Identification and quantitation of benzo[a]pyrene-DNA adducts formed in mouse skin

Abstract

The DNA adducts of benzo[a]pyrene (BP) formed in vitro were previously identified and quantitated. In this paper, we report the identification and quantitation of the depurination adducts of BP, 8-(benzo[a]pyren-6-yl)guanine (BP-6-C8Gua), BP-6-N7Gua, and BP-6-N7Ade, formed in mouse skin by one-electron oxidation, as well as the major stable adduct formed via the diolepoxide pathway, BP diolepoxide bound at C-10 to the 2-amino of dG (BPDE-10-N2dG). Identification of the depurination adducts was achieved by HPLC and fluorescence line narrowing spectroscopy. The depurination adducts, BP-6-C8Gua (34%), BP-6-N7Gua (10%), and BP-6-N7Ade (30%), constituted 74% of the adducts found in mouse skin 4 h after treatment with BP. The stable adduct BPDE-10-N2dG accounted for 22% of the adducts. Treatment of the skin with BP-7,8-dihydrodiol or BP diolepoxide yielded almost exclusively the stable adduct BPDE-10-N2dG. When BP or BP-7,8-dihydrodiol was bound to RNA or denatured DNA in reactions catalyzed by rat liver microsomes, no depurination adducts were detected. The profiles of stable adducts were similar both qualitatively and quantitatively with native or denatured DNA. With activation of BP by horseradish peroxidase, the profiles of stable adducts differed with native and denatured DNA. The total amount of adducts with denatured DNA was only 25% of the amount detected with native DNA. No depurination adducts were detected with denatured DNA or RNA in the peroxidase system.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of polycyclic aromatic hydrocarbon–DNA adducts in inducing mutations in mouse skin

“…BPDE forms predominantly stable DNA adducts [22,86] and it formed the most number of tumors when early S-phase liver cells were exposed [48]. This result is consistent with studies suggesting that NER of the BPDEinduced stable adducts is error-free [45,54], and that mutations are induced in the proliferating cells by errors in translesion synthesis.…”

“…Taken together, it appears that the PAH or their metabolites that form predominantly depurinating adducts may form preneoplastic mutations by error-prone repair in quiescent cells, whereas the PAH that form mainly stable adducts would induce mutations by errors in translesion synthesis in proliferating cells. PAH such as BP, which forms significant amounts of both types of adducts [22,86], appear to induce mutations from both stable and depurinating adducts. For example, the relative proportions of BP-induced depurinating adducts show a strong correlation with the relative abundance of Adeor Gua-specific oncogenic H-ras mutations in skin tumors [16].…”

Environmental Carcinogenic Polycyclic Aromatic Hydrocarbons: Photochemistry and Phototoxicity

“…Metabolism of PAHs through one electron oxidation resulting in reactive free radical intermediates that can react with DNA to form DNA covalent adducts has also been reported (28)(29)(30)(31)(32) (Figure 2). Due to differences in mechanisms of metabolic activation, the ultimate carcinogenic metabolites or intermediates as well as the types of DNA adducts formed from the diolepoxide formation or from the free radical generation are different.…”

Prostate cancer risk from occupational exposure to polycyclic aromatic hydrocarbons interacting with the GSTP1 Ile105Val polymorphism

“…PAH are ubiquitous environmental contaminants that result from incomplete combustion processes and are known carcinogens [8]. PAH are thought to exert their carcinogenic properties through their ability to form PAH-DNA adducts [9][10][11]. Both casecontrol [12] and cohort [13] studies have found that most jobs associated with occupational PAH exposure have the potential for prostate cancer.…”