Holomycin, a novel NLRP3 inhibitor, attenuates cartilage degeneration and inflammation in osteoarthritis

Abstract

The contribution of the NLRP3 inflammasome in osteoarthritis (OA) pathogenesis has been uncovered in recent years. Holomycin (HL) has recently been identified as a novel NLRP3 inflammasome inhibitor. Herein, we aimed to explore the benefits of HL for OA. A chondrocyte-macrophage co-culture system and the destabilization of the medial meniscus (DMM) mouse model were established to study the effect of HL on OA in vitro and in vivo. ECM degradation-related proteins (MMP-13, aggrecan, and Collagen II) were detected by Western blot (WB) and immunohistochemistry (IHC). The chondrocyte senescence was determined by cell cycle, p16 and p21 expressions, and SA-β-Gal staining. The cartilage degeneration was evaluated by OARSI score and Safranin O and H&E staining. Inflammation and NLRP3 inflammasome activation were investigated via RT-PCR, ELISA, WB, and IHC. In vitro studies showed that IL-1β stimulation caused a significant increase of MMP13, p16, p21, and β-galactosidase expressions, a G1-phase arrest, and a down-regulation of aggrecan and Collagen II in chondrocytes, and the increased expressions of IL-6, CXCL-1, IL-1β, NLRP3, and Caspase 1 p20 in both chondrocyte and macrophage. Meanwhile, HL administration could partly reverse these effects induced by IL-1β. In DMM mouse models, intra-articular administration of HL alleviated cartilage degeneration and inflammation, as evidenced by the decrease of OARSI score and MMP13, p16, p21, Collagen II, IL-6, and CXCL-1 expressions and the restoration of chondrocyte number, proteoglycan, and MMP13 expression in cartilage tissues. This study identified HL as a promising agent for OA.