Black Raspberry Extract Enhances Glutathione Conjugation of the Fjord-Region Diol Epoxide Derived from the Tobacco Carcinogen Dibenzo[def,p]chrysene in Human Oral Cells

In a series of previous studies we reported that black raspberry (BRB) powder inhibits dibenzo[a,l]pyrene (DBP)-induced DNA damage, mutagenesis, and oral squamous cell carcinoma (OSCC) development in mice. In the present study, using human oral leukoplakia (MSK-Leuk1) and squamous cell carcinoma (SCC1483) cells, we tested the hypothesis that BRB extract (BRBE) will enhance the synthesis of glutathione (GSH) and in turn increase GSH conjugation of the fjord-region DBP diol epoxide (DBPDE) derived from DBP leading to inhibition of DBP-induced DNA damage. The syntheses of DBPDE-GSH conjugate, DBPDE-dA adduct, and the corresponding isotope-labeled internal standards were performed; LC-MS/MS methods were used for their quantification. BRBE significantly (p < 0.05) increased cellular GSH by 31% and 13% at 6 and 24 h, respectively, in OSCC cells; in MSK-LeuK1 cells, the levels of GSH significantly (p < 0.05) increased by 55% and 22%, at 1 and 6 h. Since BRBE significantly enhanced the synthesis of GSH in both cell types, subsequent experiments were performed in MSK-Leuk1 cells. Western blot analysis was performed to determine the types of proteins involved in the synthesis of GSH. BRBE significantly (p < 0.05) increased the protein expression (2.5-fold) of the glutamate-cysteine ligase catalytic subunit (GCLC) but had no effect on the glutamate-cysteine ligase modifier subunit (GCLM) and glutathione synthetase (GSS). LC-MS/MS analysis showed that pretreatment of cells with BRBE followed by DBPDE significantly (p < 0.05) increased the levels of DBPDE-GSH conjugate (2.5-fold) and decreased DNA damage by 74% measured by assessing levels of DBPDE-dA adduct formation. Collectively, the results of this in vitro study clearly support our hypothesis, and the LC-MS/MS methods developed in the present study will be highly useful in testing the same hypothesis initially in our mouse model and ultimately in smokers.

Marine Actinomycetes-Derived Secondary Metabolites Overcome TRAIL-Resistance via the Intrinsic Pathway through Downregulation of Survivin and XIAP

Resistance of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis represents the major hurdle to the clinical use of TRAIL or its derivatives. The discovery and development of lead compounds able to sensitize tumor cells to TRAIL-induced cell death is thus likely to overcome this limitation. We recently reported that marine actinomycetes’ crude extracts could restore TRAIL sensitivity of the MDA-MB-231 resistant triple negative breast cancer cell line. We demonstrate in this study, that purified secondary metabolites originating from distinct marine actinomycetes (sharkquinone (1), resistomycin (2), undecylprodigiosin (3), butylcyclopentylprodigiosin (4), elloxizanone A (5) and B (6), carboxyexfoliazone (7), and exfoliazone (8)), alone, and in a concentration-dependent manner, induce killing in both MDA-MB-231 and HCT116 cell lines. Combined with TRAIL, these compounds displayed additive to synergistic apoptotic activity in the Jurkat, HCT116 and MDA-MB-231 cell lines. Mechanistically, these secondary metabolites induced and enhanced procaspase-10, -8, -9 and -3 activation leading to an increase in PARP and lamin A/C cleavage. Apoptosis induced by these compounds was blocked by the pan-caspase inhibitor QvD, but not by a deficiency in caspase-8, FADD or TRAIL agonist receptors. Activation of the intrinsic pathway, on the other hand, is likely to explain both their ability to trigger cell death and to restore sensitivity to TRAIL, as it was evidenced that these compounds could induce the downregulation of XIAP and survivin. Our data further highlight that compounds derived from marine sources may lead to novel anti-cancer drug discovery.

Comparative Tumorigenicity and DNA Damage Induced by Dibenzo[ def,p]chrysene and Its Metabolites in the Mouse Ovary

Ovarian cancer ranked second in incidence among gynecologic cancers, but it causes more deaths than any other gynecologic cancer; at present there is no curative treatment beyond surgery. Animal models that employ carcinogens found in the human environment can provide a realistic platform to understand the mechanistic basis for disease development and to design rational chemopreventive/therapeutic strategies. We and others have shown that the administration of the environmental pollutant and tobacco smoke constituent dibenzo[ def,p]chrysene (DBP) to mice by several routes of exposure can induce tumors in multiple sites including the ovary. In the present study we compared, for the first time, the tumorigenicity and DNA damage induced by DBP and its metabolites DBP-dihydrodiol (DBPDHD) and DBP-dihydrodiol epoxide (DBPDE) in the mouse ovary. Compounds were dissolved in dimethyl sulfoxide (DMSO) as the vehicle and administered by topical application into the mouse oral cavity three times per week for 38 weeks. No tumors were observed in mice treated with DMSO. At equal dose (24 nmol/30 μL DMSO), the incidence of ovarian tumors induced by DBPDHD was higher (60.7%), although not significantly, than that induced by DBP (44.8%). Similarly the levels of DNA damage induced by DBPDHD in the ovary were higher than those observed with DBP. We did not observe any histological abnormality in the ovary of mice treated with DBPDE, which is consistent with lack of DNA damage. Our results suggested that both DBP and DBPDHD can be metabolized in the mouse ovary leading to the formation of DBPDE that can damage DNA, which is a prerequisite step in the initiation stage of carcinogenesis.

Effects of chronic alcohol consumption on DNA damage and immune regulation induced by the environmental pollutant dibenzo[a,l]pyrene in oral tissues of mice

Previously, we showed that oral application of the environmental pollutant dibenzo[a,l]pyrene (DB[a,l]P) induces oral tumors in mice. Thus, in the present investigation we examined the effect of alcohol on DB[a,l]P-induced DNA damage and immune regulation; we showed that alcohol (6.4% v/v in the diet, 35% of Calories) significantly enhanced the levels of (-)-anti-trans-DB[a,l]P-dA while decreased the levels of GSH in the mouse oral tissues. Analysis of RNA expression revealed that DB[a,l]P alone upregulates inflammatory genes while alcohol suppresses several markers of immune surveillance. Collectively, these results suggest that alcohol may enhance oral carcinogenesis induced by DB[a,l]P.

Human Microdosing with Carcinogenic Polycyclic Aromatic Hydrocarbons: In Vivo Pharmacokinetics of Dibenzo[def,p]chrysene and Metabolites by UPLC Accelerator Mass Spectrometry

Metabolism is a key health risk factor following exposures to pro-carcinogenic polycyclic aromatic hydrocarbons (PAHs) such as dibenzo[def,p]chrysene (DBC), an IARC classified 2A probable human carcinogen. Human exposure to PAHs occurs primarily from the diet in nonsmokers. However, little data is available on the metabolism and pharmacokinetics in humans of high molecular weight PAHs (≥4 aromatic rings), including DBC. We previously determined the pharmacokinetics of DBC in human volunteers orally administered a microdose (29 ng; 5 nCi) of [14C]-DBC by accelerator mass spectrometry (AMS) analysis of total [14C] in plasma and urine. In the current study, we utilized a novel "moving wire" interface between ultraperformance liquid chromatography (UPLC) and AMS to detect and quantify parent DBC and its major metabolites. The major [14C] product identified in plasma was unmetabolized [14C]-DBC itself (Cmax = 18.5 ±15.9 fg/mL, Tmax= 2.1 ± 1.0 h), whereas the major metabolite was identified as [14C]-(+/-)-DBC-11,12-diol (Cmax= 2.5 ±1.3 fg/mL, Tmax= 1.8 h). Several minor species of [14C]-DBC metabolites were also detected for which no reference standards were available. Free and conjugated metabolites were detected in urine with [14C]-(+/-)-DBC-11,12,13,14-tetraol isomers identified as the major metabolites, 56.3% of which were conjugated (Cmax= 35.8 ± 23.0 pg/pool, Tmax = 6-12 h pool). [14C]-DBC-11,12-diol, of which 97.5% was conjugated, was also identified in urine (Cmax = 29.4 ± 11.6 pg/pool, Tmax = 6-12 h pool). Parent [14C]-DBC was not detected in urine. This is the first data set to assess metabolite profiles and associated pharmacokinetics of a carcinogenic PAH in human volunteers at an environmentally relevant dose, providing the data necessary for translation of high dose animal models to humans for translation of environmental health risk assessment.

