Comet assay responses in human lymphocytes are not influenced by the menstrual cycle: a study in healthy Indian females

Assessment of imidacloprid induced genotoxicity in Pethia conchonius (Rosy barb), a common freshwater fish of India

Imidacloprid is one of the highly efficient, globally used neonicotinoid groups of insecticides. The indiscriminate use of imidacloprid is contaminating large water bodies affecting not only the target organisms but also non-target organisms including fish. The present study aimed to assess the extent of nuclear DNA damage by imidacloprid in Pethia conchonius a freshwater fish in India using comet and micronucleus assays. The LC50 value of imidacloprid was estimated to be 227.33 mg L-1. Based on the LC50-96 h value, three sub-lethal concentrations of imidacloprid, SLC I -18.94 mg L-1, SLC II -28.41 mg L-1 and SLC III -56.83 mg L-1 were used to detect its genotoxic effect at DNA and cellular level. The imidacloprid exposed fishes exhibited higher DNA damage and nuclear abnormalities (p < 0.05) than the control. The %head DNA, %tail DNA, tail length and the frequency of micronuclei with other nuclear abnormalities like blebbed and notched nuclei were significantly higher than the control in a time and concentration-dependent manner. The DNA damage parameters such as %head DNA (29.107 ± 1.843), %tail DNA (70.893 ± 1.843), tail length (361.431 ± 8.455) micronucleus (1.300 ± 0.019), notched (0.844 ± 0.011) and blebbed (0.811 ± 0.011) nuclei were found to be highest for SLC III (56.83 mg L-1) at 96 h. The findings indicate that IMI is highly genotoxic in fish and other vertebrates leading to mutagenic/clastogenic effects. The study will be helpful in optimization of the imidacloprid use.

Effect of Interaction between Chromium(VI) with 17β-Estradiol and Its Metabolites on Breast Cancer Cell Lines MCF-7/WT and MDA-MB-175-VII: Preliminary Study

The number of factors initiating and stimulating the progression of breast cancer are constantly increasing. Estrogens are a risk factor for breast adenocarcinoma, the toxicity of which increases as a result of metabolism and interaction with other factors. Due to the presence of environmental exposure to estrogens and metalloestrogens, we investigated how interactions between estrogens and toxic chromium(VI)[Cr(VI)] affect breast cancer lines and investigated whether estrogens play a protective role. The aim of the study was to investigate the effect of 17β-estradiol and its metabolites: 2-methoxyestradiol (2-MeOE2), 4-hydroxyestradiol (4-OHE2), and 16α-hydroxyestrone (16α-OHE1) in exposure to Cr(VI) on cell viability and DNA cell damage. Two estrogen-dependent breast cancer cell lines, MCF 7/WT and MDA-MB-175-VII, were examined. In addition, the expression of Cu-Zn superoxide dismutase (SOD1) was determined immunocytochemically to elucidate the mechanism of oxidative stress. The effects of single substances and their mixtures were tested in the model of simultaneous and 7-day estrogen pre-incubation. As a result, the viability of MCF-7 and MDA-MB-175-VII cells is lowered most by Cr(VI) and least by 17β-E2. In the combined action of estrogens and metalloestrogens, we observed a protective effect mainly of 17β-E2 against Cr(VI)-induced cytotoxicity. The highest expression of SOD1 was found in MCF-7/WT cells exposed to 17β-E2. Moreover, high apoptosis was caused by both Cr(VI) itself and its interaction with 4-OHE2 and 2-MeOE2. The direction and dynamics of changes in viability are consistent for both lines.

Dynamics of DNA damage response markers, RAD51 and XRCC1, throughout the menstrual cycle and pregnancy in healthy women. Increment during pregnancy and relation to a low titer of antinuclear antibodies

PROBLEM

Antinuclear antibodies (ANA) potentially play a role in the pathogenesis of connective tissue diseases (CTDs); however, they are also detected in healthy individuals. Our understanding of the physiological and pathological origin of ANA is incomplete. Both; female reproductive processes and deficiencies in DNA damage response (DDR) have been independently associated with ANA production. However, the link between these two factors and the presence of ANA is unclear METHOD OF STUDY: A cohort study was conducted on 87 non-pregnant and 51 healthy pregnant women. ANA and the DDR markers X-ray repair cross-complementing 1 (XRCC1) and recombinase (RAD51) were quantified in sera by enzyme-linked immunosorbent assay. Additionally, ANA was detected by indirect immunofluorescence in HEp-2 cells in 1:40 diluted sera during the three phases of the menstrual cycle in non-pregnant women and every trimester in pregnant women RESULTS: The prevalence of ANA+ in healthy women was 26.1%, with no significant differences between pregnant and non-pregnant women. ANA and DDR marker levels did not vary among the three phases of the menstrual cycle or the three trimesters of pregnancy. However, DDR marker levels were higher in pregnant women than in non-pregnant women (p<0.001) and were found to be higher in ANA+ women (XRCC1, p = 0.025; RAD51, p = 0.006) CONCLUSIONS: The menstrual cycle and pregnancy did not influence the levels of DDR markers or ANA in healthy women; however, the DDR was higher in pregnancy and ANA+ women. The results suggest a potential role of DDR in the pathophysiology of ANA. This article is protected by copyright. All rights reserved.

Alteration in DNA structure, molecular responses and Na+ -K+ -ATPase activities in the gill of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) in response to sub-lethal verapamil

The ecotoxicological consequences of residues from pharmaceutical drugs on aquatic biota have necessitated the development of sensitive and reliable techniques to assess the impact of these xenobiotics on aquatic organisms. This study investigated the alteration in DNA structure, molecular responses and the activities of Na⁺ -K⁺ -ATPase and antioxidant enzymes in the gill of Nile tilapia, Oreochromis niloticus, exposed to long-term effects at the concentrations (0.14, 0.28 and 0.57mgL^-1) of verapamil in static renewal system for 15, 30, 45 and 60 days. Evaluation of DNA structure, using single cell gel electrophoresis, revealed certain degree of DNA damages in the gill in a time and concentration-dependent relationship. Transcription of mRNA of superoxide dismutase (sod), catalase (cat) and heat shock protein (hsp70) genes in the gill of the fish showed the genes were up-regulated. Na⁺-K⁺-ATPase activity was inhibited in a concentration and time dependent manner. The indices of oxidative stress biomarkers (lipid peroxidation and carbonyl protein) as well as superoxide dismutase, glutathione peroxidase, glutathione-S-transferase were elevated in the treated fish in comparison to the control. Further, the level of reduced glutathione and catalase activity were inhibited at 0.28mgL^-1 after day 30. Long-term exposure to sub-lethal concentration of verapamil can cause DNA damages, molecular effects and oxidative stress in O. niloticus. The biomarkers analysed can be used as early warning signals in environmental biomonitoring and assessment of drug contamination in aquatic ecosystem.

