Cellular interactions and biological responses to titanium dioxide nanoparticles in HepG2 and BEAS‐2B cells: Role of cell culture media

We showed previously that exposure of human lung cells (BEAS‐2B) to TiO₂ nanoparticles (nano‐TiO₂) produced micronuclei (MN) only when the final concentration of protein in the cell‐culture medium was at least 1%. Nanoparticles localize in the liver; thus, we exposed human liver cells (HepG2) to nano‐TiO₂ and found the same requirement for MN induction. Nano‐TiO₂ also formed small agglomerates in medium containing as little as 1% protein and caused cellular interaction as measured by side scatter by flow cytometry and DNA damage (comet assay) in HepG2 cells. Nano‐TiO₂ also increased the activity of the inflammatory factor NFkB but not of AP1 in a reporter‐gene HepG2 cell line. Suspension of nano‐TiO₂ in medium containing 0.1% protein was sufficient for induction of MN by the nanoparticles in either BEAS‐2B or HepG2 cells as long the final concentration of protein in the cell‐culture medium was at least 1%. Environ. Mol. Mutagen. 55:336–342, 2014. © 2014 Wiley Periodicals, Inc.     

Synergistic genotoxicity caused by low concentration of titanium dioxide nanoparticles and p,p′‐DDT in human hepatocytes

The use of titanium dioxide nanoparticles (nano‐TiO₂) for the degradation of dichlorodiphenyltrichloroethane (p,p′‐DDT) increases the risk of exposure to trace nano‐TiO₂ and p,p′‐DDT mixtures. The interaction of p,p′‐DDT and nano‐TiO₂ at low concentrations may alter toxic response relative to nano‐TiO₂ or p,p′‐DDT alone. In this work, the combined genotoxicity of trace nano‐TiO₂ and p,p′‐DDT on human embryo L‐02 hepatocytes without photoactivation was studied. Nano‐TiO₂ (0.1 g/L) was mixed with 0.01–1 mmol/L p,p′‐DDT to determine adsorption isotherms. L‐02 cells were exposed to different levels of p,p′‐DDT (0, 0.001, 0.01, and 0.1 μmol/L) and nano‐TiO₂ (0, 0.01, 0.1, and 1 μg/mL) respectively. The adsorption of p,p′‐DDT by nano‐TiO₂ was approximately 0.3 mmol/g. Cell viability, apoptosis, and DNA double strand breaks were similar among all test groups. Nano‐TiO₂ alone (0.01–1 μg/mL) increased the levels of oxidative stress and oxidative DNA adducts (8‐OHdG), but it did not induce DNA breaks or chromosome damage. Addition of trace nano‐TiO₂ with trace p,p′‐DDT synergistically enhanced genotoxicity via increasing oxidative stress, oxidative DNA adducts, DNA breaks, and chromosome damage in L‐02 cells. Low concentrations of nano‐TiO₂ and p,p′‐DDT increased oxidativestress by reactive oxygen species (ROS) formation and lipid oxidation. Oxidative stress is a major pathway for DNA and chromosome damage. Dose‐dependent synergistic genotoxicity induced by combined exposure of trace p,p′‐DDT and nano‐TiO₂ suggests a potential environmental risk of nano‐TiO₂ assisted photocatalysis. Environ. Mol. Mutagen., 2010. © 2009 Wiley‐Liss, Inc.     

Can the comet assay be used reliably to detect nanoparticle‐induced genotoxicity?

The comet assay is a sensitive method to detect DNA strand breaks as well as oxidatively damaged DNA at the level of single cells. Today the assay is commonly used in nano‐genotoxicology. In this review we critically discuss possible interactions between nanoparticles (NPs) and the comet assay. Concerns for such interactions have arisen from the occasional observation of NPs in the “comet head”, which implies that NPs may be present while the assay is being performed. This could give rise to false positive or false negative results, depending on the type of comet assay endpoint and NP. For most NPs, an interaction that substantially impacts the comet assay results is unlikely. For photocatalytically active NPs such as TiO₂, on the other hand, exposure to light containing UV can lead to increased DNA damage. Samples should therefore not be exposed to such light. By comparing studies in which both the comet assay and the micronucleus assay have been used, a good consistency between the assays was found in general (69%); consistency was even higher when excluding studies on TiO₂ NPs (81%). The strong consistency between the comet and micronucleus assays for a range of different NPs—even though the two tests measure different endpoints—implies that both can be trusted in assessing the genotoxicity of NPs, and that both could be useful in a standard battery of test methods. Environ. Mol. Mutagen. 56:82–96, 2015. © 2014 Wiley Periodicals, Inc.     