Predicting lung dosimetry of inhaled particleborne benzo[a]pyrene using physiologically based pharmacokinetic modeling

Benzo[a]pyrene (BaP) is a by-product of incomplete combustion of fossil fuels and plant/wood products, including tobacco. A physiologically based pharmacokinetic (PBPK) model for BaP for the rat was extended to simulate inhalation exposures to BaP in rats and humans including particle deposition and dissolution of absorbed BaP and renal elimination of 3-hydroxy benzo[a]pyrene (3-OH BaP) in humans. The clearance of particle-associated BaP from lung based on existing data in rats and dogs suggest that the process is bi-phasic. An initial rapid clearance was represented by BaP released from particles followed by a slower first-order clearance that follows particle kinetics. Parameter values for BaP-particle dissociation were estimated using inhalation data from isolated/ventilated/perfused rat lungs and optimized in the extended inhalation model using available rat data. Simulations of acute inhalation exposures in rats identified specific data needs including systemic elimination of BaP metabolites, diffusion-limited transfer rates of BaP from lung tissue to blood and the quantitative role of macrophage-mediated and ciliated clearance mechanisms. The updated BaP model provides very good prediction of the urinary 3-OH BaP concentrations and the relative difference between measured 3-OH BaP in nonsmokers versus smokers. This PBPK model for inhaled BaP is a preliminary tool for quantifying lung BaP dosimetry in rat and humans and was used to prioritize data needs that would provide significant model refinement and robust internal dosimetry capabilities.

New insights into BaP-induced toxicity: role of major metabolites in transcriptomics and contribution to hepatocarcinogenesis

Benzo(a)pyrene (BaP) is a ubiquitous carcinogen resulting from incomplete combustion of organic compounds and also present at high levels in cigarette smoke. A wide range of biological effects has been attributed to BaP and its genotoxic metabolite BPDE, but the contribution to BaP toxicity of intermediary metabolites generated along the detoxification path remains unknown. Here, we report for the first time how 3-OH-BaP, 9,10-diol and BPDE, three major BaP metabolites, temporally relate to BaP-induced transcriptomic alterations in HepG2 cells. Since BaP is also known to induce AhR activation, we additionally evaluated TCDD to source the expression of non-genotoxic AhR-mediated patterns. 9,10-Diol was shown to activate several transcription factor networks related to BaP metabolism (AhR), oxidative stress (Nrf2) and cell proliferation (HIF-1α, AP-1) in particular at early time points, while BPDE influenced expression of genes involved in cell energetics, DNA repair and apoptotic pathways. Also, in order to grasp the role of BaP and its metabolites in chemical hepatocarcinogenesis, we compared expression patterns from BaP(-metabolites) and TCDD to a signature set of approximately nine thousand gene expressions derived from hepatocellular carcinoma (HCC) patients. While transcriptome modulation by TCDD appeared not significantly related to HCC, BaP and BPDE were shown to deregulate metastatic markers via non-genotoxic and genotoxic mechanisms and activate inflammatory pathways (NF-κβ signaling, cytokine-cytokine receptor interaction). BaP also showed strong repression of genes involved in cholesterol and fatty acid biosynthesis. Altogether, this study provides new insights into BaP-induced toxicity and sheds new light onto its mechanism of action as a hepatocarcinogen.

Urinary elimination kinetics of 3-hydroxybenzo(a)pyrene and 1-hydroxypyrene of workers in a prebake aluminum electrode production plant: Evaluation of diuresis correction methods for routine biological monitoring

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous carcinogenic pollutants emitted in complex mixtures in the ambient air and contribute to the incidence of human cancers. Taking into account all absorption routes, biomonitoring is more relevant than atmospheric measurements to health risk assessment, but knowledge about how to use biomarkers is essential. In this work, urinary elimination kinetic of 1-hydroxypyrene (1-OHP) and 3-hydroxybenzo(a)pyrene (3-OHBaP) were studied in six electrometallurgy workers after PAHs exposure. Spot samples were collected on pre- and post-shift of the last workday then the whole urinations were separately sampled during the weekend. Non-linear mixed effects models were built to study inter- and intra-individual variability of both urinary metabolites toxicokinetic and investigate diuresis correction ways. Comparison of models confirmed the diuresis correction requirement to perform urinary biomonitoring of pyrene and BaP exposure. Urinary creatinine was found as a better way than specific gravity to normalize urinary concentrations of 1-OHP and as a good compromise for 3-OHBaP. Maximum observed levels were 1.0 µmol/mol creatinine and 0.8nmol/mol creatinine for 1-OHP and 3-OHBaP, respectively. Urinary 1-OHP concentrations on post-shift were higher than pre-shift for each subject, while 3-OHBaP levels were steady or decreased, and maximum urinary excretion rates of 3-OHBaP was delayed compared to 1-OHP. These results were consistent with the sampling time previously proposed for 3-OHBaP analysis, the next morning after exposure. Apparent urinary half-life of 1-OHP and 3-OHBaP ranged from 12.0h to 18.2h and from 4.8h to 49.5h, respectively. Finally, inter-individual variability of 1-OHP half-life seemed linked with the cutaneous absorption extent during exposure, while calculation of 3-OHBaP half-life required the awareness of individual urinary background level. The toxicokinetic modeling described here is an efficient tool which could be used to describe elimination kinetic and determine diuresis correction way for any other urinary biomarkers of chemicals or metals exposure.

Transcriptional Profiling of Dibenzo[def,p]chrysene-induced Spleen Atrophy Provides Mechanistic Insights into its Immunotoxicity in MutaMouse

Dibenzo[def,p]chrysene (DBC) is the most carcinogenic polycyclic aromatic hydrocarbon (PAH) examined to date. We investigated the immunotoxicity of DBC, manifested as spleen atrophy, following acute exposure of adult MutaMouse males by oral gavage. Mice were exposed to 0, 2.0, 6.2, or 20.0 mg DBC /kg-bw per day, for 3 days. Genotoxic endpoints (DBC-DNA adducts and lacZ mutant frequency in spleen and bone marrow, and red blood cell micronucleus frequency) and global gene expression changes were measured. All of the genotoxicity measures increased in a dose-dependent manner in spleen and bone marrow. Gene expression analysis showed that DBC activates p53 signaling pathways related to cellular growth and proliferation, which was evident even at the low dose. Strikingly, the expression profiles of DBC exposed mouse spleens were highly inversely correlated with the expression profiles of the only published toxicogenomics dataset of enlarged mouse spleen. This analysis suggested a central role for Bnip3l, a pro-apoptotic protein involved in negative regulation of erythroid maturation. RT-PCR confirmed expression changes in several genes related to apoptosis, iron metabolism, and aryl hydrocarbon receptor signaling that are regulated in the opposite direction during spleen atrophy versus benzo[a]pyrene-mediated splenomegaly. In addition, benchmark dose modeling of toxicogenomics data yielded toxicity estimates that are very close to traditional toxicity endpoints. This work illustrates the power of toxicogenomics to reveal rich mechanistic information for immunotoxic compounds and its ability to provide information that is quantitatively similar to that derived from standard toxicity methods in health risk assessment.

Phylum-specific regulation of resistomycin production in a Streptomyces sp. via microbial coculture

Actinomycete genomes are encoded with immense potential to produce secondary metabolites, however standard laboratory culture experiments rarely provide the conditions under which associated biosynthetic pathways are expressed. Despite years of research attempting to access these pathways and aside from a few well-studied bacterial quorum sensing systems, little is known about the specificity of secondary metabolite regulation in bacteria, such as the conditions under which a bacterium produces an antibiotic and the extent to which it does so in recognition of a particular species in the immediate environment. In the current study, we observed that the cocultivation of a Streptomyces sp. (strain B033) with four pathogenic strains of the phylum Proteobacteria resulted in the production of the antibiotic resistomycin. After further coculture experiments, we determined that Proteobacteria induced the production of resistomycin in B033 at significantly higher rates (65%) than strains from the phyla Firmicutes (5.9%) and Actinobacteria (9.1%), supporting that the regulation of secondary metabolism in bacteria can be dependent on the species present in the immediate environment. These results suggest a lack of promiscuity of antibiotic biosynthetic pathway regulation and indicate that it is feasible to mine existing microbial strain libraries for antibiotics in a phylum-specific manner.

In vitro metabolism of benzo[a]pyrene and dibenzo[def,p]chrysene in rodent and human hepatic microsomes

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and often carcinogenic contaminants released into the environment during natural and anthropogenic combustion processes. Benzo[a]pyrene (B[a]P) is the prototypical carcinogenic PAH, and dibenzo[def,p]chrysene (DBC) is a less prevalent, but highly potent transplacental carcinogenic PAH. Both are metabolically activated by isoforms of the cytochrome P450 enzyme superfamily to form reactive carcinogenic and cytotoxic metabolites. Metabolism of B[a]P and DBC was studied in hepatic microsomes of male Sprague-Dawley rats, naïve and pregnant female B6129SF1/J mice, and female humans, corresponding to available pharmacokinetic data. Michaelis-Menten saturation kinetic parameters including maximum rates of metabolism (VMAX, nmol/min/mg microsomal protein), affinity constants (KM, μM), and rates of intrinsic clearance (CLINT, ml/min/kg body weight) were calculated from substrate depletion data. CLINT was also estimated from substrate depletion data using the alternative in vitro half-life method. VMAX and CLINT were higher for B[a]P than DBC, regardless of species. Clearance for both B[a]P and DBC was highest in naïve female mice and lowest in female humans. Clearance rates of B[a]P and DBC in male rat were more similar to female human than to female mice. Clearance of DBC in liver microsomes from pregnant mice was reduced compared to naïve mice, consistent with reduced active P450 protein levels and elevated tissue concentrations and residence times for DBC observed in previous in vivo pharmacokinetic studies. These findings suggest that rats are a more appropriate model organism for human PAH metabolism, and that pregnancy's effects on metabolism should be further explored.

