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To establish the risk of the endocrine disrupting activity of polycyclic aromatic compounds, especially oxygenated and nitrated polycyclic aromatic hydrocarbons (oxy-PAHs and nitro-PAHs, respectively), antiandrogenic and estrogenic activities were determined using chemically activated luciferase expression (CALUX) assays with human osteoblast sarcoma cells. A total of 27 compounds including 9 oxy-PAHs (polycyclic aromatic ketones and quinones) and 8 nitro-PAHs was studied. The oxy-PAHs of 7H-benz[de]anthracen-7-one (BAO), 11H-benzo[a]fluoren-11-one (B[a]FO), 11H-benzo[b]fluoren-11-one (B[b]FO), and phenanthrenequinone (PhQ) exhibited significantly the potent inhibition of AR activation. All nitro-PAHs exhibited high antiandrogenic activities (especially high for 3-nitrofluoranthene (3-NFA) and 3-nitro-7H-benz[de]anthracen-7-one (3-NBAO)), and the AR inhibition was confirmed as noncompetitive for 3-NFA, 3-NBAO, and 1,3-dinitropyrene (1,3-DNPy). Antiandrogenic activity of 3-NFA demonstrated characteristically a U-shaped dose–response curve; however, the absence of fluorescence effect on the activity was confirmed. The prominent estrogenic activity dependent on dose–response curve was confirmed for 2 oxy-PAHs (i.e., B[a]FO and B[b]FO). Elucidating the role of AR and ER on the effects of polycyclic aromatic compounds (e.g., oxy- and nitro-PAHs) to endocrine dysfunctions in mammals and aquatic organisms remains a challenge.

Monocyclic aromatic amines, o-toluidine (o-Tol) and its structural analog o-anisidine (o-Ans), are IARC Group 1 and Group 2A urinary bladder carcinogens, respectively, and are involved in metabolic activation and DNA damage. Our recent study revealed that 2-methyl-N4-(2-methylphenyl) benzene-1,4-diamine (MMBD), a p-semidine-type homodimer of o-Tol, was detected and identified in an in vitro reaction of o-Tol with S9 mix and in vivo urinary samples of o-Tol-exposed rats. Potent mutagenic, genotoxic, and cytotoxic activities were reported with MMBD, suggesting its involvement in urinary bladder carcinogenesis. However, it remains unknown whether o-Ans is converted to active metabolites to induce DNA damage in a similar manner as o-Tol. In this study, we report that a novel o-Ans metabolite, 2-methoxy-N4-(2-methoxyphenyl) benzene-1,4-diamine (MxMxBD), a dimer by head-to-tail binding (p-semidine form), was for the first time identified in o-Ans-exposed rat urine. MxMxBD induced a stronger mutagenicity in N-acetyltransferase overexpressed Salmonella typhimurium strains and potent genotoxicity and cytotoxicity in human bladder carcinoma T24 cells compared with o-Ans. These results suggest that MxMxBD may to some extent contribute toward urinary bladder carcinogenesis. In addition to homodimerization, such as MxMxBD, heterodimerizations were observed when o-Ans was coincubated with o-Tol or aniline (Ani) in in vitro reactions with S9 mix. This study highlights the important consideration of homodimerizations and heterodimerizations of monocyclic aromatic amines, including o-Ans, o-Tol, and Ani, in the evaluation of the combined exposure risk of bladder carcinogenesis.

Chronic inflammation is deeply involved in various human disorders, such as cancer, neurodegenerative disorders, and metabolic disorders. Induction of epigenetic alterations, especially aberrant DNA methylation, is one of the major mechanisms, but how it is induced is still unclear. Here, we found that expression of TET genes, methylation erasers, was downregulated in inflamed mouse and human tissues, and that this was caused by upregulation of TET-targeting miRNAs such as MIR20A, MIR26B, and MIR29C, likely due to activation of NF-κB signaling downstream of IL-1β and TNF-α. However, TET knockdown induced only mild aberrant methylation. Nitric oxide (NO), produced by NOS2, enhanced enzymatic activity of DNA methyltransferases (DNMTs), methylation writers, and NO exposure induced minimal aberrant methylation. In contrast, a combination of TET knockdown and NO exposure synergistically induced aberrant methylation, involving genomic regions not methylated by either alone. The results showed that a vicious combination of TET repression, due to NF-κB activation, and DNMT activation, due to NO production, is responsible for aberrant methylation induction in human tissues.

o-Toluidine (o-Tol), a monocyclic aromatic amine, causes bladder cancer in humans and experimental animals and is therefore classified as a Group 1 carcinogen (IARC) in which the carcinogenicity of o-Tol is involved in metabolic activation, DNA damage, and DNA adduct formation. In the DNA adduct formation mechanism, o-Tol is metabolized by N-hydroxylation, N-acetoxylation, and then deacetoxylation to produce an electrophilic nitrenium ion, which is able to bind to a DNA base, such as dG-C8. Therefore, dG-C8-o-Tol is thought to be a plausible DNA adduct of o-Tol exposure. However, direct detection of dG-C8-o-Tol in biological samples has not been reported yet. Here, we show that a novel o-Tol metabolite, 2-methyl-N1-(2-methylphenyl)benzene-1,4-diamine (MMBD), a dimer by head-to-tail binding, was identified for the first time in o-Tol-exposed rat urine. MMBD was also detected in a reaction of o-Tol and S9 mix, indicating the formation was catalyzed by an enzymatic reaction. Moreover, MMBD showed a potent stronger mutagenicity in N-acetyltransferase overexpressed Salmonella typhimurium strains,and cytotoxicity in human bladder carcinoma T24 cells and human spleen lymphoblastoid TK6 cells compared with o-Tol. Furthermore, a DNA adduct (m/z 478.1) corresponding to dG-MMBD was detected in the reaction of calf thymus DNA with rat urine containing MMBD, and also in hepatic DNA of rats treated with o-Tol. These results therefore suggested that o-Tol-induced bladder carcinogenesis could be at least partly attributed to MMBD formation. The possible dimerization of monocyclic aromatic amines should be considered in the evaluation of the risk of bladder carcinogenesis after exposure.

The genotoxic activities of effluents from drainage water treatment plants were examined by using the novel umu tester strain NM8001, which lacks MutMst genes. To enhance the sensitivity of the LacZ assay, a BugBuster mix protein extraction reagent and TokyoGreen-β Gal for a fluorescence-galactosidase substrate were applied. Of the 24 sampling locations present in Kanagawa prefecture, Japan, water extracts from nine sampling points showed apparent genotoxic activities without metabolic activation. In contrast, water extracts from the upper sites of these water treatment plants did not show any significant genotoxic activities. The selected samples with genotoxic activity did not show significant mutagenicity toward Ames strains TA98 and TA100. Genotoxicity was also well correlated with the activity of a classical umu strain of TA1535/pSK1002; these findings indicate that the genotoxicity induced by oxidative damage was not a significant component of the genotoxicity.

