Effect of selected antimutagens on the genotoxicity of antitumor agents

Role of flavonoids against adriamycin toxicity

Doxorubicin (DOX), or adriamycin, is an anthracycline antineoplastic drug widely used in the chemotherapy of a large variety of cancers due to its potency and action spectrum. However, its use is limited by the toxicity on healthy cells and its acute and chronic side effects. One of the developed strategies to attenuate DOX toxicity is the combined therapy with bioactive compounds such as flavonoids. This review embraces the role of flavonoids on DOX treatment side effects. Protective properties of some flavonoidss against DOX toxicity have been investigated and observed mainly in heart but also in liver, kidney, brain, testis or bone marrow. Protective mechanisms involve reduction of oxidative stress by decrease of ROS levels and/or increase antioxidant defenses and interferences with autophagy, apoptosis and inflammation. Studies in cancer cells have reported that the anticancer activity of DOX was not compromised by the flavonoids. Moreover, some of them increased DOX efficiency as anti-cancer drug even in multidrug resistant cells.

The Protective Effect of Naringenin on Oxaliplatin-Induced Genotoxicity in Mice

Oxaliplatin is a third generation platinum based anti-cancer drug used against various human malignancies but displays genotoxic properties against normal cells. Naringenin is a naturally occurring bioflavonoid that possesses anti-oxidant properties and has protective effects against DNA damage. The aim of this study is to examine the protective effects of naringenin on oxaliplatin-induced DNA damage in mice. A total of 50, male BALB/c mice were randomly divided equally into five groups. Oxaliplatin toxicity was induced by a single dose (7 mg/kg body weight (b.w.)) injection (intraperitoneally (i.p.)) of oxaliplatin. Naringenin was given orally for ten consecutive days at two doses, 20 mg/kg b.w. (dose I) and 40 mg/kg b.w. (dose II), to group I and group II, respectively. On the tenth day of the experiment, animals in groups III, IV, and V were given a single i.p. injection of oxaliplatin (7 mg/kg b.w.). All the animals were sacrificed 24 h after oxaliplatin treatment. The extent of genotoxicity was assessed by multiple genotoxicity assays (8-hydroxydeoxy-guanosine marker, comet, micronucleus and chromosomal aberration assays, oxidative stress-marker Glutathione evaluation) in order to determine diverse kinds of DNA damage. The results indicated that naringenin administration significantly reduced the DNA damage induced by oxaliplatin possibly due to its strong anti-oxidant properties. The results suggest that naringenin is a potential candidate for future development as a chemoprotective agent against chemotherapy associated complications.

Antimutagenic activity of ipriflavone against the DNA-damage induced by cyclophosphamide in mice

In the present study we evaluated the potential of ipriflavone against the cytotoxic and mutagenic effects induced by cyclophosphamide chemotherapeutic agent in bone marrow cells of mice, using the micronucleus assay in vivo on cells of bone marrow. The study was performed following three protocols: pre-treatment, simultaneous treatment and post treatment. The results demonstrated that ipriflavone has a protective effect against mutagenicity induced by cyclophosphamide in the pre-treatment and post-treatment and against the cytotoxicity in all treatments. There was variation between the genders in some of the experimental groups. To evaluate their possible mechanisms of action, it was performed the DPPH assay, which showed no ability to donate hydrogens, suggesting that it acts through other mechanisms. Due to its ability to prevent chromosomal damage, ipriflavone is likely to open an interest field concerning its possible the use in clinical applications.

