Demethylation of MicroRNA-124a Genes Attenuated Proliferation of Rheumatoid Arthritis Derived Fibroblast-Like Synoviocytes and Synthesis of Tumor Necrosis Factor-α

Exposome: Epigenetics and autoimmune diseases

Systemic autoimmune diseases are complex conditions characterized by an immune system dysregulation and an aberrant activation against self-antigens, leading to tissue and organ damage. Even though genetic predisposition plays a role, it cannot fully explain the onset of these diseases, highlighting the significant impact of non-heritable influences such as environment, hormones and infections. The exposome represents all those factors, ranging from chemical pollutants and dietary components to psychological stressors and infectious agents. Epigenetics, which studies changes in gene expression without altering the DNA sequence, is a crucial link between exposome and the development of autoimmune diseases. Key epigenetic mechanisms include DNA methylation, histone modifications, and non-coding RNAs. These epigenetic modifications could provide a potential piece of the puzzle in understanding systemic autoimmune diseases and their connection with the exposome. In this work we have collected the most important and recent evidence in epigenetic changes linked to systemic autoimmune diseases (systemic lupus erythematosus, idiopathic inflammatory myopathies, ANCA-associated vasculitis, and rheumatoid arthritis), emphasizing the roles these changes may play in disease pathogenesis, their potential as diagnostic biomarkers and their prospective in the development of targeted therapies.

Exploring regulatory mechanisms on miRNAs and their implications in inflammation-related diseases

This comprehensive exploration delves into the pivotal role of microRNAs (miRNAs) within the intricate tapestry of cellular regulation. As potent orchestrators of gene expression, miRNAs exhibit diverse functions in cellular processes, extending their influence from the nucleus to the cytoplasm. The complex journey of miRNA biogenesis, involving transcription, processing, and integration into the RNA-induced silencing complex, showcases their versatility. In the cytoplasm, mature miRNAs finely tune cellular functions by modulating target mRNA expression, while their reach extends into the nucleus, influencing transcriptional regulation and epigenetic modifications. Dysregulation of miRNAs becomes apparent in various pathologies, such as cancer, autoimmune diseases, and inflammatory conditions. The adaptability of miRNAs to environmental signals, interactions with transcription factors, and involvement in intricate regulatory networks underscore their significance. DNA methylation and histone modifications adds depth to understanding the dynamic regulation of miRNAs. Mechanisms like competition with RNA-binding proteins, sponging, and the control of miRNA levels through degradation and editing contribute to this complex regulation process. In this review, we mainly focus on how dysregulation of miRNA expression can be related with skin-related autoimmune and autoinflammatory diseases, arthritis, cardiovascular diseases, inflammatory bowel disease, autoimmune and autoinflammatory diseases, and neurodegenerative disorders. We also emphasize the multifaceted roles of miRNAs, urging continued research to unravel their complexities. The mechanisms governing miRNA functions promise advancements in therapeutic interventions and enhanced insights into cellular dynamics in health and disease.

Comprehensive overview of microRNA function in rheumatoid arthritis

MicroRNAs (miRNAs), a class of endogenous single-stranded short noncoding RNAs, have emerged as vital epigenetic regulators of both pathological and physiological processes in animals. They direct fundamental cellular pathways and processes by fine-tuning the expression of multiple genes at the posttranscriptional level. Growing evidence suggests that miRNAs are implicated in the onset and development of rheumatoid arthritis (RA). RA is a chronic inflammatory disease that mainly affects synovial joints. This common autoimmune disorder is characterized by a complex and multifaceted pathogenesis, and its morbidity, disability and mortality rates remain consistently high. More in-depth insights into the underlying mechanisms of RA are required to address unmet clinical needs and optimize treatment. Herein, we comprehensively review the deregulated miRNAs and impaired cellular functions in RA to shed light on several aspects of RA pathogenesis, with a focus on excessive inflammation, synovial hyperplasia and progressive joint damage. This review also provides promising targets for innovative therapies of RA. In addition, we discuss the regulatory roles and clinical potential of extracellular miRNAs in RA, highlighting their prospective applications as diagnostic and predictive biomarkers.

