title: Role of caspases in acetaminophen-induced liver injury.
abstract: The mode of cell death after acetaminophen (AAP) overdose is controversially discussed. A recent study reported a protective effect of the pancaspase inhibitor Z-VAD-fmk against AAP toxicity in vivo but the mechanism of protection remained unclear. Therefore, the objective of this investigation was to assess if Z-VAD-fmk or the low doses of dimethyl sulfoxide (DMSO) used as solvent were responsible for the protection. Treatment with 10 mg/kg Z-VAD-fmk or diluted DMSO (0.25 ml/kg) for 15 min before but not 2.5 h after AAP prevented the oxidant stress (hepatic glutathione disulfide content; nitrotyrosine staining), DNA fragmentation (anti-histone ELISA, TUNEL assay) and liver injury (plasma ALT activities) at 6 h after administration of 300 mg/kg AAP. Even a lower dose (0.1 ml/kg) of DMSO was partially effective. DMSO pretreatment also attenuated the initial decline in hepatic glutathione levels. On the other hand, 10 microM Z-VAD-fmk was unable to prevent AAP-induced cell death in primary cultured mouse hepatocytes. We conclude that Z-VAD-fmk does not protect against AAP-induced liver injury and, therefore, caspases are not involved in the mechanism of AAP-induced liver injury. In contrast, the protection in vivo is caused by the diluted DMSO, which is used to solubilize the inhibitor Z-VAD-fmk. The results emphasize that even very low doses of DMSO, which are generally necessary to dissolve water-insoluble inhibitors, can have a profound impact on the toxicity of drugs and chemicals when metabolic activation is a critical aspect of the mechanism of cell injury.
authors.affiliation: Liver Research Institute University of Arizona 1501 N. Campbell Ave, Room 6309 Tucson, AZ 85724, USA. jaeschke@email.arizona.edu
authors.forename: Hartmut
authors.initials: H
authors.lastname: Jaeschke
authors.forename: Cathleen
authors.initials: C
authors.lastname: Cover
authors.forename: Mary Lynn
authors.initials: ML
authors.lastname: Bajt
mesh_terms: D000082:Acetaminophen / Q000009:adverse effects*; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D018712:Analgesics, Non-Narcotic / Q000009:adverse effects*; D000818:Animals; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D056486:Chemical and Drug Induced Liver Injury; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008107:Liver Diseases / Q000201:enzymology / Q000517:prevention & control; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D012997:Solvents / Q000494:pharmacology
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D018712:Analgesics, Non-Narcotic; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D012997:Solvents; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D000082:Acetaminophen; D020169:Caspases; D004121:Dimethyl Sulfoxide