Afzelin alleviates osteoarthritis by suppressing pyroptosis through decreasing NSUN5-mediated NLRC4 m5C modification.

Abstract

OBJECTIVE: Osteoarthritis (OA) is characterized by the destruction of chondrocytes, in which chondrocyte pyroptosis has been demonstrated to be a key mechanism driving OA progression. 5-Methylcytosine (m5C) modification has been implicated in various biological processes, yet its role in mediating OA remains poorly understood. Afzelin, a natural compound with potent anti-inflammatory properties, but its effects on OA remains uncertain. This study aimed to investigate the therapeutic effects and underlying mechanisms of afzelin in OA. METHODS: C57BL/6 mice underwent a medial meniscotibial ligament transection to induce OA development. Human chondrocytes were stimulated by LPS to induce the OA in vitro model. Both OA in vivo and in vitro model received afzelin treatment. ELISA was performed to evaluate the inflammation in vivo and in vitro. Western blot was performed to detect the levels of pyroptosis-related proteins. The underlying mechanism was investigated by methylated RNA immunoprecipitation (MeRIP), RIP and dual luciferase report. RESULTS: Results showed that afzelin suppressed inflammatory infiltration in the cartilage of OA mice and inhibited the inflammation in bone marrow-derived macrophages extracted from OA mice. Afzelin inhibited the inflammation, pyroptosis and NSUN5 expression in the in vitro OA model, while NSUN5 overexpression reversed these inhibition. Moreover, NSUN5 overexpression enhanced the stability of NLRC4 mRNA by increasing NLRC4 m5C modification. NLRC4 overexpression restored the inflammation and pyroptosis suppressed by NSUN5 knockdown in the in vitro OA model. CONCLUSIONS: These findings suggested that afzelin inhibited OA progression by suppressing pyroptosis through inhibiting NLRC4 expression by downregulating NSUN5. This study provided a new drug and potential target for the treatment of OA.