Antimutagenic and antirecombinagenic activities of noni fruit juice in somatic cells of Drosophila melanogaster

Noni, a Hawaiian name for the fruit of Morinda citrifolia L., is a traditional medicinal plant from Polynesia widely used for the treatment of many diseases including arthritis, diabetes, asthma, hypertension and cancer. Here, a commercial noni juice (TNJ) was evaluated for its protective activities against the lesions induced by mitomycin C (MMC) and doxorrubicin (DXR) using the Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. Three-day-old larvae, trans-heterozygous for two genetic markers (mwh and flr3 ), were co-treated with TNJ plus MMC or DXR. We have observed a reduction in genotoxic effects of MMC and DXR caused by the juice. TNJ provoked a marked decrease in all kinds of MMC- and DXR-induced mutant spots, mainly due to its antirecombinagenic activity. The TNJ protective effects were concentration-dependent, indicating a dose-response correlation, that can be attributed to a powerful antioxidant and/or free radical scavenger ability of TNJ.

Sesamol prevents doxorubicin-induced oxidative damage and toxicity on H9c2 cardiomyoblasts

Objectives

Exposure to toxicants like doxorubicin (Dox) damages cellular components by generating reactive oxygen species (ROS). This can be attenuated using free radical scavengers and/or antioxidants.

Methods

Dox-exposed cardiac myoblasts (H9c2 cells) were treated with sesamol (12.5, 25 and 50 μm), a natural phenolic compound. Intracellular ROS inhibition, cell viability and analysis of antioxidant and biochemical markers such as superoxide dismutase, catalase, glutathione-S-transferase, glutathione peroxidase, reduced/oxidized glutathione, lipid peroxidation and protein carbonyl content were performed. The effect of sesamol treatment on the cytotoxic and genotoxic parameters was studied by monitoring the signalling proteins involved in the apoptotic pathway.

Key findings

Dox triggered cellular and genetic damage by increasing levels of intracellular ROS, thereby decreasing cell viability and increasing apoptosis. Sesamol reversed the cytotoxic and genotoxic effects of Dox. In addition, sesamol attenuated the pro-apoptotic proteins and improved the anti-apoptotic status. Sesamol pre-treatment also alleviated the disturbed antioxidant milieu by preventing ROS production and improving endogenous enzyme levels.

Conclusions

Among the different doses tested, 50 μm of sesamol showed maximum protection against Dox-induced oxidative damage. This reflects the significance of sesamol in ameliorating the deleterious effects associated with cancer chemotherapy.

Antigenotoxic effect of lipoic acid against mitomycin-C in human lymphocyte cultures

Antitumor agents are used in therapy against many forms of human cancer. One of these is mitomycin-C (MMC). As with many agents, it can interact with biological molecules and can induce genetic hazards in non-tumor cells. One of the possible approaches to protect DNA from this damage is to supply antioxidants that can remove free radicals produced by antitumor agents. Lipoic acid (LA) is known as one of the most powerful antioxidants. The aim of this study was to investigate antigenotoxic effects of LA against MMC induced chromosomal aberrations (CA), sister chromatid exchanges (SCE) and micronucleus (MN) formation in human lymphocytes. Lymphocytes were treated with 0.2 μg MMC/heparinized mL for 48 h. Three different concentrations (0.5, 1, 2 μg/mL) of LA were used together with MMC in three different applications; 1 h pre-treatment, simultaneous treatment and 1 h post-treatment. A negative, a positive and a solvent control were also included. In all the cultures treated with MMC + LA, the frequency of abnormal cells and CA/cell significantly decreased compared to MMC. Statistically significant reduction was also observed in SCE/cell and MN frequencies in all treatments. These results demonstrated anticlastogenic and antimutagenic effects of LA against MMC induced genotoxicity. LA showed the most efficient effect during 1 h pretreatment. On the other hand, MMC + LA treatments induced significant reduction in mitotic index than that of MMC treatment alone. These results are encouraging that LA can be a possible chemopreventive agent in tumorigenesis in both cancer patients and in health care persons handling anti-cancer drugs.

