Inhibitors Of Mutagenesis Research Articles

Abstract 4876: Effects of a combination of resveratrol and sulforaphane on mutagenesis and DNA adduct formation in rat mammary tissue and a rat mammary fibroblast cell line.

Abstract In this study we investigated the effects of the combination sulforaphane (Sul) and resveratrol (Rev) on carcinogen metabolism to DNA adducts in rat mammary fibroblasts, and on DMBA-induced mutagenesis in mammary tissue from rats treated in vivo. The use of combinations of potential cancer chemopreventive agents has become one strategy to optimize chemoprevention. By targeting more than one pathway/process it may be possible to impact prevention by additive or synergistic effects, and utilize lower doses of agents that might have toxic effects at higher doses. We have previously tested a number of potential inhibitors of mutagenesis induced by the rat mammary carcinogen, 7,12-dimethylbenzanthrace (DMBA) in rat mammary epithelial and fibroblast cell lines (isolated by Dr. P.D. Josephy from lacI rats, Mutat Res, 497: 39-47, 2001). We had compared binary combinations of the agents, sulforaphane (Sul), resveratrol (Res), lipoic acid, epigallocatechin gallate, a vitamin C and E mix, and N-acetylcysteine. The agents alone had minor effects, but the combination of Sul and Res inhibited mutagenesis by about 40%. The current study extended this finding. In the metabolism study, HPLC of metabolites was employed; benzo(a)pyrene (BaP), rather than DMBA was used as the carcinogen, as standards of BaP metabolites, but not those of DMBA were available. BaP like DMBA is a carcinogenic polycyclic aromatic hydrocarbon. Fibroblasts were used, as these metabolized BaP much more effectively than epithelial cells. In the presence of 4uM BaP, in the absence of inhibitors, the cells generated 498 ± 83 pg/ml medium of the BaP-7,8 dihydrodiol -9,10 epoxide decomposition product, BaP 7,8,9,10 tetrol. This was reduced by 0.18uM Sul to 153 ± 48, by 4uM Res to 416 ± 87 and by a combination of the agents to 83 ± 37 pg/ml. The reduction was significant for Sul and for the combination. For the in vivo study rats were treated (6/group) by gavage with a single dose of 80 mg/kg DMBA. Two weeks before the DMBA treatment and continuing for 4 wks, rats received 50 mg/L Res, 120 mg/L Sul, and combinations of the agents at 50 and 120 mg/L or ½ the doses in drinking water. Eight wks after the DMBA treatment the rats were euthanized and mutagenesis in the cII gene was measured. The treatments and mutant fractions resp. were: DMBA alone, 9.1 ± 5.0; DMBA + Res, 8.9 ± 3.4; Sul, 8.2 ± 2.0; Res + Sul, 7.1 ± 2.8; Res + Sul, ½ dose, 7.9 ± 3.4; control, 1.3 ± 1.0. DMBA-induced mutagenesis was inhibited by both combination treatments, and Sul alone, although the inhibitions did not reach statistical significance, possibly because of large inter-animal variations. Taken together the results support the use of combinations of agents to enhance chemoprotection. Supported by the Susan Komen Foundation grant # KG080836. Citation Format: Peter G. Sacks, Wieslawa Kosinska, Mitaliben Contractor, Tian-Zhen Han, Joseph B. Guttenplan. Effects of a combination of resveratrol and sulforaphane on mutagenesis and DNA adduct formation in rat mammary tissue and a rat mammary fibroblast cell line. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4876. doi:10.1158/1538-7445.AM2013-4876

Effects of potential dietary inhibitors of endogenous DNA damage on mutagenesis and lipid peroxidation in lacZ mice

