LncRNA OIP5-AS1 promotes mitophagy to alleviate osteoarthritis by up-regulating PPAR-γ to activate AMPK/Akt/mTOR pathway.

BACKGROUND: Osteoarthritis (OA) is the most common chronic joint degenerative disease. Mitophagy is closely related to OA pathogenesis. Herein, we investigated the role of lncRNA OIP5-AS1 in regulating mitophagy during OA.

METHODS: RT-qPCR and Western blotting were utilized to analyze gene and protein levels. RIP and RNA pull down verified the relationship between OIP5-AS1, FUS and PPAR-γ. CCK-8 assay detected cells viability. ELISA evaluated the secretion of inflammatory cytokines. Flow cytometry measured the contents of ROS and Ca2+. Immunofluorescence staining analyzed TOMM20 and LC3B levels. JC-1 staining was adopted to measure mitochondrial membrane potential. The changes of mitophagy were analyzed by TEM.

RESULTS: LPS treatment contributed to the decrease of chondrocytes viability, calcium level and inhibited mitochondrial membrane potential, while elevated the secretion of inflammatory factors, ROS accumulation and TOMM20 expression. Additionally, LPS decreased the ratio of LC3II/I, Parkin and PINK1 protein levels, and increased p62 and TOMM20 protein levels. Furthermore, overexpression of OIP5-AS1 inhibited LPS-induced chondrocytes injury and activated mitophagy. OIP5-AS1 upregulated PPAR-γ mRNA level to regulate AMPK/Akt/mTOR signaling by interacting with FUS. In addition, PPAR-γ overexpression alleviated LPS induced chondrocytes injury by activating AMPK/Akt/mTOR signaling. Knockdown of PPAR-γ reversed the promotion of OIP5-AS1 upregulation on mitophagy.

CONCLUSION: OIP5-AS1 promotes PPAR-γ expression to activate the AMPK/Akt/mTOR signaling, thereby enhancing mitophagy and alleviating OA progression. It is suggested that OIP5-AS1 may function as a protector in OA development.