Assessment of genome damage in a population of Croatian workers employed in pesticide production by chromosomal aberration analysis,micronucleus assay and Comet assay

The widespread use of pesticides suggests that the evaluation of their genotoxicity should be extended using the different assays available. In the present study we used two standard cytogenetic methods (chromosomal aberration analysis and micronucleus assay) and the Comet assay as a relatively new and powerful technique. The study included 10 workers occupationally exposed to a complex mixture of pesticides (atrazine, alachlor, cyanazine, 2,4-dichlorophenoxyacetic acid, malathion) during their production and 20 control subjects with no history of exposure to any physical or chemical agents. For the chromosomal aberration analysis, whole blood was cultivated for 48 h, whereas for the micronucleus assay, whole blood was cultivated for 72 h. For the comet assay whole blood was embedded in agarose on a microscope slide, lysed with detergent, denaturated and subjected to alkaline electrophoresis. Damage to DNA was evaluated by measuring tail length and calculating the tail moment. A significantly increased number of chromatid and chromosome breaks, as well as the presence of dicentric chromosomes and chromatid exchanges in exposed subjects compared with control subjects (P < 0.05), was found. There was also a statistically significant difference in frequency and distribution of micronuclei between the two groups examined. In the exposed subjects the Comet assay showed a statistically significant (P < 0.001) increase in DNA migration. Results suggest that long-term occupational exposure to pesticides could cause genome damage in somatic cells and therefore may represent a potential hazard to human health.     

Genotoxic effects of chlorophenoxy herbicide diclofop-methyl in mice in vivo and in human lymphocytes in vitro

Diclofop-methyl (DM) is a chlorophenoxy derivative used in large quantities for the control of annual grasses in grain and vegetable crops. In this study, the genotoxic effects of DM were investigated by measuring chromosomal aberrations (CAs) in mouse bone-marrow cells and CA and the comet assay in human peripheral lymphocytes. Mice were treated with 15.63, 31.25, 62.5, and 125?mg/kg body weight of DM intraperitoneally for 24 hours, and 15.63-, 31.25-, 62.5-, 125-, and 250-µg/mL concentrations were applied to human lymphocytes for both 24 and 48 hours. In in vivo treatments, DM significantly, but not dose dependently, increased the total chromosome aberrations, compared to both negative and solvent controls. Cell proliferation was significantly, but not dose dependently, affected by all doses. In in vitro treatments, DM (except 15.63 µg/mL) significantly and dose dependently increased the frequency of chromosome aberrations. Also, 250 µg/mL of 48-hour treatment was found to be toxic. Cell proliferation was significantly and dose dependently affected by DM applications, when compared to negative control. In in vitro treatments, DM significantly decreased the mitotic index only at the highest concentration for 24 hours, and 62.5- and 125-µg/mL concentrations for 48 hours. In the comet assay, a significant and dose-dependent increase in comet-tail intensity was observed at 62.5-, 125-, and 250-µg/mL concentrations. The mean comet-tail length was significantly increased in all concentrations. Our results demonstrate that DM is genotoxic in mammalian cells in vivo and in vitro.     

Genotoxic effects of chlorpyrifos,cypermethrin, endosulfan and 2,4‐D on human peripheral lymphocytes cultured from smokers and nonsmokers

Pesticides often cause environmental pollution and adverse effects on human health. We have chosen four structurally different pesticides (endosulfan, an organochlorine pesticide; chlorpyrifos, an organophosphate insecticide; cypermethrin, type II pyrethroid insecticide, and 2,4‐dichlorophenoxyacetic acid, a chlorinated aromatic hydrocarbon acid pesticide) to examine and compare their effects on DNA damage in acutely cultured human lymphocytes by the comet assay. In addition, possible differences in response between smoking and nonsmoking subjects were also investigated. Venous blood samples were obtained from healthy male nonsmoker (n = 7) and smoker (n = 8) donors. Primary cultures of lymphocytes were prepared and test groups were treated with three different concentrations (1, 5, and 10 μM) of endosulfan, chlorpyrifos, cypermehrin, and 2,4‐D. DNA damage was assessed by alkaline comet assay. We determined an increase in the ratio of DNA migration in human lymphocyte cell cultures as a result of treatment with cypermethrin, 2,4‐D and chlorpyrifos at high concentration. Endosulfan had no significant genotoxic effect even at 10 μM concentration. We suggest that chlorpyrifos and cypermethrin are more potentially genotoxic than endosulfan and 2,4‐D. Our findings also indicate that the only significant DNA damage between smokers and nonsmokers was observed in the 2,4‐D‐treated group. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

