Pyrene-based materials for organic electronics.

Metabolic activation of polycyclic and heterocyclic aromatic hydrocarbons and DNA damage: a review.

A human cytochrome P-450 (P450) 1B1 cDNA was expressed in Saccharomyces cerevisiae , and the microsomes containing P450 1B1 were used to examine the selectivity of this enzyme in the activation of a variety of environmental carcinogens and mutagens in Salmonella typhimurium TA1535/pSK1002 or NM2009 tester strains, using the SOS response as an end point of DNA damage. We also determined and compared these activities of P450 1B1 with those catalyzed by recombinant human P450s 1A1 and 1A2, which were purified from membranes of Escherichia coli . The carcinogenic chemicals tested included 27 polycyclic aromatic hydrocarbons and their dihydrodiol derivatives, 17 heterocyclic and aryl amines and aminoazo dyes, three mycotoxins, two nitroaromatic hydrocarbons, N -nitrosodimethylamine, vinyl carbamate, and acrylonitrile. Among the three P450 enzymes examined here, P450 1B1 was found to have the highest catalytic activities for the activation of 11,12-dihydroxy-11,12-dihydrodibenzo[ a,l ]pyrene, 1,2-dihydroxy-1,2-dihydro-5-methylchrysene, (+)-7,8-dihydroxy-7,8-dihydrobenzo[ a ]pyrene, 11,12-dihydroxy-11,12-dihydrobenzo[ g ]chrysene, 3,4-dihydroxy-3,4-dihydrobenzo[ c ]phenanthrene, 3-amino-1,4-dimethyl-5 H -pyrido[4,3- b ]indole, 2-aminoanthracene, 3-methoxy-4-aminoazobenzene, and 2-nitropyrene. P450 1B1 also catalyzed the activation of 2-amino-3,5-dimethylimidazo[4,5- f ]quinoline, 2-amino-3,8-dimethylimidazo[4,5- f ]quinoxaline, 2-amino-3-methylimidazo[4,5- f ]quinoline, 2-aminofluorene, 6-aminochrysene and its 1,2-dihydrodiol, (-)-7,8-dihydroxy-7,8-dihydrobenzo[ a ]pyrene, 1,2-dihydroxy-1,2-dihydrochrysene, 1,2-dihydroxy-1,2-dihydro-5,6-dimethylchrysene, 2,3-dihydroxy-2,3-dihydrofluoranthene, 3,4-dihydroxy-3,4-dihydro-7,12-dimethylbenz[ a ]anthracene, and 6-nitrochrysene to appreciable extents. However, P450 1B1 did not produce genotoxic products from benzo[ a ]pyrene, trans -3,4-dihydroxy-3,4-dihydrobenzo[ a ]anthracene, trans -8,9-dihydroxy-8,9-dihydrobenzo[ a ]anthracene, 7,12-dimethylbenz[ a ]anthracene and its cis -5,6-dihydrodiol, 5-methylchrysene, 11,12-dihydroxy-11,12-dihydro-3-methylcholanthrene, 1,2-dihydroxy-1,2-dihydro-6-methylchrysene, benzo[ c ]phenanthrene, 2-amino-6-methyldipyrido[1,2- a :3′,2′- d ]imidazole, 2-acetylaminofluorene, benzidine, 2-naphthylamine, aflatoxin B 1 , aflatoxin G 1 , sterigmatocystin, N -nitrosodimethylamine, vinyl carbamate, or acrylonitrile in this assay system. P450 1B1 is expressed constitutively in extrahepatic organs, including fetal tissue samples, and is highly inducible in various organs by 2,3,7,8-tetrachlorodibenzo- p -dioxin and related compounds in experimental animal models. Thus, activation of procarcinogens by P450 1B1 may contribute to human tumors of extrahepatic origin.