Ten-eleven translocation (TET) proteins regulate DNA methylation and gene expression by converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Although Tet2/Tet3 deficiency has been reported to lead to myeloid cell, B-cell and invariant natural killer T (iNKT) cell malignancy, the effect of TET on regulatory T cells (Tregs) has not been elucidated. We found that Tet2/Tet3 deficiency in Tregs led to lethal hyperproliferation of CD4+Foxp3+ T cells in the spleen and mesenteric lymph nodes after 5 months of age. Additionally, in aged Treg-specific Tet2/Tet3-deficient mice, serum IgG1, IgG3, IgM and IgE levels were markedly elevated. High IL-17 expression was observed in both Foxp3+ and Fopx3- CD4+ T cells, and adoptive transfer of Tet2/Tet3-deficient Tregs into lymphopenic mice inhibited Foxp3 expression and caused conversion into IL-17-producing cells. However, the conserved non-coding DNA sequence-2 (CNS2) region of the Foxp3 gene locus, which has been shown to be particularly important for stable Foxp3 expression, was only partly methylated. We identified novel TET-dependent demethylation sites in the Foxp3 upstream enhancer, which may contribute to stable Foxp3 expression. Together, these data indicate that Tet2 and Tet3 are involved in Treg stability and immune homeostasis in mice.

Aryl hydrocarbons such as 3-nitrobenzanthrone (NBA), 4-aminobiphenyl (ABP), acetylaminofluorene (AAF), benzo(a)pyrene (BaP), and 1-nitropyrene (NP) form bulky DNA adducts when absorbed by mammalian cells. These chemicals are metabolically activated to reactive forms in mammalian cells and preferentially get attached covalently to the N2 or C8 positions of guanine or the N6 position of adenine. The proportion of N2 and C8 guanine adducts in DNA differs among chemicals. Although these adducts block DNA replication, cells have a mechanism allowing to continue replication by bypassing these adducts: translesion DNA synthesis (TLS). TLS is performed by translesion DNA polymerases—Pol η, κ, ι, and ζ and Rev1—in an error-free or error-prone manner. Regarding the NBA adducts, namely, 2-(2′-deoxyguanosin-N2-yl)-3-aminobenzanthrone (dG-N2-ABA) and N-(2′-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG-C8-ABA), dG-N2-ABA is produced more often than dG-C8-ABA, whereas dG-C8-ABA blocks DNA replication more strongly than dG-N2-ABA. dG-N2-ABA allows for a less error-prone bypass than dG-C8-ABA does. Pol η and κ are stronger contributors to TLS over dG-C8-ABA, and Pol κ bypasses dG-C8-ABA in an error-prone manner. TLS efficiency and error-proneness are affected by the sequences surrounding the adduct, as demonstrated in our previous study on an ABP adduct, N-(2′-deoxyguanosine-8-yl)-4-aminobiphenyl (dG-C8-ABP). Elucidation of the general mechanisms determining efficiency, error-proneness, and the polymerases involved in TLS over various adducts is the next step in the research on TLS. These TLS studies will clarify the mechanisms underlying aryl hydrocarbon mutagenesis and carcinogenesis in more detail.

Retroviral TET1 or hypoxia stabilize Foxp3 in iTregs generated in vitro, Since induced regulatory T cells (iTregs) can be produced in a large quantity in vitro, these cells are expected to be clinically useful to induce immunological tolerance in various immunological diseases. Foxp3 (Forkhead box P3) expression in iTregs is, however, unstable due to the lack of demethylation of the CpG island in the conserved non-coding sequence 2 (CNS2) of the Foxp3 locus. To facilitate the demethylation of CNS2, we over-expressed the catalytic domain (CD) of the ten-eleven translocation (TET) protein, which catalyzes the steps of the iterative demethylation of 5-methylcytosine. TET-CD over-expression in iTregs resulted in partial demethylation of CNS2 and stable Foxp3 expression. We also discovered that TET expression was enhanced under low oxygen (5%) culture conditions, which facilitated CNS2 DNA demethylation and stabilization of Foxp3 expression in a TET2- and TET3-dependent manner. In combination with vitamin C treatment, which has been reported to enhance TET catalytic activity, iTregs generated under low oxygen conditions retained more stable Foxp3 expression in vitro and in vivo and exhibited stronger suppression activity in a colitis model compared with untreated iTregs. Our data indicate that the induction and activation of TET enzymes in iTregs would be an effective method for Treg-mediated adoptive immunotherapy.

Background The human genome is constantly exposed to numerous environmental genotoxicants. To prevent the detrimental consequences induced by the expansion of damaged cells, cellular protective systems such as nucleotide excision repair (NER) exist and serve as a primary pathway for repairing the various helix-distorting DNA adducts induced by genotoxic agents. NER is further divided into two sub-pathways, namely, global genomic NER (GG-NER) and transcription-coupled NER (TC-NER). Both NER sub-pathways are reportedly involved in the damage response elicited by exposure to genotoxins. However, how disruption of these sub-pathways impacts the toxicity of different types of environmental mutagens in human cells is not well understood. Results To evaluate the role of NER sub-pathways on the cytotoxic effects of mutagens, we disrupted XPC and CSB to selectively inactivate GG-NER and TC-NER, respectively, in human lymphoblastoid TK6 cells, a standard cell line used in genotoxicity studies. Using these cells, we then comparatively assessed their respective sensitivities to representative genotoxic agents, including ultraviolet C (UVC) light, benzo [a] pyrene (B(a)P), 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP), γ-ray, and 2-acetylaminofluorene (2-AAF). CSB −/− cells exhibited a hyper-sensitivity to UVC, B(a)P, and MeIQx. On the other hand, XPC −/− cells were highly sensitive to UVC, but not to B(a)P and MeIQx, compared with wild-type cells. In contrast with other genotoxins, the sensitivity of XPC −/− cells against PhIP was significantly higher than CSB −/− cells. The toxicity of γ-ray and 2-AAF was not enhanced by disruption of either XPC or CSB in the cells. Conclusions Based on our findings, genetically modified TK6 cells appear to be a useful tool for elucidating the detailed roles of the various repair factors that exist to combat genotoxic agents, and should contribute to the improved risk assessment of environmental chemical contaminants.

Photodynamic therapy (PDT) is a widely used medicinal treatment for the cancer therapy that utilizes the combination of a photosensitizer (PS) and light irradiation. In this study, we synthesized two novel C60 fullerene derivatives, compounds 1 and 2, with a psoralen moiety that can covalently bind to DNA molecules via cross-linking to pyrimidine under photoirradiation. Along with several fullerene derivatives, the biological properties of several novel compounds have been evaluated. Compounds 1 and 2, which have been shown to induce the production of hydroxyl radicals using several ROS detecting reagents, induced DNA strand breaks with relatively weak activities in the in vitro detection system using a supercoiled plasmid. However, the psoralen-bound fullerene with carboxyl groups (2) only showed genotoxicity in the genotoxicity assay system of the umu test. Compound 2 was also seen to have cytotoxic activities in several cancer cell lines at higher doses compared to water-soluble fullerenes.

In natural water, copper is believed to be complexed with organic materials such as humic and fulvic acids, as well as anthropogenic substances such as ethylenediaminetetraacetic acid (EDTA). The nature of the complexes is known to be a main factor in determining copper toxicity to aquatic biota, as well as its geochemical transport. In this study, organically chelated copper species in river water were revealed to be classified into hydrophobic and anionic components using column cartridge separation techniques based on C18 and anion exchange. The amounts of anionic ligated copper species in the tested water samples ranged from 0 to 46 nM, and the average contribution of the anionic ligated copper to the total dissolved copper concentration was around 30 %. Several water samples contained discharged sewage effluents with high contents of EDTA, which may be the main chelating agent responsible for copper retention on the anionic ion exchange cartridge column. However, most of the river water samples were not contaminated with EDTA, and therefore, fulvic substances are expected to be responsible for retention. As this is the first observation of anionic copper species in the natural aquatic environment, further geochemical and biological studies of these substances should be undertaken.

