Objective: To explore the regulatory effects of microRNA-218 on lung tissue of rats with acute lung injury (ALI) and its underlying mechanism.
Materials and methods: A total of 32 Sprague Dawley (SD) rats were randomly divided into control group, lung injury group and microRNA-218 treatment group. The in vitro lung injury model was established by injections of lipopolysaccharide (LPS), PGN (peptidoglycan) and IgG IC (immune complex). Polymerase Chain Reaction (PCR) was performed to detect the expression of microRNA-218 in lung tissues of ALI rats. Enzyme-Linked Immunosorbent Assay (ELISA) was used to measure the level of cytokine secretion in ALI rats. The activity and expression level of nuclear factor-kappa B (NF-κB) in MH-S and RA264.7 cells were determined by Luciferase activity assay and Western blot, respectively.
Results: MicroRNA-218 was significantly down-regulated in bleomycin and IgG IC-induced lung injury rat model, as well as in cells treated with LPS, PGN and IgG IC. Inflammatory factors, including TNF-α, IL-1b, and IL-6, also showed increased in vivo and in vitro expressions. Besides, the overexpression of microRNA-218 inhibited the secretion of inflammatory factors. PCR analysis and Luciferase activity assay indicated that the expressions of RUNX2 and BIRC3 were down-regulated by microRNA-218 in MH-S and RA264.7 cells. Subsequent studies on mechanisms demonstrated that microRNA-218 inhibited the activity of the NF-κB pathway.
Conclusions: The expression of microRNA-218 markedly decreased in lung tissue of ALI rats, while the expression of inflammatory cytokines showed a remarkable increase, which might be related to the activation of RUNX2 and NF-κB.