VX-11e protects articular cartilage and subchondral bone in osteoarthritis by inhibiting the RIP1/RIP3/MLKL and MAPK signaling pathways

Necroptosis of chondrocytes contributes to the progression of osteoarthritis (OA). Recent studies have shown that VX-11e, an ERK inhibitor, exhibited a contrasting expression pattern to RIP3, the key protein of necroptosis. However, its effect on OA remains to be determined. Therefore, we investigated whether VX-11e affected the loss of articular cartilage and subchondral bone during OA. In in vivo experiments, a mouse OA model induced by medial meniscus instability (destabilization of the medial meniscus [DMM]) was used. In in vitro experiments, interleukin-1β (IL-1β) was used to simulate the inflammatory microenvironment of chondrocytes, and RANKL was used to induce osteoclast differentiation. Histological analysis, cell viability experiments, high-density cell culture experiments, immunofluorescence assay, western blot assay, quantitative PCR, and molecular docking experiments were conducted to determine the protective effect of VX-11e on articular cartilage during OA. We also performed histological analysis, tartrate-resistant acid phosphatase (TRAP) staining, F-actin ring formation test, quantitative PCR, and western blot assay to study the effect of VX-11e on subchondral bone during OA progression. We found that after the medial meniscus was severed, the articular cartilage of the mice showed pathological changes, accompanied with the loss of subchondral bone. However, an intraperitoneal injection of VX-11e protected the cartilage and subchondral bone of the mouse knee joint. The results of in vitro experiments showed that VX-11e promoted the anabolism of the extracellular matrix of chondrocytes by inhibiting the expression and phosphorylation of RIP3 and MLKL. VX-11e also inhibited RANKL-induced osteoclast differentiation by inhibiting the ERK/RSK signaling pathway, but not the NF-κB pathway. Overall, VX-11e inhibited the loss of articular cartilage and subchondral bone during OA by regulating the RIP1/RIP3/MLKL and MAPK signaling pathways.