title: Acetaminophen-induced inhibition of Fas receptor-mediated liver cell apoptosis: mitochondrial dysfunction versus glutathione depletion.
abstract: We reported previously that acetaminophen overdose interrupts the signaling pathway of Fas receptor-mediated apoptosis. The aim of our study was to investigate the mechanism of this effect. Male C3Heb/FeJ mice received a single dose of acetaminophen (300 mg/kg ip) and/or anti-Fas antibody Jo-2 (0.6 mg/kg iv). Some animals were treated with allopurinol (100 mg/kg po) 18 and 1 h before acetaminophen injection. After 90 min of Jo treatment, there was processing of procaspase-3 and a significant increase in liver caspase-3 activity, which is consistent with apoptotic cell death. Treatment with acetaminophen 2.5 h before Jo inhibited the increase in hepatic caspase-3 activity by preventing the processing of the proenzyme. When administered alone, acetaminophen did not induce caspase-3 activation but caused significant liver injury. Acetaminophen treatment alone caused mitochondrial cytochrome c release, depletion of the hepatic ATP content by 55%, and a 10-fold increase in mitochondrial glutathione disulfide levels. Pretreatment with allopurinol prevented the mitochondrial oxidant stress and liver injury due to acetaminophen toxicity but had no effect on Jo-mediated apoptosis. Allopurinol did not affect the initial glutathione depletion after acetaminophen. However, allopurinol restored the sensitivity of hepatocytes to Fas receptor signaling in acetaminophen-treated animals. Histochemical evaluation of DNA fragmentation with the TUNEL assay showed that acetaminophen eliminated Fas receptor-mediated apoptosis in all hepatocytes not just in the damaged cells of the centrilobular area. Our data suggest that acetaminophen-induced mitochondrial dysfunction and not the initial glutathione depletion is responsible for the interruption of Fas receptor-mediated apoptotic signaling in hepatocytes.
authors.affiliation: Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
authors.forename: Tamara R
authors.initials: TR
authors.lastname: Knight
authors.forename: Hartmut
authors.initials: H
authors.lastname: Jaeschke
mesh_terms: D000082:Acetaminophen / Q000633:toxicity*; D000493:Allopurinol / Q000494:pharmacology; D000818:Animals; D000974:Antibodies, Antinuclear / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004359:Drug Therapy, Combination; D005978:Glutathione / Q000172:deficiency / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D020287:In Situ Nick-End Labeling; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism*
chemical_list: D000974:Antibodies, Antinuclear; D019014:fas Receptor; D000082:Acetaminophen; D000493:Allopurinol; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione