The role of Cytochrom P4502E1 in Alcoholic Liver Disease and alcohol mediated carcinogenesis

Abstract

Various factors are involved in the pathogenesis of alcoholic liver disease (ALD) and ethanol-mediated carcinogenesis. In addition to genetic, epigenetic and immunologic mechanisms, acetaldehyde-associated toxicity, oxidative stress as well as cytokine-mediated inflammation are of major importance. Oxidative stress, with the generation of reactive oxygen species (ROS), develops either in inflammation (alcoholic hepatitis) or during oxidation of ethanol via cytochrome P4502E1 (CYP2E1). CYP2E1 is induced by ethanol, oxidizes ethanol to acetaldehyde, and generates ROS during this process. ROS results in protein damage, enhanced fibrogenesis and DNA lesions. Furthermore, CYP2E1 induction results in an enhanced activation of various procarcinogens and an increased degradation of retinol and retinoic acid (RA), a compound responsible for cell differentiation and proliferation. An inhibition of CYP2E1 results in an improvement of ALD and chemically induced carcinogenesis in animal experiments. In humans, CYP2E1 is induced following the consumption of 40grams of ethanol per day after one week. However, the induction varies inter-individually. The mechanism for this is still unclear. Patients with ALD show a significant correlation between CYP2E1, the occurrence of highly carcinogenic etheno DNA adducts and the severity of fibrosis. First results on the effect of CYP2E1 inhibition by chlormethiazole, a specific CYP2E1 inhibitor on ALD, can be expected soon.