Testosterone is protective in the sexually dimorphic development of arthritis and lung disease in SKG mice

Inflammation dynamically regulates steroid hormone metabolism and action within macrophages in rheumatoid arthritis

RATIONALE

In inflammatory diseases such as rheumatoid arthritis (RA), steroid metabolism is a central component mediating the actions of immuno-modulatory glucocorticoids and sex steroids. However, the regulation and function of cellular steroid metabolism within key leukocyte populations such as macrophages remain poorly defined. In this study, the inflammatory regulation of global steroid metabolism was assessed in RA macrophages.

METHODS

Bulk RNA-seq data from RA synovial macrophages was used to assess transcripts encoding key enzymes in steroid metabolism and signalling. Changes in metabolism were assessed in synovial fluids, correlated to measures of disease activity and functionally validated in primary macrophage cultures.

RESULTS

RNA-seq revealed a unique pattern of differentially expressed genes, including changes in genes encoding the enzymes 11β-HSD1, SRD5A1, AKR1C2 and AKR1C3. These correlated with disease activity, favouring increased glucocorticoid and androgen levels. Synovial fluid 11β-HSD1 activity correlated with local inflammatory mediators (TNFα, IL-6, IL-17), whilst 11β-HSD1, SRD5A1 and AKR1C3 activity correlated with systemic measures of disease and patient pain (ESR, DAS28 ESR, global disease activity). Changes in enzyme activity were evident in inflammatory activated macrophages in vitro and revealed a novel androgen activating role for 11β-HSD1. Together, increased glucocorticoids and androgens were able to suppress inflammation in macrophages and fibroblast-like-synoviocytes.

CONCLUSIONS

This study underscores the significant increase in androgen and glucocorticoid activation within inflammatory polarized macrophages of the synovium, contributing to local suppression of inflammation. The diminished profile of inactive steroid precursors in postmenopausal women may contribute to disturbances in this process, leading to increased disease incidence and severity.

The Expression of the Alpha7 Nicotinic Acetylcholine Receptor and the Effect of Smoking in Curdlan-Administered SKG Mice

Nicotine, an abundant molecule in tobacco, has immunomodulatory effects on inflammatory diseases, primarily due to the activation of alpha7 nicotinic acetylcholine receptor (α7 nAChR). We aim to evaluate the expression of the α7 nAChR+ cells in joint tissue and the effect of smoking on immune cells and peripheral arthritis in curdlan-administered SKG mice, a murine model of spondyloarthropathy (SpA). The SKG mice were injected with curdlan two times at 2-week intervals and were divided into two groups; one exposed to cigarette smoke and the other not exposed. We found that the α7 nAChR+ cells increased in the joint tissue of curdlan-administered SKG mice compared to in the wild type. Furthermore, the peripheral arthritis scores and histological scores for synovial inflammation were lower in smoke-exposed curdlan-administered SKG mice than in mice not exposed to smoke. Immunofluorescence staining of the α7 nAChR+ and IL-17A+ cells was lower in the synovia of smoke-exposed mice than the control mice. The proportions of α7 nAChR+IL-17A+ and α7 nAChR+IL-17A+FOXP3+ cells also decreased in the synovia of smoke-exposed mice compared with the controls. We observed an increase in the α7 nAChR+ cells within the joint tissue of curdlan-administered SKG mice and that cigarette smoke had an influence on both peripheral arthritis and immune cell population, especially α7 nAChR+ cells. Thus, exposure to cigarette smoke after arthritogenic stimuli may have an anti-arthritogenic effect in curdlan-administered SKG mice.

A case-control study for exploring the association of Prakriti with Rheumatoid Arthritis

BACKGROUND

Deha-Prakriti (DP) is a unique contribution of Ayurveda, which distinguishes the population into three main groups viz., Vata, Pitta, and Kapha predominant individuals. Its assessment helps physicians to prescribe a suitable diet, daily regimen, and lifestyle that prevents non-communicable diseases. Amavata (Rheumatoid Arthritis) is a disease that needs personalized management approach.

AIM

To evaluate the association of DP with Amavata (∼Rheumatoid Arthritis).

OBJECTIVE

To evaluate DP-based susceptibility in the manifestation of Amavata vis-à-vis Rheumatoid Arthritis.

