Role of the cellular redox state in modulating acute ethanol toxicity in isolated hepatocytes.
OBJECTIVE
To propose a mechanism for ethanol induced hepatocytotoxicity.


METHODS
Hepatocytotoxicity was determined at various concentrations of oxygen and agents involved in NADH metabolism.


RESULTS
At 1% O2, hepatocytes were nearly 8-fold more susceptible to ethanol than at 95% O2 (carbogen). Cytotoxicity at 1% O2 was enhanced in the presence of glycolytic substrates that generate NADH (e.g., sorbitol or xylitol), and prevented by glycolytic substrates that reoxidise NADH (e.g., fructose or dihydroxyacetone). Susceptibility to ethanol correlated with the cytosolic redox state (lactate; pyruvate ratio). Cytotoxicity also correlated with reactive oxygen species (ROS) formation. Cytotoxicity was averted by ROS scavengers or the ferric chelator desferoxamine but was increased by hydroxylamine, a catalase inhibitor, or by prior glutathione depletion. Ethanol induced cytotoxicity was also decreased by inhibitors of alcohol/aldehyde dehydrogenases or CYP2E1, an alcohol inducible cytochrome P450.


CONCLUSIONS
A cytotoxic mechanism was proposed where the sustained increase in NADH levels, resulting from ethanol metabolism, maintains CYP2E1 in a more reduced state that increases ROS formation.
Khan
S
S
Faculty of Pharmacy, University of Toronto, Ontario, Canada.
O'Brien
P J
PJ
D000426:Alcohol Dehydrogenase / Q000037:antagonists & inhibitors; D000444:Aldehyde Dehydrogenase / Q000037:antagonists & inhibitors; D000818:Animals; D002478:Cells, Cultured; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000633:toxicity*; D016166:Free Radical Scavengers / Q000494:pharmacology; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley
D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D000431:Ethanol; D000426:Alcohol Dehydrogenase; D000444:Aldehyde Dehydrogenase