Role of the Bay- and L-Regions in the Metabolic Activation and Carcinogenicity of Picene and Dibenz[ a,h ]anthracene

Early carcinogenicity tests found no evidence of activity for picene but found considerable initiating and carcinogenic activity for DBA. More recent investigation suggests that both pentacyclics are complete carcinogens when administered as single s.c. injections in NMRI mice, despite findings that picene acts as neither an initiating nor promoting agent. To investigate this contradiction, the complete carcinogenicity of both isomers was compared by s.c. injection in female Sprague-Dawley rats. The results demonstrated that 1 w mol of DBA administered three times weekly for 20 doses, induced sarcomas in all test animals by 33 weeks (100%). Similar treatment with picene did not induce sarcoma in any test animals by 37 weeks (0%). These present results agree with the earlier studies. It follows then that the metabolic activation and carcinogenicity of DBA and picene are dependent on the presence of an L-region, but are independent of the presence of a bay-region.     

Analysis of Polycyclic Aromatic Compounds Using Microbore Columns

The gas chromatographic analysis of polycyclic aromatic compounds can be completed faster and with increased chromatographic resolution using microbore columns (Fast GC). Microbore columns contain two to three times the number of theoretical plates per meter when compared to 0.25 mm internal diameter (i.d.) capillary columns. The increased chromatographic resolving power of microbore columns enables separations to be carried out with much shorter columns giving rise to faster analysis times. Analysis times of priority polycyclic aromatic hydrocarbons on 20 m (5% phenyl, 0.1 mm i.d., 0.1 w m film thickness) and 10 m (5% phenyl, 0.1 mm i.d., 0.1 w m film thickness) columns are reduced by about 45% and 60% respectively in comparison with 30 m columns, and data quality (precision and accuracy) is not affected. All areas/parameters of the chromatographic system must be adjusted and optimized to ensure proper chromatographic performance. Smaller injection volumes (0.2-0.5 w L) and injection liners (1-2 mm i.d.) are required to obtain optimum (and reproducible) chromatography on 0.1 mm i.d. columns.     

UVA Light-Induced DNA Single-Strand Cleavage by Hydroxybenzo[ a ]pyrenes

UVA light-induced DNA single-strand cleavage by 1-hydroxy, 3-hydroxy, 7-hydroxy, and 9-hydroxybenzo[ a ]pyrenes (OH-B a Ps) and 6-acetoxybenzo[ a ]pyrene (6-OAc-B a P) was studied. Under experimental conditions, the concentrations of 1-OH, 3-OH, 7-OH, and 9-OH-B a Ps and 6-OAc-B a P needed to cause 25% of the supercoiled form I plasmid DNA to become relaxed form II DNA were found to be 0.6, 2.5, 1.0, 1.3, and 1.1 w M, respectively. These concentrations are all smaller than that of B a P, which was 6 w M. These results indicate that on photoirradiation, OH-B a Ps are more cytotoxic and/or genotoxic than their parent compound, B a P. Mechanistic studies reveal that singlet oxygen and superoxide free radicals are involved in causing DNA cleavage.     

Effects of Histidine on Light-Induced DNA Single-Strand Cleavage by Selected Polycyclic Aromatic Hydrocarbons

The combination of UVA light and 1-aminopyrene, 1-hydroxypyrene, 1-hydroxybenzo[ a ]pyrene, 3-aminofluoranthene, 6-aminochrysene, or 5-, 6-, and 7-methylbenz[ a ]anthracenes causes DNA single-strand cleavage. 1-Hydroxypyrene, 1-hydroxybenzo[ a ]pyrene, and 5-methylbenz[ a ]anthracene have been shown to cause DNA cleavage, at least partially, by generating singlet oxygen. Therefore, the presence of histidine, a singlet oxygen quencher, should inhibit the DNA photocleavage. However, the presence of 50 mM histidine greatly enhances the DNA photocleavage caused by these compounds. This effect is due to the inhibition of the photodegradation of the PAH compounds. Therefore, care must be taken when interpreting the singlet oxygen quenching data by histidine. Histidine may coexist with PAHs that have entered the body. The presence of histidine can alter the photochemical reaction and, possibly, the phototoxicity mechanism of the PAHs.     

Mass Spectral Analysis of Unstable N7-Aralkyl DNA Adducts Resulting from Reaction of 7-Sulfooxymethyl-12-methylbenz[ a ]anthracene (SMBA) with DNA and Deoxynucleotides

The unified hypothesis for PAH activation predicts that SMBA plays a role in the metabolic activation and carcinogenicity of 7,12-dimethylbenz[ a ]anthracene (DMBA). SMBA and closely related aralkylating agents are derived from 7-hydroxymethyl-12-methylbenz[ a ]anthracene (HMBA), a direct metabolite of DMBA, and react with bases in nucleic acids. This occurs by generation of a benzylic carbonium ion owing to the fact that sulfate is a good leaving group. Previous characterization of reaction products with deoxynucleotide-3'-monophosphates detected stable adducts as primarily resulting from reaction with adenine at the N6- and guanine at the N2-amino groups, respectively. Pyrimidine adducts were also found; however, examination of SMBA-reacted DNA confirmed that the purine bases were the major targets for reaction. We now report evidence for the formation of unstable DNA adducts, most likely by reaction with purine N-7 positions. Treatment of SMBA-reacted DNA with formic acid at 70°C for 60 min and examination of acidified reaction products with electrospray-positive mode mass spectrometry (ESI + MS) disclosed m/z 390 and 406 products corresponding to 12-methylbenz[ a ]anthracene-7-methylene-N7-adenine or -guanine, respectively. Release of these adducts is expected to be accompanied by generation of apurinic sites in DNA structure. Examination of alternative leaving groups on the aralkylating agent suggest the following relative reactivities with deoxyguanosine or deoxyadenosine: chloro > sulfooxy > acetoxy > iodo. It is our expectation that development of these analytical methodologies will enable us to assign a role for the participation of aralkylating agents in PAH carcinogenicity.     

