Emapunil relieves osteoarthritis by regulating the CD14/TLR4/LY96 pathway in synovial macrophages through translocator protein 18 kDa.

OBJECTIVE: Osteoarthritis (OA), the most prevalent chronic degenerative joint disease, lacks effective therapies due to unclear pathogenesis. This study investigated the effects and mechanisms of translocator protein 18 kDa (TSPO) and its ligand emapunil in OA.

METHODS: TSPO expression was assessed in synovium, macrophages, and cartilage from OA mice and patients. Macrophages TSPO was manipulated via plasmid and siRNA to evaluate polarization and inflammatory responses. Molecular docking was applied to evaluate TSPO affinity was validated by molecular docking, and its therapeutic effects were tested in vitro and in vivo. RNA sequencing analyzed Lipopolysaccharide (LPS)-induced M1 macrophages treated with Emapunil.

RESULTS: TSPO was upregulated in OA synovium (particularly macrophages) but was unchanged in cartilage. Overexpression promoted M1 polarization and proinflammatory cytokine release, while TSPO inhibition showed no significant effects. Emapunil, a potent TSPO ligand, suppressed LPS-induced M1 polarization, reduced proinflammatory cytokines, and alleviated chondrocyte destruction. Intraperitoneal Emapunil attenuated synovitis and cartilage erosion in OA mice, lowering synovitis and Osteoarthritis Research Society International scores, reducing M1 macrophages and MMP13, while increasing COL2. Mechanistically, Emapunil downregulated CD14/LY96 mRNA via TSPO, inhibiting NF-κB/TLR signaling and M1 polarization. TSPO inhibition abolished Emapunil's regulatory effects on CD14/TLR4/LY96 pathways.

CONCLUSION: TSPO plays an important role in OA occurrence and development. Emapunil targeting TSPO improves OA by modulating macrophage polarization and inflammation through the CD14/TLR4/LY96 pathway.