Showing papers in "Mutation Research-genetic Toxicology and Environmental Mutagenesis in 1999"
TL;DR: Diet is the major source of human exposure to PAHs, and exposure to nitro-PAHs through food consumption appears to be very low.
Abstract: Polycyclic aromatic hydrocarbons (PAHs), of which benzo[a]pyrene is the most commonly studied and measured, are formed by the incomplete combustion of organic matter. They are widely distributed in the environment and human exposure to them is unavoidable. A number of them, such as benzo[a]pyrene, are carcinogenic and mutagenic, and they are widely believed to make a substantial contribution to the overall burden of cancer in humans. Their presence in the environment is reflected in their presence at detectable levels in many types of uncooked food. In addition, cooking processes can generate PAHs in food. PAHs can also be formed during the curing and processing of raw food prior to cooking. Several studies have been carried out to determine the levels of exposure to PAHs from representative human diets, and the proportion of the overall burden of environmental exposure to PAHs that is attributable to the diet. In most cases, it is concluded that diet is the major source of human exposure to PAHs. The major dietary sources of PAHs are cereals and vegetables, rather than meat, except where there is high consumption of meat cooked over an open flame. More recently, biomonitoring procedures have been developed to assess human exposure to PAHs and these have also indicated that diet is a major source of exposure. Exposure to nitro-PAHs through food consumption appears to be very low.
829 citations
TL;DR: Levels of nitrosamines have been declining during the past three decades, concurrent with a lowering of the nitrite used in food and greater control of exposure of malt to nitrogen oxides in beer making.
Abstract: N-Nitroso compounds were known almost 40 years ago to be present in food treated with sodium nitrite, which made fish meal hepatotoxic to animals through formation of nitrosodimethylamine (NDMA). Since that time, N-nitroso compounds have been shown in animal experiments to be the most broadly acting and the most potent group of carcinogens. The key role of nitrite and nitrogen oxides in forming N-nitroso compounds by interaction with secondary and tertiary amino compounds has led to the examination worldwide of foods for the presence of N-nitroso compounds, which have been found almost exclusively in those foods containing nitrite or which have become exposed to nitrogen oxides. Among these are cured meats, especially bacon-and especially when cooked; concentrations of 100 micrograms kg(-1) have been found or, more usually, near 10 micrograms kg(-1). This would correspond to consumption of 1 microgram of NDMA in a 100-g portion. Much higher concentrations of NDMA (but lower ones of other nitrosamines) have been found in Japanese smoked and cured fish (more than 100 micrograms kg(-1)). Beer is one source of NDMA, in which as much as 70 micrograms l(-1) has been reported in some types of German beer, although usual levels are much lower (10 or 5 micrograms l(-1)); this could mean a considerable intake for a heavy beer drinker of several liters per day. Levels of nitrosamines have been declining during the past three decades, concurrent with a lowering of the nitrite used in food and greater control of exposure of malt to nitrogen oxides in beer making. There have been declines of N-nitroso compound concentrations in many foods during the past two decades. The small amounts of nitrosamines in food are nonetheless significant because of the possibility-even likelihood-that humans are more sensitive to these carcinogens than are laboratory rodents. Although it is probable that alkylnitrosamides (which induce brain tumors in rodents) are present in cured meats and other potentially nitrosated products in spite of much searching, there has been only limited indirect evidence of their presence.
424 citations
TL;DR: Niazimicin was further subjected to in vivo test and found to have potent antitumor promoting activity in the two-stage carcinogenesis in mouse skin using 7,12-dimethylbenz(a)anthracene (DMBA) as initiator and TPA as tumor promoter.
Abstract: In the course of studies on the isolation of bioactive compounds from Philippine plants, the seeds of Moringa oleifera Lam. were examined and from the ethanol extract were isolated the new O-ethyl-4-(alpha-L-rhamnosyloxy)benzyl carbamate (1) together with seven known compounds, 4(alpha-L-rhamnosyloxy)-benzyl isothiocyanate (2), niazimicin (3), niazirin (4), beta-sitosterol (5), glycerol-1-(9-octadecanoate) (6), 3-O-(6'-O-oleoyl-beta-D-glucopyranosyl)-beta-sitosterol (7), and beta-sitosterol-3-O-beta-D-glucopyranoside (8). Four of the isolates (2, 3, 7, and 8), which were obtained in relatively good yields, were tested for their potential antitumor promoting activity using an in vitro assay which tested their inhibitory effects on Epstein-Barr virus-early antigen (EBV-EA) activation in Raji cells induced by the tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). All the tested compounds showed inhibitory activity against EBV-EA activation, with compounds 2, 3 and 8 having shown very significant activities. Based on the in vitro results, niazimicin (3) was further subjected to in vivo test and found to have potent antitumor promoting activity in the two-stage carcinogenesis in mouse skin using 7,12-dimethylbenz(a)anthracene (DMBA) as initiator and TPA as tumor promoter. From these results, niazimicin (3) is proposed to be a potent chemo-preventive agent in chemical carcinogenesis.
361 citations
TL;DR: Methodological questions addressed in this article include the validity of measuring 8-hydroxydeoxyguanosine (8OHdG) in cellular DNA or in urine as a biomarker of DNA damage, the extent of artifact formation during analysis of oxidative DNA damage by gas chromatography-mass spectrometry and the levels of oxidative damage in mitochondrial DNA.
Abstract: Humans are exposed to many carcinogens, but the most significant may be the reactive species derived from metabolism of oxygen and nitrogen. Nitric oxide seems unlikely to damage DNA directly, but nitrous acid produces deamination and peroxynitrite leads to both deamination and nitration. Scavenging of reactive nitrogen species generated in the stomach may be an important role of flavonoids, flavonoids and other plant-derived phenolic compounds. Different reactive oxygen species produce different patterns of damage to DNA bases, e.g., such patterns have been used to implicate hydroxyl radical as the ultimate agent in H 2 O 2 -induced DNA damage. Levels of steady-state DNA damage in vivo are consistent with the concept that such damage is a major contributor to the age-related development of cancer and so such damage can be used as a biomarker to study the effects of diet or dietary supplements on risk of cancer development, provided that reliable assays are available. Methodological questions addressed in this article include the validity of measuring 8-hydroxydeoxyguanosine (8OHdG) in cellular DNA or in urine as a biomarker of DNA damage, the extent of artifact formation during analysis of oxidative DNA damage by gas chromatography-mass spectrometry and the levels of oxidative damage in mitochondrial DNA.
