methylnitronitrosoguanidine and 2-anthramine

The aim of this work is to evaluate vitamins B antimutagenic effect against alkylatings methyl-N-nitro-N-nitrosoguanidine (MNNG), ethyl-N-nitro-N'- nitrosoguanidine (ENNG), frameshift mutagens 2-aminoanthracene (2AA) and 2-acetyl-amino-fluorene (2AF) and ROS-generating antibiotics norfloxacin (NOR) and nalidixic acid (NLX), using the in vitro Ames test. In vivo antimutagenesis studies were performed against urinary mutagens induced by NOR (70 mg/kg) or NLX (100 mg/kg) in CD1 mice. Vitamin B1 was antimutagenic against alkylatings MNNG (P<0.05) or ENNG (P<0.001). In fact as per the results observed during the current study, none of the vitamins reduced mutagenesis caused by frameshift mutagens. All of them reduced mutagenesis of NOR or NLX (P<0.001). In vivo studies showed that vitamins B1 and B6 (10 or 100 mg/kg) reduced urinary mutagens from NOR (P<0.001) or NLX (P<0.02) either free or β-glucoronidase-conjugates. None of the studied samples were toxic for the employed antimutagenic system. Vitamin B12 (4 mg/kg) reduced urinary mutagens of NOR or NLX (P<0.02). Vitamins B inhibited DNA mutations induced by ROS generated by NLX or NOR, both in vitro and in vivo. Vitamin B1is antimutagenic against mutations induced by the alkylating MNNG or ENNG. Based on the observations, employment of vitamins B in vivo can be a promising alternative to reduce genotoxic risk exposure to ROS.

Topics: 2-Acetylaminofluorene; Animals; Anthracenes; Antimutagenic Agents; DNA Damage; Methylnitronitrosoguanidine; Mice; Mice, Inbred Strains; Mutagenicity Tests; Mutagens; Mutation; Norfloxacin; Salmonella typhimurium; Thiamine; Vitamin B 12; Vitamin B 6

Magnolol, a component of the bark of Magnolia obovata, has been reported to possess various biological activities, such as anti-carcinogenicity, anti-promotion activity and anti-oxidative activity. These findings suggest potential for this compound in cancer chemoprevention. Interestingly, there have been no reports to date on the potential anti-mutagenic activity of magnolol, involving inhibition of initiation processes of the primary stage of carcinogenicity. In this study, anti-mutagenic activity of magnolol against mutagenicity induced by direct mutagens [1-nitropyrene (1-NP), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG)] and indirect mutagens [2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2), benzo(a)pyrene (B(a)P), 2-aminoanthracene (2-AA) and 7,12-dimethylbenz[a]anthracene (DMBA)] were investigated using the bacterial mutagenicity test (Ames test). Results show that magnolol strongly inhibits mutagenicity induced by indirect mutagens, but does not affect direct mutagens. To elucidate the mechanism of this effect against indirect mutagens, effect of magnolol on CYP1A1- and CYP1A2-related enzyme activities of ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-demethylase (MROD) were investigated. Magnolol strongly and competitively suppressed these enzyme activities, suggesting it inhibited mutation induced by indirect mutagens through suppression of CYP1A1 and CYP1A2 activity.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Anthracenes; Antimutagenic Agents; Benzo(a)pyrene; Biphenyl Compounds; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Cytochrome P-450 CYP1A2 Inhibitors; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Imidazoles; Kinetics; Lignans; Male; Methylnitronitrosoguanidine; Microsomes, Liver; Molecular Structure; Mutagenicity Tests; Mutagens; Oxidoreductases; Quinoxalines; Rats; Rats, Sprague-Dawley; Salmonella typhimurium

This study presents an evaluation of the SOS/umu-test after introducing an additional dilution and incubation in the post-treatment assay. This treatment reduces the influence of coloured test compounds that otherwise affect the colorimetric determination of the beta-galactosidase activity and the bacterial growth measurement during the testing of complex environmental samples. The post-treatment assay significantly increased the beta-galactosidase activity and consequently the enzyme induction ratios at higher doses of model genotoxins 4-nitroquinoline-N-oxide, N-methyl-N'-nitro-N-nitrosoguanidine, 2-aminoanthracene, benzo(a)pyrene with low or no effect on the sensitivity of the test itself. On the other hand tests of environmental extracts indicated significant increases in sensitivity after additional incubation. 4-Nitroquinoline-N-oxide treatments of bacteria in the test affected cell division and caused filamentous growth. The size of filamentous bacteria and incidence rate of the length categories was positively correlated with the concentrations of genotoxins. Presence of filamentous tester bacteria proved induction of SOS response and genotoxic activity of environment samples in SOS/umu-test.

