Chronic Alcohol-Induced Liver Injury and Oxidant Stress is Decreased in Cytochrome P4502E1 Knockout Mice and Restored in Humanized Cytochrome P4502E1 Knockin Mice

摘要

A major pathway for chronic ethanol-induced liver injury is ethanol-induced oxidant stress. Several pathways contribute to mechanisms by which ethanol induces oxidant stress. While some studies support a role for cytochrome P450 2E1 (CYP2E1), others do not. Most previous studies were conducted in the intragastric infusion model of ethanol administration. There is a need to develop oral models of significant liver injury and to evaluate the possible role of CYP2E1 in ethanol actions in such models. We evaluated chronic ethanol-induced liver injury, steatosis and oxidant stress in wild type (WT) mice, CYP2E1 knockout (KO) mice and in humanized CYP2E1 knockin (KI) mice, where the human 2E1 was added back to mice deficient in the mouse 2E1. WT mice and the CYP2E1 KO and KI mice (both provided by Dr F. Gonzalez, NCI) were fed a high fat Lieber-DeCarli ethanol liquid diet for 3 weeks; pair-fed controls received dextrose. Ethanol produced fatty liver and oxidant stress in WT mice but liver injury (transaminases, histopathology) was minimal. Ethanol-induced steatosis and oxidant stress was blunted in the KO mice (no liver injury) but restored in the KI mice. Signicant liver injury was produced in the ethanol-fed KI mice with elevated transaminases, necrosis, and increased levels of collagen type 1 and smooth muscle actin. This liver injury in the KI mice was associated with elevated oxidant stress and elevated levels of the human CYP2E1 compared to levels of the mouse 2E1 in WT mice. Activation of JNK and decreased levels of Bcl-2 and Bcl-XL were observed in the ethanol-fed KI mice compared to the other groups. Fatty liver in the WT and the KI mice was associated with lower levels of PPAR alpha and acyl CoA oxidase. No such changes were found in the ethanol-fed KO mice. These results show that CYP2E1 plays a major role in ethanol-induced fatty liver and oxidant stress. It is the absence of CYP2E1 in the KO mice responsible for the blunting of steatosis and oxidant stress since restoring the CYP2E1 restores the fatty liver and oxidant stress. Moreover, it is the human CYP2E1 which restores these effects of ethanol which suggests that results on fatty liver and oxidant stress from rodent models of ethanol intake and mouse CYP2E1 can be extrapolated to human models of ethanol intake and to human CYP2E1.