352 citations
TL;DR: It is concluded that while humans face the risk of veno-occlusive disease and childhood cirrhosis PAs are not carcinogenic to humans.
Abstract: Pyrrolizidine alkaloids are the leading plant toxins associated with disease in humans and animals. Upon ingestion, metabolic activation in liver converts the parent compounds into highly reactive electrophiles capable of reacting with cellular macromolecules forming adducts which may initiate acute or chronic toxicity. The pyrrolizidine alkaloids present a serious health risk to human populations that may be exposed to them through contamination of foodstuffs or when plants containing them are consumed as medicinal herbs. Some pyrrolizidine alkaloids (PA) adducts are persistent in animal tissue and the metabolites may be re-released and cause damage long after the initial period of ingestion. PAs are also known to act as teratogens and abortifacients. Chronic ingestion of plants containing PAs has also led to cancer in experimental animals and metabolites of several PAs have been shown to be mutagenic in the Salmonella typhimurium/mammalian microsome system. However, no clinical association has yet been found between human cancer and exposure to PAs. Based on the extensive reports on the outcome of human exposure available in the literature, we conclude that while humans face the risk of veno-occlusive disease and childhood cirrhosis PAs are not carcinogenic to humans.
274 citations
TL;DR: It is suggested that SYBR Green I stain may not intercalate, and if it does, that its presence does not give rise to point mutations at a high frequency, and that it appears to be much less mutagenic than ethidium bromide.
Abstract: SYBR Green I nucleic acid gel stain is an unsymmetrical cyanine dye developed for sensitive detection of nucleic acids in electrophoretic gels. Its mechanism of nucleic acid binding is not known, whereas the most commonly used nucleic acid gel stain, ethidium bromide, is a well-characterized intercalator. We compared the mutagenicity of SYBR Green I stain with that of ethidium bromide in Salmonella/mammalian microsome reverse mutation assays (Ames tests). As expected [J. McCann, E. Choi, E. Yamasaki, B.N. Ames, Proc. Natl. Acad. Sci. USA, 72 (1975) 5135-5139], ethidium bromide showed high revertant frequencies in several frameshift indicator strains (averaging 68-fold higher than vehicle controls in TA98, 80-fold higher in TA1538, 15-fold higher in TA1537, and 4.4-fold higher in TA97a), only in the presence of rat liver extracts (S9). Small increases in revertant frequencies were observed for ethidium bromide in the base-substitution indicator strain TA102 both in the presence and absence of S9 (averaging 2.0- and 1.8-fold higher than vehicle controls, respectively) and in base-substitution indicator strain TA100 in the presence of S9 (averaging 1.6-fold higher than vehicle controls). A small mutagenic effect was detected for SYBR Green I stain in frameshift indicator strain TA98 (averaging 2. 2-fold higher than vehicle controls) only in the absence of S9 and in base-substitution indicator strain TA102, both in the presence and absence of S9 (averaging 2.2- and 2.7-fold higher than vehicle controls, respectively). Thus, SYBR Green I stain is a weak mutagen and appears to be much less mutagenic than ethidium bromide. These results suggest that SYBR Green I stain may not intercalate, and if it does, that its presence does not give rise to point mutations at a high frequency.
164 citations
TL;DR: In attempting to understand the role which dietary metals could play in human carcinogenesis, it was found that the many factors involved and the lack of specific information made it difficult to reach firm conclusions on the hazards of dietary metals.
Abstract: Humans have been in contact with metals almost since the beginning of our existence. In fact, one cannot even think on human evolution without considering the great role played by metals in mankind's development. Metals are common moieties of molecules involved in a wide variety of biological processes, and hence are found in virtually all living organisms. Some metals are essential for human nutrition; others are found as contaminants in foodstuffs. One feature of the normal human diet which is frequently found is the simultaneous presence of both essential and toxic metals. Other factors important in the risk-evaluation analysis of metals are their pharmacokinetics, interactions among them and with other major components of the diet, and, especially, the great differences in the dietary habits of different populations and in the regional distribution of metals. In attempting to understand the role which dietary metals could play in human carcinogenesis, we found that the many factors involved and the lack of specific information made it difficult to reach firm conclusions on the hazards of dietary metals. We hope that this paper will raise the interest of genetic toxicologists in the subject and will consequently facilitate a risk analysis of the carcinogenic potential of dietary metals.
160 citations
TL;DR: The FT assay was more sensitive to the genotoxic effects of energetic compounds than was the V79 test, suggesting that the FT might be a better screening tool for the presence of these explosives.
Abstract: The mutagenicity and toxicity of energetic compounds such as 2,4, 6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), hexahydro-1,3, 5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3, 5,7-tetrazocine (HMX), and of amino/nitro derivatives of toluene were investigated in vitro. Mutagenicity was evaluated with the Salmonella fluctuation test (FT) and the V79 Chinese hamster lung cell mutagenicity assay. Cytotoxicity was evaluated using V79 and TK6 human lymphoblastic cells. For the TK6 and V79 assays, TNB and 2, 4,6-triaminotoluene were more toxic than TNT, whereas RDX and HMX were without effect at their maximal aqueous solubility limits. The primary TNT metabolites (2-amino-4,6-dinitrotoluene, 4-amino-2, 6-dinitrotoluene, 2,4-diamino-6-nitrotoluene and 2, 6-diamino-4-nitrotoluene) were generally less cytotoxic than the parent compound. The FT results indicated that TNB, TNT and all the tested primary TNT metabolites were mutagenic. Except for the cases of 4-amino-2,6-dinitrotoluene and 2,4-diamino-6-nitrotoluene in the TA98 strain, addition of rat liver S9 resulted in either no effect, or decreased activity. None of the tested compounds were mutagenic for the V79 mammalian cells with or without S9 metabolic activation. Thus, the FT assay was more sensitive to the genotoxic effects of energetic compounds than was the V79 test, suggesting that the FT might be a better screening tool for the presence of these explosives. The lack of mutagenicity of pure substances for V79 cells under the conditions used in this study does not preclude that genotoxicity could actually exist in other mammalian cells. In view of earlier reports and this study, mutagenicity testing of environmental samples should be considered as part of the hazard assessment of sites contaminated by TNT and related products.