Topics: 4-Nitroquinoline-1-oxide; Anthracenes; Bacterial Proteins; Benzo(a)pyrene; beta-Galactosidase; Cell Division; DNA-Directed DNA Polymerase; Dose-Response Relationship, Drug; Environmental Pollutants; Escherichia coli Proteins; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutagens; Recombinant Fusion Proteins; Salmonella typhimurium; SOS Response, Genetics

The effect of caffeine on the genotoxicity of several carcinogenic compounds representing various classes of chemicals was investigated in a panel of V79 Chinese hamster cells genetically engineered to express cytochromes P4501A1 and P4501A2 and differing in their expression of N-acetyltransferases. The formation of micronuclei served as genetic endpoint. The results show that caffeine increases the number of micronuclei induced by 2-aminoanthracene several fold in the test cell lines. The lowest concentration of caffeine enhancing 2-aminoanthracene-induced genotoxicity was 100 nM. Caffeine also potentiated the genotoxicity of aflatoxin B1, 2-amino-3-methylimidazo[4,5-f]-quinoline. N-methyl-N-nitro-N-nitrosoguanidine, 1,6-dinitropyrene, and 7,8-diol-benzo[a]pyrene. Overall, caffeine lowered the effective genotoxic concentrations of these agents by a factor of about three. In contrast, the genotoxic effect of 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone is markedly decreased in the presence of caffeine. The results indicate that caffeine may modulate the genotoxicity of chemical carcinogens by different mechanisms.

Topics: Aflatoxin B1; Animals; Anthracenes; Caffeine; Carcinogens, Environmental; Cells, Cultured; Cricetinae; Cricetulus; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Drug Synergism; Fibroblasts; Methylnitronitrosoguanidine; Micronuclei, Chromosome-Defective; Mutagens; Nitrosamines; Pyrenes; Quinolines

The mutational specificities of various chemical mutagens were compared in isogenic E. coli strains with different DNA repair capabilities (wild-type, uvrA, umuC, and uvrA umuC) in a reversion assay employing a set of mutant lacZ genes that can detect two types of transitions, four types of transversions, and five kinds of specific frameshift events. A uvrA derivative was more sensitive than the wild-type strain to 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone for +1G, -1G, -2(C-G), +1A and -1A frameshifts, G.C-->A.T transitions, and G.C-->T.A transversions. In a uvrA background, G.C-->T.A transversions and +1G, +1A, and -1A frameshifts appeared to be umuC-dependent, while G.C-->A.T transitions were not. N-Ethyl-N'-nitro-N-nitrosoguanidine was more mutagenic in a uvrA background for five kinds of frameshifts and G.C-->A.T transitions, but not for G.C-->T.A, A.T-->C.G, and A.T-->G.C base substitutions. A.T-->C.G transversions were totally dependent on umuC gene function. For the investigation of mutational specificities induced by frameshift mutagens, an rfa mutation was additionally introduced. The rfa strain responded to 2-nitrofluorene, which induced primarily -2(C-G) frameshift mutations. In an rfa uvrA background, benzo[a]pyrene induced +1G, -1G, +1A, and -1A frameshifts. 2-Aminoanthracene induced +1G, -1G, and +1A, but not -1A, frameshifts, with -1G frameshifts predominating. Ethidium bromide induced only two types of frameshifts, -1G and +1A. Frameshifts induced by ICR-170 were independent of umuC gene function, while those by induced 1-nitropyrene were partly umuC-dependent.

Topics: Adenosine Triphosphatases; Aminoacridines; Anthracenes; Bacterial Proteins; Benzo(a)pyrene; beta-Galactosidase; DNA Ligases; DNA Repair; DNA-Binding Proteins; DNA-Directed DNA Polymerase; Escherichia coli; Escherichia coli Proteins; Ethidium; Fluorenes; Frameshift Mutation; Furans; Genes, Bacterial; Glycosyltransferases; Lac Operon; Methotrexate; Methylnitronitrosoguanidine; Mutagenesis; Mutagenicity Tests; Mutagens; Nitrogen Mustard Compounds; Point Mutation; Pyrenes; Species Specificity; Suppression, Genetic

Pine cone extract fraction VI (PC-VI) inhibited the mutagenicity of the promutagens tested: the polycyclic aromatic hydrocarbon benzo[a]pyrene (B[a]P) dose-dependently, and the aromatic amines 2-aminoanthracene (AA) and 2-acetylaminofluorene (AAF) at high concentrations. PC-VI had no effect on the mutagenicity of the direct-acting mutagens 2-(2-furyl)-3-(5-nitrofuryl)acrylamide (AF-2) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), but inhibited the mutagenicity of the direct-acting mutagen N-hydroxy 2-acetylaminofluorene (N-OH AAF, proximate mutagen of AAF). The addition of PC-VI to rat hepatic microsomes resulted in a decrease of their enzyme activities, especially NADPH-cytochrome c reductase. By gas-chromatographic analysis of B[a]P or AA contents after incubation of B[a]P or AA and PC-VI and S9 mix, the inhibition of hepatic metabolizing enzymes and the interaction between AA and PC-VI were confirmed. On the other hand, PC-VI had no effect on the DNA repair systems for B[a]P- or AA-induced mutagenesis. We conclude that PC-VI shows indirect antimutagenicity by interfering with cytochrome P-450-dependent bioactivation and by direct interaction with AA and the proximate mutagenic product of AAF.