METHODOLOGY

A case-control study was conducted from 18.04.2018 to 09.01.2020, involving 150 cases (patients of Amavata), and 150 controls (healthy volunteers), matching in age (between 18 to 50 years), and sex, selected from Jamnagar. CCRAS-PAS for both the groups, Health Assessment proforma of TRISUTRA project CSIR-AYURGENOMICS, were used. Logistic regression analyses were conducted to determine the relationship between DP and Amavata.

RESULTS

The proportion of people with Vata dosha in the case group (53.79%) was substantially higher (P < 0.0001) than in the control group (24.91%). Pitta (39.35%) and Kapha (36.27%) doshas were found to be more prevalent in the control group (P < 0.0001). There was a six-percent rise in the likelihood of developing Amavata with every unit increase in Vata percentage, according to logistic regression analysis.

CONCLUSION

Vata predominant DP has a significant association with Amavata. Vata predominant DP individuals are more susceptible to Amavata than Pitta and Kapha predominant DP individuals.

Testosterone protects mice against zika virus infection and suppresses the inflammatory response in the brain

Testosterone is essential to human growth and development as well as immune regulation. Zika virus (ZIKV), an emerging arbovirus associated with neurological complications including neuroinflammation, can also cause testicular damage and decrease testosterone secretion. However, whether the dysregulation of testosterone plays a role in the process of neuroinflammation during ZIKV pathogenesis is still unclear. In this study, we found that ZIKV infection caused testicular damage and decreased testosterone secretion in male mice, and testosterone supplementation after ZIKV infection reduced their mortality and attenuated the pathological symptoms. Further investigation revealed that testosterone treatment after ZIKV infection alleviated inflammation and nerve injury in the mouse brain. Additionally, reduced CD8⁺ T cell infiltration and interferon-gamma production were observed in brains of testosterone-treated mice. Overall, our results demonstrated that testosterone plays a protective role in ZIKV-infected mice, and thus it can be developed as a potential therapeutic drug against ZIKV infection.

Exome sequencing link mutation in RGPD4 with systemic sclerosis-associated interstitial lung disease and the low level of testosterone—an exploration study

Background

Interstitial lung disease (ILD) is the most common and potentially most devastating manifestation of SSc in pulmonary involvement. However, the mechanism for systemic sclerosis-associated ILD (SSc-ILD) is unclear. This work aims to explore the potential candidates for SSc-ILD upon whole exome sequencing (WES) and attempts to analyze the possible pathogenesis of SSc-ILD from the perspective of the genetic level.

Materials

Variants were confirmed by whole exome sequencing (WES), and SKAT analysis was employed to explore the most differential variants. Targeted variants were performed in biological functions, associated with clinical manifestations, and the probable change of downstream.

Results

By WES and SKAT analysis of SSc with and without ILD, only the variants of RGPD4 achieved statistical power (P < 2.51 × 10^-6, P-FDR = 0.025, OR = 15.95). A total of 20 rare functional variants (missense, truncating, splicing) were tested for the RGPD4 gene, and five truncating and damaging missense variants were identified. Carriers showed the older inclusion age (P = 0.02) and the higher frequency use of prednisone (P=0.02) compared to the non-carriers. Further analysis illustrated that carriers showed lower levels of TES in comparison to non-carriers but did not reach statistical difference (P = 0.08). In bivariate correlation analysis, we analyzed the relationship between the mutant status of RGPD4 and the levels of sex hormones after adjusting for age confounders. Only the level of TES showed a negative correlation with the mutant status (B = -0.509, P = 0.037).

Conclusion

The variants of RGPD4 might contribute to the ILD development of SSc and might also be a causative factor of lower TES among SSc-ILD, which provided insight to a better understanding of pathobiology of SSc-ILD, and androgen hormone supplement might be a therapeutic target in this debilitating disease.

