1. ¹Dermatochemistry and Skin Allergy, Department of Chemistry, Göteborg University, Göteborg, Sweden
2. ²Department of Dermatology and Allergology, University Hospital RWTH Aachen, Aachen, Germany
3. ³Interdisciplinary Centre for Clinical Research (IZKF) BIOMAT, University Hospital RWTH Aachen, Aachen, Germany

Correspondence: Moa Andresen Bergström, Dermatochemistry and Skin Allergy, Department of Chemistry, Göteborg University, SE-412 96 Göteborg, Sweden. E-mail: moa.andresen@chem.gu.se

Received 5 May 2006; Revised 7 September 2006; Accepted 2 October 2006; Published online 23 November 2006.

Abstract

Allergic contact dermatitis is a complex syndrome representing immunological responses to cutaneous exposure to protein-reactive chemicals. Although many contact sensitizers directly can elicit this disorder, others (prohaptens) require activation. Knowledge regarding the activating mechanisms remains limited, but one possibility is metabolic activation by cytochrome P450 (CYP) enzymes in the skin. We have, after quantitative reverse transcriptase-PCR studies of the CYP content in 18 human skin samples, developed an enriched skin-like recombinant human (rh) CYP cocktail using CYP1A1, 1B1, 2B6, 2E1, and 3A5. To validate the rhCYP cocktail, a prohaptenic conjugated diene ((5R)-5-isopropenyl-2-methyl-1-methylene-2-cyclohexene) was investigated using: the skin-like rhCYP cocktail, a liver-like rhCYP cocktail, single rhCYP enzymes, liver microsomes, keratinocytes, and a dendritic cell (DC) assay. The diene was activated to sensitizing epoxides in all non-cell-based incubations including the skin-like rhCYP cocktail. An exocyclic epoxide metabolite ((7R)-7-isopropenyl-4-methyl-1-oxaspiro[2.5]oct-4-ene) was found to be mainly responsible for the allergenic activity of the diene. This epoxide also induced pronounced DC activation indicated by upregulation of IL-8. The skin-like rhCYP cocktail provides a simplified alternative to using skin tissue preparations in mechanistic studies of CYP-mediated skin metabolism of prohaptens and offers the future possibility of designing in vitro predictive assays for assessment of allergenic activity of prohaptens.