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      Endocrine-Immune Interactions in Adrenal Function of Asthmatic Children on Inhaled Corticosteroids

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          Abstract

          The present review highlights adrenal function in the context of endocrine-immune interactions and hypothalamic-pituitary-adrenal (HPA) axis activity in asthmatic children on long-term treatment with inhaled corticosteroids (ICS). Activation of the HPA axis by specific cytokines increases the release of cortisol, which in turn feeds back and suppresses the immune reaction. Reduced responsiveness of the HPA axis in patients with various chronic allergic inflammatory disorders and a blunted HPA axis response of poorly controlled asthmatics before long-term treatment with ICS have been reported. It appears that pro- and anti-inflammatory cytokines may be involved in the attenuation of cortisol and ACTH responses to stress in these patients. ICS as anti-inflammatory agents may have favorable effects in asthmatics with baseline subnormal adrenal responses, thus improving adrenal function during successful long-term treatment; on the other hand, few patients on conventional doses may experience further deterioration of adrenal function, a phenomenon that most likely is genetically determined. When ICS are administered at high doses, secondary adrenal insufficiency due to the excessive exogenous corticosteroid certainly may become manifest.

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          Most cited references60

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          How corticosteroids control inflammation: Quintiles Prize Lecture 2005.

          Corticosteroids are the most effective anti-inflammatory therapy for many chronic inflammatory diseases, such as asthma but are relatively ineffective in other diseases such as chronic obstructive pulmonary disease (COPD). Chronic inflammation is characterised by the increased expression of multiple inflammatory genes that are regulated by proinflammatory transcription factors, such as nuclear factor-kappaB and activator protein-1, that bind to and activate coactivator molecules, which then acetylate core histones to switch on gene transcription. Corticosteroids suppress the multiple inflammatory genes that are activated in chronic inflammatory diseases, such as asthma, mainly by reversing histone acetylation of activated inflammatory genes through binding of liganded glucocorticoid receptors (GR) to coactivators and recruitment of histone deacetylase-2 (HDAC2) to the activated transcription complex. At higher concentrations of corticosteroids GR homodimers also interact with DNA recognition sites to active transcription of anti-inflammatory genes and to inhibit transcription of several genes linked to corticosteroid side effects. In patients with COPD and severe asthma and in asthmatic patients who smoke HDAC2 is markedly reduced in activity and expression as a result of oxidative/nitrative stress so that inflammation becomes resistant to the anti-inflammatory actions of corticosteroids. Theophylline, by activating HDAC, may reverse this corticosteroid resistance. This research may lead to the development of novel anti-inflammatory approaches to manage severe inflammatory diseases.
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            Enhancing versus Suppressive Effects of Stress on Immune Function: Implications for Immunoprotection and Immunopathology

            Stress is known to suppress immune function and increase susceptibility to infections and cancer. Paradoxically, stress is also known to exacerbate asthma, and allergic, autoimmune and inflammatory diseases, although such diseases should be ameliorated by immunosuppression. Moreover, the short-term fight-or-flight stress response is one of nature’s fundamental defense mechanisms that enables the cardiovascular and musculoskeletal systems to promote survival, and it is unlikely that this response would suppress immune function at a time when it is most required for survival (e.g. in response to wounding and infection by a predator or aggressor). These observations suggest that stress may suppress immune function under some conditions while enhancing it under others. The effects of stress are likely to be beneficial or harmful depending on the type (immunoprotective, immunoregulatory/inhibitory, or immunopathological) of immune response that is affected. Studies have shown that several critical factors influence the direction (enhancing vs. suppressive) of the effects of stress or stress hormones on immune function: (1) Duration (acute vs. chronic) of stress: Acute or short-term stress experienced at the time of immune activation can enhance innate and adaptive immune responses. Chronic or long-term stress can suppress immunity by decreasing immune cell numbers and function and/or increasing active immunosuppressive mechanisms (e.g. regulatory T cells). Chronic stress can also dysregulate immune function by promoting proinflammatory and type-2 cytokine-driven responses. (2) Effects of stress on leukocyte distribution: Compartments that are enriched with immune cells during acute stress show immunoenhancement, while those that are depleted of leukocytes, show immunosuppression. (3) The differential effects of physiologic versus pharmacologic concentrations of glucocorticoids, and the differential effects of endogenous versus synthetic glucocorticoids: Endogenous hormones in physiological concentrations can have immunoenhancing effects. Endogenous hormones at pharmacologic concentrations, and synthetic hormones, are immunosuppressive. (4) The timing of stressor or stress hormone exposure relative to the time of activation and time course of the immune response: Immunoenhancement is observed when acute stress is experienced at early stages of immune activation, while immunosuppression may be observed at late stages of the immune response. We propose that it is important to study and, if possible, to clinically harness the immunoenhancing effects of the acute stress response, that evolution has finely sculpted as a survival mechanism, just as we study its maladaptive ramifications (chronic stress) that evolution has yet to resolve. In view of the ubiquitous nature of stress and its significant effects on immunoprotection as well as immunopathology, it is important to further elucidate the mechanisms mediating stress-immune interactions and to meaningfully translate findings from bench to bedside.
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              A novel polymorphism in the toll-like receptor 2 gene and its potential association with staphylococcal infection.

              The toll-like receptor 2 (TLR2) has gained importance as a major mammalian receptor for lipoproteins derived from the cell wall of a variety of bacteria, such as Borrelia burgdorferi, Treponema pallidum, and Mycoplasma fermentans. We were interested in identifying mutations in the TLR2 gene that might prove to be associated with altered susceptibility to septic shock. We performed a mutation screen of the TLR2 gene using single-stranded conformational polymorphism in 110 normal, healthy study subjects and detected an Arg753Gln mutation in three individuals. No other missense mutations were detected in the TLR2 open reading frame. Functional studies demonstrate that the Arg753Gln polymorphism, in comparison to the wild-type TLR2 gene, is significantly less responsive to bacterial peptides derived from B. burgdorferi and T. pallidum. In a septic shock population, the Arg753Gln TLR2 polymorphism occurred in 2 out of 91 septic patients. More importantly, both of the subjects with the TLR2 Arg753Gln polymorphism had staphylococcal infections. These findings suggest that a mutation in the TLR2 gene may predispose individuals to life-threatening bacterial infections.
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                Author and article information

                Journal
                NIM
                Neuroimmunomodulation
                10.1159/issn.1021-7401
                Neuroimmunomodulation
                S. Karger AG
                978-3-8055-9200-0
                978-3-8055-9201-7
                1021-7401
                1423-0216
                2009
                June 2009
                29 June 2009
                : 16
                : 5
                : 333-339
                Affiliations
                aDepartment of Allergy-Pneumonology, Penteli Children’s Hospital, Palea Penteli, bThird Department of Pediatrics, Attikon University Hospital, Athens University Medical School, cFirst Department of Pediatrics, Aghia Sophia Children’s Hospital, Athens University Medical School, Athens, and dRespiratory Unit, Department of Pediatrics, University Hospital of Patras, Rio, Greece
                Article
                216191 Neuroimmunomodulation 2009;16:333–339
                10.1159/000216191
                19571594
                ecde53ef-4864-441d-867d-e224c93546af
                © 2009 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                History
                Page count
                Figures: 1, References: 75, Pages: 7
                Categories
                Paper

                Endocrinology & Diabetes,Neurology,Nutrition & Dietetics,Sexual medicine,Internal medicine,Pharmacology & Pharmaceutical medicine
                Hypothalamic-pituitary-adrenal axis,Asthma,Stress,Airway inflammation,Inhaled corticosteroids

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