Disease progression in chronic relapsing experimental allergic encephalomyelitis is associated with reduced inflammation-driven production of corticosterone

The stress-axis in multiple sclerosis: Clinical, cellular, and molecular aspects

Altered activity of the hypothalamus-pituitary-adrenal (HPA) stress-axis has been implicated in the pathogenesis and progression of multiple sclerosis (MS) and linked to the development of specific symptoms and comorbidities such as mood disorders, fatigue, or cognitive dysfunction. Overall the HPA-axis is activated or hyperresponsive in MS, though a hyporesponsive HPA-axis has been observed in a subgroup of MS patients that has a more severe course of the disease. Here we provide an overview of the possible causes of HPA-axis activation, sex- and subtype dependent differences, pathological, cellular, and molecular effects, and the clinical correlates of HPA-axis activity in MS.

Basal cortisol levels and the relationship with clinical symptoms in multiple sclerosis: a systematic review

ABSTRACT Multiple sclerosis (MS) is a demyelinating, progressive and neurodegenerative disease. A disturbance on the hypothalamic-pituitary-adrenal axis can be observed in patients with MS, showing altered cortisol levels. We aimed to identify basal cortisol levels and verify the relationship with clinical symptoms in patients with MS. A systematic search was conducted in the databases: Pubmed, Web of Science and SCOPUS. Both higher and lower cortisol levels were associated with MS. Higher cortisol levels were associated with depression and anxiety, while lower levels were associated with depression, fatigue and urinary dysfunction. Higher cortisol levels may be associated with the progression and severity of MS.

Neuroendocrine immunoregulation in multiple sclerosis

Currently, it is generally accepted that multiple sclerosis (MS) is a complex multifactorial disease involving genetic and environmental factors affecting the autoreactive immune responses that lead to damage of myelin. In this respect, intrinsic or extrinsic factors such as emotional, psychological, traumatic, or inflammatory stress as well as a variety of other lifestyle interventions can influence the neuroendocrine system. On its turn, it has been demonstrated that the neuroendocrine system has immunomodulatory potential. Moreover, the neuroendocrine and immune systems communicate bidirectionally via shared receptors and shared messenger molecules, variously called hormones, neurotransmitters, or cytokines. Discrepancies at any level can therefore lead to changes in susceptibility and to severity of several autoimmune and inflammatory diseases. Here we provide an overview of the complex system of crosstalk between the neuroendocrine and immune system as well as reported dysfunctions involved in the pathogenesis of autoimmunity, including MS. Finally, possible strategies to intervene with the neuroendocrine-immune system for MS patient management will be discussed. Ultimately, a better understanding of the interactions between the neuroendocrine system and the immune system can open up new therapeutic approaches for the treatment of MS as well as other autoimmune diseases.

End-point effector stress mediators in neuroimmune interactions: their role in immune system homeostasis and autoimmune pathology

Much evidence has identified a direct anatomical and functional link between the brain and the immune system, with glucocorticoids (GCs), catecholamines (CAs), and neuropeptide Y (NPY) as its end-point mediators. This suggests the important role of these mediators in immune system homeostasis and the pathogenesis of inflammatory autoimmune diseases. However, although it is clear that these mediators can modulate lymphocyte maturation and the activity of distinct immune cell types, their putative role in the pathogenesis of autoimmune disease is not yet completely understood. We have contributed to this field by discovering the influence of CAs and GCs on fine-tuning thymocyte negative selection and, in particular, by pointing to the putative CA-mediated mechanisms underlying this influence. Furthermore, we have shown that CAs are implicated in the regulation of regulatory T-cell development in the thymus. Moreover, our investigations related to macrophage biology emphasize the complex interaction between GCs, CAs and NPY in the modulation of macrophage functions and their putative significance for the pathogenesis of autoimmune inflammatory diseases.

Dynamic development of glucocorticoid resistance during autoimmune neuroinflammation

CONTEXT

Glucocorticoids (GC) are powerful endogenous and therapeutic modulators of inflammation and play a critical role for controlling autoimmunity. GC resistance can be seen in patients with cell-mediated autoimmune disorders, but it is unknown whether this represents a stable trait or a state.

