MicroRNA-15b Suppresses Th17 Differentiation and Is Associated with Pathogenesis of Multiple Sclerosis by Targeting O-GlcNAc Transferase

The role of miRNAs in T helper cell development, activation, fate decisions and tumor immunity

T helper (Th) cells are central members of adaptive immunity and comprise the last line of defense against pathogen infection and malignant cell invasion by secreting specific cytokines. These cytokines then attract or induce the activation and differentiation of other immune cells, including antibody-producing B cells and cytotoxic CD8+ T cells. Therefore, the bidirectional communication between Th cells and tumor cells and their positioning within the tumor microenvironment (TME), especially the tumor immune microenvironment (TIME), sculpt the tumor immune landscape, which affects disease initiation and progression. The type, number, and condition of Th cells in the TME and TIME strongly affect tumor immunity, which is precisely regulated by key effectors, such as granzymes, perforins, cytokines, and chemokines. Moreover, microRNAs (miRNAs) have emerged as important regulators of Th cells. In this review, we discuss the role of miRNAs in regulating Th cell mediated adaptive immunity, focusing on the development, activation, fate decisions, and tumor immunity.

The role of miRNAs in multiple sclerosis pathogenesis, diagnosis, and therapeutic resistance

In recent years, microRNAs (miRNAs) have gained increased attention from researchers around the globe. Although it is twenty nucleotides long, it can modulate several gene targets simultaneously. Their mal expression is a signature of various pathologies, and they provide the foundation to elucidate the molecular mechanisms of each pathology. Among the debilitating central nervous system (CNS) disorders with a growing prevalence globally is the multiple sclerosis (MS). Moreover, the diagnosis of MS is challenging due to the lack of disease-specific biomarkers, and the diagnosis mainly depends on ruling out other disabilities. MS could adversely affect patients' lives through its progression, and only symptomatic treatments are available as therapeutic options, but an exact cure is yet unavailable. Consequently, this review hopes to further the study of the biological features of miRNAs in MS and explore their potential as a therapeutic target.

Protein O-GlcNAcylation in multiple immune cells and its therapeutic potential

O-GlcNAcylation is a post-translational modification of proteins that involves the addition of O-GlcNAc to serine or threonine residues of nuclear or cytoplasmic proteins, catalyzed by O-GlcNAc transferase (OGT). This modification is highly dynamic and can be reversed by O-GlcNAcase (OGA). O-GlcNAcylation is widespread in the immune system, which engages in multiple physiologic and pathophysiologic processes. There is substantial evidence indicating that both the hexosamine biosynthesis pathway (HBP) and O-GlcNAcylation are critically involved in regulating immune cell function. However, the precise role of O-GlcNAcylation in the immune system needs to be adequately elucidated. This review offers a thorough synopsis of the present research on protein O-GlcNAcylation, accentuating the molecular mechanisms that control immune cells' growth, maturation, and performance via this PTM.

Breast cancer tumor microenvironment affects Treg/IL-17-producing Treg/Th17 cell axis: Molecular and therapeutic perspectives

The tumor microenvironment (TME) comprises a variety of immune cells, among which T cells exert a prominent axial role in tumor development or anti-tumor responses in patients with breast cancer (BC). High or low levels of anti-inflammatory cytokines, such as transforming growth factor β, in the absence or presence of proinflammatory cytokines, such as interleukin-6 (IL-6), delineate the fate of T cells toward either regulatory T (Treg) or T helper 17 (Th17) cells, respectively. The transitional state of RORγt⁺Foxp3⁺ Treg (IL-17-producing Treg) resides in the middle of this reciprocal polarization, which is known as Treg/IL-17-producing Treg/Th17 cell axis. TME secretome, including microRNAs, cytokines, and extracellular vesicles, can significantly affect this axis. Furthermore, immune checkpoint inhibitors may be used to reconstruct immune cells; however, some of these novel therapies may favor tumor development. Therefore, understanding secretory and cell-associated factors involved in their differentiation or polarization and functions may be targeted for BC management. This review discusses microRNAs, cytokines, and extracellular vesicles (as secretome), as well as transcription factors and immune checkpoints (as cell-associated factors), which influence the Treg/IL-17-producing Treg/Th17 cell axis in BC. Furthermore, approved or ongoing clinical trials related to the modulation of this axis in the TME of BC are described to broaden new horizons of promising therapeutic approaches.

The Mutual Relationship between Glycosylation and Non-Coding RNAs in Cancer and Other Physio-Pathological Conditions

Glycosylation, which consists of the enzymatic addition of sugars to proteins and lipids, is one of the most important post-co-synthetic modifications of these molecules, profoundly affecting their activity. Although the presence of carbohydrate chains is crucial for fine-tuning the interactions between cells and molecules, glycosylation is an intrinsically stochastic process regulated by the relative abundance of biosynthetic (glycosyltransferases) and catabolic (glycosidases) enzymes, as well as sugar carriers and other molecules. Non-coding RNAs, which include microRNAs, long non-coding RNAs and circRNAs, establish a complex network of reciprocally interacting molecules whose final goal is the regulation of mRNA expression. Likewise, these interactions are stochastically regulated by ncRNA abundance. Thus, while protein sequence is deterministically dictated by the DNA/RNA/protein axis, protein abundance and activity are regulated by two stochastic processes acting, respectively, before and after the biosynthesis of the protein axis. Consequently, the worlds of glycosylation and ncRNA are closely interconnected and mutually interacting. In this paper, we will extensively review the many faces of the ncRNA-glycosylation interplay in cancer and other physio-pathological conditions.

MicroRNA expression profiles of peripheral blood and mononuclear cells in myasthenia gravis: A systematic review

BACKGROUND

Studies have described the role of microRNAs (miRNAs) in thymic function, along with directly observing the altered expression of miRNAs in thymuses of myasthenia gravis (MG) patients; so, miRNAs became a core component in the pathophysiology of MG. However, because the miRNA analysis results are contradictory, the identification of MG-related miRNAs is daunting.

OBJECTIVE

We did a systematic review of studies analyzing the miRNA expression profile of peripheral blood and mononuclear cells for patients with MG.

METHODS

We ran a database search in PubMed, Scopus, and Web of Science on August 17, 2021. Original articles that analyzed miRNA profiles in peripheral blood (serum, plasma, and whole blood) and peripheral blood mononuclear cells (PBMCs) for patients with MG in comparison with a non-MG or healthy control (HC) group were eligible. The quality of studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2).

RESULTS

26 studies were included. The quality of studies was fair (median score, 5). Among 226 different miRNAs that were deregulated in at least one study (range, 1-87), ten miRNAs were significantly deregulated in three or more studies. Five miRNAs (50%) showed the same deregulation: miR-106b-3p and miR-21-5p were consistently upregulated, and miR-20b, miR-15b, and miR-16 were consistently downregulated. Also, there were five miRNAs that were mostly upregulated, miR-150-5p, miR-146a, miR-30e-5p, and miR-338-3p, or downregulated, miR-324-3p, across studies.

CONCLUSION

These miRNAs contribute to different pathways, importantly neural apoptosis and autophagy, inflammation, T regulatory cell development, and T helper cell balance. Prior to being used for diagnostic and therapeutic purposes, it is required to pursue molecular mechanisms these consistently and mostly dysregulated miRNAs specifically use in the context of MG.