Effect of miR124a on collageninduced arthritis in mice and the underlying mechanisms

OBJECTIVES

Rheumatoid arthritis (RA) is a chronic autoimmune disease. MicroRNA has been shown to play an important role in RA. MicroRNA-124a (miR-124a) has anti-proliferative and anti-inflammatory effects in RA fibroblast synovial cells. This study aims to explore the effects of miR-124a overexpression on arthritis in collagen-induced arthritis (CIA) mice and the underlying mechanisms.

METHODS

Bovine type II collagen and complete Ferris adjuvant were used to induce CIA model from DBA/1 mice. Twenty-eight days after initial immunization (D28), CIA mice were randomly divided into a model group, a miR-124a treatment group, and a negative control (NC) group. Physiological saline, miR-124a agomir, and miR-124a agomir NC were injected into the skin at the tail root of mice every 3 days for 4 times, respectively. The degree of joint swelling and arthritis index of mice were recorded accordingly. Sixty-three days after initial immunization (D63), the mice were sacrificed to obtain the synovial tissue of ankle joint. HE staining was used to observe the proliferation of synovial cell, infiltration of inflammatory cell, pannus, and bone erosion of synovial tissues; TUNEL staining was used to detect cell apoptosis; qRT-PCR was used to detect the mRNA expression of miR-124a, phosphatidylinositol-3-kinase catalytic subunit alpha (PIK3CA) and its downstream genes Bcl-2 and Bax. Immunohistochemistry was used to detect the protein expression of PIK3CA, Bcl-2, and Bax protein in synovial tissues of each group.

RESULTS

Different degrees of swelling presented in the paws of DBA/1 mice at D28, which indicated the CIA model was constructed successfully. Forty-eight days after initial immunization (D48), the paws of mice in the miR-124a treatment group were only slightly red and swollen, while the paws of mice in the model group and the NC group were obviously red and swollen. The arthritis index of mice in the miR-124a treatment group were decreased significantly compared to the NC group at D51, D53, D59, and D62 (51, 53, 59, 62 days after initial immunization) (all P<0.05). Sixty-three days after initial immunization (D63), HE staining indicated that the scores of synovial cell proliferation, inflammatory cell infiltration, synovial pannus, and bone erosion were significantly reduced in the miR-124a treatment group (P<0.05 or P<0.01), while cell apoptosis was increased in the miR-124a treatment group compared with the model group and NC group (P<0.01 or P<0.001). Besides, the expression of miR-124a and Bax in the synovial tissue in miR-124a treatment group was significantly higher than those in the model group and NC group (P<0.01 or P<0.001), while the expressions of PIK3CA and Bcl-2 were decreased (P<0.05 or P<0.01 or P<0.001), and the ratio of Bcl-2 to Bax was significantly decreased (P<0.01 or P<0.001).

CONCLUSIONS

Overexpression of miR-124a can reduce arthritis in CIA mice bacause it could promote synovial cell apoptosis and inhibit synovial cell proliferation via targeting PIK3CA and regulating its downstream pathways.

LncRNA Expression Profiles in Systemic Lupus Erythematosus and Rheumatoid Arthritis: Emerging Biomarkers and Therapeutic Targets

Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are two common multisystem autoimmune diseases that share, among others, many clinical manifestations and serological features. The role of long non-coding RNAs (lncRNAs) has been of particular interest in the pathogenesis of autoimmune diseases. Here, we aimed to summarize the roles of lncRNAs as emerging novel biomarkers and therapeutic targets in SLE and RA. We conducted a narrative review summarizing original articles on lncRNAs associated with SLE and RA, published until November 1, 2021. Based on the studies on lncRNA expression profiles in samples (including PBMCs, serum, and exosomes), it was noted that most of the current research is focused on investigating the regulatory mechanisms of these lncRNAs in SLE and/or RA. Several lncRNAs have been hypothesized to play key roles in these diseases. In SLE, lncRNAs such as GAS5, NEAT1, TUG1, linc0949, and linc0597 are dysregulated and may serve as emerging novel biomarkers and therapeutic targets. In RA, many validated lncRNAs, such as HOTAIR, GAS5, and HIX003209, have been identified as promising novel biomarkers for both diagnosis and treatment. The shared lncRNAs, for example, GAS5, may participate in SLE pathogenesis through the mitogen-activated protein kinase pathway and trigger the AMP-activated protein kinase pathway in RA. Here, we summarize the data on key lncRNAs that may drive the pathogenesis of SLE and RA and could potentially serve as emerging novel biomarkers and therapeutic targets in the coming future.

Effects of Treatment with the Hypomethylating Agent 5-aza-2'-deoxycytidine in Murine Type II Collagen-Induced Arthritis

The emerging role of epigenetics in the pathogenesis of autoimmune diseases has recently attracted much interest on the possible use of epigenetic modulators for the prevention and treatment of these diseases. In particular, we and others have shown that drugs that inhibit DNA methylation, such as azacitidine (AZA) and decitabine (DAC), already used for the treatment of acute myeloid leukemia, exert powerful beneficial effects in rodent models of type 1 diabetes, multiple sclerosis, and Guillain Barrè syndrome. Along this line of research, we have presently studied the effects of DAC in a murine model of rheumatoid arthritis induced by type II collagen and have demonstrated that DAC administration was associated with a significant amelioration of the clinical condition, along with in vivo and ex vivo modification of the immunological profile of the so-treated mice, that exhibited a diminished production of Th1 and Th17 pro-inflammatory cytokines and reduction of anti-type II collagen autoantibodies.

Recent findings regarding the effects of microRNAs on fibroblast-like synovial cells in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease with severe joint inflammation and destruction characterized by marked hyperplasia of the lining layer of the synovium. Fibroblast-like synovial cells (FLS) is a key cellular component within the synovia; it plays pivotal roles in RA pathogenesis by unfavorable behaviors such as producing inflammatory cytokines and chemokines, and hyperproliferation. MicroRNAs are evolutionarily conserved small non-coding RNAs (length is 18-25 nucleotides) that regulate gene expression at the post-transcriptional level. There is increasing interest in the involvement of microRNAs in autoimmune diseases including RA. Recent studies revealed the regulation of the function of FLS by microRNAs. Here, we review the known functional microRNAs in RA and summarize the potential uses of these small molecules in the treatment of RA.

MicroRNAs in rheumatoid arthritis: From pathogenesis to clinical impact

Over the last decade, many epigenetic mechanisms that contribute in the pathogenesis of autoimmune disorders have been revealed. MicroRNAs (miRNAs) are small, non-coding, RNA molecules that bind to messenger RNAs and disrupt the transcription of target genes. Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease in which a plethora of epigenetic changes take place. Current research on RA epigenetics has focused mainly on miRNAs. Genetic variance of some miRNA genes, especially miR-499, might predispose an individual to RA development. Additionally, altered expression of many miRNAs has been discovered in several cells, tissues and body fluids in patients with RA. MiRNAs expression also differs depending on disease's stage and activity. Serum miR-22 and miR-103a might predict RA development in susceptible individuals (pre-RA), while serum miR-16, miR-24, miR-125a and miR-223 levels are altered in early RA (disease duration <12 months) patients compared to established RA or healthy individuals. Moreover, serum miR-223 levels have been associated with RA activity and disease relapse. What is more, serum levels of several miRNAs, including miR-125b and miR-223, could be used to predict response to RA treatment. Finally, miRNA analogs or antagonists have been used as therapeutic regimens in experimental arthritis models and have demonstrated promising results. In conclusion, the research on the miRNA alterations in RA sheds light to several aspects of RA pathogenesis, introduces new biomarkers for RA diagnosis and treatment response prediction and offers the opportunity to discover new, targeted drugs for patients with RA.