OBJECTIVE

The objective of the study was to determine whether GC resistance of T cell responses is dynamically regulated in experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS).

DESIGN

This was a translational observational study. PATIENTS AND ANIMALS: EAE was induced in C57BL/6 mice. A cross-sectional sample of 25 patients with relapsing-remitting MS was included as well as four MS patients during pregnancy and postpartum.

MAIN OUTCOME MEASURES

Outcome measures included GC sensitivity of T cell proliferation and GC-mediated apoptosis.

RESULTS

GC resistance was seen in both autoantigen-specific and nonspecific responses of T cells obtained from mice with EAE. GC resistance preceded clinical symptoms and central nervous system infiltration of immune cells. T cells obtained during EAE were resistant to GC-induced apoptosis, and this was linked to down-regulation of GC receptor-α expression. GC resistance in T cells was also seen in MS patients with radiological evidence for ongoing inflammation. GC resistance was absent in the MS patients during pregnancy, when relapse risk is decreased, but recurred postpartum, a time of increased relapse risk.

CONCLUSIONS

These data demonstrate that GC resistance during autoimmune neuroinflammation is dynamically regulated. This has implications for the timing of steroid treatments and provides a putative pathway to explain the observed association between psychological stress and exacerbation of autoimmune diseases.

Diurnal rhythms are altered in a mouse model of multiple sclerosis

Our earlier studies described a disruption of heart rate and blood pressure diurnal rhythms in mice with experimental autoimmune encephalomyelitis (EAE). The present study investigates whether these observations could be extended to additional clock-regulated rhythms in mice with EAE. Analysis of clock gene expression in the liver of EAE mice demonstrated significant variability associated with Per2 rhythmic expression. Corticosterone and leptin hormone rhythms were also altered in EAE mice. The results presented here indicate that disturbances in clock-regulated rhythms are associated with EAE and present a suitable model for investigating the relationship between circadian disruption and autoimmune inflammatory disease.

A rapid release of corticosteroid-binding globulin from the liver restrains the glucocorticoid hormone response to acute stress

A strict control of glucocorticoid hormone responses to stress is essential for health. In blood, glucocorticoid hormones are for the largest part bound to corticosteroid-binding globulin (CBG), and just a minor fraction of hormone is free. Only free glucocorticoid hormone is able to exert biological effects, but little is known about its regulation during stress. We found, using a dual-probe in vivo microdialysis method, that in rats, the forced-swim stress-induced rise in free corticosterone (its major glucocorticoid hormone) is strikingly similar in the blood and in target compartments such as the subcutaneous tissue and the brain. However, in all compartments, the free corticosterone response was delayed by 20-30 min as compared with the total corticosterone response in the blood. We discovered that CBG is the key player in this delay. Swim stress evoked a fast (within 5 min) and profound rise in CBG protein and binding capacity in the blood through a release of the protein from the liver. Thus, the increase in circulating CBG levels after stress restrains the rise in free corticosterone concentrations for approximately 20 min in the face of mounting total hormone levels in the circulation. The stress-induced increase in CBG seems to be specific for moderate and strong stressors. Both restraint stress and forced swimming caused an increase in circulating CBG, whereas its levels were not affected by mild novelty stress. Our data uncover a new, highly dynamic role for CBG in the regulation of glucocorticoid hormone physiology after acute stress.

Epigenetic mechanisms in stress and adaptation

Epigenetic mechanisms are processes at the level of the chromatin that control the expression of genes but their role in neuro-immuno-endocrine communication is poorly understood. This review focuses on epigenetic modifications induced by a range of stressors, both physical and psychological, and examines how these variations can affect the biological activity of cells. It is clear that epigenetic modifications are critical in explaining how environmental factors, which have no effect on the DNA sequence, can have such profound, long-lasting influences on both physiology and behavior. A signaling pathway involving activation of MEK-ERK1/2, MSK1, and Elk-1 signaling molecules has been identified in the hippocampus which results in the phospho-acetylation of histone H3 and modification of gene expression including up-regulation of immediate early genes such as c-Fos. This pathway can be induced by a range of challenging experiences including forced swimming, Morris water maze learning, fear conditioning and exposure to the radial maze. Glucocorticoid (GC) hormones, released as part of the stress response and acting via glucocorticoid receptors (GRs), enhance signaling through the ERK1/2/MSK1-Elk-1 pathway and thereby increase the impact on epigenetic and gene expression mechanisms. The role of synergetic interactions between these pathways in adaptive responses to stress and learning and memory paradigms is discussed, in addition we speculate on their potential role in immune function.