MicroRNAs as T Lymphocyte Regulators in Multiple Sclerosis

MicroRNA (miRNA) is a class of endogenous non-coding small RNA with regulatory activities, which generally regulates the expression of target genes at the post-transcriptional level. Multiple Sclerosis (MS) is thought to be an autoimmune-mediated chronic inflammatory demyelinating disease of the central nervous system (CNS) that typically affect young adults. T lymphocytes play an important role in the pathogenesis of MS, and studies have suggested that miRNAs are involved in regulating the proliferation, differentiation, and functional maintenance of T lymphocytes in MS. Dysregulated expression of miRNAs may lead to the differentiation balance and dysfunction of T lymphocytes, and they are thus involved in the occurrence and development of MS. In addition, some specific miRNAs, such as miR-155 and miR-326, may have potential diagnostic values for MS or be useful for discriminating subtypes of MS. Moreover, miRNAs may be a promising therapeutic strategy for MS by regulating T lymphocyte function. By summarizing the recent literature, we reviewed the involvement of T lymphocytes in the pathogenesis of MS, the role of miRNAs in the pathogenesis and disease progression of MS by regulating T lymphocytes, the possibility of differentially expressed miRNAs to function as biomarkers for MS diagnosis, and the therapeutic potential of miRNAs in MS by regulating T lymphocytes.

O-Linked β-N-Acetylglucosamine Modification: Linking Hypertension and the Immune System

The O-linked β-N-acetylglucosamine modification (O-GlcNAcylation) of proteins dynamically regulates protein function, localization, stability, and interactions. This post-translational modification is intimately linked to cardiovascular disease, including hypertension. An increasing number of studies suggest that components of innate and adaptive immunity, active players in the pathophysiology of hypertension, are targets for O-GlcNAcylation. In this review, we highlight the potential roles of O-GlcNAcylation in the immune system and discuss how those immune targets of O-GlcNAcylation may contribute to arterial hypertension.

Targeting Protein O-GlcNAcylation, a Link between Type 2 Diabetes Mellitus and Inflammatory Disease

Unresolved hyperglycaemia, a hallmark of type 2 diabetes mellitus (T2DM), is a well characterised manifestation of altered fuel homeostasis and our understanding of its role in the pathologic activation of the inflammatory system continues to grow. Metabolic disorders like T2DM trigger changes in the regulation of key cellular processes such as cell trafficking and proliferation, and manifest as chronic inflammatory disorders with severe long-term consequences. Activation of inflammatory pathways has recently emerged as a critical link between T2DM and inflammation. A substantial body of evidence has suggested that this is due in part to increased flux through the hexosamine biosynthetic pathway (HBP). The HBP, a unique nutrient-sensing metabolic pathway, produces the activated amino sugar UDP-GlcNAc which is a critical substrate for protein O-GlcNAcylation, a dynamic, reversible post-translational glycosylation of serine and threonine residues in target proteins. Protein O-GlcNAcylation impacts a range of cellular processes, including inflammation, metabolism, trafficking, and cytoskeletal organisation. As increased HBP flux culminates in increased protein O-GlcNAcylation, we propose that targeting O-GlcNAcylation may be a viable therapeutic strategy for the prevention and management of glucose-dependent pathologies with inflammatory components.

Scavenging the hidden impacts of non-coding RNAs in multiple sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory disease that causes severe neurological dysfunction leading to disabilities in patients. The prevalence of the disease has been increasing gradually worldwide, and the specific etiology behind the disease is not yet fully understood. Therapies aimed against treating MS patients have been growing lately, intending to delay the disease progression and increase the patients' quality of life. Various pathways play crucial roles in developing the disease, and several therapeutic approaches have been tackling those pathways. However, these strategies have shown several side effects and inconsistent efficacy. MicroRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs) have been shown to act as key players in various disease pathogenesis and development. Several proinflammatory and anti-inflammatory miRNAs have been reported to participate in the development of MS. Hence, the review assesses the role of miRNAs, lncRNAs, and circRNAs in regulating immune cell functions better to understand their impact on the molecular mechanics of MS.

O-GlcNAcylation in Chronic Lymphocytic Leukemia and Other Blood Cancers

In the past decade, aberrant O-GlcNAcylation has emerged as a new hallmark of cancer. O-GlcNAcylation is a post-translational modification that results when the amino-sugar β-D-N-acetylglucosamine (GlcNAc) is made in the hexosamine biosynthesis pathway (HBP) and covalently attached to serine and threonine residues in intracellular proteins by the glycosyltransferase O-GlcNAc transferase (OGT). O-GlcNAc moieties reflect the metabolic state of a cell and are removed by O-GlcNAcase (OGA). O-GlcNAcylation affects signaling pathways and protein expression by cross-talk with kinases and proteasomes and changes gene expression by altering protein interactions, localization, and complex formation. The HBP and O-GlcNAcylation are also recognized to mediate survival of cells in harsh conditions. Consequently, O-GlcNAcylation can affect many of the cellular processes that are relevant for cancer and is generally thought to promote tumor growth, disease progression, and immune escape. However, recent studies suggest a more nuanced view with O-GlcNAcylation acting as a tumor promoter or suppressor depending on the stage of disease or the genetic abnormalities, proliferative status, and state of the p53 axis in the cancer cell. Clinically relevant HBP and OGA inhibitors are already available and OGT inhibitors are in development to modulate O-GlcNAcylation as a potentially novel cancer treatment. Here recent studies that implicate O-GlcNAcylation in oncogenic properties of blood cancers are reviewed, focusing on chronic lymphocytic leukemia and effects on signal transduction and stress resistance in the cancer microenvironment. Therapeutic strategies for targeting the HBP and O-GlcNAcylation are also discussed.

O-GlcNAcylation links oncogenic signals and cancer epigenetics

Prevalent dysregulation of epigenetic modifications plays a pivotal role in cancer. Targeting epigenetic abnormality is a new strategy for cancer therapy. Understanding how conventional oncogenic factors cause epigenetic abnormality is of great basic and translational value. O-GlcNAcylation is a protein modification which affects physiology and pathophysiology. In mammals, O-GlcNAcylation is catalyzed by one single enzyme OGT and removed by one single enzyme OGA. O-GlcNAcylation is affected by the availability of the donor, UDP-GlcNAc, generated by the serial enzymatic reactions in the hexoamine biogenesis pathway (HBP). O-GlcNAcylation regulates a wide spectrum of substrates including many proteins involved in epigenetic modification. Like epigenetic modifications, abnormality of O-GlcNAcylation is also common in cancer. Studies have revealed substantial impact on HBP enzymes and OGT/OGA by oncogenic signals. In this review, we will first summarize how oncogenic signals regulate HBP enzymes, OGT and OGA in cancer. We will then integrate this knowledge with the up to date understanding how O-GlcNAcylation regulates epigenetic machinery. With this, we propose a signal axis from oncogenic signals through O-GlcNAcylation dysregulation to epigenetic abnormality in cancer. Further elucidation of this axis will not only advance our understanding of cancer biology but also provide new revenues towards cancer therapy.

