Ozone induces autophagy in rat chondrocytes stimulated with IL- Iβ through the AMPK/mTOR signaling pathway

Background: Ozone injection is generally used for the management of pain in diseases such as osteoarthritis (OA). Recent studies have shown that reduced autophagy in chondrocytes plays an important role in the development of OA. The purpose of this study was to determine whether ozone treats OA by inducing autophagy in OA chondrocytes. Materials and methods: In this study, primary chondrocytes were stimulated with IL-113 for 24 hours to simulate an OA chondrocyte model, followed by treatment with ozone (30 mu g/ mL) or pretreatment with 3-methyladenine or compound C before ozone treatment. Then, cell viability was detected by a CCK-8 kit, and the AMPK/mTOR signaling pathway and autophagy were detected by Western blotting and immunofluorescence. The mRNA expression levels of IL-6, TNF-alpha, MMP-13 and TIMP- 1 were measured by quantitative real-time PCR. Finally, autophagosomes in chondrocytes were observed by transmission electron microscopy. Results: Ozone improved cell viability in chondrocytes stimulated by IL-1 beta. The decreased level of autophagy in IL-1 beta-stimulated chondrocytes improved with ozone treatment through activation of the AMPK/mTOR signaling pathway. In addition, the mRNA expression levels of IL-6 and TNF-alpha were suppressed by ozone treatment in chondrocytes stimulated with IL-1 beta. Ozone increased the mRNA level of TIMP-1 and decreased the mRNA level of MMP- 13 in chondrocytes stimulated with IL-1 beta. Conclusion: These results suggested that ozone improved the decreased level of autophagy in chondrocytes stimulated with IL-1 beta through activation of the AMPK/mTOR signaling pathway. Moreover, ozone treatment suppressed inflammation and helped maintain metabolic balance in chondrocytes stimulated with IL- 1 beta.