Androgens are protective in experimental autoimmune encephalomyelitis: implications for multiple sclerosis

XX sex chromosome complement modulates immune responses to heat-killed Streptococcus pneumoniae immunization in a microbiome-dependent manner

BACKGROUND

Differences in male vs. female immune responses are well-documented and have significant clinical implications. While the immunomodulatory effects of sex hormones are well established, the contributions of sex chromosome complement (XX vs. XY) and gut microbiome diversity on immune sexual dimorphisms have only recently become appreciated. Here we investigate the individual and collaborative influences of sex chromosome complements and gut microbiota on humoral immune activation.

METHODS

Male and female Four Core Genotype (FCG) mice were immunized with heat-killed Streptococcus pneumoniae (HKSP). Humoral immune responses were assessed, and X-linked immune-related gene expression was evaluated to explain the identified XX-dependent phenotype. The functional role of Kdm6a, an X-linked epigenetic regulatory gene of interest, was evaluated ex vivo using mitogen stimulation of B cells. Additional influences of the gut microbiome on sex chromosome-dependent B cell activation was also evaluated by antibiotically depleting gut microbiota prior to HKSP immunization. Reconstitution of the depleted microbiome with short-chain fatty acid (SCFA)-producing bacteria tested the impact of SCFAs on XX-dependent immune activation.

RESULTS

XX mice exhibited higher HKSP-specific IgM-secreting B cells and plasma cell frequencies than XY mice, regardless of gonadal sex. Although Kdm6a was identified as an X-linked gene overexpressed in XX B cells, inhibition of its enzymatic activity did not affect mitogen-induced plasma cell differentiation or antibody production in a sex chromosome-dependent manner ex vivo. Enhanced humoral responses in XX vs. XY immunized FCG mice were eliminated after microbiome depletion, indicating that the microbiome contributes to the identified XX-dependent immune enhancement. Reconstituting microbiota-depleted mice with select SCFA-producing bacteria enhanced fecal SCFA concentrations and increased humoral responses in XX, but not XY, FCG mice. However, exposure to the SCFA propionate alone did not enhance mitogenic B cell stimulation in ex vivo studies.

CONCLUSIONS

FCG mice have been used to assess sex hormone and sex chromosome complement influences on various sexually dimorphic traits. The current study indicates that the gut microbiome impacts humoral responses in an XX-dependent manner, suggesting that the collaborative influence of gut bacteria and other sex-specific factors should be considered when interpreting data aimed at delineating the mechanisms that promote sexual dimorphism.

Heme oxygenase-1 alleviates allergic airway inflammation by suppressing NF-κB-mediated pyroptosis of bronchial epithelial cells

Allergic asthma development and pathogenesis are influenced by airway epithelial cells in response to allergens. Heme oxygenase-1 (HO-1), an inducible enzyme responsible for the breakdown of heme, has been considered an appealing target for the treatment of chronic inflammatory diseases. Herein, we report that alleviation of allergic airway inflammation by HO-1-mediated suppression of pyroptosis in airway epithelial cells (AECs). Using house dust mite (HDM)-induced asthma models of mice, we found increased gasdermin D (GSDMD) in the airway epithelium. In vivo administration of disulfiram, a specific inhibitor of pore formation by GSDMD, decreased thymic stromal lymphopoietin (TSLP) release, T helper type 2 immune response, alleviated airway inflammation, and reduced airway hyperresponsiveness (AHR). HO-1 induction by hemin administration reversed these phenotypes. In vitro studies revealed that HO-1 restrained GSDMD-mediated pyroptosis and cytokine TSLP release in AECs by binding Nuclear Factor-Kappa B (NF-κB) p65 RHD domain and thus controlling NF-κB-dependent pyroptosis. These data provide new therapeutic indications for purposing HO-1 to counteract inflammation, which contributes to allergic inflammation control.

The Effects of Neuroactive Steroids on Myelin in Health and Disease

Myelin plays a pivotal role in the efficient transmission of nerve impulses. Disruptions in myelin integrity are associated with numerous neurological disorders, including multiple sclerosis. In the central nervous system (CNS), myelin is formed by oligodendrocytes. Remyelination refers to the re-formation of the damaged myelin sheath by newly formed oligodendrocytes. Steroids have gained attention for their potential modulatory effects on myelin in both health and disease. Steroids are traditionally associated with endocrine functions, but their local synthesis within the nervous system has generated significant interest. The term "neuroactive steroids" refers to steroids that can act on cells of the nervous system. In the healthy state, neuroactive steroids promote myelin formation, maintenance, and repair by enhancing oligodendrocyte differentiation and maturation. In pathological conditions, such as demyelination injury, multiple neuroactive steroids have shown promise in promoting remyelination. Understanding the effects of neuroactive steroids on myelin could lead to novel therapeutic approaches for demyelinating diseases and neurodegenerative disorders. This review highlights the potential therapeutic significance of neuroactive steroids in myelin-related health and diseases. We review the synthesis of steroids by neurons and glial cells and discuss the roles of neuroactive steroids on myelin structure and function in health and disease. We emphasize the potential promyelinating effects of the varying levels of neuroactive steroids during different female physiological states such as the menstrual cycle, pregnancy, lactation, and postmenopause.

Interplay between androgen and CXCR4 chemokine signaling in myelin repair

In men, reduced levels of testosterone are associated with the prevalence and progression of multiple sclerosis (MS), a chronic and disabling demyelinating disorder. Testosterone has been shown to promote myelin repair. Here, we demonstrate that the cooperation between testosterone and CXCR4 signaling involving astrocytes is required for myelin regeneration after focal demyelination produced in the ventral mouse spinal cord by the infusion of lysolecithin. The testosterone-dependent remyelination of axons by oligodendrocytes was accompanied by an increase in astrocytes expressing CXCR4, its ligand CXCL12 and the androgen receptor (AR) within the demyelinated area. Depriving males of their testosterone or pharmacological inhibition of CXCR4, with the selective antagonist AMD3100, prevented the appearance of astrocytes expressing CXCR4, CXCL12 and AR within the demyelinated area and the concomitant recruitment of myelin forming oligodendrocytes. Conditional genetic ablation of either CXCR4 or AR in astrocytes also completely blocked the formation of new myelin by oligodendrocytes. Interestingly, the gain of function mutation in CXCR4 causing WHIM syndrome allows remyelination to take place, even in the absence of testosterone, but its potentiating effects remained observable. After testosterone deprivation or CXCR4 inhibition, the absence of astrocytes within the demyelinated area led to the incursion of Schwann cells, most likely derived from spinal nerves, and the formation of peripheral nerve type myelin. In patients with progressive MS, astrocytes expressing CXCR4 and AR surrounded myelin lesions, and their presence opposed the incursion of Schwann cells. These results highlight a mechanism of promyelinating testosterone signaling and the importance of normalizing its levels in combined myelin repair therapies.

XX sex chromosome complement modulates immune responses to heat-killed Streptococcus pneumoniae immunization in a microbiome-dependent manner

Background

Differences in male vs. female immune responses are well-documented and have significant clinical implications. While the immunomodulatory effects of sex hormones are well established, the contributions of sex chromosome complement (XX vs. XY) and gut microbiome diversity on immune sexual dimorphisms have only recently become appreciated. Here we investigate the individual and collaborative influences of sex chromosome complements and gut microbiome bacteria on humoral immune activation.