Nanosized titanium dioxide particles do not induce DNA damage in human peripheral blood lymphocytes

Industrial application of titanium dioxide nanoparticles (TiO₂‐NPs) as an additive in pharmaceutical and cosmetic products is increasing. However, the knowledge about the toxicity of this material is still incomplete and data concerning health and environmental safety and results of recent studies on TiO₂ nanotoxicology are inconsistent. The in vitro geno‐ and cytotoxicity of TiO₂‐NPs in the anatase crystal phase was evaluated in human peripheral blood lymphocytes from 10 male donors. Initially, transmission electron microscopy (TEM) was performed to describe particle morphology and size, the degree of particle aggregation, and the intracellular distribution. Cells were exposed to nanoparticles in increasing concentrations of 20, 50, 100, and 200 μg/ml for 24 hr. Cytotoxic effects were analyzed by trypan blue exclusion test and the single‐cell microgel electrophoresis (comet) assay was applied to detect DNA double‐strand breakage. TiO₂‐NPs were sphere shaped with a diameter of 15–30 nm. Despite dispersive pretreatment, a strong tendency to form aggregates was observed. Particles were detected in the cytoplasm of lymphocytes, but also a transfer into the nucleus was seen. The trypan blue exclusion test did not show any decrease in lymphocyte viability, and there was no evidence of genotoxicity in the comet assay for any of the tested concentrations. In conclusion, TiO₂‐NPs reached the cytoplasm as well as the nucleus and did not induce cyto‐ or genotoxic effects in human peripheral blood lymphocytes. Complement investigations on different human cell systems will be performed to estimate the biocompatibility of TiO₂‐NPs. Environ. Mol. Mutagen., 2011. © 2010 Wiley‐Liss, Inc.     

TiO2 nanoparticles induce DNA double strand breaks and cell cycle arrest in human alveolar cells

TiO₂ nanoparticles (NPs) have the second highest global annual production (～3000 tons) among the metal‐containing NPs. These NPs are used as photocatalysts for bacterial disinfection, and in various other consumer products including sunscreen, food packaging, therapeutics, biosensors, surface cleaning agents, and others. Humans are exposed to these NPs during synthesis (laboratory), manufacture (industry), and use (consumer products, devices, medicines, etc.), as well as through environmental exposures (disposal). Hence, there is great concern regarding the health effects caused by exposure to NPs and, in particular, to TiO₂ NPs. In the present study, the genotoxic potential of TiO₂ NPs in A549 cells was examined, focusing on their potential to induce ROS, different types of DNA damage, and cell cycle arrest. We show that TiO₂ NPs can induce DNA damage and a corresponding increase in micronucleus frequency, as evident from the comet and cytokinesis‐block micronucleus assays. We demonstrate that DNA damage may be attributed to increased oxidative stress and ROS generation. Furthermore, genomic and proteomic analyses showed increased expression of ATM, P53, and CdC‐2 and decreased expression of ATR, H2AX, and Cyclin B1 in A549 cells, suggesting induction of DNA double strand breaks. The occurrence of double strand breaks was correlated with cell cycle arrest in G2/M phase. Overall, the results indicate the potential for genotoxicity following exposure to these TiO₂ NPs, suggesting that use should be carefully monitored. Environ. Mol. Mutagen. 56:204–217, 2015. © 2014 Wiley Periodicals, Inc.     

