The role and mechanism of transcription factor KLF4 in regulating mitochondrial damage and apoptosis by activating chondrocyte autophagy in osteoarthritis

Objective To explore the role and mechanism of transcription factor KLF4 in regulating mitochondrial damage and apoptosis by activating chondrocyte autophagy. Methods Human primary chondrocytes were treated with IL-1β to establish an in vitro osteoarthritis model. KLF4 was overexpressed using lentivirus to intervene in chondrocytes. Cell apoptosis and mitochondrial membrane potential were detected by flow cytometry. Mitochondrial morphology was observed under transmission electron microscopy. Cell ATP level was detected by ELISA. Ca2 + homeostasis was detected by flow cytometry with Fluo-3/AM fluorescence labeling. The expression of autophagy-related proteins Beclin1, P62, and LC3 was detected by WB. The interaction between transcription factor KLF4 and gene p62 promoter was verified by dual luciferase assay. The interaction between p62, Beclin1 and KLF4 was verified by Chip assay. To further explore the relationship between KLF4 and autophagy, KLF4 was overexpressed and treated with autophagy inhibitor 3-MA (5mmol/L). The expression of autophagy-related proteins Beclin1, P62, and LC3 was detected by WB. Cell apoptosis level was detected by flow cytometry. The mitochondrial membrane potential level was detected by flow cytometry. Ca2 + homeostasis was detected by flow cytometry with Fluo-3/AM fluorescence labeling. Results In chondrocytes treated with IL-1β, TNF-α levels increased significantly, apoptosis rate rose, and ATP generation declined. However, after overexpression of KLF4, apoptosis level decreased significantly; ATP level increased significantly, and mitochondrial structure and function gradually recovered. Flow cytometry detection of mitochondrial membrane potential showed a significant decrease after KLF4 overexpression, and Ca2 + homeostasis was partially restored. WB detection of autophagy-related proteins showed a significant increase in p62 and cellular autophagy levels. Dual luciferase results indicated that transcription factor KLF4 interacted with the promoter of gene p62; Chip experiment results suggested that KLF4 may interact with the promoter regions of P62 and Beclin1. After KLF4 overexpression combined with 3-MA treatment, compared with empty load combined with 3-MA, p62 and LC3 protein expression increased significantly, apoptosis level decreased significantly, and membrane potential level decreased. Conclusion Transcription factor KLF4 can regulate mitochondrial damage and apoptosis by activating chondrocyte autophagy.