Gallic Acid Enriched Fraction of Phyllanthus emblica Potentiates Indomethacin-Induced Gastric Ulcer Healing via e-NOS-Dependent Pathway

The healing activity of gallic acid enriched ethanolic extract (GAE) of Phyllanthus emblica fruits (amla) against the indomethacin-induced gastric ulceration in mice was investigated. The activity was correlated with the ability of GAE to alter the cyclooxygenase- (COX-) dependent healing pathways. Histology of the stomach tissues revealed maximum ulceration on the 3rd day after indomethacin (18 mg/kg, single dose) administration that was associated with significant increase in inflammatory factors, namely, mucosal myeloperoxidase (MPO) activity and inducible nitric oxide synthase (i-NOS) expression. Proangiogenic parameters such as the levels of prostaglandin (PG) E₂, vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), von Willebrand Factor VIII, and endothelial NOS (e-NOS) were downregulated by indomethacin. Treatment with GAE (5 mg/kg/day) and omeprazole (3 mg/kg/day) for 3 days led to effective healing of the acute ulceration, while GAE could reverse the indomethacin-induced proinflammatory changes of the designated biochemical parameters. The ulcer healing activity of GAE was, however, compromised by coadministration of the nonspecific NOS inhibitor, N-nitro-L-arginine methyl ester (L-NAME), but not the i-NOS-specific inhibitor, L-N6-(1-iminoethyl) lysine hydrochloride (L-NIL). Taken together, these results suggested that the GAE treatment accelerates ulcer healing by inducing PGE₂ synthesis and augmenting e-NOS/i-NOS ratio.

Protective effect of rosmarinic acid on V79 cells evaluated by the micronucleus and comet assays

Rosmarinic acid (RA) is a naturally occurring phenolic compound, which contributes to the beneficial and health-promoting effects of herbs, spices and medicinal plants. RA has shown several biological activities, such as hepatoprotective, anti-inflammatory, antiangiogenic, antitumor, antidepressant, antineurodegenerative, HIV-1 inhibitory and antioxidant effects. The aim of this study was to investigate the ability of RA to prevent chemically induced chromosome breakage or loss and primary DNA damage using the micronucleus and comet assays with V79 cells, respectively. The chemotherapeutic agent doxorubicin (DXR; 0.5 microg ml(-1)) was used as the DNA-damaging agent. The cultures were treated with different concentrations of RA (0.28, 0.56 and 1.12 mm) alone or in combination with DXR. The results showed that RA exerted no genotoxic effect, but significantly reduced the frequency of micronuclei and the extent of DNA damage induced by DXR at the three concentrations tested. The antioxidant activity of RA might be involved in the reduction of DXR-induced DNA damage observed in the present study.

Effect of organic tomato (Lycopersicon esculentum) extract on the genotoxicity of doxorubicin in the Drosophila wing spot test

The consumption of organic tomatoes (ORTs) reduces the risk of harmful effects to humans and the environment caused by exposure to toxic agrochemicals. In this study, we used the somatic mutation and recombination test (SMART) of wing spots in Drosophila melanogaster to evaluate the genotoxicity of ORT and the effect of cotreatment with ORT on the genotoxicity of Doxorubicin^® (DXR, a cancer chemotherapeutic agent) that is mediated by free radical formation. Standard (ST) cross larvae were treated chronically with solutions containing 25%, 50% or 100% of an aqueous extract of ORT, in the absence and presence of DXR (0.125 mg/mL), and the number of mutant spots on the wings of emergent flies was counted. ORT alone was not genotoxic but enhanced the toxicity of DXR when administered concomitantly with DXR. The ORT-enhanced frequency of spots induced by DXR may have resulted from the interaction of ORT with the enzymatic systems that catalyze the metabolic detoxification of this drug.