150 citations
TL;DR: Malathion used as commercial product, i.e., containing malaoxon and isomalathion, can be considered as a genotoxic substance in vitro and can be regarded as a potential mutagen/carcinogen and requires further investigation.
Abstract: Malathion [S-(1,2-dicarboethoxyethyl)O,O-dimethyl phosphorodithioate] is a commonly used organophosphorus insecticide reported to be genotoxic both in vivo and in vitro, but the reports are conflicting. In order to elucidate the genotoxic potency of the main compounds present in commercial preparations of malathion, the DNA-damaging effect of this insecticide, its major metabolite malaoxon [S-(1,2-dicarboethoxyethyl)O,O-dimethyl phosphorothiolate] and its isomer isomalathion [S-(1,2-dicarboethoxyethyl)O,S-dimethyl phosphorodithioate], all at purity of at least 99.8%, was investigated by use of the alkaline single cell gel electrophoresis (comet assay). Freshly isolated human peripheral blood lymphocytes were incubated with 25, 75 and 200 microM of the chemicals for 1 h at 37 degrees C. The concentrations used are comparable to those found in blood following various non-lethal human exposures to pesticides. Malathion did not cause any significant changes in the comet length of the lymphocytes, throughout the range of concentrations tested. Malaoxon and isomalathion introduced damage to DNA in a dose-dependent manner. The effect induced by malaoxon was more pronounced than that caused by isomalathion. Treated cells were able to recover within a 60-min incubation in insecticide-free medium at 37 degrees C except the lymphocytes exposed to malaoxon at 200 microM, which did not show measurable DNA repair. The latter result suggests a considerable cytotoxic effect (cell death) of malaoxon at the highest concentration used. The reported genotoxicity of malathion might, therefore, be a consequence of its metabolic biotransformation to malaoxon or the presence of malaoxon and/or isomalathion as well as other unspecified impurities in commercial formulations of malathion. In this regard, the results of our study clearly indicate that malathion used as commercial product, i.e., containing malaoxon and isomalathion, can be considered as a genotoxic substance in vitro. This means that it may also produce DNA disturbances in vivo, such as DNA breakage at sites of oncogenes or tumor suppressor genes, thus playing a role in the induction of malignancies in individuals exposed to this agent. Therefore, malathion can be regarded as a potential mutagen/carcinogen and requires further investigation.
139 citations
TL;DR: The findings indicate that the modern additives to plastic, i.e., HBCD and PBDEs, as well as the plastic monomer BCPS may have the same effect to human health as DDT and PCBs, in terms of inducing genetic recombination, which is known to provoke a number of diseases, including cancer.
Abstract: In the present study we have examined the effects of brominated flame retardants (BFR) and several other environmental contaminants in two in vitro assays for intragenic recombination at an endogenous locus in mammalian cells. A total ten compounds were investigated, i.e., two technical PCB mixtures (Aroclor 1221 and Aroclor 1254), DDT, PCP, tetrabromobisphenol A (TBBPA), 4,4′-bischlorophenyl sulfone (BCPS), hexabromocyclododecane (HBCD) and the three different polybrominated diphenylethers (PBDEs): 2-bromodiphenylether (MBDE), 3,4-dibromodiphenylether (DBDE) and 2,4,2′,4′-tetrabromodiphenylether (TBDE). In the SPD8 assay system statistically significant increases in recombination frequency were observed with Aroclor 1221, BCPS, DBDE, DDT, HBCD, MBDE and TBDE. In the Sp5 assay system, only DBDE, HBCD and MBDE caused statistically significant increases in recombination frequency. In conclusion, our findings indicate that the modern additives to plastic, i.e., HBCD and PBDEs, as well as the plastic monomer BCPS may have the same effect to human health as DDT and PCBs, in terms of inducing genetic recombination, which is known to provoke a number of diseases, including cancer.
137 citations
TL;DR: The SOS chromotest, using E. coli PQ37, was able to detect correctly most of the Salmonella mutagens and non-mutagens, and for 17 of 20 compounds, the results obtained could be compared to those obtained in the Ames test.
Abstract: Naturally occurring substances were tested for genotoxicity using a modified laboratory protocol of the Escherichia coli PQ37 genotoxicity assay (SOS chromotest) in the presence and in the absence of an exogenous metabolizing system from rat liver S9-mix. Aristolochic acid I, II, the plant extract aristolochic acid and psoralene were genotoxic; cycasine, emodine, monocrotaline and retrorsine were classified as marginal genotoxic in the SOS chromotest in the absence of S9-mix. In the presence of an exogenous metabolizing system from rat liver S9-mix aristolochic acid I, the plant extract, beta-asarone, cycasin, monocrotaline, psoralen and retrorsine showed genotoxic effects; aristolochic acid II marginal genotoxic effects. Arecoline, benzyl acetate, coumarin, isatidine dihydrate, reserpine, safrole, sanguinarine chloride, senecionine, senkirkine, tannin and thiourea revealed no genotoxicity in the SOS chromotest either in the presence or in the absence of an exogenous metabolizing system from rat liver S9-mix. For 17 of 20 compounds, the results obtained in the SOS chromotest could be compared to those obtained in the Ames test. It was found that 12 (70.6%) of these compounds give similar responses in both tests (6 positive and 6 negative responses). The present investigation and those reported earlier, the SOS chromotest, using E. coli PQ37, was able to detect correctly most of the Salmonella mutagens and non-mutagens.
