MicroRNA-7-5p regulates human alveolar epithelial sodium channels by targeting the mTORC2/SGK-1 signaling pathway

Purpose: The aim of this study was to investigate the effect of miRNA-7-5p on human alveolar epithelial sodium channels and clarify the pathway in which miRNA-7-5p regulates the expression of ENaC in ARDS. Materials and Methods: Dual luciferase target gene validation experiments were used to confirm whether mTOR and SGK-1 are the target genes of miRNA-7-5p. Then, we overexpressed and inhibited miRNA-7-5p in the human alveolar epithelial cell line A549, respectively. LPS at a concentration of 100 ng/mL was used to stimulate the cells. The expressions of miRNA-7-5p, mTOR, SGK-1, p-Akt-Ser473, alpha-, beta-, and gamma-ENaC were detected by quantitative RT polymerase chain reaction (qRT-PCR) and western blotting. Results: In this study, we first confirmed that mTOR and SGK-1 are the target genes of miRNA-7-5p. Then, we found that mRNA expression levels of both mTOR and SGK-1 were downregulated to 0.54- and 0.3-fold, respectively, in the miRNA-7-5p mimic groups than the blank controls (P < 0.01). MiRNA-7-5p overexpression inhibited mTORC2/SGK-1 signaling pathway activity and reduced ENaC expression. The expression of miRNA-7-5p was significantly upregulated in A549 cells stimulated with lipopolysaccharide (LPS) and downregulated mRNA expression levels of both mTOR and SGK-1. After transfection with miRNA-7-5p inhibitors, we found that the mTORC2/SGK-1 pathway activity was restored compared to the group with LPS stimulation only, and the ENaC expression was also obviously increased. Conclusion: Our results demonstrate that miRNA-7-5p can regulate the expression of human alveolar ENaC by targeting the mTORC2/SGK-1 signaling pathway. The inhibition of miRNA-7-5p can enhance the expression of ENaC, which may provide a new target for the treatment of ARDS.