Role of miR-433 in fibrosis of NIH-3T3 cells and silica-induced pulmonary fibrosis in mice

AIM To study the role and regulatory mechanism of microRNA-433 (miR-433) in fibrosis. METHODS TargetScan was used to predict the potential target genes of miR-433. The changes of miR-433 expression were detected after transforming growth factor β1 (TGF-β1) treatment of mouse embryonic fibroblasts (NIH-3T3 cells) for 24 h. The effects of miR-433 mimic on the expression of p-SMAD2, fibronectin (FN), α-smooth muscle actin (α-SMA) and connective tissue growth factor (CTGF) in TGF-β1 treated cells were examined. The effects of miR-433 mimic transfection on the viability and S-phase fraction of NIH-3T3 cells induced by TGF-β1 were detected by CCK-8 assay and flow cytometry. A model of silica-induced pulmonary fibrosis in mice was established, and agomiR-433 was used for intervention. HE staining and Masson staining were used to observe the effect of miR-433 on pulmonary fibrosis in the mice. The expression of α-SMA in lung tissues was detected by immunohistochemistry. RESULTS miR-433 specifically bound to the 3'-UTR of SMAD2 and inhibited its expression at protein and mRNA levels. TGF-β1 down-regulated the expression of miR-433 in NIH-3T3 cells, up-regulated the protein level of p-SMAD2 and the expression of FN, α-SMA and CTGF at protein and mRNA levels, and increased the viability and the number of S-phase cells. miR-433 mimic reversed the effects of TGF-β1 on NIH-3T3 cell viability and S-phase arrest. In a model of silica-induced pulmonary fibrosis in mice, agomiR-433 inhibited the progress of pulmonary fibrosis and reduced the expression of α-SMA in mouse lung tissues. CONCLUSION miR-433 may interfere with TGF-β1/SMAD2 signaling pathway through targeting SMAD2, thus participating in the regulation of fibrosis process.