Transport of DNA-adducting metabolites in mouse serum following benzo [a]pyrene administration

Abstract

Metabolic activation of benzo[a]pyrene (BaP) by cellular enzymes is required for DNA adduct formation. In vivo DNA adducts might also arise from BaP metabolites supplied via the systemic circulation, rather than from in situ activation. We determined whether electrophilic metabolites could be detected in mouse serum 4 h after BaP dosing (i.p.) by trapping metabolites with salmon sperm DNA (ssDNA), followed by 32P-postlabeling analysis for DNA adducts. In vitro studies demonstrated that mouse serum sequesters BaP-7,8-diol-9,10-epoxide (BPDE) and protects it from hydrolysis. BPDE was rapidly transferred from serum to ssDNA or splenocytes, with adduct levels in ssDNA 4- to 7-fold greater than in splenocytes. After BaP administration, mouse serum produced two adduct spots when incubated with ssDNA. The major adduct (spot 3) co-chromatographed with a BPDE adduct standard, while the minor adduct (spot 2) was unrelated to BPDE. A BPDE standard curve in control serum was developed to quantitate BPDE levels in dosed serum. These levels ranged from 13.1 to 19.1 nM. Tissue DNA contained three adduct spots: spots 2 and 3 appeared identical to the respective adducts arising from dosed serum. BPDE-DNA adducts in tissues were highest in liver, lung and spleen, with kidney and stomach levels significantly lower. Levels of adduct 2 did not correlate with levels of adduct 3, especially in spleen where the adduct 2/adduct 3 ratio was very low. In vitro studies in which splenocytes were presented with both adducting metabolites suggested that splenocytes preferentially form adduct 3. These results indicate that two of the three BaP electrophilic metabolites responsible for cellular DNA damage are present in mouse serum. The levels of BPDE in serum may be sufficient to account for a substantial portion of the tissue load of BPDE-DNA adducts.

Benzo(a)pyrene-albumin adducts in humans exposed to polycyclic aromatic hydrocarbons in an industrial area of Poland.

“…Air measurements of PAHs and benzo(a)pyrene presented in this study have previously been published by 0vreb0 et al (table 4). '7 The data have been used in this study for comparing the air concentrations of PAHs and benzo(a)pyrene with the concentrations of BPDEalbumin adducts of the occupationally exposed groups for the two seasons.…”

In vitro evaluation of baseline and induced DNA damage in human sperm exposed to benzo[a]pyrene or its metabolite benzo[a]pyrene-7,8-diol-9,10-epoxide, using the comet assay

“…In general, metabolic activation by endogenous enzymes is required for B[ a ]P to be genotoxic; in particular, the metabolite BPDE is known to interact with biomolecules such as proteins and DNA (34), with new reactive B[ a ]P metabolites still being discovered (35). In vivo , some B[ a ]P activation products probably have sufficient stability to be transported from cells or organs possessing the ability to metabolize B[ a ]P, to cells or tissues lacking such activity (36). We recently detected adducts in sperm from mice exposed to B[ a ]P in vivo , strongly suggesting that B[ a ]P activation products had diffused from metabolically competent surrounding tissues (37).…”

Ovarian Susceptibility to Benzo[a]Pyrene: Tissue Burden of Metabolites and DNA Adducts in F-344 Rats

“…Another objective of this study was to examine the relationship that may exist among bioavailable dose and kinetics of disposition of administered BaP in plasma and reproductive tissues. The rationale for undertaking this research is that tissue DNA acts as the internal trapping agent for reactive metabolites (Ginsberg & Atherholt, 1989; Garg et al, 1993) produced in liver and reproductive tissues postexposure. Since BaP toxicity to reproductive system is the prime focus of our research, studies on kinetics of disposition of reactive metabolites and DNA adducts will provide insight into the amount of ingested BaP reaching the target ovaries throughout the course of its residence in the body to elicit adverse effects.…”