Methods

Sham-operated and gonadectomized male and female Four Core Genotype (FCG) mice were immunized with heat-killed Streptococcus pneumoniae (HKSP). Humoral immune responses were assessed, and X-linked immune-related gene expression was evaluated to explain the identified XX-dependent phenotypes. Ex vivo studies investigated the functional role of Kdm6a, an X-linked epigenetic regulatory gene of interest, in mitogenic B cell activation. Additionally, we examined whether gut microbiome communities, or their metabolites, differentially influence immune cell activation in a sex chromosome-dependent manner. Endogenous gut microbiomes were antibiotically depleted and reconstituted with select short-chain fatty acid (SCFA)-producing bacteria prior to HKSP immunization and immune responses assessed.

Results

XX mice exhibited higher HKSP-specific IgM-secreting B cells and plasma cell frequencies than XY mice, regardless of gonadal sex. Although Kdm6a was identified as an X-linked gene overexpressed in XX B cells, inhibition of its enzymatic activity did not affect mitogen-induced plasma cell differentiation or antibody production in a sex chromosome-dependent manner ex vivo. Enhanced humoral responses in XX vs. XY immunized FCG mice were eliminated after microbiome depletion, indicating that the microbiome contributes to the identified XX-dependent immune enhancement. Reconstituting microbiota-depleted mice with select SCFA-producing bacteria increased humoral responses in XX, but not XY, FCG mice. This XX-dependent enhancement appears to be independent of SCFA production in males, while female XX-dependent responses relied on SCFAs.

Conclusions

FCG mice have been used to assess the influence of sex hormones and sex chromosome complements on various sexually dimorphic traits. The current study indicates that the gut microbiome impacts humoral responses in an XX-dependent manner, suggesting that the collaborative influence of gut bacteria and other sex-specific factors should be considered when interpreting data aimed at delineating the mechanisms that promote sexual dimorphism.

Impact of multiple sclerosis on male sexual and reproductive health

Multiple sclerosis (MS) is a chronic inflammatory and autoimmune neurodegenerative disease characterized by the destruction of myelin in the central nervous system, leading to significant health and quality of life burdens for patients. MS is most prevalent in younger individuals aged 20-40, a critical period when many patients hope to establish relationships and start families. While neurological disability, such as fatigue, sensory dysfunction, spasticity, and cognitive dysfunction, have been greatly improved with the advances in managing MS, physicians are frequently confronted with sexual and reproductive problems among younger male people with MS (PwMS). These issues mainly include erectile dysfunction, ejaculatory disorders, reduced libido, decreased sperm quality, and impaired male fertility. Despite recent studies indicating that MS negatively impacts the sexuality and fertility of male PwMS, these issues have not received sufficient attention. Genetic factors, autoimmunity, chronic inflammation, psychological factors, and the use of drugs may contribute to sexual/reproductive dysfunction in PwMS. However, like the overall understanding of MS pathophysiology, the complete mechanisms of its development remain unclear. In this study, we review the existing literature to summarize the range of sexual and reproductive issues unique to males with MS, explore potential underlying mechanisms, and aim to improve these issues in male PwMS. By shedding light on this overlooked aspect of MS, we hope to enhance the care and well-being of male PwMS facing these challenges.

The X-linked histone demethylases KDM5C and KDM6A as regulators of T cell-driven autoimmunity in the central nervous system

T cell-driven autoimmune responses are subject to striking sex-dependent effects. While the contributions of sex hormones are well-understood, those of sex chromosomes are meeting with increased appreciation. Here, we outline what is known about the contribution of sex chromosome-linked factors to experimental autoimmune encephalomyelitis (EAE), a mouse model that recapitulates many of the T cell-driven mechanisms of multiple sclerosis (MS) pathology. Particular attention is paid to the KDM family of histone demethylases, several of which - KDM5C, KDM5D and KDM6A - are sex chromosome encoded. Finally, we provide evidence that functional inhibition of KDM5 molecules can suppress interferon (IFN)γ production from murine male effector T cells, and that an increased ratio of inflammatory Kdm6a to immunomodulatory Kdm5c transcript is observed in T helper 17 (Th17) cells from women with the autoimmune disorder ankylosing spondylitis (AS). Histone lysine demethlyases thus represent intriguing targets for the treatment of T cell-driven autoimmune disorders.

Neuroprotection in Cerebral Cortex Induced by the Pregnancy Hormone Estriol

In multiple sclerosis (MS), demyelination occurs in the cerebral cortex, and cerebral cortex atrophy correlates with clinical disabilities. Treatments are needed in MS to induce remyelination. Pregnancy is protective in MS. Estriol is made by the fetoplacental unit, and maternal serum estriol levels temporally align with fetal myelination. Here, we determined the effect of estriol treatment on the cerebral cortex in the preclinical model of MS, experimental autoimmune encephalomyelitis (EAE). Estriol treatment initiated after disease onset decreased cerebral cortex atrophy. Neuropathology of the cerebral cortex showed increased cholesterol synthesis proteins in oligodendrocytes, more newly formed remyelinating oligodendrocytes, and increased myelin in estriol-treated EAE mice. Estriol treatment also decreased the loss of cortical layer V pyramidal neurons and their apical dendrites and preserved synapses. Together, estriol treatment after EAE onset reduced atrophy and was neuroprotective in the cerebral cortex.

Androgens show sex-dependent differences in myelination in immune and non-immune murine models of CNS demyelination

Neuroprotective, anti-inflammatory, and remyelinating properties of androgens are well-characterized in demyelinated male mice and men suffering from multiple sclerosis. However, androgen effects mediated by the androgen receptor (AR), have been only poorly studied in females who make low androgen levels. Here, we show a predominant microglial AR expression in demyelinated lesions from female mice and women with multiple sclerosis, but virtually undetectable AR expression in lesions from male animals and men with multiple sclerosis. In female mice, androgens and estrogens act in a synergistic way while androgens drive microglia response towards regeneration. Transcriptomic comparisons of demyelinated mouse spinal cords indicate that, regardless of the sex, androgens up-regulate genes related to neuronal function integrity and myelin production. Depending on the sex, androgens down-regulate genes related to the immune system in females and lipid catabolism in males. Thus, androgens are required for proper myelin regeneration in females and therapeutic approaches of demyelinating diseases need to consider male-female differences.

Male sex hormones, aging, and inflammation

Adequate levels of androgens (eugonadism), and specifically testosterone, are vital compounds for male quality of life, longevity, and positive health outcomes. Testosterone exerts its effects by binding to the androgen receptor, which is expressed in numerous tissues throughout the body. Significant research has been conducted on the impact of this steroid hormone on skeletal, muscle and adipose tissues and on the cardiovascular, immune, and nervous systems. Testosterone levels have also been studied in relation to the impact of diseases, aging, nutrition and the environment on its circulating levels. Conversely, the impact of testosterone on health has also been evaluated with respect to its cardiac and vascular protective effects, body composition, autoimmunity and all-cause mortality. The male aging process results in decreasing testosterone levels over time. The exact mechanisms and impact of these changes in testosterone levels with age on health- and life-span are still not completely clear. Further research is needed to determine the optimal testosterone and androgen levels to protect from chronic age-related conditions such as frailty and osteoporosis.

The X factor in neurodegeneration

Given the aging population, it is important to better understand neurodegeneration in aging healthy people and to address the increasing incidence of neurodegenerative diseases. It is imperative to apply novel strategies to identify neuroprotective therapeutics. The study of sex differences in neurodegeneration can reveal new candidate treatment targets tailored for women and men. Sex chromosome effects on neurodegeneration remain understudied and represent a promising frontier for discovery. Here, we will review sex differences in neurodegeneration, focusing on the study of sex chromosome effects in the context of declining levels of sex hormones during aging.