Co-metabolic degradation of benzo(e)pyrene by halophilic bacterial consortium at different saline conditions

Polyaromatic hydrocarbons (PAHs) with high molecular weight (more than three benzene rings) were difficult to degrade in saline environment. The present study details about the bacterial consortium enriched from industrial sludge from salt manufacturing company, Tuticorin, Tamilnadu (India), which was capable of degrading 1, 4 dioxane (Emerging micropollutant) and also phenanthrene as sole carbon source under saline condition. The halophilic bacterial consortium was able to degrade low molecular weight (LMW) phenanthrene, but unable to degrade high molecular weight (HMW) benzo(e)pyrene. To overcome this problem, phenanthrene was added as co-substrate along with benzo(e)pyrene which enhanced the biodegradation process by co-metabolism under saline conditions. The consortium potentially degraded 80% and 99% of benzo(e)pyrene in 7 days and phenanthrene in 5 days at 30 g l⁻¹ of NaCl concentration. When the saline concentration increased to 60 g l⁻¹, degradation of phenanthrene (97% in 8 days) and benzo(e)pyrene (65% in 10 days) was observed. Further increase in saline concentration to 90 g I⁻¹ of NaCI showed reduction in the percent degradation of phenanthrene and benzo(e)pyrene leads to 30.3% and 9% respectively in 6 days. Potential bacterial strains, present in PAHs degrading bacterial consortium were identified as Achromobacter sp. AYS3 (JQ419751), Marinobacter sp. AYS4 (JQ419752) and Rhodanobacter sp. AYS5 (JQ419753). The present study details about the effect of salinity on PAHs degradation and vital role of co-metabolism on biodegradation of benzo(e)pyrene with phenanthrene under saline conditions.

Exploring micromycetes biodiversity for screening benzo[a]pyrene degrading potential

Twenty-five strains of filamentous fungi, encompassing 14 different species and belonging mainly to Ascomycetes, were tested for their ability to degrade benzo[a]pyrene (BaP) in mineral liquid medium. The most performing isolates for BaP degradation (200 mg l(-1)) in mineral medium were Cladosporium sphaerospermum with 29 % BaP degradation, i.e., 82.8 μg BaP degraded per day (day(-1)), Paecilomyces lilacinus with 20.5 % BaP degradation, i.e., 58.5 μg BaP day(-1), and Verticillium insectorum with 22.3 % BaP degradation, i.e., 64.3 μg BaP day(-1), after only 7 days of incubation. Four variables, e.g., biomass growth on hexadecane and glucose, BaP solubilization, activities of extracellular- and mycelium-associated peroxidase, and polyethylene glycol degradation, were also studied as selective criteria presumed to be involved in BaP degradation. Among these variables, the tests based on polyethylene glycol degradation and on fungal growth on hexadecane and glucose seemed to be the both pertinent criteria for setting apart isolates competent in BaP degradation, suggesting the occurrence of different mechanisms presumed to be involved in pollutant degradation among the studied micromycetes.

The potential of gibberellic acid 3 (GA3) and Tween-80 induced phytoremediation of co-contamination of Cd and Benzo[a]pyrene (B[a]P) using Tagetes patula

The present study was conducted to investigate the effectiveness of GA(3) and Tween-80 on enhancing the phytoremediation of Cd-B[a]P co-contaminated soils. Results showed that the addition of GA(3) and GA(3)-Tween-80 enhanced Tagetes patula growth by 14%-32% and 23%-55%, respectively, relative to the control group. However, under independent GA(3)-treated soils, Cd and B[a]P concentrations in the shoots of the plants decreased by 15%-33% and 15%-53%, respectively, compared with CK. By contrast, the shoot concentration and accumulation of Cd under GA(3)-Tween-80 treatment increased by 0.01-0.46 and 1.33-1.55 times, respectively, whereas those of B[a]P increased from 0.57 to 0.82, and 1.33 to 1.55 times, respectively, compared with those of the control. Optimal result for Cd phytoextraction was obtained under combined 5 mmol Tween-80 kg(-1) and 1 mmol GA(3) kg(-1) treatment, and the maximum removal rate of B[a]P was obtained after the application of 5 mmol Tween-80 kg(-1) and 5 mmol GA(3) kg(-1).

Identification of metabolites from benzo[a]pyrene oxidation by ligninolytic enzymes of Polyporus sp. S133

The biodegradation of benzo[a]pyrene (BaP) by using Polyporus sp. S133, a white-rot fungus isolated from oil-contaminated soil was investigated. Approximately 73% of the initial concentration of BaP was degraded within 30 d of incubation. The isolation and characterization of 3 metabolites by thin layer chromatography, column chromatography, and UV-vis spectrophotometry in combination with gas chromatography-mass spectrometry, indicated that Polyporus sp. S133 transformed BaP to BaP-1,6-quinone. This quinone was further degraded in 2 ways. First, BaP-1,6-quinone was decarboxylated and oxidized to form coumarin, which was then hydroxylated to hydroxycoumarin, and finally to hydroxyphenyl acetic acid by addition of an epoxide group. Second, Polyporus sp. S133 converted BaP-1,6-quinone into a major product, 1-hydroxy-2-naphthoic acid. During degradation, free extracellular laccase was detected with reduced activity of lignin peroxidase, manganese-dependent peroxidase and 2,3-dioxygenase, suggesting that laccase and 1,2-dioxygenase might play an important role in the transformation of PAHs compounds.

Polycyclic aromatic hydrocarbons as skin carcinogens: comparison of benzo[a]pyrene, dibenzo[def,p]chrysene and three environmental mixtures in the FVB/N mouse

The polycyclic aromatic hydrocarbon (PAH), benzo[a]pyrene (BaP), was compared to dibenzo[def,p]chrysene (DBC) and combinations of three environmental PAH mixtures (coal tar, diesel particulate and cigarette smoke condensate) using a two stage, FVB/N mouse skin tumor model. DBC (4nmol) was most potent, reaching 100% tumor incidence with a shorter latency to tumor formation, less than 20 weeks of 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion compared to all other treatments. Multiplicity was 4 times greater than BaP (400 nmol). Both PAHs produced primarily papillomas followed by squamous cell carcinoma and carcinoma in situ. Diesel particulate extract (1 mg SRM 1650b; mix 1) did not differ from toluene controls and failed to elicit a carcinogenic response. Addition of coal tar extract (1 mg SRM 1597a; mix 2) produced a response similar to BaP. Further addition of 2 mg of cigarette smoke condensate (mix 3) did not alter the response with mix 2. PAH-DNA adducts measured in epidermis 12 h post initiation and analyzed by ³²P post-labeling, did not correlate with tumor incidence. PAH-dependent alteration in transcriptome of skin 12 h post initiation was assessed by microarray. Principal component analysis (sum of all treatments) of the 922 significantly altered genes (p<0.05), showed DBC and BaP to cluster distinct from PAH mixtures and each other. BaP and mixtures up-regulated phase 1 and phase 2 metabolizing enzymes while DBC did not. The carcinogenicity with DBC and two of the mixtures was much greater than would be predicted based on published Relative Potency Factors (RPFs).

Influence of earthworm activity on microbial communities related with the degradation of persistent pollutants

Earthworms may promote the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in soil, but the mechanism through which they exert such influence is still unknown. To determine if the stimulation of PAH degradation by earthworms is related to changes in microbial communities, a microcosm experiment was conducted consisting of columns with natural uncontaminated soil covered with PAH-contaminated dredge sediment. Columns without and with low and high Eisenia andrei densities were prepared. Organic matter and PAH content, microbial biomass, and dehydrogenase activity (DHA) were measured in soil and sediment over time. Biolog Ecoplate™ and polymerase chain reaction using denaturing gradient gel electrophoresis were used to evaluate changes in metabolic and structural diversity of the microbial community, respectively. Earthworm activity promoted PAH degradation in soil, which was significant for biphenyl, benzo[a]pyrene, and benzo[e]pyrene. Microbial biomass and DHA activity generally did not change over the experiment. Earthworm activity did change microbial community structure, but this did not affect its functioning in terms of carbon substrate consumption. Results suggest no relationship between changes in the microbial community by earthworm activity and increased PAH disappearance. The role of shifts in soil microbial community structure induced by earthworms in PAH removal needs further investigation.

Interaction studies of resistomycin from Streptomyces aurantiacus AAA5 with calf thymus DNA and bovine serum albumin

Resistomycin, a secondary metabolite produced by Streptomyces aurantiacus AAA5. The binding interaction of resistomycin with calf thymus DNA (CT DNA) and bovine serum albumin (BSA) was investigated by spectrophotometry, spectrofluorimetry, circular dichroism (CD) and synchronous fluorescence techniques under physiological conditions in vitro. Absorption spectral studies along with the fluorescence competition with ethidium bromide measurements and circular dichroism clearly suggest that the resistomycin bind with CT DNA relatively strong via groove binding. BSA interaction results revealed that the drug was found to quench the fluorescence intensity of the protein through a static quenching mechanism. The number of binding sites 'n' and apparent binding constant 'K' calculated according to the Scatchard equation exhibit a good binding property to bovine serum albumin protein. In addition, the results observed from synchronous fluorescence measurements clearly demonstrate the occurrence of conformational changes of BSA upon addition of the test compound.

