Quercetin Alleviates Osteoarthritis Progression in Rats by Suppressing Inflammation and Apoptosis via Inhibition of IRAK1/NLRP3 Signaling.

Abstract

IntroductionQuercetin was recently reported to help protect against osteoarthritis (OA) progression, but the molecular mechanism for that protective affect remains unclear.MethodsHere, OA model rats were intraperitoneally injected with quercetin, and the severity of cartilage damage in the rats was evaluated by H&E, Safranin O, and Toluidine blue, as well as by using the Osteoarthritis Research Society International (OARSI) Scoring System. Additionally, rat chondrocytes were treated with quercetin and then stimulated with IL-1β. The levels of pro-inflammatory cytokines (IL-1β, IL-18, and TNF-α) were detected by ELISA.Cell apoptosis was evaluated by flow cytometry and Hoechst staining. ROS levels were measured using a DCFH-DA probe. Protein expression was evaluated by Western blotting, immunohistochemical staining, and immunofluorescence. ResultsOur data showed that quercetin attenuated the degeneration and erosion of articular cartilage, suppressed inflammation and apoptosis, and downregulated the levels of IRAK1, NLRP3, and caspase-3 expression. In vitro data showed that overexpression of NLRP3 could reverse the suppressive effect of quercetin on IL-1β-induced rat chondrocyte injuries. Importantly, rescue experiments confirmed that quercetin inhibited IL-1β-induced rat chondrocyte injuries in vitro by suppressing the IRAK1/NLRP3 signaling pathway.ConclusionOur study indicated that quercetin inhibits IL-1β-induced inflammation and cartilage degradation by suppressing the IRAK1/NLRP3 signaling pathway.