Effects of biological sex and pregnancy in experimental autoimmune encephalomyelitis: It's complicated

Experimental autoimmune encephalomyelitis (EAE) can be induced in many animal strains by inoculation with central nervous system antigens and adjuvant or by the passive transfer of lymphocytes reactive with these antigens and is widely used as an animal model for multiple sclerosis (MS). There are reports that female sex and pregnancy affect EAE. Here we review the effects of biological sex and the effects of pregnancy on the clinical features (including disease susceptibility) and pathophysiology of EAE. We also review reports of the possible mechanisms underlying these differences. These include sex-related differences in the immune system and in the central nervous system, the effects of hormones and the sex chromosomes and molecules unique to pregnancy. We also review sex differences in the response to factors that can modify the course of EAE. Our conclusion is that the effects of biological sex in EAE vary amongst animal models and should not be widely extrapolated. In EAE, it is therefore essential that studies looking at the effects of biological sex or pregnancy give full information about the model that is used (i.e. animal strain, sex, the inducing antigen, timing of EAE induction in relation to pregnancy, etc.). In addition, it would be preferable if more than one EAE model were used, to show if any observed effects are generalizable. This is clearly a field that requires further work. However, understanding of the mechanisms of sex differences could lead to greater understanding of EAE, and suggest possible therapies for MS.

Gammaherpesvirus infection drives age-associated B cells toward pathogenicity in EAE and MS

While age-associated B cells (ABCs) are known to expand and persist following viral infection and during autoimmunity, their interactions are yet to be studied together in these contexts. Here, we directly compared CD11c⁺T-bet⁺ ABCs using models of Epstein-Barr virus (EBV), gammaherpesvirus 68 (γHV68), multiple sclerosis (MS), and experimental autoimmune encephalomyelitis (EAE), and found that each drives the ABC population to opposing phenotypes. EBV infection has long been implicated in MS, and we have previously shown that latent γHV68 infection exacerbates EAE. Here, we demonstrate that ABCs are required for γHV68-enhanced disease. We then show that the circulating ABC population is expanded and phenotypically altered in people with relapsing MS. In this study, we show that viral infection and autoimmunity differentially affect the phenotype of ABCs in humans and mice, and we identify ABCs as functional mediators of viral-enhanced autoimmunity.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

Immune Cell Contributors to the Female Sex Bias in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is a chronic, autoimmune, demyelinating disease of the central nervous system (CNS) that leads to axonal damage and accumulation of disability. Relapsing-remitting MS (RR-MS) is the most frequent presentation of MS and this form of MS is three times more prevalent in females than in males. This female bias in MS is apparent only after puberty, suggesting a role for sex hormones in this regulation; however, very little is known of the biological mechanisms that underpin the sex difference in MS onset. Experimental autoimmune encephalomyelitis (EAE) is an animal model of RR-MS that presents more severely in females in certain mouse strains and thus has been useful to study sex differences in CNS autoimmunity. Here, we overview the immunopathogenesis of MS and EAE and how immune mechanisms in these diseases differ between a male and female. We further describe how females exhibit more robust myelin-specific T helper (Th) 1 immunity in MS and EAE and how this sex bias in Th cells is conveyed by sex hormone effects on the T cells, antigen presenting cells, regulatory T cells, and innate lymphoid cell populations.

An optimized and validated protocol for inducing chronic experimental autoimmune encephalomyelitis in C57BL/6J mice

BACKGROUND

Myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalomyelitis (EAE) is the most commonly used animal model of multiple sclerosis. However, variations in the induction protocol can affect EAE progression, and may reduce the comparability of data.

OPTIMIZED METHOD

In the present study, we investigated the influence of the different components used for EAE induction in C57BL/6J mice on disease progression. In the present study, MOG_35-55-induced chronic EAE in C57BL/6J mice has been applied as a model to challenge optimal pertussis toxin (PTx) dosing, while considering variations in batch potency.

RESULTS

We demonstrate that the dosage of PTx, adjusted to its potency, influences EAE development in a dose-dependent manner. Our data show that with our protocol, which considers PTx potency, C57BL/6J mice consistently develop symptoms of EAE. The mice show a typical chronic course with symptom onset after 10.5 ± 1.08 days and maximum severity around day 16 postimmunization followed by a mild remission of symptoms.

COMPARISON WITH EXISTING METHODS

Previously studies reveal that alterations in PTx dosing directly modify EAE progression. Our present study highlights that PTx batches differ in potency, resulting in inconsistent EAE induction. We also provide a clear protocol that allows a reduction in the number of mice used in EAE experiments, while maintaining consistent results.

CONCLUSION

Higher standards for comparability and reproducibility are needed to ensure and maximize the generation of reliable EAE data. Specifically, consideration of PTx potency. With our method of establishing consistent EAE pathogenesis, improved animal welfare standards and a reduction of mice used in experimentation can be achieved.

The autoimmune encephalitis-related cytokine TSLP in the brain primes neuroinflammation by activating the JAK2-NLRP3 axis

NLRP3 inflammasome hyperactivation contributes to neuroinflammation in autoimmune disorders, but the underlying regulatory mechanism remains to be elucidated. We demonstrate that compared with wild-type (WT) mice, mice lacking thymic stromal lymphopoietin (TSLP) receptor (TSLPR) (Tslpr^−/− mice) exhibit a significantly decreased experimental autoimmune encephalomyelitis (EAE) score, reduced CD4⁺ T cell infiltration, and restored myelin basic protein (MBP) expression in the brain after EAE induction by myelin oligodendrocyte glycoprotein_35–55 (MOG_35–55). TSLPR signals through Janus kinase (JAK)2, but not JAK1 or JAK3, to induce NLRP3 expression, and Tslpr^−/− mice with EAE show decreased JAK2 phosphorylation and NLRP3 expression in the brain. JAK2 inhibition by ruxolitinib mimicked loss of TSLPR function in vivo and further decreased TSLP expression in the EAE mouse brain. The NLRP3 inhibitor MCC950 decreased CD4⁺ T cell infiltration, restored MBP expression, and decreased IL-1β and TSLP levels, verifying the pro-inflammatory role of NLRP3. In vitro experiments using BV-2 murine microglia revealed that TSLP directly induced NLRP3 expression, phosphorylation of JAK2 but not JAK1orJAK3, and IL-1β release, which were markedly inhibited by ruxolitinib. Furthermore, EAE induction led to an increase in the Th17 cell number, a decrease in the regulatory T (Treg) cell number in the blood, and an increase in the expression of the cytokine IL-17A in the WT mouse brain, which was drastically reversed in Tslpr^−/− mice. In addition, ruxolitinib suppressed the increase in IL-17A expression in the EAE mouse brain. These findings identify TSLP as a prospective target for treating JAK2-NLRP3 axis-associated autoimmune inflammatory disorders.

Testicular steroidogenesis is suppressed during experimental autoimmune encephalomyelitis in rats

Multiple sclerosis (MS) is an autoimmune disease that usually occurs during the reproductive years in both sexes. Many male patients with MS show lower blood testosterone levels, which was also observed in male rats during experimental autoimmune encephalomyelitis (EAE), an animal model of MS. To better understand the causes of decreased testosterone production during EAE, we investigated the expression status of genes and proteins associated with steroidogenesis in the testes. No changes in the number of interstitial cells were observed in EAE animals, but the expression of the insulin-like 3 gene was reduced at the peak of the disease, implying that the Leydig cell functional capacity was affected. Consistent with this finding, the expression of most steroidogenic enzyme genes and proteins was reduced during EAE, including StAR, CYP11A1, CYP17A1 and HSD3B. No signs of testicular inflammation were observed. Recovery of steroidogenesis was observed after injection of hCG, the placental gonadotropin, or buserelin acetate, a gonadotropin-releasing hormone analogue, at the peak of EAE. Together, our results are consistent with the hypothesis that impaired testicular steroidogenesis originates upstream of the testes and that low serum LH is the main cause of decreased testosterone levels during EAE.