1-Hydroxypyrene and 3-hydroxybenzo[a]pyrene as biomarkers of exposure to PAH in various environmental exposure situations

OBJECTIVE

To evaluate the utility of urinary 3-hydroxybenzo[a]pyrene (3-OH-B[a]P) as a biomarker of exposure to polycyclic aromatic hydrocarbons (PAHs) in various environmental exposure scenarios alongside the more usually studied 1-hydroxypyrene (1-OH-Pyr).

METHODS

Two groups of 15 and 10 non smoking, healthy men and women, were exposed for approximately 6h to ambient air at two outdoor locations close to metallurgical industries, and at one indoor location in an urban setting. Atmospheric measurements of 16 "priority" PAHs were carried out during each exposure. Urinary 1-OH-Pyr and 3-OH-B[a]P were also analysed, samples being taken the morning before exposure, at the end of exposure, then 4 and 15 h after the end of exposure. Urinary 1-OH-Pyr and 3-OH-B[a]P were analysed using high performance liquid chromatograph with fluorescence detection. Limits of detection (LOD) were 0.092 nmol/L and 0.28 pmol/L for 1-OH-Pyr and 3-OH-B[a]P respectively.

RESULTS

Average ambient air concentrations varied from 0.27 to 2.87 ng/m(3) for pyrene, 0.04 to 1.20 ng/m(3) for B[a]P, and from 70.0 to 910.6 ng/m(3) for the sum of the 16 PAH (SigmaPAHs). Concentrations of 1-OH-Pyr were not correlated with atmospheric concentrations of PAHs to which subjects were exposed, nor with the concentrations of 3-OH-B[a]P. Nearly 80% of measurements of 3-OH-B[a]P were lower than the LOD and no relationship between atmospheric concentrations and urinary metabolites was observable. However, the percentage of post-exposure values of 3-OH-B[a]P greater than the LOD increased significantly with the median of atmospheric concentrations of Pyr, B[a]P and SigmaPAH at the different sites (test of linear trend, p<0.02 in all cases).

CONCLUSION

Although we used very sensitive techniques for the measurements of urinary metabolites, especially for 3-OH-B[a]P, neither 1-OH-Pyr nor 3-OH-B[a]P were an unequivocal biomarker of exposure to atmospheric PAHs in environmental exposure scenarios relevant to the general population. It would be interesting to investigate other urinary monohydroxy PAH metabolites in this context.

Inhibition of procarcinogen-bioactivating human CYP1A1, CYP1A2 and CYP1B1 enzymes by melatonin

Administration of melatonin to rodents decreases the incidence of tumorigenesis initiated by benzo[a]pyrene or 7,12-dimethylbenz[a]anthracene, which requires bioactivation by cytochrome P450 enzymes, such as CYP1A1, CYP1A2 and CYP1B1, to produce carcinogenic metabolites. The present study tested the hypothesis that melatonin is a modulator of human CYP1 catalytic activity and gene expression. As a comparison, we also investigated the effect of melatonin on the catalytic activity of CYP2A6, which is also a procarcinogen-bioactivating enzyme. Melatonin (3-300 microm) decreased 7-ethoxyresorufin O-dealkylation catalyzed by human hepatic microsomes and recombinant CYP1A1, CYP1A2 and CYP1B1, whereas it did not affect coumarin 7-hydroxylation catalyzed by hepatic microsomes or recombinant CYP2A6. Melatonin inhibited CYP1 enzymes by mixed inhibition, with apparent K(i) values (mean +/- S.E.M.) of 59 +/- 1 (CYP1A1), 12 +/- 1 (CYP1A2), 14 +/- 2 (CYP1B1) and 46 +/- 8 microm (hepatic microsomes). Additional experiments indicated that melatonin decreased benzo[a]pyrene hydroxylation catalyzed by hepatic microsomes and CYP1A2 but not by CYP1A1 or CYP1B1. Treatment of MCF-10A human mammary epithelial cells with melatonin (up to 300 microm) did not affect basal or benzo[a]pyrene-inducible CYP1A1 or CYP1B1 gene expression. Consistent with this finding, melatonin did not influence reporter activity in aryl hydrocarbon receptor-dependent pGudluc6.1-transfected MCF-10A cells treated with or without benzo[a]pyrene, as assessed in an in vitro cell-based luciferase reporter gene assay. Overall, melatonin is an in vitro inhibitor of human CYP1 catalytic activity, and it may be useful to develop potent analogues of melatonin as potential cancer chemopreventive agents that block CYP1-mediated chemical carcinogenesis.

Enzyme activities during degradation of polycyclic aromatic hydrocarbons by white rot fungus Phanerochaete chrysosporium in soils

The degradation of three polycyclic aromatic hydrocarbons (PAHs), phenanthrene, pyrene and benzo[a]pyrene in soils by Phanerochaete chrysosporium, and the enzyme activities of lignin peroxidase (LiP) and manganese peroxidase (MnP) produced during degradation, were analyzed. The results showed that the 19-d percentage degradation ranged from 72.77+/-1.39% to 25.50+/-3.41% for the three compounds, and the maximum LiP and MnP activities ranged from 0.16+/-0.005 to 0.05+/-0.002 U g(-1) and from 1.92+/-0.03 to 0.54+/-0.03 U g(-1), respectively. Degradation percentage and enzyme activities both exhibited inverse relationships with the octanol/water partition coefficient (K(ow)) of the compounds, indicating that LiP and MnP from P. chrysosporium may be the primary enzymes responsible for PAH degradation in soil. As the soil organic matter (SOM) content increased from 0.3% for Soil 1 to 19% for Soil 4, the 19-d degradation percentage of pyrene decreased from 66.20+/-2.72% to 32.42+/-1.05%, and correspondingly, the maximum of LiP and MnP activities increased from 0.05+/-0.002 to 1.78+/-0.15 U g(-1) and from 0.34+/-0.03 to 1.78+/-0.15 U g(-1), respectively. Hence, it is plausible to conclude that the P. chrysosporium appeared to degrade not only the PAHs with small molecular size but also the macromolecular SOM. When SOM differences are large, as in this study, SOM has greater influence on enzyme activity than low-level exotic pollutants.

Benzo[a]pyrene degradation using simultaneously combined chemical oxidation, biotreatment with Fusarium solani and cyclodextrins

The interest of simultaneously combining chemical (Fenton's reaction) and biological treatments for the degradation of a high molecular weight polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) has been studied in laboratory tests. An optimal concentration of 1.5x10(-3) M H(2)O(2) as Fenton's reagent was firstly determined as being compatible with the growth of Fusarium solani, the Deuteromycete fungus used in the biodegradation process. For the enhancement of BaP solubilisation, cyclodextrins were also used in the performed tests. The best degradation performance was achieved through the use of 5x10(-3) M hydroxypropyl-beta-cyclodextrin (HPBCD) in comparison with randomly methylated-beta-cyclodextrin (RAMEB). When Fenton's treatment was combined with biodegradation, a beneficial effect on BaP degradation (25%) was obtained in comparison with biodegradation alone (8%) or with chemical oxidation alone (16%) in the presence of HPBCD for 12 days of incubation.

Rainbow trout (Oncorhynchus mykiss) and ultra-low dose cancer studies

Cancer risk assessment utilizing rodents requires extrapolation across five orders of magnitude to estimate the Virtually Safe Dose (VSD). Regulatory agencies rely upon the Linear Extrapolated Dose (LED) except when sufficient information on mechanism of action justifies alternative models. Rainbow trout (Oncorhynchus mykiss) has been utilized at Oregon State University as a model for human cancer for forty years. Low cost and high capacity, made possible by our unique facility, along with low spontaneous background and high sensitivity, allow design and conduct of statistically challenging studies not possible in rodents. Utilization of custom microarrays demonstrates similarities in gene expression in trout and human hepatocellular carcinoma (HCC). We have completed one study employing over 42,000 trout with dibenzo[a,l]pyrene (DBP) and determined the dose resulting in 1 additional cancer in 5000 animals, a 50-fold enhancement over the mouse ED(01) study. Liver tumor incidence at low dose deviated significantly from linearity (concave down), whereas, DBP-DNA adductions deviated slightly (convex up). A second study is underway with aflatoxin B(1) (AFB(1)). Results to date indicate AFB(1) at low dose, in contrast to DBP, elicits a linear dose-response function on the log-log scale which falls below the LED with a slope slightly greater than 1.0. Such studies demonstrate the statistical power of the trout cancer model and strengthen the case for incorporation of these data-sets into risk assessment for these environmental human carcinogens.