Biocompatibility of designed MicNo-ZnO particles: Cytotoxicity, genotoxicity and phototoxicity in human skin keratinocyte cells

Recently, designed platelet shaped micron particles that are composed of nano primary particles, called MicNo (=Micron+naNo) particles, have been developed to exploit the benefits of nano size, while removing the adverse effects of nanoparticles. It has been shown that MicNo-ZnO particles exhibit both micron and nanosized particle characteristics. Although physical and chemical properties of MicNo-ZnO particles have been studied, their biocompatibility has not yet been evaluated. Accordingly, the research objective of this study was to evaluate in vitro cytotoxicity, genotoxicity and phototoxicity behaviors of designed MicNo-ZnO particles over human epidermal keratinocyte (HaCaT) cells. MicNo-ZnO particles exhibit much less cytotoxicity with IC₅₀ concentrations between 40 and 50μg/ml, genotoxicity above 40μg/ml and lower photo genotoxicity under UVA on HaCaT than the ZnO nanoparticles. Although their chemistries are the same, the source of this difference in toxicity values may be attributed to size differences between the particles that are probably due to their ability to penetrate into the cells. In the present study, the expansive and detailed in vitro toxicity tests show that the biocompatibility of MicNo-ZnO particles is much better than that of the ZnO nanoparticles. Consequently, MicNo-ZnO particles can be considered an important active ingredient alternative for sunscreen applications due to their safer characteristics with respect to ZnO nanoparticles.

Impaired lysosomal activity mediated autophagic flux disruption by graphite carbon nanofibers induce apoptosis in human lung epithelial cells through oxidative stress and energetic impairment

Background

Graphite carbon nanofibers (GCNF) have emerged as a potential alternative of carbon nanotubes (CNT) for various biomedical applications due to their superior physico-chemical properties. Therefore in-depth understanding of the GCNF induced toxic effects and underlying mechanisms in biological systems is of great interest. Currently, autophagy activation by nanomaterials is recognized as an emerging toxicity mechanism. However, the association of GCNF induced toxicity with this form of cell death is largely unknown. In this study, we have assessed the possible mechanism; especially the role of autophagy, underlying the GCNF induced toxicity.

Methods

Human lung adenocarcinoma (A549) cells were exposed to a range of GCNF concentrations and various cellular parameters were analyzed (up to 48 h). Transmission electron microscopy, immunofluorescent staining, western blot and quantitative real time PCR were performed to detect apoptosis, autophagy induction, lysosomal destabilization and cytoskeleton disruption in GCNF exposed cells. DCFDA assay was used to evaluate the reactive oxygen species (ROS) production. Experiments with N-acetyl-L-cysteine (NAC), 3-methyladenine (3-MA) and LC3 siRNA was carried out to confirm the involvement of oxidative stress and autophagy in GCNF induced cell death. Comet assay and micronucleus (MN) assay was performed to assess the genotoxicity potential.

Results

In the present study, GCNF was found to induce nanotoxicity in human lung cells through autophagosomes accumulation followed by apoptosis via intracellular ROS generation. Mechanistically, impaired lysosomal function and cytoskeleton disruption mediated autophagic flux blockade was found to be the major cause of accumulation rather than autophagy induction which further activates apoptosis. The whole process was in line with the increased ROS level and their pharmacological inhibition leads to mitigation of GCNF induced cell death. Moreover the inhibition of autophagy attenuates apoptosis indicating the role of autophagy as cell death process. GCNF was also found to induce genomic instability.

Conclusion

Our present study demonstrates that GCNF perturbs various interrelated signaling pathway and unveils the potential nanotoxicity mechanism of GCNF through targeting ROS-autophagy-apoptosis axis. The current study is significant to evaluate the safety and risk assessment of fibrous carbon nanomaterials prior to their potential use and suggests caution on their utilization for biomedical research.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-017-0194-4) contains supplementary material, which is available to authorized users.

Effects of different light wavelengths from LEDs on oxidative stress and apoptosis in olive flounder (Paralichthys olivaceus) at high water temperatures

We investigated how different light spectra affect thermal stress in olive flounder (Paralichthys olivaceus), using light emitting diodes (LEDs; blue, 450 nm; green, 530 nm; red, 630 nm) at two intensities (0.3 and 0.5 W/m(2)) at relatively high water temperatures (25 and 30 °C, compared to a control condition of 20 °C). We measured the expression and activity of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), and the levels of plasma hydrogen peroxide (H2O2) and lipid peroxidation (LPO). Furthermore, the levels and mRNA expression of caspase-3 were measured, and terminal transferase dUTP nick end labeling (TUNEL) assays of liver and comet assays were performed. The expression and activity of antioxidant enzymes, as well as plasma H2O2 and LPO levels were significantly higher after exposure to high temperatures, and significantly lower after exposure to green and blue light. Caspase-3 levels and mRNA expression showed a similar pattern. The TUNEL assay showed that apoptosis markedly increased at higher water temperatures, compared with the 20 °C control. In contrast, green light irradiation decreased apoptosis rate. Furthermore, the comet assays showed that nuclear DNA damage was caused by thermal stress, and that green light irradiation played a role in partially preventing this damage. Overall, these results suggest that light with green and blue wavelengths can reduce both high temperature-induced oxidative stress and apoptosis, and that particularly green light is efficient for this. Therefore, green light can play a role in protecting in olive flounder from thermal stress damage.

Effects of melatonin injection or green-wavelength LED light on the antioxidant system in goldfish (Carassius auratus) during thermal stress

We tested the mitigating effects of melatonin injections or irradiation from green-wavelength light-emitting diodes (LEDs) on goldfish (Carassius auratus) exposed to thermal stress (high water temperature, 30 °C). The effects of the two treatments were assessed by measuring the expression and activity levels of the antioxidant enzymes, superoxide dismutase and catalase, plasma hydrogen peroxide, lipid hydroperoxide, and lysozyme. In addition, a comet assay was conducted to confirm that high water temperature damaged nuclear DNA. The expression and activity of the antioxidant enzymes, plasma hydrogen peroxide, and lipid hydroperoxide were significantly higher after exposure to high temperature and were significantly lower in fish that received melatonin or LED light than in those that received no mitigating treatment. Plasma lysozyme was significantly lower after exposure to high temperature and was significantly higher after exposure to melatonin or LED light. The comet assay revealed that thermal stress caused a great deal of damage to nuclear DNA; however, treatment with melatonin or green-wavelength LED light prevented a significant portion of this damage from occurring. These results indicate that, although high temperatures induce oxidative stress and reduce immune system strength in goldfish, both melatonin and green-wavelength LED light inhibit oxidative stress and boost the immune system. LED treatment increased the antioxidant and immune system activity more significantly than did melatonin treatment.

