Anticlastogenic activity of beta-carotene against cyclophosphamide in mice in vivo

Enhanced cytotoxic activity of beta carotene conjugated liposomes towards breast cancer cell line: comparative studies with cyclophosphamide

This work aims to evaluate cyclophosphamide (Cyclo) cytotoxic efficacy combined with liposomes in the presence or absence of beta carotene (beta) by detecting the effects of these compounds on the breast cancer cell line (MCF-7) DNA damage. The IC50 value for beta in cytotoxic assay with MCF-7 treated cells was 21.15 μg/ml, while with liposomal beta (LipoBeta) being 121 μg/ml. The free Cyclo IC50 value was 719.86 μg/ml, its liposomal form (LipoCyclo) was 172 μg/ml. The results indicated that in contrast with Cyclo and control values, all comet assay parameters for the LipoBeta were significantly increased (P < 0.05). In MCF-7 cells treated with beta, the findings show a higher intensity of comet tail than those treated with LipoBeta. The presence of several double-strand breaks suggests this high intensity relative to the head. The molecular combination between Cyclo and liposomes in the presence or absence of beta was characterized. Dynamic light scattering measurements confirmed the mono-dispersity of all samples. The incorporation of Cyclo or beta into liposomes exhibited a slight shift to higher temperature compared to the main peak of empty liposomes that exists at 101.5°C which creates a conformational disorder within the phospholipids. The FTIR study showed structural alterations in vesicles after liposome encapsulation.

Micronuclei in diabetes: Folate supplementation diminishes micronuclei in diabetic patients but not in an animal model

Diabetes mellitus (DM) is associated with a high risk of health complications, mainly due to excessive free radical (FRs) production that could result in an increased frequency of micronuclei. The consumption of antioxidants, like folic acid (FA), may mitigate the effects of the FRs. In the present study, micronucleated polychromatic erythrocyte (MNPCE) frequencies were determined in blood sampled weekly from the tails of pregnant female Wistar rats and pregnant Wistar rats with experimental diabetes that were given unsupplemented diets and diets supplemented with FA. At birth, the pups were sampled to analyze micronucleated erythrocyte (MNE) and MNPCE frequencies. Moreover micronucleated cells (MNCs) were evaluated in buccal mucosa samples taken from 81 healthy adult subjects, 48 patients with DM, and 30 DM patients who were sampled before and after FA treatment. Increases in MNPCE frequencies were significant only at the first sampling (P<0.01 and P<0.03) in pregnant rats with experimental diabetes. In addition, the pups from the diabetic group and from diabetic group treated with FA had higher frequencies of MNEs (P<0.03 and P<0.001, respectively) and MNPCEs (P<0.009 and P<0.05, respectively) than the controls. No differences were found in diabetic rats and newborn rats born to diabetic mothers treated with FA compared with untreated animals. Patients with DM had a higher frequency of MNCs compared with healthy subjects (P<0.001). Also FA reduced the frequency of MNCs in DM patients (P<0.001). The results of this study indicate that diabetes results in elevated frequencies of micronuclei, and that, at least in humans, FA can protect against the elevation.

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.

Sanguinarine: an evaluation of in vivo cytogenetic activity

Sanguinarine (SG), a benzophenanthridine alkaloid, has been shown to possess anti-microbial, anti-inflammatory and antioxidant properties. In the UK and USA its salts has been in use in mouthwashes and toothpastes to inhibit dental plaque and improve gingival health. In India and Nepal consumption of mustard oil contaminated with argemone seeds containing sanguinarine, was associated with "dropsy" syndrome. In the present study, SG was evaluated in vivo in mouse bone marrow cells for its ability to induce clastogenicity and DNA damage in terms of increased sister chromatid exchange (SCE) frequencies. Doses of 5, 10, and 15 mg/kg body weight of SG given intra peritoneally induced a positive dose-dependent significant clastogenicity and SCE frequency increases (trend test alpha < or = 0.05). The minimum effective concentration to induce clastogenic and DNA damage was 10mg of SG/kg body weight. In addition to examining SCEs, the BrdUrd-differential technique was utilized to assess the effect of SG on cell replication. The analysis revealed that SG treatment did not significantly affect the distribution of cells among the different phases of the cell cycle. The proliferation rate index and average generation time data were statistically non-significant. This indicated that the alkaloid was not cytotoxic to the bone marrow cells at the doses tested. Based on the results of the present findings, the use of this alkaloid should be restricted.