Hormonal Regulation of Oligodendrogenesis II: Implications for Myelin Repair

Alterations in myelin, the protective and insulating sheath surrounding axons, affect brain function, as is evident in demyelinating diseases where the loss of myelin leads to cognitive and motor dysfunction. Recent evidence suggests that changes in myelination, including both hyper- and hypo-myelination, may also play a role in numerous neurological and psychiatric diseases. Protecting myelin and promoting remyelination is thus crucial for a wide range of disorders. Oligodendrocytes (OLs) are the cells that generate myelin, and oligodendrogenesis, the creation of new OLs, continues throughout life and is necessary for myelin plasticity and remyelination. Understanding the regulation of oligodendrogenesis and myelin plasticity within disease contexts is, therefore, critical for the development of novel therapeutic targets. In our companion manuscript, we review literature demonstrating that multiple hormone classes are involved in the regulation of oligodendrogenesis under physiological conditions. The majority of hormones enhance oligodendrogenesis, increasing oligodendrocyte precursor cell differentiation and inducing maturation and myelin production in OLs. Thus, hormonal treatments present a promising route to promote remyelination. Here, we review the literature on hormonal regulation of oligodendrogenesis within the context of disorders. We focus on steroid hormones, including glucocorticoids and sex hormones, peptide hormones such as insulin-like growth factor 1, and thyroid hormones. For each hormone, we describe whether they aid in OL survival, differentiation, or remyelination, and we discuss their mechanisms of action, if known. Several of these hormones have yielded promising results in both animal models and in human conditions; however, a better understanding of hormonal effects, interactions, and their mechanisms will ultimately lead to more targeted therapeutics for myelin repair.

Neuroprotective Effects of Testosterone in Male Wobbler Mouse, a Model of Amyotrophic Lateral Sclerosis

Patients suffering of amyotrophic lateral sclerosis (ALS) present motoneuron degeneration leading to muscle atrophy, dysphagia, and dysarthria. The Wobbler mouse, an animal model of ALS, shows a selective loss of motoneurons, astrocytosis, and microgliosis in the spinal cord. The incidence of ALS is greater in men; however, it increases in women after menopause, suggesting a role of sex steroids in ALS. Testosterone is a complex steroid that exerts its effects directly via androgen (AR) or Sigma-1 receptors and indirectly via estrogen receptors (ER) after aromatization into estradiol. Its reduced-metabolite 5α-dihydrotestosterone acts via AR. This study analyzed the effects of testosterone in male symptomatic Wobblers. Controls or Wobblers received empty or testosterone-filled silastic tubes for 2 months. The cervical spinal cord from testosterone-treated Wobblers showed (1) similar androgen levels to untreated control and (2) increased levels of testosterone, and its 5α-reduced metabolites, 5α- dihydrotestosterone, and 3β-androstanediol, but (3) undetectable levels of estradiol compared to untreated Wobblers. Testosterone-treated controls showed comparable steroid concentrations to its untreated counterpart. In testosterone- treated Wobblers a reduction of AR, ERα, and aromatase and high levels of Sigma-1 receptor mRNAs was demonstrated. Testosterone treatment increased ChAT immunoreactivity and the antiinflammatory mediator TGFβ, while it lessened vacuolated motoneurons, GFAP+ astrogliosis, the density of IBA1+ microgliosis, proinflammatory mediators, and oxidative/nitrosative stress. Clinically, testosterone treatment in Wobblers slowed the progression of paw atrophy and improved rotarod performance. Collectively, our findings indicate an antiinflammatory and protective effect of testosterone in the degenerating spinal cord. These results coincided with a high concentration of androgen-reduced derivatives after testosterone treatment suggesting that the steroid profile may have a beneficial role on disease progression.

Mechanisms of sex hormones in autoimmunity: focus on EAE

Sex-related differences in the occurrence of autoimmune diseases is well documented, with females showing a greater propensity to develop these diseases than their male counterparts. Sex hormones, namely dihydrotestosterone and estrogens, have been shown to ameliorate the severity of inflammatory diseases. Immunologically, the beneficial effects of sex hormones have been ascribed to the suppression of effector lymphocyte responses accompanied by immune deviation from pro-inflammatory to anti-inflammatory cytokine production. In this review, we present our view of the mechanisms of sex hormones that contribute to their ability to suppress autoimmune responses with an emphasis on the pathogenesis of experimental autoimmune encephalomyelitis.

Androgen Therapy in Neurodegenerative Diseases

Neurodegenerative diseases, including Alzheimer disease (AD), Parkinson disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and Huntington disease, are characterized by the loss of neurons as well as neuronal function in multiple regions of the central and peripheral nervous systems. Several studies in animal models have shown that androgens have neuroprotective effects in the brain and stimulate axonal regeneration. The presence of neuronal androgen receptors in the peripheral and central nervous system suggests that androgen therapy might be useful in the treatment of neurodegenerative diseases. To illustrate, androgen therapy reduced inflammation, amyloid-β deposition, and cognitive impairment in patients with AD. As well, improvements in remyelination in MS have been reported; by comparison, only variable results are observed in androgen treatment of PD. In ALS, androgen administration stimulated motoneuron recovery from progressive damage and regenerated both axons and dendrites. Only a few clinical studies are available in human individuals despite the safety and low cost of androgen therapy. Clinical evaluations of the effects of androgen therapy on these devastating diseases using large populations of patients are strongly needed.

Intranasal Methylprednisolone Effectively Reduces Neuroinflammation in Mice With Experimental Autoimmune Encephalitis

Relapsing-remitting multiple sclerosis, the most common form, is characterized by acute neuroinflammatory episodes. In addition to continuous disease-modifying therapy, these relapses require treatment to prevent lesion accumulation and progression of disability. Intravenous methylprednisolone (1-2 g for 3-5 days) is the standard treatment for relapses. However, this treatment is invasive, requires hospitalization, leads to substantial systemic exposure of glucocorticoids, and can only reach modest concentrations in the central nervous system (CNS). Intranasal delivery may represent an alternative to deliver relapse treatment directly to the CNS with higher concentrations and reducing side effects. Histopathological analysis revealed that intranasal administration of methylprednisolone to mice with experimental autoimmune encephalomyelitis (EAE) suppressed the neuroinflammatory peak, and reduced immune cell infiltration and demyelination in the CNS similarly to intravenous administration. Treatment also downregulated Iba1 and GFAP expression. A similar significant reduction of IL-1β, IL-6, IL-17, IFN-γ, and TNF-α levels in the spinal cord was attained in both intranasal and intravenously treated mice. No damage in the nasal cavity was found after intranasal administration. This study demonstrates that intranasal delivery of methylprednisolone is as efficient as the intravenous route to treat neuroinflammation in EAE.

Impact of Androgens on Inflammation-Related Lipid Mediator Biosynthesis in Innate Immune Cells

Rheumatoid arthritis, asthma, allergic rhinitis and many other disorders related to an aberrant immune response have a higher incidence and severity in women than in men. Emerging evidences from scientific studies indicate that the activity of the immune system is superior in females and that androgens may act as “immunosuppressive” molecules with inhibitory effects on inflammatory reactions. Among the multiple factors that contribute to the inflammatory response, lipid mediators (LM), produced from polyunsaturated fatty acids, represent a class of bioactive small molecules with pivotal roles in the onset, maintenance and resolution of inflammation. LM encompass pro-inflammatory eicosanoids and specialized pro-resolving mediators (SPM) that coexist in a tightly regulated balance necessary for the return to homeostasis. Innate immune cells including neutrophils, monocytes and macrophages possess high capacities to generate distinct LM. In the last decades it became more and more evident that sex represents an important variable in the regulation of inflammation where sex hormones play crucial roles. Recent findings showed that the biosynthesis of inflammation-related LM is sex-biased and that androgens impact LM formation with consequences not only for pathophysiology but also for pharmacotherapy. Here, we review the modulation of the inflammatory response by sex and androgens with a specific focus on LM pathways. In particular, we highlight the impact of androgens on the biosynthetic pathway of inflammation-related eicosanoids in innate immune cells.