Dietary supplementation of pyrroloquinoline quinone disodium protects against oxidative stress and liver damage in laying hens fed an oxidized sunflower oil-added diet

The protective effects of dietary pyrroloquinoline quinone disodium (PQQ.Na2) supplementation against oxidized sunflower oil-induced oxidative stress and liver injury in laying hens were examined. Three hundred and sixty 53-week-old Hy-Line Gray laying hens were randomly allocated into one of the five dietary treatments. The treatments included: (1) a diet containing 2% fresh sunflower oil; (2) a diet containing 2% thermally oxidized sunflower oil; (3) an oxidized sunflower oil diet with 100 mg/kg of added vitamin E; (4) an oxidized sunflower oil diet with 0.08 mg/kg of PQQ.Na2; and (5) an oxidized sunflower oil diet with 0.12 mg/kg of PQQ.Na2. Birds fed the oxidized sunflower oil diet showed a lower feed intake compared to birds fed the fresh oil diet or oxidized oil diet supplemented with vitamin E (P=0.009). Exposure to oxidized sunflower oil increased plasma malondialdehyde (P<0.001), hepatic reactive oxygen species (P<0.05) and carbonyl group levels (P<0.001), but decreased plasma glutathione levels (P=0.006) in laying hens. These unfavorable changes induced by the oxidized sunflower oil diet were modulated by dietary vitamin E or PQQ.Na2 supplementation to levels comparable to the fresh oil group. Dietary supplementation with PQQ.Na2 or vitamin E increased the activities of total superoxide dismutase and glutathione peroxidase in plasma and the liver, when compared with the oxidized sunflower oil group (P<0.05). PQQ.Na2 or vitamin E diminished the oxidized sunflower oil diet induced elevation of liver weight (P=0.026), liver to BW ratio (P=0.001) and plasma activities of alanine aminotransferase (P=0.001) and aspartate aminotransferase (P<0.001) and maintained these indices at the similar levels to the fresh oil diet. Furthermore, oxidized sunflower oil increased hepatic DNA tail length (P<0.05) and tail moment (P<0.05) compared with the fresh oil group. Dietary supplementation of PQQ.Na2 or vitamin E decreased the oxidized oil diet induced DNA tail length and tail moment to the basal levels in fresh oil diet. These results indicate that PQQ.Na2 is a potential antioxidant and is as effective against oxidized oil-related liver injury in laying hens as vitamin E. The protective effects of PQQ.Na2 against liver damage induced by oxidized oil may be partially due to its role in the scavenging of free radicals, inhibiting of lipid peroxidation and enhancing of antioxidant defense systems.

Concurrent acetylation of FoxO1/3a and p53 due to sirtuins inhibition elicit Bim/PUMA mediated mitochondrial dysfunction and apoptosis in berberine-treated HepG2 cells

Post-translational modifications i.e. phosphorylation and acetylation are pivotal requirements for proper functioning of eukaryotic proteins. The current study aimed to decode the impact of acetylation/deacetylation of non-histone targets i.e. FoxO1/3a and p53 of sirtuins (NAD(+) dependent enzymes with lysine deacetylase activity) in berberine treated human hepatoma cells. Berberine (100 μM) inhibited sirtuins significantly (P<0.05) at transcriptional level as well as at translational level. Combination of nicotinamide (sirtuin inhibitor) with berberine potentiated sirtuins inhibition and increased the expression of FoxO1/3a and phosphorylation of p53 tumor suppressor protein. As sirtuins deacetylate non-histone targets including FoxO1/3a and p53, berberine increased the acetylation load of FoxO1/3a and p53 proteins. Acetylated FoxO and p53 proteins transcriptionally activate BH3-only proteins Bim and PUMA (3.89 and 3.87 fold respectively, P<0.001), which are known as direct activator of pro-apoptotic Bcl-2 family protein Bax that culminated into mitochondria mediated activation of apoptotic cascade. Bim/PUMA knock-down showed no changes in sirtuins' expression while cytotoxicity induced by berberine and nicotinamide was curtailed up to 28.3% (P<0.001) and it restored pro/anti apoptotic protein ratio in HepG2 cells. Sirtuins inhibition was accompanied by decline in NAD(+)/NADH ratio, ATP generation, enhanced ROS production and decreased mitochondrial membrane potential. TEM analysis confirmed mitochondrial deterioration and cell damage. SRT-1720 (1-10 μM), a SIRT-1 activator, when pre-treated with berberine (25 μM), reversed sirtuins expression comparable to control and significantly restored the cell viability (P<0.05). Thus, our findings suggest that berberine mediated sirtuins inhibition resulting into FoxO1/3a and p53 acetylation followed by BH3-only protein Bim/PUMA activation may in part be responsible for mitochondria-mediated apoptosis.

Effect of Oral Contraceptive Pills on the Blood Serum Enzymes and DNA Damage in Lymphocytes Among Users

The continuous use of synthetic hormones as contraceptive pill or hormonal replacement therapy among women is increasing day by day. The widespread use of different formulations as oral contraceptives by women throughout their reproductive cycle has given rise to a serious concern for studying the effects of oral contraceptives on enzymatic profile and DNA damage in peripheral blood lymphocytes among users. The present study was carried out on women taking oral contraceptives. The study was based on the questionnaire having the information of reproductive history, fasting, age, health, nature of menstrual cycle, bleeding and other disease. The profile of the blood serum enzymes i.e. alkaline phosphatase (ALP), gamma glutamyl transferase (GGT), lactate dehydrogenase (LDH), aminotransferases (SGOT and SGPT), serum proteins (albumin and globulin) and DNA damage in lymphocytes was studied among users and non-users. The results of the present study suggest that OCs not only effects enzymatic activity but also results in DNA damage that may vary with the duration of using oral contraceptives. A significant increase in LDH, GGT, SGPT, SGOT, globulin and decrease in ALP as well as albumin was found among users as compared to non-users. The observed DNA damage was more in users as compared to non-users. Hormonal contraceptives seem to exert DNA damage and also have significant effects on blood serum enzymes.

The Comet assay in insects--Status, prospects and benefits for science

The Comet assay has been recently adapted to investigate DNA damage in insects. The first reports of its use in Drosophila melanogaster appeared in 2002. Since then, the interest in the application of the Comet assay to studies of insects has been rapidly increasing. Many authors see substantial potential in the use of the Comet assay in D. melanogaster for medical toxicology studies. This application could allow the testing of drugs and result in an understanding of the mechanisms of action of toxins, which could significantly influence the limited research that has been performed on vertebrates. The possible perspectives and benefits for science are considered in this review. In the last decade, the use of the Comet assay has been described in insects other than D. melanogaster. Specifically, methods to prepare a cell suspension from insect tissues, which is a difficult task, were analyzed and compared in detail. Furthermore, attention was paid to any differences and modifications in the research protocols, such as the buffer composition and electrophoresis conditions. Various scientific fields in addition to toxicological and ecotoxicological research were considered. We expect the Comet assay to be used in environmental risk assessments and to improve our understanding of many important phenomena of insect life, such as metamorphosis, molting, diapause and quiescence. The use of this method to study species that are of key importance to humans, such as pests and beneficial insects, appears to be highly probable and very promising. The use of the Comet assay for DNA stability testing in insects will most likely rapidly increase in the future.