The genotoxicity of vitamin C in vitro

The genotoxic effects of Vitamin C (ascorbic acid) on human lymphocytes in vitro were estimated by analyzing and identifying various chromosome abnormalities, in relation to the concentration of Vitamin C. Testing concentrations of Vitamin C induced different aberrations including the impairment of spindle function. The spindle disturbances can result in mitotic arrest, multipolar spindles and multipolar segregation, errors in chromosome segregation, formation of chromosome bridges and chromosome laggards. The most frequent irregularities were found in anaphase and telophase. A certain number of lymphocytes were arrested at anaphase or telophase (in colchicine-untreated cultures of human lymphocytes). Testing concentrations of ascorbic acid did not induce a significant increase in the number of aneuploid mitoses and were not clastogenic except at the highest concentration (1,000 microg/ml) in colchicine-treated cultures, and in colchicine-untreated cultures of human lymphocytes the pulverization of chromosome was observed. Vitamin C changed the mitotic index value of lymphocytes notably at the higher concentrations (250, 500 and 1,000 microg/ml).

Modulation of doxorubicin-induced genotoxicity by Aegle marmelos in mouse bone marrow: a micronucleus study

The effect of various concentrations of Aegle marmelos (AME) on the doxorubicin (DOX)-induced genotoxic effects in mice bone marrow was studied. Treatment of mice with different concentrations of DOX resulted in a dose-dependent elevation in the frequency of micronucleated polychromatic (MPCE) as well as normochromatic (MNCE) erythrocytes in mouse bone marrow. The frequencies of MPCE and MNCE increased with scoring time, and the greatest elevation for MPCE was observed at 48 hours post-DOX treatment, whereas a maximum increase in MNCE was observed at 72 hours post-DOX treatment. This increase in MPCE and MNCE was accompanied by a decline in the polychromatic erythrocytes-normochromatic erythrocytes (PCE/NCE) ratio, which showed a DOX-dose-dependent decline. Treatment of mice with 200, 250, 300, 350, and 400 mg/kg body weight of AME, orally once daily for 5 consecutive days before DOX treatment, significantly reduced the frequency of DOX-induced micronuclei accompanied by a significant elevation in the PCE/NCE ratio at all scoring times. The greatest protection against DOX-induced genotoxicity was observed at 350 mg/kg AME. The protection against DOX-induced genotoxicity by AME may be due to inhibition of free radicals and increased antioxidant status.

Cisplatin-evoked DNA fragmentation in normal and cancer cells and its modulation by free radical scavengers and the tyrosine kinase inhibitor STI571

Cis-diamminedichloroplatinum(II) (cisplatin, cis-DDP) is well studied anticancer drug, whose activity can be attributed to its ability to form adducts with DNA, but this drug can also form DNA-damaging free radicals, however this mechanism of cisplatin action is far less explored. Using the comet assay we studied cisplatin-induced DNA damage in the presence of spin traps: DMPO and PBN, Vitamins A, C and E as well as the tyrosine kinases inhibitor STI571 in normal human lymphocytes and leukemic K562 cells. The latter cells express the BCR/ABL fusion protein, which can be a target of the tyrosine kinase inhibitor STI571. A 20 h incubation with cisplatin at 1-10 microM induced DNA cross-links and DNA fragmentation in normal and cancer cells. Cisplatin could induce intra- and interstrand DNA-DNA cross-links as well as DNA-protein cross-links. DNA damage in K562 cells was more pronounced than in normal lymphocytes. In the presence of spin traps and vitamins we noticed a decrease in the DNA fragmentation in both cell types. Co-treatment of the lymphocytes with cisplatin at 10 microM and STI571 at 0.25 microg/ml caused an increase of DNA fragmentation in comparison with DNA fragmentation induced by cisplatin alone. In the case of K562 cells, an increase of DNA fragmentation was observed after treatment with cisplatin at 1 microM. Our results indicate that the free radicals scavengers could decrease DNA fragmentation induced by cisplatin in the normal and cancer cells, but probably they have no effect on DNA cross-linking induced by the drug. The results obtained with the BCR/ABL inhibitor suggest that K562 cells could be more sensitive towards co-treatment of cisplatin and STI571. Our results suggest also that aside from the BCR/ABL other factors such as p53 level, signal transduction pathways and DNA repair processes can be responsible for the increased sensitivity of K562 cells to cisplatin compared with normal lymphocytes.

