INDUCTION OF CYTOCHROME P-4502E1 BY ETHANOL IN RAT KUPFFER CELLS

Ethanol has been shown to affect several Kupffer cell functions, but t he mechanisms underlying these changes are unknown. One possible media tor is cytochrome P-4502E1 (CYP2E1), an ethanol-inducible enzyme that has been associated with toxic effects in the liver, as well as in man y extrahepatic organs. To assess whether CYP2E1 can be induced by etha nol in Kupffer cells, male rats pair-fed ethanol-containing or control Lieber-DeCarli diets for 3 weeks were studied. Immunoblotting experim ents showed that ethanol-treatment caused a 7-fold increase in CYP2E1 content both in Kupffer cells and hepatocytes. When expressed per mill igram of S9 protein, the content of CYP2E1 in Kupffer cells was, howev er, 10 times lower than in hepatocytes. Immunohistochemical studies re vealed that CYP2E1 is located in the endoplasmic reticulum of Kupffer cells in vivo and that it is also present in isolated Kupffer cells. I n both Kupffer cells and hepatocytes, ethanol feeding increased the hy droxylation of p-nitrophenol, a relatively specific substrate for CYP2 E1, demonstrating that the induced CYP2E1 was catalytically active. Th is reaction was significantly inhibited by anti-CYP2E1 IgG in both typ es of cells. Although CYP2E1 may not be the predominant pathway for et hanol metabolism in hepatocytes, it is possibly the major one in Kupff er cells. Thus, the induction of CYP2E1 by ethanol in these cells coul d cause significant changes in intracellular acetaldehyde concentratio ns which, together with increased lipid peroxidation, may contribute t o the development of alcoholic liver injury.