Mettl3 inhibits the apoptosis and autophagy of chondrocytes in inflammation through mediating Bcl2 stability via Ythdf1-mediated m⁶A modification.

Abstract

N⁶-methyladenosine (m⁶A) methylation is one of the most common internal modifications in eukaryotic messenger RNA occurring on N⁶ nitrogen of adenosine. However, the roles of m⁶A in temporomandibular joint osteoarthritis (TMJ OA) are still elusive. Here, we investigate the function and mechanism of methyltransferase-like 3 (Mettl3) in chondrocytes in inflammation. We found that the expression of Mettl3 decreased both in vivo TMJ OA mice and in vitro inflammatory stimulation. Functionally, loss and gain studies illustrated that Mettl3 inhibited the apoptosis and autophagy of chondrocytes induced by TNF-α stimulation in vitro. Mettl3 inhibitor, S-adenosylhomocysteine (SAH) promoted the apoptosis and autophagy of chondrocytes with inflammation in vitro and aggravated the degeneration of chondrocytes and subchondral bone in monosodium iodoacetate (MIA) induced TMJ OA mice in vivo. Mechanistically, the bioinformatics analysis, m⁶A-RNA immunoprecipitation (MeRIP) and RNA immunoprecipitation (RIP) were used to identify that Bcl2 mRNA was the downstream target of Mettl3 for m⁶A modification. Furthermore, the results revealed that Yth m⁶A RNA binding protein 1 (Ythdf1) mediated the stability of Bcl2 mRNA catalyzed by Mettl3. Co-immunoprecipitation (Co-IP) showed that Bcl2 protein interacted with Beclin1 protein in chondrocytes induced by TNF-α stimulation. In conclusion, our findings identify that Mettl3 inhibits the apoptosis and autophagy of chondrocytes in inflammation through m⁶A/Ythdf1/Bcl2 signal axis which provides promising therapeutic strategy for TMJ OA.