Trans- and cis-DNA adduct concentration in epidermis from mouse and rat skin treated ex vivo with benzo[a]pyrene diol epoxide and its corresponding chlorohydrin

Abstract

Benzo[a]pyrene diol epoxide, a metabolite of benzo[a]pyrene (BaP), and chlorohydrin, the reaction product of chloride and the epoxide, form in vitro the same trans- and cis-stereoisomeric DNA adducts, but in different proportions. In this study, we asked whether the DNA adduct concentration can be kept the same by applying the appropriate dose of (±)-7 r,8 t-dihydroxy-9 t,10 t-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene ( anti-BPDE)and (±)-7 r,8 t,9 t-trihydroxy-10 c-chloro-7,8,9,10-tetrahydrobenzo[a]pyrene ( trans-BPDCH) to rodent skin and whether the DNA adducts formed differ only in their trans- and cis-stereoisomerism. Skin from C57Bl6 mice, spontaneous hypertension rats (SHR) and Sprague-Dawley (SD) rats was treated ex vivo immediately after the death of the animals with anti-BPDE and its corresponding bay region chlorohydrin trans-BPDCH and the epidermis was analyzed for DNA adducts 1 h after the application. We found that adduct formation at the exocyclic amino groups of deoxyguanosine and deoxyadenosine in epidermal DNA followed a linear dose–response within 6–100 nmol/cm 2 with both chemicals. In order to achieve the same adduct concentration in mouse, spontaneous hypertension rat (SHR), and Sprague-Dawley (SD) rat skin, respectively, a 37-, 23- and 10-fold lower dose of anti-BPDE than of trans-BPDCH had to be applied. The order of 2′-deoxyguanosine (dGuo) adduct concentration with anti-BPDE was similar to what has been reported, but the order with trans-BPDCH was (+)- cis-BPDE-N 2-dGuo adduct>(+)- trans-BPDE-N 2-dGuo=(−)- trans-BPDE-N 2-dGuo>(−)- cis-BPDE-N 2-dGuo in mouse skin. Irrespective of species or strain, a significantly higher proportion of cis-adducts was obtained after treatment with trans-BPDCH than after treatment with anti-BPDE. Therefore, DNA adduct concentration can be kept the same by applying the appropriate dose of anti-BPDE and trans-BPDCH to rodent skin and the DNA adducts formed differ only in their trans- and cis-stereoisomerism.