Vol. 30, Issue 12, 1413-1417, December 2002

Effects of Ethanol Dose and Ethanol Withdrawal on Rat Liver Mitochondrial Glutathione: Implication of Potentiated Acetaminophen Toxicity in Alcoholics

Ping Zhao and John T. Slattery

Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, Washington

Chronic ethanol consumption potentiates acetaminophen (APAP) hepatotoxicity through enhanced NAPQI formation via CYP2E1 induction and selective depletion of mitochondrial glutathione. Because the prevalence of the interaction is extremely low given the use of APAP and the incidence of alcohol abuse, we studied the effects of ethanol dose and ethanol withdrawal on selective mitochondrial glutathione (GSH) depletion and APAP toxicity in liver slices. Rats were fed the Lieber-DeCarli diet containing ethanol (0, 7, 18, 27, and 36% total energy) for 6 weeks. The highest ethanol-containing diet (36% energy as ethanol) was replaced by control diet for 2, 5, 12, and 17 h. Maximal CYP2E1 induction was caused by 36% energy as ethanol diet (2.2-fold, p < 0.05 versus control). The activity and liver protein content returned to the control level 17 h after ethanol withdrawal. The 36% energy as ethanol diet caused maximal mitochondrial GSH depletion (51%, p < 0.05 versus control), which was restored 17 h after ethanol withdrawal (22.0 ± 4.9 versus 11.7 ± 1.7 nmol/mg protein of 0 h, p < 0.01). Elevated glutathione S-transferase- release in liver slices (a measure of toxicity) was observed in rats fed 36% energy as ethanol diet (1 mM APAP: 69 ± 10 versus 3 ± 1% of control, p < 0.01). Enhanced toxicity disappeared when ethanol dose decreased and when ethanol was removed (7.2% ethanol: 3 ± 1% and 17 h: 2 ± 1%, p < 0.01 versus 0 h 36% energy as ethanol). In conclusion, high-dose ethanol potentiated APAP hepatotoxicity via CYP2E1 induction and selective mitochondrial GSH depletion. Mitochondrial GSH depletion quickly reversed when ethanol was withdrawn. The time window for both mechanisms to act in concert is narrow.