Ascorbic acid potentiates mitomycin C-induced micronuclei and sister chromatid exchanges in human peripheral blood lymphocytes in vitro

Vitamin C (l-ascorbic acid), an effective free radical scavenger present as ascorbate in most biological systems, is one of the most extensively studied antioxidant vitamins. Vitamin C acts as either a free radical scavenger or a pro-oxidant producing hydrogen peroxide and free radicals. The modulatory effect of L-ascorbic acid (AA) on Mitomycin C (MMC) induced chromosome damage has been evaluated in human peripheral blood lymphocytes in vitro. The effect of L-ascorbic acid, 200 microg/ml as 1- and 2-h pretreatment on the frequencies of the biomarkers micronuclei (MN), sister chromatid exchanges (SCEs), and chromosome aberrations (CA) induced by mitomycin C 0.1 and 0.2 microg/ml has been studied. AA pretreatment caused a statistically significant increase in MMC-induced MN and SCE frequencies for all treatment groups, but did not show an increase in induced chromosome aberrations compared to MMC treatment alone. Cell division delays caused by MMC was reversed in the presence of AA. Interindividual variability in MMC as well as AA plus MMC-induced MN, SCE, and CA frequencies were evident. Ascorbic acid potentiated MMC-induced chromosome damage in human lymphocytes in vitro. The potentiation observed has to be viewed in the light of metal ion catalysed autooxidation of AA in oxygenated media and the existence of an antioxidant system in vivo that inactivates oxyradicals before their interaction with DNA.

Doxorubicin and two of its analogues are preferential inducers of homologous recombination compared with mutational events in somatic cells of Drosophila melanogaster

The genotoxic effects of the anthracycline doxorubicin (DOX) and two of its analogues, epirubicin (EPI) and pirarubicin (THP) were studied using the wing Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. These compounds are classified as topoisomerase II (topo II) poisons, acting by stabilizing a topoisomerase II-cleaved DNA complex. Using the standard version of the SMART test it was possible to estimate the quantitative and qualitative genotoxic effects of these compounds, comparing the wing spot frequencies in marker- and balancer-heterozygous flies. The results obtained indicate that all three compounds induce a high frequency of spots related to homologous recombination (HR), which is the major event responsible for their genetic toxicity. Pirarubicin was the most genotoxic anthracycline, inducing approximately 21 times more genetic lesions than doxorubicin, probably due to the presence of a second sugar ring in the amino sugar moiety in its chemical structure. Although the only difference between epirubicin and doxorubicin is the steric position of the amino sugar 4'-OH in the molecule, epirubicin is approximately 1.6 times as genotoxic as doxorubicin.

The effects of oral glutamine on cisplatin-induced genotoxicity in Wistar rat bone marrow cells

Several studies have suggested that dietary supplementation with antioxidants can influence the response to chemotherapy as well as the development of adverse side effects that result from treatment with antineoplastic agents. The emphasis of the present study was to investigate whether the administration of a single dose of oral glutamine had any protective effect against cisplatin-induced clastogenicity. Cisplatin was administered to Wistar rats either alone or after treatment with glutamine. The rats were treated with glutamine (300 mg/kg b.w.) by gavage 24h before the administration of cisplatin (5mg/kg b.w., i.p.) and then sacrificed 24h after treatment with cisplatin. Glutamine significantly reduced (by about 48%) the clastogenicity of cisplatin in rat bone marrow cells. The antioxidant action of glutamine presumably modulates the clastogenic action of cisplatin.

