Blocking Runx2 Inhibits the Caspase-1 Dependent Pyroptosis in Lipopolysaccharide-Treated Chondrocyte

Abstract

Pyroptosis is a new type of cell death in the development of osteoarthritis (OA), but the underlying mechanism is not fully understood. This study aimed to investigate the role of Runx2 in the pyroptosis of chondrocyte (CH) and explore its effect on Caspase-1 expression. Human knee tissues from the fracture patients without OA history were collected. Human CHs isolated from the tissue were treated by lipopolysaccharide (LPS) to establish the model of OA. siRNA and CADD522 were used to block the function of Runx2. The cell viability was tested by MTT. The expression levels of Runx2, Caspase1/4/5/11, GSDMD, collagen-II, aggrecan, IL-1β, IL-8, and MMP3/9 were detected by RT-PCR, immunofluorescence, or western blot. Besides, the transcriptional association between Runx2 and Caspase-1 was confirmed by DNA immunoprecipitation and luciferase reporter assay. Runx2 and Caspase-1 expression were increased in LPS-treated CHs. Runx2 bound to the promoter of Caspase-1 and activated its expression. Moreover, silencing Runx2 or disrupting the DNA-binding ability of Runx2 attenuated the LPS-induced pyroptotic phenotype, containing Caspase-1 activation, collagen-II and aggrecan degradation, viability suppression, IL-1β and IL-8 upregulation. Blocking the expression or function of Runx2 alleviated the LPS-caused pyroptosis in CHs in the Caspase-1 manner, indicating a novel understanding of the pathology of OA.