Hypothalamic noradrenergic pathways exert an influence on neuroendocrine and clinical status in experimental autoimmune encephalomyelitis

Autoimmune demyelination alters hypothalamic transcriptome and endocrine function

The hypothalamus is a brain structure that is deputed to maintain organism homeostasis by regulating autonomic function and hormonal production as part of the neuroendocrine system. Dysfunction in hypothalamic activity results in behavioral alterations, depression, metabolic syndromes, fatigue, and infertility. Remarkably, many of these symptoms are associated with multiple sclerosis (MS), a chronic autoimmune disorder of the central nervous system (CNS) characterized by focal demyelination, immune cell infiltration into the brain parenchyma, and neurodegeneration. Furthermore, altered hormonal levels have been documented in MS patients, suggesting the putative involvement of hypothalamic deficits in MS clinical manifestations. Yet, a systematic analysis of hypothalamic function in response to neuroinflammatory stress is still lacking. To fill this gap, here we performed a longitudinal profiling of the hypothalamic transcriptome upon experimental autoimmune encephalomyelitis (EAE)-a murine disease model recapitulating key MS phenotypes at both histopathological and molecular levels. We show that changes in gene expression connected with an anti-inflammatory response start already at pre-onset and persist along EAE progression. Altered levels of hypothalamic neuropeptides were also detected, which possibly underlie homeostatic responses to stress and aberrant feeding behaviors. Last, a thorough investigation of the principal endocrine glands highlighted defects in the main steroidogenic pathways upon disease. Collectively, our findings corroborate the central role of hypothalamic dysfunction in CNS autoimmunity.

Hormones in experimental autoimmune encephalomyelitis (EAE) animal models

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) in which activated immune cells attack the CNS and cause inflammation and demyelination. While the etiology of MS is still largely unknown, the interaction between hormones and the immune system plays a role in disease progression, but the mechanisms by which this occurs are incompletely understood. Several in vitro and in vivo experimental, but also clinical studies, have addressed the possible role of the endocrine system in susceptibility and severity of autoimmune diseases. Although there are several demyelinating models, experimental autoimmune encephalomyelitis (EAE) is the oldest and most commonly used model for MS in laboratory animals which enables researchers to translate their findings from EAE into human. Evidences imply that there is great heterogeneity in the susceptibility to the induction, the method of induction, and the response to various immunological or pharmacological interventions, which led to conflicting results on the role of specific hormones in the EAE model. In this review, we address the role of endocrine system in EAE model to provide a comprehensive view and a better understanding of the interactions between the endocrine and the immune systems in various models of EAE, to open up a ground for further detailed studies in this field by considering and comparing the results and models used in previous studies.

Neuroimmune interactions: dendritic cell modulation by the sympathetic nervous system

Dendritic cells are of paramount importance bridging innate and adaptive immune responses. Depending on the context, after sensing environmental antigens, commensal microorganisms, pathogenic agents, or antigens from the diet, dendritic cells may drive either different effector adaptive immune responses or tolerance, avoiding tissue damage. Although the plasticity of the immune response and the capacity to regulate itself are considered essential to orchestrate appropriate physiological responses, it is known that the nervous system plays a relevant role controlling immune cell function. Dendritic cells present in the skin, the intestine, and lymphoid organs, besides expressing adrenergic receptors, can be reached by neurotransmitters released by sympathetic fibers innervating these tissues. These review focus on how neurotransmitters from the sympathetic nervous system can modulate dendritic cell function and how this may impact the immune response and immune-mediated disorders.