Trichloroethylene-mediated cytotoxicity in human epidermal keratinocytes is mediated by the rapid accumulation of intracellular calcium: Interception by naringenin

Industrial solvents pose a significant threat to the humankind. The mechanisms of their toxicity still remain in debate. Trichloroethylene (TCE) is a widespread industrial solvent responsible for severe liver dysfunction, cutaneous toxicity in occupationally exposed humans. We utilized an in vitro system of human epidermal keratinocyte (HaCaT) cells in this study to avoid complex cell and extracellular interactions. We report the cytotoxicity of organic solvent TCE in HaCaT and its reversal by a natural flavanone, naringenin (Nar). The cytotoxicity was attributed to the rapid intracellular free calcium (Ca(2+)) release, which might lead to the elevation of protein kinase C along with robust free radical generation, instability due to energy depletion, and sensitization of intracellular stress signal transducer nuclear factor κB. These effects were actually seen to induce significant amount of genomic DNA fragmentation. Furthermore, all these effects of TCE were effectively reversed by the treatment of Nar, a natural flavanone. Our studies identify intracellular Ca as a unique target used by organic solvents in the cytotoxicity and highlight the Ca(2+) ion stabilizer properties of Nar.

Increased oxidative DNA damage and decreased expression of base excision repair proteins in airway epithelial cells of women who cook with biomass fuels

To investigate whether biomass burning causes oxidative DNA damage and alters the expression of DNA base excision repair (BER) proteins in airway cells, sputum samples were collected from 80 premenopausal rural biomass-users and 70 age-matched control women who cooked with liquefied petroleum gas. Compared with control the airway cells of biomass-users showed increased DNA damage in alkaline comet assay. Biomass-users showed higher percentage of cells expressing oxidative DNA damage marker 8-oxoguanine and lower percentages of BER proteins OGG1 and APE1 by immunocytochemical staining. Reactive oxygen species (ROS) generation was doubled and level of superoxide dismutase was depleted significantly among biomass-users. The concentrations of particulate matters were higher in biomass-using households which positively correlated with ROS generation and negatively with BER proteins expressions. ROS generation was positively correlated with 8-oxoguanine and negatively with BER proteins suggesting cooking with biomass is a risk for genotoxicity among rural women in their child-bearing age.

Mutagenic and cytotoxic potential of Endosulfan and Lambda-cyhalothrin - in vitro study describing individual and combined effects of pesticides

Excessive use of pesticides poses increased risks to non target species including humans. In the developing countries, lack of proper awareness about the toxic potential of pesticides makes the farmer more vulnerable to pesticide linked toxicities, which could lead to diverse pathological conditions. The toxic potential of a pesticide could be determined by their ability to induce genetic mutations and cytotoxicity. Hence, determination of genetic mutation and cytotoxicity of each pesticide is unavoidable to legislate health and safety appraisal about pesticides. The objective of current investigation was to determine the genotoxic and cytotoxic potential of Endosulfan (EN) and Lambda-cyhalothrin (LC); individually and in combination. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay was utilized to determine cytotoxicity, while two mutant histidine dependent Salmonella strains (TA98, TA100) were used to determine the mutagenicity of EN and LC. Moreover, mutagenicity assay was conducted with and without S9 to evaluate the effects of metabolic activation on mutagenicity. Even though a dose dependent increase in the number of revertant colonies was detected with EN against both bacterial strains, a highly significant (p<0.05) increase in the mutagenicity was detected in TA98 with S9. In comparison, data obtained from LC revealed less mutagenic potential than EN. Surprisingly, the non-mutagenic individual-concentrations of EN and LC showed dose dependent mutagenicity when combined. Combination of EN and LC synergistically induced mutagenicity both in TA98 and TA100. MTT assay spotlighted comparable dose dependent cytotoxicity effects of both pesticides. Interestingly, the combination of EN and LC produced increased reversion and cytotoxicity at lower doses as compared to each pesticide, concluding that pesticide exposure even at sub-lethal doses can produce cytotoxicity and genetic mutations, which could lead to carcinogenicity.

Cerium oxide nanoparticles induced toxicity in human lung cells: role of ROS mediated DNA damage and apoptosis

Cerium oxide nanoparticles (CeO₂ NPs) have promising industrial and biomedical applications. In spite of their applications, the toxicity of these NPs in biological/physiological environment is a major concern. Present study aimed to understand the molecular mechanism underlying the toxicity of CeO₂ NPs on lung adenocarcinoma (A549) cells. After internalization, CeO₂ NPs caused significant cytotoxicity and morphological changes in A549 cells. Further, the cell death was found to be apoptotic as shown by loss in mitochondrial membrane potential and increase in annexin-V positive cells and confirmed by immunoblot analysis of BAX, BCl-2, Cyt C, AIF, caspase-3, and caspase-9. A significant increase in oxidative DNA damage was found which was confirmed by phosphorylation of p53 gene and presence of cleaved poly ADP ribose polymerase (PARP). This damage could be attributed to increased production of reactive oxygen species (ROS) with concomitant decrease in antioxidant “glutathione (GSH)” level. DNA damage and cell death were attenuated by the application of ROS and apoptosis inhibitors N-acetyl-L- cysteine (NAC) and Z-DEVD-fmk, respectively. Our study concludes that ROS mediated DNA damage and cell cycle arrest play a major role in CeO₂ NPs induced apoptotic cell death in A549 cells. Apart from beneficial applications, these NPs also impart potential harmful effects which should be properly evaluated prior to their use.

Assessment of genotoxic and mutagenic potential of hexavalent chromium in the freshwater fish Labeo rohita (Hamilton, 1822)

The present study was undertaken to investigate the genotoxicity and mutagenicity of sublethal concentrations of hexavalent chromium (potassium dichromate) in the Indian major carp, Labeo rohita. The 96 h LC50 value of potassium dichromate estimated was 118 mg L(-1) by probit analysis using SPSS (version 16.0) software. Based on 96 h LC50 value, three sublethal test concentrations of potassium dichromate (29.5, 59.0 and 88.5 mg L(-)(1)) were selected and specimens were exposed in vivo to these test concentrations for 96 h. The mutagenic and genotoxic effects of potassium dichromate were evaluated in gill and blood cells using micronucleus (MN) test and comet assay. In general, significant (p < 0.05) effects due to the concentrations and the exposure durations were observed in exposed specimens. The MN induction was highest at 96 h at all the test concentrations in the peripheral blood. A similar trend was observed for the DNA damage, measured in terms of percentage of tail DNA, in erythrocyte and gill cells. The study indicated hazardous effect of the hexavalent chromium to fish and other aquatic organisms and indirectly to human beings.