MicroRNA Sequencing Analysis in Obstructive Sleep Apnea and Depression: Anti-Oxidant and MAOA-Inhibiting Effects of miR-15b-5p and miR-92b-3p through Targeting PTGS1-NF-κB-SP1 Signaling

The aim of this study was to identify novel microRNAs related to obstructive sleep apnea (OSA) characterized by intermittent hypoxia with re-oxygenation (IHR) injury. Illumina MiSeq was used to identify OSA-associated microRNAs, which were validated in an independent cohort. The interaction between candidate microRNA and target genes was detected in the human THP-1, HUVEC, and SH-SY5Y cell lines. Next-generation sequencing analysis identified 22 differentially expressed miRs (12 up-regulated and 10 down-regulated) in OSA patients. Enriched predicted target pathways included senescence, adherens junction, and AGE-RAGE/TNF-α/HIF-1α signaling. In the validation cohort, miR-92b-3p and miR-15b-5p gene expressions were decreased in OSA patients, and negatively correlated with an apnea hypopnea index. PTGS1 (COX1) gene expression was increased in OSA patients, especially in those with depression. Transfection with miR-15b-5p/miR-92b-3p mimic in vitro reversed IHR-induced early apoptosis, reactive oxygen species production, MAOA hyperactivity, and up-regulations of their predicted target genes, including PTGS1, ADRB1, GABRB2, GARG1, LEP, TNFSF13B, VEGFA, and CXCL5. The luciferase assay revealed the suppressed PTGS1 expression by miR-92b-3p. Down-regulated miR-15b-5p/miR-92b-3p in OSA patients could contribute to IHR-induced oxidative stress and MAOA hyperactivity through the eicosanoid inflammatory pathway via directly targeting PTGS1-NF-κB-SP1 signaling. Over-expression of the miR-15b-5p/miR-92b-3p may be a new therapeutic strategy for OSA-related depression.

Non-coding RNAs in the Pathogenesis of Multiple Sclerosis

Multiple sclerosis (MS) is an early onset chronic neurological condition in adults characterized by inflammation, demyelination, gliosis, and axonal loss in the central nervous system. The pathological cause of MS is complex and includes both genetic and environmental factors. Non-protein-coding RNAs (ncRNAs), specifically miRNAs and lncRNAs, are important regulators of various biological processes. Over the past decade, many studies have investigated both miRNAs and lncRNAs in patients with MS. Since then, insightful knowledge has been gained in this field. Here, we review the role of miRNAs and lncRNAs in MS pathogenesis and discuss their implications for diagnosis and treatment.

The circular RNA circINPP4B acts as a sponge of miR-30a to regulate Th17 cell differentiation during progression of experimental autoimmune encephalomyelitis

Circular RNAs (circRNAs) regulate gene expression and participate in various biological and pathological processes. However, little is known about the effects of specific circRNAs on T helper cell 17 (Th17) differentiation and related autoimmune diseases, such as multiple sclerosis (MS). Here, using transcriptome microarray analysis at different stages of experimental autoimmune encephalomyelitis (EAE), we identified the EAE progression-related circINPP4B, which showed upregulated expression in Th17 cells from mice with EAE and during Th17 differentiation in vitro. Silencing of circINPP4B inhibited Th17 differentiation and alleviated EAE, characterized by less demyelination and Th17 infiltration in the spinal cord. Mechanistically, circINPP4B served as a sponge that directly targeted miR-30a to regulate Th17 differentiation. Furthermore, circINPP4B levels were associated with the developing phases of clinical relapsing-remitting MS patients. Our results indicate that circINPP4B plays an important role in promoting Th17 differentiation and progression of EAE by targeting miR-30a, which provides a potential diagnostic and therapeutic target for Th17-mediated MS.

miRNAs Alter T Helper 17 Cell Fate in the Pathogenesis of Autoimmune Diseases

T helper 17 (Th17) cells are characterized by the secretion of the IL-17 cytokine and are essential for the immune response against bacterial and fungal infections. Despite the beneficial roles of Th17 cells, unrestrained IL-17 production can contribute to immunopathology and inflammatory autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, and inflammatory bowel disease. Although these diverse outcomes are directed by the activation of Th17 cells, the regulation of Th17 cells is incompletely understood. The discovery that microRNAs (miRNAs) are involved in the regulation of Th17 cell differentiation and function has greatly improved our understanding of Th17 cells in immune response and disease. Here, we provide an overview of the biogenesis and function of miRNA and summarize the role of miRNAs in Th17 cell differentiation and function. Finally, we focus on recent advances in miRNA-mediated dysregulation of Th17 cell fate in autoimmune diseases.

Small noncoding RNA profiling across cellular and biofluid compartments and their implications for multiple sclerosis immunopathology

Dysregulation of microRNAs (miRNAs), a type of small noncoding RNAs (sncRNAs), has frequently been associated with multiple sclerosis (MS). However, most studies have focused on peripheral blood, and few investigated other classes of sncRNAs. To address this, we analyzed all classes of sncRNAs in matching peripheral blood mononuclear cells, plasma, cerebrospinal fluid (CSF) cells, and cell-free CSF from MS patients and controls. We demonstrate widespread alterations of small nuclear (snRNA)–derived RNAs, small nucleolar-derived RNAs (sdRNAs), transfer RNA–derived fragments, and miRNAs, particularly in CSF cells. The striking contrast between the periphery and central nervous system and between relapse and remission phases of disease highlights the importance of sncRNA-mediated mechanisms in MS, in particular alternative splicing and mRNA translation.

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease affecting the central nervous system (CNS). Small non-coding RNAs (sncRNAs) and, in particular, microRNAs (miRNAs) have frequently been associated with MS. Here, we performed a comprehensive analysis of all classes of sncRNAs in matching samples of peripheral blood mononuclear cells (PBMCs), plasma, cerebrospinal fluid (CSF) cells, and cell-free CSF from relapsing-remitting (RRMS, n = 12 in relapse and n = 11 in remission) patients, secondary progressive (SPMS, n = 6) MS patients, and noninflammatory and inflammatory neurological disease controls (NINDC, n = 11; INDC, n = 5). We show widespread changes in miRNAs and sncRNA-derived fragments of small nuclear, nucleolar, and transfer RNAs. In CSF cells, 133 out of 133 and 115 out of 117 differentially expressed sncRNAs were increased in RRMS relapse compared to remission and RRMS compared to NINDC, respectively. In contrast, 65 out of 67 differentially expressed PBMC sncRNAs were decreased in RRMS compared to NINDC. The striking contrast between the periphery and CNS suggests that sncRNA-mediated mechanisms, including alternative splicing, RNA degradation, and mRNA translation, regulate the transcriptome of pathogenic cells primarily in the CNS target organ.

Baricitinib Ameliorates Experimental Autoimmune Encephalomyelitis by Modulating the Janus Kinase/Signal Transducer and Activator of Transcription Signaling Pathway

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis (MS) and a CD4+ T cell-mediated autoimmune disease. The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is recognized as the major mechanism that regulates the differentiation and function of T helper (Th) 1 and Th17 cells, which are recognized as pivotal effector cells responsible for the development of EAE. We used baricitinib, a JAK 1/2 inhibitor, to investigate the therapeutic efficacy of inhibiting the JAK/STAT pathway in EAE mice. Our results showed that baricitinib significantly delayed the onset time, decreased the severity of clinical symptoms, shortened the duration of EAE, and alleviated demyelination and immune cell infiltration in the spinal cord. In addition, baricitinib treatment downregulated the proportion of interferon-γ+CD4+ Th1 and interleukin-17+CD4+ Th17 cells, decreased the levels of retinoic acid-related orphan receptor γ t and T-bet mRNA, inhibited lymphocyte proliferation, and decreased the expression of proinflammatory cytokines and chemokines in the spleen of mice with EAE. Furthermore, our results showed the role of baricitinib in suppressing the phosphorylation of STATs 1, 3, and 4 in the spleen of EAE mice. Therefore, our study demonstrates that baricitinib could potentially alleviate inflammation in mice with EAE and may be a promising candidate for treating MS.