Ameliorating effect of beta-carotene on ethylmethane sulphonate-induced genotoxicity in the fish Oreochromis mossambicus

Genotoxic effects have been assessed in the fish Oreochromis mossambicus treated separately and conjointly with 0.2% ethylmethane sulphonate (EMS) and 0.05% beta-carotene (BC) during five different time periods (6, 24, 48, 72 and 96 h) by analysis of endpoints such as chromosome aberrations, abnormal red blood cell nuclei, abnormal sperm morphology and protein contents (both qualitative and quantitative) of selected tissues, viz. muscle, heart, eye, brain, gill, liver, spleen and kidney. In addition, the relative efficacy of three doses of BC 0.02, 0.05 and 0.1%, in ameliorating genotoxic effects of 0.2% EMS was also tested after a treatment period of 48 h. EMS caused chromosomal aberrations, nuclear anomalies in red blood cells, abnormal sperm morphology and an apparent alteration of protein synthesis in various tissues. Some of these genotoxic effects of EMS appeared to be ameliorated by all three doses of BC, of which the 0.02% dose showed a marginally better efficacy.

The modifying effect of beta-carotene on gamma radiation-induced elevation of oxidative reactions and genotoxicity in male rats

The aim of the present work was to evaluate the modulatory role of beta-carotene on the radiation-induced changes in certain biochemical and cytogenetic parameters. beta-Carotene was given by gavage at a dose of 5 mg/kg body weight for 7 consecutive days before whole body gamma irradiation with 7 Gy (single dose). The levels of beta-carotene in plasma, thiobarbituric acid-reactive substances (TBARS) in plasma and liver, the activities of superoxide dismutase (SOD) and catalase in blood and liver were the selected parameters. Furthermore, the frequency of micronuclei (MN) of polychromatic erythrocytes (PCEs), normochromatic erythrocytes (NCEs), the ratio of PCEs/NCEs and the mitotic index (MI) of bone marrow cells were also evaluated. The biochemical and cytogenetic determinations were carried out 1, 24, and 72 h after radiation exposure. The results obtained revealed that administration of beta-carotene pre-irradiation significantly inhibited the decrease in plasma beta-carotene, significantly reduced the levels of TBARS in plasma and liver. Significant protection of the radiation-induced changes in the activities of SOD and catalase was also recorded in the blood and liver of beta-carotene-treated and -irradiated rats. beta-Carotene resulted in significant inhibition in the frequency of radiation-induced MN, as well as in the ratio of PCEs/NCEs and the MI of bone marrow cells. These results suggest that beta-carotene as a natural product with its antioxidant capacity and capability of quenching singlet oxygen, could play a modulatory role against the cellular damage affected by free radicals induced by whole body irradiation.

Transplacental inhibitory effect of carrot juice on the clastogenicity of cyclophosphamide in mice

Genetic damage during the prenatal period can provoke important neoplastic alterations and other diseases in postnatal life. Beta-carotene (ßC) is considered to be one of the most important anticarcinogens in the diet and can protect mammalian cells against genotoxic events. As carrots are important dietary source of ßC, we decided to test the effect of fresh carrot juice (CaJ) on cyclophosphamide (CP)-induced genotoxicity in maternal and fetal erythropoietic tissues. The treatment with CaJ started on the 7th day of the pregnancy of BALB/c female mice. We observed, on the 16th gestational day, that this treatment did not modify the spontaneous frequency of micronucleated polychromatic erythrocytes (mPCE) in the bone marrow of the females nor in the livers of their fetuses. The mPCE frequency observed 24 h after an intraperitoneal injection of CP (40 mg/kg) on the 15th day was significantly lower in CaJ-pretreated pregnant female bone marrow and in the liver of their fetuses than those observed in the group treated with CP only. These results demonstrate the presence of natural anticlastogens in carrots.