Assessment of genotoxic effects of (4-methoxyphenyl)(3,4,5-trimethoxyphenyl)methanone in human lymphocytes

(4-Methoxyphenyl)(3,4,5-trimethoxyphenyl)methanone (PHT) belongs to the phenstatin family. This compound has been studied due to its potent cytotoxicity and ability to inhibit tubulin assembly. The present study aimed to evaluate the mutagenic potential of PHT in human lymphocytes. PHT displayed cytotoxicity in human lymphocytes with an IC₅₀ value of 5.68 μM, and therefore, concentrations of 0.25, 0.5, 1.0, 2.0, and 4.0 μM were used for all protocols. The alkaline comet assay and chromosome aberration (CA) analysis were performed in different phases of the cell cycle (G₁, G₁/S, transition, and G₂), to evaluate the DNA-damaging and clastogenic effects of PHT, respectively. CA analysis was carried out in the presence or absence of colchicine to evaluate the action of PHT in the mitotic phase. PHT was cytotoxic and significantly reduced the mitotic index with drug exposure in all phases of cell cycle. Interestingly, it induced an increase in mitotic index in experimental protocols without colchicine, corroborating its action as an antitubulin agent. It also induced DNA damage and was clastogenic with drug exposure in all phases of the cell cycle, in the presence or absence of colchicine. In conclusion, PHT induces DNA damage and exerts clastogenic effects in human lymphocytes.     

Evaluation of the genotoxicity and cytotoxicity of fexofenadine in cultured human peripheral blood lymphocytes

Fexofenadine (FXF) is a new non-sedating antihistamine used in the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria. Studies on FXF genotoxicity and cytotoxicity in cultured human peripheral blood lymphocytes have not been reported so far. Therefore, the present study is the first report investigating the genotoxic and cytotoxic effects of FXF in cultured human peripheral blood lymphocytes in vitro. Cultures were treated with FXF at three concentrations (50, 100 and 150 μg/ml) for 24 and 48 h. Endpoints analyzed included: mitotic index (MI), nuclear division index (NDI), chromosomal aberrations (CA) and micronucleus (MN) assay. Mitomycin C (MMC) was used as a positive control. The results of CA and MN assays showed that FXF was not genotoxic at all the concentrations tested, meanwhile MI and NDI results showed dose-dependent decrease and significant differences were found for at least one concentration. In conclusion, the results of this study suggest that FXF has a cytotoxic effect but not genotoxic effect on human peripheral blood lymphocyte cultures. Further cytogenetic studies, especially about the cell cycle kinetics of FXF are required to elucidate the decreases in dividing cells, and biomonitoring studies should also be conducted with patients receiving therapy with this drug.     

Nanoscale zerovalent iron particles induce differential cytotoxicity,genotoxicity, oxidative stress and hemolytic responses in human lymphocytes and erythrocytes in vitro