Sex Steroids Effects on Asthma: A Network Perspective of Immune and Airway Cells

A multitude of evidence has suggested the differential incidence, prevalence and severity of asthma between males and females. A compilation of recent literature recognized sex differences as a significant non-modifiable risk factor in asthma pathogenesis. Understanding the cellular and mechanistic basis of sex differences remains complex and the pivotal point of this ever elusive quest, which remains to be clarified in the current scenario. Sex steroids are an integral part of human development and evolution while also playing a critical role in the conditioning of the immune system and thereby influencing the function of peripheral organs. Classical perspectives suggest a pre-defined effect of sex steroids, generalizing estrogens popularly under the “estrogen paradox” due to conflicting reports associating estrogen with a pro- and anti-inflammatory role. On the other hand, androgens are classified as “anti-inflammatory,” serving a protective role in mitigating inflammation. Although considered mainstream and simplistic, this observation remains valid for numerous reasons, as elaborated in the current review. Women appear immune-favored with stronger and more responsive immune elements than men. However, the remarkable female predominance of diverse autoimmune and allergic diseases contradicts this observation suggesting that hormonal differences between the sexes might modulate the normal and dysfunctional regulation of the immune system. This review illustrates the potential relationship between key elements of the immune cell system and their interplay with sex steroids, relevant to structural cells in the pathophysiology of asthma and many other lung diseases. Here, we discuss established and emerging paradigms in the clarification of observed sex differences in asthma in the context of the immune system, which will deepen our understanding of asthma etiopathology.

Recent Advances in Basic and Clinical Aspects of Rheumatoid Arthritis-associated Interstitial Lung Diseases

Rheumatoid arthritis (RA) is a common autoimmune disease that mainly affects the joints and systemic organs, such as the skin, eyes, heart, gastrointestinal tract, and lungs. In particular, among various pulmonary involvements, interstitial lung disease (ILD) is closely related to the selection of anti-rheumatic drugs and the long-term prognosis of patients with RA. Although the exact pathogenesis of RA-ILD is not well defined, several mechanistic pathways, similar to those of idiopathic pulmonary fibrosis, have been elucidated recently. Conversely, RA-related autoantibodies, including anti-cyclic citrullinated peptide antibody, are detectable in circulation and in the lungs, even in the absence of articular symptoms. RA-ILD can also predate years before the occurrence of joint symptoms. This evidence supports the fact that local dysregulated mucosal immunity in the lung causes systemic autoimmunity, resulting in clinically evident polyarthritis of RA. Because the early diagnosis of RA-ILD is important, imaging tests, such as computed tomography and pulmonary function tests, are being used for early diagnosis, but there is no clear guideline for the early diagnosis of RA-ILD and selection of optimal disease-modifying anti-rheumatic drugs for the treatment of patients with RA with ILD. In addition, the efficacy of nintedanib, a new anti-fibrotic agent, for RA-ILD treatment, has been investigated recently. This review collectively discusses the basic and clinical aspects, such as pathogenesis, animal models, diagnosis, and treatment, of RA-ILD.

A systematic review exploring the bidirectional relationship between puberty and autoimmune rheumatic diseases

BACKGROUND

Autoimmune rheumatic diseases (ARDs) are associated with a significant sex-bias, which becomes more evident post-puberty. This systematic review aims to elucidate the bidirectional relationship between puberty and ARD-related outcomes.

METHODS

Studies published in English until October 2019 were identified using a systematic search of endocrinology and rheumatology literature. Information was extracted on study design, sample size, demographics, puberty outcome measures, disease outcome measures, and main findings. The methodological quality of the studies included was analysed using the Newcastle-Ottawa Scale (NOS).

RESULTS

Sixteen non-randomised studies reporting on the impact of puberty on ARD outcomes (n = 7), ARD impact on puberty-related outcomes (n = 8), or both (n = 1) have been identified. The impact of puberty on ARD outcomes were investigated in patients with juvenile idiopathic arthritis (JIA)-associated uveitis (n = 1), juvenile systemic lupus erythematosus (JSLE) (n = 5) or in healthy controls who developed adult-onset SLE (n = 1) or had non-specific symptoms (n = 1). The impact of ARD on puberty outcomes was explored in JIA (n = 4) and JSLE (n = 3). Quality assessment of studies showed a small to moderate risk of bias overall (NOS 4-9/9). Due to large heterogeneity of the studies it was not possible to perform a meta-analysis. Multiple studies reported on delayed puberty in patients with JIA/JSLE, menstrual and hormonal abnormalities, and lower height and weight than controls. Earlier (pre-pubertal) onset of JSLE was correlated with more severe disease and more need for systemic treatment.