In vivo anticlastogenic effects of L-ascorbic acid in mice

The effects of l-ascorbic acid on the frequency of micronuclei induced by model mutagens, cyclophosphamide (CP), mitomycin-C (MMC) and bleomycin (BLM) hydrochloride were tested using mouse bone marrow. Three doses of ascorbic acid (AsA) viz., 10, 30 and 60 mg/kg b.w. were tested for anticlastogenic effects. The doses of positive mutagens used were, CP-50 mg/kg, MMC-4 mg/kg and BLM-20 mg/kg b.w. Bone marrow sampling was done at 24 h after the treatment. AsA was found to be effective in reducing MN frequency induced by CP and BLM. With MMC only, the highest dose showed a slight inhibitory effect.

Comparative studies on genotoxicity and antigenotoxicity of natural and synthetic beta-carotene stereoisomers

To evaluate the practical value of natural beta-carotene (NbetaC) and to elucidate the apparent discrepancy between epidemiological observations and intervention trials on the role of beta-carotene (betaC) in tumor prevention, the genotoxicity and the antigenotoxicity of NbetaC and synthetic betaC crystal (SbetaCC) stereoisomers were studied comparatively using chromosome aberration analysis and the micronucleus test in human lymphocytes in vitro. NbetaC was extracted from the halotolerant algae Dunaliella salina. The NbetaC crystal (NbetaCC) preparation is about 70% all-trans (TbetaC) and 8% 9-cis (CbetaC). The NbetaC oil (NbetaCO) preparation is about 40% all-trans and 38% 9-cis. SbetaCC is more than 97% all-trans, and the 9-cis can not be detected. The mixture of betaC (betaCM) preparation is 74% SbetaCC and 26% NbetaC. Our results show no genotoxicity of 1-30 microg/ml NbetaCC, but this concentration of NbetaCC inhibited significantly gamma-ray-induced micronucleus formation in human lymphocytes in vitro. One to thirty microg/ml NbetaCO was most effective against both gamma-ray-induced and spontaneous micronucleus formation. However, no influence of NbetaCO on spontaneous chromosome aberrations in human lymphocytes in vitro was observed. NbetaCO suppressed significantly mitomycin C (MMC)-induced chromosome aberrations. One to thirty microg/ml SbetaCC induced a dose-dependent increase in micronucleus frequency, and also inhibited gamma-ray-induced micronucleus formation. No effect of betaCM on spontaneous chromosome aberrations was found. One to thirty microg/ml betaCM is more effective against MMC-induced chromosome aberrations than NbetaCO. These results suggest that CbetaC might play a critical role in the genotoxicity and antigenotoxicity of SbetaCC and NbetaC. The genotoxic activity of SbetaCC might be involved in carcinogenesis. NbetaC or betaCM could be of practical value in tumor prevention and supplementary treatment.

Protective effects of fruits and vegetables against in vivo clastogenicity of cyclosphosphamide or benzo[a]pyrene in mice

Seven fruits and 10 vegetables commonly consumed in Germany were investigated for their anticlastogenic potencies against cyclophosphamide (CP) and benzo[a]pyrene (BaP) in the in vivo mouse bone marrow micronucleus assay. We detected protective effects in 76.5% and 70.6% of the samples, respectively, and more or less distinct quantitative differences between the various plant materials and the two clastogens investigated. With respect to CP, moderate activities were exerted by sweet cherries, strawberries, cucumber, radish and tomatoes, average activities by bananas, oranges, peaches, asparagus and red beets and strong activities by yellow red peppers and especially spinach. Apples (cultivar Jona Gold), brussels sprouts, cauliflower and onions were inactive. With respect to BaP, we found moderate activities in strawberries, brussels sprouts and radish, average activities in sweet cherries, oranges, peaches, asparagus, red beets, cucumber and spinach and strong activities in bananas and kiwi. Apples, cauliflower, onions, tomatoes and yellow-red peppers were inactive. When oranges were fractionated according to previously described schemes (Edenharder et al., 1995), anticlastogenic activities against CP were exerted by materials extracted with n-hexane, acetone and 2-propanol and in the terminal residue, but not in the dichloromethane and water phases. With respect to BaP, materials extracted with acetone showed strong anticlastogenicity while the 2-propanol fraction, the aqueous phase and the terminal residue were less potent. The n-hexane and the dichloromethane fractions were inactive. In red beets, all fractions showed anticlastogenicity against CP and BaP as well. However, the n-hexane and dichloromethane fractions were most potent with respect to CP, while for BaP the aqueous phase and the terminal residue were most effective. These result suggest the presence of various (groups of) anticlastogenic compounds with different chemical structure.

