Emerging Insights Into the Role of Epigenetics and Gut Microbiome in the Pathogenesis of Graves’ Ophthalmopathy

Graves’ Ophthalmopathy (GO) is an organ-specific autoimmune disease that is often characterized by infiltration of orbital tissues and is considered as the most common extra-thyroid manifestation of Graves’ disease (GD). Although genetic susceptibility has been found to be critical for the phenotype of GO, the associated risk alleles in a single gene are generally insufficient to cause the disease. Accruing evidence has shown that epigenetic disorders can act as the potentially missing link between genetic risk and clinically significant disease development. Abnormal epigenetic modifications can lead to pro-inflammatory cascades and activation of orbital fibroblasts (OFs) by promoting the various inflammatory response pathways and regulating the diverse signaling molecules that are involved in the fibrogenesis and adipogenesis, thereby leading to the significant expansion of orbital tissues, fibrosis and inflammation infiltration. Additionally, emerging evidence has shown that the gut microbiome can possibly drive the pathogenesis of GO by influencing the secretion of Thyrotropin receptor antibody (TRAb) and T-helper 17 (Th17)/regulatory T cells (Treg) imbalance. This paper describes the latest epigenetic research evidence and progress made in comprehending the mechanisms of GO development, such as DNA methylation, histone modification, non-coding RNAs, and the gut microbiome.

Stress-Induced Despair Behavior Develops Independently of the AHR-RORgt Axis in CD4+ cells

Current treatments for major depressive disorder are limited to neuropharmacological approaches and are ineffective for large numbers of patients. Recently, alternative means have been explored to understand the etiology of depression. Specifically, changes in the microbiome and immune system have been observed in both clinical settings and in mouse models. As such, microbial supplements and probiotics have become a target for potential therapeutics. A current hypothesis for the mechanism of action of these supplements is via the aryl hydrocarbon receptor’s (AHR) modulation of the T helper 17 cell (Th17) and T regulatory cell axis. As inflammatory RORgt+ CD4+ Th17 T cells and their primary cytokine IL-17 have been implicated in the development of stress-induced depression, the connection between stress, the AHR, Th17s and depression remains critical to disease understanding. Here, we utilize genetic knockouts to examine the role of the microbial sensor AHR in the development of stress induced despair behavior. We observe an AHR-independent increase in gut-associated Th17s in stressed mice, indicating that AHR is not responsible for this communication. Further, we utilized a CD4-specific Rorc knockout line to disrupt the production of Th17s. Mice lacking Rorc induced IL-17 did not show any differences in behavior from controls before or after stress. Finally, we utilize an unsupervised machine learning system to examine minute differences in behavior that could not be observed in traditional behavioral assays. Our data demonstrate that neither CD4 specific Ahr nor Rorc are necessary for the development of stress-induced anxiety-or depressive-like behaviors. These data suggest that research approaches should focus on other sources or sites of IL-17 production in stress-induced depression.

Gut Microbiota as Regulators of Th17/Treg Balance in Patients With Myasthenia Gravis

Myasthenia gravis (MG) is an acquired neurological autoimmune disorder characterized by dysfunctional transmission at the neuromuscular junction, with its etiology associated with genetic and environmental factors. Anti-inflammatory regulatory T cells (Tregs) and pro-inflammatory T helper 17 (Th17) cells functionally antagonize each other, and the immune imbalance between them contributes to the pathogenesis of MG. Among the numerous factors influencing the balance of Th17/Treg cells, the gut microbiota have received attention from scholars. Gut microbial dysbiosis and altered microbial metabolites have been seen in patients with MG. Therefore, correcting Th17/Treg imbalances may be a novel therapeutic approach to MG by modifying the gut microbiota. In this review, we initially review the association between Treg/Th17 and the occurrence of MG and subsequently focus on recent findings on alterations of gut microbiota and microbial metabolites in patients with MG. We also explore the effects of gut microbiota on Th17/Treg balance in patients with MG, which may provide a new direction for the prevention and treatment of this disease.

