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Objective:To investigate the role of mitofusion 2 (Mfn2) in high glucose (HG)-induced endoplasmic reticulum stress (ERS) and apoptosis of podocytes.Methods:(1) Streptozocin was used to induce a diabetes mellitus (DM) rat model. Renal histopathological changes in rats were observed by HE staining. Expression of Mfn2 and CCAAT/enhancer-binding protein homologous protein (CHOP) in glomeruli was observed by immunohistochemistry. Protein levels of Mfn2, protein kinase RNA-like ER kinase (PERK), phospho(p)-PERK, and CHOP in glomeruli were analyzed by Western blotting. (2) Conditionally immortalized human podocytes (HPC) cultured in vitro were divided into control, mannitol (MA) and HG groups. Expression of Mfn2 was observed by immunofluorescence. Protein levels of Mfn2, p-PERK, PERK and CHOP in HPC were analyzed by Western blotting. Podocyte apoptosis in each group was evaluated by flow cytometry with AnnexinⅤ-PE/7AAD double staining method. (3) HPC were divided into control, HG, HG+Mfn2-Myc plasmid-transfected and HG+control plasmid-transfected groups. Protein levels of Mfn2, p-PERK, PERK and CHOP in HPC were analyzed by Western blotting. Expression of CHOP was observed by immunofluorescence. Mitochondrial membrane potential in each group was observed by mitochondrial membrane potential assay kit with JC-1. Podocyte apoptosis in each group was evaluated by flow cytometry with AnnexinⅤ-PE/7AAD double staining method. Results:(1) Compared with the control group, the glomerular mesangial matrix of the DM group rats was significantly proliferated, and the expression of Mfn2 was down-regulated with the expression of ERS-related proteins p-PERK/PERK and CHOP up-regulated (all P<0.05). (2) Compared with the control group, Mfn2 was down-regulated and p-PERK/PERK and CHOP were up-regulated in HPC of HG group (all P<0.05). Apoptosis of HPC was also increased in HG group. There was no significant difference in the above indicators between the control group and the mannitol group (all P>0.05). (3) Compared with the HG group, mitochondrial membrane potential of HPC was alleviated and apoptosis of HPC was decreased in HG+Mfn2-Myc plasmid-transfected group ( P<0.05). P-PERK/PERK and CHOP were down-regulated in HG+Mfn2-Myc plasmid-transfected group (both P<0.05). There was no significant difference in the above indicators between the HG group and the HG+control plasmid-transfected group (all P>0.05). Conclusions:Mfn2 down-regulation in HG-stimulated podocytes may induce ERS to increase apoptosis of podocytes. Up-regulation of Mfn2 can alleviate the HG-induced ERS and apoptosis in podocytes.
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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.
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Objective To observe the effect of mitofusion 2 (MFN2) on the proliferation of prostate cancer cells and its molecular mechanism. Methods Lentivirus containing the MFN2 coding sequence (Lenti-MFN2) were used to infect the prostate cancer cell lines DU-145 and LNCaP, and the lentivirus containing the green fluorescent protein gene (Lenti-GFP) were defined as the control. Real-time quantitative PCR (qRT-PCR) and Western blot were used to detect the expression of MFN2 mRNA and protein in the infected cells. MTT assay and colony formation assay were used to detect the cell proliferation. Cell cycle distribution was measured by flow cytometry.Western blot was used to detect the expression of Ras,p-Raf and p-Erk1/2 proteins in infected cells. Results The expressions of MFN2 mRNA in DU-145 and LNCaP cells of Lenti-MFN2 group were 2.79±0.91 and 3.87±1.06, which were higher than those in Lenti-GFP group (1.02± 0.27 and 1.13±0.59),the differences were statistically significant(t=3.726,P=0.010;t=5.209,P =0.002). Compared with Lenti-GFP group, the expression of MFN2 protein in Lenti-MFN2 group was increased. The number of colonies formed in DU-145 and LNCaP cells of Lenti-MFN2 group was 147.42±32.91 and 130.26± 62.47, respectively, which was lower than that of the Lenti-GFP group (255.46±50.91 and 238.10±49.77), the differences were statistically significant (t =3.565, P=0.012; t =2.700, P=0.036). The cell cycle was arrested at G0/G1phase,and the expressions of Ras, p-Raf and p-Erk1/2 proteins were significantly decreased. Conclusion MFN2 can inhibit the proliferation of prostate cancer cells,and its mechanism may be related to the inhibition of activation of Ras-Raf1-Erk1/2 signaling pathway.