The pyrogallol related compounds reduce UV-induced mutations in Escherichia coli B/r WP2

Radioprotective effect of epicatechin in cultured human fibroblasts and zebrafish

Radiation-induced normal cell damage limits the delivery of high-dose radiation to targeted cancer. This study investigated the effect of epicatechin (EC), a minor component of green tea extracts, on radiation-induced cellular damage in vitro in primary cultured human fibroblasts and in vivo in a zebrafish model. Cell viability, proliferation and wound-healing efficacy, mitochondrial membrane potential, and reactive oxygen species (ROS) generation as well as changes in the signaling pathway related to apoptosis were investigated in fibroblasts. The therapeutic effects of EC were explored in a zebrafish model. EC increased clonogenic survival and restored the migration ability of the fibroblasts after irradiation. EC inhibited radiation-induced ROS generation, mitochondrial dysfunction and cell death. EC significantly reduced the expression of p-JNK, p-38, and cleaved caspase-3 compared with their significant increase after radiation treatment. EC attenuated the radiation-induced embryotoxicity in a zebrafish model. These results suggest that EC represents an effective means of reducing cellular damage and facilitating wound healing after radiation exposure.

Suppression of UVC-induced cell damage and enhancement of DNA repair by the fermented milk, Kefir

An aqueous extract of Kefir, fermented milk originally produced in the Caucasus mountains, suppressed morphological changes of human melanoma HMV-1 and SK-MEL cells and human normal fibroblastTIG-1 cells caused by UVC-irradiation, suggesting that UV damage can be suppressed by the Kefir extract. The addition of the Kefir extract after UVC-irradiation of HVM-1 cells resulted in a remarkable decrease in intracellular reactive oxygen species (ROS) which had been increased by UVC irradiation. The Kefir extract also stimulated unscheduled DNA synthesis and suppressed UVC-induced apoptosis of HMV-1 cells. A colony formation assay revealed that the Kefir extract rescued HMV-1 cells from cell death caused by UVC irradiation. The Kefir extract, as well as methyl methanethiosulfonate which is known to enhance the nucleotide excision repair (NER) activity, exhibited strong thymine dimer repair-enhancing activity. Epigalocatechin exhibited a weak NER activity but vitamins A, C, and E and catechin showed no NER activity. The thymine dimer repair-enhancing factors in the Kefir extract were heat-stable and assumed to be molecules with a molecular weight of less than 5000. The treatment of HMV-1 cells with the Kefir extract during or before UVC- irradiation also prevented the generation of ROS and thymine dimmer, and suppressed the apoptosis of HMV-1 cells, suggesting that application of Kefir can prevent UV damage.

Delineation of antimutagenic activity of catechin, epicatechin and green tea extract

Tea is consumed worldwide as second largest to water in popularity as a beverage. It has been reported that tea extracts have antibacterial, antiviral, antioxidative, antitumor and antimutagenic activities. The protective effect of green tea has been assumed to be due to the powerful scavenging and antioxidative property of high concentrations of unpolymerised catechins and their gallates. In the present proposal green tea extract (GT), (+)-catechin (C) and (-)-epicatechin (EC) were investigated for their antioxidant activity by different in vitro methods like (i) DPPH assay (ii) superoxide anion scavenging and (iii) hydrogen peroxide scavenging activity. Further these agents were also tested against mutagenesis using the well-standardized Ames microsomal test system. The Ames tester strain Salmonella typhimurium TA102, which readily responds to reactive oxygen species, was used and the antimutagenic activity was evaluated against oxidative mutagens tertiary butyl hydroperoxide (ID50-24.41, 29.63 and 113.23 microg for EC, C and GT, respectively) and hydrogen peroxide (ID50-17.3, 18.4 and 88.1 microg for EC, C and GT, respectively). Ascorbic acid was used as a standard antioxidant in all the experiments. Results indicate that all the three agents possess excellent DPPH free radical scavenging activity (IC50-1.5 microg for EC, 3.45 microg for C and 3.8 microg for GT), good hydrogen peroxide (IC50-11.18 microg for EC, 13.5 microg for C and 11.78 microg for GT) and superoxide anion scavenging (IC50-1.64 microg for EC, 1.74 microg for C and 3.52 microg for GT) activities. Further, they also show antimutagenic activity in the above-mentioned test systems establishing their antioxidant nature to be responsible for such activity. The in vitro antioxidant activity correlates well with the antimutagenic action. (-)-Epicatechin is indicated to be a better agent in comparison to the other two agents (ID50-1.2 times more than C and 5 times more than GT in antimutagenicity studies against t-BOOH and hydrogen peroxide induced mutagenesis). Ascorbic acid however showed a much less activity (ID50-12.1 mg against t-BOOH and 7.2 mg with hydrogen peroxide induced mutagenesis).