Fullerene is a well-known carbon nanomaterial, which can be potentially used for drug manufacture or delivery. Despite several successful examples of utilizing fullerene derivatives as drug candidate materials, their low water solubility under physiological conditions negatively affects the cell penetration efficiency after treatment. In this work, we successfully synthesized two fullerene derivatives with covalently attached fluorescein and boron dipyrromethene (BODIPY) fluorophore moieties, which exhibited cellular uptake and intracellular localization. While both fluorophores decreased their fluorescence intensity in the vicinity of fullerene, the cellar uptake of the fluorescein-modified fullerene was detected via fluorescence microscopy observations. Moreover, decreases in the fluorescence intensities of the intact fluorescein and BODIPY species were observed when both fluorophores and fullerene coexisted in aqueous media.

Fipronil is a phenylpyrazole-based insecticide and one of the relatively new widely used generations of insecticides whose biochemical action differs from the more traditional insecticides such as the organo-phosphates and -carbamates. Although several studies have been reported to determine the fate of Fipronil under environmental field conditions, including irradiation with UVB/UVA natural or simulated sunlight (wavelength >290–300 nm), which resulted in the formation of products that retained the basic phenylpyrazole structure, the present article examines the photodegradation of Fipronil upon irradiation of aqueous solutions under both reducing (nitrogen) and oxidative (air oxygen) atmospheric conditions at 254 nm (UVC; low-pressure Hg lamp), and for comparison purposes in the presence of the wide band-gap (4.8–5.0 eV) gallium sesquioxide (β-Ga2O3) semiconductor (and for comparison also TiO2). The fate of the insecticide under such conditions was ascertained by absorption spectroscopy in the UVC spectral region, by HPLC techniques for the desulfonation, defluorination, dechlorination and formation of both nitrate and ammonium ions, in addition to ESI-TOF-MS mass spectral methods to identify some of the possible intermediates that may have formed following the breakup of the phenyl and pyrazole rings. Mass spectra indicated that within 30 min filoprin was converted to Fipronil-desulfinyl (loss of SO fragment; photoproduct (III)) and in less than 1 hour of irradiation a significant quantity of the insecticide's photoproduct (III) had also decomposed as no significant mass peaks were seen above m/z = 319. The largest yields of SO42− (79%), F− (44%), Cl− (33%), NO3− (34%) and NH4+ (15%) were obtained under air-equilibrated conditions in the presence of the metal oxide β-Ga2O3 (Ga2O3/O2), followed by air O2, Ga2O3/N2 and under N2 atmospheric conditions. Frontier electron densities and partial charges on all the atoms of Fipronil were calculated (hf/6-31g* configuration; Gaussian 09 software) to infer a possible, albeit not detailed, pathway(s) for the direct photolysis and when the metal oxides were involved in the photodegradation. In addition, Ames tests were carried out on the intermediate products of the photodegradation of Fipronil after 3 h and 24 h of UVC illumination; none of the intermediates displayed mutagenic activity.

3-Nitrobenzanthrone (3-nitro-7H-benz[d,e]anthracen-7-one, 3-NBA) is a potent environmental mutagen that is found in diesel exhaust fumes and airborne particulates. It is known to produce several DNA adducts, including three major adducts N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG-C8-N-ABA), 2-(2'-deoxyadenosin-N(6)-yl)-3-aminobenzanthrone (dA-N(6)-C2-ABA), and 2-(2'-deoxyguanosin-N(2)-yl)-3-aminobenzanthrone (dG-N(2)-C2-ABA) in mammalian cells. In the present study, we measured the quantity of the formation and subsequent reduction of these adducts in human hepatoma HepG2 cells that had been treated with 3-NBA using LC-MS/MS analysis. As a result, dG-C8-N-ABA and dG-N(2)-C2-ABA were identified as major adducts in the HepG2 cells, and dA-N(6)-C2-ABA was found to be a minor adduct. Treatment with 1μg/mL 3-NBA for 24h induced the formation of 2835±1509 dG-C8-N-ABA and 3373±1173 dG-N(2)-C2-ABA per 10(7) dG and 877±330 dA-N(6)-C2-ABA per 10(7) dA in the cells. The cellular DNA repair system removed the dG-C8-N-ABA and dA-N(6)-C2-ABA adducts more efficiently than the dG-N(2)-C2-ABA adducts. After a 24-h repair period, 86.4±11.1% of the dG-N(2)-C2-ABA adducts remained, whereas only 51.7±2.7% of the dG-C8-N-ABA adducts and 37.8±1.7% of the dA-N(6)-C2-ABA adducts were present in the cells. We also evaluated the efficiency of bypasses across these three adducts and their mutagenic potency by introducing site-specific mono-modified plasmids into human cells. This translesion DNA synthesis (TLS) assay showed that dG-C8-N-ABA blocked DNA replication markedly (its replication frequency was 16.9±2.7%), while the replication arrests induced by dG-N(2)-C2-ABA and dA-N(6)-C2-ABA were more moderate (their replication frequencies were 33.3±6.2% and 43.1±7.5%, respectively). Mutagenic TLS was observed more frequently in replication across dG-C8-N-ABA (30.6%) than in replication across dG-N(2)-C2-ABA (12.1%) or dA-N(6)-C2-ABA (12.1%). These findings provide important insights into the molecular mechanism of 3-NBA-mutagenesis.

Persistent fluorinated substances, such as the fluorine-bearing pharmaceutical drugs Fluoxetine (FLX; Prozac) and Fluvoxamine maleate (FOM) together with several other substrates (fluorobenzoic acid and fluoroaliphatic model compounds), were photochemically defluorinated and degraded under UVC illumination in relatively good yields in the presence of a wide band gap metal oxide (β-Ga2O3) in heterogeneous aqueous media. The formation of fluoride ions increased with increasing illumination time under an inert nitrogen atmosphere, the transformation of the aromatic moiety was slower under these conditions, but nonetheless it did occur. The optimal amount of β-Ga2O3 loading for defluorination was 50 mg in aqueous media (0.10 mM, 100 mL); the optimal pH to defluorinate FLX was pH 6. Platinization (1 wt%) of the gallium oxide particles enhanced defluorination under an inert nitrogen atmosphere, but was decreased under an oxygen atmosphere; however, in the latter case the degradation of the substrates was facilitated as witnessed by loss of the aromatic moiety. The Ames test on the intermediate products from the photodegradation of FLX and 4-(trifluoromethyl)benzoic acid after long illumination times revealed that none were mutagenic.

