The influence of alcohol on acetaminophen hepatotoxicity: CYP2E1 induction and selective mitochondrial glutathione depletion

Enhanced acetaminophen (APAP) hepatotoxicity has been reported in alcoholics. The prevalence of the interaction is extremely low given the widespread use of APAP and the incidence of alcohol abuse. The purpose of this dissertation was to assess whether selective depletion of liver mitochondrial glutathione (GSH) by chronic ethanol potentiates APAP hepatotoxicity beyond that seen as a consequence of cytochrome (CYP) 2E1 induction. The time-course after ethanol withdrawal and ethanol-dose dependence of mitochondrial GSH depletion were established to address the low prevalence of the interaction.; Rats were fed the Lieber-DeCarli diet (36% energy by ethanol) or an equal caloric liquid diet ad libitum for 10 days or 6 weeks. The metabolism and toxicity of APAP were evaluated in liver slices. Ethanol induced CYP2E1 by 2-fold in both 10-day and 6-week groups. Partial CYP2E1 inhibition by diethyldithiocarbamate diminished this induction effect in both groups. APAP toxicity in liver slices was higher in the 6-week ethanol group than the 10-day ethanol group. Diethyldithiocarbamate abolished APAP toxicity in the 10-day ethanol group, however, it only partially blocked toxicity in the 6-week group. Selective depletion of liver mitochondrial GSH was observed only in the 6-week group. The GSH-depleted mitochondria were ∼50% more susceptible to mitochondrial succinate dehydrogenase inactivation induced by the APAP toxic metabolite N-acetyl p-benzoquinoneimine (NAPQI).; The highest ethanol containing diet (36% dietary energy) caused maximal mitochondrial GSH depletion, which was restored 17 hrs after ethanol-withdrawal. Modulation of mitochondrial GSH closely followed that of CYP2E1. Accordingly, enhanced APAP toxicity in liver slices from ethanol fed rats disappeared when ethanol dose was decreased, and when ethanol was removed from the diet.; NAPQI formation and APAP adduct formation were detected in isolated liver mitochondria incubated with APAP, and were increased in liver mitochondria from ethanol-fed rats. The importance of local NAPQI formation in mitochondria is discussed.; In conclusion, high dose ethanol feeding chronically potentiated APAP hepatotoxicity via CYP2E1 induction and selective mitochondrial GSH depletion. The effect reversed rapidly when ethanol was withdrawn. The time window for both mechanisms is narrow, which may in part explain why the enhanced effects of the interaction seem to be observed rarely given the frequency of combined use.