Mechanism of miR-21 targeting Smad7 in pulmonary fibrosis of A549 cells induced by beryllium sulfate / 环境与职业医学

ABSTRACT

Background The pathogenesis of beryllium-induced pulmonary fibrosis is unknown and there is no specific treatment for the disease as yet. MicroRNA (miRNA) may play a role in the process of beryllium-induced pulmonary fibrosis. Objective To construct a microRNA-21 (miR-21) interfering cell line, and to investigate the effect of miR-21 on beryllium sulfate (BeSO4)-induced fibrosis in human lung adenocarcinoma alveolar basal epithelial cells (A549 cells) and its potential mechanism. Methods The miR-21 target genes were predicted by the online database miRBase and verified by experiments using dual luciferase reporter gene. After transfecting A549 with miR-21interference lentivirus, puromycin was used to select a stable cell line. An in vitro model of pulmonary fibrosis was established using BeSO4 infecting A549 cells with a concentration of 10 μmol·L−1 and an exposure time of 48 h. Then the treated cells were divided into control group, model group, miR-21 interference group, and miR-21 interference control group. Real-time fluorescent quantitative PCR (RT-qPCR) was used to detect the relative expression level of miR-21 gene. Western blotting was used to detect the relative expression levels of TGF-β1/Smads pathway related proteins [Smad2, Smad3, p-Smad2, p-Smad3, Smad7, and transforming growth factor-β1 (TGF-β1)], myofibrosis cell marker α-smooth muscle actin (α-SMA), andextracellular matrix collagen-I (COL-I) and collagen-Ⅲ (COL-Ⅲ). Results The miRBase predicted that miR-21 had a binding site with Smad7, and the results of the dual luciferase reporter gene experiment showed that the target gene of miR-21 was Smad7. The construction of miR-21 interfered with A549 cell line was successful. Compared with the control group, the relative expression of miR-21 gene in the model group increased by 97.57%; the relative expression of Smad7 protein in the model group decreased by 15.48%; the relative protein expression of Smad2, Smad3, p-Smad2, p-Smad3, TGF-β1, α-SMA, COL-I, and COL-Ⅲ increased by 13.55%, 35.72%, 18.35%, 35.75%, 25.52%, 31.58%, 24.61%, and 11.66% respectively (P<0.05). Compared with the interference control group, the miR-21 gene expression level in the interference group decreased by 28.96%; the relative expression of Smad7 protein increased by 19.07%; the relative protein expression of Smad2, Smad3, p-Smad2, p-Smad3, TGF-β1, α-SMA, COL-I, and COL-Ⅲ decreased by 8.01%, 19.95%, 14.56%, 19.37%, 11.95%, 10.96%, 18.81%, and 31.36% repectively (P<0.05). There was no statistically significant difference in the gene abd protein expression levels of each gene between the model group and the interference control group (P>0.05). Conclusion In an in vitro model of pulmonary fibrosis induced by beryllium compounds, miR-21 may promote fibrosis by targeting Smad7 to regulate the TGF-β1/Smad signaling pathway.