Asperosaponin VI suppresses ferroptosis in chondrocytes and ameliorates osteoarthritis by modulating the Nrf2/GPX4/HO-1 signaling pathway.

BACKGROUND: Asperosaponin VI (AVI) is a naturally occurring monosaccharide derived from Dipsacus asperoides renowned for its anti-inflammatory and bone-protective properties. OBJECTIVE: To elucidate the specific mechanism through which AVI affects chondrocytes in osteoarthritis (OA). METHODS: For the in vitro experiments, primary chondrocytes were to elucidate the molecular mechanisms underlying the action of AVI.For the in vivo experiments, rat OA models were established using a modified Hulth method. The severity of knee osteoarthritis was evaluated 8 weeks post-surgery. Micro-CT imaging, hematoxylin-eosin staining, and Safranin O-fast green staining were used to assess degeneration in rat knee joints. Immunohistochemistry techniques were conducted to measure the levels of collagen II, MMP13, Nrf2, GPX4, ACSL4, and HO-1 within cartilage tissues. ELISA assays were performed to measure those of TNF-α, IL -6, and PGE2 in serum samples. RESULTS: AVI alleviated chondrocyte apoptosis and extracellular matrix degradation in rat OA induced by IL-1β. It attenuated the levels of TNF-α, IL-6, and PGE2 while reducing those of Fe(2+) and malondialdehyde (MDA). AVI upregulated the expression of Nrf2, HO-1, and GPX4 while downregulating that of ACSL4. Mechanistic studies revealed that ML385-induced inhibition of the Nrf2 signaling pathway reversed the increase in GPX4 and ACSL4 expression and increased Fe(2+) and MDA levels; treatment with erastin, a ferroptosis inducer, produced comparable results. In vivo experiments demonstrated that AVI improved the bone volume/tissue volume and trabecular separation values in OA rats; reversed the Osteoarthritis Research Society International score; upregulated Nrf2, HO-1, and GPX4 expression; downregulated ACSL4 and MMP13 expression, and decreased the serum levels of TNF-α, IL-6, and PGE2. CONCLUSION: Our findings suggest that AVI is a promising therapeutic agent for OA. It exerted its protective effect by regulating the Nrf2/GPX4/HO-1 signaling axis to inhibit cartilage cell ferroptosis and improve osteoarthritis.