Identification of the major adducts formed by reaction of benzo(a)pyrene diol epoxide with DNA in vitro.

Straub, Kenneth; Meehan, Thomas; Burlingame, Alma L.; Calvin, Melvin

doi:10.1073/pnas.74.12.5285

Cited by 126 publications

(75 citation statements)

References 23 publications

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“…3). These diol epoxides can also bind to the N-7 of guanine (34), adenine (35)(36)(37)(38) and cytidine (38) and to phosphate residues (39,40). It should be mentioned that other metabolites of BP can also bind to DNA, especially under in vitro conditions; however, in target tissues for BP-induced neoplasia, BPDEI and BPDEII are the predominantly characterized adducts (41).…”

Section: Introductionmentioning

confidence: 99%

Formation and Persistence of Benzo(a)pyrene Metabolite-DNA Adducts

Stowers¹,

Anderson²

1985

Environmental Health Perspectives

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Benzo(a)pyrene (BP) and other polycyclic aromatic hydrocarbons (PAH) are ubiquitous environmental pollutants and are suspected to be carcinogenic in man. The in vivo formation of BP metabolite-DNA adducts has been characterized in a variety of target and nontarget tissues of mice and rabbits. Tissues included were lung, liver, forestomach, colon, kidney, muscle, and brain. The major adduct identified in each tissue was the (+ )-7,B,8a-dihydroxy-9a,lOa-epoxy-7,8,9,10-tetrahydro-BP (BPDEI)-deoxyguanosine adduct. A 713,8a-dihydroxy-93,1013-epoxy-7,8,9,10-tetrahydro-BP (BPDEII)-deoxyguanosine adduct, a ( -)-BPDEI-deoxyguanosine adduct, and an unidentified adduct were also observed. The adduct levels are unexpectedly similar in all the tissues examined from the same BP-treated animal. For example, the BPDEI-DNA adduct levels in muscle and brain of mice were approximately 50%o of those in lung and liver at each oral BP dose used. We have also examined adduct levels formed in vivo in several cell types of lung and liver. Macrophages, type II cells, and Clara cells from lung and hepatocytes and nonpparenchymal cells from liver were isolated from BP-treated rabbits. BPDEI-deoxyguanosine adduct was observed in each cell type and, moreover, the levels were similar in various cell types. These and previous results strongly suggest that DNA in many human tissues is continuously damaged from known exposure of humans to BP and other PAH. Moreover, DNA adducts formed from BP are persistent in lung and brain. The persistence of adducts in cell types that have slow turnover rates could result in significant accumulation of adducts from long-term exposure to low levels of BP. BPDEI-DNA adducts and other bulky adducts are known to inhibit replication and transcription in in vitro systems. Even if environmental exposure to PAH is too low to induce neoplasia, the accumulation of DNA adducts may produce aberrations in transcripts of genetic information in various cells and lead to other toxic effects. Thus, further elucidation of the mechanism by which BP(PAH) metabolites bind to DNA of specific cell types and of the cellselective repair of the adducts should enhance our understanding of the potential health risk from exposure to this class of environmental pollutants.

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Section: Introductionmentioning

confidence: 99%

Formation and Persistence of Benzo(a)pyrene Metabolite-DNA Adducts

Stowers¹,

Anderson²

1985

Environmental Health Perspectives

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“…The most mutagenic and carcinogenic of these diastereomers is 7R,8S-dihydroxy-9S, 10R-epoxy-7,8,9,10-tetrahydrobenzo[alpy-rene [(+)-anti-BPDE] (7-9). The primary alkylation site of the diol epoxides in DNA is the N2 position of deoxyguanosine (N2-dGuo) (5)(6)(7)(10)(11)(12), and the principal adduct formed at this site in vivo is due to (+)-anti-BPDE (4). The purine is attached to the C-10 position of the hydrocarbon and is trans to the C-9 hydroxy substituent of the benzo[a]pyrene moiety (a trans adduct).…”

Section: Introductionmentioning

confidence: 99%

“…Adduct quantitation was based on a summation of the disintegrations per minute (dpm) in a peak. Adducts were identified from their chromatographic and spectroscopic properties on the basis of previous work in this (11,14,26) and other laboratories (12,15). Adduct samples stored for more than a few weeks were kept at -800C.…”

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confidence: 99%

Chloride ions catalyze the formation of cis adducts inthe binding of anti-benzo[a]pyrene diol epoxide to nucleicacids.

