0000000000013416
AUTHOR
Andreas Luch
DNA Modification Induced After Metabolic Activation of the Potent Carcinogen Dibenzo[a, l]pyrene in V79 Chinese Hamster Cells Stably Expressing Single Cytochromes P450
Abstract The polycyclic aromatic hydrocarbon (PAH) dibenzo[a, l]pyrene (DB[a, l]P) has been found to be an environmental pollutant and, considering the available data from rodent bioassays, it represents the most carcinogenic member compound of the class of PAH yet discovered. To sort out the contribution of individual cytochromes P450 (P450) in the metabolic activation of this PAH, V79 cells stably expressing a single P450 isoform were treated with DB[a, l]P or enantiomeric DB[a, l]P-11,12-dihydrodiols (diols). Subsequent analysis of the DNA adducts formed revealed substantial differences in the adduct pattern and the total DNA binding depending on the cell line used. Human P450 1B1 effect…
Stereoselective Metabolic Activation of Dibenzo[a,l]Pyrene in the Human Mammary Carcinoma Cell Line MCF-7 Results in Formation of (-)-antiand (+)-syn-11,12-Diol-13,14-Epoxidedeoxyadenosine Adducts in DNA
Abstract Dibenzo[a,l]pyrene (DB[a,l]P) is an important polycyclic aromatic hydrocarbon because of possible human exposure and its exceptionally high carcinogenicity in rodents. We examined the metabolism of DB[a,l]P and the formation of DB[a,l]P-DNA adducts in the human mammary carcinoma cell line (MCF-7). Analysis of the DNA adducts by 33P-postlabeling, immobilized boronate chromatography, HPLC and TLC demonstrated that DB[a,l]P is stereoselectively metabolized to specific optical isomers of DB[a,l]P-11,12-diol-13,14-epoxide (DB[a,l]PDE). The major anti-DB[a,l]PDE adduct formed in DB[a,l]P-treated MCF-7 cells resulted from reaction of (-)-anti-DB[a,l]PDE with DNA whereas the two major syn-…
Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles
The advancement of analytical methods for nanoparticle measurements is critical both for the growing industrial exploitation of engineered nanoparticles and for developing robust strategies to understand and control the concentration of nanomaterials in humans and the environment. For high value nanoparticles, the measurement of nanoparticle number concentration in a liquid directly impacts the ability to assess the scale and reproducibility of the production process, it allows optimisation of efficiency and supports regulatory compliance. This measurement is also useful to monitor and control the intentional or accidental release of engineered nanoparticles into the environment at the produc…
Metabolic activation of dibenzo[a,l]pyrene by human cytochrome P450 1A1 and P450 1B1 expressed in V79 Chinese hamster cells.
Metabolic activation of the strongly carcinogenic polycyclic aromatic hydrocarbon (PAH) dibenzo[a,l]pyrene (DB[a,l]P) and its trans-8,9-dihydrodiol (trans-8,9-diol) catalyzed by human cytochromes P450 (P450) 1A1 and 1B1 was investigated. DNA binding of DB[a,l]P in mammalian cell lines has previously been shown to be preferentially mediated by fjord region DB[a,l]P-11,12-dihydrodiol 13,14-epoxides (DB[a,l]PDE). In order to elucidate different capabilities of both P450 enzymes for metabolic activation of DB[a, l]P V79 Chinese hamster cells, stably expressing human P450s 1A1 or 1B1 have been exposed to the parent PAH or its racemic trans-8, 9-diol. For this purpose, synthesis and spectroscopic…
Tumor formation in the neonatal mouse bioassay indicates that the potent carcinogen dibenzo[def,p]chrysene (dibenzo[a,l]pyrene) is activated in vivo via its trans-11,12-dihydrodiol.
The hexacyclic aromatic hydrocarbon dibenzo[def,p]chrysene, better known as dibenzo[a,l]pyrene (DBP) in the field of chemical carcinogenesis, is present in the environment as a combustion product of organic matter. This compound is probably the strongest chemical carcinogen ever tested. As ultimate genotoxic metabolites of DBP two electrophilically reactive species are discussed: (i) radical cations generated by one-electron oxidation, and (ii) fjord region dihydrodiol epoxides formed via the trans-11,12-dihydroxy 11,12-dihydro derivative of DBP (11,12-dihydrodiol). In order to delineate the metabolic pathway(s) involved in tumor formation by DBP, newborn Crl:CD-1(ICR)BR mice were intraperi…
Molecular studies on the toxifying effects by genetically engineered cytochromes P450.
After almost two decades, it is now evident that methodology based on molecular biology and gene technology has dramatically changed the way basic and applied toxicology is being performed. It star...
Synthesis and mutagenicity of the diastereomeric fjord-region 11,12-dihydrodiol 13,14-epoxides of dibenzo[a,l]pyrene.