The growing usage of nanoscale zerovalent iron particles (nZVI) in the remediation of soil, ground/surface water has elicited large‐scale environmental release triggering human exposure. The size of nanomaterials is a key regulator of toxicity. However, the effect of a variable size of nZVI on genotoxicity is unexplored in human cells. To the best of our knowledge, in this study, the cytotoxic, genotoxic and hemolytic potential of nZVI‐1 (15 nm) and nZVI‐2 (50 nm) at concentrations of 5, 10 and 20 μg/mL was evaluated for the first time in human lymphocytes and erythrocytes treated for 3 hours. In erythrocytes, spherocytosis and echinocytosis occurred upon exposure to nZVI‐1 and nZVI‐2, respectively, leading to hemolysis. Lymphocytes treated with 20 μg/mL nZVI‐2 and 10 μg/mL nZVI‐1, incurred maximum DNA damage, although nZVI‐2 induced higher cyto‐genotoxicity than nZVI‐1. This can be attributed to higher Fe ion dissolution and time/concentration‐dependent colloidal destabilization (lower zeta potential) of nZVI‐2. Although nZVI‐1 showed higher uptake, its lower genotoxicity can be due to lesser Fe content, Fe ion dissolution and superior colloidal stability (higher zeta potential) compared with nZVI‐2. Substantial accumulation of Ca²⁺, superoxide anions, hydroxyl radicals and H₂O₂ leading to mitochondrial impairment and altered antioxidant enzyme activity was noted at the same concentrations. Pre‐treatment with N‐acetyl‐cysteine modulated these parameters indicating the indirect action of reactive oxygen species in nZVI‐induced DNA damage. The morphology of diffused nuclei implied the possible onset of apoptotic cell death. These results validate the synergistic role of size, ion dissolution, colloidal stability and reactive oxygen species on cyto‐genotoxicity of nZVI and unlock further prospects in its environmental nano‐safety evaluation.     

顺铂对人体淋巴细胞的细胞毒性和遗传毒性特征

为了解顺铂对人体外周血淋巴细胞的细胞毒性和遗传毒性特征,在人体外周血淋巴细胞培养物中分别加入０．１ 和０．５ ｍ ｇ·Ｌ－ １顺铂,７２ ｈ 后观察淋巴细胞转化率,增殖指数,姐妹染色单体交换（ＳＣＥ）频率及染色体畸变（ＣＡ）率等． 结果表明,两顺铂组的淋巴细胞转化率均显著降低,ＳＣＥ频率和ＣＡ 率显著增高． 顺铂对人体淋巴细胞的细胞毒性主要特征是抑制其转化,较高剂量时使部分非转化小淋巴细胞发生聚集融合;遗传毒性特征表现为诱发高频ＳＣＥ和以裂隙及断裂为主的多种类型的染色体结构畸变,较高剂量时引起复杂交联．     

Comparing the genotoxicity of a potentially carcinogenic and a noncarcinogenic PAH,singly, and in binary combination,on peripheral blood cells of the European sea bass

Research on the toxicological mechanisms of polycyclic aromatic hydrocarbons (PAHs) deemed carcinogenic and noncarcinogenic has mostly been developed for individual compounds even though, in the environment, PAHs invariably occur in mixtures. The present work aimed at understanding the interaction effects of two model PAHs, the potentially carcinogenic benzo[b]fluoranthene (B[b]F) and the noncarcinogenic phenanthrene (Phe) to a marine fish (the sea bass Dicentrarchus labrax). The study endeavoured an ecologically‐relevant scenario with respect to concentrations and contaminant matrix, sediments, which are the main reservoirs of these substances in the environment, due to their hydrophobic nature. For the purpose, 28‐day laboratorial bioassays with spiked sediments (with individual and combined PAHs at equitoxic concentrations) were conducted. Genotoxicity was determined in peripheral blood through the “Comet” assay and by scoring erythrocytic nuclear abnormalities (ENA). The results showed that exposure to either PAHs induced similar levels of DNA strand breaks, although without a clear dose‐ or time‐response, likely due to the low concentrations of exposure and potential shits in PAH bioavailability during the assays. However, clastogenic/aneugenic lesions were only observed in fish exposed to B[b]F‐spiked sediments. Conversely, the combination assays revealed a supra‐additive effect especially at chromosome level, linked to concentrations of PAHs in water. A decrease in DNA‐strand breakage was observed over time during all assays, revealing some ability of fish to cope with this DNA lesion. Overall, the findings show that low‐moderate concentrations of sediment‐bound mixed PAHs may significantly increase the hazard of mutagenesis even when the individual concentrations indicate low risk, especially considering that chromosome‐level damage is unlikely to be repaired, leading to the fixation of DNA lesions upon prolonged exposures. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1307–1318, 2016.     