CONCLUSION

A bidirectional relationship exists between puberty and ARDs; however, more and better research is required to elucidate the complexity of this relationship. We propose puberty-related clinical assessments in patients with ARDs, which can improve patient outcomes and facilitate future research.

Animal models of rheumatoid arthritis-associated interstitial lung disease

BACKGROUND

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is an irreversible pathologic condition of unknown cause, commonly involving the joint and the lung with variable amounts of fibrotic change. In contrast to rheumatoid arthritis or other chronic interstitial lung diseases such as interstitial pulmonary fibrosis, there is so far no extensively accepted or implemented animal model for this disease.

AIMS

To provide guidance for those who are investigating the pathogenesis of RA-ILD with animal models.

MATERIALS AND METHODS

An analysis of papers from PubMed during 1978-2020.

RESULTS

We outline the present status quo for animal models of RA-ILD about their modeling methods and pathogenesis, compare their pros and cons with respect to their ability to mimic the clinical and histological features of human disease and discuss their applicability for future research.

DISCUSSION

There is no doubt that these animal models do provide valuable information relating to the pathogenesis of RA-ILD and the development of effective therapeutic drugs. Nevertheless, these animal models can not entirely recapitulate clinical pathology and have some limitations in experimental research application. Therefore, it should be emphasized that we should improve and explore animal models in more accordance with the pathogenesis and clinical characteristics of human RA-ILD.

CONCLUSION

These established animal models of the disease can significantly progress our understanding of the etiology of RA-ILD, the fundamental mechanisms of its pathogenesis and the identification of new bio-markers, and can contribute to the development and implementation of novel treatment strategies.

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.

The Effects of Androgens on T Cells: Clues to Female Predominance in Autoimmune Liver Diseases?

The immune system responds differently in women and in men. Generally speaking, adult females show stronger innate and adaptive immune responses than males. This results in lower risk of developing most of the infectious diseases and a better ability to clear viral infection in women (1–5). On the other hand, women are at increased risk of developing autoimmune diseases (AID) such as rheumatoid arthritis, multiple sclerosis (MS), systemic lupus erythematosus (SLE), Sjögren's syndrome, and the autoimmune liver diseases autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) (6). Factors contributing to the female sex bias in autoimmune diseases include environmental exposure, e.g., microbiome, behavior, and genetics including X chromosomal inactivation of genes. Several lines of evidence and clinical observations clearly indicate that sex hormones contribute significantly to disease pathogenesis, and the role of estrogen in autoimmune diseases has been extensively studied. In many of these diseases, including the autoimmune liver diseases, T cells are thought to play an important pathogenetic role. We will use this mini-review to focus on the effects of androgens on T cells and how the two major androgens, testosterone and dihydrotestosterone, potentially contribute to the pathogenesis of autoimmune liver diseases (AILD).

Effects of dihydrotestosterone on osteoblast activity in curdlan-administered SKG mice and osteoprogenitor cells in patients with ankylosing spondylitis

Background

Ankylosing spondylitis (AS) is characteristically male-predominant, and progressive spinal ankylosis affects male patients more severely; however, the hormonal effects in males with AS are poorly understood.

Methods

In the present study, the regulatory effects of dutasteride, a 5-α reductase inhibitor that blocks the conversion of testosterone to dihydrotestosterone (DHT), were examined in curdlan-administered male SKG mice to determine spinal bone formation, bone metabolism-related markers, and interleukin (IL)-17A cytokine and T cell populations. In addition, the effects of DHT on primary osteoprogenitors from the facet joints of AS patients were assessed based on osteoblast-related parameters. DHT level was measured, and the correlation with modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) was analyzed in AS patients.

Results

In curdlan-administered SKG mice, dutasteride treatment resulted in an increased accumulation of hydroxyapatite in the spine which was positively correlated with serum IL-17A levels. In the analysis of bone metabolism-related molecules, a decrease in sclerostin levels was observed in the sera in the dutasteride group. Continuous exposure to DHT resulted in fewer calcium deposits in AS osteoprogenitors during osteoblast differentiation. DHT-treated AS osteoprogenitors showed decreased osteocalcin and increased DKK1 and SOST1 mRNA expression, supporting the results of the in vivo experiments. Treatment with dutasteride upregulated bone formation in the spine of curdlan-administered SKG mice and DHT treatment downregulated osteoblast differentiation in vitro.

