A comparative study of the antimutagenic effects of antioxidants on chemical mutagenesis in Drosophila melanogaster

A Review on the Antimutagenic and Anticancer Effects of Cysteamine

Cancer is one of the leading causes of death worldwide. First-line treatments usually include surgery, radiotherapy, and/or systemic therapy. These methods can be associated with serious adverse events and can be toxic to healthy cells. Despite the new advances in cancer therapies, there is still a continuous need for safe and effective therapeutic agents. Cysteamine is an aminothiol endogenously synthetized by human cells during the degradation of coenzyme-A. It has been safely used in humans for the treatment of several pathologies including cystinosis and neurodegenerative diseases. Cysteamine has been shown to be a potent antimutagenic, anticarcinogenic, and antimelanoma in various in vitro and in vivo studies, but a review on these aspects of cysteamine's use in medicine is lacking in the current literature. The efficacy of cysteamine has been shown in vitro and in vivo for the treatment of different types of cancer, such as gastrointestinal cancer, pancreatic cancer, sarcomas, hepatocellular carcinoma, and melanoma, leading to the significant reduction of lesions and/or the increase of survival time. Although the mechanisms of action are not fully understood, possible explanations are (i) free radical scavenging, (ii) alteration of the tumor cell proliferation by affecting nucleic acid and protein synthesis or inhibition of DNA synthesis, and (iii) hormone regulation. In conclusion, regarding the high safety profile of cysteamine and the current literature data presented in this article, cysteamine might be considered as an interesting molecule for the prevention and the treatment of cancer. Further clinical studies should be performed to support these data in humans.

Genotoxic and genoprotective effects of 1,4-dihydropyridine derivatives: a brief review

This review summarises current knowledge about the genotoxic and genoprotective effects of 1,4-dihydropyridines (DHP) with the main focus on the water-soluble 1,4-DHPs. Most of these water-soluble compounds manifest very low calcium channel blocking activity, which is considered "unusual" for 1,4-DHPs. Glutapyrone, diludine, and AV-153 decrease spontaneous mutagenesis and frequency of mutations induced by chemical mutagens. AV-153, glutapyrone, and carbatones protect DNA against the damage produced by hydrogen peroxide, radiation, and peroxynitrite. The ability of these molecules to bind to the DNA may not be the only mechanism of DNA protection, as other mechanisms such as radical scavenging or binding to other genotoxic compounds may take place and enhance DNA repair. These uncertainties and reports of high 1,4-DHP concentrations damaging the DNA call for further in vitro and in vivo preclinical research, pharmacokinetic in particular, as it can help pinpoint the exact mechanism(s) of the genotoxic and/or genoprotective action of 1,4-DHPs.

Protective Effect of Emblica officinalis in Cyprinus carpio against Hepatotoxicity Induced by Malachite Green: Ultrastructural and Molecular Analysis

Malachite green (MG) dye, besides coloring is used as an effective aquaculture therapeutic. The present study assesses the mitigating ability of Emblica officinalis (EO) fruit extract against the dye induced chronic (60 days) cyto-toxicity in Cyprinus carpio. For this, four experimental groups were maintained: group I—control, group II—MG, group III—EO (positive control), group IV—MG + EO. The study was made at three tiers: detailing structural anomalies using a light microscope and transmission electron microscope (TEM), biochemical estimation of antioxidant enzymes, and lipid peroxidation and molecular analysis of expression patterns of HSP70, and CYP1A genes. MG intoxication resulted in necrosis, cytoplasmic vacuolation, glycogen depletion, abundant macrophages, loss of cell integrity and prominent nuclear alterations. Significant (p < 0.05) inhibition in the activities of catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) and reduced glutathione (GSH), along with an elevation in malondialdehyde (MDA) levels, occurred after 60 days of MG exposure. CYP1A and HSP70 genes presented a significant change in their expression in MG treated fish. Whereas oral supplementation with EO significantly restored the histo-architecture, normalized the altered enzymatic activity, reduced the oxidative stress level and regulated the expression of HSP70 and CYP1A genes. Thus, it can be concluded that EO acted as an effective ameliorant against malachite green induced cyto-toxicity in Cyprinus carpio.

