Ethanol-induced cytochrome P4502E1 causes carcinogenic etheno-DNA lesions in alcoholic liver disease.
Oxidative stress is thought to play a major role in the pathogenesis of hepatocellular cancer (HCC), a frequent complication of alcoholic liver disease (ALD). However, the underlying mechanisms are poorly understood. In hepatocytes of ALD patients, we recently detected by immunohistochemistry significantly increased levels of carcinogenic etheno-DNA adducts that are formed by the reaction of the major lipid peroxidation product, 4-hydroxynonenal (4-HNE) with nucleobases. In the current study, we show that protein-bound 4-HNE and etheno-DNA adducts both strongly correlate with cytochrome P450 2E1 (CYP2E1) expression in patients with ALD (r = 0.9, P < 0.01). Increased levels of etheno-DNA adducts were also detected in the liver of alcohol-fed lean (Fa/?) and obese (fa/fa) Zucker rats. The number of nuclei in hepatocytes stained positively for etheno-DNA adducts correlated significantly with CYP2E1 expression (r = 0.6, P = 0.03). To further assess the role of CYP2E1 in the formation of etheno-DNA adducts, HepG2 cells stably transfected with human CYP2E1 were exposed to ethanol with or without chlormethiazole (CMZ), a specific CYP2E1 inhibitor. Ethanol increased etheno-DNA adducts in the nuclei of CYP2E1-transfected HepG2 cells in a concentration-dependent and time-dependent manner, but not in vector mock-transfected control cells. CMZ blocked the generation of etheno-DNA adducts by 70%-90% (P < 0.01).


CONCLUSIONS
Our data support the assumption that ethanol-mediated induction of hepatic CYP2E1 leading inter alia to highly miscoding lipid peroxidation-derived DNA lesions may play a central role in hepatocarcinogenesis in patients with ALD.
Wang
Ying
Y
Center of Alcohol Research, Liver Disease and Nutrition, University of Heidelberg, Germany.
Millonig
Gunda
G
Nair
Jagadeesan
J
Patsenker
Eleonora
E
Stickel
Felix
F
Mueller
Sebastian
S
Bartsch
Helmut
H
Seitz
Helmut K
HK
D000328:Adult; D000368:Aged; D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D001706:Biopsy; D045744:Cell Line, Tumor; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism*; D000431:Ethanol / Q000009:adverse effects; D005260:Female; D006801:Humans; D008099:Liver / Q000378:metabolism; D008108:Liver Diseases, Alcoholic / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D051381:Rats; D011924:Rats, Zucker
D000447:Aldehydes; D018736:DNA Adducts; D000431:Ethanol; D019392:Cytochrome P-450 CYP2E1; C027576:4-hydroxy-2-nonenal