Circular RNA circ-CARD8 regulates alveolar macrophage pyroptosis through the miR-580-3p/CARD8 pathway in acute lung injury

by Sida Chen, Ling Wen, Yumei Wu, Shan Xiao, Yuting Lai, Jintao Ou, Yan Shen

Pyroptosis is linked to the development of acute lung injury (ALI), and circular RNAs (circRNAs) play a role in ALI-related inflammation. However, the mechanisms by which circRNAs contribute to macrophage pyroptosis in ALI remain unclear. This study constructed an in vitro ALI model by inducing THP-1 cells with phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS). The expression and potential mechanism of circ-CARD8 in macrophage pyroptosis were then investigated. The interaction between circ-CARD8, hsa-miR-580-3p, and caspase recruitment domain family member 8 (CARD8) was confirmed through luciferase reporter assays and RNA-binding protein immunoprecipitation. Our data showed that circ-CARD8 was expressed at low levels. Meanwhile, the pyroptotic proteins caspase-1 and GSDMD, along with the secretion of chemokine (C-C motif) ligand 18 and interleukin 1 beta, were upregulated in the ALI cell model. Overexpression of circ-CARD8 reversed macrophage pyroptosis, whereas inhibition of circ-CARD8 promoted it. Furthermore, the expression of miR-580-3p, a downstream microRNA that binds to circ-CARD8, was reduced upon circ-CARD8 overexpression and increased following its inhibition. Additionally, overexpression of miR-580-3p suppressed the expression of CARD8, a downstream target of miR-580-3p, thereby promoting macrophage pyroptosis. The inhibition of miR-580-3p reversed the effect of circ-CARD8 silencing on macrophage pyroptosis and CARD8 expression. Therefore, our study confirms that the low expression of circ-CARD8 reduces the sponge adsorption of miR-580-3p, increasing its expression, which in turn targets and inhibits CARD8, ultimately promoting macrophage pyroptosis induced by LPS in THP-1 cells.