Determination of genotoxic and antigenotoxic effects of wild-grown Reishi mushroom (Ganoderma lucidum) using the hen's egg test for analysis of micronucleus induction

The micronucleus (MN) technique is commonly used for genotoxicity testing. The hen's egg test (HET) for analysis of MN induction (HET-MN) is an inexpensive, rapid and simple genotoxicity assay that is compatible with animal protection and ethical considerations. Ganoderma lucidum (Curtis) P. Karst is known also as reishi mushroom and mushroom of immortality. It has long been used to treat disorders including fungal infections, influenza, common cold, hepatitis, diabetes, high cholesterol and cancer in many countries including China and Japan. G. lucidum strengthens the immune system and reduces the side effects of chemo- and radiotherapy. We investigated the possible genotoxic and antigenotoxic effects of the aqueous extract of wild-grown G. lucidum from Turkey using the HET-MN test. Three different doses of aqueous extract of G. lucidum, 50 µg/egg vitamin C as an antigenotoxic agent and 50 µg/egg cyclophosphamide as a genotoxic compound were injected separately or together into fertilized chicken eggs at incubation day 8. Embryonic peripheral blood smears were prepared and stained with a modified May-Grünwald-Giemsa method on incubation day 11. The frequencies of MN and nuclear abnormalities in erythrocytes were determined using light microscopy. Although the aqueous extract G. lucidum exhibited no genotoxic effect, it did exhibit an antigenotoxic effect. Our findings suggest that G. lucidum extract is a valuable natural antigenotoxic agent.

Genotoxic and antigenotoxic assessment of four newly synthesized dihydropyridine derivatives

The current study aims to determine the genotoxic and antigenotoxic potential of four newly synthesized dihydropyridine derivatives using Escherichia coli WP2 and Ames/ Salmonella bacterial reversion assay systems. The bacterial mutant tester strains, E. coli WP2 uvrA with a point mutation and Salmonella typhimurium TA1537 with a frameshift mutation, were used to determine genotoxic potentials of the test compounds. To determine antigenotoxic potentials of the test compounds, the same strains were also used together with positive mutagens N-methyl- N′-nitro- N-nitrosoguanidine (MNNG) for E. coli WP2 uvrA and 9-aminoacridine (9-AA) for S. typhimurium TA1537. According to the results, neither of the test compounds showed significant genotoxic activity on both tester strains at the tested concentrations. However, except compound 4, all the test compounds showed significant antigenotoxic activity on MNNG- or/and 9-AA-induced mutations. The inhibition rates of mutagenesis ranged from 27.0% (compound 2: 2.5 mM/plate) to 65.0% (compound 2: 0.5 mM/plate) for MNNG and from 30.6% (compound 2: 2 mM/plate) to 58.5% (compound 1: 1 mM/plate) for 9-AA genotoxicity. According to these results, it is concluded that all the test compounds do not have a mutagenic potential on the bacterial strains at the tested concentrations, and some of them have antigenotoxic potentials against MNNG- and 9-AA-induced mutagenesis.

Inhibition by beta-caryophyllene of ethyl methanesulfonate-induced clastogenicity in cultured human lymphocytes

beta-Caryophyllene is a bi-cyclic sesquiterpene that occurs in essential oils from several plants. A variety of biological activities have been ascribed to this compound. In particular, it seems to possess anti-carcinogenic properties, due to its capability to induce detoxifying enzymes or to enhance, in vitro and in vivo, the natural killer cell-induced cytotoxicity against tumours. Conversely, the knowledge on the DNA-damaging activity of the substance and its modulation is scanty. Therefore, in this study, we aimed at evaluating the capability of beta-caryophyllene to protect cultured human lymphocytes from the genotoxic damage induced by ethyl methanesulfonate (EMS) and colcemid (COL) in the micronucleus assay. To investigate the mechanisms of action of this sesquiterpene, the cultures were treated with the compound before (pre-treatment), during (co-treatment) and after (post-treatment) treatment with the mutagens. Up to 100 microg/ml, beta-caryophyllene by itself did not produce any cytotoxic and genotoxic effect, as shown by the value of the nuclear division index (NDI) and the frequency of micronuclei (MN). The test compound (0.1-100 microg/ml) significantly reduced the MN frequency induced by EMS in pre- and co-treatment protocols (up to 64.4% and 87% reduction, respectively). In the post-treatment protocol, beta-caryophyllene was not effective as an antimutagen. No significant reduction of COL-induced MN frequency was found. The antigenotoxic activity of beta-caryophyllene observed here suggests that this compound could act by chemical interaction with the mutagen in the growth medium (co-treatment) or in the cytoplasm of lymphocytes (pre-treatment), so acting as a desmutagen. These data encourage further studies to investigate the mode of action and the potential use of this compound as a chemopreventive agent.