Serum Based miRNA as a Diagnostic Biomarker for Multiple Sclerosis: a Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to identify deferentially expressed serum miRNAs in multiple sclerosis patients and to evaluate their diagnostic value in multiple sclerosis diagnosis. Studies were identified on PubMed, Google scholar and Saudi digital library up to 30 September 2019. Articles that examined miRNA expression level in MS patients compared to healthy control group were included in the review and the data were extracted by three independent author. The comprehensive Meta-Analysis version 3 software was used for meta-analysis and heterogeneity of studies was identified according to I2 value. Our literatures search identified 9 eligible articles concerning the serum miRNA as a diagnostic biomarker for multiple sclerosis in comparison to healthy control group. 19 serum miRNAs differentially expressed in MS patients were identified (8 downregulated, 11 upregulated and 1 with discordant result). In publications that provided information on specific miRNA diagnostic value, the pooled AUC was 72% (95% CI 0.65-0.78, p-value 0.00) for the overall multiple sclerosis patients and primary progressive MS (PPMS) (95% CI 0.66-0.78 p-value 0.00). A miRNA panel of four miRNAs showed high sensitivity (73%) and specificity (68%) in distinguishing multiple sclerosis from control groups. When using single miRNA (miR-145), the sensitivity increased to 79% and the specificity to 87%. The available data from the literature and this meta-analysis suggests the potential use of serum miRNA as biomarkers for early diagnosis of MS with high sensitivity and specificity in distinguishing multiple sclerosis subtypes from healthy controls.Abbreviation: MS: Multiple sclerosis; IDD: inflammatory demyelinating diseases; RRMS: relapsing-remitting Multiple sclerosis; PPMS: primary progressive Multiple sclerosis; SPMS: secondary progressive Multiple sclerosis; NMO: Neuromyelitis optica; miRNA: microRNA; ECmiRNA: extracellular microRNA; AUC: Area Under the Curve; ROC: Receiver Operator Characteristic.

MicroRNA-221 and -222 modulate intestinal inflammatory Th17 cell response as negative feedback regulators downstream of interleukin-23

MicroRNAs are important regulators of immune responses. Here, we show miR-221 and miR-222 modulate the intestinal Th17 cell response. Expression of miR-221 and miR-222 was induced by proinflammatory cytokines and repressed by the cytokine TGF-β. Molecular targets of miR-221 and miR-222 included Maf and Il23r, and loss of miR-221 and miR-222 expression shifted the transcriptomic spectrum of intestinal Th17 cells to a proinflammatory signature. Although the loss of miR-221 and miR-222 was tolerated for maintaining intestinal Th17 cell homeostasis in healthy mice, Th17 cells lacking miR-221 and miR-222 expanded more efficiently in response to IL-23. Both global and T cell-specific deletion of miR-221 and miR-222 rendered mice prone to mucosal barrier damage. Collectively, these findings demonstrate that miR-221 and miR-222 are an integral part of intestinal Th17 cell response that are induced after IL-23 stimulation to constrain the magnitude of proinflammatory response.

miRNA-Dependent CD4+ T Cell Differentiation in the Pathogenesis of Multiple Sclerosis

Multiple sclerosis (MS) is characterized by multifocal lesions, chronic inflammatory condition, and degenerative processes within the central nervous system (CNS) leading to demyelination. The most important cells involved in its pathogenesis are those which are CD4⁺, particularly proinflammatory Th1/Th17 and regulatory Treg. Signal cascades associated with CD4⁺ differentiation are regulated by microRNAs (miRNAs): short, single-stranded RNAs, responsible for negative regulation of gene expression at the posttranscriptional level. Several miRNAs have been consistently reported as showing dysregulated expression in MS, and their expression patterns may be elevated or decreased, depending on the function of specific miRNA in the immune system. Studies in MS patients indicate that, among others, miR-141, miR-200a, miR-155, miR-223, and miR-326 are upregulated, while miR-15b, miR-20b, miR-26a, and miR-30a are downregulated. Dysregulation of these miRNAs may contribute to the imbalance between pro- and anti-inflammatory processes, since their targets are associated with the regulation of Th1/Th17 and Treg cell differentiation. Highly expressed miRNAs can in turn suppress translation of key Th1/Th17 differentiation inhibitors. miRNA dysregulation may result from the impact of various factors at each stage of their biogenesis. Immature miRNA undergoes multistage transcriptional and posttranscriptional modifications; therefore, any protein involved in the processing of miRNAs can potentially lead to disturbances in their expression. Epigenetic modifications that have a direct impact on miRNA gene transcription may also play an important role.

Lipopolysaccharide Induces GFAT2 Expression to Promote O-Linked β-N-Acetylglucosaminylation and Attenuate Inflammation in Macrophages

Glycosylation with O-linked β-N-acetylglucosamine (O-GlcNAcylation) is a reversible posttranslational modification that regulates the activity of intracellular proteins according to glucose availability and its metabolism through the hexosamine biosynthesis pathway. This modification has been involved in the regulation of various immune cell types, including macrophages. However, little is known concerning the mechanisms that regulate the protein O-GlcNAcylation level in these cells. In the present work, we demonstrate that LPS treatment induces a marked increase in protein O-GlcNAcylation in RAW264.7 cells, bone marrow-derived and peritoneal mouse macrophages, as well as human monocyte-derived macrophages. Targeted deletion of OGT in macrophages resulted in an increased effect of LPS on NOS2 expression and cytokine production, suggesting that O-GlcNAcylation may restrain inflammatory processes induced by LPS. The effect of LPS on protein O-GlcNAcylation in macrophages was associated with an increased expression and activity of glutamine fructose 6-phosphate amidotransferase (GFAT), the enzyme that catalyzes the rate-limiting step of the hexosamine biosynthesis pathway. More specifically, we observed that LPS potently stimulated GFAT2 isoform mRNA and protein expression. Genetic or pharmacological inhibition of FoxO1 impaired the LPS effect on GFAT2 expression, suggesting a FoxO1-dependent mechanism. We conclude that GFAT2 should be considered a new LPS-inducible gene involved in regulation of protein O-GlcNAcylation, which permits limited exacerbation of inflammation upon macrophage activation.

The role of O-GlcNAcylation in immunity against infections

Mounting an effective immune response is crucial for the host to protect itself against invading pathogens. It is now well appreciated that reprogramming of core metabolic pathways in immune cells is a key requirement for their activation and function during infections. The role of several ancillary metabolic pathways in shaping immune cell function is less well understood. One such pathway, for which interest has recently been growing, is the hexosamine biosynthesis pathway (HBP) that generates uridine diphosphate N‐acetylglucosamine (UDP‐GlcNAc), the donor substrate for a specific form of glycosylation termed O‐GlcNAcylation. O‐GlcNAc is an intracellular post‐translational modification that alters the functional properties of the modified proteins, in particular transcription factors and epigenetic regulators. An increasing number of studies suggest a central role for the HBP and O‐GlcNAcylation in dictating immune cell function, including the response to different pathogens. We here discuss the most recent insights regarding O‐GlcNAcylation and immunity, and explore whether targeting of O‐GlcNAcylation could hold promise as a therapeutic approach to modulate immune responses to infections.