In vivo genotoxicity of estragole in male F344 rats

Estragole, a naturally occurring constituent of various herbs and spices, is a rodent liver carcinogen which requires bio‐activation. To further understand the mechanisms underlying its carcinogenicity, genotoxicity was assessed in F344 rats using the comet, micronucleus (MN), and DNA adduct assays together with histopathological analysis. Oxidative damage was measured using human 8‐oxoguanine‐DNA‐N‐glycosylase (hOGG1) and EndonucleaseIII (EndoIII)‐modified comet assays. Results with estragole were compared with the structurally related genotoxic carcinogen, safrole. Groups of seven‐week‐old male F344 rats received corn oil or corn oil containing 300, 600, or 1,000 mg/kg bw estragole and 125, 250, or 450 mg/kg bw safrole by gavage at 0, 24, and 45 hr and terminated at 48 hr. Estragole‐induced dose‐dependent increases in DNA damage following EndoIII or hOGG1 digestion and without enzyme treatment in liver, the cancer target organ. No DNA damage was detected in stomach, the non‐target tissue for cancer. No elevation of MN was observed in reticulocytes sampled from peripheral blood. Comet assays, both without digestion or with either EndoIII or hOGG1 digestion, also detected DNA damage in the liver of safrole‐dosed rats. No DNA damage was detected in stomach, nor was MN elevated in peripheral blood following dosing with safrole suggesting that, as far both safrole and estragole, oxidative damage may contribute to genotoxicity. Taken together, these results implicate multiple mechanisms of estragole genotoxicity. DNA damage arises from chemical‐specific interaction and is also mediated by oxidative species. Environ. Mol. Mutagen. 56:356–365, 2015. © 2014 Crown copyright.     

Genotoxic effects induced by formaldehyde in human blood and implications for the interpretation of biomonitoring studies

Formaldehyde (FA) was tested for its genotoxicity in human blood cultures. We treated blood samples at the start of the culture to follow FA-induced DNA damage (DNA-protein crosslinks, DPX), its repair and its genetic consequences in form of sister chromatid exchanges (SCE) and micronuclei (MN). Our results clearly indicate that DPX (determined by the comet assay) are induced at FA concentrations of > or =25 microM. DPX induced by FA concentrations up to 100 microM are completely removed before lymphocytes start to replicate. SCE are induced at concentrations >100 microM parallel to the induction of cytotoxicity (measured as reduction of the replication index). MN were not induced by FA concentrations up to 250 microM (the highest analyzable concentration) added at the start of the blood cultures in the cytokinesis-block micronucleus (CBMN) test. FA-induced cytotoxicity (measured as reduction of the nuclear division index) possibly prevented division of damaged cells. MN were only significantly induced in human blood when proliferating cells were exposed to FA during the last cell cycle before preparation. Several human biomonitoring studies reported increased frequencies of SCE and MN in lymphocytes of subjects exposed to FA. Our results characterize the genotoxic potential of FA in cultured lymphocytes and lead to the conclusion that cytogenetic effects of FA are very unlikely to occur in blood cultures of FA-exposed subjects.     

Effects of epigallocatechin gallate and quercetin on oxidative damage to cellular DNA

Phenolic phytochemicals are thought to promote optimal health, partly via their antioxidant effects in protecting cellular components against free radicals. The aims of this study were to assess the free radical-scavenging activities of several common phenolic phytochemicals, and then, the effects of the most potent phenolic phytochemicals on oxidative damage to DNA in cultured cells. Epigallocatechin gallate (EGCG) scavenged the stable free radical, α,α-diphenyl-β-picrylhydrazyl (DPPH), most effectively, while quercetin was about half as effective. Genistein, daidzein, hesperetin, and naringenin did not scavenge DPPH appreciably. Jurkat T-lymphocytes that were pre-incubated with relatively low concentrations of either EGCG or quercetin were less susceptible to DNA damage induced by either a reactive oxygen species or a reactive nitrogen species, as evaluated by the comet assay. More specifically, control cells had a comet score of only 17±5, indicating minimal DNA damage. Cells challenged with 25 μM hydrogen peroxide (H₂O₂) or 100 μM 3-morpholinosydnonimine (SIN-1, a peroxynitrite generator) had comet scores of 188±6 and 125±12, respectively, indicating extensive DNA damage. The H₂O₂-induced DNA damage was inhibited with 10 μM of either EGCG (comet score: 113±23) or quercetin (comet score: 82±7). Similarly, the SIN-1-mediated DNA damage was inhibited with 10 μM of either EGCG (comet score: 79±13) or quercetin (comet score: 72±17). In contrast, noticeable DNA damage was induced in Jurkat T-lymphocytes by incubating with 10-fold higher concentrations (i.e., 100 μM) of either EGCG (comet score: 56±17) or quercetin (comet score: 64±13) by themselves. Collectively, these data suggest that low concentrations of EGCG and quercetin scavenged free radicals, thereby inhibiting oxidative damage to cellular DNA. But, high concentrations of either EGCG or quercetin alone induced cellular DNA damage.     

