Oxidative stress promotes pathologic polyploidization in nonalcoholic fatty liver disease
Géraldine Gentric, … , Séverine Celton-Morizur, Chantal Desdouets
Géraldine Gentric, … , Séverine Celton-Morizur, Chantal Desdouets
Published January 26, 2015
Citation Information: J Clin Invest. 2015;125(3):981-992. https://doi.org/10.1172/JCI73957.
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Research Article Hepatology

Oxidative stress promotes pathologic polyploidization in nonalcoholic fatty liver disease

Abstract

Polyploidization is one of the most dramatic changes that can occur in the genome. In the liver, physiological polyploidization events occur during both liver development and throughout adult life. Here, we determined that a pathological polyploidization takes place in nonalcoholic fatty liver disease (NAFLD), a widespread hepatic metabolic disorder that is believed to be a risk factor for hepatocellular carcinoma (HCC). In murine models of NAFLD, the parenchyma of fatty livers displayed alterations of the polyploidization process, including the presence of a large proportion of highly polyploid mononuclear cells, which are rarely observed in normal hepatic parenchyma. Biopsies from patients with nonalcoholic steatohepatitis (NASH) revealed the presence of alterations in hepatocyte ploidy compared with tissue from control individuals. Hepatocytes from NAFLD mice revealed that progression through the S/G2 phases of the cell cycle was inefficient. This alteration was associated with activation of a G2/M DNA damage checkpoint, which prevented activation of the cyclin B1/CDK1 complex. Furthermore, we determined that oxidative stress promotes the appearance of highly polyploid cells, and antioxidant-treated NAFLD hepatocytes resumed normal cell division and returned to a physiological state of polyploidy. Collectively, these findings indicate that oxidative stress promotes pathological polyploidization and suggest that this is an early event in NAFLD that may contribute to HCC development.

Authors

Géraldine Gentric, Vanessa Maillet, Valérie Paradis, Dominique Couton, Antoine L’Hermitte, Ganna Panasyuk, Bernard Fromenty, Séverine Celton-Morizur, Chantal Desdouets

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Figure 7

Antioxidant treatment prevents activation of the G2/M DNA damage checkpoint and rescues normal hepatocyte polyploidy.

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Antioxidant treatment prevents activation of the G2/M DNA damage checkpo...
(A) DHE staining of hepatocytes (60 hours of culture). The ROS-sensitive vital dye DHE (red) was used to detect the production of superoxide (scale bar: 20 μm). The abundance of Gpx3 and Hba1 mRNA was assessed by qPCR in WT hepatocytes and in ob/ob hepatocytes treated with NAC or not treated (n = 4). *P < 0.05, **P < 0.01, Student’s t test. (B) Quantitative analysis of BrdU labeling. Data represent mean ± SEM of 4 independent cultures. **P < 0.01, Student’s t test. (C) Western blot analysis of phosphorylated ATR (Ser428) (60 hours of culture). γ-Tubulin was used as a loading control. The Western blot is representative of 4 different cultures. (D) DHE immunostaining of liver sections isolated from ob/ob mice treated with NAC for 10 weeks or from ob/ob mice that were not treated (n = 3 per group) (scale bar: 20 μm). The abundance of Gpx3 and Hba1 mRNA was assessed by qPCR (n = 3 per group). *P < 0.05, **P < 0.01, ***P < 0.001, Student’s t test. (E) Analysis of nuclear ploidy in ob/ob mice treated or not with NAC. Box plots of the percentage of diploid (2n) and highly polyploid (≥8n) hepatocytes relative to all mononuclear hepatocytes. The bottom, central, and top lines of each box represent the first quartile, median, and third quartile of the distribution, respectively (n = 3 per group). *P < 0.05, ***P < 0.001, Student’s t test.