L-Theanine prevents alcoholic liver injury through enhancing the antioxidant capability of hepatocytes

L-Theanine is a unique amino acid in green tea. We here evaluated the protective effects of L-theanine on ethanol-induced liver injury in vitro and in vivo. Our results revealed that L-theanine significantly protected hepatocytes against ethanol-induced cell cytotoxicity which displayed by decrease of viability and increase of LDH and AST. Furthermore, the experiments of DAPI staining, pro-caspase3 level and PARP cleavage determination indicated that L-theanine inhibited ethanol-induced L02 cell apoptosis. Mechanically, L-theanine inhibited loss of mitochondrial membrane potential and prevented cytochrome c release from mitochondria in ethanol-treated L02 cells. L-Theanine also prevented ethanol-triggered ROS and MDA generation in L02 cells. L-Theanine restored the antioxidant capability of hepatocytes including GSH content and SOD activity which were reduced by ethanol. In vivo experiments showed that L-theanine significantly inhibited ethanol-stimulated the increase of ALT, AST, TG and MDA in mice. Histopathological examination demonstrated that L-theanine pretreated to mice apparently diminished ethanol-induced fat droplets. In accordance with the in vitro study, L-theanine significantly inhibited ethanol-induced reduction of mouse antioxidant capability which included the activities of SOD, CAT and GR, and level of GSH. These results indicated that L-theanine prevented ethanol-induced liver injury through enhancing hepatocyte antioxidant abilities. (C) 2011 Elsevier Ltd. All rights reserved.