Expression of microRNA-34a in lipopolysaccharide-induced acute respiratory distress syndrome and its mechanism of action

Abstract:

Objective：To investigate the significance of the expression of microRNA-34a（miR-34a） in lipopolysaccharide（LPS）-in－duced acute respiratory distress syndrome（ARDS） and its mechanism of action. Methods：Forty male Sprague-Dawley rats were ran－domly divided into five groups：control group and 10 mg/kg LPS intraperitoneal injection groups（3，6，12，and 24 hours）；the human alveolar type Ⅱ epithelial cell line（A549） was divided into five groups：control group and 10 μg/mL LPS stimulation groups（3，6，12，and 24 hours）. The A549 cells were transfected with a miR-34a inhibitor and were treated with 10 μg/mL LPS（added 24 hours later） for 24 hours. The wet/dry weight（W/D） ratio of the lungs was measured and the histopathological changes in the lung tissue were evaluated. Quantitative real-time polymerase chain reaction（qRT-PCR） was used to determine the expression of miR-34a in the lung tissue and cells；enzyme-linked immunosorbent assay was used to determine the concentrations of tumor necrosis factor-α（TNF-α） and interleukin-1 beta（IL-1β） in the lung tissue and cells；Western blot was used to determine the protein expression of phos－phatidylinositol 3-kinase（PI3K） and phosphorylated protein kinase B（p-AKT） in the cells. Results：The W/D ratio of the lungs was significantly higher in the experimental groups than in the control group. The hematoxylin-eosin staining indicated that the experimental groups showed the presence of thickened alveolar septa in the lung tissue，pink edema fluids in the alveolar cavities，and inflammatory cell infiltration and hemorrhage in the pulmonary interstitium. The expression of miR-34a，the concentrations of TNF-α and IL-1β，and the protein expression of PI3K and p-AKT were higher in the experimental groups than in the control group at each time point，with a positive correlation observed between the expression of miR-34a and the concentrations of TNF-α and IL-1β. Transfection with the miR-34a inhibitor significantly down-regulated the concentrations of TNF-α and IL-1β and the protein expression of PI3K and p-AKT in the LPS-treated A549 cells. Conclusion：miR-34a can attenuate LPS-induced lung injury by inhibiting the PI3K/AKT signaling pathway，which provides a new target for ARDS treatment.