Enhanced kinetics of solid-phase microextraction and biodegradation of polycyclic aromatic hydrocarbons in the presence of dissolved organic matter

The uptake kinetics of fluorene, phenanthrene, fluoranthene, pyrene, and benzo[e]pyrene by solid-phase microextraction fibers was studied in the presence of dissolved organic matter (DOM) obtained from sediment pore water and resulted in increased fiber absorption and desorption rate coefficients. Compared to the control without DOM, these rate coefficients were increased at a DOM concentration of 36.62 mg/L by a factor of 1.27 to 2.21 and 1.31 to 2.10 for fluorene and benzo[e]pyrene, respectively. The calculated values for the fiber absorption and desorption rate coefficients show that diffusion through an unstirred boundary layer (UBL) surrounding the fiber probably forms the rate-limiting step of the process. The mineralization of aqueous-phase phenanthrene and pyrene by a representative polycyclic aromatic hydrocarbon (PAH)-degrading bacterium (Mycobacterium gilvum VM552) also was found to be enhanced by DOM. The initial degradation rates of phenanthrene (9.03 (microg/L) and pyrene (1.96 microg/L) were significantly higher compared to the control values and were enhanced by a factor of 1.32 and 1.26 at a DOM concentration of 43.14 and 42.15 mg/L, respectively. We suggest that such an enhancement results from the combination of faster uptake kinetics of the water-dissolved compounds in the UBL surrounding microbial cells and direct access of the bacteria to DOM-associated PAHs. These enhanced kinetic effects of DOM may have strong implications in sediment processes like desorption, nonequilibrium exposure, and biodegradation.

Inhibition of human cytochrome p450 1b1 further clarifies its role in the activation of dibenzo[a,l]pyrene in cells in culture

Metabolic activation and DNA adduct formation of the carcinogenic aromatic hydrocarbon dibenzo[a,l]pyrene (DBP) was investigated in human mammary carcinoma MCF-7 cells and human cytochrome P450 (CYP) 1B1-expressing Chinese hamster V79 cells in culture. It has been shown that DBP is metabolically activated to DNA-binding diol epoxides both in vitro and in vivo. To further establish the role of human CYP1B1 in the activation of DBP, both cell lines were cotreated with DBP and a selective chemical inhibitor of CYP1B1, 2,4,3' ,5'-tetramethoxy-stilbene (TMS). Results from DBP-DNA adduct analyses revealed the complete inhibition of DNA binding when cells were cotreated with DBP and TMS in comparison to DBP alone. Inactivation of CYP1B1 by TMS was also demonstrated through a decrease in the 7-ethoxyresorufin O-deethylase (EROD) activity in microsomes isolated from these cells. Emodin, 3-methyl-1,6,8-trihydroxyanthraquinone, an active ingredient of an herb, has been recently shown of being able to induce CYP1 gene expression. Examination of human CYP1B1 induction and EROD activity confirmed an increase in protein levels upon cotreatment with emodin and DBP. Despite increases in protein levels and enzyme activity, there was no significant change in DBP-DNA binding levels at very low substrate concentrations (17 nM). The data obtained in this study emphasize the central role of CYP1B1 in the activation of DBP in human cells in culture.

A structural gap in Dpo4 supports mutagenic bypass of a major benzo[a]pyrene dG adduct in DNA through template misalignment

Erroneous replication of lesions in DNA by DNA polymerases leads to elevated mutagenesis. To understand the molecular basis of DNA damage-induced mutagenesis, we have determined the x-ray structures of the Y-family polymerase, Dpo4, in complex with a DNA substrate containing a bulky DNA lesion and incoming nucleotides. The DNA lesion is derived from an environmentally widespread carcinogenic polycyclic aromatic hydrocarbon, benzo[a]pyrene (BP). The potent carcinogen BP is metabolized to diol epoxides that form covalent adducts with cellular DNA. In the present study, the major BP diol epoxide adduct in DNA, BP-N(2)-deoxyguanosine (BP-dG), was placed at a template-primer junction. Three ternary complexes reveal replication blockage, extension past a mismatched lesion, and a -1 frameshift mutation. In the productive structures, the bulky adduct is flipped/looped out of the DNA helix into a structural gap between the little finger and core domains. Sequestering of the hydrophobic BP adduct in this new substrate-binding site permits the DNA to exhibit normal geometry for primer extension. Extrusion of the lesion by template misalignment allows the base 5' to the adduct to serve as the template, resulting in a -1 frameshift. Subsequent strand realignment produces a mismatched base opposite the lesion. These structural observations, in combination with replication and mutagenesis data, suggest a model in which the additional substrate-binding site stabilizes the extrahelical nucleotide for lesion bypass and generation of base substitutions and -1 frameshift mutations.

Spectral differentiation and immunoaffinity capillary electrophoresis separation of enantiomeric benzo(a)pyrene diol epoxide-derived DNA adducts

Antibody cross-reactivity makes separation and differentiation of enantiomeric analytes one of the most challenging problems in immunoanalytical research, particularly for the analysis of structurally related biological molecules [such as benzo( a)pyrene (BP) metabolites and BP-derived DNA adducts]. It has recently been shown that the interaction of enantiomers of BP tetrols (BPT) with a promiscuous anti-polycyclic aromatic hydrocarbon ( anti-PAH) monoclonal antibody (mAb) allowed for separation of all four enantiomeric isomers using immunoaffinity capillary electrophoresis [ Grubor, N. M. , Armstrong, D. W. , and Jankowiak, R. ( 2006) Electrophoresis 27, 1078 ] and unambiguous spectral resolution using fluorescence line narrowing spectroscopy (FLNS) [ Grubor, N. M. , Liu, Y. , Han, X. , Armstrong, D.W. , and Jankowiak, R. ( 2006) J. Am.Chem. Soc. 128, 6409 ]. Here, we expand the use of the above two methodologies to the group of biologically important molecules that are products of BP diol epoxide (BPDE)-induced DNA damage. Four diastereomeric anti-BPDE-derived deoxyguanosine (dG) adducts, that is, (+)- and (-)- anti-trans-BPDE- N (2)-dG and (+)- and (-)- anti-cis-BPDE- N (2)-dG, were electrophoretically separated and spectroscopically differentiated using 8E11 mAb raised against BP-DNA conjugates. In fluorescence line narrowing spectroscopy (FLNS) experiments, complexes of BPDE-dG adducts with mAb revealed differences in fluorescence origin band positions, bandwidths, and vibrational patterns for all four BPDE- N (2)-dG adducts. Narrow fluorescence origin bands observed for (-)- trans-BPDE-dG (70 cm (-1)) and (+)- trans-BPDE- N (2)-dG (80 cm (-1)) suggest spatial constraint within the mAb binding pocket. Broader origin bands observed for cis type adducts ( approximately 120 cm (-1)) in 8E11 mAb suggest different binding geometries and/or conformational changes, as also indicated by changes in vibrational frequencies observed for the (+)- anti-cis and (-)- anti-cis adducts complexed with mAb. FLNS revealed that binding conformations and interactions within the mAb binding pocket are different for each adduct, enabling unambiguous positive identification. The methodologies described in this manuscript could also be used for analysis of DNA adducts following enzymatic hydrolysis of BPDE-adducted DNA to free nucleosides.

Cytotoxicity and mutagenicity of dibenzo[a,l]pyrene and (+/-)-dibenzo[a,l]pyrene-11,12-dihydrodiol in V79MZ cells co-expressing either hCYP1A1 or hCYP1B1 together with human glutathione-S-transferase A1

We have used V79MZ hamster lung fibroblasts stably transfected with human cytochrome P450-1A1 (hCYP1A1; cell line designated V79MZh1A1) or P450-1B1 (hCYP1B1; cell line designated V79MZh1B1) alone, or in combination with human glutathione-S-transferase (GST) alpha-1 (hGSTA1), in order to examine GST protection against cytotoxicity and mutagenicity of dibenzo[a,l]pyrene (DBP) and the intermediate dihydrodiol metabolite (+/-)-DBP-11,12-dihydrodiol (DBPD). At comparable expression levels of hCYP1A1 and hCYP1B1, both DBP and DBPD were more cytotoxic in V79MZ1A1 (IC(50)=2.7 and 0.7nM, respectively) than in V79MZh1B1 (IC(50)=6.0 and 4.8nM, respectively). In contrast, both DBP and DBPD were two- to four-fold more mutagenic in V79MZh1B1 than in V79MZ1A1. Co-expression of hGSTA1 with hCYP1A1 decreased DBP cytotoxicity two-fold compared to V79MZh1A1 with hCYP1A1 alone, and provided a small, yet still statistically significant, 1.3-fold protection against DBPD. Protection against mutagenicity of these compounds was comparable to that for cytotoxicity in cells expressing hCYP1A1. In V79MZh1B1 cells, co-expression of hGSTA1 conferred up to five-fold protection against DBP cytotoxicity, and up to nine-fold protection against the (+/-)-DBP-dihydrodiol cytotoxicity relative to the cells expressing hCYP1B1 alone. Co-expression of hGSTA1 also reduced mutagenicity of DBP or its dihydrodiol to a lesser extent (1.3-1.8-fold) than the protection against cytotoxicity in cells expressing hCYP1B1. These findings demonstrate that the protective efficacy of hGSTA1 against DBP and DBPD toxicity is variable, depending on the compound or metabolite present, the specific cytochrome P450 isozyme expressed, and the specific cellular damage endpoint examined.

