Circ_0033530 knockdown alleviates lipopolysaccharide-induced acute lung injury model of human lung fibroblasts by miR-1184/TLR4 axis

Abstract

Abstract Background Circular RNAs (circRNAs) have been reported to be involved in regulating the progression of sepsis and sepsis-associated damage. Herein, this work investigated whether circ_0033530 had roles in the process of septic acute lung injury (sepsis-ALI) and its associated mechanism. Methods Lipopolysaccharide (LPS)-stimulated human lung fibroblasts MRC-5 were used to mimic the cell model of sepsis-ALI in vitro. Levels of genes and proteins were detected by qRT-PCR and western blotting. Functional experiments were conducted using 5-ethynyl-2’-deoxyuridine (EdU) assay, Cell counting Kit-8 (CCK-8) assay, flow cytometry, and Enzyme-Linked Immunosorbent Assay (ELISA), respectively. The interaction between miR-1184 and circ_0033530 or Toll-like receptor 4 (TLR4) was confirmed by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Results Circ_0033530 expression was lower in sepsis patients and LSP-induced fibroblasts than those in healthy control and untreated cells. Functionally, knockdown of circ_0033530 protected fibroblasts against LPS-induced proliferation arrest, apoptosis and inflammatory response. Mechanistically, circ_0033530 acted as a sponge for miR-1184, and TLR4 RNA was targeted by miR-1184, indicating the circ_0033530/miR-1184/TLR4 axis. Further rescue experiments showed that circ_0033530 silencing-mediated growth inhibition and inflammation on fibroblasts were attenuated by miR-1184 down-regulation or TLR4 up-regulation. Conclusion Circ_0033530 knockdown alleviated LPS-induced proliferation arrest, apoptosis and inflammation in lung fibroblasts by miR-1184/TLR4 axis, provide molecular theoretical basis for circ_0033530 on the pathogenesis of sepsis-ALI.