Evaluation of micronucleus frequencies and DNA damage in glass workers exposed to arsenic

Arsenic (As) is a known human carcinogen; however, very little is known about the health consequences of occupational exposure to As. In the present study, we assessed the genotoxic damage in the blood cells and in the buccal cells of south Indian glass factory workers who are occupationally exposed to As. The As content in the whole blood of 200 workers and 165 controls was evaluated with inductively coupled plasma mass spectrometry. Blood leukocytes from the subjects were monitored for the level of DNA damage using the Comet assay (mean comet tail length); buccal cells were used to determine the frequency of micronuclei (MN). The mean As concentration was significantly higher in the workers (56.76 microg/L) than in the controls (11.74 microg/L) (P < 0.001). The workers also had increased frequencies of MN in the buccal cells and increased levels of DNA damage in leukocytes compared to the controls (P < 0.001). There were significant correlations between the genotoxicity endpoints that were evaluated and blood As concentration, smoking, age, and the duration of working in the factory. Also, a significant correlation was observed between the frequency of MN and comet tail-length for the worker samples. Our findings indicate that chronic occupational exposure to As is genotoxic and that the Comet assay and micronucleus test are useful assays for evaluating genotoxicity in humans occupationally exposed to As.     

Characterization of the genotoxic potential of formaldehyde in V79 cells

Formaldehyde (FA) is known to be genotoxic and mutagenic in proliferating mammalian cells in vitro. The present study was performed to further characterize its genotoxic potential in the V79 Chinese hamster cell line. The induction of DNA strand breaks and DNA-protein cross-links (DPXs) was measured by the comet assay in relationship to the induction of sister chromatid exchanges (SCEs) and micronuclei (MN). Induction of DNA strand breaks was found neither with the standard protocol of the alkaline comet assay nor with modifications using extended electrophoresis times or proteinase K. The concentration-effect relationship for the genotoxic effects was characterized by fitting different curves to the data. A two-phase regression model fitted best in comparison with a linear or a quadratic model and indicated practical thresholds for the induction of SCE and MN. For the induction of DPX as measured by the comet assay, neither a linear concentration-response relationship nor any of the tested models fitted well to the data. Three repeated treatments with genotoxic concentrations of FA with a 3-h interval led to enhanced levels of DPX and MN while the same treatments with a 24-h interval did not enhance FA genotoxicity but suggested adaptive protection against the DNA-damaging action of FA.     

Comparative investigations of the genotoxic effects of metals in the single cell gel (SCG) assay and the sister chromatid exchange (SCE) test

Sodium arsenite (NaAsO₂) and cadmium sulphate (CdSO₄) were tested for their ability to induce genotoxic effects in the single cell gel (SCG) assay and the sister chromatid exchange (SCE) test in human blood cultures in vitro. Both metals induced DNA damage in white blood cells that was expressed and detected as DNA migration in the SCG assay. Dose dependent effects were seen for cadmium in concentrations from 5 × 10^?4-5 × 10^?3 M and for arsenic in concentrations from 2 × 10^?4-1.5 × 10^?3 M. The distribution of DNA migration among cells, a function of dose, revealed that the majority of exposed cells expressed more DNA damage than cells from control cultures and that with increasing length of DNA migration the variability in migration among cells increased as well. Treatment of cells for 2 hr or 24 hr beginning 48 hr after the start of the blood cultures did not increase the SCE frequency in the case of cadmium but caused a small but significant SCE induction with arsenic at the highest concentration. The metal concentrations which could be investigated in the SCE test were much lower due to a strong toxic effect. Metal concentrations which were toxic in the SCE test were without visible effect in the SCG assay. Thus the two endpoints for the determination of genotoxic effects in vitro differed markedly with respect to the detection of genotoxicity induced by metals. These differences and the biological significance of the findings are discussed. © 1994 Wiley-Liss, Inc.     