The green tea polyphenol, epigallocatechin-3-gallate, protects against the oxidative cellular and genotoxic damage of UVA radiation

A number of biological activities have been ascribed to the major green tea polyphenol epigallocatechin-3-gallate (EGCG) to explain its chemopreventive properties. Its antioxidant properties emerge as a potentially important mode of action. We have examined the effect of EGCG treatment on the damaging oxidative effects of UVA radiation in a human keratinocyte line (HaCaT). Using the ROS-sensitive probes dihydrorhodamine 123 (DHR) and 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA), we detected a reduction in fluorescence in UVA-irradiated (100 kJ/m(2)) cells in the case of the former but not the latter probe after a 24-hr treatment with EGCG (e.g., 14%, [p < 0.05] after 10 microM EGCG). In the absence of UVA, however, both DHR and DCFH detected a pro-oxidant effect of EGCG at the highest concentration used of 50 microM. Measurements of DNA damage in UVA-exposed cells using the single cell gel electrophoresis assay (comet assay) also showed the protective effects of EGCG. A concentration of 10 microM EGCG decreased the level of DNA single strand breaks and alkali-labile sites to 62% of the level observed in non-EGCG, irradiated cells (p < 0.001) with a 5-fold higher concentration producing little further effect. Correspondingly, EGCG ablated the mutagenic effects of UVA (500 kJ/m(2)) reducing an induced hypoxanthine-guanine phosphoribosyl transferase (HPRT) mutant frequency of (3.39 +/- 0.73) x 10(-6) to spontaneous levels (1.09 +/- 0.19) x 10(-6). Despite having an antiproliferative effect in the absence of UVA, EGCG also served to protect against the cytotoxic effects of UVA radiation. Our data demonstrate the ability of EGCG to modify endpoints directly relevant to the carcinogenic process in skin.

Catechins are not major components responsible for anti-genotoxic effects of tea extracts against nitroarenes

The anti-genotoxic properties of tea leaf extracts were examined in a Salmonella umu-test. Seven non-fermented teas (green tea), one semi-fermented tea (oolong tea), two fermented teas (black tea and Chinese pu er tea) and two other teas were examined for their anti-genotoxic abilities and for their catechins contents. This was to study the relationship between catechins contents and anti-genotoxic activity of various tea leaf extracts. All types of tea extracts showed more potent suppressive effects against umu gene expression of the SOS response in Salmonella typhimurium TA1535/pSK 1002 induced by four nitroarenes (1-nitropyrene, 2-nitrofluorene, 3-nitrofluoranthene and a mixture of 1,6- and 1,8-dinitropyrene) rather than 4-NQO, AF-2 and MNNG. The anti-genotoxic effect of 12 tea leaf extracts on 1-NP, 2-NF, 3-NF and DNP decreased in the order: oolong tea (semi-fermented tea)>black tea (fermented tea)>sencha (non-fermented tea, an ordinary grade green tea)>tocyucya (other tea)>Chinese pu er tea (fermented tea). The amount of catechins (EGC, C, EGCG, EC and ECG) in various teas in decreasing order was non-fermented tea>semi-fermented tea>fermented tea>other tea. A remarkable feature was the effectiveness of black tea and Chinese pu er tea in suppressing the genotoxicity induced by nitroarenes, in spite of the fact that these fermented teas do not have high catechins contents. Statistical analysis showed that no significant (P<0.01) correlation was found between the anti-genotoxicity of tea extracts against nitroarenes and the catechins contents in tea leaf extracts. In further experiment, fractionation of sencha extract by HPLC revealed that anti-genotoxicity of the peak fraction corresponding to catechins accounted for <10% of the total anti-genotoxic activity of sencha extract against for 1-nitropyrene. These results suggest that catechins are not major components responsible for the anti-genotoxic effects of tea leaf extracts against direct-acting nitroarenes.

A novel method of measuring hydroxyl radical-scavenging activity of antioxidants using gamma-irradiation

A new method using ESR spin trapping was proposed for measuring the scavenging activity of antioxidants for the hydroxyl (OH) radical. (-)-Epigallocatechin gallate (EGCg) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) were used as the antioxidant and spin trapping agent, respectively. The conventional method using a Fenton reaction had problems associated with the estimation of activity, because the antioxidant disturbs the system for generating OH radical by coordinating on Fe2+ and by consuming H2O2, besides scavenging the spin adduct (DMPO-OH). Intense gamma-irradiation was therefore used to generate OH radicals, and the intensity decrease in DMPO-OH after irradiation was followed to obtain the rate constant for the scavenging of DMPO-OH by EGCg. The intensities were extrapolated to zero time to estimate the quantity of DMPO-OH formed during gamma-irradiation. By using these values, the reaction rate constant between OH radical and EGCg was calculated as a ratio to that of DMPO. It was shown that this method is useful for comparing the OH radical-scavenging activity of various antioxidants.