Causes, consequences, and cures for neuroinflammation mediated via the locus coeruleus: noradrenergic signaling system

Aside from its roles in as a classical neurotransmitter involved in regulation of behavior, noradrenaline (NA) has other functions in the CNS. This includes restricting the development of neuroinflammatory activation, providing neurotrophic support to neurons, and providing neuroprotection against oxidative stress. In recent years, it has become evident that disruption of physiological NA levels or signaling is a contributing factor to a variety of neurological diseases and conditions including Alzheimer's disease (AD) and Multiple Sclerosis. The basis for dysregulation in these diseases is, in many cases, due to damage occurring to noradrenergic neurons present in the locus coeruleus (LC), the major source of NA in the CNS. LC damage is present in AD, multiple sclerosis, and a large number of other diseases and conditions. Studies using animal models have shown that experimentally induced lesion of LC neurons exacerbates neuropathology while treatments to compensate for NA depletion, or to reduce LC neuronal damage, provide benefit. In this review, we will summarize the anti-inflammatory and neuroprotective actions of NA, summarize examples of how LC damage worsens disease, and discuss several approaches taken to treat or prevent reductions in NA levels and LC neuronal damage. Further understanding of these events will be of value for the development of treatments for AD, multiple sclerosis, and other diseases and conditions having a neuroinflammatory component. The classical neurotransmitter noradrenaline (NA) has critical roles in modulating behaviors including those involved in sleep, anxiety, and depression. However, NA can also elicit anti-inflammatory responses in glial cells, can increase neuronal viability by inducing neurotrophic factor expression, and can reduce neuronal damage due to oxidative stress by scavenging free radicals. NA is primarily produced by tyrosine hydroxylase (TH) expressing neurons in the locus coeruleus (LC), a relatively small brainstem nucleus near the IVth ventricle which sends projections throughout the brain and spinal cord. It has been known for close to 50 years that LC neurons are lost during normal aging, and that loss is exacerbated in neurological diseases including Parkinson's disease and Alzheimer's disease. LC neuronal damage and glial activation has now been documented in a variety of other neurological conditions and diseases, however, the causes of LC damage and cell loss remain largely unknown. A number of approaches have been developed to address the loss of NA and increased inflammation associated with LC damage, and several methods are being explored to directly minimize the extent of LC neuronal cell loss or function. In this review, we will summarize some of the consequences of LC loss, consider several factors that likely contribute to that loss, and discuss various ways that have been used to increase NA or to reduce LC damage. This article is part of the 60th Anniversary special issue.

Mimicking disruption of brain-immune system-joint communication results in collagen type II-induced arthritis in non-susceptible PVG rats

The brain-immune system-joint communication is disrupted during collagen type II (CII) arthritis in DA rats. Since PVG rats are not susceptible to arthritis induction, comparison of hypothalamic and peripheral neuro-endocrine and immune responses between immunized DA and PVG rats might help to explain their different susceptibility to develop the disease. PVG and DA rats were immunized with CII. Corticosterone, neurotransmitters, anti-CII antibodies, and cytokine concentrations in plasma, and hypothalamic neurotransmitters and cytokines were determined by ELISA, Luminex, HPLC and RT-qPCR. Adrenalectomy or sham-operation was performed in PVG and DA rats 14 days before immunization. Basal plasma corticosterone and adrenaline concentrations were significantly higher, and plasma cytokines and hypothalamic noradrenaline were lower in PVG rats than in DA rats. While DA rats developed severe arthritis upon immunization (maximum score 16), only 12 out of 28 PVG rats showed minimal symptoms (score 1-2). The density of sympathetic nerve fibers in arthritic joints of DA rats markedly decreased, but it remained stable in immunized PVG rats. The ratio corticosterone to IL-1β levels in plasma was markedly higher in immunized PVG rats than in arthritic DA rats. Adrenalectomy resulted in severe arthritis in PVG rats upon immunization with CII. While DA rats show an altered immune-brain communication that favors the development of arthritis, PVG rats express a protective neuro-endocrine milieu, particularly linked to the basal tone of the HPA axis. Mimicking disruption of this axis elicits arthritis in non-susceptible PVG rats.