Conclusions

Treatment with dutasteride affected the bone formation in the spine of curdlan-treated SKG mice, and DHT treatment attenuated osteoblast differentiation in vitro. Therefore, contrary to what could be expected if osteoblasts contributed to spinal ankylosis, DHT inhibition might increase rather than decrease the progression of spinal ankylosis despite the higher levels of DHT observed in many AS patients.

Y chromosome loss is associated with age-related male patients with abdominal aortic aneurysms

Purpose

Abdominal aortic aneurysm (AAA) demonstrates many features of autoimmune diseases. Y chromosome, sex-determining region of the Y chromosome (SRY) gene, androgen receptor (AR) gene, and androgen appear as potential candidates for influence of the male immune function. This study investigated Y chromosome numbers, SRY gene, AR gene, and androgen levels in male AAAs. We also investigated the correlation between Y chromosome loss (LOY) ratio, SRY expression, androgen levels, and age.

Patients and methods

We investigated LOY by fluorescence in situ hybridization (FISH) in 37 AAAs and compared with 12 patients with abdominal aortic atherosclerotic occlusive disease (AOD) and 91 healthy controls (HC). We investigated SRY and AR expression at mRNA level by real-time PCR in peripheral T lymphocytes in AAA compared with AOD and HC, and AR protein levels by immunohistochemistry (IHC) in AAA. LOY, SRY expression, androgen levels, and age were examined for correlations using the Spearman’s rank correlation coefficient.

Results

LOY ratio in peripheral T lymphocytes was significantly higher in the AAA group compared with the HC (9.11% vs 5.56%, P<0.001) and AOD groups (9.11% vs 6.42%, P=0.029). The SRY mRNA expression in peripheral T lymphocytes was 4.7-fold lower expressed in the AAA group than in the HC group (P<0.001). Free plasma testosterone levels were lower in the AAA group compared with the HC group (P=0.036), whereas sex hormone-binding globulin levels were higher (P=0.020). LOY ratio and expression of SRY mRNA level increased with age in the AAA group (R=0.402 and, R=0.366, respectively). A significant correlation between AR mRNA level (R=0.692) and aortic diameter was detected. Simultaneously, in AAA tissue, the rate of LOY increased with age (R=0.547) and also positively associated with LOY in peripheral blood T lymphocytes (R=0.661).

Conclusion

This study identified a prominent Y chromosome loss in male AAAs, which is correlated to age, lower level of SRY expression and free testosterone, providing a new clue for the mechanisms of AAA.

Selective Sexual Dimorphisms in Musculoskeletal and Cardiopulmonary Pathologic Manifestations and Mortality Incidence in the Tumor Necrosis Factor-Transgenic Mouse Model of Rheumatoid Arthritis

OBJECTIVE

To examine and quantify the sexual dimorphism in pathologic features manifested in the musculoskeletal and cardiopulmonary systems and incidence of mortality in the tumor necrosis factor-transgenic (TNF-Tg; Tg3647 strain) mouse model of inflammatory erosive arthritis.

METHODS

Kaplan-Meier survival estimates were determined in male and female Tg3647 mice and sex-matched wild-type (WT) littermate mice. Longitudinal and cross-sectional pathologic outcomes in the musculoskeletal and cardiopulmonary systems were assessed via ultrasound, micro-computed tomography, grip strength measurements, histologic and serologic analyses, flow cytometry, and skeletal muscle physiologic measures.

RESULTS

Compared to male Tg3647 mice (n = 30), female Tg3647 mice (n = 34) had significantly shorter lifespans (P < 0.001) and exhibited the following pathologic features (n = 4-6 per group; P < 0.05 versus male Tg3647 littermates): gross deficits in body mass and muscle weight, early-onset inflammatory arthritis with severity of end-stage arthritis that was as severe as that seen in male transgenic mice, and early onset and increased severity of inflammatory interstitial lung disease (ILD). Histologically, the ILD observed in Tg3647 mice was characterized by inflammatory cell accumulation and pulmonary arteriole thickening, which was concomitant with the presence of right ventricular hypertrophy, a feature that was also more severe in the female compared to male Tg3647 mice (P < 0.05). No sexual dimorphisms in TNF-induced deficient grip strength, axial skeletal growth, or bone loss were found. Globally, the extent of the pathologic changes observed in female Tg3647 mice was greater than that observed in male Tg3647 mice when each group was compared to their sex-matched WT littermates.