TL;DR: The results have identified the possible genotoxic damage of oncology nurses related to occupational exposure to at least one antineoplastic agent, which is used as a marker for drug handling.
Abstract: In this study, urinary cyclophosphamide (CP) excretion rate, as well as micronuclei (MN) in peripheral lymphocytes and in buccal epithelial cells were determined for 26 nurses handling antineoplastics and 14 referents matched for age and sex. In urine samples of 20 out of 25 exposed nurses CP excretion rate was found in a range of 0.02–9.14 μg CP/24 h. Our results of the analyses of CP in urine demonstrates that when the nurses were handling CP (and other antineoplastic drugs) this particular compound was observed in urine. The mean values (±SD) of MN frequencies (%) in peripheral lymphocytes from the nurses and controls were 0.61 (±0.32) and 0.28 (±0.16), respectively ( p p >0.05). Age, sex and smoking habits have not influenced the parameters analyzed in this study. Handling time of antineoplastics, use of protective equipment and handling frequency of drugs have no effect on urinary and cytogenetic parameters analyzed. No correlation was found between the urinary CP excretion and the cytogenetic findings in nurses. Neither could we find any relationship between two cytogenetic endpoints. Our results have identified the possible genotoxic damage of oncology nurses related to occupational exposure to at least one antineoplastic agent, which is used as a marker for drug handling. As a whole, there is concern that the present handling practices of antineoplastic drugs used in the several hospitals in Ankara will not be sufficient to prevent exposure.
TL;DR: The results indicate that MN rates are increased in greenhouse workers, especially in those involved in pesticide spraying, which contradicts with earlier results on elevated chromosomal aberration rates in GSTM1 null smokers and NAT2 slow subjects.
Abstract: The frequency of micronuclei (MN) in cultured peripheral lymphocytes was used as a biomarker of genotoxic effects in 34 Italian pesticide-exposed greenhouse workers and 33 unexposed referents matched with the exposed workers for age and smoking habits. The possible influence of the genetic polymorphisms of xenobiotic metabolizing enzymes glutathione S -transferase M1 (GSTM1), T1 (GSTT1), and N -acetyltransferase 2 (NAT2) was also evaluated. To restrict the analysis primarily to cells that have divided once in vitro, MN were scored only in cells showing label after a 42-h incubation with bromodeoxyuridine (BrdU), as detected by immunofluorescence (anti-BrdU technique). Two different concentrations of BrdU (0.5 and 1 μg/ml) were compared. Individual frequencies of micronucleated cells (MNCs) obtained with the two concentrations of BrdU significantly correlated with each other ( r =0.55, P P =0.004 at 1 μg/ml BrdU; P =0.052 at 0.5 μg/ml BrdU) was observed in greenhouse workers with a work history of extensive pesticide spraying ( n =17). Increased MNC frequencies were also associated with ageing at 0.5 μg/ml BrdU, with the GSTM1 -positive genotype at both 1 ( P =0.028) and 0.5 ( P =0.056) μg/ml BrdU in all subjects, and with the NAT2 fast acetylator genotype in smokers at 0.5 μg/ml BrdU ( P =0.043). The results indicate that MN rates are increased in greenhouse workers, especially in those involved in pesticide spraying. The GSTM1 positive and NAT2 fast genotypes appear to be associated with elevated MNC frequencies, which contradicts with earlier results on elevated chromosomal aberration rates in GSTM1 null smokers and NAT2 slow subjects.
TL;DR: The understanding of the potent genotoxicity of MCE will help to establish the possible link between water cyanobacteria contamination and high risk of primary liver cancer found in some endemic areas.
Abstract: The water pollution of toxic cyanobacteria (blue-green algae) is a worldwide problem and worsens with industrialization. Microcystins are potent cyclic heptapeptidic hepatotoxins produced mainly by Microcystis aeruginosa, and their hepatotoxicity has been well-documented. In contrast, information on the genotoxic effects of microcystins is relatively scarce. In our present study, the genotoxicity of microcystic cyanobacteria extract (MCE) of a water source in China was studied using Salmonella typhimurium assay (Ames test), comet assay (Single cell gel electrophoresis) and mouse micronucleus test. Results from Ames test indicated that MCE had strong mutagenicity regardless of the presence of S9. Moreover, MCE was able to induce DNA damage in primary cultured rat hepatocytes examined by comet assay. In addition, MCE also enhanced bone marrow micronucleated polychromatic erythrocytes in mice. The analysis of HPLC showed that the main component of MCE was microcystin-LR. The understanding of the potent genotoxicity of MCE will help to establish the possible link between water cyanobacteria contamination and high risk of primary liver cancer found in some endemic areas.
TL;DR: In this paper, the U.S. Environmental Protection Agency's Office of Pesticide Programs (OPP) published data on a group of selected chloroacetanilides and a few related compounds.
Abstract: With this effort, we continue our examination of data on selected pesticide chemicals and their related analogues that have been presented to the U.S. Environmental Protection Agency's (USEPA's) Office of Pesticide Programs (OPP). This report focuses on a group of selected chloroacetanilides and a few related compounds. As part of the registration process for pesticidal chemicals, interested parties (registrants) must submit toxicity information to support the registration including both mutagenicity and carcinogenicity data. Although this information is available to the public via Freedom of Information (FOI) requests to the OPP, publication in the scientific literature allows greater dissemination and examination of the data. For this Special Issue, graphic profiles have been prepared of the mutagenicity and carcinogenicity data available in the submissions to OPP. Also, a discussion is presented about how toxicity data are used to help establish tolerances (limits of pesticide residues in foods). The mutagenicity results submitted by registrants are supplemented by data on these chemicals from the open literature to provide a full perspective of their genetic toxicology. The group of chloroacetanilides reviewed here display a consistent pattern of mutagenic activity, probably mediated via metabolites. This mutagenic activity is a mechanistically plausible factor in the development of tumors seen in experimental animals exposed to this class of chemicals.