Noradrenergic regulation of glial activation: molecular mechanisms and therapeutic implications

It has been known for many years that the endogenous neurotransmitter noradrenaline (NA) exerts anti-inflammatory and neuroprotective effects both in vitro and in vivo. In many cases the site of action of NA are beta-adrenergic receptors (βARs), causing an increase in intracellular levels of cAMP which initiates a broad cascade of events including suppression of inflammatory transcription factor activities, alterations in nuclear localization of proteins, and induction of patterns of gene expression mediated through activity of the CREB transcription factor. These changes lead not only to reduced inflammatory events, but also contribute to neuroprotective actions of NA by increasing expression of neurotrophic substances including BDNF, GDNF, and NGF. These properties have prompted studies to determine if treatments with drugs to raise CNS NA levels could provide benefit in various neurological conditions and diseases having an inflammatory component. Moreover, increasing evidence shows that disruptions in endogenous NA levels occurs in several diseases and conditions including Alzheimer's disease (AD), Parkinson's disease (PD), Down's syndrome, posttraumatic stress disorder (PTSD), and multiple sclerosis (MS), suggesting that damage to NA producing neurons is a common factor that contributes to the initiation or progression of neuropathology. Methods to increase NA levels, or to reduce damage to noradrenergic neurons, therefore represent potential preventative as well as therapeutic approaches to disease.

Altered cognitive-emotional behavior in early experimental autoimmune encephalitis--cytokine and hormonal correlates

Multiple sclerosis (MS) is often associated with co-morbid behavioural and cognitive impairments; however the presence of these symptoms does not necessarily correlate with neurological damage. This suggests that an alternate mechanism may subserve these impairments relative to motor deficits. We investigated whether these abnormalities could be studied in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. In myelin oligodendrocyte glycoprotein peptide (MOG35-55)-induced EAE mice, no motor deficits were observed until d9 after immunization. This enabled us to carry out a series of neurobehavioral tests during the presymptomatic stage, between d6 and d8 post-immunization. EAE mice spent more time in the outer zone in an open field test and in the closed arms of an elevated plus maze and, showed decreased latency for immobility in the tail suspension and forced swim tests and reduced social interaction compared with controls. These results are indicative of anxiety- and depression- like behavior. In addition, EAE mice appeared to exhibit memory impairment compared to controls based on their reduced time spent in the target quadrant in the Morris water maze and their faster memory extinction in the fear conditioning test. No demyelination, microglial activation or astrogliosis was observed in the brain at this early stage. Transcript analysis by RT-PCR from d6 to d8 brain revealed elevated interleukin (IL)-1β and TNF-α in the hypothalamus but not in the amygdala or hippocampus of EAE mice. Lastly, plasma corticosterone levels increased in EAE mice compared to controls. In conclusion, emotional and cognitive deficits are observed in EAE prior to demyelination and are associated with elevated IL-1β and TNF-α in the hypothalamus and changes in the hypothalamic-pituitary-adrenal axis.

Increasing CNS noradrenaline reduces EAE severity

The endogenous neurotransmitter noradrenaline (NA) is known to exert potent anti-inflammatory effects in glial cells, as well as provide neuroprotection against excitatory and inflammatory stimuli. These properties raise the possibility that increasing levels of NA in the central nervous system (CNS) could provide benefit in neurological diseases and conditions containing an inflammatory component. In the current study, we tested this possibility by examining the consequences of selectively modulating CNS NA levels on the development of clinical signs in experimental autoimmune encephalomyelitis (EAE). In mice immunized with myelin oligodendrocyte glycoprotein peptide to develop a chronic disease, pretreatment to selectively deplete CNS NA levels exacerbated clinical scores. Elevation of NA levels using the selective NA reuptake inhibitor atomoxetine did not affect clinical scores, while treatment of immunized mice with the synthetic NA precursor L-threo-3,4-dihydroxyphenylserine (L-DOPS) prevented further worsening. In contrast, treatment of mice with a combination of atomoxetine and L-DOPS led to significant improvement in clinical scores as compared to the control group. The combined treatment reduced astrocyte activation in the molecular layer of the cerebellum as assessed by staining for glial fibrillary protein but did not affect Th1 or Th17 type cytokine production from splenic T cells. These data suggest that selective elevation of CNS NA levels could provide benefit in EAE and multiple sclerosis without influencing peripheral immune responses.

