miR-200b/c attenuates lipopolysaccharide-induced early pulmonary fibrosis by targeting ZEB1/2 via p38 MAPK and TGF-β/smad3 signaling pathways.

Pulmonary fibrosis triggered during the early stage of acute respiratory distress syndrome (ARDS) contributes to poor prognosis in patients. However, whether microRNAs (miRNAs) can serve as therapeutic targets for early pulmonary fibrosis during ARDS is still largely unknown. In this study, we evaluated the effects and mechanisms of miR-200s and its targets ZEB1/2 in lung tissue. An early pulmonary fibrosis mouse model caused by ARDS was established via a lipopolysaccharide (LPS) three-hit regimen. Lentiviral packaged miR-200b/c cDNA or ZEB1/2 shRNA was intratracheally administered into the lungs of C57BL/6 mice 1 day before an LPS injection was administered. In vitro, following a 30-min pretreatment with miR-200b/c or SB203580/SIS3, RLE-6TN cells were stimulated by LPS or LPS + transforming growth factor-β (TGF-β) for 24 h. miR-200b/c and E-cadherin protein expression declined, whereas ZEB1/2 mRNA and protein and vimentin and α-smooth muscle actin (α-SMA) protein levels gradually increased during the development of pulmonary fibrosis. Furthermore, both the overexpression of miR-200b/c and the silencing of ZEB1/2 significantly alleviated pulmonary inflammation and fibrosis, reduced vimentin and α-SMA expression, and increased E-cadherin protein levels. In RLE-6TN cells, LPS combined with TGF-β exerts synergistic effects of increasing vimentin and α-SMA protein levels, increasing p38 and smad3 phosphorylation and reducing E-cadherin protein levels, which were reversed by pretreatment with miR-200b/c or SB203580/SIS3. Our findings demonstrate that miR-200b/c was downregulated, whereas ZEB1/2 was upregulated in the development of LPS-induced early pulmonary fibrosis. miR-200b/c exerts a protective effect by targeting ZEB1/2, which may be associated with the inhibition of p38 MAPK and TGF-β /smad3 signaling pathways.