Quercetin as a promising intervention for rat osteoarthritis by decreasing M1‐polarized macrophages via blocking the TRPV1‐mediated P2X7/NLRP3 signaling pathway

Abstract Osteoarthritis (OA) is characterized by an imbalance between M1 and M2 polarized synovial macrophages. Quercetin has shown protective effects against OA by altering M1/M2‐polarized macrophages, but the underlying mechanisms remain unclear. In this study, rat chondrocytes were treated with 10 ng/mL of IL‐1β. To create M1‐polarized macrophages in vitro, rat bone marrow‐derived macrophages (rBMDMs) were treated with 100 ng/mL LPS. To mimic OA conditions observed in vivo, a co‐culture system of chondrocytes and macrophages was established. ATP release assays, immunofluorescence assays, Fluo‐4 AM staining, Transwell assays, ELISA assays, and flow cytometry were performed. Male adult Sprague–Dawley (SD) rats were used to create an OA model. Histological analyses, including H&E, and safranin O‐fast green staining were performed. Our data showed a quercetin‐mediated suppression of calcium ion influx and ATP release, with concurrent downregulation of TRPV1 and P2X7 in the chondrocytes treated with IL‐1β. Activation of TRPV1 abolished the quercetin‐mediated effects on calcium ion influx and ATP release in chondrocytes treated with IL‐1β. In the co‐culture system, overexpression of P2X7 in macrophages attenuated the quercetin‐mediated effects on M1 polarization, migration, and inflammation. Either P2X7 or NLRP3 knockdown attenuated IL‐1β‐induced M1/M2 polarization, migration, and inflammation. Moreover, overexpression of TRPV1 reduced the quercetin‐mediated suppressive effects on OA by promoting M1/M2‐polarized macrophages in vivo. Collectively, our data showed that quercetin‐induced suppression of TRPV1 leads to a delay in OA progression by shifting the macrophage polarization from M1 to M2 subtypes via modulation of the P2X7/NLRP3 pathway.