Let-7f-5p suppresses Th17 differentiation via targeting STAT3 in multiple sclerosis

T helper 17 (Th17) cells are regarded as key factors in the pathogenesis of multiple sclerosis (MS). Although the involvement of certain microRNAs (miRNAs) in the development of MS has been reported, their roles in Th17 cell differentiation and MS pathogenesis remain elusive. In this study, we identified that let-7f-5p expression is significantly downregulated in CD4⁺ T cells from MS patients and during the process of Th17 differentiation. The overexpression of let-7f-5p suppressed Th17 differentiation, whereas the knockdown of let-7f-5p expression enhanced this progress. We then explored the molecular mechanism through which let-7f-5p suppressed Th17 differentiation and identified signal transducer and activator of transcription 3 (STAT3), a pivotal transcription factor of Th17 cells, as a direct target of let-7f-5p. In contrast to the downregulated expression of let-7f-5p, STAT3 and p-STAT3 protein levels were dramatically upregulated and inversely correlated with let-7f-5p in peripheral blood CD4⁺ T cells from MS patients. In conclusion, let-7f-5p functions as a potential inhibitor of Th17 differentiation in the pathogenesis of MS by targeting STAT3 and may serve as a new therapeutic target.

Epigenetics in Multiple Sclerosis

Multiple sclerosis (MS) is an aggravating autoimmune disease that cripples young patients slowly with physical, sensory and cognitive deficits. The break of self-tolerance to neuronal antigens is the key to the pathogenesis of MS, with autoreactive T cells causing demyelination that subsequently leads to inflammation-mediated neurodegenerative events in the central nervous system. The exact etiology of MS remains elusive; however, the interplay of genetic and environmental factors contributes to disease development and progression. Given that genetic variation only accounts for a fraction of risk for MS, extrinsic risk factors including smoking, infection and lack of vitamin D or sunshine, which cause changes in gene expression, contribute to disease development through epigenetic regulation. To date, there is a growing body of scientific evidence to support the important roles of epigenetic processes in MS. In this chapter, the three main layers of epigenetic regulatory mechanisms, namely DNA methylation, histone modification and microRNA-mediated gene regulation, will be discussed, with a particular focus on the role of epigenetics on dysregulated immune responses and neurodegenerative events in MS. Also, the potential for epigenetic modifiers as biomarkers and therapeutics for MS will be reviewed.

A Network of Sputum MicroRNAs Is Associated with Neutrophilic Airway Inflammation in Asthma

Rationale: MicroRNAs are potent regulators of biologic systems that are critical to tissue homeostasis. Individual microRNAs have been identified in airway samples. However, a systems analysis of the microRNA-mRNA networks present in the sputum that contribute to airway inflammation in asthma has not been published.Objectives: Identify microRNA and mRNA networks in the sputum of patients with asthma.Methods: We conducted a genome-wide analysis of microRNA and mRNA in the sputum from patients with asthma and correlated expression with clinical phenotypes. Weighted gene correlation network analysis was implemented to identify microRNA networks (modules) that significantly correlate with clinical features of asthma and mRNA expression networks. MicroRNA expression in peripheral blood neutrophils and lymphocytes and in situ hybridization of the sputum were used to identify the cellular sources of microRNAs. MicroRNA expression obtained before and after ozone exposure was also used to identify changes associated with neutrophil counts in the airway.Measurements and Main Results: Six microRNA modules were associated with clinical features of asthma. A single module (nely) was associated with a history of hospitalizations, lung function impairment, and numbers of neutrophils and lymphocytes in the sputum. Of the 12 microRNAs in the nely module, hsa-miR-223-3p was the highest expressed microRNA in neutrophils and was associated with increased neutrophil counts in the sputum in response to ozone exposure. Multiple microRNAs in the nely module correlated with two mRNA modules enriched for TLR (Toll-like receptor) and T-helper cell type 17 (Th17) signaling and endoplasmic reticulum stress. hsa-miR-223-3p was a key regulator of the TLR and Th17 pathways in the sputum of subjects with asthma.Conclusions: This study of sputum microRNA and mRNA expression from patients with asthma demonstrates the existence of microRNA networks and genes that are associated with features of asthma severity. Among these, hsa-miR-223-3p, a neutrophil-derived microRNA, regulates TLR/Th17 signaling and endoplasmic reticulum stress.

microRNAs: key modulators of disease-modifying therapies in multiple sclerosis

There is a high level of heterogeneity in symptom manifestations and response to disease-modifying therapies (DMTs) in multiple sclerosis (MS), an immune-based neurodegenerative disease with ever-increasing prevalence in recent decades. Because of unknown aspects of the etiopathology of MS and mechanism of action of DMTs, the reason for this variability is undetermined, and much remains to be understood. Traditionally, physicians consider switching to other DMTs based on the exacerbation of symptoms and/or change in the results of magnetic resonance imaging and biochemical factors. Therefore, identifying biological treatment response markers that help us recognizing non-responders rapidly and subsequently choosing another DMTs is necessary. microRNAs (miRNAs) are micromanagers of gene expression which have been profiled in different samples of MS patients, highlighting their role in pathogenetic of MS. Recent studies have investigated expression profiling of miRNAs after treatment with DMTs to clarify possible DMTs-mediated mechanism and obtaining response to therapy biomarkers. In this review, we will discuss the modulation of miRNAs by DMTs in cells and pathways involved in MS.

O-GlcNAcylation and its role in the immune system

O-linked-N-acetylglucosaminylation (O-GlcNAcylation) is a type of glycosylation that occurs when a monosaccharide, O-GlcNAc, is added onto serine or threonine residues of nuclear or cytoplasmic proteins by O-GlcNAc transferase (OGT) and which can be reversibly removed by O-GlcNAcase (OGA). O-GlcNAcylation couples the processes of nutrient sensing, metabolism, signal transduction and transcription, and plays important roles in development, normal physiology and physiopathology. Cumulative studies have indicated that O-GlcNAcylation affects the functions of protein substrates in a number of ways, including protein cellular localization, protein stability and protein/protein interaction. Particularly, O-GlcNAcylation has been shown to have intricate crosstalk with phosphorylation as they both modify serine or threonine residues. Aberrant O-GlcNAcylation on various protein substrates has been implicated in many diseases, including neurodegenerative diseases, diabetes and cancers. However, the role of protein O-GlcNAcylation in immune cell lineages has been less explored. This review summarizes the current understanding of the fundamental biochemistry of O-GlcNAcylation, and discusses the molecular mechanisms by which O-GlcNAcylation regulates the development, maturation and functions of immune cells. In brief, O-GlcNAcylation promotes the development, proliferation, and activation of T and B cells. O-GlcNAcylation regulates inflammatory and antiviral responses of macrophages. O-GlcNAcylation promotes the function of activated neutrophils, but inhibits the activity of nature killer cells.

Aberrant expression of miR-21 in patients with inflammatory bowel disease: A protocol for systematic review and meta analysis

BACKGROUND

microRNAs have drawn more attention due to their function on the inflammatory process. The association between microRNA-21 (miR-21) expression and risk of inflammatory bowel diseases (IBD) remain inconclusive. This study was aimed to acquire a more exact estimation of this relationship.

METHODS

Relevant studies were identified through searching PubMed, Embase, Wanfang, and China National Knowledge Infrastructure database. Pooled standardized mean difference and 95% confidence intervals were calculated using a random-effect model. Publication bias test, sensitivity analysis and subgroup analysis were carried out.

RESULTS

A total of 20 relevant articles comprising 540 patients with ulcerative colitis (UC), 459 patients with Crohn disease (CD) and 511 non-IBD controls were included in this analysis. The expression of miR-21 was significantly increased in colon tissue of both UC and CD patients compared with non-IBD controls. However, there were no significant differences between patients with UC and CD. Moreover, increased miR-21 expression was associated with disease activity status in UC patients, but not in CD patients.

