title: Cutaneous metabolic activation of carvoxime, a self-activating, skin-sensitizing prohapten.
abstract: Bioactivation of low molecular weight compounds in the skin can cause contact sensitization. We have previously shown that the alpha, beta-R-unsaturated oxime R-carvoxime [1, (R)-2-methyl-5-isopropenylcyclohex-2-enone oxime] is bioactivated to two diastereomeric highly reactive and strongly sensitizing alpha, beta-epoxy oxime metabolites. To investigate if this metabolic activation is catalyzed by the major cytochrome P450 (P450) enzymes found in human skin, incubations of 1 with a skinlike P450 cocktail in the presence of glutathione were carried out. We identified three glutathione conjugates in the incubation mixture arising from two diasteomeric alpha, beta-epoxy oxime metabolites of 1, thus showing that the metabolic activation of 1 is P450-mediated. A P450 identification study using the individual P450 enzymes present in the skinlike P450 cocktail showed the involvement of P450 1A1 and 1B1 and also to some extent 2B6. P450 1B1 metabolism of 1 was found to be stereoselective as glutathione conjugates from only one of the alpha, beta-epoxyoxime metabolites were identified (metabolite 2). Additionally, 1 was found to be an inducer of P450 1B1 (but not 1A1) in human monocyte-derived dendritic cells (moDCs) and to some extent in normal human epidermal keratinocytes. A further transcriptional gene expression change observed in moDCs was a 44-fold upregulation of IL-8, a marker often used for assessment of sensitizing potential of contact allergens. The autoinduction of P450 1B1 by 1 may be a key event in the development of contact allergy to 1 and may also explain why only metabolite 2, and not 3, was found to elicit an allergic response in mice sensitized to 1. Our data show that the alpha, beta-unsaturated oxime 1 is bioactivated by human cutaneous P450, thus forming highly allergenic metabolites, and has the potential to induce its own bioactivation pathway, particularly in antigen-presenting cells.
authors.affiliation: Department of Dermatology and Allergology and Interdisciplinary Centre for Clinical Research (IZKF), BIOMAT, RWTH Aachen University, D-52074 Aachen, Germany. hagen.ott@post.rwth-aachen.de
authors.forename: Hagen
authors.initials: H
authors.lastname: Ott
authors.forename: Moa Andresen
authors.initials: MA
authors.lastname: Bergström
authors.forename: Ruth
authors.initials: R
authors.lastname: Heise
authors.forename: Claudia
authors.initials: C
authors.lastname: Skazik
authors.forename: Gabriele
authors.initials: G
authors.lastname: Zwadlo-Klarwasser
authors.forename: Hans F
authors.initials: HF
authors.lastname: Merk
authors.forename: Jens M
authors.initials: JM
authors.lastname: Baron
authors.forename: Ann-Therese
authors.initials: AT
authors.lastname: Karlberg
mesh_terms: D000818:Animals; D002460:Cell Line; D002853:Chromatography, Liquid; D003512:Cyclohexanones / Q000737:chemistry* / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003713:Dendritic Cells / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D006241:Haptens / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D020382:Interleukin-18 / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects; D013058:Mass Spectrometry; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D010091:Oximes / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D012867:Skin / Q000201:enzymology*
chemical_list: C540395:2-methyl-5-isopropenylcyclohex-2-enone oxime; D003512:Cyclohexanones; D006241:Haptens; D020382:Interleukin-18; D010091:Oximes; D003577:Cytochrome P-450 Enzyme System; D005978:Glutathione