Degradation of metabolites of benzo[a]pyrene by coupling Penicillium chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene (BaP) formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone (BP 1,6-quinone), trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP 7,8-diol), 3-hydroxybenzo[a]pyrene (3-OHBP), were identified by high-performance liquid chromatography (HPLC). The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that (1) the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; (2) the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; (3) the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% (w/v), concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.

Urban dust particulate matter alters PAH-induced carcinogenesis by inhibition of CYP1A1 and CYP1B1

The polycyclic aromatic hydrocarbons (PAHs) benzo[a]pyrene (B[a]P) and dibenzo[a,l]pyrene (DB[a,l]P) are well-studied environmental carcinogens, however, their potency within a complex mixture is uncertain. We investigated the influence of urban dust particulate matter (UDPM) on the bioactivation and tumor initiation of B[a]P and DB[a,l]P in an initiation-promotion tumorigenesis model. SENCAR mice were treated topically with UDPM or in combination with B[a]P or DB[a,l]P, followed by weekly application of the promoter 12-O-tetradecanoylphorbol-13 acetate. UDPM exhibited weak tumor-initiating activity but significantly delayed the onset of B[a]P-induced tumor initiation by two-fold. When cotreated with UDPM, DB[a,l]P-treated animals displayed no significant difference in tumor-initiating activity, compared with DB[a,l]P alone. Tumor initiation correlated with PAH-DNA adducts, as detected by (33)P-postlabeling and reversed-phase high-performance liquid chromatography. Induction of cytochrome P450 (CYP)1A1 and 1B1 proteins was also detected following UDPM treatment or cotreatment with B[a]P or DB[a,l]P, indicating PAH bioactivation. Further genotoxicity analyses by the comet assay revealed that cotreatment of UDPM plus B[a]P or DB[a,l]P resulted in increased DNA strand breaks, compared with PAH treatment alone. The metabolizing activities of CYP1A1 and CYP1B1, as measured by the 7-ethoxyresorufin O-deethylation (EROD) assay, revealed that UDPM noncompetitively inhibited CYP1A1 and CYP1B1 EROD activity in a dose-dependent manner. Overall, these data suggest that components within complex mixtures can alter PAH-induced carcinogenesis by inhibiting CYP bioactivation and influence other genotoxic effects, such as oxidative DNA damage. These data further suggest that in addition to the levels of potent PAH, the effects of other mixture components must be considered when predicting human cancer risk.

Polycyclic aromatic hydrocarbon (PAH) o-quinones produced by the aldo-keto-reductases (AKRs) generate abasic sites, oxidized pyrimidines, and 8-oxo-dGuo via reactive oxygen species

Reactive and redox-active polycyclic aromatic hydrocarbon (PAH) o-quinones produced by Aldo-Keto Reductases (AKRs) have the potential to cause depurinating adducts leading to the formation of abasic sites and oxidative base lesions. The aldehyde reactive probe (ARP) was used to detect these lesions in calf thymus DNA treated with three PAH o-quinones (BP-7,8-dione, 7,12-DMBA-3,4-dione, and BA-3,4-dione) in the absence and presence of redox-cycling conditions. In the absence of redox-cycling, a modest amount of abasic sites were detected indicating the formation of a low level of covalent o-quinone depurinating adducts (>3.2 x 10(6) dNs). In the presence of NADPH and CuCl2, the three PAH o-quinones increased the formation of abasic sites due to ROS-derived lesions destabilizing the N-glycosidic bond. The predominant source of AP sites, however, was revealed by coupling the assay with human 8-oxoguanine glycosylase (hOGG1) treatment, showing that 8-oxo-dGuo was the major lesion caused by PAH o-quinones. The levels of 8-oxo-dGuo formation were independently validated by HPLC-ECD analysis. Apyrimidinic sites were also revealed by coupling the assay with Escherichia coli (Endo III) treatment showing that oxidized pyrimidines were formed, but to a lesser extent. Different mechanisms were responsible for the formation of the oxidative lesions depending on whether Cu(II) or Fe(III) was used in the redox-cycling conditions. In the presence of Cu(II)-mediated PAH o-quinone redox-cycling, catalase completely suppressed the formation of the lesions, but mannitol and sodium benzoate were without effect. By contrast, sodium azide, which acts as a *OH and 1O2 scavenger, inhibited the formation of all oxidative lesions, suggesting that the ROS responsible was 1O2. However, in the presence of Fe(III)-mediated PAH o-quinone redox-cycling, the *OH radical scavengers and sodium azide consistently attenuated their formation, indicating that the ROS responsible was *OH.

Benzo[a]pyrene-7,8-quinone-3'-mononucleotide adduct standards for 32P postlabeling analyses: detection of benzo[a]pyrene-7,8-quinone-calf thymus DNA adducts

Benzo[a]pyrene-7,8-quinone (BPQ) is one of the reactive metabolites of the widely distributed archetypal polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P). The formation of BPQ from B[a]P through trans-7,8-dihydroxy-7,8-dihydroB[a]P by the mediation of aldo-keto reductases and its role in the genotoxicity and carcinogenesis of B[a]P currently are under extensive investigation. Toxicity pathways related to BPQ are believed to include both stable and unstable (depurinating) DNA adduct formation as well as reactive oxygen species. We previously reported the complete characterization of four novel stable BPQ-deoxyguanosine (dG) and two BPQ-deoxyadenosine (dA) adducts (Balu et al., Chem. Res. Toxicol. 17 (2004) 827-838). However, the identification of BPQ-DNA adducts by 32P postlabeling methods from in vitro and in vivo exposures required 3'-monophosphate derivatives of BPQ-dG, BPQ-dA, and BPQ-deoxycytidine (dC) as standards. Therefore, in the current study, BPQ adducts of dGMP(3'), dAMP(3'), and dCMP(3') were prepared. The syntheses of the BPQ-3'-mononucleotide standards were carried out in a manner similar to that reported previously for the nucleoside analogs. Reaction products were characterized by UV, LC/MS analyses, and one- and two-dimensional NMR techniques. The spectral studies indicated that all adducts existed as diastereomeric mixtures. Furthermore, the structural identities of the novel BPQ-dGMP, BPQ-dAMP, and BPQ-dCMP adducts were confirmed by acid phosphatase dephosphorylation of the BPQ-nucleotide adducts to the corresponding known BPQ-nucleoside adduct standards. The BPQ-dGMP, BPQ-dAMP, and BPQ-dCMP adduct standards were used in 32P postlabeling studies to identify BPQ adducts formed in vitro with calf thymus DNA and DNA homopolymers. 32P postlabeling analysis revealed the formation of 8 major and at least 10 minor calf thymus DNA adducts. Of these BPQ-DNA adducts, the following were identified: 1 BPQ-dGMP adduct, 2 BPQ-dAMP adducts, and 3 BPQ-dCMP adducts. This study represents the first reported example of the characterization of stable BPQ-DNA adducts in isolated mammalian DNA and is expected to contribute significantly to the future BPQ-DNA adduct studies in vivo and thereby to the contribution of BPQ in B[a]P carcinogenesis.

Molecular breeding of white rot fungus Pleurotus ostreatus by homologous expression of its versatile peroxidase MnP2

Using a DNA-mediated transformation technique, a molecular breeding approach to isolate Pleurotus ostreatus strains with enhanced productivity of its versatile peroxidase MnP2 was conducted. A recombinant mnp2 construct under the control of P. ostreatus sdi1 expression signals was introduced into the wild-type P. ostreatus strain by cotransformation with a carboxin-resistant marker plasmid. A total of 32 transformants containing the recombinant mnp2 sequence were isolated in a screening with specific amplification by PCR. Productivity of MnP2 in the recombinants was evaluated by the decolorization ability of Poly R-478 on agar plates in the absence of Mn2+. Recombinant P. ostreatus strains with elevated manganese peroxidase (MnP) productivity were successfully isolated. One of the recombinants, TM2-10, was demonstrated to secrete recombinant MnP2 predominantly on a synthetic medium containing 15 mM ammonium oxalate, which was confirmed by reverse transcription PCR (RT-PCR) and isozyme profile analysis using anion-exchange chromatography. The benzo[a]pyrene-removing activity by fungal treatment was also analyzed using the isolated recombinant strains.

Indole-3-carbinol in the maternal diet provides chemoprotection for the fetus against transplacental carcinogenesis by the polycyclic aromatic hydrocarbon dibenzo[a,l]pyrene

The fetus and neonate are sensitive targets for chemically induced carcinogenesis. Few studies have examined the risk/benefit of chemoprotective phytochemicals, given in the maternal diet, against transplacental carcinogenesis. In this study, B6129 SF1/J (AHR(b-1/d)) and 129Sv/ImJ (AHR(d/d)) mice were cross-bred. The polycyclic aromatic hydrocarbon, dibenzo[a,l]pyrene (DBP), was administered to pregnant mice (15 mg/kg, gavage) on gestation day 17, and 2000 p.p.m. indole-3-carbinol (I3C), a chemoprotective phytochemical from cruciferous vegetables, was fed to half of the mice from gestation day 9 until weaning. Offspring born to dams fed I3C exhibited markedly fewer mortalities (P < 0.0001). Maternal dietary exposure to I3C also significantly lowered lung tumor multiplicity (P = 0.035) in offspring surviving to 10 months of age. The I3C chemoprotection was independent of either maternal or fetal AHR genotype. The bioavailability of DBP to fetal target tissue was demonstrated by assessing DNA covalent adduction with a (33)P-post-labeling assay. The bioavailability of I3C was determined by dosing a subset of pregnant mice with [(14)C]-I3C. Addition of chemoprotective agents to the maternal diet during pregnancy and nursing may be an effective new approach in reducing the incidence of cancers in children and young adults.