The effects of a nine month administration of dietary: (1) 3H-1,2-dithiole-3-thione (D3T), (2) N-acetylcysteine (NAC), (3) antioxidant vitamin mix, (vitamin C+E), (4) free radical scavenger, amifostine, and (5) calorie restriction, (CR), on mutagenesis and lipid peroxidation in lung, kidney, spleen and liver of lacZ transgenic mice were examined. These agents/diets were chosen because they might inhibit certain proposed mechanisms of endogenous damage to DNA. The agents were added to a high fat, reduced antioxidant AIN-76 diet, to better approximate a Western style diet than the conventional AIN-76 diet. As the lacZ gene is not expressed, mutations in that gene are neutral, and simply accumulate over time. The mutant fractions in control mice increased about 50-100%. Most of the agents inhibited to various extents the age-related increase in mutagenesis in lung, kidney, and/or spleen, but no inhibition was observed in liver. There was no significant effect of age on lipid peroxidation levels in controls, possibly reflecting steady state turnover of lipid peroxidation products. Almost all of the treatments except D3T inhibited lipid peroxidation in most organs to different degrees. The vitamin C+E mix was the most effective at inhibiting lipid peroxidation, but a single most effective inhibitor of mutagenesis could not be discerned. Some associations were observed between the reduction in lipid peroxidation and the inhibition of mutagenesis. The results are consistent with a partial role for oxidative stress in the age-related increase in mutagenesis. These observations may have implications for chemoprevention of carcinogenesis.

Plant phenolic metabolites as the free radical scavengers and mutagenesis inhibitors

Plant secondary metabolites are involved in versatile functions on different levels in the plant organism. One of the roles is the scavenging of free radicals and the protection against excess oxidation caused by UV irradiation, chemical oxidants or pathogen attack or other kinds of stress. Involved are phenolic compounds from different classes such as numerous phenol carboxylic acids, hydroxylated flavonoids such as flavones, flavonols, leucocyanidins, anthocyanins and procyanidins as well as isoflavonoids. Many of these substances have been isolated from plant species possessing valuable and intensively studied medicinal properties. For assessment of the free radical scavenging and antioxidant capacity of phenolic complexes in plants the chemical in vitro (cell free) tests can be used for their relative simplicity and sometimes reasonable cost. Here, we describe the application of several antioxidant and anti-free radical spectrophotometric assays for testing the antioxidant abilities of some rarely studied plant species containing different classes of polyphenols. In addition, the antimutagenic bacterial assays were used to examine the in vivo genoprotective activity of these compounds against chemical mutagens. Among the investigated compounds there are lipophilic flavones and their glucuronides from Scutellaria baicalensis and Iridaceae-type isoflavonoids from Belamcanda chinensis. Phenolic acids, procyanidins and flavonols containing Lamiaceae species such as Leonurus sp, Lamium sp., Stachys officinalis, Marrubium vulgare, Galeopsis speciosa have been also studied to comprise wider spectrum of different types of polyphenolics. The assays used address the different aspects of antioxidant properties such as: free radical scavenging in aqueous and non-aqueous environment (ABTS and DPPH colorimetric tests), scavenging of enzymatically generated superoxide anion radical, transition metal reduction ability by phosphomolybdenum complex formation [2], protection against hydroxyl radical induced polyunsaturated lipid peroxidation in the Fenton reaction system. It is important to employ several antioxidant assays for each object as there are usually different mechanisms of the antioxidation involved that results in varying outcome depending on the test used. For example the polyphenolic mixture from Stachys officinalis showed the weakest potential in the DPPH discoloration test whereas was the strongest one in molybdate reduction assay what clearly indicates the complexity of the involved mechanisms. The antimutagenic activity of the extracted phenol complexes and isolated compounds correlates with free radical scavenging. In the Ames bacterial assays [1] the direct mutagenesis by chemical mutagens can be distinguished from the mutagenesis induced by activation of pro-mutagen with cytochrome P-450 enzymatic fractions. The aglycones were clearly more efficient than glycosides in inhibition of mutagenesis, the lipophilic flavone from Scutellaria baicalensis – baicalein being the most efficient. Other flavonoids were effective in inhibition of indirect mutagenesis that can be attributed to the inhibitory action against the pro-mutagen activating enzymes [3]. Free radical scavenging by the low molecular weight compounds can play an important role as the last line of defense against oxidative damage of the cells for they are more stable than enzymatic antioxidant apparatus and can be easily accumulated in stress conditions (e.g deposited in the cell wall or the vacuole). Superoxide scavenging can protect the cells against the production of deleterious peroxynitrite upon reaction of the relatively harmless superoxide with an important signaling molecule – nitric oxide. The activity of complex extracts is sometimes stronger than individual compounds, which can be interpreted as the necessity for preserving the native composition, more effective when acting in oxidation/reduction cascades and thereby able to reduce the formation of harmful oxidation end-products. The in planta function of the antioxidant and antigenotoxic compounds should be further explored in order to obtain the complete insight into their role in protecting the plant cell.