Genotoxicity of the herbicides alachlor and maleic hydrazide in cultured human lymphocytes

The herbicides alachlor and maleic hydrazide were evaluatedfor genotoxicity in peripheral blood human lymphocyte cultures.Sister-chromatid exchanges (SCE), chromosome aberrations (CA)and micronuclei (MN) were scored as genetic endpoints. To detectpossible metabolic modifications in the genotoxicity of bothherbicides, the cultures for SCE and MN demonstration were alsotreated with S9 fraction. From our results we conclude that,in the absence of metabolic activation, the two herbicides inducesignificant increases in the frequency of SCE, although theconcentrations needed to be effective are very different Thus,alachlor gave positive results at concentrations ranging from1 µg/ml, and maleic hydrazide at concentrations rangingfrom 100 µg/ml. In addition, alachlor appears to be clastogenicin both the CA and MN assays, but only at the highest concentrationtested (20 µg/ml). The co-treatment with the S9 fractionproduced a slight decrease in the induction of SCE with bothherbicides; nevertheless, it does not seem to affect the responsein the MN assay. ³To whom correspondence should be addressed     

Integrated approach to the in vivo genotoxic effects of a titanium dioxide nanomaterial using LacZ plasmid‐based transgenic mice

Titanium dioxide (TiO₂) nanomaterials (NMs) are widely used in a diversity of products including cosmetics, pharmaceuticals, food, and inks, despite uncertainties surrounding the potential health risks that they pose to humans and the environment. Previous studies on the genotoxicity of TiO₂ have reported discrepant or inconclusive findings in both in vitro and in vivo systems. This study explores the in vivo genotoxic potential of a well‐characterized uncoated TiO₂ NM with an average diameter of 22 nm (NM‐102, from JRC repository) using several genotoxicity endpoints in the LacZ plasmid‐based transgenic mouse model. Mice were exposed by intravenous injection to two daily doses of NM‐102: 10 and 15 mg/kg of body weight/day. Micronuclei were analyzed in peripheral blood reticulocytes 42 hr after the last treatment. DNA strand breaks (comet assay) and gene mutations were determined in the spleens and livers of the same animals 28 days after the last treatment. Histopathological and cytological analyses were also performed in liver samples. Genotoxic effects were not detected in mice exposed to the nanosized TiO₂ under the experimental conditions used, despite a moderate inflammatory response that was observed in the liver. Considering the biopersistence of TiO₂ in mouse liver and the moderate inflammatory response, the possibility of a secondary genotoxic effect at higher doses and in conditions that result in a stronger inflammatory response, for example, within a longer time window, should be investigated further. Environ. Mol. Mutagen. 55:500–509, 2014. © 2014 Wiley Periodicals, Inc.     

Carbon nanotubes induce oxidative DNA damage in RAW 264.7 cells

The induction of DNA and chromosome damage following in vitro exposure to carbon nanotubes (CNT) was assessed on the murine macrophage cell line RAW 264.7 by means of the micronucleus (MN) and the comet assays. Exposures to two CNT preparations (single‐walled CNT (SWCNT > 90%) and multiwalled CNT (MWCNT > 90%) were performed in increasing mass concentrations (0.01–100 μg/ml). The frequency of micronuclei was significantly increased in cells treated with SWCNT (at doses above 0.1 μg/ml), whereas MWCNT had the same effect at higher concentrations (1 μg/ml) (P < 0.05). The results of the comet assay revealed that the effects of treatment with SWCNT were detectable at all concentrations tested (1–100 μg/ml); oxidized purines increased significantly, whereas pyrimidines showed a significant increase (P < 0.001) only at the highest concentration (100 μg/ml). In cells treated with MWCNT, an increase in DNA migration due to the oxidative damage to purines was observed at a concentration of 1 and 10 μg/ml, whereas pyrimidines showed a significant increase only at the highest mass concentration tested. However, both SWCNT and MWCNT induced a statistically significant cytotoxic effect at the highest concentrations tested (P < 0.001). These findings suggest that both the MN and comet assays can reliably detect small amount of damaged DNA at both chromosome and nuclear levels in RAW 264.7 cells. Moreover, the modified version of the comet assay allows the specific detection of the induction of oxidative damage to DNA, which may be the underlying mechanism involved in the CNT‐associated genotoxicity. Environ. Mol. Mutagen., 2010. © 2010 Wiley‐Liss, Inc.     