TL;DR: The genotoxicity of the pyrethroid lambda-cyhalothrin was studied using the micronucleus test in erythrocytes of Cheirodon interruptus interruptus using a validation of the MN test in fishes for the assessment of genotoxic pollutants.
Abstract: In order to develop experimental models able to detect genotoxic effects of pollutants in aquatic organisms, the genotoxicity of the pyrethroid lambda-cyhalothrin was studied using the micronucleus test in erythrocytes of Cheirodon interruptus interruptus. The frequency of micronuclei was examined in blood smears obtained from fishes exposed in vivo to three different concentrations (0.05; 0.01; 0.001 ug/l) of the compound and sacrificed at nine sampling times (24, 48, 72, 96 h and 8, 12, 15, 19 and 23 days). As a positive control fishes were exposed to 5 mg/l of cyclophosphamide. Results obtained demonstrated the genotoxic effects of the pyrethroid in the experimental model employed. The variation in the micronuclei frequencies in the different sampling times could be related to the blood cell kinetics and the erythrocyte replacement. The results could be considered as a validation of the MN test in fishes for the assessment of genotoxic pollutants.
TL;DR: It is concluded by analogy that the induction of large DNA sequence deletions, like the mutation spectra induced by TEGDMA in V79 cells here, is probably typical for crosslinking agents, including anticancer drugs.
Abstract: Acrylate esters are applied in industrial and consumer products often associated with polymers and resins. The difunctional methacrylate, triethylene glycol dimethacrylate (TEGDMA), is also frequently included in dental composite materials. Recently, mutagenicity testing of the compound revealed the induction of gene mutations at the hprt locus in V79 cell [H. Schweikl, G. Schmalz, K. Rackebrandt, The mutagenic activity of unpolymerized resin monomers in Salmonella typhimurium and V79 cells, Mutat. Res. 415 (1998) 119-130]. In the present study, TEGDMA caused a dose dependent increase of the number of micronuclei in V79 cells. Furthermore, the mutation spectra induced in exon sequences of the hprt gene in HPRT-deficient V79 cell clones were analyzed by the polymerase chain reaction (PCR). No DNA sequence deletions were observed in spontaneously occurring HPRT-deficient cell clones at the molecular level after PCR analysis, indicating that all spontaneous mutations were caused by point mutations. However, TEGDMA treated V79 cell cultures exhibited different mutation spectra. Only one cell clone among a total of 25 contained all exon sequences of the hprt gene. Large DNA sequences were deleted in 24 cell clones. Partial gene deletions occurred in four clones from exon 5 through 9, and exon 1 was not amplified in one cell clone. Exon sequences of the hprt gene were totally deleted in 19 HPRT-deficient clones. The induction of mostly large deletions in the genome of mammalian cells, like the mutation spectra induced by TEGDMA in V79 cells here, is probably typical for crosslinking agents, including anticancer drugs. Identical types of mutations including chromosomal aberrations and the formation of micronuclei in vitro were observed for acrylates and methacrylates tested so far in various mutation assays. Therefore, we conclude by analogy that the induction of large DNA sequence deletions as shown here with the reactive dimethacrylate, triethylene glycol dimethacrylate, is probably common for acrylates and methacrylates.
TL;DR: This review summarises current understanding of the DNA-damaging potential of various substances of endogenous origin, including oxidants, lipid peroxidation products, alkylating agents, estrogens, chlorinating agents, reactive nitrogen species, and certain intermediates of various metabolic pathways.
Abstract: Recent improvements in the ability to detect chemically modified bases in DNA have revealed that not only does the genetic material incur damage by foreign chemicals, but that it also sustains injury by reactive products of normal physiological processes. This review summarises current understanding of the DNA-damaging potential of various substances of endogenous origin, including oxidants, lipid peroxidation products, alkylating agents, estrogens, chlorinating agents, reactive nitrogen species, and certain intermediates of various metabolic pathways. The strengths and weaknesses of the existing database for DNA damage by each class of substance are discussed, as are future strategies for resolving the difficult question of whether endogenous chemicals are significant contributors to spontaneous mutagenesis and cancer development in vivo.
TL;DR: Findings provide further evidence that citrinin requires complex cellular biotransformation to exert mutagenicity.
Abstract: Pigments produced as secondary metabolites by various isolates of moulds belonging to the genus Monascus have been used traditionally as colorants in Oriental food. Modern food industry has rediscovered these moulds as promising source for natural colorants. However, recent studies evidence that one of the secondary metabolites produced by Monascus is identical in structure to the mycotoxin citrinin. Thus, a sensitive HPLC method was developed to analyse these food colorants for contamination with citrinin. The mycotoxin could be detected in all the commercial Monascus samples at concentrations varying between 0.2 to 17.1 microg/g. In addition, the mutagenicity of commercial Monascus samples applying Salmonella-microsome assay and Salmonella-hepatocyte-assay was investigated and compared to the results obtained with citrinin. Citrinin and two Monascus extracts induced a positive dose depending mutagenic response in the Salmonella-hepatocyte-assay applying strain TA-98. However, no mutagenicity could be detected in the Salmonella-microsome assay, neither with nor without S9-mix, for citrinin and Monascus extracts, applying TA-98, TA-100, TA-1535, TA-1538 and TA-97. These findings provide further evidence that citrinin requires complex cellular biotransformation to exert mutagenicity.
TL;DR: Results suggest that common beans, as other legumes, can function as health-promoting foods and the inhibitory effects of the bean extracts and EA against B[a]P mutagenicity were dose-dependent.