Dihydropyridines decrease X-ray-induced DNA base damage in mammalian cells

Compounds with the structural motif of 1,4-dihydropyridine display a broad spectrum of biological activities, often defined as bioprotective. Among them are L-type calcium channel blockers, however, also derivatives which do not block calcium channels exert various effects at the cellular and organismal levels. We examined the effect of sodium 3,5-bis-ethoxycarbonyl-2,6-dimethyl-1,4-dihydropyridine-4-carboxylate (denoted here as DHP and previously also as AV-153) on X-ray-induced DNA damage and mutation frequency at the HGPRT (hypoxanthine-guanine phosphoribosyl transferase) locus in Chinese hamster ovary CHO-K1 cells. Using formamido-pyrimidine glycosylase (FPG) comet assay, we found that 1-h DHP (10nM) treatment before X-irradiation considerably reduced the initial level of FPG-recognized DNA base damage, which was consistent with decreased 8-oxo-7,8-dihydro-2'-deoxyguanosine content and mutation frequency lowered by about 40%. No effect on single strand break rejoining or on cell survival was observed. Similar base damage-protective effect was observed for two calcium channel blockers: nifedipine (structurally similar to DHP) or verapamil (structurally unrelated). So far, the specificity of the DHP-caused reduction in DNA damage - practically limited to base damage - has no satisfactory explanation.

Ameliorative effects of vitamin supplementation on ethyl methane sulphonate-induced genotoxicity in a fish, Anabas testudineus

The efficacy of 0.02% vitamin C (VC; l-ascorbic acid) and 0.05% beta-carotene (BC) at the rate of 1 ml/100g of body weight in amelioration of ethyl methane sulphonate (EMS)-induced genotoxicity has been studied in an Indian endemic fish, Anabas testudineus by using several cytogenetical endpoints like chromosome aberrations, micronuclei (MN) and abnormal nuclei (AN), and sperm head anomaly at 6, 24, 48, 72 and 96 h after treatment, as compared to suitable controls (distilled water (DW)-treated control for EMS and VC-treated fish, and 1% alcohol-treated control for BC-treated fish). Both VC and BC reduced EMS-induced genotoxicity at all the fixation intervals as compared to their respective controls. Additionally, effects of two more doses of VC (0.01% and 0.05%) and BC (0.02% and 0.1%) were analyzed at 72 h after treatment (at the peak period of EMS genotoxicity) for testing their relative efficacy in amelioration of EMS-induced cytogenetical damage in this fish. All the three doses of both VC and BC appeared to reduce the EMS-induced genotoxicity in this fish to a variable extent, of which the higher dose of VC appeared to give marginally better protection while the dose-response relationship was inconclusive for BC. The results of this study can lead to future research for exploring if low doses of these vitamins may be useful in protecting fish from genotoxic damage on exposure to mutagenic agents in small confined/stagnant waters.

