Abstract:

Objective To discuss the effect of inhibiting microRNA（miR）-193a-5p expression on pulmonary fibrosis in the rats with acute respiratory distress syndrome（ARDS）， and to clarify the related mechanism. Methods A total of 60 male SD rats were divided into sham operation group， model group， miR-193a-5p antagonist group（Antagomir group）， and negative control group （Antagomir-NC group）， and there were 15 rats in each group. The ARDS animal model was induced by administering 10 mg·kg^-1 lipopolysaccharide（LPS） via tracheal instillation， while the rats in sham operation group received an equal volume of saline. After successful modeling， the rats in Antagomir group and Antagomir-NC group were treated with miR-193a-5p Antagomir or Antagomir-NC via tail vein injection. The arterial partial pressure of oxygen （PaO₂） and oxygenation index（OI） of the rats in various groups were measured； HE staining and Masson staining were used to observe the pathology and collagen fiber deposition in lung tissue of the rats； kit was used to detect the level of hydroxyproline（Hyp） in lung tissue of the rats in various groups； enzyme-linked immunosorbent assay（ELISA） method was used to detect the levels of inflammatory factors tumor necrosis factor α（TNF-α）， interleukin （IL）-1β， and IL-6 in bronchoalveolar lavage fluid（BALF） of the rats in various groups； real-time fluorescence quantitative PCR（RT-qPCR） method was used to detect the expression levels of miR-193a-5p in lung tissue of the rats in various groups； Western blotting method was used to detect the expression levels of β-catenin， Snail family transcriptional repressor 1（Snail1）， and α-smooth muscle actin（α-SMA） proteins in lung tissue of the rats in various groups. Results Compared with sham operation group， the PaO₂ and OI of the rats in model group were significantly decreased （P<0.05）； compared with model group， the PaO₂ and OI of the rats in Antagomir group were significantly increased（P<0.05）. The HE staining results showed that the lung tissue structure of the rats in sham operation group was normal， and there were no obvious inflammatory changes； compared with sham operation group， mild abnormalities in lung tissue structure， alveolar atrophy， and collapse were observed in the rats in model group and Antagomir-NC group， with a large number of lymphocytes and a small number of neutrophils infiltrating in the alveolar cavities， and widened alveolar spaces； compared with model group， the rats in Antagomir group showed a significant reduction in lymphocytes and neutrophil infiltration in the alveolar cavities and there were no obvious hyperplasia. The Masson staining results showed no obvious blue collagen fiber deposition in lung tissue of the rats in sham operation group； compared with sham operation group， significant blue collagen fiber deposition was observed in lung tissue of the rats in model group and Antagomir-NC group， with severe damage of the alveolar structure， indicating obvious pulmonary fibrosis； compared with model group， the deposition of blue-stained collagen fibers in lung tissue of the rats in Antagomir group was significantly reduced. Compared with sham operation group， the level of Hyp in lung tissue of the rats in model group was significantly increased（P<0.05）； compared with model group， the level of Hyp of the rats in Antagomir group was significantly decreased（P<0.05）. The ELISA results showed that compared with sham operation group， the levels of TNF-α， IL-1β， and IL-6 in BALF of the rats in model group were significantly increased（P<0.05）； compared with model group， the levels of TNF-α， IL-1β， and IL-6 of the rats in Antagomir group were significantly decreased（P<0.05）. The RT-qPCR results showed that compared with sham operation group， the expression level of miR-193a-5p in lung tissue of the rats in model group was significantly increased（P<0.05）； compared with model group， the expression level of miR-193a-5p of the rats in Antagomir group was significantly decreased（P<0.05）. The Western blotting results showed that compared with sham operation group， the expression levels of β-catenin， Snail1， and α-SMA proteins in lung tissue of the rats in model group were significantly increased（P<0.05）； compared with model group， the expression levels of β-catenin， Snail1， and α-SMA proteins in lung tissue of the rats in Antagomir group were significantly decreased（P<0.05）. Conclusion Inhibition of miR-193a-5p expression can improve the lung function and alleviate the pulmonary fibrosis in the ARDS rats by reducing the inflammatory responses and downregulating the expressions of β-catenin， Snail1， and α-SMA proteins.

Key words: Micro RNA-193a-5p, Acute respiratory distress syndrome, Pulmonary fibrosis, Wnt/β-catenin signaling pathway