Distinct, time-dependent effects of voluntary exercise on circadian and ultradian rhythms and stress responses of free corticosterone in the rat hippocampus

Previous work has shown that allowing rats to voluntarily exercise in a running wheel for 4 wk modifies the hypothalamic-pituitary-adrenal axis and behavioral coping responses to stress. To investigate whether long-term voluntary exercise would also affect the free, biologically active fraction of corticosterone in the brain, we conducted an in vivo microdialysis study in the hippocampus of rats. We monitored both the baseline circadian and ultradian patterns of corticosterone in hippocampus dialysates over the diurnal cycle and the responses to forced swim and novelty stress at different stages of exercise. Exercise for 1 d, 2 d, or 1 wk did not affect baseline circadian and ultradian pulse parameters or stress-induced hippocampal free corticosterone concentrations suggesting that acute or short-term periods of exercise do not affect baseline and stress-induced hormone levels. Baseline hormone parameters in 4 wk exercised rats, however, showed significantly increased pulse amplitudes (+108%) and mean free corticosterone levels (+42%) between 1500 and 2100 h but not between 0900 and 1500 h. Surprisingly, although our previous work showed substantial changes in stress-evoked plasma (total) corticosterone responses in long-term exercised animals, no differences in stress-induced hippocampal free hormone responses could be observed between exercised and sedentary animals. This lack of differences was not caused by compensatory changes in plasma corticosteroid-binding-globulin binding levels in exercising rats. Thus, long-term exercising rats show anticipatory increases in glucocorticoid output before the start of the active phase. These rats also reveal the putative existence of a containment mechanism preventing overexposure of the brain to glucocorticoid hormones.

Contactin-2/TAG-1-directed autoimmunity is identified in multiple sclerosis patients and mediates gray matter pathology in animals

Gray matter pathology is increasingly recognized as an important feature of multiple sclerosis (MS), but the nature of the immune response that targets the gray matter is poorly understood. Starting with a proteomics approach, we identified contactin-2/transiently expressed axonal glycoprotein 1 (TAG-1) as a candidate autoantigen recognized by both autoantibodies and T helper (Th) 1/Th17 T cells in MS patients. Contactin-2 and its rat homologue, TAG-1, are expressed by various neuronal populations and sequestered in the juxtaparanodal domain of myelinated axons both at the axonal and myelin sides. The pathogenic significance of these autoimmune responses was then explored in experimental autoimmune encephalitis models in the rat. Adoptive transfer of TAG-1-specific T cells induced encephalitis characterized by a preferential inflammation of gray matter of the spinal cord and cortex. Cotransfer of TAG-1-specific T cells with a myelin oligodendrocyte glycoprotein-specific mAb generated focal perivascular demyelinating lesions in the cortex and extensive demyelination in spinal cord gray and white matter. This study identifies contactin-2 as an autoantigen targeted by T cells and autoantibodies in MS. Our findings suggest that a contactin-2-specific T-cell response contributes to the development of gray matter pathology.

A telemetric study of physiologic changes in mice with induced autoimmune encephalomyelitis

Dysfunction of the autonomic nervous system may be an important component of disease progression in multiple sclerosis (MS), a paralytic inflammatory autoimmune disease of the central nervous system. Using the experimental autoimmune encephalomyelitis mouse model of MS, the authors carried out a pilot study to investigate whether telemetric monitoring might be a feasible approach for detecting disturbances in the autonomic control of heart rate and blood pressure after disease induction. Telemetric monitoring devices that were implanted in mice provided useful information regarding the physiologic changes that accompanied disease induction and progression. Changes were observed in heart rate, blood pressure, heart rate variability and diurnal rhythm immediately before and after disease onset. The device implantation procedure did not seem to alter the course of disease. Further investigation may establish these methods as a system for studying the relationships between MS progression and autonomic regulation of physiological status.