Spin-trapping study on the hydroxyl radical formed from a tea catechin-Cu(II) system

A spin-trapping method was applied to examine the formation of the hydroxyl (OH) radical from a tea catechin-Cu(II) system to elucidate a previous result that some tea catechin-Cu(II) systems induced DNA scission. Three tea catechins, (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCg) and (-)-epicatechin (EC), were used. The spin-trapping agent, 5,5'-dimethyl-pyrroline-1-oxide (DMPO), was dissolved in a pH 9 phosphate buffer solution, then a catechin and Cu(II) were added in that order, and the ESR spectral change was monitored for one hour. The order of adding the catechin and Cu(II) was then reversed, and the ESR spectral change was again monitored to examine the coordinating activity of each catechin toward the Cu(II) ion and the effect on OH radical generation. The intensity changes of the spin adducts, DMPO-OH, DMPO-CH3 and DMPO-H, were analyzed, the results suggesting that the OH radical generated in the system decomposed DMPO, resulting in the formation of DMPO-CH3 and DMPO-H. The results show that EGC formed a stable complex with Cu(II) and generated the OH radical. EGCg seemed to have this activity, but the OH radical that was generated was scavenged by the gallate group existing in the complex. EC did not show strong coordinating and OH-generating activities. These characteristics of the three catechins are consistent with the results shown for DNA scission.

Mut-Test to detect substances suppressing spontaneous mutation due to oxidative damage

Since it has been considered that suppression of spontaneous mutation in cells is related to suppression of spontaneous carcinogenesis, it is significant to detect substances which suppress spontaneous mutation in bacterial cells such as Escherichia coli and Salmonella typhimurium in the environment. However, since the frequency of spontaneous mutation in bacteria is usually very low, generally 10(-8)-10(-10),it is difficult to determine significant suppressive ability of such substances on spontaneous mutation. A new method, Mut-Test, was developed by us, applying Luria & Delbruck fluctuation test, to detect substances which suppress spontaneous mutation using E. coli mutT mutant in which spontaneous mutation frequency due to oxidative damage is enhanced to approximately 500-1000 times of the wild type strain. Suppressive abilities of two hydroxyl radical scavengers: D(-)-mannitol and thiourea, were examined and clear positive results were obtained, suggesting that the radical scavengers are suitable as the positive control for the test. Using Mut-Test, suppressive abilities of four vitamins: L-ascorbic acid, beta-carotene, folic acid and riboflavin; 10 polyphenols: caffeic acid, ellagic acid, (-)-epicatechin, (-)-epicatechin gallate, (-)-epigallocatechin, gallic acid, pyrocatechol, pyrogallol, quercetin and tannic acid which are recognized as antimutagens, were examined. Furthermore, the concentrations for 50% of suppressive abilities of five positive samples, L-ascorbic acid, folic acid, caffeic acid, pyrocatechol and pyrogallol were compared. Negative results were obtained in nine samples, riboflavin, tannic acid, etc. suggesting that their antimutagenic effect on cells may not be related to oxidative damage in cells.

Supercritical fluid extraction of catechins from Cratoxylum prunifolium dyer and subsequent purification by high-speed counter-current chromatography

Supercritical fluid extraction of tea catechins including epigallocatechin-3-O-gallate (EGCG) and epicatechin-3-O-gallate (ECG) from Cratoxylum prunifolium Dyer was performed. The optimization of parameters was carried out using an analytical-scale supercritical fluid extraction (SFE) system designed in our laboratory. Then the extraction was scaled up by 100 times using a preparative SFE system under a set of optimized conditions of 40 degrees C, 25 MPa and modified CO2 with 80% ethanol aqueous solution. The combined yield of EGCG and ECG reached about 1 mg per 1 g of tea leaves where the solubility was near 1.4 x 10(-4) mass fraction of CO2 fluid. EGCG and ECG of high purity (>98%) were obtained from the crude preparative extract by high-speed counter-current chromatography.

Interference of tannic acid on the genotoxicity of mitomycin C, methylmethanesulfonate, and nitrogen mustard in somatic cells of Drosophila melanogaster

The modulating effects of tannic acid (TA) on somatic mutation and mitotic recombination induced by methylmethanesulfonate (MMS), nitrogen mustard (HN2), and mitomycin C (MMC) were evaluated in the standard (ST) cross of the wing spot test in Drosophila melanogaster using co- and posttreatment protocols. It was shown that TA alone did not modify the spontaneous frequencies of single and twin spots, which means that this polyphenol neither acts as a genotoxin nor exerts any antigenotoxic effect over spontaneous DNA lesions. However, the simultaneous administration of genotoxins with TA can lead to considerable alterations of the frequencies of induced wing spots in comparison to those with administration of the genotoxins alone. In fact, TA produced a significant increase in HN2-induced wing spots with enhancements between 90 and 160%. For MMS, the enhancement was 38% in the highest TA concentration tested. In contrast, a significant protective action of this polyphenol was observed in combined treatments with MMC (64 to 99% inhibition). Moreover, the data from TA posttreatments demonstrated that this agent is not effective in exerting protective or enhancing effects on the genotoxicity of MMS, HN2, or MMC. One feasible mechanism of TA action is its interaction with the enzyme systems catalyzing the metabolic detoxification of MMS and HN2, which may also be involved in the bioactivation of MMC.

