Baicalin mitigated IL-1β-Induced osteoarthritis chondrocytes damage through activating mitophagy

Mitophagy is related to chondrocyte homeostasis and plays a key role in the progress of osteoarthritis (OA). Baicalin has a protective effect on OA chondrocytes, the aim of this study was to explore whether the effect of Baicalin on IL-1β-induced chondrocyte injury is related to the regulation of mitophagy. The expression of collagen II in chondrocytes was detected to identify chondrocytes. The effects of different concentrations of Baicalin (10, 20 and 40 μM), autophagy inhibitor (3-Methyladenine), autophagy activator (rapamycin) and Baicalin combined with PI3K agonist (740Y-P) on the viability (cell counting kit 8), apoptosis (flow cytometry), autophagy activation (Monodansylcadaverine staining) and mitochondrial membrane potential (JC-1 kit) of IL-1β-induced chondrocytes were evaluated. The co-localization of autophagosome and mitochondria was determined by immunofluorescence. Apoptosis-, autophagy-, PI3K/AKT/mTOR pathway- and mitophagy-related proteins were detected by western blot. Our result revealed that Baicalin and rapamycin facilitated cell viability, autophagy and mitophagy, elevated mitochondrial membrane potential and suppressed apoptosis of IL-1β-induced rat chondrocytes. In addition, Baicalin and rapamycin upregulated the levels of Bcl-2, Beclin 1, LC3-II/LC3-I, p-Drp1, PINK1 and Parkin as well as downregulated the levels of Bax, cleaved caspase-3, P62, p-PI3K/PI3K, p-mTOR/mTOR and Drp1 in IL-1β-induced rat chondrocytes. However, 3-Methyladenine did the opposite effects of Baicalin and 740Y-P reversed the effects of Baicalin on IL-1β-induced rat chondrocytes. In conclusion, Baicalin activated mitophagy in IL-1β-induced chondrocytes by inhibiting PI3K/AKT/mTOR pathway and activating PINK1/Parkin and PINK1/Drp-1 pathway, thereby reducing the chondrocyte injury.