Titanium dioxide nanoparticle-induced oxidative stress triggers DNA damage and hepatic injury in mice

BACKGROUND

The use of metal oxide nanoparticles (titanium dioxide) in consumer and industrial products improves their quality but also underscores the possible adverse effects to human and environmental health.

MATERIALS & METHODS

Mice were exposed orally for 14 consecutive days and analyzed for alteration in different hepatic enzymes, histopathological changes, oxidative stress, DNA damage, tumor suppressor and proapoptotic protein expression in liver cells.

RESULTS

We observed a significant alteration in the level of hepatic enzymes and liver histopathology at a dose of 100 mg/kg body weight. Significant oxidative DNA damage was observed in liver cells, which could be attributed to oxidative stress. In addition, the increased expression of p53, BAX, caspase-3 and -9 proteins and decreased expression of antiapoptotic protein Bcl-2, suggest activation of the intrinsic pathway of apoptosis.

CONCLUSION

High accumulation of titanium dioxide nanoparticles in the liver tissue would cause DNA damage and apoptosis through the intrinsic pathway.

DNA damage and oxidative stress modulatory effects of glyphosate-based herbicide in freshwater fish, Channa punctatus

The present study was undertaken to evaluate the genotoxic and oxidative stress modulatory effects of commercial formulation of glyphosate-based herbicide (Roundup(®)) in freshwater fish Channa punctatus. Three sublethal test concentrations of the herbicide viz., SL-I (1/10th of LC50=∼3.25mgL(-1)), SL-II (1/8th of LC50=∼4.07mgL(-1)) and SL-III (1/5th of LC50=∼6.51mgL(-1)) were calculated using 96-LC50 value and the test specimens were exposed to these concentrations. Blood and gill cells of the exposed specimens were sampled on day 1, 7, 14, 21, 28 and 35 to examine the DNA damage using comet assay and to assess the alteration in lipid peroxidation and antioxidant enzymes activities. The highest DNA damage was observed on day 14 at all test concentrations followed by gradual non-linear decline. Induction of oxidative stress in the blood and gill cells were evidenced by increased lipid peroxidation level, while antioxidants namely superoxide dismutase, catalase and glutathione reductase responded in a concentration-dependent manner. The results supported the integrated use of comet and antioxidant assays in determining the toxicity of water pollutants which could be used as part of monitoring programs.

Zinc oxide nanoparticles induce oxidative DNA damage and ROS-triggered mitochondria mediated apoptosis in human liver cells (HepG2)

The wide scale use of Zinc oxide (ZnO) nanoparticles in the world consumer market makes human beings more prone to the exposure to ZnO nanoparticles and its adverse effects. The liver, which is the primary organ of metabolism, might act as a major target organ for ZnO nanoparticles after they gain entry into the body through any of the possible routes. Therefore, the aim of the present study was to assess the apoptotic and genotoxic potential of ZnO nanoparticles in human liver cells (HepG2) and the underlying molecular mechanism of its cellular toxicity. The role of dissolution in the toxicity of ZnO nanoparticles was also investigated. Our results demonstrate that HepG2 cells exposed to 14-20 μg/ml ZnO nanoparticles for 12 h showed a decrease in cell viability and the mode of cell death induced by ZnO nanoparticles was apoptosis. They also induced DNA damage which was mediated by oxidative stress as evidenced by an increase in Fpg sensitive sites. Reactive oxygen species triggered a decrease in mitochondria membrane potential and an increase in the ratio of Bax/Bcl2 leading to mitochondria mediated pathway involved in apoptosis. In addition, ZnO nanoparticles activated JNK, p38 and induced p53(Ser15) phosphorylation. However, apoptosis was found to be independent of JNK and p38 pathways. This study investigating the effects of ZnO nanoparticles in human liver cells has provided valuable insights into the mechanism of toxicity induced by ZnO nanoparticles.

Comparative evaluation of environmental contamination and DNA damage induced by electronic-waste in Nigeria and China

In the last decade, China and Nigeria have been prime destinations for the world's e-waste disposal leading to serious environmental contamination. We carried out a comparative study of the level of contamination using soils and plants from e-waste dumping and processing sites in both countries. Levels of polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were analyzed using gas chromatography/spectrophotometry and heavy metals using atomic absorption spectrophotometry. DNA damage was assayed in human peripheral blood lymphocytes using an alkaline comet assay. Soils and plants were highly contaminated with toxic PAHs, PCBs, PBDEs, and heavy metals in both countries. Soil samples from China and plant samples from Nigeria were more contaminated. There was a positive correlation between the concentrations of organics and heavy metals in plant samples and the surrounding soils. In human lymphocytes, all tested samples induced significant (p<0.05) concentration-dependent increases in DNA damage compared with the negative control. These findings suggest that e-waste components/constituents can accumulate, in soil and surrounding vegetation, to toxic and genotoxic levels that could induce adverse health effects in exposed individuals.

Induction of oxidative stress, DNA damage and apoptosis in mouse liver after sub-acute oral exposure to zinc oxide nanoparticles

Zinc oxide (ZnO) nanoparticles are finding applications in a wide range of products including cosmetics, food packaging, imaging, etc. This increases the likelihood of human exposure to these nanoparticles through dermal, inhalation and oral routes. Presently, the majority of the studies concerning ZnO nanoparticle toxicity have been conducted using in vitro systems which lack the complex cell-cell, cell-matrix interactions and hormonal effects found in the in vivo scenario. The present in vivo study in mice was aimed at investigating the oral toxicity of ZnO nanoparticles. Our results showed a significant accumulation of nanoparticles in the liver leading to cellular injury after sub-acute oral exposure of ZnO nanoparticles (300 mg/kg) for 14 consecutive days. This was evident by the elevated alanine aminotransferase (ALT) and alkaline phosphatase (ALP) serum levels and pathological lesions in the liver. ZnO nanoparticles were also found to induce oxidative stress indicated by an increase in lipid peroxidation. The DNA damage in the liver and kidney cells of mice was evaluated by the Fpg-modified Comet assay which revealed a significant (p<0.05) increase in the Fpg-specific DNA lesions in liver indicating oxidative stress as the cause of DNA damage. The TUNEL assay revealed an induction of apoptosis in the liver of mice exposed to ZnO nanoparticles compared to the control. Our results conclusively demonstrate that sub-acute oral exposure to ZnO nanoparticles in mice leads to an accumulation of nanoparticles in the liver causing oxidative stress mediated DNA damage and apoptosis. These results also suggest the need for a complete risk assessment of any new engineered nanoparticle before its arrival into the consumer market.