Inhibition of genotoxic effects of mammalian germ cell mutagens

Germ cell mutagens are among the most important chemicals for which chemopreventive agents should be sought and mechanistically defined. These mutagens may include environmental chemicals as well as drugs. In this investigation, the literature was reviewed for substances antimutagenic (or anticlastogenic) to compounds identified as mutagens in at least two germ cell studies. A complete matrix of test results was prepared to identify commonly tested pairs of germ cell mutagens and antimutagens. The categories of antimutagens most tested included vitamins, fatty acids, thiols, tannins and other phenolics. The most frequently studied mutagens were benzo[a]pyrene, cyclophosphamide, mitomycin C, and bleomycin. Based on the availability of the most relevant data, the analysis presented here focused on in vivo tests, specifically on bone marrow cytogenetics. The results indicated that antimutagens commonly found in the diet or endogenously in the body effectively antagonized the cytogenetic damage induced in the bone marrow by most of the germ cell mutagens studied to date. Bone marrow micronucleus and chromosomal aberration assays, which detect systemically active mutagens, may be predictive of similar mitigating effects in germ cells. Test results from antimutagenicity studies in germ cells, though limited, were comparable to the results from studies in the mouse bone marrow micronucleus test.

Effect of selected antimutagens on the genotoxicity of antitumor agents

Cyclophosphamide (CP), bleomycin (BL), doxorubicin (DOX) and cisplatin (CISP) are potent antitumor drugs used worldwide against many forms of human cancer. As with most such agents, there can be physiological side-effects and the possible induction of mutations and other genotoxic effects in non-tumor cells. It is common for patients to ingest a host of food supplements to diminish the discomforting side-effects of therapy. Because these food supplements are often also rich in antimutagens that could also affect the biological efficacy of the antitumor drugs, we investigated if such antimutagenic agents were indeed antimutagenic to these antitumor drugs. Using the Salmonella/microsome bioassay, we tested CP, BL, DOX, and CP for mutagenicity in the presence and absence of the antimutagens ascorbic acid (AA), chlorophyllin (CHL) and (+)-catechin (CAT). AA was a very effective antimutagen against CISP and less effective against BL and DOX. It was not antimutagenic to CP. CHL was effective as an antimutagen against all four antitumor drugs, and CAT was a strong inhibitor of DOX mutagenicity, but had little effect on BL, CP and CISP. These data now provide a basis for future in vivo antitumor/antimutagen combination studies to determine if these antimutagens function in a manner to reduce genetic effects without having concomitant effects on intended antitumorogenicity of these therapeutic agents.

In vitro antimutagenic and in vivo anticlastogenic effects of carotenoids and solvent extracts from fruits and vegetables rich in carotenoids