Nonlinear responses for chromosome and gene level effects induced by vinyl acetate monomer and its metabolite,acetaldehyde in TK6 cells

Vinyl acetate monomer (VAM) produced rat nasal tumors at concentrations in the hundreds of parts per million. However, VAM is weakly genotoxic in vitro and shows no genotoxicity in vivo. A European Union Risk Assessment concluded that VAM's hydrolysis to acetaldehyde (AA), via carboxylesterase, is a critical key event in VAM's carcinogenic potential. In the following study, we observed increases in micronuclei (MN) and thymidine kinase (Tk) mutants that were dependent on the ability of TK6 cell culture conditions to rapidly hydrolyze VAM to AA. Heat‐inactivated horse serum demonstrated a high capacity to hydrolyze VAM to AA; this activity was highly correlated with a concomitant increase in MN. In contrast, heat‐inactivated fetal bovine serum (FBS) did not hydrolyze VAM and no increase in MN was observed. AA's ability to induce MN was not impacted by either serum since it directly forms Schiff bases with DNA and proteins. Increased mutant frequency at the Tk locus was similarly mitigated when AA formation was not sufficiently rapid, such as incubating VAM in the presence of FBS for 4 hr. Interestingly, neither VAM nor AA induced mutations at the HPRT locus. Finally, cytotoxicity paralleled genotoxicity demonstrating that a small degree of cytotoxicity occurred prior to increases in MN. These results established 0.25 mM as a consistent concentration where genotoxicity first occurred for both VAM and AA provided VAM is hydrolyzed to AA. This information further informs significant key events related to the mode of action of VAM‐induced nasal mucosal tumors in rats. Environ. Mol. Mutagen. 54:755–768, 2013. © 2013 Wiley Periodicals, Inc.     

Caffeic Acid Genotoxicity: Correlation of the Pig-a Assay with Regulatory Genetic Toxicology In Vivo Endpoints

Caffeic acid is found in variety of fruits and vegetables. It is considered as possible human carcinogen (Group 2B). It is negative in Ames and mouse micronucleus (MN), but positive in mouse lymphoma and chromosomal aberration assays. The objective of this study was to evaluate the in vivo genotoxicity of caffeic acid using three different endpoints: in vivo MN, Pig-a, and comet assay. Two sets of six rats per group were administered vehicle (0.5% hydroxypropyl methylcellulose), 500, 1,000, or 2,000 mg/kg/day of caffeic acid for three consecutive days via oral gavage. One set of animals was used for the Pig-a and MN assay and the other set was used for the comet assay. N-Ethyl N-Nitrosourea was used as positive control for the Pig-a and MN assay, and ethyl methanesulfonate for the comet assay. From one set of animals, peripheral blood was collected on Days −1, 14, and 30 for the Pig-a assay and on Day 4 for the MN assay. The other set of animals was euthanized 3 hr after the last dose; liver and blood were collected for the comet assay. A statistically significant increase in the MN frequency was observed at 2,000 mg/kg/day. No increase in the red blood cells (RBC^CD59-) or reticulocytes (RET^CD59-) Pig-a mutant frequencies was observed on Days 14 or 30. No increase in DNA strand breaks was observed in the peripheral blood or liver in the comet assay. Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc.     

In vitro genotoxicity testing of the furylethylene derivative UC-245 in human cells

The possible genotoxic potential of the 2-furylethylene derivative UC-245 has been evaluated in vitro using human cells as a test system. This compound was synthesized at the Centro de Bioactivos Químicos, Universidad Central de Las Villas (Cuba) and it appears to be effective against leishmaniosis. The induced genetic damage was determined by scoring the frequency of micronuclei (MN) and the frequency of sister chromatid exchanges (SCE) in primary lymphocyte cultures set up from two different donors. The DNA breakage level was also evaluated by the Comet assay, using an established human lymphoblastoid cell line (TK6). For the MN and SCE studies, to detect eventual metabolic modification in the genotoxicity of this compound, the cultures were treated with S9 microsomal fraction. The results obtained indicate that, under the experimental conditions used, the test agent does not induce significant increases in the frequency of micronucleated cells, irrespective of presence/absence of the metabolic fraction, which would indicate a lack of clastogenic and/or aneugenic potential. Nevertheless, a clear and significant increase in the SCE frequency was observed in the treatments without S9. This would support the 2-furylethylene derivative UC-245 inducing DNA primary damage. In addition, the results obtained in the Comet assay also show that UC-245 induces a significant increase in the level of DNA breakage, which would confirm its genotoxicity.     