Extensive tumorigenicity studies in rodents revealed that dibenzo[a,l]pyrene (DB[a,l]P) is the most potent carcinogen among all polycyclic aromatic hydrocarbons (PAHs) tested so far. The structure of the genotoxic metabolite(s) responsible for this exceptional carcinogenicity is unknown. The fjord-region syn- and anti-DB[a,l]P-11,12-dihydrodiol 13,14-epoxides (syn- and anti-DB[a,l]PDE) were synthesized to clarify their role as possible ultimate mutagenic and carcinogenic metabolites of DB[a,l]P.9-Formyl-11,12-dimethoxybenzo[g] chrysene was prepared from 9-phenanthrylacetic acid by a photochemical route. After reaction of the aldehyde with trimethylsulfonium iodide to generate an oxiranyl si…
Tumor-initiating activity of the (+)-(S,S)- and (−)-(R,R)-enantiomers of trans-11,12-dihydroxy-11,12-dihydrodibenzo[a,l]pyrene in mouse skin
Abstract A single administration of enantiomerically pure 11,12-dihydrodiols of dibenzo[ a,l ]pyrene (DB[ a,l ]P) on the back of NMRI mice and subsequent chronic treatment with 12- O -tetradecanoylphorbol 13-acetate (TPA) (initiation/promotion assay) revealed strikingly different carcinogenic activities of both enantiomers. Tumor-initiating activity of (−)-(11 R ,12 R )-DB[ a,l ]P-dihydrodiol, which is the metabolic precursor of the (−)- anti -(11 R ,12 S )-dihydrodiol (13 S ,14 R )-epoxide, was exceptionally higher than the corresponding effect of (+)-(11 S ,12 S )-DB[ a,l ]P-dihydrodiol, the metabolic precursor of (+)- syn -(11 S ,12 R )-dihydrodiol (13 S ,14 R )-epoxide. After topical ap…
Species-dependent Metabolism of Benzo[c]phenanthrene and Dibenzo[a, l]pyrene by Various CYP450 Isoforms
Abstract The metabolism of benzo[c]phenanthrene (B[c]Ph) and dibenzo[a, l]-pyrene (DB[a, l]P) with various CYP isoforms including rat 1A1, 1A2, 2B1, 2E1, human 1A1, 1A2, 1B1, 2A6, 3A4, 2E1 and fish 1A expressed in Chinese hamster V79 cells has been compared. Major differences in the catalytic activities and in the regioselectivity of the eleven CYP isoforms with B[c]Ph and DB[a, l]P as substrates have been observed. There have been found substantially species-specific differences between homologous CYP isoforms at least when human, rat and fish are compared, which have to be taken into account when animal experiments are extrapolated to human. In particular, complementary catalytic activiti…
Synthesis of fjord region tetraols and their use in hepatic biotransformation studies of dihydrodiols of benzo[c]chrysene, benzo[g]chrysene and dibenzo[a,l]pyrene
Metabolic activation of the racemic benzo[c]chrysene-trans-9,10-, benzo[g]chrysene-trans-11,12- and dibenzo[a,l]pyrene-trans-11,12-dihydrodiols to fjord region syn- and anti-dihydrodiol epoxides by microsomes of Aroclor 1254-treated Sprague-Dawley rats has been examined. Since the fjord region dihydrodiol epoxides were hydrolytically unstable under the experimental conditions, their enzymatic formation was determined by analyzing the tetraols as their products of acidic hydrolysis upon addition of perchloric acid. The various stereoisomeric tetraols formed were separated by HPLC and identified by co-chromatography with authentic tetraols, which had been prepared by acidic hydrolysis of synt…
Relationship of Dibenzo[a, l]pyrene-DNA Binding to the Induction of p53, p21WAFIand Cell Cycle Arrest in Human Cells in Culture
Abstract The tumor suppressor protein p53 plays an important role in recognition of DNA damage and induction of subsequent cell cycle arrest. One of its target genes encodes the p21 WAFI protein which is involved in the mediation of growth arrest after DNA damage has occured. The exceptionally potent carcino-genic polycyclic aromatic hydrocarbon (PAH) dibenzo[a, l]pyrene (DB[a, l]P) and its ultimate metabolites, the fjord region (+)-syn- and (-)-anti-11,12-diol 13,14-epoxides (DB[a, l]PDE), were used in order to investigate DNA damage via adduct formation, subsequent induction of p53 and p21 WAFI , and cell growth behavior in human mammary carcinoma MCF-7 cells. Exposure of MCF-7 cells to 0…
Metabolic Activation of the (+)-S,S- and (−)-R,R-Enantiomers of trans-11,12-Dihydroxy-11,12-dihydrodibenzo[a,l]pyrene: Stereoselectivity, DNA Adduct Formation, and Mutagenicity in Chinese Hamster V79 Cells
Polycyclic aromatic hydrocarbons require metabolic activation in order to exert their biological activity initiated by DNA binding. The metabolic pathway leading to bay or fjord region dihydrodiol epoxides as ultimate mutagenic and/or carcinogenic metabolites is thought to play a dominant role. For dibenzo[a,l]pyrene, considered as the most potent carcinogenic polycyclic aromatic hydrocarbon, the formation of the fjord region syn- and/or anti-11,12-dihydrodiol 13,-14-epoxide (DB[a,l]PDE) diastereomers has been found to be the principal metabolic activation pathway in cell cultures leading to DNA adducts. In order to further elucidate the stereoselectivity involved in this activation pathway…
Correlation of the Extent of Fjord-Region Oxidation with DNA Binding and Mutagenicity of the Enantiomeric 11,12-Dihydrodiols of Dibenzo[a,l]pyrene
Abstract In vitro studies on the hepatic biotransformation of the enantiomeric trans-11,12-dihydrodiols of dibenzo[a,l]pyrene (DB[a,l]P) using microsomal fractions of animals pretreated with Aroclor 1254 revealed that the formation of fjord-region dihydrodiol epoxides strongly depends on the absolute configuration of the substrate. Both the (-)-11R,12R- and the (+)-11S,12S-enantiomer are converted diastereoselectively to the (-)- and (+)-anti-dihydrodiol epoxide, respectively, by either rat or mouse liver microsomes. Fjord-region oxidation occurs to greatest extent on incubation of the (-)-11R,12R-dihydrodiol with preparations from rats. This finding is in line with the differences seen for…