NRH:quinone oxidoreductase 2 (NQO2) catalyzes metabolic activation of quinones and anti-tumor drugs

NRH:quinone oxidoreductase 2 (NQO2) is a cytosolic flavoprotein that utilizes NRH as electron donor. The present studies investigate the role of NQO2 in metabolic detoxification/activation of quinones and quinone based anti-tumor drugs. Chinese hamster ovary (CHO) cells stably overexpressing cDNA derived mouse NQO2 and mouse keratinocytes from DMBA-induced skin tumors in wild-type and NQO2-null mice were generated. The CHO cells overexpressing NQO2 and mouse keratinocytes expressing or deficient in NQO2 were treated with varying concentrations of mitomycin C (MMC), CB1954, MMC analog BMY25067, EO9, menadione and BP-3,6-quinone, in the absence and presence of NRH. The cytotoxicity of the drugs was evaluated by colony formation. The CHO cells overexpressing higher levels of mouse NQO2 showed significantly increased cytotoxicity to menadione, BP-3,6-quinone and to the anti-tumor drugs MMC and CB1954 when compared to CHO cells expressing endogenous NQO2. The cytotoxicity increased in presence of NRH. Similar results were also observed with BMY25067 and EO9 treatments, but to a lesser extent. The results on keratinocytes deficient in NQO2 supported the data from CHO cells. The inclusion of NRH had no effect on cytotoxicity of quinones and drugs in keratinocytes deficient in NQO2. Mouse NQO2 protein was expressed in bacteria, purified and used to study the role of NQO2 in MMC-induced DNA cross-linking. Bacterially expressed and purified NQO2 efficiently catalyzed MMC activation that led to DNA cross-linking. These results concluded that NQO2 plays a significant role in the metabolic activation of both quinones and anti-tumor drugs leading to cytotoxicity and cell death.

Competing roles of aldo-keto reductase 1A1 and cytochrome P4501B1 in benzo[a]pyrene-7,8-diol activation in human bronchoalveolar H358 cells: role of AKRs in P4501B1 induction

Benzo[a]pyrene (BP) requires metabolic activation to electrophiles to exert its deleterious effects. We compared the respective roles of aldo-keto reductase 1A1 (AKR1A1, aldehyde reductase) and P4501B1 in the formation of BP-7,8-dione and BP-tetrols, respectively, in intact bronchoalveolar cells manipulated to express either enzyme. Metabolite formation was confirmed by HPLC/MS and quantitatively measured by HPLC/UV/beta-RAM. In TCDD-treated H358 cells (P4501B1 expression), the anti-BPDE hydrolysis product BP-tetrol-1 increased over 3-12 h to a constant level. In H358 AKR1A1 transfectants, formation of BP-7,8-dione was elevated for 3-12 h but significantly decreased after 24 h. Interestingly, BP-tetrols were also detected in AKR1A1 transfectants even though they do not constitutively express P4501A1/P4501B1 enzymes. Northern and Western blotting confirmed the induction of P4501B1 by BP-7,8-dione in parental cells and the induction of P4501B1 by BP-7,8-diol in AKR1A1-transfected cells. P4501B1 induction was blocked in AKR1A1 transfectants by the AKR1A1 inhibitor (sulfonylnitromethane), the o-quinone scavenger (N-acetyl-l-cysteine), or the cytosolic AhR antagonist (diflubenzuron). Attenuation of P4501B1 induction in these cells was verified by measuring a decrease in BP-tetrol formation. Our studies show that the formation of BP-7,8-dione by AKR1A1 in human bronchoalveolar cells leads to an induction of P4501B1 and that a functional consequence of this induction is elevated anti-BPDE production as detected by increased BP-tetrol formation. Therefore, the role of AKR1A1 in the activation of BP-7,8-diol is bifunctional; that is, it directly activates BP-7,8-diol to the reactive and redox-active PAH o-quinone (BP-7,8-dione) and it indirectly trans-activates the P4501B1 gene by generating the aryl hydrocarbon receptor (AhR) ligand BP-7,8-dione.

3-Hydroxybenzo[a]pyrene in the urine of smokers and non-smokers

The people studied were male volunteers without occupational and dietary exposure to PAH: 27 smokers (10 cigarettes or more) and 27 non-smokers matched for age and socio-professional category. For each person, all the 24h voided urine samples were reassembled in a single sample. 1-Hydroxypyrene (1-OHPy) and 3-hydroxybenzo[a]pyrene (3-OHBaP) were then determined by automated column-switching high-performance liquid chromatography. Urinary 1-OHPy ranged from 0.041 to 0.530 micromol/molCreatinine (arithmetic mean 0.144, median 0.115) for smokers and from 0.01 to 0.148 mmol/molCreatinine (arithmetic mean 0.044, median 0.032) for non-smokers. These values are close to those of some other studies. Urinary 3-OHBaP ranged from <0.01 to 0.084 nmol/molCreatinine (arithmetic mean 0.030, median 0.023) for smokers and from <0.01 to 0.045 nmol/molCreatinine (arithmetic mean 0.014, median 0.011) for non-smokers. Considering more particularly the urinary 3-OHBaP values, the influence of smoking could be important among workers exposed to low levels of BaP (<100 ng/m(3)) and the concentrations for smokers were equivalent to most of the preshift values of exposed workers. The dietary BaP intake was slightly lower than the BaP intake for an average smoker. From the present study, temporary basic reference levels may be proposed for urinary 3-OHBaP.

Importance of UDP-glucuronosyltransferase 1A10 (UGT1A10) in the detoxification of polycyclic aromatic hydrocarbons: decreased glucuronidative activity of the UGT1A10139Lys isoform

UDP-glucuronosyltransferase 1A10 (UGT1A10) is an extrahepatic enzyme expressed in aerodigestive tract tissues that exhibits significant glucuronidation activity against the important procarcinogenic benzo(a)pyrene (BaP) metabolite, BaP-trans-7,8-dihydrodiol (BPD), and the UGT1A10 codon 139 (Glu>Lys) polymorphism was previously implicated in risk for orolaryngeal cancer by Elahi et al. in their 2003 study. To better assess the potential role of UGT1A10 in risk for tobacco-related cancers, the glucuronidation activity of UGT1A10 was compared with that of other known UGT enzymes against selected polycyclic aromatic hydrocarbons, and the effects of the codon 139 polymorphism on UGT1A10 function were examined in vitro. UGT1A10 exhibited considerably more glucuronidation activity as determined by Vmax/Km against 3-hydroxy (OH)-BaP, 7-OH-BaP, 9-OH-BaP, and 1-OH-pyrene than any other UGT1A family member. Although a kinetic comparison using Vmax could not be performed against family 2B UGTs, UGT1A10 exhibited a 1.7- to 254-fold lower Km than active family 2B UGTs against 3-OH-BaP, 7-OH-BaP, and 1-OH-pyrene. A significantly (p < 0.01) higher Vmax/Km was observed for homogenates from wild-type UGT1A10139Glu-overexpressing cells against all four BaP metabolites tested (3-OH-BaP, 7-OH-BaP, 9-OH-BaP, and BPD). A similarly significant (p < 0.05) increase in Vmax/Km was observed for homogenates from wild-type UGT1A10139Glu-overexpressing cells against 1-OH-pyrene. Significant differences in Km were observed for homogenates from wild-type UGT1A10139Glu-overexpressing cells against 1-OH-pyrene (p < 0.05) and 3-OH-BaP (p < 0.01). Reverse transcription-polymerase chain reaction of total lung RNA showed low levels of UGT1A10 expression in human lung tissue. Together, these studies implicate UGT1A10 as an important detoxifier of polycyclic aromatic hydrocarbons in humans and that the UGT1A10 codon 139 polymorphism may be an important determinant in risk for tobacco-related cancers.

Degradation of benzo[a]pyrene in an experimentally contaminated paddy soil by vetiver grass (Vetiveria zizanioides)

A pot experiment was conducted to study the effect of growing vetiver grass on the biodegradation of benzo[a]pyrene (B[a]P) under glasshouse conditions. Plant biomass, microbial biomass C and degradation of B[a]P were determined. B[a]P disappeared faster in the plant treatments than in unplanted controls. Disappearance of B[a]P was accompanied by an increase in soil microbial biomass C. Vetiver grass may promote the biodegradation of B[a]P under flooded conditions by plant roots by stimulating the microbial biomass. Microbial biomass was the main factor affecting dissipation of B[a]P under flooded conditions.