In vivo genotoxicity and cytotoxicity assessment of a novel quinoxalinone with trichomonacide activity

The compound VAM2‐6 (1‐methyl‐7‐nitro‐4‐(5‐(piperidin‐1‐yl)pentyl)‐3,4‐dihydroquinoxalin‐2(1H)‐one) has previously been shown to have an in vitro efficacy of 100% at a concentration of 100 µg ml^–1 against Trichomonas vaginalis, a protozoon parasite that causes the sexually transmitted disease trichomoniasis. Because VAM2‐6 is a quinoxaline derivative and given the lack of studies on the genotoxic activity of this compound, the present study was undertaken to evaluate its ability to induce DNA damage in the peripheral blood of mice using single‐cell gel electrophoresis (SCGE or comet assay) and the micronucleus (MN) assay. Cell viability was assessed using a fluorochrome‐mediated viability test. The compound was tested on CD1 mice at 60, 40 and 10 mg kg^–1 body weight administrated intraperitoneal (i.p.) in a single dose. Peripheral blood samples were collected 24 and 48 h after treatment. N‐Ethyl‐N‐nitrosourea (ENU) was used as a positive control for the comet and micronucleus assays. The results showed that i.p. VAM2‐6 induced single‐strand DNA breaks and increased the average number of micronuclei in the treated mice in a dose‐dependent manner at 60, 40 and 10 mg kg^–1. Cell viability decreased at 24 h but recovered at 48 h for all three evaluated doses. Therefore, the chemical structure of VAM2‐6 should be modified to reduce its genotoxic potential. Copyright © 2012 John Wiley & Sons, Ltd.     

A research on the genotoxicity of stevia in human lymphocytes

Stevia extracts are obtained from Stevia rebaudiana commonly used as natural sweeteners. It is ～250–300 times sweeter than sucrose. Common use of stevia prompted us to investigate its genotoxicity in human peripheral blood lymphocytes. Stevia (active ingredient steviol glycoside) was dissolved in pure water. Dose selection was done using ADI (acceptable daily intake) value. Negative control (pure water), 1, 2, 4, 8 and 16?μg/ml concentrations which were equivalent to ADI/4, ADI/2, ADI, ADI?×?2 and ADI?×?4 of Stevia were added to whole-blood culture. Two repetitive experiments were conducted. Our results showed that there was no significant difference in the induction of chromosomal aberrations and micronuclei between the groups treated with the concentrations of Stevia and the negative control at 24 and 48?h treatment periods. The data showed that stevia (active ingredient steviol glycosides) has no genotoxic activity in both test systems. Our results clearly supports previous findings.     

Evaluation of salidroside in vitro and in vivo genotoxicity

It is reported that salidroside, the main component of a traditional Chinese medicine, Rhodiola rosea, has the efficacy of protecting Coxsackie virus impairment. As part of a safety evaluation on salidroside for use in the treatment of viral myocarditis, the present study evaluated potential genotoxicity of salidroside by using the standard battery of tests (i.e., bacterial reverse mutation assay, chromosomal aberrations assay, and mouse micronucleus assay) recommended by the State Food and Drug Administration of China. The results showed that salidroside was not genotoxic under the conditions of the reverse mutation assay, chromosomal aberrations assay, and mouse micronucleus assay conditions. The anticipated clinical dose seems to be smaller than the doses administered in the genotoxicity assays. With confirmation from further toxicity studies, salidroside would hopefully prove to be a safe anti-Coxsackie virus agent.     