Roles of Progesterone, Testosterone and Their Nuclear Receptors in Central Nervous System Myelination and Remyelination

Progesterone and testosterone, beyond their roles as sex hormones, are neuroactive steroids, playing crucial regulatory functions within the nervous system. Among these, neuroprotection and myelin regeneration are important ones. The present review aims to discuss the stimulatory effects of progesterone and testosterone on the process of myelination and remyelination. These effects have been demonstrated in vitro (i.e., organotypic cultures) and in vivo (cuprizone- or lysolecithin-induced demyelination and experimental autoimmune encephalomyelitis (EAE)). Both steroids stimulate myelin formation and regeneration by acting through their respective intracellular receptors: progesterone receptors (PR) and androgen receptors (AR). Activation of these receptors results in multiple events involving direct transcription and translation, regulating general homeostasis, cell proliferation, differentiation, growth and myelination. It also ameliorates immune response as seen in the EAE model, resulting in a significant decrease in inflammation leading to a fast recovery. Although natural progesterone and testosterone have a therapeutic potential, their synthetic derivatives—the 19-norprogesterone (nestorone) and 7α-methyl-nortestosterone (MENT), already used as hormonal contraception or in postmenopausal hormone replacement therapies, may offer enhanced benefits for myelin repair. We summarize here a recent advancement in the field of myelin biology, to treat demyelinating disorders using the natural as well as synthetic analogs of progesterone and testosterone.

Physiopathological role of the enzymatic complex 5α-reductase and 3α/β-hydroxysteroid oxidoreductase in the generation of progesterone and testosterone neuroactive metabolites

The enzymatic complex 5α-reductase (5α-R) and 3α/3β-hydroxysteroid oxidoreductase (HSOR) is expressed in the nervous system, where it transforms progesterone (PROG) and testosterone (T) into neuroactive metabolites. These metabolites regulate myelination, brain maturation, neurotransmission, reproductive behavior and the stress response. The expression of 5α-R and 3α-HSOR and the levels of PROG and T reduced metabolites show regional and sex differences in the nervous system and are affected by changing physiological conditions as well as by neurodegenerative and psychiatric disorders. A decrease in their nervous tissue levels may negatively impact the course and outcome of some pathological events. However, in other pathological conditions their increased levels may have a negative impact. Thus, the use of synthetic analogues of these steroids or 5α-R modulation have been proposed as therapeutic approaches for several nervous system pathologies. However, further research is needed to fully understand the consequences of these manipulations, in particular with 5α-R inhibitors.

Sex-related differences in urinary immune-related metabolic profiling of alopecia areata patients

INTRODUCTION

Alopecia areata is a well-known autoimmune disease affecting humans. Polyamines are closely associated with proliferation and inflammation, and steroid hormones are involved in immune responses. Additionally, bile acids play roles in immune homeostasis by activating various signaling pathways; however, the roles of these substances and their metabolites in alopecia areata remain unclear.

OBJECTIVES

In this study, we aimed to identify differences in metabolite levels in urine samples from patients with alopecia areata and healthy controls.

METHODS

To assess polyamine, androgen, and bile acid concentrations, we performed high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Our results showed that spermine and dehydroepiandrosterone levels differed significantly between male patients and controls, whereas ursodeoxycholic acid levels were significantly higher in female patients with alopecia areata than in controls.

CONCLUSION

Our findings suggested different urinary polyamine, androgen, and bile acid concentrations between alopecia areata patients and normal controls. Additionally, levels of endogenous substances varied according to sex, and this should be considered when developing appropriate treatments and diagnostic techniques. Our findings improve our understanding of polyamine, androgen, and bile acid profiles in patients with alopecia areata and highlight the need to consider sex-related differences.

An Inconvenient Variable: Sex Hormones and Their Impact on T Cell Responses

Epidemiologic data demonstrate sex differences in autoimmune diseases, immune responses against infection, and antitumor immunity, and accumulating evidence suggests a major role for sex hormones in mediating these differences. In this study, we review recent advances in understanding how sex hormones regulate T cell responses to alter susceptibility to autoimmunity. Although sex hormones can directly alter gene transcriptional programs of T cells, we focus in this study on how sex hormones alter T cell development and function through their effects on thymic stromal cells and innate cell types. In addition to contributing to our understanding of sex differences, these findings also have implications for the therapeutic use of sex hormones and sex hormone modulators, which are now being prescribed to increasing numbers of patients for a wide variety of indications.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

Parent-of-origin differences in DNA methylation of X chromosome genes in T lymphocytes

Sex differences are naturally occurring disease modifiers that, if understood, could lead to novel targets for drug development. Autoimmune diseases are more prevalent in women than in men, and sex differences in immune responses have been shown in humans and mice. Here, we discover a global parent-of-origin difference in DNA methylation on the X chromosome that affects gene expression in activated CD4⁺ T lymphocytes. The paternal X has more methylation than the maternal X, with higher expression of X genes in XY cells since they only express from the maternal X. Thus, parent-of-origin differences in DNA methylation of X genes can play a role in sex differences in immune responses.

Many autoimmune diseases are more frequent in females than in males in humans and their mouse models, and sex differences in immune responses have been shown. Despite extensive studies of sex hormones, mechanisms underlying these sex differences remain unclear. Here, we focused on sex chromosomes using the “four core genotypes” model in C57BL/6 mice and discovered that the transcriptomes of both autoantigen and anti-CD3/CD28 stimulated CD4⁺ T lymphocytes showed higher expression of a cluster of 5 X genes when derived from XY as compared to XX mice. We next determined if higher expression of an X gene in XY compared to XX could be due to parent-of-origin differences in DNA methylation of the X chromosome. We found a global increase in DNA methylation on the X chromosome of paternal as compared to maternal origin. Since DNA methylation usually suppresses gene expression, this result was consistent with higher expression of X genes in XY cells because XY cells always express from the maternal X chromosome. In addition, gene expression analysis of F1 hybrid mice from CAST × FVB reciprocal crosses showed preferential gene expression from the maternal X compared to paternal X chromosome, revealing that these parent-of-origin effects are not strain-specific. SJL mice also showed a parent-of-origin effect on DNA methylation and X gene expression; however, which X genes were affected differed from those in C57BL/6. Together, this demonstrates how parent-of-origin differences in DNA methylation of the X chromosome can lead to sex differences in gene expression during immune responses.