CONCLUSION

These findings indicate that TNF selectively drives the early onset of arthritis and progression of pathologic changes in the cardiopulmonary system in female Tg3647 mice. These results in the Tg3647 mouse identify it as a suitable model to better understand the mechanisms underlying sexual dimorphism and cardiopulmonary disease in the setting of inflammatory arthritis and other connective tissue diseases.

In search of new paradigms for epididymal health and disease: innate immunity, inflammatory mediators, and steroid hormones

The primary job of the epididymis is to mature and protect the luminally transiting spermatozoa. Mounting evidence is showing that innate immune components [including Toll-like receptors (TLRs) and antimicrobial proteins, among which are β-defensins] and inflammatory mediators, under the primary influence of androgens, participate in the cellular and molecular processes that define this tissue. Here, we present an overview of the contributions of these signaling pathway components during epididymal homeostasis and discuss the hypotheses as to their involvement in epididymitis, the most common urological inflammatory condition in men, frequently impairing their fertility. Drawing primarily from rodent models, we also focus on how the distribution and functional expression of innate immune components are differentially regulated in the prenatal developing epididymis, providing new insights into the disruption of these signaling pathways throughout the lifespan. Male infertility is caused by a variety of conditions, such as congenital malformations, genetic and endocrine disorders, exposure to environmental toxicants, and inflammatory/infectious conditions. More than one-third of infertile men with an idiopathic condition cannot currently be adequately diagnosed. Thinking about the innate immunity and inflammation context of the epididymis may provide new insights and directions as to how these systems contribute to male fertility, as well as also uncover urological and andrological outcomes that may aid clinicians in diagnosing and preventing epididymal pathologies.

Nod2 Deficiency Augments Th17 Responses and Exacerbates Autoimmune Arthritis

Arthritis in a genetically susceptible SKG strain of mice models a theoretical paradigm wherein autoimmune arthritis arises because of interplay between preexisting autoreactive T cells and environmental stimuli. SKG mice have a point mutation in ZAP-70 that results in attenuated TCR signaling, altered thymic selection, and spontaneous production of autoreactive T cells that cause arthritis following exposure to microbial β-glucans. In this study, we identify Nod2, an innate immune receptor, as a critical suppressor of arthritis in SKG mice. SKG mice deficient in Nod2 (Nod2^-/-SKG) developed a dramatically exacerbated form of arthritis, which was independent of sex and microbiota, but required the skg mutation in T cells. Worsened arthritis in Nod2^-/-SKG mice was accompanied by expansion of Th17 cells, which to some measure coproduced TNF, GM-CSF, and IL-22, along with elevated IL-17A levels within joint synovial fluid. Importantly, neutralization of IL-17A mitigated arthritis in Nod2^-/-SKG mice, indicating that Nod2-mediated protection occurs through suppression of the Th17 response. Nod2 deficiency did not alter regulatory T cell development or function. Instead, Nod2 deficiency resulted in an enhanced fundamental ability of SKG CD4⁺ T cells (from naive mice) to produce increased levels of IL-17 and to passively transfer arthritis to lymphopenic recipients on a single-cell level. These data reveal a previously unconsidered role for T cell-intrinsic Nod2 as an endogenous negative regulator of Th17 responses and arthritogenic T cells. Based on our findings, future studies aimed at understanding a negative regulatory function of Nod2 within autoreactive T cells could provide novel therapeutic strategies for treatment of patients with arthritis.

Nintedanib reduces pulmonary fibrosis in a model of rheumatoid arthritis-associated interstitial lung disease

