Circular RNA circESPL1 knockdown alleviates lipopolysaccharide (LPS)-induced lung cell injury via sponging miR-326 to regulate MAPK14

Background: Infantile pneumonia (IP) is a common inflammatory disease, which brings a heavy burden to young children's health. Previous studies suggested that circular RNA (circRNA) hsa_circ_0026579 (also called cir-cESPL1) was significantly upregulated in pneumonia patients, which was associated with the disease severity. This subject aimed to explore the functional effects and potential regulatory mechanism of circESPL1 on lipo-polysaccharide (LPS)-induced lung cell injury. Methods: WI-38 and MRC-5 cells were stimulated by LPS to mimic the inflammatory injury model. CircESPL1, microRNA-326 (miR-326), and Mitogen-Activated Protein Kinase 14 (MAPK14) levels were measured using real -time quantitative polymerase chain reaction (RT-qPCR). Cell Counting Kit-8 (CCK-8), 5-ethynyl-2 & PRIME;-deoxyuridine (EdU), and flow cytometry assays were performed to assess cell proliferation and apoptosis. Western blot analysis of B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), C-caspase 3, and MAPK14 protein levels. Tumor necrosis factor-alpha (TNF-alpha), Interleukin-6 (IL-6), and IL-1 beta levels were examined using an Enzyme-linked immu-nosorbent assay (ELISA). Using Starbase analysis, the binding between miR-326 and circESPL1 or MAPK14 was predicted, followed by confirmation using a dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays. Results: Increased circESPL1 and MAPK14, and reduced miR-326 were observed in serum samples from pre-eclampsia sufferers and LPS-treated lung cells (P < 0.05). Furthermore, circESPL1 deficiency overturned LPS-mediated cell proliferation, apoptosis, and inflammatory response in vitro (P < 0.05). In terms of molecular mechanisms, circESPL1 worked as a sponge of miR-326, and miR-326 absence reversed the protective role of circESPL1 silencing on LPS-triggered lung cell injury (P < 0.05). Also, miR-326 directly targeted MAPK14, and MAPK14 overexpression abolished miR-326-mediated impacts under LPS treatment (P < 0.05). Conclusion: CircESPL1 knockdown might attenuate LPS-caused lung cell injury by regulating the miR-326/ MAPK14 axis, providing useful insight for exploring a novel therapeutic approach for IP.

Automated summary

This study found that circESPL1 deficiency can attenuate LPS-induced lung cell injury by regulating the miR-326/MAPK14 axis, providing a new insight for the treatment of infantile pneumonia.