Mechanism of miR-181a-5p in Regulatory T/T-Helper 17 Immune Imbalance and Asthma Development in Mice with Allergic Rhinitis

<b><i>Introduction:</i></b> Allergic rhinitis (AR) is an immune disorder and also a risk factor of asthma. microRNAs (miRNAs) are implicated in autoimmune diseases, including RA. This study investigated effect of miR-181a-5p on regulatory T (Treg)/ T-helper (Th) 17 immune imbalance in AR. <b><i>Methods:</i></b> A murine model of AR was established and treated with lentivirus modified miR-181a-5p. The allergic symptoms of mice were examined. The contents of Th17-related cytokines (interferon [IFN]-γ and interleukin [IL]-6), Treg-related cytokine (IL-10), and Treg-specific nuclear transcription factor (Foxp3) in nasal mucosa and lung tissues were determined. The proportion of Treg and Th17 cells was analyzed by flow cytometry. The level of ovalbumin-specific immunoglobulin E in the serum, and the contents of IL-4, IL-5, and IL-13 in bronchoalveolar lavage fluid and IFN-γ, IL-6, and IL-10 in nasal lavage fluid were measured. The targeting relationship between miR-181a-5p and high mobility group box chromosomal protein 1 (HMGB1) was verified. HMGB1 and receptor for advanced glycation end products (RAGE) expression in RA were determined, and the interaction between HMGB1 and RAGE was detected. <b><i>Results:</i></b> miR-181a-5p expression was reduced in AR mice. miR-181a-5p overexpression attenuated allergic behaviors, alleviated Treg/Th17 imbalance, and delayed asthma development. HMGB1 and RAGE were elevated in AR mice. miR-181a-5p targeted HMGB1, and HMGB1 bound to RAGE, while miR-181a-5p overexpression reduced the binding between them. Activating HMGB1/RAGE reversed the protective effect of miR-181a-5p overexpression on AR and induced the development of asthma. <b><i>Conclusion:</i></b> miR-181a-5p overexpression reduced the binding of HMGB1 and RAGE by inhibiting HMGB1, thus alleviating Treg/Th17 immune imbalance and blocking AR from developing into asthma.

The Role of the Microbiota in Graves’ Disease and Graves’ Orbitopathy

Graves‘ disease (GD) is a clinical syndrome with an enlarged and overactive thyroid gland, an accelerated heart rate, Graves’ orbitopathy (GO), and pretibial myxedema (PTM). GO is the most common extrathyroidal complication of GD. GD/GO has a significant negative impact on the quality of life. GD is the most common systemic autoimmune disorder, mediated by autoantibodies to the thyroid-stimulating hormone receptor (TSHR). It is generally accepted that GD/GO results from complex interactions between genetic and environmental factors that lead to the loss of immune tolerance to thyroid antigens. However, the exact mechanism is still elusive. Systematic investigations into GD/GO animal models and clinical patients have provided important new insight into these disorders during the past 4 years. These studies suggested that gut microbiota may play an essential role in the pathogenesis of GD/GO. Antibiotic vancomycin can reduce disease severity, but fecal material transfer (FMT) from GD/GO patients exaggerates the disease in GD/GO mouse models. There are significant differences in microbiota composition between GD/GO patients and healthy controls. Lactobacillus, Prevotella, and Veillonella often increase in GD patients. The commonly used therapeutic agents for GD/GO can also affect the gut microbiota. Antigenic mimicry and the imbalance of T helper 17 cells (Th17)/regulatory T cells (Tregs) are the primary mechanisms proposed for dysbiosis in GD/GO. Interventions including antibiotics, probiotics, and diet modification that modulate the gut microbiota have been actively investigated in preclinical models and, to some extent, in clinical settings, such as probiotics (Bifidobacterium longum) and selenium supplements. Future studies will reveal molecular pathways linking gut and thyroid functions and how they impact orbital autoimmunity. Microbiota-targeting therapeutics will likely be an essential strategy in managing GD/GO in the coming years.