Changes in poly(ADP-ribose) level modulate the kinetics of DNA strand break rejoining

ADP-ribose polymers are rapidly synthesized in cell nuclei by the poly(ADP-ribose) polymerases PARP-1 and PARP-2 in response to DNA strand interruptions, using NAD(+) as precursor. The level of induced poly(ADP-ribose) formation is proportional to the level of DNA damage and can be decreased by NAD(+) or PARP deficiency, followed by poor DNA repair and genomic instability. Here we studied the correlation between poly(ADP-ribose) level and DNA strand break repair in lymphoblastoid Raji cells. Poly(ADP-ribose) synthesis was induced by 100 microM H(2)O(2) and intensified by the 1,4-dihydropyridine derivative AV-153. The level of poly(ADP-ribose) in individual cells was analyzed by quantitative in situ immunofluorescence and confirmed in whole-cell extracts by Western blotting, and DNA damage was assessed by alkaline comet assays. Cells showed a approximately 100-fold increase in poly(ADP-ribose) formation during the first 5 min of recovery from H(2)O(2) treatment, followed by a gradual decrease up to 15 min. This synthesis was completely inhibited by the PARP inhibitor NU1025 (100 microM) while the cells treated with AV-153, at non-genotoxic concentrations of 1 nM-10 microM, showed a concentration-dependent increase of poly(ADP-ribose) level up to 130% after the first minute of recovery. The transient increase in poly(ADP-ribose) level was strongly correlated with the speed and efficiency of DNA strand break rejoining (correlation coefficient r > or = 0.92, p<0.05). These results are consistent with the idea that poly(ADP-ribose) formation immediately after genome damage reflects rapid assembly and efficient functioning of repair machinery.

Investigation of the mutagenic and antimutagenic effects of Origanum compactum essential oil and some of its constituents

In the present study, the chemical composition of Origanum compactum essential oil was determined by gas chromatography and mass spectrometry, and its mutagenic and antimutagenic activities were investigated by the somatic mutation and recombination test (SMART) in Drosophila melanogaster. No significant increase in the number of somatic mutations was observed with the essential oil tested using both the standard (ST) and high bio-activation (HB) cross. In order to investigate the antimutagenic effect of the essential oil, we have tested the effect on the indirect-acting mutagen urethane (URE), as well as the direct-acting mutagen methyl methanesulfonate (MMS). O. compactum essential oil showed a strong inhibitory effect against URE-induced mutagenicity, especially with the HB cross. However, only a weak inhibitory effect on the mutagenicity induced by MMS was observed. These results suggest that the detected antimutagenicity could be mediated by an inhibitory effect on metabolic activation. The essential oil was fractionated to identify the components responsible of the suppressing effect detected. Seven fractions were obtained: two of them showed the most potent inhibitory effect against URE-induced mutagenicity and were further fractionated. The sub-fractions obtained from the second chromatographic fractionation were tested for their antimutagenic activity, together with carvacrol and thymol. The highest antimutagenic effect obtained with the sub-fractions was similar to the effect of the crude essential oil, as well as to the effect of carvacrol alone. These results suggest the absence of a synergic antimutagenic effect between the components of O. compactum essential oil and indicate that carvacrol was the most active oil component.

Bioactive 1,4-dihydroisonicotinic acid derivatives prevent oxidative damage of liver cells

1,4-Dihydroisonicotinic acid derivatives (1,4-DHINA) are compounds closely related to derivatives of 1,4-dihydropyridine, a well-known calcium channel antagonists. 1,4-DHINA we used were derived from a well-known antioxidant Diludin. Although some compounds have neuromodulatory or antimutagenic properties, their activity mechanisms are not well known. This study was performed to obtain data on antioxidant and bioprotective activities of: 2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydroisonicotinic acid (Ia); sodium 2-(2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine-4-carboxamido)glutamate (Ib) and sodium 2-(2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine-4-carboxamido)ethane-sulphate (Ic). 1,4-DHINA's activities were studied in comparison to Trolox by: N,N-Diphenyl-N'-picrylhydrazyl (DPPH*), deoxyribose degradation, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical scavenging and antioxidative capacity assays; copper-induced lipid peroxidation of cultured rat liver cells (malondialdehyde determination by high performance liquid chromatography and 4-hydroxynonenal-protein conjugates by dot-blot); (3)H-thymidine incorporation and trypan blue assay for liver cells growth and viability. In all assays used Ia was the most potent antioxidant. Ia was also a potent antioxidant at non-toxic concentrations for liver cell cultures. It completely abolished, while Ic only slightly decreased copper-induced lipid peroxidation of liver cells. Thus, antioxidant capacities are important activity principle of Ia, which was even superior to Trolox in the cell cultures used, while activity principles of Ic and Ib remain yet to be determined.