Polyaromatic Hydrocarbons in Flue Gases from Waste Tire Combustion

With the aim of studying the polycyclic aromatic hydrocarbon (PAH) emissions when high calorific waste materials are used as nonfossil fuels, waste tire combustion has been performed in a laboratory plant. The goal was to compare the PAH emissions with the ones obtained when a fossil fuel is burned at the same combustion conditions. PAH emissions have been analyzed in solids collected in two cyclones at the exit of the combustor and in the trap system composed of a condenser, a filter (20 w m), and an adsorbent. After PAH extraction with dimethylformamide (DMF) by sonication and fluorescence spectroscopy in the synchronous mode (FS) analyses, it can be concluded that the nonfossil fuel generates higher PAH atmospheric pollution.     

Comparison of Sample Preparation and Analysis Using Solid-Phase Extraction and Solid-Phase Microextraction to Determine Monohydroxy PAH in Urine by GC/HRMS

Sample preparation techniques using solid-phase extraction (SPE) and solid-phase microextraction (SPME) are compared for the analysis of monohydroxy polycyclic aromatic hydrocarbons (OHPAH) in human urine. Urine samples spiked with five carbon-13 labeled internal standards are first enzymatically hydrolyzed. Sixteen OHPAH from eight parent compounds (naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[ c ]phenanthrene, and benz[ a ]anthracene) are then extracted along with the internal standards by these two different techniques. The analytes are derivatized by a silylating reagent before final analysis. Final separation and detection are performed by temperature-programmed capillary gas chromatography (GC) and high-resolution mass spectrometry (HRMS). The two extraction techniques are compared for sample preparation time, cost, throughput, reinjection possibility, frequency of outliers, matrix interference, signal linearity, and method detection limit. SPE demonstrates major advantages over SPME for most of these aspects.     

Photooxidation of Benzo[ de ]naphtho[2,1,8,7- stuv ]anthra[2,1,9,8- hijkl ]pentacene

This article describes the photooxidation of benzo[ de ]naphtho-[2,1,8,7- stuv ]anthra[2,1,9,8- hijkl ]pentacene (BNAP) synthesized by the condensation of naphthanthrone with zinc dust. When an o -dichlorobenzene solution of BNAP was irradiated with light of its maximum absorption wavelength (535 nm), the original absorption band was reduced and a new band appeared at longer wavelengths showing a peak at 606 nm. Excitation of the photobleached sample with 600 nm gave rise to fluorescence on the red side of that of BNAP by about 90 nm. The new fluorescence spectrum showed a vibrational progression of about 1,600 cm m 1 , which corresponds to the stretching of a carbonyl group. No spectral changes occurred in degassed solution. These findings suggest that BNAP reacts with singlet oxygen to form a ketone. Molecular orbital calculations revealed that the carbonyl group of the product is located at the C-18 position and that a hydroxy group is also present at the C-2 position; therefore the product is predicted as 2,18-dihydrobenzo[ de ]-naphtho[2,1,8,7- stuv ]anthra[2,1,9,8- hijkl ]pentacen-18-one.     

Benzo[ a ]pyrene-7,8-dione is More Mutagenic than Anti -BPDE on p53 and is Dependent on the Generation of Reactive Oxygen Species

Polycyclic aromatic hydrocarbons (PAHs) may cause lung cancer via metabolic activation. p53 is one of the most commonly mutated tumor suppressor genes in this disease. To determine whether PAH o -quinones cause change-in-function mutations in p53 , we employed a yeast reporter system. Treatment of p53 cDNA with ( - )- anti -7,8-dihydroxy-9 f ,10 f -epoxy-7,8,9,10-tetrahydro-benzo[ a ]pyrene, ( anti -BPDE, an ultimate carcinogen) or submicromolar concentrations of BP-7,8-dione under redox-cycling conditions (NADPH and CuCl 2 ) also caused p53 mutagenesis in a dose-dependent manner. It was found that BP-7,8-dione was 80 times more mutagenic than anti -BPDE under these conditions. p53 mutagenesis by BPQ was attenuated by ROS scavengers and completely abrogated by a combination of superoxide dismutase and catalase, indicating that both superoxide anion and hydroxyl radicals were the responsible mutagens. DNA sequencing demonstrated that over 46% of BPQ-induced mutations were G:C to T:A transversions. Together these data suggest that PAH o -quinones generate an endogenous mutagen (ROS) which leads to p53 inactivation.     

Evaluation of PAH: DNA Adduct Formation in Rats Fed Coal Tar-Contaminated Diets

Previous studies have demonstrated that mouse lung is a target organ for the tumorigenic and genotoxic effects of coal tar. The present study evaluated PAH:DNA adduct formation in lung, liver, forestomach, and mammary gland of female CD rats fed various types of coal tar-contaminated diets. Coal tar-contaminated soil, an organic extract of contaminated soil, neat coal tar, and diets containing only B[ a ]P were evaluated. Ingestion of coal tar diets resulted in detectable levels of DNA adducts in lung and forestomach tissue. These adducts were primarily derived from benzo[ c ]fluorene and B[ a ]P. The adduct derived from benzo[ c ]fluorene was the most predominant. No adducts were detected in liver and mammary gland under the conditions employed in this study. The formation of a benzo[ c ]fluorene-derived DNA adduct in rat lung following coal tar exposure is consistent with previous studies performed with mice.