Chronic inhalation of biomass smoke is associated with DNA damage in airway cells: involvement of particulate pollutants and benzene

This study examined whether indoor air pollution from biomass fuel burning induces DNA damage in airway cells. For this, sputum cells were collected from 56 premenopausal rural women who cooked with biomass (wood, dung, crop residues) and 49 age-matched controls who cooked with cleaner liquefied petroleum gas. The levels of particulate matters with diameters of less than 10 and 2.5 µm (PM(10) and PM(2.5)) in indoor air were measured using a real-time aerosol monitor. Benzene exposure was monitored by measuring trans,trans-muconic acid (t,t-MA) in urine by HPLC-UV. DNA damage was examined by alkaline comet assay in sputum cells. Generation of reactive oxygen species (ROS) and level of superoxide dismutase (SOD) in sputum cells were measured by flow cytometry and spectrophotometry, respectively. Compared with controls, biomass users had 4 times higher tail percentage DNA, 37% more comet tail length and 5 times more Olive tail moment (p < 0.001) in inflammatory and epithelial cells in sputum, suggesting extensive DNA damage. In addition, women who cooked with biomass had 6 times higher levels of urinary t,t-MA and 2-fold higher levels of ROS generation concomitant with 28% depletion of SOD. Indoor air of biomass-using households had 2-4 times more PM(10) and PM(2.5) than that of controls. After controlling potential confounders, positive association was found between DNA damage parameters, particulate pollution, urinary t,t-MA and ROS. Thus, long-term exposure to biomass smoke induces DNA damage in airway cells and the effect was probably mediated, at least in part, by oxidative stress generated by inhaled particulate matter and benzene.

Are endogenous sex hormones related to DNA damage in paradoxically sleep-deprived female rats?

The aim of this investigation was to evaluate overall DNA damage induced by experimental paradoxical sleep deprivation (PSD) in estrous-cycling and ovariectomized female rats to examine possible hormonal involvement during DNA damage. Intact rats in different phases of the estrous cycle (proestrus, estrus, and diestrus) or ovariectomized female Wistar rats were subjected to PSD by the single platform technique for 96 h or were maintained for the equivalent period as controls in home-cages. After this period, peripheral blood and tissues (brain, liver, and heart) were collected to evaluate genetic damage using the single cell gel (comet) assay. The results showed that PSD caused extensive genotoxic effects in brain cells, as evident by increased DNA migration rates in rats exposed to PSD for 96 h when compared to negative control. This was observed for all phases of the estrous cycle indistinctly. In ovariectomized rats, PSD also led to DNA damage in brain cells. No significant statistically differences were detected in peripheral blood, the liver or heart for all groups analyzed. In conclusion, our data are consistent with the notion that genetic damage in the form of DNA breakage in brain cells induced by sleep deprivation overrides the effects related to endogenous female sex hormones.

DNA damaging potential of zinc oxide nanoparticles in human epidermal cells

At present, more than 20 countries worldwide are manufacturing and marketing different varieties of nanotech-based consumer products of which cosmetics form the largest category. Due to the extremely small size of the nanoparticles (NPs) being used, there is a concern that they may interact directly with macromolecules such as DNA. The present study was aimed to assess the genotoxicity of zinc oxide (ZnO) NPs, one of the widely used ingredients of cosmetics, and other dermatological preparations in human epidermal cell line (A431). A reduction in cell viability as a function of both NP concentration as well as exposure time was observed. ZnO NPs demonstrated a DNA damaging potential as evident from an increased Olive tail moment (OTM) of 2.13 +/- 0.12 (0.8 g/ml) compared to control 1.37 +/- 0.12 in the Comet assay after an exposure of 6 h. ZnO NPs were also found to induce oxidative stress in cells indicated by depletion of glutathione (59% and 51%); catalase (64% and 55%) and superoxide dismutase (72% and 75%) at 0.8 and 0.08 g/ml respectively. Our data demonstrates that ZnO NPs even at low concentrations possess a genotoxic potential in human epidermal cells which may be mediated through lipid peroxidation and oxidative stress. Hence, caution should be taken in their use in dermatological preparations as well as while handling.

Multipronged evaluation of genotoxicity in Indian petrol-pump workers

Petrol (gasoline) contains a number of toxicants. This study used human biomonitoring to evaluate the genotoxic effects of exposure to benzene in petrol fumes in 100 Indian petrol-pump workers (PPWs) and an equal number of controls. The study was corroborated with in silico assessments of the Comet assay results from the human biomonitoring study. An in vitro study in human lymphocytes was also conducted to understand the genotoxicity of benzene and its metabolites. In a subset of the population studied, higher blood benzene levels were detected in the PPWs (n = 39; P < 0.01) than the controls (n = 18), and 100-250 ppb benzene was also detected in air samples from the petrol pumps. PPWs had higher levels of DNA damage than the controls (P < 0.01). In addition, the micronucleus assay was performed on lymphocytes from a subset of the subjects, and the micronucleus frequency for PPWs was significantly higher (n = 39; 14.79 +/- 3.92 per thousand) than the controls (n = 18; 7.54 +/- 3.00 per thousand). Human lymphocytes were treated in vitro with benzene and several of its metabolites and assayed for DNA damage with the Comet assay. Benzene and its metabolites produced significant (P < 0.05) levels of DNA damage at and above concentrations of 10 microM. The metabolite, p-benzoquinone, produced the greatest amount of DNA damage, followed by hydroquinone > benzene > catechol > 1,2,4,-benzenetriol > muconic acid. This study demonstrates that, using sensitive techniques, it is possible to detect human health risks at an early stage when intervention is possible. possible.

Genotoxicity evaluation of low doses of clodinafop-propargyl to the silkworm Bombyx mori using alkaline single-cell gel electrophoresis

In the present study, DNA damage caused by clodinafop-propargyl was evaluated in silkworm, Bombyx mori, by the alkaline single-cell gel electrophoresis (SCGE). The second, fourth and fifth instar larvae of silkworm were exposed to clodinafop-propargyl by oral feeding with mulberry leaves treated using the different concentration of 30, 60, 120, 240, 480mgL(-1), respectively. The results showed that comet percentage, the head DNA percentage, tail DNA percentage, tail length, tail moment and olive moment of the five tested groups were significantly different from the controlled group (P<0.01). A statistically significant (olive tail moment, P<0.01) dose-dependent increase in DNA damage was observed in silkworm. In addition, the significant dose-dependent reduce in percentage of cocooning and pupating was found in the second instar larvae of silkworm exposed to clodinafop-propargyl. To our knowledge, this was the first report describing the genotoxicity assessment of pesticide using silkworm by the alkaline SCGE.