Wolfe

Yamamoto

Meehan

1994

Proc. Natl. Acad. Sci. U.S.A.

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The alkylation of DNA by racemic 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[alpyrene (ant-BPDE) exhibits a strong preference for formation of trans adducts between the N2 deoxyguanosine alkylation site and the (+)-enantiomer of anli-BPDE. In the presence of 10 mM buffer with no added salt, 98% of the adducts formed with native calf thymus DNA result from trans opening ofthe epoxide ring. The strong selectivity for trans adduct formation obtained with duplex DNA at low salt concentration is found to a lesser degree with poly(G) but is nearly absent with dAMP. When DNA adducts are formed in 10 mM MgCl2 or 1 M NaCl, the proportion of cis adducts increases to %-7 and ""26%, respectively. At low salt, 10 mM MgCl2, and 1 M NaCl, deoxyguanosine adducts are approximately 1%, 6%, and 24% cis, whereas deoxyadenosine adducts are approximately 11%, 14%, and 37% cis, respectively. NaCI also increases the proportion of cis adducts formed with poly(G) and dAMP. It is proposed that the increase in cis-adduct formation due to salt results from SN1 attack of chloride ion on the BPDE carbocation, forming a trans chlorohydrin, followed by SN2 attack of DNA.Benzo [a]pyrene is a potent carcinogen and ubiquitous environmental pollutant which is metabolically activated to form several diastereomeric diol epoxide intermediates capable of alkylating DNA, RNA, and protein (1-7). The most mutagenic and carcinogenic of these diastereomers is 7R,8S-dihydroxy-9S, 10R-epoxy-7,8,9,10-tetrahydrobenzo[alpy-rene [(+)-anti-BPDE] (7-9). The primary alkylation site of the diol epoxides in DNA is the N2 position of deoxyguanosine (N2-dGuo) (5)(6)(7)(10)(11)(12), and the principal adduct formed at this site in vivo is due to (+)-anti-BPDE (4). The purine is attached to the C-10 position of the hydrocarbon and is trans to the C-9 hydroxy substituent of the benzo[a]pyrene moiety (a trans adduct). Although trans adducts predominate in DNA, those with the 9 and 10 substituents ofthe hydrocarbon moiety in the cis configuration (cis adducts) also occur (12-15). The interaction of anti-BPDE with DNA involves physical association and a DNA-catalyzed hydrolysis reaction that competes with the alkylation reaction. The mechanisms of these reactions have been reviewed (16,17), as have the characteristics of the covalent adducts (18).The conformations of the trans N2-dGuo adducts of (+)-anti-BPDE and 7S,8R-dihydroxy-9R, 8,9,pyrene [(-)-anti-BPDE] in DNA have recently been determined by NMR, and both adducts have been found to be situated in the minor groove, causing minimal distortion of the duplex (19,20). The hydrocarbon moieties of the two adducts point in opposite directions [toward the 5' end of the modified strand in the (+)-BPDE adduct, and toward the 3' end in the (-)-BPDE adduct]. The cis (+)-anti-BPDE N2-dGuo adduct has an intercalated conformation, leading to disruption of a base pair (21). The conformation of the cis (-)-anti-BPDE N2-dGuo adduct is believed, on the basis of less direct spectroscopic evidence, to be similar (22). A var...