TGFB1-Mediated Gliosis in Multiple Sclerosis Spinal Cords Is Favored by the Regionalized Expression of HOXA5 and the Age-Dependent Decline in Androgen Receptor Ligands

In multiple sclerosis (MS) patients with a progressive form of the disease, spinal cord (SC) functions slowly deteriorate beyond age 40. We previously showed that in the SC of these patients, large areas of incomplete demyelination extend distance away from plaque borders and are characterized by a unique progliotic TGFB1 (Transforming Growth Factor Beta 1) genomic signature. Here, we attempted to determine whether region- and age-specific physiological parameters could promote the progression of SC periplaques in MS patients beyond age 40. An analysis of transcriptomics databases showed that, under physiological conditions, a set of 10 homeobox (HOX) genes are highly significantly overexpressed in the human SC as compared to distinct brain regions. Among these HOX genes, a survey of the human proteome showed that only HOXA5 encodes a protein which interacts with a member of the TGF-beta signaling pathway, namely SMAD1 (SMAD family member 1). Moreover, HOXA5 was previously found to promote the TGF-beta pathway. Interestingly, SMAD1 is also a protein partner of the androgen receptor (AR) and an unsupervised analysis of gene ontology terms indicates that the AR pathway antagonizes the TGF-beta/SMAD pathway. Retrieval of promoter analysis data further confirmed that AR negatively regulates the transcription of several members of the TGF-beta/SMAD pathway. On this basis, we propose that in progressive MS patients, the physiological SC overexpression of HOXA5 combined with the age-dependent decline in AR ligands may favor the slow progression of TGFB1-mediated gliosis. Potential therapeutic implications are discussed.

Do Androgens Modulate the Pathophysiological Pathways of Inflammation? Appraising the Contemporary Evidence

The role of testosterone in the pathophysiology of inflammation is of critical clinical importance; however, no universal mechanism(s) has been advanced to explain the complex and interwoven pathways of androgens in the attenuation of the inflammatory processes. PubMed and EMBASE searches were performed, including the following key words: "testosterone", "androgens", "inflammatory cytokines", "inflammatory biomarkers" with focus on clinical studies as well as basic scientific studies in human and animal models. Significant benefits of testosterone therapy in ameliorating or attenuating the symptoms of several chronic inflammatory diseases were reported. Because anti⁻tumor necrosis factor therapy is the mainstay for the treatment of moderate-to-severe inflammatory bowel disease; including Crohn's disease and ulcerative colitis, and because testosterone therapy in hypogonadal men with chronic inflammatory conditions reduce tumor necrosis factor-alpha (TNF-α), IL-1β, and IL-6, we suggest that testosterone therapy attenuates the inflammatory process and reduces the burden of disease by mechanisms inhibiting inflammatory cytokine expression and function. Mechanistically, androgens regulate the expression and function of inflammatory cytokines, including TNF-α, IL-1β, IL-6, and CRP (C-reactive protein). Here, we suggest that testosterone regulates multiple and overlapping cellular and molecular pathways involving a host of immune cells and biochemical factors that converge to contribute to attenuation of the inflammatory process.

Neurodegenerative Diseases: Regenerative Mechanisms and Novel Therapeutic Approaches

Regeneration refers to regrowth of tissue in the central nervous system. It includes generation of new neurons, glia, myelin, and synapses, as well as the regaining of essential functions: sensory, motor, emotional and cognitive abilities. Unfortunately, regeneration within the nervous system is very slow compared to other body systems. This relative slowness is attributed to increased vulnerability to irreversible cellular insults and the loss of function due to the very long lifespan of neurons, the stretch of cells and cytoplasm over several dozens of inches throughout the body, insufficiency of the tissue-level waste removal system, and minimal neural cell proliferation/self-renewal capacity. In this context, the current review summarized the most common features of major neurodegenerative disorders; their causes and consequences and proposed novel therapeutic approaches.

Neuroactive steroids, neurosteroidogenesis and sex

The nervous system is a target and a source of steroids. Neuroactive steroids are steroids that target neurons and glial cells. They include hormonal steroids originated in the peripheral glands, steroids locally synthesized by the neurons and glial cells (neurosteroids) and synthetic steroids, some of them used in clinical practice. Here we review the mechanisms of synthesis, metabolism and action of neuroactive steroids, including the role of epigenetic modifications and the mitochondria in their sex specific actions. We examine sex differences in neuroactive steroid levels under physiological conditions and their role in the establishment of sex dimorphic structures in the nervous system and sex differences in its function. In addition, particular attention is paid to neuroactive steroids under pathological conditions, analyzing how pathology alters their levels and their role as neuroprotective factors, considering the influence of sex in both cases.

Androgen-Induced Immunosuppression

In addition to determining biological sex, sex hormones are known to influence health and disease via regulation of immune cell activities and modulation of target-organ susceptibility to immune-mediated damage. Systemic autoimmune disorders, such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis are more prevalent in females, while cancer shows the opposite pattern. Sex hormones have been repeatedly suggested to play a part in these biases. In this review, we will discuss how androgens and the expression of functional androgen receptor affect immune cells and how this may dampen or alter immune response(s) and affect autoimmune disease incidences and progression.

Mast Cells and Innate Lymphoid Cells: Underappreciated Players in CNS Autoimmune Demyelinating Disease

Multiple sclerosis (MS) and its mouse model, experimental autoimmune encephalomyelitis, are autoimmune CNS inflammatory diseases. As a result of a breakdown in the relatively impermeable blood–brain barrier (BBB) in affected individuals, myelin-specific CD4⁺ and CD8⁺ T cells gain entry into the immune privileged CNS and initiate myelin, oligodendrocyte, and nerve axon destruction. However, despite the absolute requirement for T cells, there is increasing evidence that innate immune cells also play critical amplifying roles in disease pathogenesis. By modulating the character and magnitude of the myelin-reactive T cell response and regulating BBB integrity, innate cells affect both disease initiation and progression. Two classes of innate cells, mast cells and innate lymphoid cells (ILCs), have been best studied in models of allergic and gastrointestinal inflammatory diseases. Yet, there is emerging evidence that these cell types also exert a profound influence in CNS inflammatory disease. Both cell types are residents within the meninges and can be activated early in disease to express a wide variety of disease-modifying cytokines and chemokines. In this review, we discuss how mast cells and ILCs can have either disease-promoting or -protecting effects on MS and other CNS inflammatory diseases and how sex hormones may influence this outcome. These observations suggest that targeting these cells and their unique mediators can be exploited therapeutically.

Male-specific IL-33 expression regulates sex-dimorphic EAE susceptibility

The cellular and molecular basis of sex-dimorphic autoimmune diseases, such as the CNS demyelinating disease multiple sclerosis (MS), remains unclear. Our studies in the SJL mouse model of MS, experimental autoimmune encephalomyelitis (EAE), reveal that sex-determined differences in Il33 expression by innate immune cells in response to myelin peptide immunization regulate EAE susceptibility. IL-33 is selectively induced in PLP_139-151-immunized males and activates type 2 innate lymphoid cells (ILC2s), cells that promote and sustain a nonpathogenic Th2 myelin-specific response. Without this attenuating IL-33 response, females generate an encephalitogenic Th17-dominant response, which can be reversed by IL-33 treatment. Mast cells are one source of IL-33 and we provide evidence that testosterone directly induces Il33 gene expression and also exerts effects on the potential for Il33 gene expression during mast cell development. Thus, in contrast to their pathogenic role in allergy, we propose a sex-specific role for both mast cells and ILC2s as attenuators of the pathogenic Th response in CNS inflammatory disease.

Single-nucleotide polymorphism rs948854 in human galanin gene and multiple sclerosis: a gender-specific risk factor

We performed comparative analyses of the genotype distribution and allelic frequencies of the rs948854 polymorphism (G/A) in the galanin gene's promoter in patients with multiple sclerosis (MS) and in healthy matched controls. In total 111 patients and 115 control subjects were included. The analyses revealed that the presence of the minor allele (G) increased susceptibility to MS in men (OR = 2.49, P = 0.008) but not in women. The presence of the G allele in men was also significantly associated with the late onset of MS. Furthermore, rs948854 polymorphism affected the rate of MS progression depending on the sex of the patients. In woman (typically slowly progressing), the percentage of patients with the slow (<0.5 EDSS score per year) progression rate was significantly reduced (χ²  = 5.7, P = 0.017) in the minor allele carriers group (52.6%), in comparison with the wild-type carriers (83.9%). In men (typically quickly progressing), the number of patients with fast progression rate (≥0.75 EDSS score per year) tended to increase in the minor allele carriers group (50%) compared with number of patients with the wild-type carriers (31.3%). These data demonstrate for the first time an association between rs948854 polymorphism and multiple sclerosis and, further, that this association is sex specific. They also point to diagnostic and prognostic benefits of genetic screening of patients with multiple sclerosis. © 2016 Wiley Periodicals, Inc.

