VHL/CDO1 axis regulates chondrocyte ferroptosis and knee osteoarthritis progression

Ferroptosis is closely associated with the pathogenesis of osteoarthritis (OA), though the underlying molecular mechanisms remain unclear. This study aims at exploring the role of CDO1 in chondrocyte ferroptosis. In this study, cell viability was assessed using the CCK8 assay. ROS levels were measured via flow cytometry. Lipid peroxidation was evaluated using the C11 BODIPY 581/591 fluorescent probe, and mitochondrial morphology was examined by transmission electron microscopy. Our results demonstrated that CDO1 was upregulated in cartilage tissues from patients with severe knee OA. IL-1β stimulation elevated ferroptosis levels in SW1353 cells, as indicated by reduced cell viability, extracellular matrix (ECM) accumulation and GSH levels, increased oxidative stress, lipid peroxidation and MDA content, and impaired mitochondrial morphology. These effects were reversed by the ferroptosis inhibitor Fer-1. Overexpression of CDO1 reduced intracellular cysteine levels and enhanced ferroptosis, whereas CDO1 knockdown produced the opposite effects. We further identified VHL as a binding partner of CDO1 and showed that VHL promoted CDO1 protein degradation. The ferroptosis and ECM degradation induced by CDO1 overexpression were rescued by VHL co-overexpression. Importantly, cysteine deficiency enhanced VHL activity, promoted CDO1-VHL interaction, and accelerated CDO1 degradation, thereby may form a VHL/CDO1/cysteine negative feedback loop. The function of CDO1/VHL axis was further validated in a rat OA model, where CDO1 exacerbated OA progression and VHL alleviated it. In summary, our findings reveal that the VHL/CDO1 axis regulates intracellular cysteine levels, mediates chondrocyte ferroptosis and OA progression.