Ziprasidone induces cytotoxicity and genotoxicity in human peripheral lymphocytes

It has been stated that some antipsychotic drugs might cause genotoxic and carcinogenic effects. Ziprasidone (ZIP) is commonly used an antipsychotic drug. However, its genotoxicity and carcinogenicity data are very limited. The cytotoxicity and genotoxicity of ZIP on human peripheral blood lymphocytes were examined in vitro by sister chromatid exchange (SCE), chromosome aberration (CA) and micronucleus (MN) tests in this study. Lymphocyte cultures were treated with 50, 75 and 100?μg/ml of ZIP in the presence and absence of a metabolic activator (S9 mix). Dimethylsulfoxide was used as a solvent control. While the cells were treated with ZIP for 24?h and 48?h in cultures without S9 mix, the cultures with S9 mix were exposed to ZIP for 3?h. ZIP and its metabolites can exert cytotoxic activities due to significant decreases in mitotic index, proliferation index and nuclear division index in the presence and absence of S9 mix. Statistically significant increases in CAs, aberrant cells and MN values in the presence and absence of S9 mix were found in cultures treated with ZIP. While ZIP significantly increased the SCE values in the absence of S9 mix at all concentrations, increased SCE values in cultures with S9 mix were not found to significantly at all concentrations tested. Our results indicated that both ZIP and its metabolites have cytotoxic, cytostatic and genotoxic potential on lymphocyte cultures under the experimental conditions. Further studies are necessary to make a possible risk assessment in patients receiving therapy with this drug.     

Evaluation of genotoxicity induced by exposure to antineoplastic drugs in lymphocytes of oncology nurses and pharmacists

The hazards of handling antineoplastic drugs have been raised and discussed in several studies. Introduction of new antineoplastics together with abuse of safety standards have contributed to the exposure risk for personnel who handle these substances. Interactions of antineoplastic drugs with biological structures vary according to the drug(s) and the individual's genetic susceptibility. This study was carried out to evaluate the genome damage induced by exposure to antineoplastic drugs in nurses (n = 20) and pharmacists (n = 18) working in the Oncology Department of Tanta Cancer Center. Thirty subjects matched in age, gender and smoking habit were selected as controls. Both chromosomal aberration analysis and micronucleus assay were used to evaluate genome damage in peripheral blood lymphocytes of the study subjects. The numbers of aberrant lymphocytes, as well as chromosomal aberration and micronuclei frequencies, were significantly increased in exposed personnel in comparison to matched controls. Compared with pharmacists, nurses showed notably higher level of chromosome damage. On the other hand, no significant difference in micronuclei frequency was observed between nurses and pharmacists. Correlation analyses pointed to the influence of age and duration of occupational exposure on the level of chromosome damage among exposed subjects. The results of this study confirmed that handling antineoplastic drugs without appropriate precautions imposed a genotoxic risk for exposed healthcare workers. These results address the need for regular biomonitoring of exposed personnel. In addition, they call attention to the need for proper implementation of intervention measures aiming to eliminate or significantly reduce worker exposure and prevent untoward biological effects. Copyright © 2011 John Wiley & Sons, Ltd.     

Assessment of genotoxicity of benzidine and its structural analogues to human lymphocytes using comet assay.

Benzidine (BZ) and its six structural analogues (2-aminobiphenyl [2-ABP], 4-aminobiphenyl [4-ABP], 3,3'-diaminobenzidine [DABZ], 3,3'-dichlorobenzidine [DCBZ] 3,3'-dimethoxybenzidine [DEBZ], and 3,3'-dimthylbenzidine [DMBZ]) were examined for DNA damage in human lymphocytes using the alkaline comet assay. All the tested compounds showed a distinct disparity in their respective DNA-damaging capacities with an order of DABZ > BZ > DCBZ > 2-ABP > DEBZ > 4-ABP > DMBZ when lymphocytes were exposed to these chemicals for 2 h. Results show that the DNA-damaging effects of these compounds had no bearing on some physicochemical parameters including oxidation potentials, the energy differences between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, ionization potentials, dipole moment, and relative partition coefficient. On the other hand, the free radical scavengers, including catalase, SOD, BHT, EDTA, and histidine exerted varying degrees of inhibitory effects on the DNA damage caused by benzidine. This suggests that genotoxicity in lymphocytes caused by benzidine proceeded via a reactive oxygen species (ROS)-mediated mechanism.     