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Activation of chemically diverse procarcinogens by human cytochrome P-450 1B1

Multistage carcinogenesis in mouse skin

The comet assay is a rapid, sensitive and inexpensive method for measuring DNA strand breaks. The comet assay has advantages over other DNA damage methods, such as sister chromatid exchange, alkali elution and micronucleus assay, because of its high sensitivity and that DNA strand breaks are determined in individual cells. This review describes a number of studies that used the comet assay to determine DNA strand breaks in aquatic animals exposed to genotoxicants both in vitro and in vivo, including assessment of DNA damage in aquatic animals collected from contaminated sites. One difficulty of using the comet assay in environmental work is that of comparing results from studies that used different methods, such as empirical scoring or comet tail lengths. There seems to be a consensus in more recent studies to use both the intensity of the tail and the length of the tail, i.e. DNA tail moment, percentage of DNA in the tail. The comet assay has been used to assess DNA repair and apoptosis in aquatic animals and modifications of the comet assay have allowed the detection of specific DNA lesions. There have been some recent studies to link DNA strand breaks in aquatic animals to effects on the immune system, reproduction, growth, and population dynamics. Further work is required before the comet assay can be used as a standard bio-indicator in aquatic environments, including standardization of methods (such as ASTM method E2186-02a) and measurements.

Use of the single cell gel electrophoresis/comet assay for detecting DNA damage in aquatic (marine and freshwater) animals.

Four 7,12-dimethylbenz[a]anthracene--deoxyribonucleoside adducts formed in mouse epidermis in vivo arise from the syn dihydrodiol epoxide metabolite of this carcinogen. With the synthetic syn dihydrodiol epoxide it was possible to identify three of these as deoxyadenosine adducts and to establish their structures. These three adducts account for the large majority of DNA adduct arising from this metabolite in vivo. The in vivo metabolite is unusual, therefore, in that it reacts almost exclusively with adenine residues in DNA while most carcinogen metabolites react preferentially with guanine residues.

A metabolite of the carcinogen 7,12-dimethylbenz[ a ]anthracene that reacts predominantly with adenine residues in DNA

The metabolic activation of the carcinogens benzo[a]pyrene (BP) and 7,12-dimethylbenz[a]anthracene (DMBA) was examined in cell lines derived from bluegill fry (BF-2), rainbow trout (RTG-2) and brown bullhead (BB). All three cell lines metabolized BP (0.5 microgram/ml medium) almost completely to water-soluble metabolites within 120 h, but the maximum amount of BP bound to DNA ranged from only 5 pmol/mg DNA in the BF-2 cells to 17 in the BB cells and 44 in the RTG-2 cells. The major BP-DNA adduct in the BB and BF-2 cells was that formed by reaction of (+)-anti-BP-7,8-diol-9,10 epoxide [(+)anti-BPDE] with deoxyguanosine. This adduct was also present in the RTG-2 cell DNA, but there were larger amounts of unidentified polar BP-DNA adducts. Exposure of the cells to [3H]BP-7,8-diol, a metabolic precursor of (+)anti-BPDE, resulted in binding of 1.5, 12 and 35 pmol BP per mg DNA in the BF-2, BB and RTG-2 cells, respectively. More than 90% of the BP-7,8-diol added to the BF-2 cultures was recovered as a glucuronic acid conjugate, but the RTG-2 cells formed more glutathione conjugates than glucuronide conjugates. The BB cells formed both types of conjugates at a slower rate for more than 75% of the 7,8-diol was recovered unchanged after 24 h. The three cell lines differed in the proportion of a 0.1 microgram/ml dose of DMBA metabolized in 48 h: the values ranged from 47% in the BF-2 cells to 78% in the BB cells and 97% in the RTG-2 cells. The amount of DMBA bound to DNA ranged from 4.7 to 8.6 pmol/mg DNA in the three cell lines: DMBA-3,4-diol-1,2-epoxide (DMBADE) adducts were present in the BB cell DNA, but no significant amounts of DMBADE-DNA adducts were detected in the RTG-2 or BF-2 cell DNA. These results demonstrate that fish cell cultures can activate BP to an ultimate carcinogenic metabolite, (+)anti-BPDE, but the level of binding of this metabolite to DNA is much lower than that which occurs in rodent embryo cell cultures. In BF-2 cell cultures formation of BP-7,8-diol-glucuronide effectively prevents the activation of this diol to (+)anti-BPDE. A substantial proportion of the BP-7,8-diol is also metabolized to glucuronide and glutathione conjugates in BB and RTG-2 cells. DMBA also binds to DNA at very low levels in these fish cell cultures. Thus effective conjugation of diols and their metabolites by fish cell lines appears to greatly reduce metabolic activation of hydrocarbons through the bay-region diol epoxide pathway that predominates in mammalian cell cultures.

