Skatole attenuates osteoarthritis by protecting chondrocytes and mediating macrophage repolarization through regulating the NFκB/MAPK signaling pathway and metabolic reprogramming

Osteoarthritis (OA) is the most common joint disease, but there are currently no disease-modifying OA drugs (DMOADs) yet approved by the regulatory agencies. Regulating macrophage polarization can alleviate synovial inflammation and then repair articular cartilage damage, providing a new target for OA treatment. Here, we found that Skatole can modulate macrophage polarization and attenuate OA. Skatole hindered M1 macrophage polarization while promoting M2 macrophage polarization. Mechanistically, Skatole activated Stat6, suppressed the phosphorylation of IKK, IκBα, and p65 in NFκB signaling pathway, and inhibited MAPK signaling activation. RNA-seq analysis revealed that Skatole downregulated the expression of inflammation-related genes, while upregulating genes involved in glutathione metabolism and oxidative phosphorylation, thereby reducing ROS levels and inhibiting M1 macrophage polarization. Moreover, conditional medium (CM) from M1 macrophages treated with Skatole balanced anabolism and catabolism in mouse chondrocytes while inhibiting cell apoptosis. Intriguingly, in IL1β-treated chondrocytes, Skatole directly suppressed inflammation and catabolism, without significantly affecting cell apoptosis or anabolism; In vivo experiments showed that Skatole increased M2 polarization and decreased M1 polarization of synovial macrophages, alleviated synovitis, and lessend articular cartilage damage in destabilization of medial meniscus (DMM)-induced OA mice. Our finding suggest that Skatole has the potential to function as a DMOAD.