CONCLUSIONS

This meta-analysis demonstrates that the higher miR-21 expression in colon tissue is positively associated with the development of UC and CD, and miR-21 might serve as a disease marker of IBD.

Molecular mechanisms regulating O-linked N-acetylglucosamine (O-GlcNAc)-processing enzymes

The post-translational modification of proteins by O-linked N-acetylglucosamine (O-GlcNAc) dynamically programmes cellular physiology to maintain homoeostasis and tailor biochemical pathways to meet context-dependent cellular needs. Despite diverse roles of played by O-GlcNAc, only two enzymes act antagonistically to govern its cycling; O-GlcNAc transferase installs the monosaccharide on target proteins, and O-GlcNAc hydrolase removes it. The recent literature has exposed a network of mechanisms regulating these two enzymes to choreograph global, and target-specific, O-GlcNAc cycling in response to cellular stress and nutrient availability. Herein, we amalgamate these emerging mechanisms from a structural and molecular perspective to explore how the cell exerts fine control to regulate O-GlcNAcylation of diverse proteins in a selective fashion.

MicroRNA-455-3p mediates GATA3 tumor suppression in mammary epithelial cells by inhibiting TGF-β signaling

GATA3 is a basic and essential transcription factor that regulates many pathophysiological processes and is required for the development of mammary luminal epithelial cells. Loss-of-function GATA3 alterations in breast cancer are associated with poor prognosis. Here, we sought to understand the tumor-suppressive functions GATA3 normally performs. We discovered a role for GATA3 in suppressing epithelial-to-mesenchymal transition (EMT) in breast cancer by activating miR-455-3p expression. Enforced expression of miR-455-3p alone partially prevented EMT induced by transforming growth factor β (TGF-β) both in cells and tumor xenografts by directly inhibiting key components of TGF-β signaling. Pathway and biochemical analyses showed that one miRNA-455-3p target, the TGF-β-induced protein ZEB1, recruits the Mi-2/nucleosome remodeling and deacetylase (NuRD) complex to the promotor region of miR-455 to strictly repress the GATA3-induced transcription of this microRNA. Considering that ZEB1 enhances TGF-β signaling, we delineated a double-feedback interaction between ZEB1 and miR-455-3p, in addition to the repressive effect of miR-455-3p on TGF-β signaling. Our study revealed that a feedback loop between these two axes, specifically GATA3-induced miR-455-3p expression, could repress ZEB1 and its recruitment of NuRD (MTA1) to suppress miR-455, which ultimately regulates TGF-β signaling. In conclusion, we identified that miR-455-3p plays a pivotal role in inhibiting the EMT and TGF-β signaling pathway and maintaining cell differentiation. This forms the basis of that miR-455-3p might be a promising therapeutic intervention for breast cancer.

BCL-6 suppresses miR-142-3p/5p expression in SLE CD4+ T cells by modulating histone methylation and acetylation of the miR-142 promoter

The reduced expression of miR-142-3p/5p in CD4⁺ T cells of SLE patients caused T cell hyperactivity and B cell hyperstimulation. This study aimed to investigate the mechanisms of regulating miR-142-3p/5p expression in SLE CD4⁺ T cells. The BCL-6 expression was significantly increased in SLE CD4⁺ T cells compared with normal controls, and the BCL-6 expression was inversely correlated with miR-142-3p/5p expression. BCL-6 suppresses the expression of miR-142-3p/5p by increasing H3K27me3 level and reducing H3K9/K14ac levels in SLE CD4⁺ T cells. BCL-6 regulates histone modifications in miR-142 promoter by recruiting EZH2 and HDAC5. Furthermore, we observed significantly decreased CD40L, ICOS, and IL-21 expression levels in SLE CD4⁺ T cells with BCL-6 interference, and obviously reduced autoantibody IgG production in autologous B cells co-cultured with BCL-6 inhibited SLE CD4⁺ T cells. Our study found that increased BCL-6 up-regulates H3K27me3 and down-regulates H3K9/14ac at miR-142 promoter in SLE CD4⁺ T cells. These factors induce a declination in miR-142-3p/5p expression, consequently resulting in CD4⁺ T cell hyperactivity.

O-GlcNAcylation in immunity and inflammation: An intricate system (Review)

Chronic, low‑grade inflammation associated with obesity and diabetes result from the infiltration of adipose and vascular tissue by immune cells and contributes to cardiovascular complications. Despite an incomplete understanding of the mechanistic underpinnings of immune cell differentiation and inflammation, O‑GlcNAcylation, the addition of O‑linked N‑acetylglucosamine (O‑GlcNAc) to cytoplasmic, nuclear and mitochondrial proteins by the two cycling enzymes, the O‑linked N‑acetylglucosamine transferase (OGT) and the O‑GlcNAcase (OGA), may contribute to fine‑tune immunity and inflammation in both physiological and pathological conditions. Early studies have indicated that O‑GlcNAcylation of proteins play a pro‑inflammatory role in diabetes and insulin resistance, whereas subsequent studies have demonstrated that this post‑translational modification could also be protective against acute injuries. These studies suggest that diverse types of insults result in dynamic changes to O‑GlcNAcylation patterns, which fluctuate with cellular metabolism to promote or inhibit inflammation. In this review, the current understanding of O‑GlcNAcylation and its adaptive modulation in immune and inflammatory responses is summarized.

Excessive miR-152-3p Results in Increased BAFF Expression in SLE B-Cells by Inhibiting the KLF5 Expression

The increased BAFF expression in B-cells of patients with systemic lupus erythematosus (SLE) is associated with B-cell hyperstimulation and T-cell hyperactivity, but the underlying mechanisms are still unclear. This study aimed to uncover the mechanisms that regulate the BAFF expression in SLE B-cells. The results demonstrated that the expression of miR-152-3p was significantly increased in SLE B-cells compared with normal controls. This study confirmed that Kruppel-like factor 5 (KLF5) was a direct target of miR-152-3p, and it could bind to the promoter region of BAFF and inhibit its expression in B-cells. The upregulation of miRNA-152-3p expression decreased the KLF5 expression and increased the BAFF expression in SLE B-cells. Knockdown of miR-152-3p expression inhibited the self-reactivity of SLE B-cells, thereby reducing the autoantibody production. The increased miR-152-3p expression in SLE B-cells led to an increase in BAFF expression by inhibiting KLF5 expression. These factors caused B-cell self-reactivity and autoantibody production, allowing participation in the disease process of SLE.

Elevated O-GlcNAcylation enhances pro-inflammatory Th17 function by altering the intracellular lipid microenvironment

Chronic, low-grade inflammation increases the risk for atherosclerosis, cancer, and autoimmunity in diseases such as obesity and diabetes. Levels of CD4⁺ T helper 17 (Th17) cells, which secrete interleukin 17A (IL-17A), are increased in obesity and contribute to the inflammatory milieu; however, the relationship between signaling events triggered by excess nutrient levels and IL-17A-mediated inflammation is unclear. Here, using cytokine, quantitative real-time PCR, immunoprecipitation, and ChIP assays, along with lipidomics and MS-based approaches, we show that increased levels of the nutrient-responsive, post-translational protein modification, O-GlcNAc, are present in naive CD4⁺ T cells from a diet-induced obesity murine model and that elevated O-GlcNAc levels increase IL-17A production. We also found that increased binding of the Th17 master transcription factor RAR-related orphan receptor γ t variant (RORγt) at the IL-17 gene promoter and enhancer, as well as significant alterations in the intracellular lipid microenvironment, elevates the production of ligands capable of increasing RORγt transcriptional activity. Importantly, the rate-limiting enzyme of fatty acid biosynthesis, acetyl-CoA carboxylase 1 (ACC1), is O-GlcNAcylated and necessary for production of these RORγt-activating ligands. Our results suggest that increased O-GlcNAcylation of cellular proteins may be a potential link between excess nutrient levels and pathological inflammation.