Evaluation of DNA damage in Chinese toad (Bufo bufo gargarizans) after in vivo exposure to sublethal concentrations of four herbicides using the comet assay

Chinese toad, Bufo bufo gargarizans, is frequently found in rice fields, muddy ponds, wetlands and other aquatic ecosystems in China. Because of its habitat, it has many chances of being exposed to pesticides, such as acetochlor, butachlor, chlorimuron-ethyl, and paraquat, which are extensively used in rice or cereal fields. Amphibians may serve as model organisms for determining the genotoxic effects of pollutants contaminating these areas. In the present study DNA damage was evaluated in the Chinese toad using the comet assay, as a potential tool for the assessment of ecogenotoxicity. The first step was to determine the acute toxicity of the above-mentioned herbicides. In acute tests, tadpoles were exposed to a series of relatively high concentrations of acetochlor, butachlor, chlorimuron-ethyl, and paraquat for 96 h. The LC(50 )(96 h) of acetochlor, butachlor, chlorimuron-ethyl and paraquat were measured as 0.76, 1.32, 20.1 and 164 mg l(-1), respectively. Also, negative effects on the behavior of tadpoles were observed with acetochlor, butachlor, and paraquat. Secondly, the comet assay was used for detecting DNA damage in Chinese toad tadpoles exposed to sublethal concentrations of four herbicides. Significant (P < 0.05) concentration-dependent increase in DNA damage (as indicated by tail length, tail moment, olive tail moment) were observed from erythrocytes of tadpoles exposed to sublethal concentrations of acetochlor, butachlor, paraquat, and methyl methanesulfonate, except chlorimuron-ethyl. To our knowledge, this is the first report describing the use of Bufo bufo gargarizans for genotoxicity assessment of herbicides.

Comet assay: a reliable tool for the assessment of DNA damage in different models

New chemicals are being added each year to the existing burden of toxic substances in the environment. This has led to increased pollution of ecosystems as well as deterioration of the air, water, and soil quality. Excessive agricultural and industrial activities adversely affect biodiversity, threatening the survival of species in a particular habitat as well as posing disease risks to humans. Some of the chemicals, e.g., pesticides and heavy metals, may be genotoxic to the sentinel species and/or to non-target species, causing deleterious effects in somatic or germ cells. Test systems which help in hazard prediction and risk assessment are important to assess the genotoxic potential of chemicals before their release into the environment or commercial use as well as DNA damage in flora and fauna affected by contaminated/polluted habitats. The Comet assay has been widely accepted as a simple, sensitive, and rapid tool for assessing DNA damage and repair in individual eukaryotic as well as some prokaryotic cells, and has increasingly found application in diverse fields ranging from genetic toxicology to human epidemiology. This review is an attempt to comprehensively encase the use of Comet assay in different models from bacteria to man, employing diverse cell types to assess the DNA-damaging potential of chemicals and/or environmental conditions. Sentinel species are the first to be affected by adverse changes in their environment. Determination of DNA damage using the Comet assay in these indicator organisms would thus provide information about the genotoxic potential of their habitat at an early stage. This would allow for intervention strategies to be implemented for prevention or reduction of deleterious health effects in the sentinel species as well as in humans.

In vitro induction of cytotoxicity and DNA strand breaks in CHO cells exposed to cypermethrin, pendimethalin and dichlorvos

The indiscriminate use of pesticides and herbicides to increase crop productivity has aroused a great concern among the environmental and health scientists due to their adverse effects in both target as well as non-target species. Although substantial information is available regarding their environmental and ecological impact, not much is known in regard to its toxicity in the mammalian system. Therefore a study was conducted for the assessment of cytotoxic and genotoxic effects of cypermethrin (Type II pyrethroid) dichlorvos (organophosphate) and pendimethalin (dinitroaniline herbicide) in Chinese hamster ovary (CHO) cells. CHO cells were exposed to 1 microM, 10 microM, 100 microM, 1000 microM, and 10,000 microM, cypermethrin, pendimethalin and dichlorvos for 3h and cytotoxicity was assessed by MTT assay. Their genotoxic potential was also evaluated by Comet assay. The results demonstrate that dichlorvos and pendimethalin exhibited higher extent of cytotoxicity as compared to cypermethrin. A significant (p<0.05) concentration dependent increase in DNA damage was observed with dichlorvos (0.01 microM and above) and pendimethalin (0.1 microM and above) as evident by Comet assay parameters viz., Olive tail moment (arbitrary units), tail DNA (%) and tail length (muM). Cypermethrin induced a significant (p<0.05) DNA damage only at higher concentrations (1000 and 5000 microM). Our data indicates that these chemicals produce cytotoxicity and DNA damage in mammalian cells and should be used with caution.

Lack of genotoxicity induced by endogenous and synthetic female sex hormones in peripheral blood cells detected by alkaline comet assay

The etiology of hormone-induced cancers has been considered to be a combination of genotoxic and epigenetic events. Currently, the Comet assay is widely used for detecting genotoxicity because it is relatively simple, sensitive, and capable of detecting various kinds of DNA damage. The present study evaluates the genotoxic potential of endogenous and synthetic sex hormones, as detected by the Comet assay. Blood cells were obtained from 12 nonsmoking and 12 smoking women with regular menstrual cycles and from 12 nonsmoking women taking low-dose oral contraceptives (OC). Peripheral blood samples were collected at three phases of the menstrual cycle (early follicular, mean follicular, and luteal phases), or at three different moments of oral contraceptive intake. Three blood samples were also collected from 12 healthy nonsmoking men, at the same time as oral contraceptive users. Results showed no significant difference in the level of DNA damage among the three moments of the menstrual cycle either in nonsmoking and smoking women, or between them. No significant difference in DNA damage was also observed among oral contraceptive users, nonusers, and men. Together, these data indicate lack of genotoxicity induced by the physiological level of the female sex hormones and OC as assessed by the alkaline Comet assay. In conclusion, normal fluctuation in endogenous sex hormones and use of low-doses of oral contraceptive should not interfere with Comet assay data when this technique is used for human biomonitoring.

Influence of endogenous and synthetic female sex hormones on human blood cells in vitro studied with comet assay

The comet assay has been conducted with numerous cell lines to assess in vitro genotoxicity. In order to use the comet assay as part of an in vitro test for evaluating genotoxicity, however, there are cell-specific factors that need to be better understood. In this present study we have evaluated some factors that may impact upon the DNA damage detected in whole blood (WB) cells and lymphocytes (ILs). Experiments were conducted comparing responses of both cells, and investigating the effects of the female hormonal cycle, and oral contraceptive (OC) use on DNA damage detection in the in vitro comet assay, at three sampling time. No significant differences were detected in the basal levels of DNA damage detected in ILs and WB cells from women OC users and non-users and from men. Basal DNA damage in ILs was unaffected by gender and stage of the menstrual cycle or the stage of the treatment schedule. Our results also indicated that the H2O2 induces DNA damage in human lymphocytes independently of gender, low-dose OC use and hormonal fluctuation. However, data showed that in 3rd sampling of menstrual cycle, lymphocytes were more resistant to H2O2-induced DNA damage than those from OC users and men.