The water insoluble residues of some carotenoid-rich fruits and vegetables, such as apricots, oranges, brussels sprouts, carrots, yellow-red peppers, and tomatoes, were sequentially extracted with n-hexane, dichloromethane, acetone, and 2-propanol, and solvent extracted materials were tested for inhibition of mutagenicities induced by aflatoxin B1 (AFB1), benzo[a]pyrene (BaP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and cyclophosphamide (CP) in histidine-deficient strains of Salmonella typhimurium. Antimutagenic activities were found in many extracts, but especially in the n-hexane extracts. For example, in the case of oranges, 100 microg of this extract reduced the bacterial mutagenicity of AFB1, BaP, CP and IQ by 72, 67, 53, and 27%, respectively. Separation by semi-preparative HPLC of the n-hexane extracts of carrots, tomatoes, and oranges indicated that the antimutagenicity was mainly associated with the fractions of the hydrocarbon carotenoids (alpha-, beta-carotene, lycopene), the xanthophylls (beta-cryptoxanthin, lutein), and also the carotenolesters (oranges). When 16 reference carotenoids were investigated as described above, the following results were obtained: In the case of BaP, antimutagenic activity, quantified by dose-response curves, was exhibited by 8'-apo-beta-carotenal, alpha- and beta-carotene, beta-cryptoxanthin, lutein, retinal, and retinol (ID50-values: 20-100 nmol ml-1 top agar, 50-70% maximum inhibition at 1 micromol ml-1 top agar), while the maximum inhibition by torularhodin did not exceed 40%. Astaxanthin, 10'- and 12'-apo-beta-carotenal, bixin, canthaxanthin, ethyl-8'-apo-beta-caro-ten-8'-oate, lycopene, and zeaxanthin were inactive or at best marginally active (<20% inhibition). Closely similar results were obtained with AFB1. The bacterial mutagenicity of CP was strongly reduced by alpha- and beta-carotene, canthaxanthin, and retinol (ID50-values: 67-112 nmol ml-1 top agar, 50-63% maximum inhibition at 1 micromol ml-1 top agar), moderately by beta-cryptoxanthin, and lutein (45% and 28%, respectively), and only marginally or, not at all, by all remaining carotenoids. In the case of IQ, the carotenoids exhibited the weakest antimutagenic potency (7-43%, ID50-values of retinal and retinol: 160 and 189 nmol ml-1 top agar, 60% and 55% inhibition, respectively). The mutagenic activity of the proximal mutagen of IQ, N-OH-IQ, in S. typhimurium TA 98NR was not significantly reduced by any carotenoid tested. These observations as well as the inhibition of various cytochrome P-450 linked 7-alkoxyresorufin-O-dealkylase activities (EROD, MROD, PROD) by four selected carotenoids (retinol>beta-cryptoxanthin>beta-carotene>lutein, IC50-values: 19-109 microM), indicate that the inhibition of the metabolic activation of the different promutagens could cause antimutagenicity. Finally, it could be demonstrated that the number of BaP or CP induced micronuclei in polychromatic erythrocytes in bone-marrow of mice was reduced significantly by the carotenoids lycopene, canthaxanthin, lutein and beta-cryptoxanthin (25-46%). These results clearly show that carotenoids possess biological activities in vitro and in vivo distinct from their function as precursors of vitamin A or antioxidants suggesting effects on activation of promutagens.

The influence of two carotenoid food dyes on clastogenic activities of cyclophosphamide and dioxidine in mice

The influence of the food dyes E160e (beta-apo-8'-carotenal in an oil suspension) and E160a (beta-carotene in an oil suspension) on clastogenic effects of cyclophosphamide (CP) and dioxidine (DN) was investigated. Chromosome damage in the bone marrow of C57BL/6 mice was reported. The following protocols were used: (1) simultaneous single administration of the dye and the mutagen and the subsequent animal sacrifice within 24 hr; (2) a 4-day pretreatment with the dye (daily administrations) followed with simultaneous injection of the dye and the mutagen on the 5th day 24 hr before sacrifice; (3) daily co-administration of the dye and the mutagen for 5 days with sacrifice 6 hr after the last administration. CP at a dose of 30 mg/kg and DN at 300 mg/kg were injected intraperitoneally; the dyes at doses of 0.5, 5 and 50 mg/kg were given orally. Under all the protocols applied, E160e at a dose of 50 mg/kg caused a significant reduction of both DN and CP effects. At 5 mg/kg this dye reduced the effects of the mutagens only under the pretreatment regimen. Pretreatment with E160a at doses of 5 and 50 mg/kg resulted in a meaningful reduction of the DN effect. Under the combined treatment with mutagens this dye reduced both CP and DN effects.

Vitamins as antimutagens: advantages and some possible mechanisms of antimutagenic action

Dietary natural inhibitors of mutagenesis and carcinogenesis are of particular importance because they may be useful for human cancer prevention and do not have undesirable xenobiotic effects on living organisms. As was shown in numerous experiments, many endogenous substances, usually obtained in food or synthesized by cells, possess some inhibitory activity towards natural or man-made environmental mutagens which often induce increased frequency of cancer. Among such substances are vitamins, thiol compounds, porphyrin derivatives, polyphenols and others, the antigenotoxicity of which is well established in various genetic tests. Probably a number of these compounds are included in the defense systems of organisms protecting them from harmful exogenous influences continuously affecting genetic material and other components of cells. Some vitamins show protective effects; for example, E, A and C vitamins are active against well-known mutagens both in vitro and in vivo. Genetic properties of other vitamins have been insufficiently explored, but positive results were obtained for a number of them suggesting the desirability of further studies in this field. Synergism of some vitamins activity, both with other vitamins and non-vitamin substances, is of particular interest because clarifying some of their mechanisms of action could be important for understanding the functions of our defense systems.

