title: Markers of electrophilic stress caused by chemically reactive metabolites in human hepatocytes.
abstract: The metabolic activation of a drug to an electrophilic reactive metabolite and its covalent binding to cellular macromolecules is considered to be involved in the occurrence of idiosyncratic drug toxicity (IDT). As a cellular defense system against oxidative and electrophilic stress, phase II enzymes are known to be induced through a Kelch-like ECH-associated protein 1/nuclear factor E2-related factor 2/antioxidant response element system. We presumed that it is important for the risk assessment of drug-induced hepatotoxicity and IDTs to observe the biological responses evoked by exposure to reactive metabolites, and then investigated the mRNA induction profiles of phase II enzymes in human hepatocytes after exposure to problematic drugs associated with IDTs, such as ticlopidine, diclofenac, clozapine, and tienilic acid, as well as safe drugs such as levofloxacin and caffeine. According to the results, the problematic drugs exhibited inductive effects on heme oxygenase 1 (HO-1), which contrasted with the safe drugs; therefore, the induction of HO-1 mRNA seems to be correlated with the occurrence of drug toxicity, including IDT caused by electrophilic reactive metabolites. Moreover, glutathione-depletion and cytochrome P450 (P450)-inhibition experiments have shown that the observed HO-1 induction was triggered by the electrophilic reactive metabolites produced from the problematic drugs through P450-mediated metabolic bioactivation. Taken together with our present study, this suggests that HO-1 induction in human hepatocytes would be a good marker of the occurrence of metabolism-based drug-induced hepatotoxicity and IDT caused by the formation of electrophilic reactive metabolites.
authors.affiliation: Drug Metabolism Laboratory, Research and Development Division, Shinagawa Research and Development Center, Daiichi Sankyo Co., Ltd., 1-2-58, Hiromachi, Shinagawa-ku, Tokyo, 140-8710, Japan. takakusa.hideo.yb@daiichisankyo.co.jp
authors.forename: Hideo
authors.initials: H
authors.lastname: Takakusa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Masumoto
authors.forename: Ayako
authors.initials: A
authors.lastname: Mitsuru
authors.forename: Osamu
authors.initials: O
authors.lastname: Okazaki
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sudo
mesh_terms: D000082:Acetaminophen / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D002083:Butylated Hydroxyanisole / Q000494:pharmacology*; D002265:Carboxylic Ester Hydrolases / Q000235:genetics; D002478:Cells, Cultured; D003024:Clozapine / Q000494:pharmacology; D004008:Diclofenac / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D014453:Glucuronosyltransferase / Q000235:genetics; D051547:Heme Oxygenase-1 / Q000235:genetics*; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics; D051267:NF-E2-Related Factor 2 / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013988:Ticlopidine / Q000494:pharmacology; D013989:Ticrynafen / Q000494:pharmacology; D000099148:UGT1A1 Enzyme
chemical_list: D000082:Acetaminophen; D001241:Aspirin; D002083:Butylated Hydroxyanisole; D002265:Carboxylic Ester Hydrolases; D003024:Clozapine; D004008:Diclofenac; D005665:Furosemide; D014453:Glucuronosyltransferase; D051547:Heme Oxygenase-1; D007770:L-Lactate Dehydrogenase; D016660:NAD(P)H Dehydrogenase (Quinone); D051267:NF-E2-Related Factor 2; D012333:RNA, Messenger; D013988:Ticlopidine; D013989:Ticrynafen; D000099148:UGT1A1 Enzyme; C495635:NFE2L2 protein, human; C447479:NQO1 protein, human; C474609:CES1 protein, human