Sympathetic modulation of immunity: relevance to disease

Optimal host defense against pathogens requires cross-talk between the nervous and immune systems. This paper reviews sympathetic-immune interaction, one major communication pathway, and its importance for health and disease. Sympathetic innervation of primary and secondary immune organs is described, as well as evidence for neurotransmission with cells of the immune system as targets. Most research thus far has focused on neural-immune modulation in secondary lymphoid organs, has revealed complex sympathetic modulation resulting in both potentiation and inhibition of immune functions. SNS-immune interaction may enhance immune readiness during disease- or injury-induced 'fight' responses. Research also indicate that dysregulation of the SNS can significantly affect the progression of immune-mediated diseases. However, a better understanding of neural-immune interactions is needed to develop strategies for treatment of immune-mediated diseases that are designed to return homeostasis and restore normal functioning neural-immune networks.

Beta-adrenoceptor blockade ameliorates the clinical course of experimental allergic encephalomyelitis and diminishes its aggravation in adrenalectomized rats

As glucocorticoids influence both catecholamine synthesis and adrenoceptor expression by immune cells, the current study was undertaken to distinguish their direct effects on the development of experimental allergic encephalomyelitis from those induced by alteration of catecholamine signaling. We examined the influence of 16-day-long beta-adrenoceptor blockade with propranolol (0.40 mg/100 g body weight/day, s.c.) beginning 3 days before immunization on the development of experimental allergic encephalomyelitis in adrenalectomized (7 days before immunization) and in non-operated male Dark Agouti rats. Adrenalectomy aggravated the clinical course of experimental allergic encephalomyelitis. In contrast, propranolol attenuated both the clinical signs of the disease and decreased the number of lesions in the spinal cord. Furthermore, propranolol prevented adrenalectomy-induced aggravation of the disease course without affecting mortality. We also found that the percentage of CD4(+)CD25(+) T lymphocytes (recently activated or regulatory cells) was increased in peripheral blood of experimental allergic encephalomyelitis rats over that in the corresponding non-immunized and bovine serum albumin immunized rats. However, the percentage of these cells was reduced in adrenalectomized and/or propranolol-treated experimental allergic encephalomyelitis rats compared to control experimental allergic encephalomyelitis rats. Our findings, coupled with the clinical course of the disease and the underlying pathomorphological changes, clearly suggest that differential mechanisms were responsible for the changes in the percentage of CD4(+)CD25(+) T lymphocytes in propranolol-treated adrenalectomized rats and only propranolol-treated rats with experimental allergic encephalomyelitis. Our results, when viewed globally, indicate that: i) beta-adrenoceptor-dependent mechanisms are involved in the immunopathogenesis of experimental allergic encephalomyelitis, ii) experimental allergic encephalomyelitis has a more severe course in adrenalectomized rats and iii) beta-adrenoceptor-mediated mechanisms operate in adrenalectomy-induced aggravation of the disease.

Amygdaloid kindled seizures can induce functional and pathological changes in thymus of rat: role of the sympathetic nervous system

The present study sought to determine the effects of long-term kindled seizures of the basal amygdala upon immune function in rat, utilizing the thymus, as a principal target for study. Histopathology from kindled Sprague-Dawley rats revealed the presence of epithelial cell thymoma in 70% of these rats. The results revealed an increased rate of apoptosis and proliferation in thymic epithelial cells. Analysis of thymocytes indicated a decrease in the ratio of CD4 to CD8 positive T cells and reduced proliferative response to T-cell mitogens. To determine whether these effects were mediated through the sympathetic nervous system, animals were treated with guanethidine, which blocked the development of epithelial cell thymomas, while mifepristone treatment, employed to determine the possible role of the hypothalamic-pituitary axis, was ineffective in attenuating thymoma development. Thus, the present study demonstrated that functional and pathological changes in the thymus during kindled seizures are mediated through the sympathetic nervous system.

Severe T-cell depletion from the PALS leads to altered spleen composition in common marmosets with experimental autoimmune encephalomyelitis (EAE)

Recent data suggest that the spleen is a crucial component of the immune system in the development of experimental autoimmune encephalomyelitis (EAE) in marmoset monkeys. Using immunohistochemistry, we investigated changes in the distribution of leukocytes in the spleen associated with clinical symptoms of EAE. Animals without EAE displayed well-developed T- and B-cell areas, germinal centers and red pulp. In contrast, a marked depletion of periarteriolar T cells with preservation of other elements was found in animals with clinical EAE. These findings suggest that immune responses within the spleen are impaired during a paralysing inflammatory process in the central nervous system.

Environmental Influences in Experimental Autoimmune Encephalomyelitis

Environmental factors, in particular infectious agents, are thought to have a major influence on the development and course of MS. Some of these influences are also reflected in the animal model, EAE. In this chapter, the role of infectious agents in the development and course of autoimmunity in EAE is discussed. Other environmental agents including trauma, solar radiation exposure, temperature, stress, toxins, are discussed in terms of their relevance to MS and EAE.

In vitro adrenergic modulation of cellular immune functions in experimental autoimmune encephalomyelitis

OBJECTIVE

To analyze the effects in vitro of alpha- and beta-adrenoceptor agonists on splenocyte proliferation and on proinflammatory cytokine production in splenocytes and peritoneal macrophages (MF) in different stages of EAE.

METHODS

Splenocytes and peritoneal macrophages were harvested in the acute phase of EAE and in remission, and from controls. The beta-agonist terbutaline, the alpha(1)-agonist methoxamine, and the alpha(2)-agonist UK-14304 were added with ConA or lipopolysaccharide (LPS). TNF-alpha and IFN-gamma contents in supernatant and splenocyte proliferation were determined.

RESULTS

Terbutaline and UK-14304 significantly suppressed TNF-alpha production by MF. However, EAE acute phase rats were resistant to the suppressive effect of UK-14304. Terbutaline significantly suppressed IFN-gamma and TNF-alpha production by splenocytes. EAE acute phase and remission animals showed reduced terbutaline-induced inhibition of IFN-gamma production.

CONCLUSIONS

Disturbed sympathetic-immune communication in EAE is characterized by alterations in adrenergic sensitivity via both alpha- and beta-adrenergic pathways.

Neuroendocrinology of autoimmunity

The HPA axis is fundamental for long-term survival and protection from the ravages of autoimmune disease. Continuing investigations suggest that the hypothesis linking susceptibility to autoimmune disease and a hyporesponsive HPA axis is somewhat simplistic. Instead, data from a number of different human diseases and from preclinical studies in a variety of models have suggested a more complicated picture. Alterations in the diurnal rhythms of ACTH, cortisol, and immune parameters appear to be linked to severity of disease. The use of low doses of steroids timed to target disrupted diurnal immune system changes in patients with RA may reduce the unfortunate side effects of long-term steroid use. Studies in cancer patients have related alterations in diurnal cortisol to survival. Whether differences in individual cortisol profiles are predictive of a deterioration in symptoms of autoimmune disease remains to be established. Responsiveness of the HPA axis to subtle challenges such as the dexamethasone suppression test and the related dexamethasone-CRF test suggest that there are different sub-populations of patients with RA and MS and these may have confounded earlier, apparently contradictory, studies. These different responses may be related to the severity of the disease. That these HPA axis differences can be altered beneficially through the use of antidepressants, as has been shown in MS, may impact on future health care strategies. However, reports of negative developments in arthritis associated with SSRI use suggest that the SSRIs may be unsuitable under some circumstances. The link of behavioral differences to alterations in neurotransmitter changes associated with disease is intriguing and opens new avenues of research. These future studies will require input from neuroscientists, neuroendocrinologists, psychologists, and immunologists working with the clinical specialties already involved in treating patients with autoimmune disease. These multidisciplinary studies reflecting the increased importance of hormonal and neurotransmitter involvement with the immune system hold great promise for the future.