The Streptomyces coelicolor A3(2) genome encodes a possible secretion protein, SCO5461, that shares a 30% homology with the activity domains of two toxic ADP-ribosyltransferases, pierisins and mosquitocidal toxin. We found ADP-ribosylating activity for the SCO5461 protein product through its co-incubation with guanosine and NAD(+), which resulted in the formation of N(2)-(ADP-ribos-1-yl)-guanosine ((ar2)Guo), with a K(m) value of 110 μM. SCO5461 was further found to ADP-ribosylate deoxyguanosine, GMP, dGMP, GTP, dGTP, and cyclic GMP with k(cat) values of 150-370 s(-1). Oligo(dG), oligo(G), and yeast tRNA were also ADP-ribosylated by this protein, although with much lower k(cat) values of 0.2 s(-1) or less. SCO5461 showed maximum ADP-ribosylation activity towards guanosine at 30 °C, and maintained 20% of these maximum activity levels even at 0 °C. This is the first report of the ADP-ribosylation of guanosine and guanine mononucleotides among the family members of various ADP-ribosylating enzymes. We additionally observed secretion of the putative gene product, SCO5461, in liquid cultures of S. coelicolor. We thus designated the SCO5461 protein product as S. coelicolor ADP-ribosylating protein, ScARP. Our current results could offer new insights into not only the ADP-ribosylation of small molecules but also signal transduction events via enzymatic nucleoside modification by toxin-related enzymes.

3-Nitrobenzanthrone (3-NBA), a potential human carcinogen, is present in diesel exhaust. The main metabolite of 3-NBA, 3-aminobenzanthrone, was detected in urine of miners occupationally exposed to diesel emissions. Environmental and occupational factors play an important role in development of bladder cancer (BC), one of the most frequent malignancies. It is expected that exposure of urothelium to 3-NBA and its metabolites may induce BC initiation and/or progression. To test this hypothesis, we studied geno- and cytotoxicity of 3-NBA using an in vitro BC model. 3-NBA induced higher levels of DNA adducts, reactive oxygen species and DNA breaks in aggressive T24 cells than in more differentiated RT4 cells. To understand the nature of this difference we examined the role of several enzymes that were identified as 3-NBA bio activators. However, the difference in DNA adduct formation cannot be directly linked to the different activity of any of the examined enzymes. Conversely, the difference of tested cell lines in p53 status can partly explain the distinct levels of 3-NBA-DNA adducts and DNA damage induced by 3-NBA. Therefore, we assume that more aggressive T24 cells are more predisposed for DNA adduct formation, DNA damage and, possibly, mutations and as a result further tumorigenesis.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundant heterocyclic amine in cooked foods, and is both mutagenic and carcinogenic. It has been suspected that the carcinogenicity of PhIP is derived from its ability to form DNA adducts, principally dG-C8-PhIP. To shed further light on the molecular mechanisms underlying the induction of mutations by PhIP, in vitro DNA synthesis analyses were carried out using a dG-C8-PhIP-modified oligonucleotide template. In this template, the dG-C8-PhIP adduct was introduced into the second G of the TCC GGG AAC sequence located in the 5′ region. This represents one of the mutation hot spots in the rat Apc gene that is targeted by PhIP. Guanine deletions at this site in the Apc gene have been found to be preferentially induced by PhIP in rat colon tumors. DNA synthesis with A- or B-family DNA polymerases, such as Escherichia coli polymerase (pol) I and human pol δ, was completely blocked at the adducted guanine base. Translesional synthesis polymerases of the Y-family, pol η, pol ι, pol κ, and REV1, were also used for in vitro DNA synthesis analyses with the same templates. REV1, pol η, and pol κ were able to insert dCTP opposite dG-C8-PhIP, although the efficiencies for pol η and pol κ were low. pol κ was also able to catalyze the extension reaction from the dC opposite dG-C8-PhIP, during which it often skipped over one dG of the triple dG sequence on the template. This slippage probably leads to the single dG base deletion in colon tumors.

Translesion DNA synthesis (TLS) is a tolerance pathway of replication block caused by DNA lesions. To measure the efficiency and fidelity of TLS in human cells, we established a shuttle vector assay by modifying of a bacterial TLS assay system. The assay consists of transfection of DNA repair-deficient human cells with a plasmid possessing a single DNA adduct, and transformation of indicator bacteria with plasmids extracted from the cells. We show that plasmid replication was suppressed to 1/9 by a single aminobiphenyl-dG adduct, and the mutant frequency of TLS-operated plasmids was 0.31, of which the major mutation (78%) was G to T transversion. The results demonstrate that this assay is applicable in practice for investigating TLS in human cells.

3-Nitrobenzanthrone (3-NBA) is a potent environmental mutagen and a potential human carcinogen present in diesel exhaust and airborne particulates. N-acetoxy-3-aminobenzanthrone (N-Aco-ABA) has been shown to be a major reactive metabolite of 3-NBA, which mainly produces adducts with guanine and adenine in cellular DNA. Here we analyzed mutations induced by N-Aco-ABA using supF shuttle vector plasmids to elucidate the mutagenic specificity of 3-NBA in human cells. Base sequence analysis of more than 100 plasmids with supF mutations induced in wildtype and DNA repair-deficient XP cells revealed that the major mutation was base substitutions of which the majority (42 and 38%, respectively) were G:C to T:A transversions. The next major mutation was G:C to A:T and A:T to G:C base substitutions in wildtype and XP cells, respectively. The DNA polymerase stop assay using N-Aco-ABA-treated plasmids as a template showed that most stop signals, i.e., adducted sites, appeared at G:C sites. These results suggest that N-Aco-ABA binds preferably to guanine rather than adenine, and adducted adenine is repaired more efficiently by the nucleotide excision repair. Error-prone DNA polymerases could insert adenine at sites opposite to N-Aco-ABA-adducted guanine, which leads to G:C to T:A transversion. These findings could be very important to evaluate the human lung cancer risk of environmental 3-NBA.

3-Nitrobenzanthrone (3-nitro-7H-benz[d,e]anthracen-7-one, 3-NBA) is a powerful nurtagen and a suspected human carcinogen existing in diesel exhaust and airborne particulates. Recently, one of the major presumed metabolites of 3-NBA, 3-aminobenzanthrone (3-ABA), was detected in human urine samples. Here we analyzed DNA adducts fon-ned in 3-NBA-exposed human hepatoma HepG2 cells by a P-32-postlabeling/thin layer chromatography (TLC) method and a P-32-postlabeling/polyacrylamide gel electrophoresis (PAGE) method. With HepG2 cells exposed to 3-NBA (0.36-36.4 mu M) for 3h, we obtained three spots or bands corresponding to adducted nucleotides. Two were assigned as 2-(2 '-deoxyadenosin-N-6-yl)-3-aminobenzanthrone-3 '-phosphate (dA3 ' p-N-6-C2-ABA) and 2-(2 '-deoxyguanosin-N-2-yl)-3-aminobenzanthrone-3 '-phosphate (dG3 ' p-N-2-C2-ABA), with identical mobilities to those of synthetic standards on PAGE analysis. The chemical structure of the substance corresponding to the other spot or band could not be identified. Quantitative analyses revealed that the major adduct was dA3 ' p-N-6-C2-ABA and its relative adduct labeling (RAL) value at 36.4 mu M of 3-NBA was 200.8 +/- 86.1/10(8) nucleotide. (c) 2007 Elsevier B.V. All rights reserved.