Genotoxic evaluation of terbinafine in human lymphocytes in vitro

Terbinafine is an antimycotic drug usually used against several superficial fungal infections and with a potential application in the treatment of human cancers. Since to date there are few data on the genotoxic effects of terbinafine in mammalian cells, current study evaluated the potential genotoxic of such antifungal agent in cultured human peripheral blood lymphocytes. Terbinafine was used at the peak plasma concentration (1.0?μg/ml) and in four additional concentrations higher than the human plasmatic peak (5.0?μg/ml, 25.0?μg/ml, 50.0?μg/ml and 100.0?μg/ml). Chromosomal aberrations (CA), sister chromatid exchanges (SCE), micronuclei (MN), nucleoplasmic bridges (NP) and nuclear buds (NB) were scored as genetic endpoints. In all analysis no significant differences (α?=?0.05, Kruskal-Wallis test) were observed. Complementary criterion adopted to obtain the final response in cytogenetic agreed with statistical results. Therefore, results of this study showed that terbinafine neither induced CA, SCE, MN, NP and NB nor affected significantly mitotic, replication and cytokinesis-block proliferation indices in any of the tested concentrations. It may be assumed that terbinafine was not genotoxic or cytotoxic to cultured human peripheral blood lymphocytes in our experimental conditions.     

鼠尾草酸的遗传毒性研究

目的 研究鼠尾草酸(carnosic acid,CA)的遗传毒性。方法 选用鼠伤寒沙门杆菌回复突变(Ames 试验)、体内哺乳动物红细胞微核、精子畸形以及单细胞凝胶电泳(彗星试验)四项致突变生物学试验进行筛选评价。结果 在6.25～50μg/mL 的剂量水平,CA 对鼠伤寒沙门菌株TA97、TA98、TA100、TA102 和TA1535 均无诱变性;此外,在受试剂量下小鼠骨髓嗜多染红细胞微核、小鼠精子畸形以及体内彗星试验的结果均为阴性(与溶剂对照比较,P> 0.05)。结论 在本实验条件下,CA 未见明显遗传毒性。     

Evaluation of genotoxicity of Yanhuanglian dehydrocavidine (YHL-DC) in vitro and in vivo

It is reported that dehydrocavidine (DC), the main component of a traditional Chinese medicine, Yanhuanglian (YHL), can protect hepatic tissue against HBV and HAV impairment. As part of a safety evaluation on YHL-DC for use in the treatment of HBV, the present study evaluated the potential genotoxicity of YHL-DC by using the standard battery of tests (i.e., bacterial reverse mutation, chromosomal aberrations, and mouse micronucleus assays) recommended by the State Food and Drug Administration of China. The results showed that YHL-DC was not genotoxic under the conditions of the reverse mutation, chromosomal aberrations, and mouse micronucleus assay conditions. The anticipated clinical dose should be smaller than the doses used in the genotoxicity assays. With confirmation from further toxicity studies, YHL-DC would hopefully prove to be a useful anti-HBV agent.     