Epigenetic Changes in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease that affects about 1% of the world’s population. The etiology of RA remains unknown. It is considered to occur in the presence of genetic and environmental factors. An increasing body of evidence pinpoints that epigenetic modifications play an important role in the regulation of RA pathogenesis. Epigenetics causes heritable phenotype changes that are not determined by changes in the DNA sequence. The major epigenetic mechanisms include DNA methylation, histone proteins modifications and changes in gene expression caused by microRNAs and other non-coding RNAs. These modifications are reversible and could be modulated by diet, drugs, and other environmental factors. Specific changes in DNA methylation, histone modifications and abnormal expression of non-coding RNAs associated with RA have already been identified. This review focuses on the role of these multiple epigenetic factors in the pathogenesis and progression of the disease, not only in synovial fibroblasts, immune cells, but also in the peripheral blood of patients with RA, which clearly shows their high diagnostic potential and promising targets for therapy in the future.

miR-124a inhibits the proliferation and inflammation in rheumatoid arthritis fibroblast-like synoviocytes via targeting PIK3/NF-κB pathway

Abnormal hyperplasia of fibroblast-like synoviocytes (FLS) leads to the progression of rheumatoid arthritis (RA). This study aimed to investigate the role of miR-124a in the pathogenesis of RA. The viability and cell cycle of FLS in rheumatoid arthritis (RAFLS) were evaluated by Cell Counting Kit 8 and flow cytometry assay. The expression of PIK3CA, Akt, and NF-κB in RAFLS was examined by real-time PCR and Western blot analysis. The production of tumour necrosis factor (TNF)-α and interleukin (IL)-6 was detected by ELISA. The joint swelling and inflammation in collagen-induced arthritis (CIA) mice were examined by histological and immunohistochemical analysis. We found that miR-124a suppressed the viability and proliferation of RAFLS and increased the percentage of cells in the G1 phase. miR-124a suppressed PIK3CA 3'UTR luciferase reporter activity and decreased the expression of PIK3CA at mRNA and protein levels. Furthermore, miR-124a inhibited the expression of the key components of the PIK3/Akt/NF-κB signal pathway and inhibited the expression of pro-inflammatory factors TNF-α and IL-6. Local overexpression of miR-124a in the joints of CIA mice inhibited inflammation and promoted apoptosis in FLS by decreasing PIK3CA expression. In conclusion, miR-124a inhibits the proliferation and inflammation in RAFLS via targeting PIK3/NF-κB pathway. miR-124a is a promising therapeutic target for RA.

Blood Serum From Head and Neck Squamous Cell Carcinoma Patients Induces Altered MicroRNA and Target Gene Expression Profile in Treated Cells

The head and neck squamous cell carcinoma (HNSCC) represents one of the most common cancers in humans. Close to 600,000 new diagnoses are made every year worldwide and over half of diagnosed patients will not survive. In view of this low survival rate, the development of novel cell-based assays for HNSCC will allow more mechanistic approaches for specific diagnostics for each individual patient. The cell-based assays will provide more informative data predicting cellular processes in treated patient, which in effect would improve patient follow up. More importantly, it will increase the specificity and effectiveness of therapeutic approaches. In this study, we investigated the role of serum from HNSCC patients on the regulation of microRNA (miRNA) expression in exposed cells in vitro. Next-generation sequencing of miRNA revealed that serum from HNSCC patients induced a different miRNA expression profile than the serum from healthy individuals. Out of 377 miRNA detected, we found that 16 miRNAs were differentially expressed when comparing cells exposed to serum from HNSCC or healthy individuals. The analysis of gene ontologies and pathway analysis revealed that these miRNA target genes were involved in biological cancer-related processes, including cell cycle and apoptosis. The real-time PCR analysis revealed that serum from HNSCC patients downregulate the expression level of five genes involved in carcinogenesis and two of these genes-P53 and SLC2A1-are direct targets of detected miRNAs. These novel findings provide new insight into how cancer-associated factors in circulation regulate the expression of genes and regulatory elements in distal cells in favor of tumorigenesis. This has the potential for new therapeutic approaches and more specific diagnostics with tumor-specific cell lines or single-cell in vitro assays for personalized treatment and early detection of primary tumors or metastasis.

