Effects of miR-204-3p inhibitor on epithelial-mesenchymal transition and silicosis fibrosis in silicon dioxide-induced alveolar epithelial cells

BackgroundThe pathogenesis of silicosis has not been fully elucidated, and microRNAs (miRNA) may be involved in the occurrence and development of silicosis. ObjectiveTo investigate the effect of miR-204-3p inhibitor on the epithelial-mesenchymal transition (EMT) process and silicosis fibrosis in silicon dioxide dust-induced alveolar epithelial cells. MethodsA co-culture model of macrophages and epithelial cells was established using a Transwell chamber. NR8383 macrophages were seeded into the upper chamber of the Transwell, and RLE-6TN cells were seeded into the lower chamber. After 24 h of culture, the medium in the lower chamber was discarded, washed three times with phosphate-buffered saline (PBS), and replaced with serum-free medium. The cells were divided into four groups: control group, silicosis group, miRNA NC group, and miR-204-3p inhibitor group. The lower chamber was transfected with miRNA NC for the miRNA NC group or the miR-204-3p inhibitor for the miR-204-3p inhibitor group. The lower chambers of the remaining two groups were added by equal amounts of serum-free medium. After 24 h, except for the control group that received an equal volume of serum-free medium, the upper chambers of the remaining three groups were treated with 800 μg·mL−1 silicon dioxide dust. Morphological changes in each group were observed under a microscope. The mRNA and protein expression levels of EMT-related factors, including α-smooth muscle actin (α-SMA), Vimentin, N-Cadherin, and E-Cadherin, were detected by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and Western blot. The mRNA and protein expression levels of fibrosis-related factors, including Collagen I, Collagen III, and Fibronectin, were also assessed by RT-qPCR and Western blot. The fluorescence expression intensities of α-SMA, N-Cadherin, and E-Cadherin were evaluated by immunofluorescence. ResultsThe morphological observation revealed that RLE-6TN cells in the control group exhibited a regular oval shape. After treatment with silicon dioxide, the cells predominantly displayed a long spindle shape. Following the intervention with the miR-204-3p inhibitor, the number of long spindle-shaped cells increased, and the intercellular gaps widened. The RT-qPCR results showed that, compared with the control group, the silicosis group exhibited significantly higher relative mRNA expression levels of EMT-related markers (α-SMA, Vimentin, and N-Cadherin) (P<0.05), while the relative mRNA expression level of E-Cadherin was significantly reduced (P<0.05); the relative mRNA expression levels of fibrosis-related markers (Collagen I, Collagen III, and Fibronectin) were also significantly elevated (P<0.05). Compared with the miRNA NC group, the miR-204-3p inhibitor group showed significantly increased relative mRNA expression levels of α-SMA, Vimentin, and N-Cadherin (P<0.05), decreased E-Cadherin mPNA expression (P<0.05), and elevated mPNA expression of Collagen I, Collagen III, and Fibronectin (P<0.05). The Western blot analysis indicated that, compared with the control group, the silicosis group had significantly higher protein expression levels of α-SMA, Vimentin, and N-Cadherin (P<0.05), lower E-Cadherin protein expression (P<0.05), and increased protein expression of Collagen I, Collagen III, and Fibronectin (P<0.05). Compared with the miRNA NC group, the miR-204-3p inhibitor group exhibited significantly elevated protein expression levels of α-SMA, Vimentin, and N-Cadherin (P<0.05), reduced E-Cadherin expression (P<0.05), and increased protein expression of Collagen I, Collagen III, and Fibronectin (P<0.05). The immunofluorescence analysis demonstrated that, compared with the control group, the silicosis group showed enhanced fluorescence intensities of α-SMA and N-Cadherin and reduced fluorescence intensity of E-Cadherin. Compared with the miRNA NC group, the miR-204-3p inhibitor group exhibited increased fluorescence intensities of α-SMA and N-Cadherin and decreased fluorescence intensity of E-Cadherin. ConclusionThe miR-204-3p inhibitor may exacerbate the EMT process and silicosis fibrosis in silicon dioxide-induced RLE-6TN cells. miR-204-3p plays a negative regulatory role in silicosis fibrosis.