Molecular Mechanism of Hydroxyl Safflower Yellow A in Knee Osteoarthritis through Modulation of Autophagy <em>via</em> Inhibition of the HIF-1α/BNIP3 Pathway

The reduction of autophagy in cartilage tissue is closely linked to the development of knee osteoarthritis (KOA), yet the mechanisms by which Hydroxyl safflower yellow A (HSYA) exerts protective effects remain incompletely understood. In this study, human KOA chondrocytes were isolated and assigned to different treatment groups, including normal control, blank model, HSYA, hypoxia-inducible factor-1α (HIF-1α) inhibitor, autophagy inducer, HSYA combined with HIF-1α inhibitor, and HSYA combined with autophagy inducer. Proinflammatory cytokines (IL-1β, TNF-α, IL-6) were quantified by ELISA, protein expression of HIF-1α, BNIP3, and autophagy-related markers was examined by Western blotting, and autophagic vesicles in mitochondria were evaluated using monodansylcadaverine staining and transmission electron microscopy. Compared with the normal control, the blank model group showed significantly increased levels of IL-1β, TNF-α, IL-6, and HIF-1α, accompanied by higher apoptosis rates, reduced proliferation, and downregulation of autophagy-related proteins (P < 0.05). Treatment with HSYA, HIF-1α inhibitor, or autophagy inducer significantly upregulated autophagy-related protein expression and reduced inflammatory cytokine levels. Moreover, HSYA combined with HIF-1α inhibitor or autophagy inducer produced the most pronounced effects, with marked reductions in cytokine release and apoptosis, along with enhanced chondrocyte proliferation and mitochondrial autophagic vesicle formation (P < 0.05). These findings demonstrate that HSYA exerts chondroprotective effects in KOA, at least in part, through inhibition of the HIF-1α/BNIP3 pathway, thereby promoting autophagy and attenuating inflammatory injury in chondrocytes.