Abstract: Polyphenols in fruits, vegetables (e.g., flavonols like quercetin) and tea (e.g., catechins such as epigallocatechin gallate) are good antioxidants with antimutagenic and anticarcinogenic properties. In the present study, the Salmonella typhimurium tester strain YG1024 was used in the plate-incorporation test to examine the antimutagenic effect of phenolic compounds, extracted from common beans ( Phaseolus vulgaris ), on 1-NP and B[ a ]P mutagenicity. Dose–response curves for 1-NP and B[ a ]P were obtained; the number of net revertants/plate at the peak mutagenic dosage were 880 for 1-NP and 490 for B[ a ]P. For the antimutagenicity studies doses of 0.1 μg/plate and 2 μg/plate for 1-NP and B[ a ]P, respectively, were chosen. We obtained a dose–response curve of ellagic acid (EA) against B[ a ]P and 1-NP mutagenicity. To test the bean extract, a dose of 300 μg/plate of EA was chosen as the antimutagenic control. The EA and bean extracts were not toxic to the bacteria at the concentrations tested. The inhibitory effects of the bean extracts and EA against B[ a ]P mutagenicity were dose-dependent. The percentages of inhibition produced against B[ a ]P (2 μg/plate) using 300 μg/plate of EA and for the extracts 500 μg equivalent catechin/plate were 82%, 83%, 81% and 83% for EA, water extract, water/methanol extract and methanol extract, respectively. However, for 1-NP mutagenicity, only the methanolic extract from beans showed an inhibitory effect. These results suggest that common beans, as other legumes, can function as health-promoting foods.
TL;DR: The increased excretion of 8-oxodG in bus drivers from central Copenhagen as compared with drivers from rural/suburban greater Copenhagen suggests that exposure to ambient air pollution causes oxidative damage to DNA.
Abstract: Oxidative damage to DNA could be involved in the increased risk of cancer associated with exposure to polluted urban air, which contains a number of oxidants. CYP1A2 is induced by and metabolizes polyaromatic hydrocarbons (PAH) and aromatic amines and could modify effects of exposure to ambient air pollution. Similarly, DNA repair may be influenced by occupational and other exposures as well as modify the effect of DNA damaging agents. As part of a large investigation of the genotoxic burden to diesel exposed workers in transport sectors we studied oxidative DNA damage in 57 non-smoking bus drivers from the greater Copenhagen area. The drivers were studied on a workday and on a day off work. Comparisons were made between drivers from the central (n=30) and rural/suburban (n=27) areas of Copenhagen. The rate of oxidative DNA damage was estimated from 24 h urinary excretion of 8-oxo-2'-deoxyguanosine (8-oxodG), a repair product of the highly mutagenic oxidation of guanine in DNA or the cellular pool of GTP. CYP1A2 activity was estimated from the urinary excretion of metabolites of dietary caffeine. The DNA repair was estimated by unscheduled DNA synthesis (UDS) in mononuclear cells isolated on the workday. Repeated measures ANOVA and multifactorial ANCOVA with CYP1A2 activity, age and UDS as covariates were used for statistical evaluation. On the workday, the 8-oxodG excretion was 190+/-108 and 146+/-89 pmol/kg 24 h in the bus drivers from central and the suburban/rural areas Copenhagen, respectively (p<0.05). The 8-oxodG excretion was not significantly different between the workday and the day off. CYP1A2 activity was not affected by driving area but was correlated with the 8-oxodG excretion on the workday (r=0.53; p<0.05). UDS was not significantly affected by driving area or correlated with the 8-oxodG excretion. The increased excretion of 8-oxodG in bus drivers from central Copenhagen as compared with drivers from rural/suburban greater Copenhagen suggests that exposure to ambient air pollution causes oxidative damage to DNA. This effect may be modified by the activity of CYP1A2 or a coregulated enzyme.
TL;DR: The alkaline single-cell gel electrophoresis (or Comet) assay was applied to evaluate DNA damage in cryopreserved peripheral blood mononuclear leukocytes from 34 female shoe workers exposed to organic solvents and a group of 19 non-exposed women.
Abstract: The alkaline single-cell gel electrophoresis (or Comet) assay was applied to evaluate DNA damage in cryopreserved peripheral blood mononuclear leukocytes from 34 female shoe workers exposed to organic solvents and a group of 19 non-exposed women We also investigated whether the polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) genes affect individual level of DNA damage possibly induced by the solvent exposure Chemical measurements of workplace air in the two factories studied showed that the workers were exposed to acetone, gasoline, and toluene in both factories and to ethylacetate and diisocyanate in one factory In the exposed workers, the average level of blood hemoglobin was lower and that of urinary hippuric acid higher than in the non-exposed individuals However, the occupational exposure to organic solvents did not affect the Comet values Neither did age, smoking, or the GSTM1 genotype have any effect on the outcome of this assay The low prevalence of the GSTT1-null genotype precluded conclusions on the influence of GSTT1 polymorphism
TL;DR: Administration of sodium selenite 1 h before sodium arsenite reduced the clastogenic effects of the latter significantly and is of significance in protecting against the widespread toxicity observed in human populations exposed to arsenic through drinking water from contaminated deep tubewells in West Bengal and Bangladesh.
Abstract: Interaction between selenium and arsenic has been used to protect against the genotoxic effects of sodium arsenite through dietary intervention by an equivalent amount (1/10 LD50) of sodium selenite. The two salts were administered by gavaging to laboratory bred Swiss albino mice sequentially and in combination. Cytogenetic endpoints, including chromosomal aberrations (CA) and damaged cells (DC) were recorded 24 h after exposure from chromosome spreads in bone marrow cells. Administration of sodium selenite 1 h before sodium arsenite reduced the clastogenic effects of the latter significantly. The protection was less when the salts were given together and negative when arsenite was given before selenite. Histological changes were recorded. Such reduction of arsenic toxicity through dietary intervention by selenium is of significance in protecting against the widespread toxicity observed in human populations exposed to arsenic through drinking water from contaminated deep tubewells in West Bengal and Bangladesh.
TL;DR: The studies indicate the genotoxic potential of endosulfan and the role of the recA gene in the repair of endOSulfan-induced DNA damage and the roles of prophage lambda and umu gene expression in S. typhimurium cells.