Metabolism and DNA adduct formation of benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene in fish cell lines in culture.

Syntheses of polycyclic aromatic hydrocarbon-nucleoslde and oligonucleotide adducts specifically alkylated on the amino functions of deoxyguanosine and deoxyadenosine

Benzo[c]phenanthrene diol epoxide can covalently bind to the exocyclic amino group of deoxyadenosine to generate [BPh]dA adducts where the polycyclic aromatic hydrocarbon is attached to the major groove edge of DNA. This paper reports on NMR-energy minimization structural studies of the (+)-trans-anti-[BPh]dA adduct positioned opposite dT in the sequence context d(C5-[BPh]A6-C7).d-(G16-T17-G18) at the 11-mer duplex level. The exchangeable and nonexchangeable protons of the benzo[c]phenanthrenyl moiety and the nucleic acid were assigned following analysis of two-dimensional NMR data sets in H2O and D2O solution. The solution structure of the (+)-trans-anti-[BPh]dA.dT 11-mer duplex has been determined by incorporating intramolecular and intermolecular proton-proton distances defined by upper and lower bounds deduced from NOESY data sets as restraints in energy minimization computations. The covalently attached benzo[c]phenanthrene ring intercalates to the 5'-side of the [BPh]-dA6 lesion site without disruption of the flanking Watson-Crick dC5.dG18 and [BPh]dA6.dT17 base pairs. The observed buckling of the intercalation cavity reflects the selective overlap of the intercalated phenanthrenyl ring with dT17 and dG18 bases on the unmodified strand. The structure provides new insights into how a polycyclic aromatic hydrocarbon covalently attached to the major groove edge of deoxyadenosine can still unidirectionally intercalate into the helix without disruption of the modified base pair. Our study establishes that among the contributing factors are a propeller-twisted [BPh]dA6.dT17 base pair, displacement of the carcinogen-DNA linkage bond from the plane of the dA6 base, the specific pucker adopted by the benzylic ring, and the propeller-like nonplanar geometry for the aromatic phenanthrenyl ring system. Our combined experimental-computational studies to date have now identified three structural motifs adopted by covalent polycyclic aromatic hydrocarbon-DNA adducts with their distribution determined by the chiral characteristics of individual stereoisomers and by whether the covalent adducts are generated at the minor or the major groove edge of the helix.

Solution Conformation of the (+)-trans-anti-[BPh]dA Adduct opposite dT in a DNA Duplex: Intercalation of the Covalently Attached Benzo[c]phenanthrene to the 5′-Side of the Adduct Site without Disruption of the Modified Base Pair

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in acetic acid, a convenient new reagent for the synthesis of aryl ketones and aldehydes via benzylic oxidation

Hongmee Lee

Papers

A metabolite of the carcinogen 7,12-dimethylbenz[ a ]anthracene that reacts predominantly with adenine residues in DNA

Metabolism and DNA adduct formation of benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene in fish cell lines in culture.

Syntheses of polycyclic aromatic hydrocarbon-nucleoslde and oligonucleotide adducts specifically alkylated on the amino functions of deoxyguanosine and deoxyadenosine

Solution Conformation of the (+)-trans-anti-[BPh]dA Adduct opposite dT in a DNA Duplex: Intercalation of the Covalently Attached Benzo[c]phenanthrene to the 5′-Side of the Adduct Site without Disruption of the Modified Base Pair

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in acetic acid, a convenient new reagent for the synthesis of aryl ketones and aldehydes via benzylic oxidation