FTY720 sustains and restores neuronal function in the DA rat model of MOG-induced experimental autoimmune encephalomyelitis

FTY720 (fingolimod) is an oral sphingosine 1-phosphate (S1P) receptor modulator under development for the treatment of multiple sclerosis (MS). To elucidate its effects in the central nervous system (CNS), we compared functional parameters of nerve conductance in the DA rat model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) after preventive and therapeutic treatment. We demonstrate that prophylactic therapy protected against the emergence of EAE symptoms, neuropathology, and disturbances to visual and somatosensory evoked potentials (VEP, SEP). Moreover, therapeutic treatment from day 25 to 45 markedly reversed paralysis in established EAE and normalized the electrophysiological responses, correlating with decreased demyelination in the brain and spinal cord. The effectiveness of FTY720 in this model is likely due to several contributing factors. Evidence thus far supports its role in the reduction of inflammation and preservation of blood-brain-barrier integrity. FTY720 may also act via S1P receptors in glial cells to promote endogenous repair mechanisms that complement its immunomodulatory action.

Social conflict exacerbates an animal model of multiple sclerosis

A growing body of evidence suggests that social conflict is associated with inflammatory disease onset and exacerbations in multiple sclerosis (MS) patients and in animal models of MS. This review illustrates how animal research can be used to elucidate the biobehavioral mechanisms underlying the adverse health effects of social conflict. The authors review studies indicating that social conflict exacerbates a virally initiated animal model of MS. This research suggests that the deleterious effects of social conflict may be partially mediated by stress-induced increases in pro-inflammatory cytokine levels in the central nervous system. In addition, they provide evidence that the adverse health effects of social conflict can be prevented by blocking the stress-induced increases in cytokine activity. This suggests that interventions designed to prevent or reverse the stress-induced increases in cytokine activity may be able to prevent or reverse some of the negative health effects of social conflict in humans.

Stress regulation in multiple sclerosis: current issues and concepts

Since its first description by Charcot, psychological stress has been considered a triggering factor for exacerbations in multiple sclerosis, but until recently the clinical evidence for a causal relation was weak. Over the past years, a growing number of studies have started to elucidate this association and highlight potential mechanisms, including brain-immune communication. On 5 June 2005, a panel of international researchers discussed the current evidence. This article summarizes the observational, animal experimental, as well as human experimental findings on stress regulation in MS, as well as studies on the functioning of the major stress response systems, ie, the hypothalamo-pituitary-adrenal (HPA) axis and the autonomous nervous system (ANS) in MS. Consensus statements from the group to these aspects are given. Research objectives and strategies are delineated, as well as clinical implications.

Stress and disease progression in multiple sclerosis and its animal models

Since the first description of multiple sclerosis (MS) by Charcot, stress has been hypothesized to be a potential trigger of relapses. In recent years, data from observational studies in MS patients have provided some support for an association between stress and MS relapses. Furthermore, studies employing the MS animal model experimental autoimmune encephalomyelitis have shown that certain stressors can exacerbate the disease if administered prior to disease induction. Several lines of research have explored the 2 major stress response systems--the hypothalamic-pituitary-adrenal axis and the autonomic nervous system--and their relation to disease course in MS and experimental autoimmune encephalomyelitis. These studies provide evidence that insensitivity of the immune system to signals from these systems may play a role in inflammatory events. These findings can be integrated into a biological model of stress response system alterations in MS.

TCR signaling inhibits glucocorticoid-induced apoptosis in murine thymocytes depending on the stage of development

Signaling by either the TCR or glucocorticoid receptor (GR) induces apoptosis in thymocytes. Interestingly, it has been shown previously that hybridoma T cells escape apoptosis induced by either TCR or GR when both of these receptors signal simultaneously. Whether such mutual antagonism is present in primary thymocytes was the subject of the present study. Both glucocorticoids (GC) and anti-TCR/CD28 (or anti-CD3/CD28) mAb induced apoptosis in total thymocytes. When these signals were present at the same time, GC-induced apoptosis was partially inhibited by TCR/CD3 signaling. Costimulation by anti-CD28 enhanced the inhibitory effects of anti-CD3 on GC-induced apoptosis about 30-fold. However, subset analysis revealed that most cells rescued from GC-induced apoptosis were mature CD4+ and CD8+ thymocytes, and these cells were resistant to TCR/CD3-induced apoptosis in the absence of GC. Similar results were obtained with mature splenic CD4+ and CD8+ T cells. TCR/CD3 signaling alone, while inducing apoptosis in CD4+(CD8+)TCRlow thymocytes, rescued a small subset of CD4+(CD8+)TCRlow thymocytes from GC-induced apoptosis. Thus, TCR signaling increasingly reverses GC-induced apoptosis as thymocyte development progresses. As GC are infinitely present in vivo, these findings support a model wherein TCR signaling may be required to prevent GC-induced apoptosis both under basal and immune challenging conditions.

