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Mitofusin 2 protects hepatocyte mitochondrial function from damage induced by GCDCA.

Chen Y, Lv L, Jiang Z, Yang H, Li S, Jiang Y - PLoS ONE (2013)

Bottom Line: In line with the mitochondrial dysfunction, the expression of Mfn2 decreased significantly under GCDCA treatment conditions.Increasing the expression of truncated Mfn2 also had a protective effect against the hepatotoxicity of GCDCA.Therapeutic approaches that target Mfn2 may have protective effects against hepatotoxic of bile acids during cholestasis.

View Article: PubMed Central - PubMed

Affiliation: Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China. cybiao717@sina.com.cn

ABSTRACT
Mitochondrial impairment is hypothesized to contribute to the pathogenesis of chronic cholestatic liver diseases. Mitofusin 2 (Mfn2) regulates mitochondrial morphology and signaling and is involved in the development of numerous mitochondrial-related diseases; however, a functional role for Mfn2 in chronic liver cholestasis which is characterized by increased levels of toxic bile acids remain unknown. Therefore, the aims of this study were to evaluate the expression levels of Mfn2 in liver samples from patients with extrahepatic cholestasis and to investigate the role Mfn2 during bile acid induced injury in vitro. Endogenous Mfn2 expression decreased in patients with extrahepatic cholestasis. Glycochenodeoxycholic acid (GCDCA) is the main toxic component of bile acid in patients with extrahepatic cholestasis. In human normal hepatocyte cells (L02), Mfn2 plays an important role in GCDCA-induced mitochondrial damage and changes in mitochondrial morphology. In line with the mitochondrial dysfunction, the expression of Mfn2 decreased significantly under GCDCA treatment conditions. Moreover, the overexpression of Mfn2 effectively attenuated mitochondrial fragmentation and reversed the mitochondrial damage observed in GCDCA-treated L02 cells. Notably, a truncated Mfn2 mutant that lacked the normal C-terminal domain lost the capacity to induce mitochondrial fusion. Increasing the expression of truncated Mfn2 also had a protective effect against the hepatotoxicity of GCDCA. Taken together, these findings indicate that the loss of Mfn2 may play a crucial role the pathogenesis of the liver damage that is observed in patients with extrahepatic cholestasis. The findings also indicate that Mfn2 may directly regulate mitochondrial metabolism independently of its primary fusion function. Therapeutic approaches that target Mfn2 may have protective effects against hepatotoxic of bile acids during cholestasis.

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Effect of the overexpression of Mfn2 or the truncated Mfn2 mutant on mitochondrial morphology and mitochondrial function in GCDCA-treated L02 cells.(A) Western blot analysis was used to detect the expression of Mfn2-GFP and the truncated Mfn2 mutant transfected into L02 cells. (B) Confocal microscope photographs indicated increased mitochondrial localization of Mfn2 and the truncated Mfn2 mutant and their roles in mitochondrial morphology. (C) Proportions of cells with fragmented mitochondrial pattern was determined in at least six different cultures under basal conditions (untreated), and after the L02 cells were treated with various doses (25, 50, 75, or 100 µM) of GCDCA for 6 h. The results are expressed as a percentage of the control value, which was set at 100%. The values are the means ± SEM. *P<0.05 versus the control group, #P<0.05, ##P<0.01 versus the GCDCA group, n = 6.
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pone-0065455-g004: Effect of the overexpression of Mfn2 or the truncated Mfn2 mutant on mitochondrial morphology and mitochondrial function in GCDCA-treated L02 cells.(A) Western blot analysis was used to detect the expression of Mfn2-GFP and the truncated Mfn2 mutant transfected into L02 cells. (B) Confocal microscope photographs indicated increased mitochondrial localization of Mfn2 and the truncated Mfn2 mutant and their roles in mitochondrial morphology. (C) Proportions of cells with fragmented mitochondrial pattern was determined in at least six different cultures under basal conditions (untreated), and after the L02 cells were treated with various doses (25, 50, 75, or 100 µM) of GCDCA for 6 h. The results are expressed as a percentage of the control value, which was set at 100%. The values are the means ± SEM. *P<0.05 versus the control group, #P<0.05, ##P<0.01 versus the GCDCA group, n = 6.

Mentions: To assess whether the restoration of Mfn2 expression is sufficient to enhance mitochondrial activity in GCDCA-induced hepatotoxicity, we overexpressed Mfn2 in L02 cells by transient transfection. Mfn2 overexpression efficiently reversed the decrease in cell viability in L02 cells that had been treated with 75 µM GCDCA for 6 h (Fig. 4C). In parallel, Mfn2-overexpressing cells exhibited marked increases in ATP (Fig. 4D) and ΔΨm (Fig. 4E) levels and a decrease in the rate of ROS production (Fig. 4F). Notably, overexpressed Mfn2 efficiently reversed the increase in mitochondrial fragmentation in the transfected L02 cells that had been incubated with GCDCA (Fig. 4B).


