title: Metabolic activation of the antibacterial agent triclocarban by cytochrome P450 1A1 yielding glutathione adducts.
abstract: Triclocarban (3,4,4'-trichlorocarbanilide; TCC) is an antibacterial agent used in personal care products such as bar soaps. Small amounts of chemical are absorbed through the epidermis. Recent studies show that residues of reactive TCC metabolites are bound covalently to proteins in incubations with keratinocytes, raising concerns about the potential toxicity of this antimicrobial agent. To obtain additional information on metabolic activation of TCC, this study characterized the reactive metabolites trapped as glutathione conjugates. Incubations were carried out with (14)C-labeled TCC, recombinant CYP1A1 or CYP1B1, coexpressed with cytochrome P450 reductase, glutathione-S-transferases (GSH), and an NADPH-generating system. Incubations containing CYP1A1, but not 1B1, led to formation of a single TCC-GSH adduct with a conversion rate of 1% of parent compound in 2 hours. Using high-resolution mass spectrometry and diagnostic fragmentation, the adduct was tentatively identified as 3,4-dichloro-3'-glutathionyl-4'-hydroxycarbanilide. These findings support the hypothesis that TCC is activated by oxidative dehalogenation and oxidation to a quinone imine. Incubations of TCDD-induced keratinocytes with (14)C-TCC yielded a minor radioactive peak coeluting with TCC-GSH. Thus, we conclude that covalent protein modification by TCC in TCDD-induced human keratinocyte incubations is mainly caused by activation of TCC by CYP1A1 via a dehalogenated TCC derivative as reactive species.
authors.affiliation: Institute of Food Toxicology and Chemical Analysis, University of Veterinary Medicine, Hanover Germany (N.H.S.); Department of Molecular Biosciences, School of Veterinary Medicine (J.B.M., D.M., A.R.B.), and Department of Entomology and Comprehensive Cancer Center (B.D.H.), and Environmental Toxicology, College of Agricultural and Environmental Sciences (R.H.R.), University of California, Davis, California schebb@wwu.de.
authors.forename: Nils Helge
authors.initials: NH
authors.lastname: Schebb
authors.affiliation: Institute of Food Toxicology and Chemical Analysis, University of Veterinary Medicine, Hanover Germany (N.H.S.); Department of Molecular Biosciences, School of Veterinary Medicine (J.B.M., D.M., A.R.B.), and Department of Entomology and Comprehensive Cancer Center (B.D.H.), and Environmental Toxicology, College of Agricultural and Environmental Sciences (R.H.R.), University of California, Davis, California.
authors.forename: Jaya B
authors.initials: JB
authors.lastname: Muvvala
authors.affiliation: Institute of Food Toxicology and Chemical Analysis, University of Veterinary Medicine, Hanover Germany (N.H.S.); Department of Molecular Biosciences, School of Veterinary Medicine (J.B.M., D.M., A.R.B.), and Department of Entomology and Comprehensive Cancer Center (B.D.H.), and Environmental Toxicology, College of Agricultural and Environmental Sciences (R.H.R.), University of California, Davis, California.
authors.forename: Dexter
authors.initials: D
authors.lastname: Morin
authors.affiliation: Institute of Food Toxicology and Chemical Analysis, University of Veterinary Medicine, Hanover Germany (N.H.S.); Department of Molecular Biosciences, School of Veterinary Medicine (J.B.M., D.M., A.R.B.), and Department of Entomology and Comprehensive Cancer Center (B.D.H.), and Environmental Toxicology, College of Agricultural and Environmental Sciences (R.H.R.), University of California, Davis, California.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Buckpitt
authors.affiliation: Institute of Food Toxicology and Chemical Analysis, University of Veterinary Medicine, Hanover Germany (N.H.S.); Department of Molecular Biosciences, School of Veterinary Medicine (J.B.M., D.M., A.R.B.), and Department of Entomology and Comprehensive Cancer Center (B.D.H.), and Environmental Toxicology, College of Agricultural and Environmental Sciences (R.H.R.), University of California, Davis, California.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Hammock
authors.affiliation: Institute of Food Toxicology and Chemical Analysis, University of Veterinary Medicine, Hanover Germany (N.H.S.); Department of Molecular Biosciences, School of Veterinary Medicine (J.B.M., D.M., A.R.B.), and Department of Entomology and Comprehensive Cancer Center (B.D.H.), and Environmental Toxicology, College of Agricultural and Environmental Sciences (R.H.R.), University of California, Davis, California.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Rice
mesh_terms: D065767:Activation, Metabolic; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D002224:Carbanilides / Q000493:pharmacokinetics*; D002461:Cell Line, Transformed; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans
chemical_list: D000900:Anti-Bacterial Agents; D002224:Carbanilides; C009540:triclocarban; D019363:Cytochrome P-450 CYP1A1; D005978:Glutathione
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