Topics: 2-Acetylaminofluorene; Animals; Anthracenes; Antimutagenic Agents; Benzo(a)pyrene; In Vitro Techniques; Lignin; Male; Methylnitronitrosoguanidine; Microsomes, Liver; Molecular Weight; Mutagenicity Tests; Plant Extracts; Rats; Rats, Sprague-Dawley

Studies with the arabinose-resistant Salmonella forward mutation assay system were performed to determine the antimutagenic activity of chlorophyllin against the mutagenic activity of aflatoxin B1 (AFB1), 2-aminoanthracene (2AA), benzo[a]pyrene (BaP), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and solvent extracts of coal dust (CD), diesel emission particles (DE), airborne particles (AP), tobacco snuff (TS), black pepper (BP) and red wine (RW). Various concentrations of each chemical and complex mixture extract were assayed for mutagenic activity with and/or without S9 in a preincubation test. One concentration of each chemical and complex mixture extract was then tested with various concentrations of chlorophyllin. Results showed that chlorophyllin, at concentrations of 2.5 mg/plate or less, completely or almost completely inhibited the mutagenicity of 2AA, AFB1, BaP, MNNG and solvent extracts of CD, DE and RW. With concentrations from 1.25 to 5 mg/plate, chlorophyllin inhibited over 50% of the mutagenicity of AP, TS and BP extracts. These results further substantiate the antimutagenic efficacy of chlorophyllin against chemicals and complex mixtures.

Topics: Aflatoxin B1; Aflatoxins; Air Pollutants; Anthracenes; Benzo(a)pyrene; Carcinogens; Chlorophyllides; Coal; DNA; Dose-Response Relationship, Drug; Fossil Fuels; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutation; Plants, Toxic; Salmonella typhimurium; Tobacco, Smokeless; Wine

The in vitro unscheduled DNA synthesis (UDS) assay has been evaluated in rat primary lung cells with known genotoxicants. The autoradiographic method was employed to detect UDS in both alveolar macrophages and primary pulmonary cells. Data of a time course study revealed that a high radioactive labeling of DNA repair was achieved after a 16-h incubation with [3H]thymidine. Coupled with low serum (1%), hydroxyurea at the concentration of 20 mM inhibited regular DNA synthesis in primary lung cells in a satisfactory manner (81-88% inhibition). With this protocol, a dose-related increase in UDS was induced by N-methyl-N'-nitro-N-nitrosoguanidine and 2-aminoanthracene in both rat alveolar macrophages and primary lung cells. The results suggest that primary rat lung cells in culture possess DNA-repair ability and that the UDS assay may be useful for assessing the pulmonary genotoxic effect of chemicals in this cell system.

Topics: Animals; Anthracenes; Autoradiography; DNA; Dose-Response Relationship, Drug; Hydroxyurea; In Vitro Techniques; Lung; Macrophages; Male; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutagens; Rats; Rats, Inbred Strains

Since its development by Dr. Bruce Ames and his colleagues more than a decade ago, the Salmonella/mammalian microsome mutagenicity assay has become a widely accepted tool to assist in the identification of chemicals with mutagenic and carcinogenic potential. Several automated approaches to Salmonella testing have been proposed in recent years but have failed to gain acceptance in the scientific community due to poor performance or lack of demonstrated usefulness. In this paper we report on an automated system that successfully generates dose-response data and, moreover, reduces the labor, materials, and sample mass required to obtain such information. In the standard plate-incorporation assay, dose-response relationships are defined by testing discrete doses of the test agent on a series of agar plates. In contrast, the spiral Salmonella assay generates dose-response data from a continuous concentration gradient on a single agar plate. Upon analysis, each spiral plate yields a dose-response curve consisting of 13 data points that span a concentration range of about 15:1, which is equivalent to 5 two-fold serial dilutions. The performance of the spiral Salmonella assay was compared to that of the conventional plate-incorporation assay using 13 mutagens and 7 nonmutagens selected from a variety of chemical classes. Concordant qualitative responses were obtained for all compounds tested, and comparable dose-response relationships were generated by all mutagens with the exception of sodium azide and cyclophosphamide, which are highly water-soluble and, thus, are unable to maintain a well-defined concentration gradient on a spiral plate due to rapid diffusion. In general, toxicity was expressed at a lower dose in the spiral assay, and the mutagenic potencies (slopes of the dose-response curves) were greater in the spiral assay relative to the plate-incorporation assay. These differences will be discussed, as will the applicability of the spiral plating technique to routine screening and its relevancy to future mutagenesis testing.

Topics: 4-Nitroquinoline-1-oxide; Anthracenes; Biotransformation; Fluorenes; Image Processing, Computer-Assisted; In Vitro Techniques; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutation; Salmonella typhimurium; Time Factors

Topics: 2-Acetylaminofluorene; Acetylcysteine; Animals; Anthracenes; Azides; Benzo(a)pyrene; Biotransformation; Dose-Response Relationship, Drug; Fluorenes; Methylnitronitrosoguanidine; Microsomes, Liver; Mutagenicity Tests; Mutagens; Rats; Salmonella typhimurium; Sodium Azide