Antimutagenic effects of extracts from sage (Salvia officinalis) in mammalian system in vivo.

Naturally occurring antimutagenic factors, especially those of plant origin, have recently become a subject of intensive research. Antimutagenic properties of terpenoid fractions of sage (Salvia officinalis) were tested in mammalian system in vivo through examining the ability of sage to decrease the frequency of aberrant cells induced by a potent mutagen. First, groups of mice were treated with three concentrations of sage alone and it was established that the frequency of aberrant cells after treatment with a concentration of 25 microL/kg was not significantly different from the negative control (olive oil), while that found after treatment with the 50 microL/kg concentration differed significantly (chi2(1) = 4.05, p < 0.05). Sage used at a concentration of 100 microL/kg was cytotoxic. Mitomycin C (MMC), known as a potent mutagen, was used for induction of chromosome aberrations. Post-treatment with sage suppressed the effects of MMC significantly. Both concentrations (25 microL/kg and 50 microL/kg) produced a significant decrease in the frequency of aberrations relative to MMC (chi2(1) = 5.42, p < 0.02, chi2(1) = 14.93, p < 0.001, respectively). The percent of aberrations decreased with increasing concentrations of sage. Only nontoxic concentrations of sage without mutagenic effects can be recommended for use as inhibitors of mutagenesis or carcinogenesis.

Antimutagenic profile of three antioxidants in the Ames assay and the Drosophila wing spot test

Antimutagens and anticarcinogens are known to play an important role in combating the action of factors involved in the etiology of cancer. It is expected that inhibitors of mutagenesis also act as inhibitors of carcinogenesis. In the present study, two short-term genotoxicity assays, namely the Ames assay and the Drosophila wing spot test, have been selected for examining the antimutagenic potential of three antioxidants. For this purpose, a promutagen aflatoxin B 1 (AFB 1) was chosen as a positive mutagen against which antimutagenic potential of α-tocopherol (Vit. E), caffeic acid (CA) and glutathione (GSH) was assessed. Vit. E did not exert any antimutagenic response while CA and GSH were effective in reducing the mutational events induced by AFB 1.

Effects of arsenic on DNA synthesis in human lymphocytes.

Effects of arsenic on DNA synthesis in human lymphocytes were biphasic: Either trivalent (arsenic trioxide and sodium arsenite) or pentavalent (sodium arsenate) arsenic compounds at very low concentrations enhanced DNA synthesis in human lymphocytes stimulated by phytohemagglutinin (PHA), whereas higher concentrations inhibited DNA synthesis. There were differences among individual susceptibilities to arsenic-induced DNA synthesis. Either stimulating or inhibiting effects of trivalent arsenic on DNA synthesis in PHA-stimulated lymphocytes were always stronger than those of pentavalent arsenic. Both trivalent and pentavalent arsenic could be rapidly taken up into the human lymphocytes and immediately stimulate or inhibit DNA synthesis. A possible dual effect of arsenic at very low concentrations as both comutagen and inhibitor of mutagenesis is discussed.