Caryocar brasiliense camb protects against genomic and oxidative damage in urethane-induced lung carcinogenesis

The antioxidant effects of Caryocar brasiliense Camb, commonly known as the pequi fruit, have not been evaluated to determine their protective effects against oxidative damage in lung carcinogenesis. In the present study, we evaluated the role of pequi fruit against urethane-induced DNA damage and oxidative stress in forty 8-12 week old male BALB/C mice. An in vivo comet assay was performed to assess DNA damage in lung tissues and changes in lipid peroxidation and redox cycle antioxidants were monitored for oxidative stress. Prior supplementation with pequi oil or its extract (15 µL, 60 days) significantly reduced urethane-induced oxidative stress. A protective effect against DNA damage was associated with the modulation of lipid peroxidation and low protein and gene expression of nitric oxide synthase. These findings suggest that the intake of pequi fruit might protect against in vivo genotoxicity and oxidative stress.     

Genotoxic risk and oxidative DNA damage in workers exposed to antimony trioxide

The growing use of antimony (Sb) compounds in industry and the consequent increase in the number of exposed workers make it important to carry out a health risk assessment. The main goal of this study was to assess the genotoxicity of Sb(2)O(3) in occupationally exposed workers. Genotoxicity was evaluated by the sister chromatid exchange (SCE) and micronucleus tests, and the enzyme (Fpg)-modified comet assay. In addition, antimony exposure levels were established by environmental monitoring with personal air samplers. We studied 23 male workers assigned to different fire retardant treatment tasks in the car upholstery industry and a control group of 23 healthy nonexposed males. The exposed workers were divided into two groups on the basis of their tasks and the work cycle: Group A comprised finishing and intermediate inspection operators who directly handled a mixture containing Sb(2)O(3); Group B were jet operators, not directly exposed to the compound. Environmental monitoring detected low Sb exposure levels but significant differences between the two groups, with Group A having the higher exposure level. Cytogenetic analyses showed no difference between exposed workers and controls for micronuclei and SCE. The enzyme-modified comet assay showed a probable relation between moderate levels of oxidative DNA damage and exposure to antimony, with a significantly higher proportion of workers in Group A having oxidative DNA damage compared to controls. The results support the theory that oxidative DNA damage is involved in the genotoxicity of antimony and indicate the need for further research in this field.     

Genotoxicity analysis of two hydroxyfuranones,byproducts of water disinfection,in human cells treated in vitro

In general, water for human consumption is chemically disinfected, usually by adding chlorine. As well as producing safe drinking water however, the chlorine treatment, also results in a number of disinfection byproducts (DBPs). One important class of these DBPs is made up of hydroxyfuranones (HFs). In this article, we report the results of a recent investigation to assess the genotoxicity of two HFs, namely mucobromic acid (MBA) and mucochloric acid (MCA), in cultured human cells. The comet assay is used to measure the induction of primary DNA damage and to determine the DNA repair kinetics and the ability of the tested compounds to cause oxidative damage. In addition, the micronucleus (MN) assay is applied to evaluate chromosome damage. The results of the comet assay reveal that both HFs are clearly genotoxic leading to high levels of DNA breaks, and that MBA is more effective than MCA. According to the comet results, the DNA damage induced by MBA repairs well over time, but not the one induced by MCA. Furthermore, HFs produce high levels of oxidized bases. In contrast, the results from the MN assay, which measures the induction of clastogenic and/or aneugenic effects, are mainly negative for the two HFs tested, although MCA is able to increase significantly the frequency of micronuclei in binucleated TK cells, at the concentration of 10 μM. Environ. Mol. Mutagen. 2009. © 2009 Wiley‐Liss, Inc.