Anti-genotoxic effect of Aloysia triphylla infusion against acrylamide-induced DNA damage as shown by the comet assay technique

Aloysia triphylla a perennial, bushy plant originally from South America has long been used in traditional medicine. Its aqueous extract contains considerable amounts of polyphenolic compounds, namely flavonoids and phenolic acids. In view of the interest in natural phenolic compounds as antioxidant in preventive medicine, this study was undertaken to investigate the chemoprotective effects of cedron leaves infusion against the genetic damage induced by acrylamide (AA) by using the alkaline version of the comet assay technique. Mice were separated in nine groups (eight animals each): (I) untreated, (II) negative control, (III) treated with infusion of cedron leaves 5%, 20 days twice a day, (IV) treated with AA (5 mg/kg b.w.), (V) treated with AA (20 mg/kg b.w.), (VI) treated with AA (30 mg/kg b.w.), (VII) treated with AA (50 mg/kg b.w.), (VIII) pretreated with infusion and treated with AA (50 mg/kg b.w.) and (IX) positive control (cyclophosphamide, 20 mg/kg b.w.). Three hundred blast cells were digitally evaluated per animal from three different slides (100 each). Media of tail moment (TM) values were analyzed by ANOVA test. No statistical differences (p>0.05) were found between untreated animals, negative control and infusion-treated mice. A single dose of AA-induced genetic damage as revealed by a statistically significant increase in TM values (p<0.01). Pretreatment with infusion prior to AA injection significantly reduces the capacity of AA to induce genetic damage. In these conditions, tail moments values did not differ from data obtained in negative control (p>0.05) and exhibit statistical differences from animals treated only with AA (p<0.01). Cell viability was at least 90% in all cases as measured by the trypan blue exclusion method. The ferric reducing ability of plasma (FRAP) method reveals that the plasma of infusion-treated mice has a significantly higher antioxidant capacity than plasma from controls (p<0.01). The results suggest that the infusion could exerts an in vivo chemo protective action, probably due to its scavenging potency towards free radicals.

A 1,4-dihydropyridine derivative reduces DNA damage and stimulates DNA repair in human cells in vitro

Compounds of the 1,4-dihydropyridine (1,4-DHP) series have been shown to reduce spontaneous, alkylation- and radiation-induced mutation rates in animal test systems. Here we report studies using AV-153, the 1,4-DHP derivative that showed the highest antimutagenic activity in those tests, to examine if it modulates DNA repair in human peripheral blood lymphocytes and in two human lymphoblastoid cell lines, Raji and HL-60. AV-153 caused a 50% inhibition of growth (IC50) of Raji and HL-60 cells at 14.9+/-1.2 and 10.3+/-0.8mM, respectively, but did not show a cytotoxic effect at concentrations <100 microM. Alkaline single-cell gel electrophoresis (comet) assays showed that AV-153 reduced the number of DNA strand breaks in untreated cells and also in cells exposed to 2 Gy of gamma-radiation, 100 microM ethylmethane sulfonate (EMS), or 100 microM H2O2. DNA damage was reduced by up to 87% at AV-153 concentrations between 1 and 10nM, and a positive dose-effect relationship was seen between 0.01 and 1 nM. Comparison of the kinetics of DNA strand-break rejoining in the presence and absence of AV-153 revealed a considerable influence on the rate of repair. In view of the resemblance of this compound's structure to that of dihydronicotinamide, a substrate for poly(ADP-rybose)polymerase, the modulation of DNA repair by AV-153 could involve an influence on poly(ADP)ribosylation.