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“…The primary alkylation site of (ϩ)-anti-BPDE is the exocyclic amino group of deoxyguanosine (3, 6-10). Minor adducts are formed by alkylation of the exocyclic amino group of deoxyadenosine (dAdo) and, to a lesser extent, that of deoxycytidine (9,11,12). In addition, BPDE forms an unstable adduct at the N-7 position of deoxyguanosine, which results in depurination (13).…”

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confidence: 99%

Benzo[ a ]pyrene diol epoxide-DNA cis adduct formation through a trans chlorohydrin intermediate

Meehan

Wolfe

Negrete

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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Alkylation of DNA by 7r,8t-dihydroxy,9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) forms mainly trans adducts (with respect to the C-9͞10 positions). We recently described a halide-catalyzed pathway that preferentially generates cis adducts and now report that the trans chlorohydrin of anti-BPDE (trans-BPDCH) is an intermediate in the chloride-catalyzed reaction. trans-BPDCH was synthesized, and both it and anti-BPDE were reacted with deoxyadenosine as a model DNA nucleophile. The stereochemistry and yields of deoxyadenosine adducts were determined as a function of chloride concentration. In the absence of salt, the fraction of cis adducts obtained from anti-BPDE and trans-BPDCH are 0.33 and 0.67, respectively. Adding sodium chloride increases the fraction of cis adducts (and consequently decreases the fraction of trans adducts), with the midpoint of the increase for both substrates at approximately 35-40 mM chloride. The chloride-dependent curves for BPDE and BP-DCH converge at 1 M chloride, where the fraction of cis adducts is 0.88. Chloride also increases the total yield of cis adducts with either substrate, whereas the yield of trans adducts from the chlorohydrin is not significantly changed. These results support a mechanism by which chloride ion undergoes nucleophilic addition to the benzylic C-10 position of anti-BPDE. This generates a trans halohydrin that alkylates DNA with inversion of configuration to form a cis adduct. This pathway may have biological significance because chlorohydrins could form in serum or in cells with relatively high intracellular concentrations of chloride.Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants, and a number of these hydrocarbons, including benzo[a]pyrene, are potent carcinogens. Benzo [a]pyrene is cytotoxic and mutagenic, and induces cell transformation in culture (1, 2). Although benzo [a]pyrene is a weak complete carcinogen, it is an initiator and interacts strongly with DNA, causing mutations and chromosomal damage (2).Benzo [a]pyrene is metabolically activated by a series of reactions to form several isomeric bay region diol epoxides (3). The most mutagenic and carcinogenic of these is (7R,8S)-dihydroxy-(9S,10R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(ϩ)-anti-BPDE]; this isomer is also the one formed in highest amounts in vivo (3-5). BPDE and other activated PAH carcinogens probably initiate tumors by alkylation of DNA. The primary alkylation site of (ϩ)-anti-BPDE is the exocyclic amino group of deoxyguanosine (3, 6-10). Minor adducts are formed by alkylation of the exocyclic amino group of deoxyadenosine (dAdo) and, to a lesser extent, that of deoxycytidine (9,11,12). In addition, BPDE forms an unstable adduct at the N-7 position of deoxyguanosine, which results in depurination (13). Another pathway of PAH activation is by metabolic conversion to radical cations (14), which alkylate DNA to form adducts that are also lost by depurination.The formation of adducts between bay region diol epoxides and DNA has be...

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Identification of the major adducts formed by reaction of benzo(a)pyrene diol epoxide with DNA in vitro.

Cited by 126 publications

References 23 publications

Formation and Persistence of Benzo(a)pyrene Metabolite-DNA Adducts

Formation and Persistence of Benzo(a)pyrene Metabolite-DNA Adducts

Chloride ions catalyze the formation of cis adducts inthe binding of anti-benzo[a]pyrene diol epoxide to nucleicacids.

Benzo[ a ]pyrene diol epoxide-DNA cis adduct formation through a trans chlorohydrin intermediate

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