Ozone induces autophagy by activating PPARγ/mTOR in rat chondrocytes treated with IL-1β

BACKGROUND: Osteoarthritis (OA) is the main cause of older pain and disability. Intra-articular injections of ozone (O(3)) commonly have been found to have antioxidative and anti-inflammatory effects to reduce pain and improve function in knee osteoarthritis. It has been reported that reduced autophagy in chondrocytes plays an important role in the development of OA. This study aimed to probe the role of O(3) on the autophagy in chondrocytes treated with IL-1β. METHODS: Primary chondrocytes were isolated from Wistar rats cartilage within 3 days. The OA chondrocytes model was induced via treatment with IL-1β for 24 h. Then the cells were treated with O(3) and GW9662, the inhibitor of PPARγ. Cell viability was assessed by CCK-8. Further, the cells subjected to Western blot analysis, qRT-PCR and immunofluorescence assay. The numbers of autophagosomes were observed via transmission electron microscopy. RESULTS: 30 μg/ml O(3) improved the viability of chondrocytes treated with IL-1β. The decreased level of autophagy proteins and the numbers of autophagosomes improved in IL-1β-treated chondrocytes with O(3) via activating PPARγ/mTOR. In addition, the qRT-PCR results showed that O(3) decreased the levels of IL-6, TNF-α and MMP-3, MMP-13 in chondrocytes treated with IL-1β. CONCLUSIONS: 30 μg/ml O(3) improved autophagy via activating PPARγ/mTOR signaling and suppressing inflammation in chondrocytes treated with IL-1β.