Acetaminophen-induced hepatotoxicity: role of metabolic activation, reactive oxygen/nitrogen species, and mitochondrial permeability transition.

Large doses of the analgesic acetaminophen cause centrilobular hepatic necrosis in man and in experimental animals. It has been previously shown that acetaminophen is metabolically activated by CYP enzymes to N-acetyl-p-benzoquinone imine. This species is normally detoxified by GSH, but following a toxic dose GSH is depleted and the metabolite covalently binds to a number of different proteins. Covalent binding occurs only to the cells developing necrosis. Recently we showed that these cells also contain nitrated tyrosine residues. Nitrotyrosine is mediated by peroxynitrite, a reactive nitrogen species formed by rapid reaction between nitric oxide and superoxide and is normally detoxified by GSH. Thus, acetaminophen toxicity occurs with increased oxygen/nitrogen stress. This manuscript will review current data on acetaminophen covalent binding, increased oxygen/nitrogen stress, and mitochondrial permeability transition, a toxic mechanism that is both mediated by and leads to increased oxygen/nitrogen stress.