DNA damage induced in human peripheral blood lymphocytes by industrial solid waste and municipal sludge leachates

Exposure of humans to toxic compounds occurs mostly in the form of complex mixtures. Leachates, consisting of mixtures of many chemicals, are a potential risk to human health. In the present study, leachates of solid wastes from a polyfiber factory (PFL), an aeronautical plant (AEL), and a municipal sludge leachate (MSL) were assessed for their ability to induce DNA damage in human peripheral blood lymphocytes using the alkaline Comet assay. The leachates also were examined for their physical and chemical properties. Lymphocytes were incubated with 0.5-15.0% concentrations (pH range 7.1-7.4) of the test leachates for 3 hr at 37 degrees C, and treatment with 1 mM ethyl methanesulfonate served as a positive control. All three leachates induced significant (P < 0.05), concentration-dependent increases in DNA damage compared with the negative control, as measured by increases in Olive tail moment (arbitrary units), tail DNA (%), and tail length (mum). A comparison of these variables among the treatment groups indicated that the MSL induced the most DNA damage. Inductively coupled plasma emission spectrometry analysis of the leachates indicated that they contained high concentrations of heavy metals, viz. iron, manganese, nickel, zinc, cadmium, chromium, and lead. The individual, synergistic, or antagonistic effects of these chemicals in the leachates may be responsible for the DNA damage. Our data indicate that the ever-increasing amounts of leachates from waste landfill sites have the potential to induce DNA damage and suggest that the exposure of human populations to these leachates may lead to adverse health effects.

DNA damage and mutagenicity induced by endosulfan and its metabolites

Endosulfan is a widely used broad-spectrum organochlorine pesticide, which acts as a contact and stomach poison. Nontarget species, such as cattle, fish, birds, and even humans, are also affected. Studies on the genotoxicity and mutagenicity of endosulfan have been inconsistent and nothing is known about the genotoxicity of its metabolites. In the present study, endosulfan (as a commercial isomeric mixture and as the alpha- and beta-isomers), and metabolites of endosulfan (the sulfate, lactone, ether, hydroxyether, and diol derivatives) were assayed for their ability to induce DNA damage in Chinese hamster ovary (CHO) cells and human lymphocytes using the Comet assay and were assayed for their mutagenicity using the Salmonella reversion assay (Ames test with TA98, TA97a, TA102, TA104, and TA100, with and without S9 activation). The compounds produced statistically significant (P < 0.01), concentration-dependent (0.25-10 microM) increases in DNA damage in both CHO cells and human lymphocytes. Endosulfan lactone caused the most DNA damage in CHO cells, while the isomeric mixture of endosulfan produced the greatest response in lymphocytes. The test compounds also were mutagenic in Salmonella strains at concentrations of 1-20 mug/plate (P < 0.05), with TA98 being the most sensitive strain and the diol and hydroxyether metabolites producing the highest responses. The results indicate that exposure to sublethal doses of endosulfan and its metabolites induces DNA damage and mutation. The contribution of the metabolites to the genotoxicity of the parent compound in Salmonella and mammalian cells, however, is unclear, and the pathways leading to bacterial mutation and mammalian cell DNA damage appear to differ.

Evaluation of the alkaline Comet assay conducted with the wetlands plant Bacopa monnieri L. as a model for ecogenotoxicity assessment

Wetlands play a key role in maintaining environmental quality, and wetlands plants could serve as model organisms for determining the genotoxic effects of pollutants contaminating these areas. In the present study, DNA damage was evaluated in a wetlands plant, Bacopa monnieri L., as a potential tool for the assessment of ecogenotoxicity. The Comet assay was used for detecting DNA damage in B. monnieri exposed to two model mutagens, ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS). Significant (P < 0.05) dose-dependent increases in DNA damage were observed following treatments conducted by exposing both isolated nuclei (acellular or in vitro exposure) and whole plants (in vivo exposure) to 0.01-5 mM EMS and 0.05-100 microM MMS for 2 hr at (26 +/- 2) degrees C. The assay was then used to evaluate the genotoxic potential of cadmium (Cd), a wetlands contaminant. In vitro exposure of nuclei from untreated leaves to 0.001-200 microM Cd for 2 hr resulted in significant (P < 0.05) levels of DNA damage. Cd concentrations >or=0.01 microM induced DNA damage as evidenced by increases in the Olive tail moment. In vivo exposure of plants to 0.01-500 microM Cd for 2, 4, and 18 hr resulted in dose- and time-dependent increases in DNA damage in the nuclei isolated from roots and leaves. Cd-induced DNA damage was greater in roots than leaves. To our knowledge, this is the first report describing the use of a wetlands plant for genotoxicity assessment, using the Comet assay.

DNA damage in bone marrow and blood cells of mice exposed to municipal sludge leachates

Leachates of municipal solid waste from unsecured disposal sites contaminate sources of potable water and affect human health. In the present study, we have used the Comet assay to evaluate the DNA damage in mice exposed to municipal sludge leachates. Ten percent leachates were prepared from municipal sludge obtained from two different disposal drains. Male Swiss albino mice were treated daily with 0.1-0.4 ml of the leachates by oral gavage for 15 days, and the DNA damage was evaluated in bone marrow and blood using Olive tail moment, % tail DNA, and tail length as measures of DNA damage. Physicochemical and metal analysis of the leachates detected the presence of cadmium, chromium, copper, nickel, lead, and zinc, as well as elevated concentrations of sulfate and nitrate. Both of the leachates produced significant dose-responsive increases in DNA damage in both mouse tissues. There were no significant differences in the responses for any of the Comet endpoints between tissues (for the same leachate sample) or between leachate samples (for the same tissue). The results of this study indicate that municipal waste leachates produce DNA damage in vivo.

DNA damage in lymphocytes of Indian rickshaw pullers as measured by the alkaline Comet assay

Rickshaw pullers (RPs) engage in strenuous physical activity and are exposed to the air pollutants found in urban environments. Air pollutants and the reactive oxygen species generated by the physical activity both potentially can damage DNA. In the present study, the Comet assay, a sensitive tool for measuring DNA damage in single cells, was used to study genomic DNA damage in lymphocytes of Indian RPs. The study evaluated DNA damage in 118 healthy male volunteers, including 63 RPs whose work demanded high levels of physical activity for 7-9 hr/day, and 55 controls matched for age, habits, socio-economic status, and exposure to air pollution. A significant increase was found for the mean Olive tail moment (arbitrary units) among the RPs (4.13 +/- 0.11; P < 0.001) in comparison with the controls (3.21 +/- 0.10). Likewise, comet tail length (microm) (RPs: 58.98 +/- 1.01 vs. controls: 52.38 +/- 1.24) and tail DNA (%) (RPs: 13.52 +/- 0.31 vs. controls: 10.04 +/- 0.24) were also significantly higher for RPs compared with those of their matched controls (both, P < 0.001). To our knowledge, this is the first demonstration that physical activity due to occupation can produce DNA damage in peripheral lymphocytes.