title: Peroxynitrite is a critical mediator of acetaminophen hepatotoxicity in murine livers: protection by glutathione.
abstract: Acetaminophen (AAP) overdose causes formation of nitrotyrosine, a footprint of peroxynitrite, in centrilobular hepatocytes. The importance of peroxynitrite for the pathophysiology, however, is unclear. C3Heb/FeJ mice were treated with 300 mg/kg AAP. To accelerate the restoration of hepatic glutathione (GSH) levels as potential endogenous scavengers of peroxynitrite, some groups of animals received 200 mg of GSH/kg i.v. at different time points after AAP. AAP induced severe liver cell damage at 6 h. Total liver and mitochondrial glutathione levels decreased by >90% at 1 h but recovered to 75 and 45%, respectively, of untreated values at 6 h after AAP. In addition, the hepatic and mitochondrial glutathione disulfide (GSSG) content was significantly increased over baseline, suggesting a mitochondrial oxidant stress. Moreover, centrilobular hepatocytes stained for nitrotyrosine. Treatment with GSH at t = 0 restored hepatic GSH levels and completely prevented the mitochondrial oxidant stress, peroxynitrite formation, and liver cell injury. In contrast, treatment at 1.5 and 2.25 h restored hepatic and mitochondrial GSH levels but did not prevent the increase in GSSG formation. Nitrotyrosine adduct formation and liver injury, however, was substantially reduced. GSH treatment at 3 h after AAP was ineffective. Similar results were obtained when these experiments were repeated with glutathione peroxidase-deficient animals. Our data suggest that early GSH treatment (t = 0) prevented cell injury by improving the detoxification of the reactive metabolite of AAP. Delayed GSH treatment enhanced hepatic GSH levels, which scavenged peroxynitrite in a spontaneous reaction. Thus, peroxynitrite is an important mediator of AAP-induced liver cell necrosis.
authors.affiliation: Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Little Rock, AR 72205, USA.
authors.forename: Tamara R
authors.initials: TR
authors.lastname: Knight
authors.forename: Ye-Shih
authors.initials: YS
authors.lastname: Ho
authors.forename: Anwar
authors.initials: A
authors.lastname: Farhood
authors.forename: Hartmut
authors.initials: H
authors.lastname: Jaeschke
mesh_terms: D000082:Acetaminophen / Q000037:antagonists & inhibitors / Q000633:toxicity*; D000410:Alanine Transaminase / Q000378:metabolism; D018712:Analgesics, Non-Narcotic / Q000037:antagonists & inhibitors / Q000633:toxicity*; D000818:Animals; D000931:Antidotes / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D056486:Chemical and Drug Induced Liver Injury / Q000473:pathology*; D005978:Glutathione / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D007150:Immunohistochemistry; D007275:Injections, Intravenous; D008099:Liver / Q000473:pathology*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008930:Mitochondria, Liver / Q000378:metabolism; D009336:Necrosis; D030421:Peroxynitrous Acid / Q000378:metabolism / Q000502:physiology*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D018712:Analgesics, Non-Narcotic; D000931:Antidotes; D030421:Peroxynitrous Acid; D012710:Serum Albumin, Bovine; C002744:3-nitrotyrosine; D000082:Acetaminophen; D014443:Tyrosine; D000410:Alanine Transaminase; D005978:Glutathione