Antimutagenic and anticarcinogenic activity of tea polyphenols

Tea is the most popular beverage, consumed by over two thirds of the world's population. Tea is processed differently in different parts of the world to give green (20%), black (78%) or oolong tea (2%). Green tea is consumed mostly in Japan and China. The antimutagenic and anticarcinogenic activities of green tea are extensively examined. The chemical components of green and black tea are polyphenols, which include EC, ECG, EGC, EGCG and TFs. This article reviews the epidemiological and experimental studies on the antimutagenicity and anticarcinogenicity of tea extracts and tea polyphenols. In Japan, an epidemiological study showed an inverse relationship between habitual green tea drinking and the standardized mortality rates for cancer. Some cohort studies on Chanoyu (Japanese tea ceremony) women teachers also showed that their mortality ratio including deaths caused by malignant neoplasms were surprisingly low. The antimutagenic activity against various mutagens of tea extracts and polyphenols including ECG and EGCG has been demonstrated in microbial systems (Salmonella typhimurium and Escherichia coli), mammalian cell systems and in vivo animal tests. The anticarcinogenic activity of tea phenols has been shown in experimental animals such as rats and mice, in transplantable tumors, carcinogen-induced tumors in digestive organs, mammary glands, hepatocarcinomas, lung cancers, skin tumors, leukemia, tumor promotion and metastasis. The mechanisms of antimutagenesis and anticarcinogenesis of tea polyphenols suggest that the inhibition of tumors may be due to both extracellular and intracellular mechanisms including the modulation of metabolism, blocking or suppression, modulation of DNA replication and repair effects, promotion, inhibition of invasion and metastasis, and induction of novel mechanisms.

Antimutagenicity of Tochu tea (an aqueous extract of Eucommia ulmoides leaves): 1. The clastogen-suppressing effects of Tochu tea in CHO cells and mice

The suppressing effect of crude extracts of Tochu tea, an aqueous extract of Eucommia ulmoides leaves and a popular beverage in Japan, on the induction of chromosome aberrations in CHO cells and mice was studied. When CHO cells were treated with Tochu tea crude extract after MMC treatment, the frequency of chromosome aberrations was reduced. Out of 17 Tochu tea components, 5 irridoids (geniposidic acid, geniposide, asperulosidic acid, deacetyl asperulosidic acid, and asperuloside) and 3 phenols (pyrogallol, protocatechuic acid, and p-trans-coumaric acid) were found to have anticlastogenic activity. Since the anticlastogenic irridoids had an alpha-unsaturated carbonyl group, this structure was considered to play an important role in the anticlastogenicity. The anticlastogenic effect of Tochu tea extracts was examined in mice using a micronucleus assay. When mice received 1.0 ml 4% Tochu tea extract by oral gavage 6 h before intraperitoneal injection of MMC, a decrease in the frequency of micronuclei was observed. This decrease was not due to a delay in the maturation of micronucleated reticulocytes.

Antimutagenicity of Tochu tea (an aqueous extract of Eucommia ulmoides leaves): 2. Suppressing effect of Tochu tea on the urine mutagenicity after ingestion of raw fish and cooked beef

The effect of Tochu tea, which is an aqueous extract of Eucommia ulmoides leaves and a popular-beverage in Japan, on the urine mutagenicity before and after ingestion of raw fish and cooked beef was studied using Salmonella typhimurium YG1024. Urines were collected from seven healthy, non-smoking Japanese women before and after ingestion of raw fish and cooked beef. In experiment 1,3 were in a control group and 4 were in a Tochu tea-drinking group (2000 ml per day). The mutagenicity of urine from the Tochu tea-drinking group was much lower. In experiment 2 the 7 women switched groups; the tea-drinking group became the control group, and the control group became the Tochu tea-drinking group. Again, the mutagenicity of urine collected from the Tochu tea-drinking group was much lower. These results suggest that the decrease in the mutagenicity of the urine from the Tochu tea-drinking group was due to the intake of Tochu tea, but not to individual differences. Thus, the ingestion of Tochu tea may reduce human exposure to dietary mutagens.

Bio-antimutagenic activity of green tea catechins in cultured Chinese hamster V79 cells

The antimutagenic effects of green tea catechins, (-)-epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg) on induction of 6-thioguanine (6TG)-resistant mutations induced by 4-nitroquinolin 1-oxide (4NQO) were found in cultured Chinese hamster V79 cells. The antimutagenic activity of catechins was found only when cells were post-treated with catechins during the mutation expression time after treatment with 4NQO, and not found by simultaneous treatments with 4NQO and catechins. This bioantimutagenic activity of catechins were not observed in ethyl methanesulfonate (EMS)-induced mutations. This suggests that the antimutagenic effects of catechins may act intracellularly as bio-antimutagenic blocking agent or suppressive agent. These catechins had no effects on the cytotoxic activity of 4NQO in V79 cells, whether catechins were used in simultaneous treatment with or in post-treatment after 4NQO. This indicates that the antimutagenicity and anticytotoxicity to 4NQO may be caused by different mechanism(s).

