ALKBH5-YTHDF2 m6A modification axis inhibits rheumatoid arthritis progression by suppressing NLRP3

Increased m6A RNA methylation and METTL3 expression may contribute to the synovitis progression of rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial hyperplasia and progressive bone destruction. The tumor-like growth of fibroblast-like synoviocytes (FLSs) plays a crucial role in the pathogenesis of RA. The N6 methyladenine (m6A) mRNA methylation modification, regulated by methyltransferases (METTL3) and demethylation enzymes, is a novel epigenetic regulator in the development of RA. However, there is limited research on m6A methylation modifications in RA synovitis and a lack of mechanistic studies on their impact on the function of RA-FLSs.

METHODS

This study utilized clinical synovial tissue specimens and FLSs as research subjects. The m6A methylation level and the expression of methyltransferases and demethylation enzymes were detected. RNA interference and gene overexpression methods were employed to investigate the mechanism of METTL3 in RA-FLSs. The study also examined the proliferation, apoptosis, migration, invasion, and cytokine levels of RA-FLSs, as well as the expression of METTL3 in RA animal models.

RESULTS

In this study, we found that m6A methylation levels were elevated in synovial tissues and FLSs of RA patients. Immunohistochemical staining showed that METTL3 and METTL14 levels were up-regulated in synovial tissues of RA, the mRNA levels of METTL3, METTL14, WTAP, FTO, and ALKBH5 were significantly higher in synovial tissues and FLSs of RA patients. Overexpression of METTL3 could promote the proliferation, migration, and secretion of IL-6, RANKL of RA-FLSs; inhibition of METTL3 expression could inhibit the abnormal proliferation, migration, invasion, and secretion of IL-6, RANKL, at the same time promoted the apoptosis and secretion of OPG, thus inhibited RA-FLSs tumor-like growth. In CIA mice, the use of MTX and STM2457 reduced METTL3 expression, synovial hyperplasia and bone destruction.

CONCLUSION

Abnormal modification of m6A methylation exists in synovial tissues and FLSs of RA patients, and inhibition of METTL3 can reduce synovitis and bone destruction. Our findings suggest that m6A methylation might control FLS-mediated tumor-like phenotype, and be a novel target for RA treatment.

METTL3 knockdown suppresses RA-FLS activation through m6A-YTHDC2-mediated regulation of AMIGO2

The dysregulation of N6-methyladenosine (m6A) on mRNAs is involved in the pathogenesis of rheumatoid arthritis (RA). Methyltransferase-like 3 (METTL3), serving as a central m6A methyltransferase, is highly expressed in macrophages, synovial tissues and RA fibroblast-like synoviocytes (RA-FLS) of RA patients. However, METTL3-mediated m6A modification on target mRNAs and the molecular mechanisms involved in RA-FLS remain poorly defined. Our research demonstrated that METTL3 knockdown decreased the proliferation, migratory and invasive abilities of RA-FLS. Notably, we identified the adhesion molecule with Ig like domain 2 (AMIGO2) as a probable downstream target of both METTL3 and YTH Domain Containing 2 (YTHDC2) in RA-FLS. We revealed that AMIGO2 augmented the activation of RA-FLS and can potentially reverse the phenotypic effects induced by the knockdown of either METTL3 or YTHDC2. Mechanistically, METTL3 knockdown decreased m6A modification in the 5'-untranslated region (5'UTR) of AMIGO2 mRNA, which diminished its interaction with YTHDC2 in RA-FLS. Our findings unveiled that silencing of METTL3 inhibited the proliferation and aggressive behaviors of RA-FLS by downregulating AMIGO2 expression in an m6A-YTHDC2 dependent mechanism, thereby underscoring the pivotal role of the METTL3-m6A-YTHDC2-AMIGO2 axis in modulating RA-FLS phenotypes.

Recent advances of m6A methylation in skeletal system disease

Skeletal system disease (SSD) is defined as a class of chronic disorders of skeletal system with poor prognosis and causes heavy economic burden. m6A, methylation at the N6 position of adenosine in RNA, is a reversible and dynamic modification in posttranscriptional mRNA. Evidences suggest that m6A modifications play a crucial role in regulating biological processes of all kinds of diseases, such as malignancy. Recently studies have revealed that as the most abundant epigentic modification, m6A is involved in the progression of SSD. However, the function of m6A modification in SSD is not fully illustrated. Therefore, make clear the relationship between m6A modification and SSD pathogenesis might provide novel sights for prevention and targeted treatment of SSD. This article will summarize the recent advances of m6A regulation in the biological processes of SSD, including osteoporosis, osteosarcoma, rheumatoid arthritis and osteoarthritis, and discuss the potential clinical value, research challenge and future prospect of m6A modification in SSD.

Emerging roles and mechanism of m6A methylation in rheumatoid arthritis

Rheumatoid arthritis (RA) is a multifaceted autoimmune disease characterized by systemic inflammation, affecting both articular and extra-articular structures. This condition results in inflammation of joints and synovial membranes, accompanied by the development of systemic comorbidities. Despite extensive research, the precise pathogenic mechanisms responsible for RA have yet to be completely understood. RNA methylation, a burgeoning epigenetic alteration, assumes a pivotal function in the regulation of a myriad of biological phenomena, encompassing immunity, DNA damage response, tumorigenesis, metastasis, stem cell renewal, adipocyte differentiation, circadian rhythms, cellular development and differentiation, and cell division. The N6-methyladenosine (m6A) modification is the most prevalent among the various RNA modifications found in mammalian mRNA. Recent studies have provided evidence of the significant role played by m6A modification in the pathophysiological progression of RA. This review aims to provide a comprehensive analysis of the progress made in research focused on m6A modification in the context of RA, consolidate the underlying mechanisms involved in m6A modification during the initiation of RA and discuss the potential of targeting m6A modification as a viable therapeutic approach for RA.