The importance of studying sex differences in disease: The example of multiple sclerosis

To date, scientific research has often focused on one sex, with assumptions that study of the other sex would yield similar results. However, many diseases affect males and females differently. The sex of a patient can affect the risk for both disease susceptibility and progression. Such differences can be brought to the laboratory bench to be investigated, potentially bringing new treatments back to the clinic. This method of research, known as a "bedside to bench to bedside" approach, has been applied to studying sex differences in multiple sclerosis (MS). Females have greater susceptibly to MS, while males have worse disease progression. These two characteristics of the disease are influenced by the immune system and the nervous system, respectively. Thus, sex differences in each system must be studied. Personalized medicine has been at the forefront of research recently, and studying sex differences in disease fits with this initiative. This review will discuss the known sex differences in MS and highlight how investigating them can lead to new insights and potential treatments for both men and women. © 2016 Wiley Periodicals, Inc.

Male factor infertility and risk of multiple sclerosis: A register-based cohort study

Background:

Gender, possibly due to the influence of gonadal hormones, is presumed to play a role in the pathogenesis of multiple sclerosis (MS), but no studies have evaluated whether male infertility is associated with MS.

Objective:

To study the association between male factor infertility and prevalent as well as incident MS.

Method:

Our cohort was established by linkage of the Danish National in vitro fertilization (IVF) registry to The Danish Multiple Sclerosis Registry and consisted of 51,063 men whose partners had undergone fertility treatment in all public and private fertility clinics in Denmark between 1994 and 2015.

Results:

With a median age of 34 years at baseline, 24,011 men were diagnosed with male factor infertility and 27,052 did not have male factor infertility and made up the reference group. Men diagnosed with male factor infertility had a higher risk of prevalent (odds ratio (OR) = 1.61, 95% confidence interval (95% CI) 1.04–2.51) and incident MS (hazard ratio (HR) = 1.28, 95% CI 0.76–2.17) when compared to the reference group.

Conclusion:

This nationwide cohort study has shown, for the first time, an association between male infertility and MS which may be due to underlying common etiologies such as hypogonadism, shared genetics, or a joint autoimmune component.

Unexpected central role of the androgen receptor in the spontaneous regeneration of myelin

Lost myelin can be replaced after injury or during demyelinating diseases in a regenerative process called remyelination. In the central nervous system (CNS), the myelin sheaths, which protect axons and allow the fast propagation of electrical impulses, are produced by oligodendrocytes. The abundance and widespread distribution of oligodendrocyte progenitors (OPs) within the adult CNS account for this remarkable regenerative potential. Here, we report a key role for the male gonad, testosterone, and androgen receptor (AR) in CNS remyelination. After lysolecithin-induced demyelination of the male mouse ventral spinal cord white matter, the recruitment of glial fibrillary acidic protein-expressing astrocytes was compromised in the absence of testes and testosterone signaling via AR. Concomitantly, the differentiation of OPs into oligodendrocytes forming myelin basic protein (MBP)⁺ and proteolipid protein-positive myelin was impaired. Instead, in the absence of astrocytes, axons were remyelinated by protein zero (P0)⁺ and peripheral myelin protein 22-kDa (PMP22)⁺ myelin, normally only produced by Schwann cells in the peripheral nervous system. Thus, testosterone favors astrocyte recruitment and spontaneous oligodendrocyte-mediated remyelination. This finding may have important implications for demyelinating diseases, psychiatric disorders, and cognitive aging. The testosterone dependency of CNS oligodendrocyte remyelination may have roots in the evolutionary history of the AR, because the receptor has evolved from an ancestral 3-ketosteroid receptor through gene duplication at the time when myelin appeared in jawed vertebrates.

Novel model of double transgenic mouse results in autoimmune diabetes in males

Identifying the type of diabetogenic CD8⁺ T cells that initiate autoimmune diabetes (AID) is a critical step in designing appropriate strategies for the early detection of beta cell-directed autoimmunity and its progression to diabetes. We generated a novel double transgenic (Tg) mouse model on the naturally diabetes resistant C57Bl/6 background, co-expressing two transgenes including a specific TCR anti-lymphocytic choriomeningitis virus nucleoprotein (LCMV-NP) carried by CD8⁺ T cells and LCMV-NP (as neo-self antigen) expressed by pancreatic beta cells. The resulting double Tg mouse showed partial thymic deletion of the NP-specific CD8⁺ T cells. The escaping autoreactive NP-specific CD8⁺ T cells joining the periphery were activated and gained effector functions. Both male and female mice mounted anti-NP antibodies, but only one-fourth adult males spontaneously developed AID. Significant upregulation of the CD44 and CD122 markers as compared to healthy male and female mice characterized the phenotype of diabetogenic CD8⁺ T cells in diabetic male mice. We also show that only 10% of these CD8⁺T cells expressed programmed death 1 receptor (PD-1). Together, these results suggest that in our double Tg mouse model, Ag-specific effector CD44⁺CD122⁺PD-1^-CD8⁺ T cell subpopulation is associated with the pathogenesis of AID.

Structural sex differences at disease onset in multiple sclerosis patients

BACKGROUND

Male sex is associated with worsening disability and a more rapid progression of multiple sclerosis (MS). This study analysed structural sex differences in magnetic resonance images of the brain, comparing women whose disease started before and after the menopause with a control group of men.

METHODS

This was a case control study in which female patients whose MS started before (Group 1) and after (Group 2) the menopause were included. The control group was matched by age, disease duration, Expanded Disability Status Scale and disease-modifying treatment. Patients were analysed according to demographic and clinical variables, as well as in terms of radiological measurements at disease onset and during the first 12 months of follow-up. These measurements included normalised total brain volume (NTBV), normalised cortical volume (NCV), normalised white matter volume, left and right hippocampus, the thalamus, brain stem volume, lesion load and percentage brain volume change. A linear regression model was used to analyse the data.

RESULTS

A total of 97 patients were included: 53 in Group 1 (27 females) and 44 in Group 2 (22 females). In Group 1, we observed a reduction in brain volume in males compared with females at disease onset in NTBV (p = 0.01), NCV (p = 0.001) and brain stem volume (p = 0.01). We did not observe differences in Group 2 at disease onset in the brain volumes analysed.

CONCLUSION

We observed structural sex differences in brain volume at disease onset in the pre-menopausal group. However, no structural differences were observed at disease onset between the sexes after the menopause had started.

The influence of sex hormones on cytokines in multiple sclerosis and experimental autoimmune encephalomyelitis: a review

The female predominance of multiple sclerosis (MS) has suggested that hormonal differences between the sexes must confer some protective effect on males or enhance the susceptibility of females to this disease. There has been evidence that gonadal hormones can modulate the immune response regulated by antigen presenting cells and T cells. These cells control the immune response by the production of interacting pro- and anti-inflammatory cytokines. The first include the acute phase pro-inflammatory cytokines of the innate immune response as well as the T-helper 1 (Th1) cytokines, while the later contain the Th2 cytokines as well as the suppressor cytokines. There is some evidence that MS and experimental autoimmune encephalitis (EAE) are Th1 cell-mediated diseases. For this reason many studies have been done to influence the pro-inflammatory cytokine production of these Th1 cells in favour of an anti-inflammatory immune response as mediated by Th2 cells. However the role of the regulatory T cells in this context is not clearly understood. Here we review the studies concerning the role of sex hormones on the cytokine production in relation to the disease course of MS and EAE and in particular in the light of the recent revival of the regulatory T cells and their suppressive cytokines.