Anticlastogenic effect of Vitamin C on cisplatin induced chromosome aberrations in human lymphocyte cultures

Vitamin C (ascorbic acid) is an antioxidant that can scavenge free radicals and protect cellular macromolecules, including DNA, from oxidative damage induced by different agents. The protective effect of Vitamin C on cisplatin induced chromosome aberrations has been determined in the human peripheral lymphocyte chromosome aberration test in vitro. The results of treatments with Vitamin C indicated that it statistically significantly decreases the number of chromosome aberrations and number of metaphases with aberrations induced with cisplatin, but it can not completely protect cells from damage. The test concentrations of Vitamin C (10 and 100 microg/ml) had a limited antimutagen effect on cisplatin (0.5 microg/ml), which can cause genetic damage through free radical mechanisms. The antimutagen effect included the anticlastogenic effect of Vitamin C and its ability to decrease the number of aneuploid mitoses. Vitamin C showed the most efficient anticlastogenic effect during simultaneous treatment with cisplatin. Also, Vitamin C reduced cell toxicity of cisplatin during simultaneous treatment.

Effect of vitamin C supplementation against cisplatin-induced toxicity and oxidative DNA damage in rats

Antitumor agents are used as a common therapy against some kinds of cancer. However, as with many agents that have mammalian cell toxicity as a target, physiological adverse effects can occur such as nephrotoxicity and genotoxicity that can be induced in non-tumor cells by generating activated oxygen species, which attack the DNA frequently resulting in oxidative DNA damage. To diminish the undesirable side-effects of therapy and to reduce the levels of oxidative DNA damage, it is recommended for patients to ingest food supplements and vitamins combinations containing substantial amounts of antioxidants. In the present study, we investigated the effects of cisplatin and vitamin C on the renal toxicity and on the oxidative DNA damage. Rats were co-treated with the chemotherapeutic agent cisplatin (5 mg kg(-1) body weight) and dietary doses of vitamin C (50 and 100 mg kg(-1) body weight). Results demonstrated that depending on the treatment protocol, we observed alterations in parameters such as body weight, urinary volume and urinary creatinine, indicating some kidney toxicity. We also observed changes in the urinary levels of 8-OHdG, suggesting possible oxidative DNA damage.

Influence of dietary antioxidants on the mutagenicity of 7,12-dimethylbenz[a]anthracene and bleomycin in female rats

Studies on agents that modulate carcinogen-induced genotoxic effects in experimental animals provide end points that can be used for assessing the antimutagenic or anticarcinogenic properties of putative chemopreventive compounds and for predicting their protective efficacy in humans. In this study, we investigated the ability of the dietary antioxidant Vitamins C, E, beta-carotene and the mineral selenium to inhibit the mutant frequency (MF) induced by treatment of rats with 7,12-dimethylbenz[a]anthracene (DMBA), a mammary carcinogen and bleomycin (BLM), an anti-tumor agent that can damage DNA by free radical mechanisms. Both chemicals have been previously shown to be mutagenic in the rat lymphocyte Hprt assay. Adult female Fischer 344 rats were given the antioxidants singly or in a combination 2 weeks prior to mutagen treatment. Antioxidant intake continued for an additional 4 weeks post-mutagen treatment. At sacrifice, spleens were aseptically removed for the isolation of lymphocytes to conduct the mutagenesis assay at the Hprt locus. The DMBA and BLM treatment induced a marked increase in MF, 52.8 x 10(-6) and 19.2 x 10(-6), respectively, over the controls. The MFs seen in the individual antioxidants alone (single or mixture) were relatively similar to the controls, with the exception of Vitamins C and E, that had 1.7- and 1.5-fold increase, respectively. The degree of inhibitory response was dependent on the type of mutagen and the particular antioxidant. BLM/antioxidant combination had inhibitions ranging from 44 to 80%, while DMBA/antioxidant system ranged from 60 to 93%, with Vitamins C and E achieving the highest inhibition in both systems. The mixture displayed low inhibitory responses, 44.6% for BLM/mix and 47% DMBA/mix. On the whole, the results indicate that the dietary constituents tested are antimutagenic; however, because of the gradations seen with the responses, the protective efficacy of these antioxidants may depend on the type of mutagen/carcinogen they encounter. Pending molecular analysis of mitochondrial DNA mutations will also indicate whether there is a shift in the mutational spectra produced by the carcinogens in the presence of antioxidants.