Tetramerization of STAT5 promotes autoimmune-mediated neuroinflammation

Signal tranducer and activator of transcription 5 (STAT5) plays a critical role in mediating cellular responses following cytokine stimulation. STAT proteins critically signal via the formation of dimers, but additionally, STAT tetramers serve key biological roles, and we previously reported their importance in T and natural killer (NK) cell biology. However, the role of STAT5 tetramerization in autoimmune-mediated neuroinflammation has not been investigated. Using the STAT5 tetramer-deficient Stat5a-Stat5b N-domain double knockin (DKI) mouse strain, we report here that STAT5 tetramers promote the pathogenesis of experimental autoimmune encephalomyelitis (EAE). The mild EAE phenotype observed in DKI mice correlates with the impaired extravasation of pathogenic T-helper 17 (Th17) cells and interactions between Th17 cells and monocyte-derived cells (MDCs) in the meninges. We further demonstrate that granulocyte-macrophage colony-stimulating factor (GM-CSF)–mediated STAT5 tetramerization regulates the production of CCL17 by MDCs. Importantly, CCL17 can partially restore the pathogenicity of DKI Th17 cells, and this is dependent on the activity of the integrin VLA-4. Thus, our study reveals a GM-CSF-STAT5 tetramer-CCL17 pathway in MDCs that promotes autoimmune neuroinflammation.

Effects of IL-17 on Epidermal Development

Immunotherapies targeting interleukin 17 (IL-17) have a strong effect on plaque psoriasis. However, many previous studies on IL-17 focused only on the T-helper 17 (Th17) immune response, and a few studies have reported that IL-17A may affect psoriatic epidermal structure. IL-17 includes six family members, namely IL-17A–F, which are involved in a wide variety of biological responses. IL-17A is produced mainly by Th17 cells or group 3 innate lymphoid cells (ILC3), while IL-17C is locally produced by epithelial cells, such as keratinocytes. In contrast to IL-17C, which is locally produced in various cells such as keratinocytes, it is predicted that IL-17A, which is produced by limited cells and has systemic effects, has different roles in epidermal development. For example, several research studies have shown that IL-17A affects terminal differentiation of epidermis by suppressing the expression of filaggrin or loricrin in keratinocytes. On the other hand, IL-17C, which is produced by keratinocytes themselves, does not have as strong as an effect on epidermal development as IL-17A. In this chapter, we summarized the effects of IL-17A and other IL-17 members on epidermal development and their comprehensive roles based on previously reported papers.

Decrease in Regulatory T-cells and Increase in T Helper 17 Cells in Women With Recurrent Spontaneous Abortion

BackgroundAppearance of improper immune responses against the fetus and/or inadequate immunoregulatory mechanisms during pregnancy may lead to recurrent spontaneous abortion (RSA). TH17 cells play a significant role in inducing inflammation, autoimmune disease, and acute transplant rejection, while regulatory T (Treg) cells moderate the function of immune system in order to retain homeostasis.MethodsThis case-control study was designed to evaluate TH17 as well as Treg cells in 25 women with RSA and 25 age-matched healthy non-pregnant women. Flow cytometric assay was performed using monoclonal antibodies to detect CD4+CD25+ Treg cells (CD25dim and CD25bright). FoxP3 and RORγt expressions were compared using real-time PCR, and pro-inflammatory and anti-inflammatory cytokines were measured by ELISA kits. Independent-samples T test was employed for statistical analysis. ResultsThe ratio of CD4+CD25bright T cells was remarkably lower in women with RSA (P<0.05), and CD4+CD25dim T cells did not show any significant difference among the groups (P>0.05). RORγt was up-regulated, and FoxP3 was down-regulated significantly in case group (P<0.05). The significant increase of IL-6 and IL-17 as well as the decrease of TGF-β was indicated in RSA group (P<0.05). Also, IL-10 did not vary among the groups (P>0.05). ConclusionThese remarks prove that the decrease in regulatory factors such as CD4+CD25bright T-cells, TGF-β and FoxP3 expression may disrupt immune tolerance and homeostasis during pregnancy. Also, the environment rich in RORγt, IL-6, and IL-17 suggests the detrimental role of TH17 cells, which may lead to fetal rejection.