Oral N-acetylcysteine rescues lethality of hepatocyte-specific Gclc-knockout mice, providing a model for hepatic cirrhosis

Abstract

Background & aims: Certain liver diseases have been associated with depletion of glutathione (GSH), the major antioxidant in the liver. A recent report about Gclc(h/h) mice with a hepatocyte-specific ablation of Gclc (the gene encoding the catalytic subunit of the rate-limiting enzyme in GSH synthesis) has shown an essential role of GSH in hepatic function. Gclc(h/h) mice develop severe steatosis and die of liver failure within one month, due to ~95% depletion of hepatic GSH; mitochondria are the major affected organelles, displaying abnormal ultrastructure and impaired functioning.

Methods: Gclc(h/h) mice were fed with L-N-acetylcysteine (NAC; 10 g/L) in drinking water, starting at postnatal day 18.

Results: Gclc(h/h) mice were rescued by use of NAC supplementation, and survived until adulthood. NAC replenished the mitochondrial GSH pool and attenuated mitochondrial damage, with accompanying diminished hepatic steatosis; however, abnormal liver biochemical tests, hepatocyte death, and hepatic oxidative stress persisted in the rescued mice. At 50 days of age, the liver from rescued Gclc(h/h) mice started to display characteristics of fibrosis and at age 120 days, macronodular cirrhosis was observed. Immunohistostaining for liver-specific markers as well as the expression profile of hepatic cytokines indicated that the repopulation of hepatocytes in the cirrhotic nodules involved the expansion of oval cells.

Conclusions: Replenishment of mitochondrial GSH and restoration of mitochondrial function by NAC prevents mortality caused by the loss of hepatocyte GSH de novo synthesis, allowing steatosis to progress to a chronic stage. Thus, with NAC supplementation, Gclc(h/h) mice provide a model for the development of liver fibrosis and cirrhosis.