Cognitive impairment correlates with hypothalamo-pituitary-adrenal axis dysregulation in multiple sclerosis

Hypothalamo-pituitary-adrenal (HPA) dysregulation has recently been demonstrated in multiple sclerosis (MS) by means of combined dexamethasone corticotropin-releasing hormone (Dex-CRH) suppression tests. Authors found a correlation with course of disease and to a lesser extent with depressive symptoms. In this study, we aimed to further evaluate whether HPA disturbances in MS are correlated with cognitive impairment, disability status, and fatigue. Dex-CRH tests were performed in a total of 40 patients and 11 healthy controls. Concomitantly, cognitive impairment was evaluated using the symbol digit modalities test and fatigue was assessed by different fatigue severity scales. When comparing patient subpopulations to healthy subjects, Dex-CRH stimulation tests indicated an HPA hyperactivity in primary and secondary progressive MS, while relapsing-remitting patients had response patterns similar to controls. However, results were only significant for one of the six analysed parameters, i.e. area under the curve calculations of ACTH stimulation. Within the patient sample, clear-cut differences emerged between groups of different cognitive impairment, being significant for all ACTH response parameters. Our results suggest an HPA hyperactivation related to increased cognitive impairment. Indicators of HPA axis activation further correlated substantially with neurologic disability, but only moderately with duration of disease and even less with depressive symptoms and fatigue. We conclude that the observed dysregulation is more likely a secondary effect of the extent of brain damage rather than primarily involved in the pathogenesis of MS.

Neonatal glucocorticoids and the developing brain: short-term treatment with life-long consequences?

Although synthetic glucocorticoids are frequently used in hospital for the prevention of chronic lung disease in premature infants, major concern has arisen about the possible long-term consequences of these treatments. Animal research provides evidence for the idea that neonatal glucocorticoid treatment enhances susceptibility to autoimmune disease in adult life. Altered functioning of the hypothalamo-pituitary-adrenal axis, and/or changes at higher brain levels might underlie alterations in disease susceptibility.

Autonomic regulation of experimental autoimmune encephalomyelitis in IL-4 knockout mice

The effect of chemical sympathectomy induced with 6-hydroxydopamine (OHDA) on experimental autoimmune encephalomyelitis (EAE) was studied in wild type and IL-4-/- C57BL/6 (B6) mice. When actively sensitized with myelin oligodendrocyte glycoprotein (MOG)35-55 peptide, control B6 mice developed a mild form of EAE with full recovery. The sympathectomized mice developed paralysis with higher maximum disease score and did not recover completely, indicating that the sympathetic nervous system (SNS) down-modulates the process of EAE. Unexpectedly, however, sympathectomy resulted in suppression of EAE in IL-4-/- mice, implying that control of actively induced EAE by the SNS depends on the genetic background of mice. We also induced EAE by passive transfer of MOG35-55-reactive lymph node cells, and this disease was augmented by sympathectomy in both wild type and knockout animals. Further experiments showed that changes in T cell populations and the activity of antigen presenting cells might be responsible for the altered immune response and clinical course after sympathetic ablation. Our studies indicate that the absence of a single cytokine can severely alter nervous-immune system interactions.

The hypothalamic-pituitary-adrenal axis in autoimmunity

We have characterized the activation of the HPA axis in the chronic inflammatory stress model of adjuvant-induced arthritis. Alteration in the hypothalamic control mechanism, where CRF is no longer the major corticotrophin-releasing factor, has been noted in a number of other immune-mediated disease models, including experimental allergic encephalomyelitis, eosinophilia myalgia syndrome, systemic lupus erythematosus, and leishmaniasis. These changes occur in both the mouse and the rat, suggesting this may be a common mechanism to chronic immune activation. We have good evidence to suggest that AVP takes over as the major stimulator of the axis. The arthritic rat is unable to mount a response to acute stressors, such as restraint or ip hypertonic saline. However, these animals are able to mount a response to an acute immune challenge. These data provide further evidence for a differential activation of the HPA by acute stress or acute immune stimulation. This presumably reflects an adaptive response to the development of chronic inflammation. We have demonstrated that central neurotransmitter systems are able to influence the severity of peripheral inflammation. In particular we have shown that depletion of serotonin at the time of the development of the inflammatory episode reduces the severity of the inflammation. These findings suggest the possibility of novel therapeutic strategies targeting neurotransmitter systems to alleviate inflammation.

