Objective: To investigate the protective effect of transfected microRNA-146a (miR-146a) on mice with sepsis-induced acute lung injury (ALI) in vivo.
Methods: Twenty-four healthy male BALB/C mice were randomly divided into sham group, sepsis group, transfection group and transfection control group, each n=6. Mice in transfection group were given miR-146a agomir loaded by in vivo-jetPEITM via airway before reproduction of model, and mice in transfection control group were given negative control loaded by in vivo-jetPEITM only via airway. The septic model was reproduced by cecal ligation and puncture (CLP) 12 hours after transfection , and the mice in the sham group underwent laparotomy and closure only without ligation and puncture of the cecum. The mice of each group were sacrificed at 24 hours post-operation. The expression of miR-146a in lung tissue was determined by real time fluorescence quantitative reverse transcription-polymerase chain reaction (RT-qPCR), and the quantity of tumor necrosis factor-α (TNF-α) in the bronchial alveolar lavage fluid (BALF) was determined with enzyme-linked immunosorbent assay (ELISA). The wet/dry ratio of lung (W/D) was determined. The pathohistological changes in the lung were observed and scored.
Results: The expression of miR-146a showed a significant increase in sepsis group, transfection group and transfection control group, which were (3.56±0.43), (27.64±3.46) and (3.72±0.54) folds of that in sham group, respectively (P<0.05 or P<0.01). The miR-146a expression in transfection group was significantly increased compared with sepsis group and transfection control group (both P<0.01), but no statistical difference in the expression was found between sepsis group and transfection control group (P>0.05). Compared with the sham group, higher level of TNF-α in the BALF was found in the sepsis group, transfection group and transfection control group (ng/L: 511.65±43.47, 305.74±34.76, 492.27±42.21 vs. 50.72±7.23, all P<0.01). The level of TNF-α in transfection group was significantly lower than that in sepsis group and transfection control group (both P<0.01). Compared with the sham group, the W/D ratio of lung in sepsis group, transfection group and transfection control group showed a significant increase (6.11±0.32, 5.02±0.29, 6.05±0.43 vs. 4.18±0.10, all P<0.01). The W/D ratio of lung in transfection group was significantly lower than that of sepsis group and transfection control group (both P<0.01). The lung injury score of transfection group was significantly lower than that of sepsis group and transfection control group (6.12±0.75 vs. 10.53±1.52, 9.73±1.08, both P<0.01).
Conclusions: miR-146a agomir loaded by in vivo-jetPEITM instillation into airway was able to increase the expression of miR-146a in the lung tissue of septic mice. Up-regulation of miR-146a inhibit the release of the inflammatory cytokine TNF-α stimulated by sepsis, and alleviate inflammatory reaction and lung tissue injury in mice with sepsis-induced ALI.