Proteomic analysis of the OGT interactome: novel links to epithelial-mesenchymal transition and metastasis of cervical cancer

The role of O-GlcNAc transferase (OGT) in gene regulation and tumor invasion is poorly understood. Here, we have identified several previously undiscovered OGT-interacting proteins, including the PRMT5/WDR77 complex, the PRC2 complex, the ten-eleven translocation (TET) family, the CRL4B complex and the nucleosome remodeling and deacetylase (NuRD) complex. Genome-wide analysis of target genes responsive to OGT resulted in identification of a cohort of genes including SNAI1 and ING4 that are critically involved in cell epithelial–mesenchymal transition and invasion/metastasis. We have demonstrated that OGT promotes carcinogenesis and metastasis of cervical cancer cells. OGT’s expression is significantly upregulated in cervical cancer, and low OGT level is correlated with improved prognosis. Our study has thus revealed a mechanistic link between OGT and tumor progression, providing potential prognostic indicators and targets for cancer therapy.

Small non-coding RNAs as important players, biomarkers and therapeutic targets in multiple sclerosis: A comprehensive overview

Multiple sclerosis (MS) is a leading cause of progressive disability among young adults caused by inflammation, demyelination and axonal loss in the central nervous system. Small non-coding RNAs (sncRNAs) are important regulators of various biological processes and could therefore play important roles in MS. Over the past decade, a large number of studies investigated sncRNAs in MS patients, focusing primarily on microRNAs (miRNAs). Overwhelming 500 miRNAs have been reported as dysregulated in MS. Nevertheless, owing to a large heterogeneity between studies it is challenging to evaluate the reproducibility of findings, in turn hampering our knowledge about the functional roles of miRNAs in disease. We systematically searched main databases and evaluated results from all studies that examined sncRNAs in MS to date (n = 61) and provided a detailed overview of experimental design and findings of these studies. We focused on the mechanisms of the most dysregulated sncRNAs and used predicted targets of the most dysregulated sncRNAs as input for functional enrichment analysis to highlight affected pathways. The prime affected pathway was TGF-β signaling. This multifunctional cytokine is important in the differentiation and function of T helper type 17 (Th17) and regulatory T (Treg) cells, with opposing functions in the disease. Recent studies demonstrate the importance of miRNAs in controlling the balance between Th17/Th1 cells and Tregs and, importantly, the potential to exploit this paradigm for therapeutic purposes. Additionally, some of the discussed miRNAs could potentially serve as biomarkers of disease. In order to assist researchers in evaluating the evidence of a particular sncRNA in the pathogenesis of MS, we provide a detailed overview of experimental design and findings of these studies to date.

Dietary Modulation of Intestinal Microbiota: Future Opportunities in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease that affects the functioning of the central nervous system (CNS). Recent studies on MS and its animal model, experimental autoimmune encephalomyelitis (EAE), have shown that the composition and abundance of microbes in the intestinal microbiota are an environmental risk factor for the development of MS and EAE. Changes in certain microbial populations in the gastrointestinal tract can cause MS in humans, but MS inflammation can be reduced or even prevented by introducing other commensal microbes that produce beneficial metabolites. Other risk factors for MS include the presence of an altered gut physiology and the interaction between the intestinal microbiota and the immune system. Metabolites including short-chain fatty acids (SCFAs), such as butyrate, are the primary signaling molecules produced by the intestinal microbiota that interact with the host immune system, suggesting an association between MS pathophysiology and gut microbiota. In addition, several host microRNAs present in the gut have been found to interact with the intestinal microbial community, these interactions may indirectly affect the neurological system. Increasing evidence has shown that regulation of the intestinal microbiota is an important approach for reducing MS inflammation. Thus, here we review the use of diet to alter the gut microbiota and its application in the treatment and prevention of MS.

NF-κB/mTOR/MYC Axis Drives PRMT5 Protein Induction After T Cell Activation via Transcriptional and Non-transcriptional Mechanisms

Multiple sclerosis is an autoimmune disease of the central nervous system (CNS) mediated by CD4⁺ T cells and modeled via experimental autoimmune encephalomyelitis (EAE). Inhibition of PRMT5, the major Type II arginine methyltransferase, suppresses pathogenic T cell responses and EAE. PRMT5 is transiently induced in proliferating memory inflammatory Th1 cells and during EAE. However, the mechanisms driving PRMT5 protein induction and repression as T cells expand and return to resting is currently unknown. Here, we used naive mouse and memory mouse and human Th1/Th2 cells as models to identify mechanisms controlling PRMT5 protein expression in initial and recall T cell activation. Initial activation of naive mouse T cells resulted in NF-κB-dependent transient Prmt5 transcription and NF-κB, mTOR and MYC-dependent PRMT5 protein induction. In murine memory Th cells, transcription and miRNA loss supported PRMT5 induction to a lesser extent than in naive T cells. In contrast, NF-κB/MYC/mTOR-dependent non-transcriptional PRMT5 induction played a major role. These results highlight the importance of the NF-κB/mTOR/MYC axis in PRMT5-driven pathogenic T cell expansion and may guide targeted therapeutic strategies for MS.

Noncoding RNAs in multiple sclerosis

Multiple sclerosis (MS), a chronic inflammatory demyelinating disease of the central nervous system, is characterized by axonal degeneration and gliosis. Although the causes of MS remain unknown, gene dysregulation in the central nervous system has been associated with the disease pathogenesis. As such, the various regulators of gene expression may be contributing factors. The noncoding (nc) RNAs have piqued the interest of MS researchers due to their known functions in human physiology and various pathological processes, despite being generally characterized as transcripts without apparent protein-coding capacity. Accumulating evidence has indicated that ncRNAs participate in the regulation of MS by acting as epigenetic factors, especially the long (l) ncRNAs and the micro (mi) RNAs, and they are now recognized as key regulatory molecules in MS. In this review, we summarize the most current studies on the contribution of ncRNAs in MS pathogenic processes and discuss their potential applications in the diagnosis and treatment of MS.

MiRNAs and inflammatory bowel disease: An interesting new story

Inflammatory bowel disease (IBD), as a chronic and recurrent inflammatory disorder, is caused by a dysregulated and aberrant immune response to exposed environmental factors in genetically susceptible individuals. Despite huge efforts in determining the molecular pathogenesis of IBD, an increasing worldwide incidence of IBD has been reported. MicroRNAs (miRNAs) are a set of noncoding RNA molecules that are about 22 nucleotides long, and these molecules are involved in the regulation of the gene expression. By clarifying the important role of miRNAs in a number of diseases, their role was also considered in IBD; numerous studies have been performed on this topic. In this review, we attempt to summarize a number of studies and discuss some of the recent developments in the roles of miRNAs in the pathophysiology, diagnosis, and treatment of IBD.

