Long non-coding RNA NEAT1 promotes pulmonary fibrosis by regulating the microRNA-455-3p/SMAD3 axis

Pulmonary fibrosis is an excessive repair response to tissue damage, triggering hyperplasia of fibrotic connective tissues; however, there is no effective treatment in a clinical setting. The purpose of the present study was to investigate the roles of long non-coding RNA nuclear enriched abundant transcript 1 (NEAT1) and microRNA-455-3p (miR-455-3p) were investigated in pulmonary fibrosis. In this study, the mRNA expression levels of NEAT1, miR-455-3p and SMAD3 in the HPAEpiC alveolar and BEAS-2B bronchial epithelial cell lines were determined using reverse transcription-quantitative PCR, while the markers of epithelial-mesenchymal transformation (EMT) and collagen production were determined using western blot analysis. A wound healing assay was performed to evaluate the migratory ability of the HPAEpiC and BEAS-2B cell lines. The interactions between NEAT1 and miR-455-3p or SMAD3 and miR-455-3p were validated using a luciferase reporter gene assay. The results showed that the mRNA expression levels of NEAT1 and SMAD3 were upregulated in the TGF-β1-treated HPAEpiC and BEAS-2B cell lines, while the mRNA expression level of miR-455-3p was significantly decreased. In addition, silencing NEAT1 effectively alleviated the migratory ability, EMT and collagen generation of the epithelial cells. Following these experiments, NEAT1 was identified as a sponge for miR-455-3p, and SMAD3 was a target gene of miR-455-3p. NEAT1 downregulation or miR-455-3p mimic inhibited the migratory ability, EMT and collagen production of the epithelial cells; however, the effects were reversed by the overexpression of SMAD3. Furthermore, NEAT1 knockdown reduced the expression level of SMAD3 by increasing the expression level of miR-455-3p to further inhibit the migratory ability, EMT and collagen production of epithelial cells.