Abstract: Endosulfan, an organochlorine pesticide, was subjected to the differential sensitivity assay in repair-deficient and repair-proficient strains of Escherichia coli K12, prophage λ induction assay in WP2s (λ) and mutation induction in E. coli K12. The induction of umu gene expression with endosulfan was studied also in Salmonella typhimurium TA1535/pSK1002 cells. The differential sensitivity assay revealed that the rec A 13 strain was the most sensitive. Endosulfan induced prophage λ in E. coli and umu gene expression in S. typhimurium cells; however, the extent of the effects were low. Endosulfan also induced a dose-dependent increase in forward mutations in E. coli K12 cells from ampicillin sensitivity to ampicillin resistance. Our studies indicate the genotoxic potential of endosulfan and the role of the rec A gene in the repair of endosulfan-induced DNA damage.
TL;DR: The Hep G2/SCGE assay appears to be a suitable approach for investigating DNA damaging potential of chemicals in the human-derived, metabolically competent hepatoma (Hep G2) cells.
Abstract: The purpose of the present study was the development of a protocol for detecting chemically-induced DNA damage, using the alkaline single-cell gel electrophoresis (SCGE) assay with human-derived, metabolically competent hepatoma (Hep G2) cells. Previous studies indicated that Hep G2 cells have retained the activities of certain phase I and phase II enzymes and reflect the metabolism of genotoxins in mammals better than other in vitro models which require addition of exogenous activation mixtures. The optimal trypsin concentration for the removal of the cells from the plates were found to be 0.1%. Dimethylsulfoxide, at concentrations up to 2%, was an appropriate solvent for water-insoluble compounds. To determine the optimal exposure periods for mutagen treatment, the time kinetics of comet formation was investigated with genotoxic chemicals representing various classes of promutagens namely benzo[a]pyrene (B[a]P), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and N-nitrosodimethylamine (NDMA) and with N-nitrosomethylurea (NMU). All compounds caused a statistically significant induction in DNA damage. With the promutagens, comet formation increased gradually as a function of the exposure duration, and reached maximum values between 20-24 h. With NMU, comet induction maximized already after a short exposure (1 h) and remained at a constant level for up to 24 h. Based on these results, the Hep G2/SCGE assay appears to be a suitable approach for investigating DNA damaging potential of chemicals. Further experiments with IQ and B[a]P showed that the assays are highly reproducible. Comparisons of the present results with those from earlier experiments in which other endpoints (induction of sister chromatid exchanges, micronuclei and chromosomal aberrations) were measured in Hep G2 cells, indicated that the sensitivity of the SCGE assays is more or less identical. Since the SCGE assay is less time consuming than other genotoxicity assays we anticipate that it might be a suitable approach to investigate DNA damaging effects of chemicals in the human-derived, metabolically competent cell line.
TL;DR: The potential risks of introducing new food hazards from the applications of genetic engineering are no different from the risks that might be anticipated from genetic manipulation of crops via traditional breeding.
Abstract: The benefits of genetic engineering of crop plants to improve the reliability and quality of the world food supply have been contrasted with public concerns raised about the food safety of the resulting products. Debates have concentrated on the possible unforeseen risks associated with the accumulation of new metabolites in crop plants that may contribute to toxins, allergens and genetic hazards in the human diet. This review examines the various molecular and biochemical mechanisms by which new hazards may appear in foods as a direct consequence of genetic engineering in crop plants. Such hazards may arise from the expression products of the inserted genes, secondary or pleiotropic effects of transgene expression, and random insertional mutagenic effects resulting from transgene integration into plant genomes. However, when traditional plant breeding is evaluated in the same context, these mechanisms are no different from those that have been widely accepted from the past use of new cultivars in agriculture. The risks associated with the introduction of new genes via genetic engineering must be considered alongside the common breeding practice of introgressing large fragments of chromatin from related wild species into crop cultivars. The large proportion of such introgressed DNA involves genes of unknown function linked to the trait of interest such as pest or disease resistance. In this context, the potential risks of introducing new food hazards from the applications of genetic engineering are no different from the risks that might be anticipated from genetic manipulation of crops via traditional breeding. In many respects, the precise manner in which genetic engineering can control the nature and expression of the transferred DNA offers greater confidence for producing the desired outcome compared with traditional breeding.
TL;DR: The data suggest that brain and heart are more severely affected by the monitored age-related DNA lesions than liver, which can be ascribed to certain characteristics of these postmitotic organs, including the low detoxifying capacities, the high oxygen consumption, and the impossibility to replace damaged cells by mitosis.
Abstract: Experimental data suggest a possible role of DNA damage in aging, mainly related to oxidative lesions. With the objective of evaluating DNA lesions as molecular biomarkers of aging, we measured 8-hydroxy-2'-deoxyguanosine (8-OH-dG) and DNA-protein crosslinks (DPXL) levels in different organs of mice aged 12 and 24 months. 8-OH-dG was detected by 32P postlabelling after removing unmodified dG by trifluoracetic acid, which prevented the artificial formation of 8-OH-dG during 32P labelling procedures. Appreciable 8-OH-dG amounts were detected in 12-month-old mice in liver (1.8 +/- 0.7 8-OH-dG/10(5) normal nucleotides), brain (1.6 +/- 0.5) and heart (2.3 +/- 0.5). In 24-month-old mice these values were higher in all examined organs (liver, 2.7 +/- 0.4; brain, 3.6 +/- 1.1; heart, 6.8 +/- 2.2 8-OH-dG/10(5) normal nucleotides). This accounted for a 1.5-fold increase in liver (not significant), 2.3-fold increase in brain (P < 0.01), and 3.0-fold increase in heart (P < 0.001). A similar trend was observed for DPXL levels, which were the 1.8 +/- 0.3%, 1.2 +/- 0.2%, and 2.2 +/- 0.3% of total DNA in liver, brain, and heart of 12-month-old mice and 1.9 +/- 0.4%, 2.0 +/- 0.4%, and 3.4 +/- 0.5% in 24-month-old mice, with ratios of 1.0, 1.7 (P < 0.01), and 1.5 (P < 0.001), respectively. Highly significant correlations between 8-OH-dG and DPXL levels were recorded in brain (r = 0.619, P < 0.001) and heart (r = 0.800, P < 0.0001), but not in liver (r = 0.201, not significant). These data suggest that brain and heart are more severely affected by the monitored age-related DNA lesions than liver, which can be ascribed to certain characteristics of these postmitotic organs, including the low detoxifying capacities, the high oxygen consumption, and the impossibility to replace damaged cells by mitosis. The strong correlation between 8-OH-dG and DPXL supports a possible contribution of oxidative mechanisms to formation of DPXL in those organs, such as brain and heart, which play a primary role in the aging of the whole organism.
