Overexpression of mitofusion 2 inhibits acute respiratory distress syndrome pulmonary fibrosis and its mechanism / 中华危重病急救医学

ABSTRACT

Objective:To study the inhibitory effect of overexpression of mitofusion 2 (Mfn2) protein on acute respiratory distress syndrome (ARDS) pulmonary fibrosis and its mechanism.Methods:Human embryo lung fibroblasts (HELF) were cultured in vitro, and digested and passaged when the adherent rate of HELF reached 80%, and then the cells in good condition were selected for experiment. The ARDS cell model was reproduced by 5 mg/L of lipopolysaccharide (LPS, LPS group); 75 mol/L adenovirus vector carrying mitofusion 2 (Adv-Mfn2) was transfected into HELF (Adv-Mfn2+LPS group); at the same time, blank control group (complete medium culture) and Adv-vector+LPS group were set as controls. The cell proliferation was observed by sulforhodamine B (SRB) method at 0, 12, 24, 36 and 48 hours. After Hoechst 33342 staining, the morphological changes were observed under confocal microscope. Western blotting was used to detect the protein expressions of Bcl-2 and caspase-3. Real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) was used to detect the gene expressions of Bcl-2 and caspase-3. Results:After LPS stimulation for 12-48 hours, the cell proliferation rates in the LPS group increased gradually, which were significantly higher than those in the blank control group [12 hours: (10.75±1.51)% vs. (0.73±1.22)%, 24 hours: (20.09±1.71)% vs. (1.15±1.12)%, 36 hours: (20.58±1.55)% vs. (1.20±1.12)%, 48 hours: (21.30±1.51)% vs. (1.23±1.10)%, all P < 0.01]. There was no statistically significant difference in the cell proliferation rate between the LPS group and the Adv-vector+LPS group. After overexpression of Mfn2, the cell proliferation rates at 12, 24, 36, 48 hours in the Adv-Mfn2+LPS group were (8.93±1.14)%, (10.52±1.24)%, (10.72±1.30)%, and (10.91±1.20)%, which were significantly lower than those in the LPS group (all P < 0.05). Confocal microscopy showed that some cells in the blank control group had nuclei of different sizes, and some nuclei fragmented or shrank to form apoptotic bodies. The nuclei of the cells in the LPS and Adv-vector+LPS groups were round or oval in size, and only a few apoptotic cells appeared. When Mfn2 was overexpressed, there were more apoptotic cells in the visual field in the Adv-Mfn2+LPS group than LPS group. Western blotting and RT-qPCR results showed that Bcl-2 expressions increased significantly after LPS stimulation in the LPS group as compared with the blank control group [Bcl-2 protein (Bcl-2/GAPDH): 0.68±0.01 vs. 0.29±0.01, Bcl-2 mRNA (2 -ΔΔCT): 2.23±0.34 vs. 1.00±0.00, both P < 0.01], and caspase-3 expressions decreased significantly [caspase-3 protein (caspase-3/GAPDH): 0.37±0.02 vs. 0.66±0.02, caspase-3 mRNA (2 -ΔΔCT): 0.31±0.05 vs. 1.00±0.00, both P < 0.01]. Compared with LPS group, the expressions of Bcl-2 after overexpression of Mfn2 in the Adv-Mfn2+LPS group were down-regulated [Bcl-2 protein (Bcl-2/GAPDH): 0.46±0.01 vs. 0.68±0.01, Bcl-2 mRNA (2 -ΔΔCT): 1.45±0.14 vs. 2.23±0.34, both P < 0.01], and the expressions of caspase-3 were up-regulated [caspase-3 protein (caspase-3/GAPDH): 0.54±0.02 vs. 0.37±0.02, caspase-3 mRNA (2 -ΔΔCT): 0.88±0.10 vs. 0.31±0.05, both P < 0.01]. Conclusion:Mfn2 protein is involved in ARDS pulmonary fibrosis, which may be related to mitochondrial mediated inhibition of cell proliferation.