METTL3-mediated methylation of RAC2 contributes to cell motility, oxidative stress and inflammation in TNF-α-stimulated rheumatoid arthritis fibroblast-like synovial cells.

[BACKGROUND] Rheumatoid arthritis (RA) is a widely prevalent rheumatic condition causing joint inflammation and damage. RNA methylation plays an important role in RA. Herein, we intended to investigate the function of methyltransferase-like 3 (METTL3) and its N6-methyladenosine (m6A) methylation regulation for ras-related C3 botulinum toxin substrate 2 (RAC2) in RA.

[METHODS] MH7A cells were treated with TNF-α to establish RA cell model. The expression analysis was performed by RT-qPCR and western blot. Cellular behaviors were examined by CCK-8 assay, flow cytometry, wound healing assay and transwell assay. Oxidative stress was assessed by detecting the associated indicators. Inflammatory cytokines were measured via enzyme-linked immunosorbent assay (ELISA). Interaction between METTL3 and RAC2 was analyzed via RNA immunoprecipitation (RIP) assay and MeRIP assay.

[RESULTS] RAC2 was highly expressed in RA tissues and TNF-α-stimulated MH7A cells. Knockdown of RAC2 enhanced apoptosis and reduced proliferation, migration, invasion after TNF-α treatment. RAC2 downregulation suppressed oxidative stress and inflammatory response in TNF-α-treated MH7A cells. METTL3 promoted RAC2 expression through m6A methylated modification, and METTL3/RAC2 could activate AKT pathway. RAC2 overexpression reversed the effects of METTL3 knockdown on cell proliferation, motility, oxidative stress and inflammation.

[CONCLUSION] The above results demonstrated that METTL3 facilitated the progression of RA via downregulating RAC2 in an m6A dependent mechanism in TNF-α-treated MH7A cells.