Prevention of photocarcinogenesis by topical administration of pure epigallocatechin gallate isolated from green tea

Topical application of purified (-)-epigallocatechin-3-gallate (EGCG), a polyphenolic antioxidant isolated from green tea, inhibited photocarcinogenesis in BALB/cAnNHsd mice with no visible toxicity. Mice were treated with 0, 10, or 50 mg of EGCG in 200 microliters of acetone three times weekly for three weeks before ultraviolet (UV) treatments began and throughout the experiment. UV radiation consisted of five 30-minute exposures per week to banks of six FS40 Westinghouse sunlamps for 25 weeks. In the photocarcinogenesis study, mice received a total dose of approximately 2.1 x 10(6) J/m2. Skin cancer incidence in UV-irradiated mice was 96% at 28 weeks after the first UV treatment; EGCG at 10 or 50 mg reduced this incidence to 62% and 29%, respectively. UV-induced immunosuppression, assessed by the inability of UVB-irradiated mice to reject a syngeneic antigenic tumor, was not influenced by topical EGCG. Oral administration of 0, 100, or 500 mg of pure EGCG per liter of drinking water (approximately 0, 0.56, or 2.8 mg/day, respectively) did not decrease UV-induced skin tumor incidence, rate of primary tumor growth, or inability to reject antigenic tumors. Thus induction of skin tumors by UV radiation was significantly reduced by topical, but not by oral, administration of purified EGCG through a mechanism distinct from inhibition of photoimmunosuppression.

Biphenyl compounds are hydroxyl radical scavengers: their effective inhibition for UV-induced mutation in Salmonella typhimurium TA102

In our previous study, we found several hydroxylated biphenyl compounds have a great scavenging effect for hydroxyl radicals (.OH). In this study, to elucidate the relationship between generation of the .OH and photo-mutagenesis, six biphenyl compounds such as dehydrodieugenol, dehydrodivanillyl alcohol, dehydrodidihydroeugenol, dehydrodicreosol, magnolol and honokiol, respectively, were examined for their ability to inhibit UV-induced mutation in Salmonella typhimurium TA102. The relative mutagenic activities (RMA, %) indicated the mutation frequency of treated cells divided by the mutation frequency of control cells times 100%. The RMA (%) are as follows: 28 +/- 1, 31 +/- 1, 33 +/- 1, 41 +/- 2, 62 +/- 1, and 62 +/- 4 at concentrations of 5 micrograms per plate for dehydrodieugenol, dehydrodivanillyl alcohol, dehydrodidihydroeugenol, dehydrodicreosol, magnolol, and honokiol, respectively. These values indicate that low concentrations of these biphenyl compounds effectively suppress UV-induced mutagenesis. Also, these compounds acted as effective antimutagens in a dose-dependent manner (0.00005-5 micrograms per plate). These compounds are effective .OH scavengers. Consequently, the results obtained above suggest that these compounds could inhibit against UV-induced mutations by scavenging of .OH generated by UV irradiation. The results also suggest that .OH are associated with UV-induced mutation in Salmonella typhimurium TA102.

Identification of (+)-gallocatechin as a bio-antimutagenic compound in Psidium guava leaves

From the MeOH-extract of guava leaves, (+)-gallocatechin was isolated as a bio-antimutagenic compound against UV-induced mutation in Escherichia coli. This strengthens the evidence that phenolic compounds require three neighbouring-OH groups in order to possess this activity.

Bio-anticlastogenic effects of unsaturated fatty acids included in fish oil--docosahexaenoic acid, docosapentaenoic acid, and eicosapentaenoic acid--in cultured Chinese hamster cells

Bio-anticlastogenic effects of unsaturated fatty acids--cis-4,7,10,13,16,19-docosahexaenoic acid (DHA), cis-7,10,13,16,19-docosapentaenoic acid (DPA), and cis-5,8,11,14,17-eicosapentaenoic acid (EPA)--on chemically induced chromosome aberrations were studied in cultured Chinese hamster cells. The induction of chromosome aberrations by the crosslinking agents mitomycin C (MMC) and cisplatin (DDP), the SN-1 type alkylating agents N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG), methyl nitrosourea (MNU), and ethyl nitrosourea (ENU), and the SN-2 type alkylating agent ethyl methanesulfonate (EMS), but not by the SN-1 type alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and the SN-2 type alkylating agent methyl methanesulfonate (MMS), was suppressed by post-treatment with DHA, DPA, and EPA. Since there was no opportunity to inactivate mutagens by desmutagenic mechanisms under the post-treatment schedule used, the results demonstrate the bio-anticlastogenicity of unsaturated fatty acids. Suppression by the unsaturated fatty acids was observed when cells were treated during the G2 phase, suggesting that G2 events were responsible for the bio-anticlastogenic effects. Two saturated fatty acids with the same number of carbons as the studied unsaturated fatty acids--docosanoic acid and eicosanoic acid--did not affect chromosome aberration induction, suggesting the necessity of unsaturation for fatty acid bio-anticlastogenicity.