Neuroendocrine changes in systemic lupus erythematosus and Sjögren's syndrome

It has become clear that the neuroendocrine and immune systems are closely linked and interdependent. The exact mechanisms of this interaction are only beginning to be unravelled. The complexity of these connections may partly explain why the aetiopathogenesis of autoimmune diseases remains obscure and why genetic, hormonal, microbial, environmental, as well as a host of other factors, have all been put forward as explanations. What has become clear is that a number of neuroendocrine and hormonal factors have important immunomodulatory roles in health and disease.

Activation and proliferation of murine microglia are insensitive to glucocorticoids in Wallerian degeneration

Activation and proliferation of microglia are commonly described in the central nervous system after a wide range of insults, but the mechanisms that regulate their phenotype in vivo are still poorly understood. We have studied the effect that adrenalectomy and dexamethasone treatment have on the proliferation and activation of microglia during Wallerian degeneration of the optic nerve in BALB/c mice. We found that the onset and rate of microglia proliferation is independent of glucocorticoids. There was an increase in F4/80-positive cells 3 days after optic nerve crush, with a peak at 7 days, both in the optic nerve and its target, the superior colliculus. The numbers of F4/80-positive cells remained high up to 3 weeks after crush, the longest time point examined. We also found that up-regulation of F4/80 and the complement receptor type 3 and expression of major histocompatibility complex class II antigens were not affected by adrenalectomy or dexamethasone treatment. These observations show that, unlike microglia in vitro or peripheral macrophages, microglia do not readily respond to glucocorticoids, which could indicate a lack of or reduced expression of glucocorticoid receptor in these cells.

Recent advances in the pharmacological control of experimental allergic encephalomyelitis (EAE) and the implications for multiple sclerosis treatment

The autoimmune, cell-mediated condition experimental allergic encephalomyelitis (EAE) is the representative model for the inflammatory central nervous system disease MS. EAE has been extensively employed to determine the efficacy of pharmacological agents that may be of ultimate use in the treatment of MS. A wide variety of drugs has been examined for activity in EAE but, over the last decade, three groups of compounds have emerged with clear and reproducible ability to modify significantly the onset and progression of the disease. The immunosuppressants, the modulators of catecholamine activity and the antineoplastic agents have convincingly altered the course of EAE and, as a consequence, provided understanding of the mechanisms of disease expression and offered further insight into the pathogenesis of MS. The article stresses the usefulness of EAE as a model to identify prospective pharmacological treatments for MS and, in particular, considers those compounds subsequently assessed for their ability to interfere with the progression of the human disease.

Suppression of experimental allergic encephalomyelitis in the Lewis rat by the matrix metalloproteinase inhibitor Ro31-9790

Matrix metalloproteinases (MMPs) are implicated in the tissue destruction associated with inflammatory demyelinating diseases such as multiple sclerosis. The effect of a hydroxamate inhibitor of MMPs, Ro31-9790, on inflammatory demyelination was assessed in two acute models of experimental allergic encephalomyelitis (EAE). Daily intraperitoneal injections of Ro31-9790 (50 mg kg-1), beginning either at the time of disease induction or from day 3 post induction, significantly reduced the clinical severity of adoptively transferred EAE. Administration of the inhibitor from the day of induction of active EAE prevented disease onset in 9/10 animals. However, in a repeat study, in which clinical disease was much more severe in the vesicle treated animals, the inhibitor was less effective. Clinical signs and CNS histopathology correlated well, with greater numbers of inflammatory lesions associated with increased disease severity. The present study confirms a role for then MMP cascade in inflammation in EAE.

Experimental allergic encephalomyelitis in adult DA rats subjected to neonatal handling or gentling

The present study investigated the effect of daily handling and gentling between postnatal days 1 and 28 on experimental allergic encephalomyelitis (EAE) in 8-week old DA rats. Handling consisted of removing pups from the mother, and placing them in the novel cage for 15 min. The gentling procedure included handling accompanied by 3 min of dorsal tactile stimulation before returning the pups to the nest cage. Adult rats of both sexes handled in infancy showed increased susceptibility to EAE, as revealed by higher incidence of the disease, and more severe clinical signs. Anti-myelin basic protein (MBP) autoantibodies were increased in handled males, and decreased in handled females, compared to controls. Gentling induced aggravation of clinical signs and histopathological lesions of EAE in males, while in gentled females suppression was observed. These results indicated that both neonatal handling and gentling aggravated EAE induced in adult male rats. In female rats handling exacerbated, and gentling suppressed clinical EAE. The overall effect of neonatal manipulations was more pronounced in males. Furthermore, in mothers separated from their offspring due to handling and gentling, and immunized for EAE at day 28 postpartum, earlier appearance of clinical signs, and increased frequency of relapses compared to control dams was recorded.