Protective effect of thiourea, a hydroxyl-radical scavenger, on curcumin-induced chromosomal aberrations in an in vitro mammalian cell system

Natural dietary antioxidants are extensively studied for their ability to protect cells from damage to DNA, protein, and lipids induced by antitumor agents or radiation that leads to the generation of free radical in normal cells in vivo and in vitro. Curcumin is a natural antioxidant known to possess therapeutic properties and has been reported to scavenge free radicals and to inhibit clastogenesis in mammalian cells. However, curcumin has been reported to induce a significant increase in the frequency of chromosomal aberrations in Chinese hamster ovary (CHO) cells. To investigate whether the clastogenic activity of curcumin in CHO cells in culture can be ascribed to a pro-oxidant behavior, mediated by free radical generation, experiments were carried out with the combination of curcumin (15 microg/ml) and thiourea (10, 20, or 40 microg/ml), a potent hydroxyl radical scavenger. The results showed that the clastogenic action of curcumin was statistically decreased in a dose-dependent manner in the presence of thiourea. These data have shown that curcumin-induced chromosomal damage in CHO cells can be mediated by hydroxyl radical generation in the present experimental conditions. Teratogenesis Carcinog. Mutagen. 21:175-180, 2001.

Effects of selenium pretreatment on cisplatin-induced chromosome aberrations in wistar rats

Selenium is an essential trace element and a potent anticancer agent. Extensive laboratory studies demonstrate that selenium is an effective chemopreventive agent in various sites in animals. The administration of selenium as a chemopreventive agent raises the question whether the antioxidant selenium, alone or in combination with other dietary antioxidants, could protect non-tumor cells from the clastogenic effect of cisplatin. Therefore, the present study was undertaken to investigate the modulatory effects of selenium, combined or not with vitamin C, on cisplatin-induced chromosomal aberrations in Wistar rat bone marrow cells. The animals were sacrificed 18, 24, or 72 h after cisplatin injection. The results obtained in Wistar rat bone marrow cells showed a slight nonsignificant reduction in the total number of chromosomal aberrations induced by cisplatin (5 mg/kg b.w.) observed in the animals that received a pretreatment with a single dose of selenium (2 mg/kg b.w.). The administration of two doses of selenium (1 mg/kg b.w.) also did not inhibit the chromosomal damage induced by cisplatin. In the present study, no protective response was obtained with either a single or double dose of selenium in rats treated with cisplatin. Furthermore, the combination between selenium+vitamin C was no more effective than vitamin C alone in the protection against damage caused by this antitumor drug. Further investigations, with other forms of selenium, are necessary to elucidate a possible protective role of selenium in clastogenicity induced by free radicals generated by antitumor drugs.

Structure-activity analysis of the potentiation by aminothiols of the chromosome-damaging effect of bleomycin in G0 human lymphocytes