The Effects of MicroRNAs on Key Signalling Pathways and Epigenetic Modification in Fibroblast-Like Synoviocytes of Rheumatoid Arthritis

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at the posttranscriptional level via direct binding to the 3′-untranslated region (UTR) of target mRNAs. Emerging evidence shows that miRNAs play crucial roles in controlling and modulating immune system-related diseases. This review focuses on the role played by miRNAs in fibroblast-like synoviocytes (FLS), which is a key cellular component within synovia, during the establishment and maintenance of rheumatoid arthritis (RA), a systemic inflammatory autoimmune disease. It also provides an overview and classification of known functional miRNAs in RA FLS and summarizes the potential uses of these small molecules in RA diagnosis and treatment.

Dysregulation of microRNAs in autoimmune diseases: Pathogenesis, biomarkers and potential therapeutic targets

MicroRNAs (miRNAs) are small, single-stranded, endogenous non-coding RNAs that repress the expression of target genes via post-transcriptional mechanisms. Due to their broad regulatory effects, the precisely regulated, spatial-specific and temporal-specific expression of miRNAs is fundamentally important to various biological processes including the immune homeostasis and normal function of both innate and adaptive immune response. Aberrance of miRNAs is implicated in the development of various human diseases, especially cancers. Increasing evidence has revealed a dysregulated expression pattern of miRNAs in autoimmune diseases, among which many play key roles in the pathogenesis. In this review we summarize these findings on miRNA dysregulation implicated in autoimmune diseases, focusing on four representative systemic autoimmune diseases, i.e. systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis and dermatomyositis. The causes of the dysregulation of miRNA expression in autoimmune diseases may include genetic and epigenetic variants, and various environmental factors. Further understanding of miRNA dysregulation and its mechanisms during the development of different autoimmune diseases holds enormous potential to bring about novel therapeutic targets or strategies for these complex human disorders, as well as novel circulating or exosomal miRNA biomarkers.

Identification of miR‑124a as a novel diagnostic and prognostic biomarker in non‑small cell lung cancer for chemotherapy

Previous studies have suggested that dysregulation of microRNA (miR) −124a is associated with various types of human cancer. However, there are few studies reporting the level of miR-124a expression in non-small cell lung cancer (NSCLC). The present study investigated the association between miR-124a and NSCLC by analyzing the differential expression of miR-124a in NSCLC using the GEO database, as well as subsequently performing reverse transcription-quantitative polymerase chain reaction analysis on 160 NSCLC biopsies, 32 of which were paired with adjacent normal tissues. The results indicated that mir-124a expression levels were decreased in NSCLC tumor biopsies compared with adjacent normal tissues. The overall survival (OS) in patients with a high expression of miR-124a was prolonged relative to patients with low expression of miR-124a. The expression levels of miR-124a were associated with clinical characteristics, including lymph-node metastasis, tumor differentiation, tumor node metastasis (TNM) stage and diameter. Frequently, lymph-node metastasis, TNM stage, diameter and lack of chemotherapy have been associated with a worse prognosis in patients. In addition, the present study identified that high expression of miR-124awith chemotherapy may increase OS. In conclusion, the current study demonstrated that miR-124a was downregulated in NSCLC, and miR-124a was a potential prognostic tumor biomarker response to chemotherapy.