Received for publication April 7, 2006.
Revised June 30, 2006.
Accepted for publication July 3, 2006.

Enzyme-mediated protein haptenation of dapsone and sulfamethoxaozle in human keratinocytes - 1. Expression and role of cytochromes P450

Abstract

Cutaneous drug reactions (CDR) are among the most common adverse drug reactions and are responsible for numerous minor to life-threatening complications. Several arylamine drugs, such as sulfamethoxazole (SMX) and dapsone (DDS), undergo bioactivation resulting in adduction to cellular proteins. These adducted proteins may initiate the immune response that ultimately results in a CDR. Recent studies have demonstrated that normal human epidermal keratinocytes (NHEK) can bioactivate these drugs, resulting in protein haptenation. We sought to identify the enzyme(s) responsible for this bioactivation in NHEK. Using immunofluorescence confocal microscopy and an adduct-specific ELISA assay, we found that N-acetylation of the primary amine of SMX and DDS markedly reduced the level of protein haptenation in NHEK. Detection of mRNA and/or protein confirmed the presence of CYP3A4, CYP3A5 and CYP2E1 in NHEK. In contrast, neither CYP2C9 message nor protein was detectable. We also examined the ability of chemical inhibitors of cytochromes P450 (aminobenzotriazole and 1-dichloroethylene) and cyclooxygenase (indomethacin) to reduce protein haptenation when NHEK were incubated with SMX or DDS by either confocal microscopy or ELISA. These inhibitors did not significantly attenuate protein adduction with either SMX or DDS, indicating that cytochromes P450 and cyclooxygenase do not play important roles in the bioactivation of these xenobiotics in NHEK and thus suggesting the importance of other enzymes in these cells.

Key words: cytochromes P450, dapsone, keratinocytes, metabolism, protein haptenation, sulfamethoxazole

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