Lipopolysaccharide-Mediated Hepatic Glutathione Depletion and Progressive Mitochondrial Damage in Mice: Protective Effect of Glutathione Monoethyl Ester☆☆☆

Overproduction of reactive oxygen intermediates (ROI) may have an important role in the pathophysiology of lipopolysaccharide-mediated liver injury. This study examined the role of cytosolic and mitochondrial glutathione in protecting hepatocytes from oxidative stress during exposure to lipopolysaccharide. In addition, the possible participation of changes of inner mitochondrial membrane permeability in lipopolysaccharide-induced hepatotoxicity was investigated. The changes of hepatic glutathione content following lipopolysaccharide challenge (2 mg/kg) were measured in mice by reverse-phase high-performance liquid chromatography. Glutathione depletion and a glutathione-rich state were produced by intraperitoneal administration of a specific inhibitor of γ-glutamyl cysteine synthetase, buthionine sulfoximine (3 mmol/kg), and by administration of glutathione monoethyl ester (10 mmol/kg), respectively. Intracellular ROI generation and the mitochondrial membrane potential were quantified by flow cytometry. Changes of inner mitochondrial membrane permeability in hepatocytes were assessed by radioactive sucrose entrapment. There was increased production of ROI along with depletion of cellular and mitochondrial glutathione in the liver after lipopolysaccharide administration. There was also a change of inner mitochondrial membrane permeability in hepatocytes, with the loss of coupled functions. Buthionine sulfoximine decreased the hepatic antioxidant capacity, worsened mitochondrial function, and reduced the survival rate of the mice. In contrast, glutathione monoethyl ester improved all of these parameters. Glutathione may have an important role in cellular defenses against lipopolysaccharide-induced liver damage in mice, and excessive oxidative stress may precipitate the mitochondrial membrane permeability transition in hepatocytes and lead to cell death.