Mitofusin 2 protects hepatocyte mitochondrial function from damage induced by GCDCA.

Chen Y, Lv L, Jiang Z, Yang H, Li S, Jiang Y - PLoS ONE (2013)

Effect of the overexpression of Mfn2 or the truncated Mfn2 mutant on mitochondrial morphology and mitochondrial function in GCDCA-treated L02 cells.(A) Western blot analysis was used to detect the expression of Mfn2-GFP and the truncated Mfn2 mutant transfected into L02 cells. (B) Confocal microscope photographs indicated increased mitochondrial localization of Mfn2 and the truncated Mfn2 mutant and their roles in mitochondrial morphology. (C) Proportions of cells with fragmented mitochondrial pattern was determined in at least six different cultures under basal conditions (untreated), and after the L02 cells were treated with various doses (25, 50, 75, or 100 µM) of GCDCA for 6 h. The results are expressed as a percentage of the control value, which was set at 100%. The values are the means ± SEM. *P<0.05 versus the control group, #P<0.05, ##P<0.01 versus the GCDCA group, n = 6.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3675030&req=5

pone-0065455-g004: Effect of the overexpression of Mfn2 or the truncated Mfn2 mutant on mitochondrial morphology and mitochondrial function in GCDCA-treated L02 cells.(A) Western blot analysis was used to detect the expression of Mfn2-GFP and the truncated Mfn2 mutant transfected into L02 cells. (B) Confocal microscope photographs indicated increased mitochondrial localization of Mfn2 and the truncated Mfn2 mutant and their roles in mitochondrial morphology. (C) Proportions of cells with fragmented mitochondrial pattern was determined in at least six different cultures under basal conditions (untreated), and after the L02 cells were treated with various doses (25, 50, 75, or 100 µM) of GCDCA for 6 h. The results are expressed as a percentage of the control value, which was set at 100%. The values are the means ± SEM. *P<0.05 versus the control group, #P<0.05, ##P<0.01 versus the GCDCA group, n = 6.
Mentions: To assess whether the restoration of Mfn2 expression is sufficient to enhance mitochondrial activity in GCDCA-induced hepatotoxicity, we overexpressed Mfn2 in L02 cells by transient transfection. Mfn2 overexpression efficiently reversed the decrease in cell viability in L02 cells that had been treated with 75 µM GCDCA for 6 h (Fig. 4C). In parallel, Mfn2-overexpressing cells exhibited marked increases in ATP (Fig. 4D) and ΔΨm (Fig. 4E) levels and a decrease in the rate of ROS production (Fig. 4F). Notably, overexpressed Mfn2 efficiently reversed the increase in mitochondrial fragmentation in the transfected L02 cells that had been incubated with GCDCA (Fig. 4B).

Bottom Line: In line with the mitochondrial dysfunction, the expression of Mfn2 decreased significantly under GCDCA treatment conditions.Increasing the expression of truncated Mfn2 also had a protective effect against the hepatotoxicity of GCDCA.Therapeutic approaches that target Mfn2 may have protective effects against hepatotoxic of bile acids during cholestasis.

View Article: PubMed Central - PubMed

Affiliation: Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China. cybiao717@sina.com.cn

ABSTRACT
Mitochondrial impairment is hypothesized to contribute to the pathogenesis of chronic cholestatic liver diseases. Mitofusin 2 (Mfn2) regulates mitochondrial morphology and signaling and is involved in the development of numerous mitochondrial-related diseases; however, a functional role for Mfn2 in chronic liver cholestasis which is characterized by increased levels of toxic bile acids remain unknown. Therefore, the aims of this study were to evaluate the expression levels of Mfn2 in liver samples from patients with extrahepatic cholestasis and to investigate the role Mfn2 during bile acid induced injury in vitro. Endogenous Mfn2 expression decreased in patients with extrahepatic cholestasis. Glycochenodeoxycholic acid (GCDCA) is the main toxic component of bile acid in patients with extrahepatic cholestasis. In human normal hepatocyte cells (L02), Mfn2 plays an important role in GCDCA-induced mitochondrial damage and changes in mitochondrial morphology. In line with the mitochondrial dysfunction, the expression of Mfn2 decreased significantly under GCDCA treatment conditions. Moreover, the overexpression of Mfn2 effectively attenuated mitochondrial fragmentation and reversed the mitochondrial damage observed in GCDCA-treated L02 cells. Notably, a truncated Mfn2 mutant that lacked the normal C-terminal domain lost the capacity to induce mitochondrial fusion. Increasing the expression of truncated Mfn2 also had a protective effect against the hepatotoxicity of GCDCA. Taken together, these findings indicate that the loss of Mfn2 may play a crucial role the pathogenesis of the liver damage that is observed in patients with extrahepatic cholestasis. The findings also indicate that Mfn2 may directly regulate mitochondrial metabolism independently of its primary fusion function. Therapeutic approaches that target Mfn2 may have protective effects against hepatotoxic of bile acids during cholestasis.

Show MeSH
Related in: MedlinePlus