3-Nitrobenzanthrone is a powerful bacterial mutagen and carcinogen to mammals. To obtain precise information on DNA-adduct formation by 3-nitrobenzanthrone, a number of DNA adducts, including N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (13 a), 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone (14 a), N-(2'-deoxyadenosin-8-yl)-3-aminobenzanthrone (15 a), 2-(2'-deoxyadenosin-N6-yl)-3-aminobenzanthrone (16 a), and their N-acetylated counterparts 13 b, 14 b, 15 b, and 16 b were synthesized by palladium-catalyzed aryl amination of the corresponding nucleoside and bromobenzanthrone derivatives. Among these DNA adducts, DNA adducts 13 a, 13 b, 14 a, 14 b, and 16 a were identified in the reaction mixture of nucleosides (2'-deoxyguanosine, 2'-deoxyadenosine, or DNA) with N-acetoxy-3-aminobenzanthrone or N-acetyl-N-acetoxy-3-aminobenzanthrone, both of which are recognized as activated metabolites of 3-nitrobenzanthrone. The formation of these multiple DNA adducts may help explain the potent mutacarcinogenicity of 3-nitrobenzanthrone.

9-(4′-Aminophenyl)-9H-pyrido[3,4-b]indole (aminophenylnorharman, APNH), a novel endogenous mutagenic/ carcinogenic heterocyclic amine, is known to be a reaction product of 9H-pyrido[3,4-b]indole (norharman) and aniline. The major APNH-DNA adduct has been reported to be 2′-deoxyguanosin-8-yl-aminophenylnorharman (dGuo-C8-APNH). However, RNA adducts may also be important. We here demonstrated formation of APNH-RNA adducts and conducted a structural analysis using various spectrometric approaches. When a reaction mixture of an ultimate mutagenic form of APNH, N-acetoxy-APNH, and guanosine (Guo) was subjected to LC-ESI/MS analysis, one peak, with a similar UV spectrum to dGuo-C8-APNH, exhibited a molecular ion peak at m/z 541 along with a fragment peak at m/z 409, consistent with loss of a ribose moiety. From 1H-NMR analysis, its chemical structure was concluded to be N4-(guanosin-8-yl)-9-(4′-aminophenyl)-9H-pyrido[3,4-b]indole (Guo-C8-APNH). The same adduct was yielded in yeast tRNA incubated with N-acetoxy-APNH. Digestion of tRNA treated with N-acetoxy-APNH resulted in the appearance of one adduct spot visualized by the 32P-postlabeling method, corresponding to Guo-C8-APNH. No spot was seen with tRNA alone. Additional analysis of in vivo adduct formation in the livers of rats administered APNH at a concentration of 100 mg/kg revealed that several adduct spots, including one corresponded to Guo-C8-APNH, were observed. The total adduct levels of APNH-RNA were 28±13.3 (mean±SD) adducts per 106 nucleotides. Comparisons demonstrated six times higher levels of total APNH-RNA than total APNH-DNA adducts in the same rat liver samples. These results indicate that APNH-RNA might be a useful biomarker for exposure to APNH.

Various types of polycyclic aromatic compounds (PACs) in diesel exhaust particles are thought to contribute to carcinogenesis in mammals. Although the carcinogenicity, mutagenicity and tumour-initiating activity of these compounds have been evaluated, their tumour-promoting activity is unclear. In the present study, to determine the tumour-inducing activity of PACs, including previously known mutagenic compounds in atmospheric environments, a transformation assay for promoting activity mediated by the release of contact inhibition was conducted for six polycyclic aromatic hydrocarbons (PAHs), seven oxygenated PAHs (oxy-PAHs) and seven nitrated PAHs (nitro-PAHs) using mouse embryonic fibroblast cells transfected with the v-Ha-ras gene (Bhas 42 cells). Of these, two PAHs [benzo[k]fluoranthene (B[k]FA) and benzo[b]fluoranthene (B[b]FA)], one oxy-PAH [6H-benzo[cd]pyren-6-one (BPO)] and two nitro-PAHs (3-nitro-7H-benz[de]anthracen-7-one and 6-nitrochrysene) were found to exhibit particularly powerful tumour-promoting activity (≥10 foci following exposure to

We previously identified 2-[2-(acetylamino)-4-amino-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA) congeners as major mutagens in water concentrates from several rivers that flow in three different areas, i.e. Kyoto, Aichi, and Fukui Prefectures, in Japan. In synthesis studies, these PBTAs were shown to be formed from corresponding dinitrophenylazo dyes via non-chlorinated derivatives (non-ClPBTAs). However, only non-ClPBTA-1, i.e. 2-[2-(acetylamino)-4-[bis(2-methoxyethyl)amino]-5-methoxyphenyl]-6-amino-4-bromo-2H-benzotriazole, had been detected as a minor contaminant in the Nishitakase River in Kyoto. In this study, analysis of mutagens in water concentrate from the Ho River, which flows through an area with a textile dyeing industry in Shizuoka Prefecture, Japan, allowed the isolation of four compounds (I, II, III, and IV). These four mutagens were identified as 2-[2-(acetylamino)-4-[N-(2-cyanoethyl)ethylamino]-5-methoxyphenyl]-6-amino-4-bromo-2H-benzotriazole (non-ClPBTA-2), 2-[2-(acetylamino)-4-[(2-hydroxyethyl)amino]-5-methoxyphenyl]-6-amino-4-bromo-2H-benzotriazole (non-ClPBTA-3), 2-(2-acetylamino-4-amino-5-methoxyphenyl)-6-amino-4-bromo-2H-benzotriazole (non-ClPBTA-4), and 2-[2-(acetylamino)-4-(diethylamino)-5-methoxyphenyl]-6-amino-4-bromo-2H-benzotriazole (non-ClPBTA-7) by spectral data and co-chromatography using synthesized standards. Non-ClPBTA-3 and -7 were highly mutagenic in Salmonella typhimurium YG1024, inducing 159,000 and 178,000 revertants/microg, respectively, in the presence of S9 mix. Like PBTAs, non-ClPBTAs might have been produced from azo dyes during industrial processes in dyeing factories and released into rivers.

3-Nitrobenzanthrone (3-NBA) is an extremely potent mutagen in diesel exhaust. It is a lung carcinogen to rats, and therefore a suspected carcinogen to human. In order to clarify the mechanism of carcinogenicity of 3-NBA, we investigated oxidative DNA damage by N -hydroxy-3-aminobenzanthrone (N-OH-ABA), a metabolite of 3-NBA, using 32 P-labeled DNA fragments from the human p53 tumor-suppressor gene. N-OH-ABA caused Cu(II)-mediated DNA damage, and endogenous reductant NADH dramatically enhanced this process. Catalase and a Cu(I)-specific chelator decreased DNA damage, suggesting the involvement of hydrogen peroxide (H 2 O 2 ) and Cu(I). N-OH-ABA induced DNA damage at cytosine and guanine residues of ACG sequence complementary to codon 273, a well-known hot spot of the p53 gene. N-OH-ABA dose dependently induced 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) formation in the presence of Cu(II) and NADH. Treatment with N-OH-ABA increased amounts of 8-oxodG in HL-60 cells compared to the H 2 O 2 -resistant clone HP100, supporting the involvement of H 2 O 2 . The present study has demonstrated that the N -hydroxy metabolite of 3-NBA induces oxidative DNA damage through H 2 O 2 in both a cell-free system and cultured human cells. We conclude that oxidative DNA damage may play an important role in the carcinogenic process of 3-NBA in addition to previously reported DNA adduct formation.