Effects of aloe, aloesin, or propolis on the pharmacokinetics of benzo[a]pyrene and 3-OH-benzo[a]pyrene in rats

This study was conducted to examine the effects of aloe and aloesin on the weight gain and blood chemistry as well as the pharmacokinetics of benzo[a]pyrene (BaP) and 3-OH-BaP in rats. The rats treated with multiple doses of aloe and aloesin (100 mg/kg every 12 h for 14-19 d) did not show any significant changes in the weight gain and blood biochemical parameters. In addition, the effects of oral treatment with aloe, aloesin, and propolis on the absorption and pharmacokinetics of benzo[a]pyrene (BaP) and its metabolite, 3-OH-BaP, were studied in rats. The treatment with a single oral dose (200 mg/kg) of aloe, aloesin, and propolis did not alter the concentration-time profiles of BaP and 3-OH-BaP after iv and oral administration of BaP. At higher oral doses (500 mg/kg), the biliary excretion of BaP and the urinary excretion of 3-OH-BaP were significantly increased, but the urinary excretion of BaP and the fecal excretion of 3-OH-BaP remained unaltered. Whether high doses of aloe increase the overall elimination of BaP deserves further investigation.

Kordiimonas gwangyangensis gen. nov., sp. nov., a marine bacterium isolated from marine sediments that forms a distinct phyletic lineage (Kordiimonadales ord. nov.) in the 'Alphaproteobacteria'

A marine bacterium, designated strain GW14-5(T), capable of degrading high-molecular-mass polycyclic aromatic hydrocarbons was isolated from the sediments of Gwangyang Bay, Republic of Korea, after enrichment culture for 2 years with a mixture of benzo[a]pyrene and pyrene. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate forms a phyletic lineage that is distinct from the seven known orders within the 'Alphaproteobacteria'. 16S rRNA gene sequence similarity of strain GW14-5(T) to all recognized bacterial species was not greater than 92%. The dominant fatty acids of the isolate were i-17:1 (46.2%), i-15:0 (15.1%) and i-17:0 (12.6%). The major respiratory quinone was MK-5, and the DNA G+C content was 39.3 mol%. Cells of strain GW14-5(T) were Gram-negative, motile, catalase-positive, oxidase-positive and weakly halophilic. Glucose, N-acetylglucosamine and maltose were utilized as sole carbon sources. The strain was positive for beta-glucosidase activity. Optimal growth of strain GW14-5(T) was at pH 7.0 and 37-40 degrees C and required the presence of 2% (w/v) NaCl. On the basis of this evidence, strain GW14-5(T) represents a novel genus and species in the 'Alphaproteobacteria' for which the name Kordiimonas gwangyangensis gen. nov., sp. nov. is proposed. The novel order Kordiimonadales is proposed for the distinct phyletic line represented by the genus Kordiimonas. The type strain is GW14-5(T) (=KCCM 42021(T)=JCM 12864(T)).

Age-related changes in oxidative DNA damage and benzo(a)pyrene diolepoxide-I (BPDE-I)-DNA adduct levels in human stomach

This study was conducted in order to obtain information on the association between age and oxidative DNA damage and benzo[a]pyrene diolepoxide-I (BPDE-I)-DNA adduct levels in the stomach tissues of normal subjects (n = 113). Subjects ranged from 17 to 75 yr. The levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, were measured by high-performance liquid chromatography-electrochemical detector (HPLC-ECD). BPDE-I-DNA adduct levels were quantitatively measured by enzyme-linked immunosorbent assay (ELISA) using the monoclonal antibody 8E11. Increase in 8-OHdG levels was observed in subjects from 31 to 60 yr of age. Higher levels of 8-OHdG were observed in the stomach tissues of those in the 51-60 yr old group. Although Helicobacter. Pylori-positive group subjects had higher 8-OHdG levels than those in the H. pylori-negative group, no age-related changes in 8-OHdG levels were observed in these groups. The levels of BPDE-I-DNA adduct also markedly increased with age. Higher levels of BPDE-I-DNA adduct were observed in subjects aged 61-70 yr, but this difference was not significant from other age groups. These results provide evidence that there is a progressive age-dependent accumulation of oxidative DNA damage and of BPDE-I-DNA adducts in human stomach tissues. It is possible that such damage contributes to the known increased incidence of gastric tumor with aging.

Identification and quantification of the depurinating DNA adducts formed in mouse skin treated with dibenzo[a,l]pyrene (DB[a,l]P) or its metabolites and in rat mammary gland treated with DB[a,l]P

Dibenzo[a,l]pyrene (DB[a,l]P) is the most potent carcinogenic polycyclic aromatic hydrocarbon and has been identified in the environment. Comparative tumorigenicity studies in mouse skin and rat mammary gland indicate that DB[a,l]P is slightly more potent than DB[a,l]P-11,12-dihydrodiol and much more potent than (+/-)-syn-DB[a,l]P-11,12-dihydrodiol-13,14-epoxide {(+/-)-syn-DB[a,l]PDE} and (+/-)-anti-DB[a,l]PDE. We report here the identification and quantification of the depurinating adducts formed in mouse skin treated with DB[a,l]P, DB[a,l]P-11,12-dihydrodiol, (+/-)-syn-DB[a,l]PDE, or (+/-)-anti-DB[a,l]PDE and rat mammary gland treated with DB[a,l]P. The biologically formed adducts were compared with standard adducts by their retention times on HPLC and their spectra obtained by fluorescence line-narrowing spectroscopy at low temperature. In mouse skin treated with DB[a,l]P, depurinating adducts comprised 99% of the total adducts. Most of the depurinating adducts were formed by one-electron oxidation, with 63% at Ade and 12% at Gua. The remainder were formed by the diol epoxide, with 18% at Ade and 6% at Gua. When mouse skin was treated with DB[a,l]P-11,12-dihydrodiol, depurinating adducts comprised 80% of the total, and the predominant one was with Ade (69%). Treatment of skin with (+/-)-syn-DB[a,l]PDE resulted in 32% depurinating adducts, primarily at Ade (25%), whereas treatment with (+/-)-anti-DB[a,l]PDE produced 97% stable adducts. The formation of depurinating adducts following treatment of rat mammary gland with DB[a,l]P resulted in approximately 98% depurinating adducts, with the major adducts formed by one-electron oxidation. Only one depurinating diol epoxide adduct was formed. Tumorigenicity, mutations, and DNA adduct data suggest that depurinating Ade adducts play a major role in the initiation of tumors by DB[a,l]P.

Identification and quantification of stable DNA adducts formed from dibenzo[a,l]pyrene or its metabolites in vitro and in mouse skin and rat mammary gland

The stable adducts of dibenzo[a,l]pyrene (DB[a,l]P) formed by rat liver microsomes in vitro were previously quantified, whereas the depurinating adducts were both identified and quantified [Li, et al. (1995) Biochemistry 34, 8043]. In this article, we report the identification and quantification of the stable DNA adducts obtained from DB[a,l]P and DB[a,l]P-11,12-dihydrodiol activated by rat liver microsomes and from reaction of (+/-)-anti-DB[a,l]P-11,12-dihydrodiol-13,14-epoxide (DB[a,l]PDE) and (+/-)-syn-DB[a,l]PDE with DNA in vitro. In addition, the stable DNA adducts were identified and quantified following treatment of mouse skin with DB[a,l]P, DB[a,l]P-11,12-dihydrodiol, (+/-)-anti-DB[a,l]PDE, or (+/-)-syn-DB[a,l]PDE in vivo and treatment of rat mammary gland with DB[a,l]P in vivo. The DNA adducts were analyzed by the (32)P-postlabeling method, and the major adducts were identified by comparison with standards. The six stable adducts of DB[a,l]P formed by rat liver microsomes in vitro were either guanine or adenine adducts of anti-DB[a,l]PDE or syn-DB[a,l]PDE. About 43% of the detected stable adducts from microsomes were with guanine and 44% were with adenine. The pattern of adducts formed from DB[a,l]P-11,12-dihydrodiol with microsomes was very similar to that from DB[a,l]P. Reaction of (+/-)-anti-DB[a,l]PDE with DNA in vitro formed higher levels of stable adducts (55% from guanine and 39% from adenine) than (+/-)-syn-DB[a,l]PDE did (about 44% with guanine and 47% with adenine). In mouse skin treated with DB[a,l]P, 1% of the total adducts detected were stable adducts, comprised of 51% guanine adducts and 46% from adenine; with DB[a,l]P-11,12-dihydrodiol, 54% of the total were stable adducts, with a pattern of adducts similar to those formed from DB[a,l]P. Treatment of mouse skin with (+/-)-syn-DB[a,l]PDE formed 68% stable adducts, mostly at guanine. With (+/-)-anti-DB[a,l]PDE, mouse skin contained almost exclusively (97%) stable adducts: 61% guanine adducts and 33% adenine adducts. In rat mammary gland treated with DB[a,l]P, 2% of the total adducts were stable, with 42% guanine adducts and 55% adenine adducts. Approximately equal to or greater amounts of stable guanine adducts were formed in all systems, except for rat mammary gland. In contrast, the majority of depurinating adducts were adenine adducts. The carcinogenic potencies of these compounds in mouse skin, published earlier, do not qualitatively or quantitatively correlate with stable adducts, but rather with depurinating adducts.