Involvement and role of the hypothalamo-pituitary-adrenal (HPA) stress axis in animal models of chronic pain and inflammation

Hypothalamo-pituitary-adrenal (HPA) axis changes have been reported in several disease states, including major depressive disorder, rheumatoid arthritis, multiple sclerosis and various other conditions associated with chronic pain. These observations suggest that stress and the HPA axis may play important roles in the pathology of these diseases. In order to contribute to a better understanding of the role that chronic stress may play in human pathology, this review article explores the involvement of the HPA axis in those animal models of chronic pain and inflammation that entail persistent rather than intermittent stress.

The hypothalamo-pituitary-adrenal axis in multiple sclerosis

During multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS), activation of the hypothalamo-pituitary-adrenal (HPA) axis is considered to modulate the immune system in such a way that the probability of recovery from a relapse is increased. In a series of postmortem studies we observed a significant activation of corticotropin releasing hormone (CRH) neurons and increased cortisol in the cerebrospinal fluid (CSF) of MS patients, indicating activation of the HPA axis in this disease. On the other hand, sepsis, while elevating cortisol in control subjects, did not associate with a further increase of cortisol in MS patients. Thus, the activated HPA-system in MS does not respond to an acute inflammatory stimulus. In order to investigate the role of chronic inflammation in the CNS in the activation of the HPA axis in MS, MS lesions in the hypothalamus were quantified and interleukin (IL)-6 levels in the CSF were determined. There was no difference in IL-6 levels between MS and control patients. A positive correlation was found between cortisol and IL-6 in control subjects with sepsis, but not in MS patients with sepsis or MS and control groups without sepsis. Thus, IL-6 in the CSF of MS patients is not the cause of the activation of the HPA system in MS. We found a remarkably high incidence (95% of the patients) of MS lesions in the hypothalamus, of which the majority (60%) were active. The more active lesions were present in the hypothalamus, the shorter the disease duration to the moment of death, indicative of a worse disease course. Preliminary data show suppression of the activation of CRH neurons by active hypothalamic MS lesions. We propose that this suppression of CRH neurons by active hypothalamic MS lesions causes the concomitant unfavorable disease course via an inadequate cortisol response during relapses of MS.

Impaired hypothalamus-pituitary-adrenal axis activity and more severe multiple sclerosis with hypothalamic lesions

In this postmortem study, we investigated the relationship between multiple sclerosis (MS) lesions in the hypothalamus and the state of activity of corticotropin-releasing hormone (CRH)-producing neurons that control the hypothalamus-pituitary-adrenal (HPA) axis. A high incidence (15/16) of MS lesions was found in the hypothalamus, of which more than 50% was active, that is, contained activated macrophages. MS patients have increased numbers of CRH-immunoreactive neurons coexpressing vasopressin (CRH/VP neurons), a sign of chronic activation of CRH neurons and increased CRH mRNA expression. Active MS lesions correlated with a low number of hyperactive CRH/VP neurons. High human leukocyte antigen (HLA)-DR, -DP, -DQ expression, a measure for macrophage and microglial activation, correlated with low CRH mRNA expression. The nearer the HLA expression was situated to the CRH neurons, the stronger the inhibiting effect, suggesting that activated microglial cells or macrophages suppress these neurons. The more active MS lesions were present in the hypothalamus, the shorter was the disease duration until the moment of death, indicating an unfavorable course of the disease. Thus, MS patients have a chronically activated CRH system, but, in the subgroup of patients with active MS lesions in the hypothalamus, this activation is impaired and the disease course is worse.