B Cell-Related Circulating MicroRNAs With the Potential Value of Biomarkers in the Differential Diagnosis, and Distinguishment Between the Disease Activity and Lupus Nephritis for Systemic Lupus Erythematosus

Our understanding of circulating microRNAs (miRNAs) related to systemic lupus erythematosus (SLE) remains very limited. In this study, we screened SLE-specific miRNAs in plasma from 42 B cell-related miRNAs by using miRNA PCR Array. The selected miRNAs were first confirmed in plasma samples from 50 SLE patients, 16 rheumatoid arthritis (RA) patients, and 20 healthy donors using qRT-PCR. We then investigated the relationship between expressions of the selected miRNAs and SLE clinical indicators. As a result, 14 miRNAs (miR-103, miR-150, miR-20a, miR-223, miR-27a, miR-15b, miR-16, miR-181a, miR-19b, miR-22, miR-23a, miR-25, miR-92a, and miR-93) were significantly decreased in the plasma of SLE patients compared with healthy controls (P < 0.05) and could act as the diagnostic signature to distinguish SLE patients from healthy donors. Six miRNAs (miR-92a, miR-27a, miR-19b, miR-23a, miR-223, and miR-16) expressed in plasma were significantly lower in SLE patients than in RA patients (P < 0.05), revealing the potentially diagnostic signature to distinguish SLE patients from RA patients. Furthermore, the downregulated expression of miR-19b, miR-25, miR-93, and miR-15b was associated with SLE disease activity (P < 0.05) while miR-15b and miR-22 expressions were significantly lower in SLE patients with low estimate glomerular filtration rate (eGFR < 60 ml/min/1.73 m²) (P < 0.05). The diagnostic potential of miR-15b for SLE disease activity and lupus nephritis (LN) with low eGFR was validated on an independent validation set with 69 SLE patients and a cross-validation set with 80 SLE patients. In summary, the signature of circulating miRNAs will provide novel biomarkers for the diagnosis of SLE and evaluation of disease activity and LN.

Dysregulated MicroRNA Involvement in Multiple Sclerosis by Induction of T Helper 17 Cell Differentiation

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system. Growing evidence has proven that T helper 17 (Th17) cells are one of the regulators of neuroinflammation mechanisms in MS disease. Researchers have demonstrated that some microRNAs (miRNAs) are associated with disease activity and duration, even with different MS patterns. miRNAs regulate CD4⁺ T cells to differentiate toward various T cell subtypes including Th17 cells. In this review, we discuss the possible mechanisms of miRNAs in MS pathophysiology by regulating CD4⁺ T cell differentiation into Th17 cells, and potential miRNA targets for current disease-modifying treatments.

Too sweet to resist: Control of immune cell function by O-GlcNAcylation

O-linked β-N-acetyl glucosamine modification (O-GlcNAcylation) is a dynamic, reversible posttranslational modification of cytoplasmic and nuclear proteins. O-GlcNAcylation depends on nutrient availability and the hexosamine biosynthetic pathway (HBP), which produces the donor substrate UDP-GlcNAc. O-GlcNAcylation is mediated by a single enzyme, O-GlcNAc transferase (OGT), which adds GlcNAc and another enzyme, O-GlcNAcase (OGA), which removes O-GlcNAc from proteins. O-GlcNAcylation controls vital cellular processes including transcription, translation, the cell cycle, metabolism, and cellular stress. Aberrant O-GlcNAcylation has been implicated in various pathologies including Alzheimer's disease, diabetes, obesity, and cancer. Growing evidences indicate that O-GlcNAcylation plays crucial roles in regulating immunity and inflammatory responses, especially under hyperglycemic conditions. This review will highlight the emerging functions of O-GlcNAcylation in mammalian immunity under physiological and various pathological conditions.

Control of T cell effector functions by miRNAs

The differentiation of effector T cells is a tightly regulated process that relies on the selective expression of lineage-defining master regulators that orchestrate unique transcriptional programs, including the production of distinct sets of effector cytokines. miRNAs are post-transcriptional regulators that are now viewed as critical players in these gene expression networks and help defining cell identity and function. This review summarises the role of individual miRNAs in the regulation of the differentiation of effector T cell subsets, including CD4⁺ T helper cells, cytotoxic CD8⁺ T cells and innate-like NKT cells. Moreover, we refer to miRNAs that have been identified to affect simultaneously two or more effector T cell populations, impacting on the balance between effector T cells in vivo, thus constituting potential biomarkers or targets for therapies aiming at boosting immunity or controlling autoimmunity.

MicroRNA 15a/16-1 suppresses aryl hydrocarbon receptor-dependent interleukin-22 secretion in CD4+ T cells and contributes to immune-mediated organ injury

Interleukin-22 (IL-22), as a link between leukocytic and nonleukocytic cells, has gained increasing attention for its pronounced tissue-protective properties. MicroRNAs, emerging as crucial immune modulators, have been reported to be involved in the production and action of various cytokines. However, the precise control of IL-22 by microRNAs and its subsequent actions remained to be elucidated. In this study, we found a negative correlation between the expression of microRNA 15a/16-1 (miR-15a/16-1) and IL-22 in the model of concanavalin A-induced, immune-mediated liver injury. Knockout of miR-15a/16-1 ameliorated liver injury in an IL-22-dependent manner. Further results revealed that cluster of differentiation 4-positive (CD4+ ) T cells were the major source of IL-22 during liver injury and that the aryl hydrocarbon receptor was the direct target of miR-15a/16-1 in CD4+ T cells. In vivo and in vitro data showed that miR-15a/16-1 knockout CD4+ T cells produced more IL-22, while overexpression of miR-15a/16-1 down-regulated the IL-22 production by inhibiting the aryl hydrocarbon receptor. Moreover, transfer of miR-15a/16-1 knockout CD4+ T cells promoted tissue repair compared to wild-type CD4+ T cells by up-regulating IL-22. In addition, as a synergistic effect, IL-22 could down-regulate miR-15a/16-1 expression by activating phosphorylated signal transducer and activator of transcription 3-c-myc signaling, and the decrease of miR-15a/16-1 in damaged hepatocytes contributed to IL-22-mediated tissue repair by reducing cell apoptosis and promoting cell proliferation. As further proof, we demonstrated the role of miR-15a/16-1 in controlling IL-22 production and IL-22-mediated reconstruction of the intestinal epithelial barrier in a dextran sodium sulfate-induced colitis model.

CONCLUSION

Our results suggest that miR-15a/16-1 acts as a essential regulator of IL-22 and that the miR-15a/16-1-aryl hydrocarbon receptor-IL-22 regulatory axis plays a central role in tissue repair; modulation of miR-15a/16-1 might hold promise in developing new strategies to enhance IL-22-mediated tissue repair. (Hepatology 2018;67:1027-1040).

O-GlcNAc: a novel regulator of immunometabolism

The rapidly expanding field of immunometabolism focuses on how metabolism controls the function of immune cells. CD4⁺ T cells are essential for the adaptive immune response leading to the eradication of specific pathogens. However, when T cells are inappropriately over-active, they can drive autoimmunity, allergic disease, and chronic inflammation. The mechanisms by which metabolic changes influence function in CD4⁺ T cells are not fully understood. The post-translational protein modification, O-GlcNAc (O-linked β-N-acetylglucosamine), dynamically cycles on and off of intracellular proteins as cells respond to their environment and flux through metabolic pathways changes. As the rate of O-GlcNAc cycling fluctuates, protein function, stability, and/or localization can be affected. Thus, O-GlcNAc is critically poised at the nexus of cellular metabolism and function. This review highlights the intra- and extracellular metabolic factors that influence CD4⁺ T cell activation and differentiation and how O-GlcNAc regulates these processes. We also propose areas of future research that may illuminate O-GlcNAc's role in the plasticity and pathogenicity of CD4⁺ T cells and uncover new potential therapeutic targets.