Rheumatoid arthritis (RA)-associated interstitial lung disease (RA-ILD) develops in ~20% of patients with RA. SKG mice, which are genetically prone to development of autoimmune arthritis, develop a pulmonary interstitial pneumonia that resembles human cellular and fibrotic nonspecific interstitial pneumonia. Nintedanib, a tyrosine kinase inhibitor approved for treatment of idiopathic pulmonary fibrosis, has been shown to reduce the decline in lung function. Therefore, we investigated the effect of nintedanib on development of pulmonary fibrosis and joint disease in female SKG mice with arthritis induced by intraperitoneal injection of zymosan (5 mg). Nintedanib (60 mg·kg-1·day-1 via oral gavage) was started 5 or 10 wk after injection of zymosan. Arthritis and lung fibrosis outcome measures were assessed after 6 wk of treatment with nintedanib. A significant reduction in lung collagen levels, determined by measuring hydroxyproline levels and staining for collagen, was observed after 6 wk in nintedanib-treated mice with established arthritis and lung disease. Early intervention with nintedanib significantly reduced development of arthritis based on joint assessment and high-resolution μ-CT. This study impacts the RA and ILD fields by facilitating identification of a therapeutic treatment that may improve both diseases. As this model replicates the characteristics of RA-ILD, the results may be translatable to the human disease.

Testosterone is an endogenous regulator of BAFF and splenic B cell number

Testosterone deficiency in men is associated with increased risk for autoimmunity and increased B cell numbers through unknown mechanisms. Here we show that testosterone regulates the cytokine BAFF, an essential survival factor for B cells. Male mice lacking the androgen receptor have increased splenic B cell numbers, serum BAFF levels and splenic Baff mRNA. Testosterone deficiency by castration causes expansion of BAFF-producing fibroblastic reticular cells (FRCs) in spleen, which may be coupled to lower splenic noradrenaline levels in castrated males, as an α-adrenergic agonist decreases splenic FRC number in vitro. Antibody-mediated blockade of the BAFF receptor or treatment with the neurotoxin 6-hydroxydopamine revert the increased splenic B cell numbers induced by castration. Among healthy men, serum BAFF levels are higher in men with low testosterone. Our study uncovers a previously unrecognized regulation of BAFF by testosterone and raises important questions about BAFF in testosterone-mediated protection against autoimmunity.

Testosterone deficiency is associated with autoimmunity and increased B cell numbers, but the underlying mechanism is unclear. Here the authors show that testosterone may modulate the production of B cell survival factor BAFF by fibroblastic reticular cells via regulation of splenic neurotransmitter levels.

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.

Rheumatoid arthritis onset in postmenopausal women: Does the ACPA seropositive subset result from genetic effects, estrogen deficiency, skewed profile of CD4(+) T-cells, and their interactions?

Rheumatoid arthritis (RA) incidence displays a differentiated age-dependent female-to-male ratio in which women outnumber men. Evidence that the peak incidence of RA in women coincides with menopause age, suggests a potential estrogenic role to disease etiology. Estrogens exert physiologically both stimulatory and inhibitory effects on the immune system. Epidemiologic and animal model studies with estrogen deprivation or supplementation suggested estrogens as to play, mainly, a protective role in RA immunopathology. In this review, we propose that some yet unidentified disturbances associated with estrogen circulating levels, differentiated by the menopausal status, play a major role in women's RA susceptibility. We focus on the interaction between estrogen deprivation and genetic risk alleles for anti-citrullinated protein antibodies (ACPA) seropositive RA, as a major driving force for increased immune reactivity and RA susceptibility, in postmenopausal women. This opens up new fields for research concerning the association among different irregular estrogenic conditions, the cytokine milieu, and age/menopausal status bias in RA.

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.

Investigation of the relationship between the onset of arthritis and uveitis in genetically predisposed SKG mice

Introduction

Systemic rheumatic conditions are often accompanied by intraocular inflammatory disease (termed uveitis). Despite the frequent manifestation of uveitis with arthritis, very little is understood of the underlying mechanisms that mediate the eye’s susceptibility to disease. The genetically susceptible SKG mouse strain develops arthritis that arises from an inherent mutation that disrupts T-cell antigen receptor signal transduction and thymic selection. The ensuing T-cell–mediated disease is further modulated through exposure to microbial triggers. The purpose of this study was to elucidate how a genetically determined shift in the T-cell repertoire toward self-reactive T cells that drive arthritis influences uveitis in SKG mice.

Methods

SKG mice (BALB/c mice that harbor the W163C point mutation in zeta-chain-associated protein kinase 70 [i.e., ZAP-70]) were housed under arthritis-resistant, specific pathogen–free conditions. Arthritis was induced by intraperitoneal injection with fungal glucans (zymosan or curdlan). Arthritis onset and severity were evaluated by clinical scoring, histopathology and infrared imaging within the joints. Periocular traits involving blepharoconjunctivitis were evaluated by clinical scoring and histology. Eyes were evaluated for signs of anterior uveitis using intravital videomicroscopy to document cell-trafficking responses within the iris vasculature and stroma and by histology to detect inflammatory infiltrate and tissue damage within the anterior and posterior eye segments.