Effects of provitamin A or non-provitamin A carotenoids on liver xenobiotic-metabolizing enzymes in mice

To determine whether carotenoids can modulate xenobiotic-metabolizing enzymes in mice, catalytic activities of several phase I and phase II enzymes have been measured in liver microsomes and cytosol of male Swiss mice fed diets containing beta-carotene, beta-apo-8'-carotenal, canthaxanthin, or astaxanthin (300 mg/kg diet) or treated with 3-methylcholanthrene (3-MC) (3 times at 50 mg/kg ip) for 15 days. Canthaxanthin increased CYP 1A-dependent activities: ethoxyresorufin O-deethylase (EROD) was increased 3-fold, pentoxyresorufin dealkylase (PROD) was increased 2.5-fold, and methoxyresorufin O-demethylase (MROD) was increased 1.6-fold; these increases were much less than those induced by 3-MC, which induced EROD 49-fold, PROD 10-fold, and MROD 4-fold. 3-MC, but not canthaxanthin, also increased relative liver weight, liver P-450 content, NADH-cytochrome c reductase, and benzoxyresorufin dearylase. The three other carotenoids had little or no effect on phase I enzymes. Among the phase II enzyme activities, only NADPH-quinone reductase was slightly increased by 3-MC and carotenoids, except beta-carotene. Among the three carotenoids that have previously been found to be powerful CYP 1A inducers in the rat, i.e., canthaxanthin, astaxanthin, and beta-apo-8'-carotenal, only canthaxanthin shows some (weak) inducing effect of CYP 1A in the 3-MC-responsive Swiss mice, indicating that the mechanism of CYP 1A induction by carotenoids may not be the same as that by 3-MC. In addition, the fact that beta-carotene has no effect on the tested enzymes does not support the hypothesis that the modulation of xenobiotic metabolism is a possible mechanism for the antimutagenic and anticarcinogenic effects of beta-carotene, which have been demonstrated in several in vivo models in mice.

Phenethyl isothiocyanate modulates clastogenicity of mitomycin C and cyclophosphamide in vivo

Phenethyl isothiocyanate (PEITC), a constituent of many cruciferous vegetables, is an effective chemopreventive agent against N-nitrosamine-induced carcinogenesis. We have investigated the extent to which PEITC modulates the clastogenicity of standard genotoxicants, mitomycin C and cyclophosphamide, using bone marrow cells of Swiss albino mice. PEITC, 1 mumol/kg body weight in corn oil was administered by gavage for 7 consecutive days to prime the animals. 24 h later, mice received a single dose of cyclophosphamide (10 or 20 mg/kg body weight) or mitomycin C (1 or 2 mg/kg body weight) intraperitoneally. Clastogenicity of the chemicals was compared using PEITC-primed and non-primed animals 24 h after clastogen treatment. As a single agent, PEITC is not clastogenic even after 7 days of priming. Oral priming with PEITC decreased the aberrations per cell values by 22-67% in all cases. PEITC could only alleviate the clastogenicity of 1 mg/kg body weight mitomycin C to near-control values (p < or = 0.05). Although PEITC is reported to be effective against N-nitrosamine-induced tumorigenesis by preventing metabolic activation and by blocking the reactive species formed, it is virtually ineffective against the clastogenicity of cyclophosphamide. The results of inhibition by PEITC of the clastogenicity of mitomycin C suggest that the modulation of mitomycin C bio-activation contributes to, but may not be sufficient for, PEITC chemoprevention of clastogenicity by mitomycin C.

