Circ_ZNF652 regulates the proliferation and apoptosis of LPS-induced WI-38 cells via miR-302e/TLR4 axis

Background: Circular RNAs (circRNAs) play an important regulatory role in multiple human diseases, including organ allograft rejection. Infantile pneumonia (IP) is a common disease that seriously threatens the health of infants and young children. CircRNAs have been shown to be involved in the advance of IP. However, the function of circ_ZNF652 in IP has not been fully studied. Methods: Lipopolysaccharide (LPS)-treated WI-38 cells were used as cell injury models of IP. Quantitative realtime polymerase chain reaction (qRT-PCR) was used to detect the expression of circ_ZNF652, miR-302e and Toll-like receptor 4 (TLR4). 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium Bromide (MTT) assay, thymidine analog 5-ethynyl-2 & PRIME;-deoxyuridine (EdU) assay, and flow cytometry assay were utilized to explore cell functions. Western blot was employed to examine the protein levels of PCNA, Bcl-2, Bax, and TLR4. ELISA was used to detect the release of inflammatory cytokines. The relationship between miR-302e and circ_ZNF652 or TLR4 was verified by dual-luciferase reporter assay and RNA pull down assay. Results: Circ_ZNF652 was significantly up-regulated in serum of IP patients and LPS-induced WI-38 cells. Silencing circ_ZNF652 enhanced cell proliferation and inhibited cell apoptosis in LPS-induced WI-38 cells. MiR302e was identified as a target of circ_ZNF652, and knockdown of circ_ZNF652 alleviated LPS-induced WI-38 cell injuries by up-regulating miR-302e. In addition, TLR4 was a downstream target of miR-302e. Overexpression of TLR4 recovered cell apoptosis and inflammation that were repressed by miR-302e enrichment in LPS-induced WI-38 cells. Conclusion: Circ_ZNF652 regulates the expression of TLR4 by regulating miR-302e, thereby mediating cell proliferation, apoptosis and inflammation. The results provide a novel targeted therapy for IP.