Neuroendocrine-immune interactions in homeostasis and autoimmunity

Recent experimental evidence confirms the interrelationships between the central nervous, neuroendocrine and immune systems. Indeed, extensive duality exists in the use of neurotransmitters, hormones and receptors each system displays. In the present annotation, the effect of cytokines, soluble mediators of immune function, on the CNS and neuroendocrine systems is addressed and conversely, we discuss the modification of the immune compartment by the sympathetic nervous and neuroendocrine systems, with particular reference to the role of noradrenaline and corticosterone. Dysfunction between the systems is considered in the context of autoimmune conditions, with emphasis on experimental allergic encephalomyelitis and the contribution of corticosterone-driven T-cell apoptosis to recovery from the disease. Finally, we speculate on the relevance of neuroimmune interactions in the pathogenesis of multiple sclerosis.

Salivary cortisol in psychoneuroendocrine research: recent developments and applications

The assessment of cortisol in saliva has proven a valid and reliable reflection of the respective unbound hormone in blood. To date, assessment of cortisol in saliva is a widely accepted and frequently employed method in psychoneuroendocrinology. Due to several advantages over blood cortisol analyses (e.g., stress-free sampling, laboratory independence, lower costs) saliva cortisol assessment can be the method of choice in basic research and clinical environments. The determination of cortisol in saliva can facilitate stress studies including newborns and infants and replace blood sampling for diagnostic endocrine tests like the dexamethasone suppression test. The present paper provides an up-to-date overview of recent methodological developments, novel applications as well as a discussion of possible future applications of salivary cortisol determination.

Modulation of interferon-gamma-induced major histocompatibility complex class II and Fc receptor expression on isolated microglia by transforming growth factor-beta 1, interleukin-4, noradrenaline and glucocorticoids

Interleukin-4 (IL-4) enhances Fc receptor (FcR) expression on isolated rat brain microglia and peritoneal macrophages but has little effect on major histocompatibility complex (MHC) class II antigen expression. In contrast transforming growth factor-beta 1 (TGF-beta 1) causes a reduction in expression of MHC class II on macrophages and of FcR on both cell types. Both microglia and peritoneal macrophages demonstrate enhanced expression of FcR and MHC class II on treatment with interferon-gamma (IFN-gamma). The effect of IL-4 or TGF-beta 1 in combination with IFN-gamma, added either sequentially or simultaneously, has been investigated. TGF-beta 1 down-regulates IFN-gamma-induced effects in both microglia and macrophages when present before or during the activation stage. In combination, IL-4 and IFN-gamma can be additive or antagonistic, depending on their concentrations and the sequence in which cells are exposed to the cytokines. Non-cytokine mediators present during stimulation, such as noradrenaline, dexamethasone and corticosterone, are also potent inhibitors of IFN-gamma-induced activation of microglia and macrophages.

Changes in hypothalamic corticotrophin-releasing factor and anterior pituitary pro-opiomelanocortin mRNA during the course of experimental allergic encephalomyelitis

The pituitary-adrenal axis is activated during the course of experimental allergic encephalomyelitis (EAE), a paralytic disease resulting from an immunological reaction against central nervous system myelin. The magnitude of the adrenal response not only correlates with the severity of disease, but also serves an important functional role in recovery. We have shown that in EAE there are short-term changes in anterior pituitary pro-opiomelanocortin (POMC) mRNA as well as plasma corticosterone which can be detected before the development of clinical disease. At peak clinical signs when corticosterone and POMC mRNA are maximal, hypothalamic corticotrophin-releasing factor (CRF) mRNA is suppressed, suggesting that pituitary-adrenal activation is not mediated by CRF. Following recovery all parameters return to normal.