Radioprotection of beta-carotene evaluated on mouse somatic and germ cells

In the present paper, the protective effect of beta-carotene was evaluated after whole body exposure of mice to 2 Gy of X-rays. Splenocytes, reticulocytes, bone marrow cells and spermatids were evaluated for the frequency of micronuclei (MN) induced by X-rays. Mice were treated (gavage) with beta-carotene (10, 25 and 50 mg/kg b.w.) for 5 consecutive days and, 4 h after the last treatment, the animals were irradiated. The results obtained showed different frequencies of X-ray-induced-MN between different cell populations analysed and also different response of these cells to the beta-carotene treatment. The radioprotective effect of beta-carotene was observed in splenocytes, reticulocytes, and spermatids but not in bone marrow cells. No dose-response relationship for beta-carotene was detected. The time of sampling, the sensitivity of the cells as well as the antioxidant activity of beta-carotene are discussed as important factors for the radioprotective action of this provitamin.

Reduction of clastogenic effect of clofazimine, an antileprosy drug, by vitamin A and vitamin C in bone marrow cells of mice

Clofazimine (CLF), an antileprosy drug, has earlier been proved to be clastogenic in mice in vivo. It is an important constituent of the triple-drug regimen recommended by WHO for the treatment of leprosy. In this study the protective role of vitamins A and C (vit A and vit C) against the clastogenic effect of CLF in mouse bone marrow cells has been evaluated. Two doses (20 and 40 mg/kg) of vit C and two doses (2500 and 5000 IU/kg) of vit A were tested against a dose of 40 mg CLF/kg. The drug alone induced chromosomal aberrations of about 8 times the control value. Neither of the doses of vit C exhibited any clastogenic effect and, when administered simultaneously with CLF, both reduced the effect of CLF very significantly, the higher dose reducing chromosomal aberrations almost to the control value. Conversely, both doses of vit A, when administered alone, brought about significant increases in chromosome aberrations over the control value; the higher, but not the lower dose, given simultaneously with CLF, minimized the effect of CLF significantly but not as greatly as vit C. A scavenging effect of the vitamins, removing free radicals produced by CLF, is assumed to be responsible for modulation of the clastogenic effect of CLF.

In vivo cytogenetic studies on mice exposed to natural food colourings

Safflower Yellow and Kokum Red, two food colourings developed from natural plant products, were assessed in vivo for their clastogenic potential. Swiss albino male mice were exposed to the compounds through ip injections. Bone marrow cells isolated from femora were analysed for chromosome aberrations. The results show that the two food colourings were weakly clastogenic.

Effect of beta-carotene on spontaneous and X-ray-induced chromosomal damage in bone marrow cells of mice

The effect of beta-carotene on spontaneous and X-ray-induced chromosomal damage in bone marrow cells of mice was studied. As a source of beta-carotene, dried Dunaliella bardawil (containing 6% beta-carotene) or oil suspension of Dunaliella beta-carotene was used. In Experiment 1, mice were given a basal diet, a 0.5% Dunaliella diet, or a 4% Dunaliella diet for four weeks. In Experiment 2, mice were given an oil suspension of Dunaliella beta-carotene (300 mg/kg body wt) by gavage for seven days while being fed a fat-rich diet. After beta-carotene treatment for the indicated time, spontaneous and X-ray (0.3 Gy, whole-body)-induced chromosomal damage in bone marrow cells was evaluated in terms of the percentages of micronucleated reticulocytes in their peripheral blood. The beta-carotene treatment slightly lowered the spontaneous and X-ray-induced chromosomal damage in bone marrow cells. Despite the higher doses of beta-carotene, the concentrations of beta-carotene in bone marrow, liver, and serum were much lower than those of vitamin E. In addition, the beta-carotene treatment markedly lowered the concentration of vitamin E in the tissues.