A kind of N-nitrosobile acid conjugate, N-nitrosotaurocholic acid (NO-TCA), was incubated with calf thymus DNA, and formation of an adduct was detected by the 32P-postlabeling method under nuclease P1 conditions. To examine the nucleotides containing the adduct from NO-TCA, each of 2'-deoxyribonucleotide 3'-monophosphates (3'-dAp, 3'-dGp, 3'-dCp, or 3'-Tp) was incubated with NO-TCA. The same adduct spot was detected in the reaction of NO-TCA with 3'-dCp. The structure of this adduct was determined to be 3-ethanesulfonic acid-dC by several spectrometry techniques. Moreover, bulky adducts containing bile acid moiety were also produced from the reaction of NO-TCA with 3'-dCp and 3'-dAp. From comparison with spectral data for authentic compounds, these adducts were concluded to be N4-cholyl-dC and N6-cholyl-dA. N4-Cholyl-dC and N6-cholyl-dA were also detected in calf thymus DNA treated with NO-TCA. In addition, 3-ethanesulfonic acid-dC and N4-deoxycholyl-dC were found to be produced from N-nitrosotaurodeoxycholic acid (NO-TDCA) with dC. NO-TCA and NO-TDCA induced mutations in Salmonella typhimurium TA100 but not in TA98. Mutational spectrum analysis revealed that NO-TCA induced G to A transitions predominantly. When NO-TCA (250 mg/kg) was singly administered to male Wistar rats by gavage, both ethanesulfonic acid-dC and N4-cholyl-dC could be detected in the glandular stomach and colon. The levels of ethanesulfonic acid-dC were 0.22-0.29 per 10(6) nucleotides, but values for N4-cholyl-dC were about 500-fold lower. These observations suggest that N-nitroso bile acid conjugates, NO-TCA and NO-TDCA, may induce G to A base substitutions in genes via DNA adduct formation, producing ethanesulfonic acid- and/or (deoxy)cholic acid-DNA and, therefore, may be related to human carcinogenesis as endogenous mutagens.

Pierisin-2 is a cytotoxic and apoptosis-inducing protein present in Pieris brassicae with a 91% homology in the deduced amino acid sequences to pierisin-1 from Pieris rapae. We earlier showed pierisin-1 to catalyze mono(ADP-ribosyl)ation of 2'-deoxyguanosine (dG) in DNA to form N2-(ADP-ribos-1-yl)-2'-deoxyguanosine, this DNA modification appearing linked to its cytotoxicity and ability to induce apoptosis in mammalian cell lines. In this paper, we documented evidence that pierisin-2 also catalyzed ADP-ribosylation of dG in DNA to give the same reaction product as demonstrated for pierisin-1, with similar efficiency. With oligonucleotides as substrates, ADP-ribosylation by pierisin-2 was suggested to occur by one-side attack of the carbon atom at 1 position of the ribose moiety in NAD toward N2 of dG. The presence of a unique ADP-ribosylation toxin targeting dG in DNA in two distinct species in a Pieris genus could be a quite important finding to better understand biological functions of pierisin-1 and -2 in Pieris butterflies and the generic evolution of these cabbage butterflies.

2-[2-(Acetylamino)-4-[bis(2-hydroxyethyl)amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-6) and 4-amino-3,3'-dichloro-5,4'-dinitrobiphenyl (ADDB) are two compounds, which show strong mutagenicity toward bacteria, that have been identified as major mutagens in river water in Japan. In the present study, we examined the genotoxicity of PBTA-6 and ADDB in goldfish (Carassius auratus) by the micronucleus test and single-cell gel electrophoresis (comet assay). The frequencies of micronuclei in gill cells gradually increased until 96h after i.p. injection of PBTA-6 and ADDB at doses of 50mg/kg body weight, and then decreased 144h after injection. PBTA-6 induced micronuclei in gill cells dose-dependently at a dose range of 1-100mg/kg body weight, giving significantly high frequencies at doses of 50 and 100mg/kg body weight. On the other hand, no significant increase was observed in the peripheral erythrocytes of goldfish exposed to PBTA-6 or ADDB. In the comet assay, values of DNA tail moment and tail length in peripheral erythrocytes increased significantly until 6h after the i.p. injection of PBTA-6 (50mg/kg body weight), only to decrease by 9h after injection. Both the DNA tail moment and tail length were dose-dependently increased by injections of PBTA-6 at doses ranging from 1 to 50mg/kg. Significantly high values for tail moment and tail length were found in peripheral erythrocytes 3h after an i.p. injection of ADDB and persisted for up to 6h. These results show that both PBTA-6 and ADDB have genotoxic effects in goldfish.

Synthetic methods for the preparation of 2′-deoxyguanosine-C8 (dG-C8) adducts with several mutagenic and carcinogenic amino- or nitro-arenes were developed using the palladium-mediated cross-coupling reaction of protected 8-amino-dG with bromoarenes in around 80% yields, followed by conventional deprotection procedures. This approach can be applied to preparation of a variety of authentic dG-C8 adducts with amino or nitro-arenes.

To clarify the mutagenic potential of surface soil in the Kinki region of Japan, particularly in Osaka and neighboring cities, 62 surface soil samples were collected and their organic extracts were examined by the Ames/Salmonella assay. All of the samples were mutagenic toward TA98 in both the presence and absence of a mammalian metabolic activation system (S9 mix). While all of the samples showed mutagenicity toward TA100 with S9 mix, only 45/62 (73%) were mutagenic without S9 mix. Fifty (81%) of the samples showed higher activity toward TA98 than TA100. The mean values of the mutagenicities of soil samples collected in Osaka prefecture (n=35) toward TA98 with and without S9 mix were 2315 and 1630 revertants per gram of soil, respectively, and these were 2.9 and 2.6 times as high as the values for samples from other prefectures (n=27), respectively. Three dinitropyrene (DNP) isomers, i.e. 1,3-, 1,6- and 1,8-DNP, and 3-nitrobenzanthrone (NBA) in the surface soil samples were quantified by fluorometric detection of the corresponding amino compounds, i.e. diaminopyrene isomers and 3-aminobenzanthrone, using high-performance liquid chromatography (HPLC). The three DNP isomers were detected in all of the soil samples (n=26) that were mainly collected in Osaka prefecture, and the amounts of 1,3-, 1,6- and 1,8-DNP were 6-1526, 11-1772 and 10-2092pg/g of soil, respectively. The contribution ratios of 1,3-, 1,6- and 1,8-DNP to the mutagenicity of soil extracts toward TA98 without S9 mix were 0.2-12, 0.3-12 and 0.5-27%, respectively. The amount of 3-NBA in soil samples (n=8) was 144-1158pg/g of soil, and the contribution ratio of 3-NBA to the mutagenicity of soil extracts was 2-38%. These results suggest that the surface soils in the Kinki region were highly polluted with mutagens and the pollution levels in Osaka prefecture were higher than those in other areas. DNP isomers and 3-NBA may be major mutagens that contaminate surface soil in this region.