TL;DR: Significantly higher levels of damaged DNA was observed in woodworkers who either smoked or did not smoke cigarettes than in smokers and non-smokers from the control group, which could be associated with the occupational exposure to wood dust in the furniture manufacture.
Abstract: The study was aimed at the assessment of genotoxic effects in workers of a wooden furniture manufacture, based on the level of DNA damage in white blood cells (WBC). The alkaline single cell gel electrophoresis assay (known as the comet assay) in individual cells was adapted for detecting damaged DNA in WBC. The level of DNA damage was determined as the percentage of cells with comets. It was assessed in cells before and after incubation in RPMI 1640 medium and CO 2 at 37°C for 1 h to repair DNA breaks. Thirty-five woodworkers and 41 control subjects were studied. In the woodworkers, significantly more cells with DNA damage (21.5%) were observed than in the control persons (9.7%). A slight but significant decrease in the level of DNA damage was found in the WBC of woodworkers after incubation (17.2%). Significantly higher levels of damaged DNA was observed in woodworkers who either smoked (22.1%) or did not smoke cigarettes (20.8%) than in smokers (13.2%) and non-smokers (7.0%) from the control group. After incubation, a slight decrease in the level of DNA damage was found in both smoking and non-smoking woodworkers compared to the respective subjects in the control group. The increased levels of DNA damage observed in the woodworkers could be associated with the occupational exposure to wood dust in the furniture manufacture.
TL;DR: Given the toxic effects of fumonisins in animals and the widespread human exposure, then the development of biomarkers and their application in epidemiological studies should be a priority for research on these toxins.
Abstract: Fumonisins, fungal toxins produced by Fusarium moniliforme, contaminate maize based foods and feeds throughout the world. They cause liver and kidney toxicity in animals in addition to leukoencephalomalacia in horses and pulmonary edema in pigs. Fumonisin B is carcinogenic in rats and mice. Ecological studies have linked consumption of fumonisin 1 contaminated maize with oesophageal cancer in human populations in South Africa and China. This review discusses the potential health risks for people exposed to the fumonisins, and describes how mechanistic studies of toxicity in animal models have allowed the development of putative biomarkers of fumonisin exposure at the individual level. The requirements for an applicable biomarker include sample availability as well as a high specificity and sensitivity for the exposure of interest. Most environmental toxic insults involve complex exposures both to other toxins and to infections; these confounding factors need to be considered in assessing both the validity of the biomarker and the exposure-disease associations. Fumonisins can be detected in the urine of animals in feeding studies but the sensitivity of the current methodology means only highly exposed people could be monitored. Mechanistic studies indicate that ceramide synthase, an enzyme involved in sphingolipid synthesis, is one cellular target for fumonisin toxicity and carcinogenicity, and this disruption to sphingolipid metabolism increases the ratio of two sphingoid precursors, sphinganine and sphingosine. The altered ratio has been observed in tissues, serum and urine for a number of animal models suggesting it as a good candidate marker of fumonisin exposure. Despite development of analytical methods to measure this biomarker there have been no studies to date correlating it to fumonisin intake in people. Given the toxic effects of fumonisins in animals and the widespread human exposure, which has been calculated to reach 440 m gk g y1 body weight day y1 in a population y1. consuming high quantities 460 g day of contaminated maize, then the development of biomarkers and their application in epidemiological studies should be a priority for research on these toxins. q 1999 Elsevier Science B.V. All rights reserved.
TL;DR: It would appear that 8-OHdG levels in leukocytes may not provide a sensitive marker of exposure to tobacco smoking.
Abstract: 8-Hydroxydeoxyguanosine (8-OHdG) has been widely used as a biomarker of oxidative DNA damage in both animal and human studies. However, controversial data exist on the relationship between 8-OHdG formation and age, sex and tobacco smoking in humans, while few or no data are available on other exposures such as environmental tobacco smoke, alcohol, coffee and tea consumption. We investigated the level of 8-OHdG in DNA from peripheral leukocytes among 102 healthy adults living in Brescia province, North Italy, aged 25-45 (mean: 35.2 years), of which 51 were males. 8-OHdG levels expressed as a ratio to total deoxyguanosine (8-OHdG/106 dG) in DNA showed wide interindividual variation, the highest value (63.8) being 6. 2-fold greater than the lowest (10.3). Current smokers showed lower mean 8-OHdG values than subjects who never smoked (29.3 and 34.0, respectively, p<0.05), and an inverse relationship was found between 8-OHdG and lifetime smoking, which was independent of age, sex and body mass index. An inverse relationship was also found with coffee drinking while no association was observed with alcohol and tea consumption, exposure to environmental tobacco smoke and use of vitamins in all subjects, and with use of oral contraceptives in females. The inverse relationship between smoking status and 8-OHdG levels could be explained by the presence of efficient repair processes for the oxidative damage induced by smoking. In this study, the smokers were relatively young (77% were less than 40 years) and only 7% smoked 30 or more cigarettes a day. In conclusion, it would appear that 8-OHdG levels in leukocytes may not provide a sensitive marker of exposure to tobacco smoking.