Bone marrow micronucleus assay: a review of the mouse stocks used and their published mean spontaneous micronucleus frequencies

We have examined published negative control data from 581 papers on micronucleated bone marrow polychromatic erythrocytes (mnPCE) for differences in mean frequency and the frequency distribution profile among the mouse stocks used with the bone marrow micronucleus assay. For the 55 mouse stocks with published micronucleus assay data, the overall mean frequency is 1.95 mnPCE/1,000 PCE (1.95 mnPCE/1,000); for the 13 stocks most commonly used in the assay, it is 1.88 mnPCE/1,000. During the last 5 years, the mnPCE rate for these 13 major stocks has been 1.74 mnPCE/1,000. This current mean frequency is a substantial decrease from the mean of 3.07 mnPCE/1,000 observed for these 13 stocks for data published prior to 1981. Of the major stocks, the highest mean mnPCE negative control frequencies were observed for MS/Ae > BALB/c > C57Bl/6, and the lowest for CD-1 < Swiss Webster. We note that hybrid mouse stocks appear to have lower and less variable negative control frequencies than either of their parent strains and that the negative control frequency for some progeny stocks have diverged significantly from that of the parent stocks. Overall mean negative control frequencies appear to be correlated with breadth of the frequency distribution profile of published mean negative control values. Furthermore, a possible correlation between negative control frequency in the micronucleus assay and sensitivity to clastogens of different mouse strains may be indicated. The databases generated here allow us to define a range of norms for both the historical mean frequency and individual experimental mean frequencies for most stocks, but in particular, for the more commonly used mouse stocks. Our analysis, for the most part, bears out the recommendation of the first Gene-Tox Report on the micronucleus assay that the historical negative control frequency for a mouse stock should fall between 1 and 3 mnPCE/1,000. Eighty-six percent of the most commonly used mouse stocks have historical mean frequencies within this range. Though individual experimental mean values would not necessarily be expected to fall within the 1-3.00 mnPCE/1,000 range, 65.3% of the 2,327 published negative control values do, and 83.5% are < 3 mnPCE/1,000. The frequency with which an individual experimental mean value lies outside the 1.00 to 3.00 mnPCE/1,000 range differs among stocks and appears related to the mouse mean frequency. We suggest that the recommended range for historical mean frequency be extended slightly, to approximately 3.4 mnPCE/1,000, to accommodate some commonly used strains with overall mean negative control frequencies just above 3.00 mnPCE/1,000.(ABSTRACT TRUNCATED AT 400 WORDS)

Cancer-protective factors in fruits and vegetables: biochemical and biological background

Cancer-protective factors are present in several fruits, vegetables and commonly used spices and herbs. They can be divided into several different groups, based on their chemical structure, e.g. polyphenols, thiols, carotenoids and retinoids, carbohydrates, trace metals, terpenes, tocopherols and degradation products of glucosinolates (i.e. isothiocyanates, indoles and dithiothiols) and others. Among each of these groups of compounds are substances, which may exert their cancer-protective action by more than one biochemical mechanism. The biochemical processes of carcinogenesis are still not known in detail and probably varies with the cancer disease in question. Accordingly, the description of the biochemical backgrounds for the actions of cancer-protective factors must be based on a simplified model of the process of carcinogenesis. The model used in this presentation is a generalised initiation-promotion-conversion model, in which initiators are thought to be directly or indirectly genotoxic, promoters are visualised as substances capable of inferring a growth advantage on initiated cells and converters are believed to be genotoxic, e.g. mutagens, clastogens, recombinogens or the like. Experimental evidence for the mechanisms of action of cancer-protective agents in fruits and vegetables that protect against initiation include the scavenging effects of polyphenols on activated mutagens and carcinogens, the quenching of singlet oxygen and radicals by carotenoids, the antioxidant effects of many compounds including ascorbic acid and polyphenols, the inhibition of activating enzymes by some flavonols and tannins, the induction of oxidation- and of conjugation (protective) enzymes by indoles, isothiocyanates and dithiothiones, the shielding of sensitive structures by some polyphenols and the stimulation of DNA-repair exerted by sulphur-containing compounds. Mechanisms at the biochemical level in anti-promotion include the antioxidant effects of carotenoids and the membrane stabilizing effects reported with polyphenols, the inhibition of proteases caused by compounds from soybeans, the stimulation of immune responses seen with carotenoids and ascorbic acid and the inhibition of ornithine decarboxylase by polyphenols and carotenoids. A few inhibitors of conversion have been identified experimentally, and it can be argued on a theoretical basis, that many inhibitors of initiation should also be efficient against conversion. The mechanisms of anticarcinogenic substances in fruits and vegetables are discussed in the light of cancer prevention and inhibition.