Circ_0026579 knockdown ameliorates lipopolysaccharide‐induced human lung fibroblast cell injury by regulating CXCR1 via miR‐370‐3p

Abstract Pneumonia is an inflammatory disease in lower respiratory tracts and its development involves the regulation of RNAs. Circular RNAs are a class of RNA subgroups that can mediate the progression of pneumonia. However, the molecular mechanism of circ_0026579 in regulating pneumonia occurrence remains unclear. The study is designed to reveal the role of circ_0026579 in lipopolysaccharide (LPS)‐induced human lung fibroblast cell injury and the underlying mechanism. The expression levels of circ_0026579, miR‐370‐3p and C‐X‐C motif chemokine receptor 1 (CXCR1) were detected by quantitative real‐time polymerase chain reaction or by western blotting. The production of tumour necrosis factor‐α, interleukin (IL)‐1β and IL‐6 was assessed by enzyme‐linked immunosorbent assays. Malondialdehyde and superoxide dismutase levels were analysed using commercial kits. Cell viability, proliferation and apoptosis were analysed by cell counting kit‐8 assay, 5‐Ethynyl‐2′‐deoxyuridine assay and flow cytometry analysis, respectively. The binding relationship between miR‐370‐3p and circ_0026579 or CXCR1 was identified by dual‐luciferase reporter assay, RNA immunoprecipitation assay and RNA pull‐down assay. Circ_0026579 and CXCR1 expression were significantly upregulated, whereas miR‐370‐3p was downregulated in the serum of pneumonia patients. LPS treatment induced inflammatory response, oxidative stress and cell apoptosis and inhibited cell proliferation in MRC‐5 cells; however, these effects were reversed after circ_0026579 depletion. In terms of the mechanism, circ_0026579 acted as a miR‐370‐3p sponge, and miR‐370‐3p combined with CXCR1. Additionally, circ_0026579 depletion ameliorated LPS‐induced MRC‐5 cell disorder by increasing miR‐370‐3p expression. CXCR1 overexpression also relieved the miR‐370‐3p‐mediated effects in LPS‐treated MRC‐5 cells. Further, circ_0026579 induced CXCR1 expression by interacting with miR‐370‐3p. Circ_0026579 absence ameliorated MRC‐5 cell dysfunction induced by LPS through the regulation of the miR‐370‐3p/CXCR1 axis.