The radioprotective aminothiols 2-[(aminopropyl)amino] ethanethiol (WR-1065) and cysteamine (CSM) potentiate the induction of chromosomal damage by the radiomimetic compound bleomycin (BLM) in G0 human lymphocytes. To investigate the mechanism of potentiation, we measured the clastogenic activity of BLM in the cytokinesis-block micronucleus assay in the presence and absence of amines, thiols, and aminothiols. The hydroxy analog of WR-1065, 2-(3-aminopropylamino) ethanol (WR-OH), potentiates BLM only slightly, indicating the critical nature of the thiol group. As thiols, WR-1065 and CSM may donate electrons for the activation of Fe(+2)-BLM or for the regeneration of Fe(+2)-BLM from inactive Fe(+3)-BLM. The amines putrescine, spermidine, and spermine all potentiate BLM, but they are weaker potentiators than the aminothiols, and they are effective only at high concentrations. Their activity, like that of WR-OH, is probably a consequence of conformational alteration of DNA. Dithioerythritol (DTE) and 2-mercaptoethanol (2-ME), thiols lacking an amino group, are less effective potentiators of BLM than are the aminothiols. The thiol group of WR-1065 and CSM is therefore essential, but insufficient, for explaining the strong enhancement of BLM activity. The cationic nature of CSM and WR-1065, conferred by the amino groups, evidently concentrates the active thiol function at the site of BLM action on DNA. As expected on this basis, the diamine WR-1065 is a more effective potentiator of BLM than is the monoamine CSM, whereas cysteine and N-acetylcysteine (NAC), which lack a net positive charge, potentiate BLM only weakly. These studies suggest that potentiation of the clastogenic action of BLM by aminothiols can be explained by the combination of a thiol-mediated redox mechanism and an amine-mediated targeting of the thiol function to DNA.

Effects of the antioxidants curcumin and vitamin C on cisplatin-induced clastogenesis in Wistar rat bone marrow cells

The use of dietary antioxidants to prevent antitumor agent-induced chromosomal damage in nontumor cells is currently eliciting considerable interest. Curcumin (CMN) is a dietary antioxidant that has been reported to protect against clastogenesis in in vivo and in vitro assays. This study was undertaken to investigate the modulatory effects of CMN on cisplatin-induced chromosomal aberrations in Wistar rat bone marrow cells and whether there is any potentiation of these effects with the combination between CMN and vitamin C (VC), which has been reported to reduce the clastogenic effect of many antitumor agents in in vivo assays. Animals treated with CMN plus a single dose of cisplatin, at 18, 24 or 72 h following treatment, presented a statistically significant reduction in the total amount of chromosomal damage and in the number of abnormal metaphases. The results also indicate that the combination between antioxidants would not be effective in protecting against cisplatin-induced chromosomal damage in animals sacrificed 24 h after cisplatin treatment. Under the present experimental conditions, CMN could prevent cisplatin-induced clastogenesis by acting as a free radical scavenger.

Inhibitory effects of chlorophyllin on 7,12-dimethylbenz[a]anthracene-induced bacterial mutagenesis and mouse skin carcinogenesis

Chlorophyllin (CHL), a water-soluble derivative of chlorophyll, has been used for the treatment of several abnormal human conditions without apparent toxicity. Recent studies have revealed that CHL has the excellent chemopreventive potential. In the present investigation, we have found the inhibitory activities of CHL against 7,12-dimethylbenz[a]anthracene (DMBA)-induced mutagenesis in Salmonella typhimurium TA100 and also on DMBA-initiated and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-promoted mouse skin tumor formation. The incidence and the multiplicity of skin tumors were not significantly decreased in mice by a single topical application of CHL prior to the DMBA treatment, but there was a marked suppression of papillomagenesis in mice treated with CHL during the promotional stage. Furthermore, the formation of DMBA-induced papillomagenesis was reduced in all mice that had received CHL for 6 weeks following treatment with TPA for 6, 18 and 24 weeks. These results indicate that CHL can inhibit both tumor promotion and the progression of papillomagenesis in the two-stage mouse skin carcinogenesis induced by DMBA and TPA.

Anticlastogenic effect of vitamin C on cisplatin in vivo

The ability of vitamin C (VC) to protect against the clastogenic action of the chemotherapeutic agent cisplatin (DDP, cis-diamminedichloroplatinun II) in rat bone marrow cells was evaluated. DDP was administered to Wistar rats either alone or after treatment with VC. The rats were treated with VC (50, 100 or 200 mg/kg body weight) by gavage 10 min before the administration of DDP (5 mg/kg body weight, ip) and then sacrificed 24 h after treatment. VC significantly reduced (by about 70%) the clastogenicity of DDP in rat bone marrow cells. The antioxidant action of VC presumably modulates the clastogenic action of DDP.