Effects of arsenic on DNA synthesis in human lymphocytes stimulated by phytohemagglutinin.

Effects of arsenic on DNA synthesis in human lymphocytes were biphasic: either trivalent (arsenic trioxide and sodium arsenite) or pentavalent (sodium arsenate) arsenic compounds at very low concentrations enhanced DNA synthesis in human lymphocytes stimulated by phytohemagglutinin (PHA), whereas higher concentrations inhibited DNA synthesis. There were differences among individual susceptibilities to arsenic-induced DNA synthesis. Either stimulating or inhibiting effects of trivalent arsenic on DNA synthesis in PHA-stimulated lymphocytes were always stronger than those of pentavalent arsenic. It was also shown that both trivalent and pentavalent arsenic could be rapidly taken up into the human lymphocytes, and immediately stimulated or inhibited DNA synthesis. A possible dual effect of arsenic at very low concentrations as both comutagen and inhibitor of mutagenesis is discussed.

Mutagens, carcinogens and inhibitors in Chinese foods

Abstract Stomach and esophageal cancers have the highest mortality rate in China. The incidence of these cancers is closely related to diet and nutrition. Many mutagens and carcinogens have been isolated and identified in foods consumed in some high‐rate areas of esophageal and stomach cancers. Upon screening more than 100 different fruits, vegetables, and beverages in China, it is shown that green tea, onion, ginger, eggplant, coriander, banana, and orange skin are strong inhibitors of mutagenesis. Polyphenol components isolated from green tea showed strong antioxidant activity. The green tea antioxidant inhibited backward mutagenicity of AFB1 and BaP in Salmonella typhimurium. It also inhibited gene forward mutation and chromosome aberrations in V79 Chinese hamster cells treated by AFB1 and BaP. When the green tea antioxidant was given to mice with drinking water or topically applied to mouse skin, it inhibited the development of skin papilloma induced by DMBA/TPA. It was found that green tea antioxidan...

Plant phenolics as inhibitors of mutational and precarcinogenic events.

Initiation of chemical carcinogenesis involves the intracellular formation of a highly reactive electrophile that can attack many chemical nucleophiles in the cell, including DNA, a process that seems to be a central mechanism of initiation. Competing chemical nucleophiles in the cell, such as endogenous glutathione, can act as protecting or blocking agents against the attack on DNA. There are chemical substances in our food supply that may act as anticarcinogens or antimutagens by blocking or trapping ultimate carcinogen electrophiles in a nucleophilic chemical reaction, to form innocuous products. A continuous input of these substances could serve as an additional buffer against DNA damage, supplementing the endogenous systems qualitatively and quantitatively. Certain plant phenolics can be effective inhibitors of chemical mutagens and (or) carcinogens. Tetrapyrroles and porphyrins, both plant and animal, can also act as blocking agents. Both plant phenolics and porphyrins are primarily active against aromatic carcinogens as inhibitors of mutagenesis in in vitro systems. Plant phenolics have also demonstrated inhibiting activity against aromatic chemically induced carcinogenesis.

Inhibitors of mutagenesis and their relevance to carcinogenesis: Report by ICPEMC expert group on antimutagens and desmutagens

Inhibitors of mutagenesis and their relevance to carcinogenesis: Report by ICPEMC expert group on antimutagens and desmutagens

Inhibitors of mutagenesis and their relevance to carcinogenesis.

The International Commission for the Protection against Environmental Mutagens and Carcinogens (ICPEMC) is an international forum, founded in 1977, with the aim to provide an unbiased scientific basis for the evaluation of the genetic and carcinogenic effects of exposure to chemicals. The ICPEMC has acted by means of different subgroups to which experts in different fields have been selected. One such subgroup has dealt with inhibitors of mutagenesis and their relevance to carcinogenesis (21).