Urolithin A protects mice against osteoarthritis by inhibiting chondrocyte ferroptosis through activating AMPK/mTOR/HIF-1α signaling pathway

Abstract

Urolithin A (UA) is a metabolite of natural polyphenols tannic acid and tannic acid produced by the gut microbiota that has multiple pharmacological effects. However, the effects of UA on osteoarthritis (OA) have not been reported. The aim of this study was to study the effect of UA on OA and clarify the possible mechanism. The mouse OA model was established and the mouse chondrocytes were isolated and cultured. The effect of UA on the cell viability of chondrocytes was tested by MTT assay. The levels of prostaglandin E2 (PGE2), Nitric Oxide (NO), Matrix Metalloproteinase-1 (MMP1), and Matrix Metalloproteinase-3 (MMP3) were measured by the detection kits. The expression of ferroptosis, nuclear factor-kappa B (NF-κB), and Adenosine Monophosphate-Activated Protein Kinase (AMPK) pathway related proteins were detected by western blot. The results showed that UA could attenuate the cartilage tissue injury, MMP1, and MMP3 expression in vivo. UA significantly suppressed PGE2, NO, MMP1, and MMP3 production, and NF-κB activation induced by Interleukin-1 beta (IL-1β). UA attenuated IL-1β-induced MDA, Fe²⁺, and up-regulated glutathione (GSH) production, GPX4, and ferritin expression, which suggested UA could attenuate IL-1β-induced ferroptosis. Furthermore, UA could upregulate the expression of AMPK, and downregulate the expression of mTOR and HIF-1α induced by IL-1β. In addition, AMPK inhibitor compound C prevented the inhibition of UA on IL-1β-induced PGE2, NO, MMP1, MMP3, and ferroptosis. In conclusion, the data indicated that UA exhibited therapeutic effects against OA through inhibiting inflammation and ferroptosis via the AMPK/mTOR/HIF-1α signaling pathway.