A sensitive method for determining 3-nitrobenzanthrone in surface soil was developed. 3-Nitrobenzanthrone was reduced to 3-aminobenzanthrone by refluxing at 60 degrees C with hydrazine and Raney nickel for 20 min, and 3-aminobenzanthrone was determined by normal-phase high-performance liquid chromatography (HPLC) with fluorescence detection. We used a cyanopropyl stationary phase and an n-hexane-ethyl acetate (3:1, v/v) mobile phase, since 3-aminobenzanthrone exhibits fluorescence in a low-polarity solvent such as n-hexane or ethyl acetate, but not in a polar solvent such as water or methanol. The calibration graph showed good linearity (r2>0.9999) in the range of 0.002-2 ng, and the detection limit was 0.002 ng (S/N=3). 3-Nitrobenzanthrone in extracts from surface soil collected in the Chubu area (central area) of Japan was determined after clean-up using silica gel chromatography and high-performance liquid chromatography on a pyrenylethyl stationary phase. The concentration of 3-nitrobenzanthrone in surface soil was determined in the range of 1.2-1020 pg/g soil.

We have synthesized several nitrobenzanthrones (NBAs) and investigated their structures in solution using NMR spectroscopy. In our study, however, low solubility of NBAs in organic solvents always became a serious problem and led to NMR spectra with low signal-to-noise ratios. To solve this problem, we adopted a new method of conventional coherence transfer pathway selection using pulsed field-gradients. The double-pulsed field-gradient spin echo (DPFGSE) sequence was used for selecting natural-abundance carbon-13 isotopomers by using a bilinear rotation decoupling (BIRD) sequence and a so-called gradient-BIRD pulse for the excitation sculpting technique. We performed NMR measurements on 3,9-dinitro-7 H -benz[ d,e ]anthracene-7-one (compound 1), 3,9,11-trinitro-7 H -benz[ d,e ]anthracene-7-one (compound 2), and 2-nitro-7 H -benz[ d,e ]anthracene-7-one (compound 3) by this method and obtained spectra of high quality. Combining the results from phase-sensitive 2D NOESY, HOHAHA, and DPFGSE-HMQC, DPFGSE-HMQC ...

The present study investigated the time-course changes of concentration of chloroform (CHCl3) in the blood during and after exposure of male rats to CHCl3 by inhalation. Increasing the dose of CHCl3 in the inhalation exposed groups caused a commensurate increase in the concentration of CHCl3 in the blood and the area under the blood concentration-time curve (AUC). There was good correlation (r = 0.988) between the inhalation dose and the AUC/kg body weight. Based on the AUC/kg body weight-inhalation dose curve and the AUC/kg body weight after oral administration, inhalation equivalent doses of orally administered CHCl3 were calculated. Calculation of inhalation equivalent doses allows the body burden due to CHCl3 by inhalation exposure and oral exposure to be directly compared. This type of comparison facilitates risk assessment in humans exposed to CHCl3 by different routes. Our results indicate that when calculating inhalation equivalent doses of CHCl3, it is critical to include the AUC from the exposure period in addition to the AUC after the end of the exposure period. Thus, studies which measure the concentration of volatile organic compounds in the blood during the inhalation exposure period are crucial. The data reported here makes an important contribution to the physiologically based pharmacokinetic (PBPK) database of CHCl3 in rodents.

Poly (ADP-ribose) chain (PAR) formed by poly (ADP-ribose) polymerase (PARP) is catabolized mainly by poly (ADP-ribose) glycohydrolase (PARG). PARG is emerging as a therapeutic target for cancer, because its inhibition leads to cell death in some kinds of cancer cell lines. In order to obtain small molecules that effectively inhibit PARG protein, an in-house collection of ∼10,000 small molecules were screened for their ability to accumulate the PAR in A549 cells at 5 μM. We identified ∼100 hit compounds. Among them, MO2282 and MO2455 induced the most significant accumulation of PAR. MO2455 is an analogue of MO2282 with improved water-solubility. MO2282 and MO2455 were evaluated in vitro for their ability to inhibit the catalytic activity of PARG. MO2282 and MO2455 showed modest inhibition activities against recombinant rat PARG. They also inhibited the growth of various kinds of cancel cell lines in vitro at an IC50 value of 0.05 - 3.0 μM and showed different spectrum of antitumor activity from conventional anticancer drugs, CDDP, ADM, PTX, and CPT-11. Next, we investigated the growth-inhibitory effect of MO2455 on A549 cells in a xenotransplanted model. A significant anti-tumor activity was observed in mice when treated with MO2455 at doses of 25 mg/kg every two days. Although treatment-related body weight loss was observed in mice treated with MO2455, body weight recovered by day 8. In conclusion, the present data suggest that MO2455 has potential as a cancer drug with different mechanisms of action from conventional anti-cancer drugs. Citation Format: Tatsu Shimoyama, Takeshi Sawada, Mari Akimoto, Yuka Sasaki, Hiroaki Fujimori, Yoshinobu Ishikawa, Tadashi Okawara, Tetsumi Irie, Takeji Takamura, Kenji Matsuno, Kengo Inoue, Mitsuko Masutani, Fumiaki Koizumi. Identification of a novel compound, MO2455, that induces poly(ADP-ribose) (PAR) accumulation and inhibits the growth of cancer cells in vitro and in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4808.

Six compounds known to be photo-genotoxic were assayed with the photo-irradiated 96-well umu test system using the original Salmonella strain TA1535/pSK1002 as well as the newly developed strains NM8001 and NM8021. The latter two strains were obtained by introducing the pSK1002 plasmid into strains YG3001 and YG3021. These strains are highly sensitive to oxidative DNA damage owing to the deletion of the nucleotide excision repair enzyme uvrB and the base excision repair enzyme mutY and the nucleotide excision repair enzyme uvrB and the base excision repair enzymes mutY and mutM, respectively. Among the compounds tested under UVA irradiation, methylene blue, neutral red and dichlorobenzidine showed only a slight induction of β-galactosidase activity, whereas 8-methoxypsoralen, chloropromazine and 9,10-dimethylbenzanthracene showed a significant increase in the relative LacZ level as an indicator of genotoxicity. The activity of NM8001 induced by the photo-genotoxins was quite similar to that of NM8021, which indicated that the deficiency of mutY did not affect detection of the selected photo-genotoxins. With NM8001, under UVA light, riboflavin was able to induce the SOS response in bacterial cells. Moreover, neutral red was also found to exert photo-genotoxicity under fluorescent light. Phenalenone, a known atmospheric contaminant present in large amounts, showed positive response with NM8001 under UVA. These results indicate that the photo-irradiated 96-well version of the umu test can be used for rapid screening of the photo-genotoxicity of compounds.

BODIPY-modified 2′-deoxyguanosine was synthesized for use as a detection reagent for genotoxic compounds. BODIPY-FL is a well known fluorescence reagent whose fluorescent light emission diminishes near a guanine base by a photo-induced electron transfer process. We attached BODIPY-Fl to the 5′ position of the deoxyribose moiety of 2′-deoxyguanosine. Although this compound has low fluorescence activity, when depurination by the action of alkylating reagents and dG oxidation by singlet oxygen occurred, the emission of strong fluorescence was observed. BODIPY-dG was found, therefore, to be a very useful tool for selectively detecting DNA damaging activity particularly in natural environmental extracts.

