The objective of this study is to explore the specific roles of a crucial N6-methyladenosine (m6A) methyltransferase, methyltransferase-like 14 (METTL14), in fibroblast-like synoviocytes (FLSs) activation of rheumatoid arthritis (RA). RA rat model was induced by administering intraperitoneally collagen antibody alcohol. Primary fibroblast-like synoviocytes (FLSs) were isolated from joint synovium tissues in rats. shRNA transfection tools were used to downregulate METTL14 expression in vivo and vitro. The injury of joint synovium was shown by hematoxylin and eosin (HE) staining. The cell apoptosis of FLSs was determined by flow cytometry. The levels of IL-6, IL-18, and C-X-C motif chemokine ligand (CXCL)10 in serum and culture supernatants were measured by ELISA kits. The expressions of LIM and SH3 domain protein 1 (LASP1), p-SRC/SRC, and p-AKT/AKT in FLSs and joint synovium tissues were determined by Western blots. The expression of METTL14 was greatly induced in the synovium tissues of RA rats compared with normal control rats. Compared with sh-NC-treated FLSs, METTL14 knockdown significantly increased cell apoptosis, inhibited cell migration and invasion, and suppressed the production of IL-6, IL-18, and CXCL10 induced by TNF-α. METTL14 silencing suppresses the expression of LASP1 and the activation of Src/AKT axis induced by TNF-α in FLSs. METTL14 improves the mRNA stability of LASP1 through m6A modification. In contrast, these were reversed by LASP1 overexpression. Moreover, METTL14 silencing clearly alleviates FLSs activation and inflammation in a RA rat model. These results suggested that METTL14 promotes FLSs activation and related inflammatory response via the LASP1/SRC/AKT signaling pathway and identified METTL14 as a potential target for treating RA.
Keywords: LASP1; METTL14; fibroblast-like synoviocytes; m6A methylation; rheumatoid arthritis.