Protective action of vitamins on the spermatogenesis in lead-treated Swiss mice

The protective action of vitamins C and E against lead acetate-induced reduced sperm count and sperm abnormalities in Swiss mice has been studied. Intraperitoneal injection of lead acetate (10mg/kg body weight) in the present study stimulates lipid peroxidation in the testicular tissue, indicated by a significant increase in malondialdehyde content in the experimental mice group. This is associated with an increased generation of noxious reactive oxygen species (ROS). Significantly reduced sperm count associated with increased sperm abnormality percentage in the lead-injected mice group compared to controls substantially proves the ongoing damaging effects of lead-induced ROS on developing germ cells. However, intraperitoneal administration of vitamin C (Vit C) at a concentration equivalent to the human therapeutic dose (10 mg/kg body weight) was able to minimize significantly the testicular malondialdehyde content with a concomitant increase in sperm count and significant decrease in the percentage of abnormal sperm population. Vitamin E (Vit E) (100 mg/kg body weight) treatment of a batch of lead-injected mice had a similar effect as Vit C but with a comparatively lower efficacy. On the other hand, coadministration of both vitamins (Vit C + Vit E) at the above mentioned doses to lead-treated mice led to the most significant decline in malondialdehyde content along with elevated sperm count and reduction in the percentage of abnormal sperm population. The protective action and the synergistic action of both vitamins (C and E) against lead-induced genotoxicity are discussed.

Final report on the safety assessment of BHT(1)

BHT is the recognized name in the cosmetics industry for butylated hydroxytoluene. BHT is used in a wide range of cosmetic formulations as an antioxidant at concentrations from 0.0002% to 0.5%. BHT does penetrate the skin, but the relatively low amount absorbed remains primarily in the skin. Oral studies demonstrate that BHT is metabolized. The major metabolites appear as the carboxylic acid of BHT and its glucuronide in urine. At acute doses of 0.5 to 1.0 g/kg, some renal and hepatic damage was seen in male rats. Short-term repeated exposure to comparable doses produced hepatic toxic effects in male and female rats. Subchronic feeding and intraperitoneal studies in rats with BHT at lower doses produced increased liver weight, and decreased activity of several hepatic enzymes. In addition to liver and kidney effects, BHT applied to the skin was associated with toxic effects in lung tissue. BHT was not a reproductive or developmental toxin in animals. BHT has been found to enhance and to inhibit the humoral immune response in animals. BHT itself was not generally considered genotoxic, although it did modify the genotoxicity of other agents. BHT has been associated with hepatocellular and pulmonary adenomas in animals, but was not considered carcinogenic and actually was associated with a decreased incidence of neoplasms. BHT has been shown to have tumor promotion effects, to be anticarcinogenic, and to have no effect on other carcinogenic agents, depending on the target organ, exposure parameters, the carcinogen, and the animal tested. Various mechanism studies suggested that BHT toxicity is related to an electrophillic metabolite. In a predictive clinical test, 100% BHT was a mild irritant and a moderate sensitizer. In provocative skin tests, BHT (in the 1% to 2% concentration range) produced positive reactions in a small number of patients. Clinical testing did not find any depigmentation associated with dermal exposure to BHT, although a few case reports of depigmentation were found. The Cosmetic Ingredient Review Expert Panel recognized that oral exposure to BHT was associated with toxic effects in some studies and was negative in others. BHT applied to the skin, however, appears to remain in the skin or pass through only slowly and does not produce systemic exposures to BHT or its metabolites seen with oral exposures. Although there were only limited studies that evaluated the effect of BHT on the skin, the available studies, along with the case literature, demonstrate no significant irritation, sensitization, or photosensitization. Recognizing the low concentration at which this ingredient is currently used in cosmetic formulations, it was concluded that BHT is safe as used in cosmetic formulations.

Efficacy of vitamin-C (L-ascorbic acid) in reducing genotoxicity in fish (Oreochromis mossambicus) induced by ethyl methane sulphonate

The genotoxic effects of ethyl methane sulphonate (EMS) have been assessed in a fish, Oreochromis mossambicus with endpoints including chromosome aberrations, abnormal red blood cell nuclei, abnormal sperm morphology, and protein content (both qualitative and quantitative) of selected tissues, namely, muscle, heart, eye, brain, gill, liver, spleen and kidney. EMS caused chromosomal aberrations, nuclear anomalies in red blood cells, abnormal sperm morphology, and alteration of protein synthesis in various tissues. Some of the EMS toxicity appeared to be modulated and ameliorated in this fish by vitamin-C treatment.