Sister-chromatid exchanges induced by trihalomethanes in rat erythroblastic cells and their suppression by crude catechin extracted from green tea

An in vitro sister-chromatid exchange (SCE) assay using rat erythroblastic leukemia cells was conducted with four major trihalomethanes (THMs): chloroform, CHCl3; dichlorobromomethane, CHCl2Br, dibromochloromethane, CHClBr2; bromoform, CHBr3. In the absence of S9 mix, CHBr3, CHClBr2 and CHCl2Br significantly induced SCEs in a clear dose-dependent manner, while CHCl3 did not significantly induce SCEs. On the other hand, the incidence of CHCl3-induced SCEs significantly increased, although the incidence of CHBr3-induced SCEs decreased by the addition of S9 mix. However, there was no difference between the incidence of SCEs induced by CHBr3, CHClBr2 or CHCl2Br in the absence of S9 mix and that in the presence of S9 mix. The addition of crude catechin to the SCE assay system suppressed the ability of CHCl3 or CHBr3 to induce SCEs but had no suppressive effect on the other THM-induced SCEs. The suppression of SCEs induced by CHCl3 or CHBr3 depended on the crude catechin dose.

The clastogen-suppressing effects of green tea, Po-lei tea and Rooibos tea in CHO cells and mice

The suppressing effects of crude extracts of three kinds of tea-green tea (GT) from Japan, Po-lei tea (PT) from China, and Rooibos tea (RT) from South Africa-on the induction of chromosome aberrations in cultured CHO cells and mice were studied. When CHO cells were exposed to each tea extract in the presence of rat liver microsomal enzymes (S9 mix) together with benzo[a]pyrene (B(a)P) or mitomycin C (MMC), a decrease in the frequency of chromosome aberrations was observed. PT and RT, but not GT, also suppressed the induction of chromosome aberrations by MMC in the absence of S9 mix. When cells were treated with tea extract after B(a)P or MMC treatment, RT suppressed the induction of chromosome aberrations in the presence and absence of S9 mix whereas GT and PT showed suppressing effects only in the presence of S9 mix. These data suggest that catechines, well-known antimutagens in tea samples, might account for the inhibitory effect in the case of GT and PT. Since RT contains few catechines, several unknown antimutagenic components could be responsible for its effect. The antimutagenic effects of tea extracts at concentration levels consumed by humans were examined in mice using micronucleus induction with B(a)P or MMC. When mice received oral gavage of 0.2% GT, 0.1% PT, and 0.1% RT at 1.0 ml/mouse 6 h before intraperitoneal injection of MMC, a decrease in the frequency of micronuclei was observed. The induction of micronuclei by B(a)P was suppressed by oral dosage of GT, PT and RT at 1.0 ml/mouse/day for 28 days. This was not due to a delay in the maturation of micronucleated reticulocytes. In conclusion, intake of tea might suppress the mutagenic activity of certain potent mutagens in human beings.

Antimutagenic effects of N-methyl-valyl-amiclenomycin (BA-2) isolated from the metabolites of Streptomyces sp

A novel antimutagenic factor, BA-2, active against UV-induced mutagenesis in Escherichia coli WP2 was isolated from the metabolites of Streptomyces sp. strain AJ9455. BA-2 also suppressed mutations induced by 4-nitroquinoline N-oxide (4-NQO) and furylfuramide (AF-2) in E. coli WP2s (uvrA) without any decrease of cellular viability. BA-2 strongly inhibited the UV induction of SOS repair functions when it was monitored by beta-galactosidase activity expressed from the sulA::lacZ fusion gene of strain PQ37. It is assumed that the antimutagenic effect of BA-2 on mutagenesis induced by UV, 4-NQO or AF-2 was the result of inhibition of induction of the inducible error-prone SOS repair. The structure of BA-2 was considered to be N-methyl-valyl-amiclenomycin, and the structural unit of 4-amino-2,5-cyclohexadiene must be essential for the antimutagenic activity, since deamination by heating results in the loss of antimutagenic activity of BA-2.

Organotins are co-clastogens in a whole mammalian system

The frequency of micronuclei induced by mitomycin C (MMC) in mouse peripheral reticulocytes was enhanced by treatment with organotins: bis(tri-n-butyltin) oxide (TBTO) and triphenyltin chloride (TPTC). TBTO and TPTC did not themselves induce micronucleated reticulocytes (MNRETs) in mouse peripheral blood. When 50 mg/kg TBTO or 100 mg/kg TPTC was given orally to mice simultaneously with an intraperitoneal (i.p.) administration of 1 mg/kg MMC, however, TBTO and TPTC caused about 55% and 51% increases, respectively, in MMC-induced a synergistic MNRET frequency. Organotin administration 3 or 6 h before and 3 h after MMC injection also caused enhancement of MNRET frequency. These results demonstrate that TBTO and TPTC act as co-clastogens in a whole mammalian system.

