title: Protection against acetaminophen-induced liver injury by allopurinol is dependent on aldehyde oxidase-mediated liver preconditioning.
abstract: Acetaminophen (APAP) overdose causes severe and occasionally fatal liver injury. Numerous drugs that attenuate APAP toxicity have been described. However these compounds frequently protect by cytochrome P450 inhibition, thereby preventing the initiating step of toxicity. We have previously shown that pretreatment with allopurinol can effectively protect against APAP toxicity, but the mechanism remains unclear. In the current study, C3HeB/FeJ mice were administered allopurinol 18h or 1h prior to an APAP overdose. Administration of allopurinol 18h prior to APAP overdose resulted in an 88% reduction in liver injury (serum ALT) 6h after APAP; however, 1h pretreatment offered no protection. APAP-cysteine adducts and glutathione depletion kinetics were similar with or without allopurinol pretreatment. The phosphorylation and mitochondrial translocation of c-jun-N-terminal-kinase (JNK) have been implicated in the progression of APAP toxicity. In our study we showed equivalent early JNK activation (2h) however late JNK activation (6h) was attenuated in allopurinol treated mice, which suggests that later JNK activation is more critical for the toxicity. Additional mice were administered oxypurinol (primary metabolite of allopurinol) 18h or 1h pre-APAP, but neither treatment protected. This finding implicated an aldehyde oxidase (AO)-mediated metabolism of allopurinol, so mice were treated with hydralazine to inhibit AO prior to allopurinol/APAP administration, which eliminated the protective effects of allopurinol. We evaluated potential targets of AO-mediated preconditioning and found increased hepatic metallothionein 18h post-allopurinol. These data show metabolism of allopurinol occurring independent of P450 isoenzymes preconditions the liver and renders the animal less susceptible to an APAP overdose.
authors.affiliation: Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
authors.forename: C David
authors.initials: CD
authors.lastname: Williams
authors.affiliation: Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
authors.forename: Mitchell R
authors.initials: MR
authors.lastname: McGill
authors.affiliation: Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
authors.forename: Margitta
authors.initials: M
authors.lastname: Lebofsky
authors.affiliation: Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
authors.forename: Mary Lynn
authors.initials: ML
authors.lastname: Bajt
authors.affiliation: Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA. Electronic address: hjaeschke@kumc.edu.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Jaeschke
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives*; D042931:Aldehyde Oxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000493:Allopurinol / Q000494:pharmacology*; D000818:Animals; D056486:Chemical and Drug Induced Liver Injury / Q000188:drug therapy* / Q000473:pathology; D003545:Cysteine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives*; D062787:Drug Overdose; D005978:Glutathione / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008668:Metallothionein / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010117:Oxypurinol / Q000378:metabolism; D010766:Phosphorylation; D014969:Xanthine Oxidase / Q000378:metabolism
chemical_list: D000082:Acetaminophen; D000493:Allopurinol; C069744:acetaminophen cysteine; D008668:Metallothionein; D014969:Xanthine Oxidase; D042931:Aldehyde Oxidase; D048031:JNK Mitogen-Activated Protein Kinases; D010117:Oxypurinol; D005978:Glutathione; D003545:Cysteine
keywords: Acetaminophen hepatotoxicity; Aldehyde oxidase; Allopurinol; Metallothionein; Oxypurinol; c-Jun-N-terminal kinase