Anticlastogenicity of two derivatives of 1,4-dihydroisonicotinic acid in mouse micronucleus test

Effects of two derivatives of 1,4-dihydroisonicotinic acid (1,4-DHINA) against the monofunctional alkylating agent ethyl methanesulfonate (EMS) were studied in the micronucleus test in (CBA x C57Bl/6(j)) mice. Adult males and pregnant females were treated with an antimutagen (i.p.) and 12h later they were exposed to EMS (i.p.). The frequencies of micronucleated (MN) polychromatic erythrocytes (PCEs) in mouse bone marrow and foetal liver were analysed 6, 12, 18, 24, 30, 36, 48 or 24, 48 and 72 h after the mutagen injection. In adults, the maximum number of MNPCEs was observed 36 or 24h after the EMS administration. In foetuses, which were treated in a maternal organism, such peak was found at 24h. Pre-treatment of mice with the antimutagens 2,6-dimethyl-3,5-diethoxycarbonyl-4-(Na carboxylate)-1,4-dihydropyridine (DHP) and glutapyrone (GP) decreased the yield of MNPCEs in male bone marrow. Having been observed at a peak of MN induction, the anticlastogenic effect of DHP (1/10 LD(50) or 340 mg/kg) reached 30%. DHP at the doses of 0.5-1mM/kg did not affect the EMS-induced frequency of MNPCEs in bone marrow, whereas GP inhibited it at the similar millimolar concentrations. Simultaneously with maternal bone marrow, foetal liver cells were analysed for MNs in the transplacental test. The anticlastogenic effect of DHP (1/10 LD(50)) was found to be more prolonged and higher in females than in males and to average 50%, but this antimutagen was not efficient in foetuses. Both antimutagens did not change the polychromatic/normochromatic erythrocyte (PCE/NCE) ratio as compared with EMS action. Results presented indicate a peak of EMS-induced micronucleated cells in mouse bone marrow 24 or 36 h and in foetal liver 24h after animal treatment. Two 1,4-DHINA derivatives exhibited anticlastogenic activity in adults, but not in foetuses.

Antimutagenic effect of one variety of green pepper (Capsicum spp.) and its possible interference with the nitrosation process

It is known that the poblano green pepper, a significant component in the Mexican diet, contains certain natural compounds such as chlorophyll, beta-carotene, and vitamins, which have antimutagenic and/or anticarcinogenic properties. Using the somatic mutation and recombination test in wing cells of Drosophila melanogaster, an extract of the poblano pepper (Capsicum spp.) was evaluated to determine its antimutagenic effect against the nitrosation process, simulating the process occurring in the human stomach caused by known food additives. Larvae of 72h old D. melanogaster of standard (ST) and high bioactivation (HB) crosses were exposed in a simultaneous, chronic treatment with the juice expressed from the crushed, whole, fresh pepper fruit, plus the mixture of 20mM methyl urea (MU) and sodium nitrite (SN), mixed with the animals' food. Three doses of pepper juice (12.5, 25, and 50%) were used. The background mutation rate given as spots per wing was 0.36 and 0.48 for ST and HB, respectively. Mutation frequencies produced by the MU and SN mixture was 1.73 (ST) and 26.46 (HB) mutations per wing. The poblano juice decreased the above rates between 40 and 80%, respectively. The experiments suggest that some compounds present in the green pepper may cause this antimutagenic effect by interfering with the nitrosation process. The role of the extract and one of its components, such as vitamin C, in the nitrosation process will be discussed.

Modulation of ochratoxin-produced genotoxicity in mice by vitamin C

Ochratoxin A (OA), when administered orally daily for 45 days to albino Swiss mice, Mus musculus, at a level equivalent to the human dietary concentration of 1 microgram/kg body weight/day, increased the production of abnormalities in both mitotic and meiotic chromosomes as well as in the gross morphology of the sperm head. The sperm count per unit volume of caput epididymal suspension also decreased. Vitamin C at a concentration equivalent to the human therapeutic dose (10 mg/kg body weight/day), when administered orally concurrently with OA, significantly minimized the incidence of these abnormalities. The protective effect of vitamin C was most marked in mitotic chromosomes followed by that in meiotic chromosomes and sperm head morphology; the improvement in sperm count was least marked. The possible mechanism of this effect is discussed.