Synergistic effect between tannic acid and X-rays detected by the Tradescantia-micronucleus assay

Tannic acid (TA), a complex mixture of polyphenolics, exhibited synergism with 4-nitroquinoline 1-oxide (4-NQO), methyl methanesulfonate (MMS) and cis-platinum (cis-DDP) in a recent study on w/w+ somatic mutation in the eye pigment of Drosophila, although several studies indicated that tannic acid is an antimutagen in cultured mammalian cells. The goal of this study was to determine the genotoxicity of tannic acid alone and its possible synergistic effect with X-rays using the Tradescantia-micronucleus (Trad-MCN) bioassay. Plant cuttings were irradiated with 35 R of X-rays (80 kV, 5 mA) and followed by a series of increasing dosages (0.1, 0.5, 0.75, 1.0, 1.25, 1.50 mM) of TA treatment (24 h) and in some cases TA treatment was followed by X-irradiation. Inflorescences were fixed after a 24-h recovery period and slides were prepared for scoring MCN frequencies. Four series of experiments were conducted and the results of Trad-MCN tests on X-rays alone yielded an average of 47.5 MCN/100 tetrads (SE = 6.08), and 1.0 mM TA alone yielded an average of 8.95 MCN/100 tetrads (SE = 0.1), while the combined treatments (35 R X-rays plus 1.0 mM TA) yielded an average of 126.95 MCM/100 tetrads (SE = 13.69). The MCN frequency of the negative control was around 4.6 MCN/100 tetrads (SE = 0.75). This kind of synergism was exhibited through all the increasing dosages around 1.0 mM or higher. The synergistic effect of these two agents remained at the same level when TA was followed by X-irradiation. When a 12-h repairing period was allowed after X-irradiation in the combined treatment, the MCN frequency was similar to that of the X-ray treatment alone. The synergistic effect in the cases where the TA exposure was given immediately after X-irradiation could be attributed to the inhibitory action of TA on the DNA repair process.

Enhancing effects of heterocyclic amines and beta-carbolines on the induction of chromosome aberrations in cultured mammalian cells

The effects of post-treatment with heterocyclic amines and beta-carbolines on the induction of chromosome aberrations were studied in Chinese hamster CHO K-1 cells and SV40-transformed excision repair-deficient human XP2OSSV cells. The number of chromosome aberrations induced by UV and MMC were increased by post-treatment with Trp-P-1 and Trp-P-2, in both the presence and the absence of S9 mix. A alpha C, MeA alpha C, Glu-P-1, Glu-P-2, IQ, MeIQ, harman and harmine increased chromosome aberrations only in the presence of S9 mix. Glu-P-2, IQ, MeIQ, harman, and harmine did not induce chromosome aberrations by themselves at the concentrations used in this study. Trp-P-1, Trp-P-2, A alpha C, MeA alpha C and Glu-P-1 were weak clastogens by themselves, but at much higher concentrations than those at which they increased the induction of chromosome aberrations in cells pretreated with UV or MMC. Therefore, the increases in chromosome aberrations were not considered to be additive.

Glycyrrhiza glabra extract as an effector of interception in Escherichia coli K12+

Glycyrrhiza glabra polar lipid extract contains a number of flavonoids and related chemical compounds. Studies on the effectiveness of Glycyrrhiza glabra polar lipid extract in intercepting reactive molecules generated from the illumination of the photosensitizers rose bengal and phenosafranin indicate that it is effective in preventing cytotoxicity against E. coli K12+ in a dose-related fashion using illuminated rose bengal. Since only a modest scavenging of singlet oxygen generated from phenosafranin is observed, the effects of the extracts are less related to singlet oxygen-mediated oxidation of substrate (type II reactions) than non-singlet oxygen-mediated oxidation of substrate (type I reactions). Elevated levels of glutathione observed in exponentially growing cells of E. coli K12 were also observed.

Bio-antimutagenic activities of vitamin B6 in E. coli and mouse peripheral blood cells

Pyridoxal (PL) and pyridoxal 5'-phosphate (PLP) showed a marked bio-antimutagenic effect on UV-induced mutagenesis in E. coli B/r WP2, but not in the DNA excision repair-deficient strain WP2suvrA under the condition where no cellular toxicity was observed. No delay in the first cell division was seen on post-treatment with PL after UV irradiation. PL reduced not only UV- but 4-nitroquinoline-1-oxide-induced mutation, while it was ineffective in N-methyl-N'-nitro-N-nitrosoguanidine- or gamma-ray-treated cells. These results suggest that PL promotes DNA excision repair directly or indirectly and the decrease in the amount of unrepaired DNA damage might cause the reduction of UV-induced mutations in E. coli B/r WP2. In addition to the above observation, PLP reduced the frequency of mitomycin C- (2 mg/kg, i.p.) induced micronuclei in mouse peripheral blood cells. Simultaneous or subsequent oral administration of PLP (25 mg/kg) decreased the frequency of micronucleated peripheral reticulocytes.

