FHL2 deteriorates IL-1β induced inflammation, apoptosis, and extracellular matrix degradation in chondrocyte-like ATDC5 cells by mTOR and NF-ĸB pathways

The role of nuclear translocation in osteoarthritis (OA) pathogenesis has garnered increasing attention in recent years. Extensive research has demonstrated that FHL2 acts as a nuclear transmitter through interactions with other nuclear transcription factors. We aimed to investigate the role of FHL2 in an osteoarthritis cell model. OA cartilage model was established by chondrocyte-like ATDC5 cells induced by 1% insulin-transferrin-selenium and then treated with interleukin-1β (IL-1β, 10 ng/mL). Lentivirus transfection was employed to suppress the expression of FHL2. Immunofluorescence and flow cytometry were used to examine nuclear transcription and apoptosis, respectively. Western blotting was performed to analyze the expression of metabolism-related proteins, autophagy-related proteins, apoptosis-related proteins, as well as proteins associated with the NF-ĸB and mTOR pathways. The elevated expression of FHL2 occurred in both the cytoplasm and the nucleus. Knockdown of FHL2 could inhibit IL-1β-induced phosphorylation of NF-ĸB p65 and stabilize the extracellular matrix (ECM) by decreasing MMP-3 and MMP-13 expression, to suppress COL II degradation in chondrocyte-like ATDC5 cells. Meanwhile, the knockdown of FHL2-activated autophagy in IL-1β-treated chondrocytes through mTOR signaling, characterized by an increased LC3-II/LC3-I ratio and Beclin-1. FHL2 downregulation inhibited IL-1β-induced apoptosis by suppressing BAX and Caspase-3 expression, while enhancing BCL-2 protein levels. This mechanism may involve AKT phosphorylation and decreased expression of p-NF-ĸB p65. FHL2 knockdown activated autophagy while suppressing inflammation, apoptosis, and ECM degradation. The mechanism underlying these processes may involve the inhibition of the mTOR and NF-ĸB signaling pathways.