Results

Exposure to zymosan resulted in the predicted arthritic, sexually dimorphic phenotype in SKG mice. The eyes of SKG mice exhibited episodic intravascular cellular responses to zymosan or curdlan as indicated by significant increases in leukocyte–endothelium interactions akin to ocular vasculitis. However, despite the significant increase in early cell-trafficking responses, cellular infiltration into the iris stroma was not observed and histopathological signs indicative of a sustained uveitis were absent. Instead, eyes of SKG mice developed blepharoconjunctivitis that coincided with arthritis and exhibited sexual dimorphism.

Conclusions

This study underscores the complexity surrounding the pathogenesis of uveitis and its relationship with arthritis. The findings suggest that distinct mechanisms exist by which pathogenic autoimmune T cells target the eyes versus joints, which likely involves the environmental context but nonetheless should be taken into account in the identification and development of effective therapies for each organ.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0725-z) contains supplementary material, which is available to authorized users.

Sexual dimorphism in autoimmunity

Autoimmune diseases occur when the immune system attacks and destroys the organs and tissues of its own host. Autoimmunity is the third most common type of disease in the United States. Because there is no cure for autoimmunity, it is extremely important to study the mechanisms that trigger these diseases. Most autoimmune diseases predominantly affect females, indicating a strong sex bias. Various factors, including sex hormones, the presence or absence of a second X chromosome, and sex-specific gut microbiota can influence gene expression in a sex-specific way. These changes in gene expression may, in turn, lead to susceptibility or protection from autoimmunity, creating a sex bias for autoimmune diseases. In this Review we discuss recent findings in the field of sex-dependent regulation of gene expression and autoimmunity.

Animal models of rheumatoid arthritis: How informative are they?

Animal models of arthritis are widely used to de-convolute disease pathways and to identify novel drug targets and therapeutic approaches. However, the high attrition rates of drugs in Phase II/III rates means that a relatively small number of drugs reach the market, despite showing efficacy in pre-clinical models. There is also increasing awareness of the ethical issues surrounding the use of animal models of disease and it is timely, therefore, to review the relevance and translatability of animal models of arthritis. In this paper we review the most commonly used animal models in terms of their pathological similarities to human rheumatoid arthritis as well as their response to drug therapy. In general, the ability of animal models to predict efficacy of biologics in man has been good. However, the predictive power of animal models for small molecules has been variable, probably because of differences in the levels of target knockdown achievable in vivo.

Suppressive effects of androgens on the immune system

Sex-based disparities in immune responses are well known phenomena. The two most important factors accounting for the sex-bias in immunity are genetics and sex hormones. Effects of female sex hormones, estrogen and progesterone are well established, however the role of testosterone is not completely understood. Evidence from unrelated studies points to an immunosuppressive role of testosterone on different components of the immune system, but the underlying molecular mechanisms remains unknown. In this review we evaluate the effect of testosterone on key cellular components of innate and adaptive immunity. Specifically, we highlight the importance of testosterone in down-regulating the systemic immune response by cell type specific effects in the context of immunological disorders. Further studies are required to elucidate the molecular mechanisms of testosterone-induced immunosuppression, leading the way to the identification of novel therapeutic targets for immune disorders.

The lung may play a role in the pathogenesis of rheumatoid arthritis

Multiple studies have identified strong associations between the lung and rheumatoid arthritis (RA). Such studies identify a high prevalence of lung disease, both airways and parenchymal disease, in subjects with clinically classifiable RA. It has been suggested that lung disease in RA results from targeting of the lung from circulating autoimmunity or other factors such as medications. However, findings that lung disease, specifically inflammatory airways disease, and lung generation of autoimmunity can be present before the onset of joint symptoms suggest that immune reactions in the lung may be involved in the initial development of RA-related autoimmunity. Herein we review these issues in detail, as well as outline a potential research agenda to understand the natural history of lung involvement in RA and its relation to the overall pathogenesis of RA.