Global hypomethylation and regional hypermethylation are supposed to be hallmarks of cancer cells. During gastric carcinogenesis, in which Helicobacter pylori infection is causally involved, aberrant hypermethylation is already present in H. pylori-infected gastric mucosae. In contrast, little is known about global hypomethylation, which can be caused by hypomethylation of individual repetitive elements and other sequences. We, therefore, investigated hypomethylation of individual repetitive elements and the global 5-methylcytosine content in four groups of gastric mucosal samples that represented the time course of H. pylori infection and gastric carcinogenesis [gastric mucosae of H. pylori-negative healthy volunteers (G1, n = 34), H. pylori-positive healthy volunteers (G2, n = 42), H. pylori-positive gastric cancer patients (G3, n = 34) and H. pylori-negative gastric cancer patients (G4, n = 20)] and 52 primary gastric cancers. Major variants of Alu, LINE1 and Satα were identified, and their methylation levels were quantified by bisulfite pyrosequencing. Compared with G1, the Alu methylation level was decreased in G2, G3, G4 and cancers (89.2-97.1% of that in G1, p < 0.05). The Satα methylation level was decreased in G2 (91.6%, p < 0.05) and G3 (94.3%, p = 0.08) but not in G4 and cancers. The LINE1 methylation level was decreased only in cancers. The 5-methylcytosine content was at similar levels in G2, G3 and G4 and highly variable in cancers. These results showed that Alu and Satα hypomethylation is induced in gastric mucosae by H. pylori infection during gastric carcinogenesis, possibly in different target cells, and that global hypomethylation is not always present in human gastric cancers.

The aromatic nitroketone 3-nitrobenzanthrone (3-nitro-7H-benz[de]anthracen-7-one; 3-NBA) is an extremely potent mutagen and a suspected human carcinogen detected in the exhaust of diesel engines and in airborne particulate matter. 3-NBA is metabolically activated via reduction of the nitro group to the hydroxylamine (N-OH-3-ABA) to form covalent DNA adducts. Thus far, the detection and quantification of covalent 3-NBA-DNA adducts has relied solely on (32)P-postlabeling methodologies. In order to expand the range of available techniques for the detection and improved quantification of 3-NBA-DNA adducts, we have developed a method based upon online column-switching HPLC coupled to electrospray tandem mass spectrometry, with isotopic dilution of (15)N-labeled internal standards. This methodology was applied to the determination of three 3-NBA-derived adducts: 2-(2'-deoxyguanosin-N(2)-yl)-3-aminobenzanthrone (dG-N(2)-3-ABA), N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG-C8-N-3-ABA) and 2-(2'-deoxyguanosine-8-yl)-3-aminobenzanthrone (dG-C8-C2-3-ABA). Dose-dependent increases were observed for all three adducts when salmon testis DNA was reacted with N-acetoxy-3-aminobenzanthrone (N-AcO-3-ABA). dG-C8-C2-3-ABA was detected at much lower levels (overall 1%) than the other two adducts. DNA samples isolated from tissues of rats treated either intratracheally with 3-NBA or intraperitoneally with N-OH-3-ABA were analyzed by mass spectrometry, and the results compared to those obtained by (32)P-postlabeling. The method required 50 microg of hydrolyzed animal DNA on column and the limit of detection was 2.0 fmol for each adduct. dG-C8-C2-3-ABA was not observed in any of the samples providing confirmation that it is not formed in vivo. Linear regression analysis of the levels of dG-N(2)-3-ABA and dG-C8-N-3-ABA in the rat DNA showed a reasonable correlation between the two methods (R(2) = 0.88 and 0.93, respectively). In summary, the mass spectrometric method is a faster, more automated analytical approach that also provides structural confirmation of the adducts detected by (32)P-postlabeling, and it has sufficient sensitivity and precision to analyze DNA adducts in animals exposed to 3-NBA or its hydroxylamine metabolite. The authors acknowledge financial support from Cancer Research UK and from the European Union Network of Excellence ECNIS (Environmental Cancer Risk, Nutrition and Individual Susceptibility, www.ecnis.org, Contract No. FOOD-CT-2005-513943), and from the Medical Research Council (Grant No. G0100873).

3-Nitrobenzanthrone (3-NBA), a genotoxic mutagen found in diesel exhaust and ambient air pollution and its active metabolite N-hydroxy-3-aminobenzanthrone (N-OH-3-ABA) were tested for initiating and complete carcinogenic activity in the NMRI mouse skin carcinogenesis model. Both compounds were found to be inactive as either tumour initiators or complete carcinogens in mouse skin over a dose range of 25-400nmol. Topical application of 3-NBA and N-OH-3-ABA produced DNA adduct patterns in epidermis, detected by (32)P-postlabelling, similar to those found previously in other organs of rats and mice. 24h after a single treatment of 100nmol DNA adduct levels produced by 3-NBA (18+/-4 adducts/10(8) nucleotides) were 6 times lower than those by 7,12-dimethylbenz[a]anthracene (DMBA; 114+/-37 adducts/10(8) nucleotides). In contrast, identical treatment with N-OH-3-ABA resulted in adduct levels in the same range as with DMBA (136+/-25 adducts/10(8) nucleotides), indicating that initial DNA adduct levels do not parallel tumour initiating activity. When compounds were tested for tumour initiating activity by a single treatment followed by twice-weekly applications of TPA, DNA adducts formed by DMBA, but not by 3-NBA or N-OH-3-ABA, were still detectable 40weeks after treatment. When tested for activity as complete carcinogens by twice-weekly topical application, 3-NBA and N-OH-3-ABA produced identical DNA adduct profiles in mouse skin, with adducts still detectable after 40weeks. Only 3-NBA produced detectable adducts in other organs. The authors acknowledge the excellent technical assistance by Brigitte Steinbauer, German Cancer Research Center, Heidelberg. The study was supported by Cancer Research UK. H.H.S., V.M.A. and D.H.P. are members of ECNIS (Environmental Cancer Risk, Nutrition and Individual Susceptibility), a network of excellence operating within the European Union 6th Framework Program, Priority 5: “Food Quality and Safety” (Contract No. 513943).

To clarify the formation of mutagens in the Maillard reaction of glucose and amino acids, 20 amino acids were separately incubated with glucose in the presence or absence of hydroxyl radicals produced by the Fenton reaction. After 1 week at 37 degrees C and pH 7.4, the reaction mixtures of glucose and tryptophan with and without the Fenton reagent showed mutagenicity toward Salmonella typhimurium YG1024 in the presence of a mammalian metabolic system (S9 mix). To identify mutagens in the reaction mixture, blue rayon-adsorbed material from a mixture of glucose, tryptophan, and the Fenton reagent was separated by column chromatography using various solid and mobile phases, and one mutagen, which accounted for 18% of the total mutagenicity of the reaction mixture, was isolated. The chemical structure of the mutagen was determined to be 5-amino-6-hydroxy-8H-benzo[6,7]azepino[5,4,3-de]quinolin-7-one (ABAQ) on the basis of ESI mass, high-resolution APCI mass, (1)H NMR, (13)C NMR, and IR spectral analyses and chemical synthesis of the mutagen. The novel aromatic amine showed high mutagenicity toward S. typhimurium TA98 and YG1024 with S9 mix, inducing 857 revertants of TA98 and 6007 revertants of YG1024/microg, respectively. The mutagenicity of ABAQ was comparable to that of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, which is a mutagenic and carcinogenic hetrocyclic amine in cooked meat and fish formed through the Maillard reaction at high temperature.