In vitro assessment of cytotoxic,genotoxic and mutagenic effects of antimalarial drugs artemisinin and artemether in human lymphocytes

Artemisinin is a substance extracted from the Chinese plant Artemisia annua L. widely used in natural medicine for the treatment of various diseases. Artemether is a substance synthesized from artemisinin, and both drugs are commonly administered in the treatment of malaria. Although considered effective antimalarial drugs, very little is known about the genotoxic, cytotoxic and mutagenic effects of these drugs. Therefore, in the present study, we evaluated the genotoxic, mutagenic and cytotoxic effects of artemisinin (12.5, 25 and 50?µg/mL) and artemether (7.46; 14.92 and 29.84?µg/mL) in cultured human lymphocytes using the comet assay, the micronucleus test and the cytotoxicity assay for detection of necrosis and apoptosis by acridine orange/ethidium bromide staining. Our results showed a significant increase (p?<?0.05) in the rate of DNA damage measured by comet assay and in the micronucleus frequency after treatment with both drugs. It was also observed that only artemisinin induced a statistically significant increase (p?<?0.05) in the number of lymphocytes with death by necrosis 48?h after treatment. The results demonstrated that these two drugs induce mutagenic, genotoxic and cytotoxic effects in cultured human lymphocytes. Our data indicate the need for caution in the use of such drugs, since genotoxic/mutagenic effects may increase the risk of carcinogenesis.     

Uranyl Nitrilotriacetate, a Stabilized Salt of Uranium, is Genotoxic in Nontransformed Human Colon Cells and in the Human Colon Adenoma Cell Line LT97

Previous uranium mining in the "Wismut" region in Germany enhancedenvironmental distribution of heavy metals and radionuclides.Carryover effects may now lead to contamination of locally producedfoods. Compounds of "Wismut" origin are probably genotoxic viatheir irradiating components (radon) or by interacting directlywith cellular macromolecules. To assess possible hazards, weinvestigated the genotoxic effects of uranyl nitrilotriacetate(U-NTA) in human colon tumor cells (HT29 clone 19A), adenomacells (LT97), and nontransformed primary colon cells. Theseare target cells of oral exposure to environmentally contaminatedfoods and represent different cellular stages during colorectalcarcinogenesis. Colon cells were incubated with U-NTA. Cellsurvival, cytotoxicity, cellular glutathione (GSH) levels, genotoxicity,and DNA repair capacity (comet assay), as well as gene- andchromosome-specific damage combination of comet assay and fluorescencein situ hybridization [FISH], 24-color FISH) were determined.U-NTA inhibited growth of HT29 clone 19A cells (75–2000µM,72 h) and increased GSH (125–2000µM, 24 h). U-NTAwas genotoxic (1000µM, 30 min) but did not inhibit therepair of DNA damage caused by hydrogen peroxide (H₂O₂), 4-hydroxynonenal,and 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]-pyridine.U-NTA was also genotoxic in LT97 cells and primary colon cells,where it additionally increased migration of TP53 into the comettail. In LT97 cells, 0.5–2mM U-NTA increased chromosomalaberrations in chromosomes 5, 12, and 17, which harbor the tumor-relatedgenes APC, KRAS, and TP53. It may be concluded that uraniumcompounds could increase alimentary genotoxic exposure in humansif they reach the food chain in sufficient amounts.     

Modulation of ethoxyquin genotoxicity by free radical scavengers and DNA damage repair in human lymphocytes

N-tert-butyl-α-phenylnitrone (PBN) and its new derivative N-(Pyridine-4-ylmethylidene)-2-carboxy-tert-butylamine N-oxide (PBNC) were synthesized and used to modulate ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline, EQ) genotoxicity. Ethoxyquin, an antioxidant used mainly as a preservative in animal feeds, was shown to cause DNA breaks in human lymphocytes. The aim of the study was to evaluate the involvement of free radicals in the genotoxicity of EQ and its modulation by cellular repair systems. Human lymphocytes treated with EQ (10–50 μM) and nitrone free radical scavengers (100 μM) were tested with the comet assay. It was shown that both PBN and PBNC reduced the level of EQ-induced DNA damage, but PBN was slightly more effective. The modulation of the level of DNA damage was also observed as a result of DNA repair by cellular repair systems. Moreover, induction of oxidized bases by ethoxyquin was showed; lymphocytes exposed to ethoxyquin and treated with endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (FpG), enzymes recognizing oxidized bases, displayed greater extent of DNA damage than those not treated with the enzymes.