Sex bias in CNS autoimmune disease mediated by androgen control of autoimmune regulator

Male gender is protective against multiple sclerosis and other T-cell-mediated autoimmune diseases. This protection may be due, in part, to higher androgen levels in males. Androgen binds to the androgen receptor (AR) to regulate gene expression, but how androgen protects against autoimmunity is not well understood. Autoimmune regulator (Aire) prevents autoimmunity by promoting self-antigen expression in medullary thymic epithelial cells, such that developing T cells that recognize these self-antigens within the thymus undergo clonal deletion. Here we show that androgen upregulates Aire-mediated thymic tolerance to protect against autoimmunity. Androgen recruits AR to Aire promoter regions, with consequent enhancement of Aire transcription. In mice and humans, thymic Aire expression is higher in males compared with females. Androgen administration and male gender protect against autoimmunity in a multiple sclerosis mouse model in an Aire-dependent manner. Thus, androgen control of an intrathymic Aire-mediated tolerance mechanism contributes to gender differences in autoimmunity.

The Influence of Dihydrotestosterone on the Development of Graves' Disease in Female BALB/c Mice

BACKGROUND

Graves' disease (GD) is a common organ-specific autoimmune disease characterized by hyperthyroidism that has significant sex differences in prevalence and clinical expressions. Abnormal cytokine production and T cell activation may result in various manifestations of GD. Studies have shown that androgen treatment can provide protection against autoimmune diseases, but the effects of androgen treatment on GD are still unknown. Therefore, this study investigated whether a potent bioactive androgen, 5α-dihydrotestosterone (DHT), could be of benefit in a BALB/c mouse model of GD. The aims of this study were to investigate (i) whether DHT pretreatment inhibits autoimmune responses, and (ii) the mechanism of immune protection of DHT in GD.

METHODS

Female BALB/c mice were immunized three times with an adenovirus expressing the human thyrotropin receptor (TSHR) A-subunit (Ad-TSHR289). Three doses (1.5, 5, and 15 mg) of DHT or a matching placebo were implanted a week before the first immunization. Four weeks after the third immunization, mice were sacrificed, and blood, the spleen, and the thyroid were removed for further analysis.

RESULTS

After DHT treatment, thyroid hormones were dramatically reduced compared with placebo. In addition, a remarkable reduction in interferon-γ and interleukin-2 production was observed in DHT-pretreated mice.

CONCLUSIONS

DHT can alleviate the severity of GD by downregulating pro-autoimmune T helper 1 cells in female BALB/c mice. The protective influence was more noticeable with 5 mg and 15 mg doses of DHT.

Association of Autophagy in the Cell Death Mediated by Dihydrotestosterone in Autoreactive T Cells Independent of Antigenic Stimulation

Gender disparity is well documented in the mouse model of experimental autoimmune encephalomyelitis (EAE) induced with proteolipid protein (PLP) 139-151, in which female, but not male, SJL mice show a chronic relapsing-remitting paralysis. Furthermore, dihydrotestosterone (DHT) has been shown to ameliorate the severity of EAE, but the underlying mechanisms of its protective effects are unclear. Using major histocompatibility complex (MHC) class II dextramers for PLP 139-151, we tested the hypothesis that DHT selectively modulates the expansion and functionalities of antigen-specific T cells. Unexpectedly, we noted that DHT induced cell death in antigen-specific, autoreactive T cells, but the effects were not selective, because both proliferating and non-proliferating cells were equally affected independent of antigenic stimulation. Furthermore, DHT-exposed PLP 139-151-specific T cells did not show any shift in cytokine production; rather, frequencies of cytokine-producing PLP-specific T cells were significantly reduced, irrespective of T helper (Th) 1, Th2, and Th17 subsets of cytokines. By evaluating cell death and autophagy pathways, we provide evidence for the induction of autophagy to be associated with cell death caused by DHT. Taken together, the data provide new insights into the role of DHT and indicate that cell death and autophagy contribute to the therapeutic effects of androgens in autoreactive T cells.

Analytical challenges for measuring steroid responses to stress, neurodegeneration and injury in the central nervous system

Levels of steroids in the adult central nervous system (CNS) show marked changes in response to stress, degenerative disorders and injury. However, their analysis in complex matrices such as fatty brain and spinal cord tissues, and even in plasma, requires accurate and precise analytical methods. Radioimmunoassays (RIA) and enzyme-linked immunosorbent assays, even with prepurification steps, do not provide sufficient specificity, and they are at the origin of many inconsistent results in the literature. The analysis of steroids by mass spectrometric methods has become the gold standard for accurate and sensitive steroid analysis. However, these technologies involve multiple purification steps prone to errors, and they only provide accurate reference values when combined with careful sample workup. In addition, the interpretation of changes in CNS steroid levels is not an easy task because of their multiple sources: the endocrine glands and the local synthesis by neural cells. In the CNS, decreased steroid levels may reflect alterations of their biosynthesis, as observed in the case of chronic stress, post-traumatic stress disorders or depressive episodes. In such cases, return to normalization by administering exogenous hormones or by stimulating their endogenous production may have beneficial effects. On the other hand, increases in CNS steroids in response to acute stress, degenerative processes or injury may be part of endogenous protective or rescue programs, contributing to the resistance of neural cells to stress and insults. The aim of this review is to encourage a more critical reading of the literature reporting steroid measures, and to draw attention to the absolute need for well-validated methods. We discuss reported findings concerning changing steroid levels in the nervous system by insisting on methodological issues. An important message is that even recent mass spectrometric methods have their limits, and they only become reliable tools if combined with careful sample preparation.

Association of sex hormones and glucose metabolism with the severity of multiple sclerosis

PURPOSE/AIM OF THE STUDY

We evaluated possible associations between the severity of multiple sclerosis (MS) and levels of sex hormones as well as biochemical parameters in a sample of ambulatory patients.

MATERIAL AND METHODS

This cross-sectional study recruited 133 adults (52 men, 66 premenopausal and 15 postmenopausal women), with relapsing-remitting MS. Fasting venous blood samples were drawn for biochemical and hormonal evaluation. These parameters were tested for possible associations with MS severity, assessed using the Expanded Disability Status Scale (EDSS)-scores.

RESULTS

Follicle-stimulating hormone correlated with mean EDSS scores (r = -0.369, p = 0.038) in the premenopausal subgroup. However, this association became non-significant in the age-adjusted multivariate analysis (p = 0.141; power = 67%, type α error 0.10). Free androgen exhibited a borderline negative effect on EDSS-scores in the subgroup of men (r = -0.367, p = 0.093), which was lost after adjusting for age and duration of disease (p = 0.192; statistical power = 93%, type α error 0.05). Levels of estradiol tended to affect disability status of postmenopausal women (normal-mild vs. severe impairment: 23.33 ± 11.73pg/mL vs. 14.74 ± 6.30pg/mL, p = 0.095). Levels of sex hormones or indices of glycemic metabolism did not differ between patients presenting with EDSS scores higher or lower than the median value.

CONCLUSION

Sex hormones and indices of glucose metabolism exhibited only a middle effect on EDSS scoring, which was not independent from the presence of confounders like age and duration of MS. The present study highlights the need for additional research, in order to elucidate the role of sex hormones and insulin resistance in the course of MS.