Tea tannin components modify the induction of sister-chromatid exchanges and chromosome aberrations in mutagen-treated cultured mammalian cells and mice

The modifying effects of tannin components extracted from green tea and black tea on mutagen-induced SCEs and chromosome aberrations were studied. These tannin components did not affect spontaneous SCEs and chromosome aberrations in cultured Chinese hamster cells. The frequency of SCEs and chromosome aberrations induced by mitomycin C (MMC) or UV was enhanced by the posttreatment with tea tannin components. When cells were post-treated with tea tannin components in the presence of metabolic enzymes of rat liver (S9 mix), the modifying effects on the induction of SCEs and chromosome aberrations by mutagens were complicated. MMC- and UV-induced SCEs and chromosome aberrations were suppressed by the posttreatment with tea tannin components at low concentrations (less than or equal to 6.7 micrograms/ml) with S9 mix. At a high concentration of tea tannin components (20 micrograms/ml) with S9 mix, a co-mutagenic effect was observed. The modifying effects of tea tannin components were shown to occur in the G1 phase of the cell cycle. In cells from a patient with xeroderma pigmentosum (XP) and a normal human embryo, MMC-induced SCEs were suppressed by the posttreatment with tea tannin components in the presence of S9 mix, and enhanced in the absence of S9 mix. On the other hand, tea tannin components modified SCE frequencies in UV-irradiated normal human cells but not in UV-irradiated XP cells. Our results suggested that tea tannin components themselves inhibited DNA-excision repair and resulted in a co-mutagenic effect, while in the presence of S9 mix metabolites of tea tannin components promoted DNA-excision repair activity and resulted in an antimutagenic effect. MMC-induced chromosome aberrations in mouse bone marrow cells were suppressed by the pretreatment with green tea and black tea tannin mixture.

In vivo anticlastogenic and antimutagenic effects of tannic acid in mice

The anticlastogenic effect of tannic acid was studied in vivo in the mouse micronucleus test. The frequencies of micronuclei induced by mitomycin C, ethyl nitrosourea (ENU) or 4-nitroquinoline 1-oxide in mouse bone marrow cells were decreased by the oral administration of tannic acid 6 h before the mutagen injection. The observed suppressing effect was not a reflection of a delay in the formation of micronuclei by the cytotoxic effect of tannic acid. The antimutagenic effect of tannic acid was also investigated in vivo in the mouse spot test using male PW and female C57BL/10 mice. Tannic acid was given orally to pregnant females 6 h before the intraperitoneal injection of ENU on the 10th day of pregnancy. The frequency of pups with recessive color spots induced by ENU was decreased by the administration of tannic acid. The observed decrease was not due to toxic effects on the embryo. These results indicate that tannic acid acts as an anticlastogen and antimutagen in vivo.

Enhancing effects of cinoxate and methyl sinapate on the frequencies of sister-chromatid exchanges and chromosome aberrations in cultured mammalian cells

Sister-chromatid exchanges (SCEs) induced by mitomycin C (MMC), 4-nitroquinoline-1-oxide (4NQO) or UV-light in cultured Chinese hamster ovary cells (CHO K-1 cells) were enhanced by cinoxate (2-ethoxyethyl p-methoxycinnamate) or methyl sinapate (methyl 3,5-dimethoxy 4-hydroxycinnamate). Both substances are cinnamate derivatives and cinoxate is commonly used as a cosmetic UV absorber. Methyl sinapate also increased the frequency of cells with chromosome aberrations in the CHO K-1 cells treated with MMC, 4NQO or UV. These increasing effects of methyl sinapate were critical in the G1 phase of the cell cycle and the decline of the frequencies of UV-induced SCEs and chromosome aberrations during liquid holding was not seen in the presence of methyl sinapate. Both compounds were, however, ineffective in cells treated with X-rays. In cells from a normal human embryo and from a xeroderma pigmentosum (XP) patient, MMC-induced SCEs were also increased by the post-treatment with methyl sinapate. The SCE frequencies in UV-irradiated normal human cells were elevated by methyl sinapate, but no SCE-enhancing effects were observed in UV-irradiated XP cells. Our results suggest that the test substances inhibit DNA excision repair and that the increase in the amount of unrepaired DNA damage might cause the enhancement of induced SCEs and chromosome aberrations.

Antimutagenesis by factors affecting DNA repair in bacteria

The term 'antimutagen' was originally used to describe an agent that reduces the apparent yield of spontaneous and/or induced mutations, regardless of the mechanisms involved. The 'antimutagens' include 'desmutagens' and 'bio-antimutagens'. In this article, our attention was focused on the bio-antimutagens affecting DNA repair in bacteria. Cobaltous chloride reduced the frequency of mutations in Escherichia coli induced by MNNG. The possibility that metal compound inhibits the growth of mutagen-treated cells was examined. The results clearly showed that the antimutagen surely reduces the mutation rate. The target of cobaltous chloride was found to be cellular factors including Rec A. Vanillin and cinnamaldehyde had strong antimutagenic activities against UV, 4NQO and AF-2. They stimulated Rec A-dependent recombination repair functions in the mutagen-treated cells. Among plant materials, tannins possess antimutagenic activity against UV-induced mutations in E. coli. It has been found that tannic acid stimulates the excision repair encoded by the uvrA gene thereby reducing the yield of mutants. Substances which are antimutagenic in bacterial systems also had antimutagenic activity in cultured mammalian cell systems. Vanillin reduced the frequency of mutagen-induced chromosomal aberrations.