In vitro testing for genotoxicity of the herbicide terbutryn: cytogenetic and primary DNA damage

Comet assay and hormesis

The paper provides the first assessment of the occurrence of hormetic dose responses using the Comet assay, a genotoxic assay. Using a priori evaluative criteria based on the Hormetic Database on peer-reviewed comet assay experimental findings, numerous examples of hormetic dose responses were obtained. These responses occurred in a large and diverse range of cell types and for agents from a broad range of chemical classes. Limited attempts were made to estimate the frequency of hormesis within comet assay experimental studies using a priori entry and evaluative criteria, with results suggesting a frequency in the 40% range. These findings are important as they show that a wide range of genotoxic chemicals display evidence that is strongly suggestive of hormetic dose responses. These findings have significant implications for study design issues, including the number of doses selected, dose range and spacing. Likewise, the widespread occurrence of hormetic dose responses in this genotoxic assay has important risk assessment implications.

Application of QSARs in identification of mutagenicity mechanisms of nitro and amino aromatic compounds against Salmonella typhimurium species

In an attempt to describe the underlying causes of mutagenicity mainly due to organic chemicals, quantitative structure-activity relationship (QSAR) models have been developed using two different Salmonella typhimurium mutagenicity endpoints with or without presence of liver metabolic microsomal enzymes (S9) namely TA98-S9 and TA98 + S9. The models were developed using simple 2D variables having definite physicochemical meaning calculated from Dragon, SiRMS, and PaDEL-descriptor software tools. Stepwise regression followed by partial least squares (PLS) regression was used in model development following the strict OECD guidelines for QSAR model development and validation. The models were validated using coefficient of determination R², cross-validation coefficient Q²_LOO (leave one out) while the test set predictions were analyzed using Q²F₁ (coefficient of determination for the test set). Several other internationally accepted validation metrics like MAE_95%train, average r_m(LOO)² and Δr_m(LOO)² (for the training set) were used to check model robustness while predictive efficiency was evaluated using MAE_95%test, average r_m² and Δr_m² (for the test set). The scope of predictions was defined by applicability domain analysis using the DModX approach, a recommended tool for PLS models. The major contributing features related to mutagenicity include lipophilicity, electronegativity, branching and unsaturation, etc. The present manuscript is the first attempt to undertake modeling of two different endpoints (TA98-S9 and TA98 + S9) in order to explore major contributing molecular features linked directly or indirectly to mutagenicity.

Results of buccal micronucleus cytome assay in pesticide-exposed and non-exposed group

Since many different pesticides have been used occupationally, there have been inconsistent results regarding DNA damages among greenhouse workers. Thus, the aim of the study is to evaluate DNA damages, cell death, and chromosomal instability by using the buccal micronucleus cytome (BMcyt) assay in greenhouse workers and to compare those with a non-exposed group. The BMcyt assay was applied to the exfoliated buccal cell samples collected from 66 pesticide-exposed and 50 non-exposed individuals. We evaluated the frequency of micronucleus (MN), nuclear bud (NBUD), binucleated (BN) cells, and karyolitic (KL), pyknotic (PY), and karyorrhectic (KH) cells. The results showed that the MN, BN, PY, and KH frequencies of the pesticide-exposed group were significantly higher than those of the controls (P ˂ 0.05, P ˂ 0.05, P ˂ 0.01, and P ˂ 0.05, respectively). We observed that the MN, BN, PY, and KH frequencies in the autumn were statistically different compared with those in the control group (P = 0.037 for MN, P = 0.001 for BN, P = 0.016 for PY, and P = 0.033 for KH). The same comparison was done in the spring for the control, and there was a statistically significant difference for MN (P = 0.046) and PY (P = 0.014). We can conclude that pesticide exposure in greenhouse workers was one of the factors that altered DNA damages, cell death, and chromosomal instability in oral mucosa cells.

Genotoxicity of amorphous silica nanoparticles: Status and prospects

Amorphous silica nanoparticles (SNPs) are widely used in biomedical applications and consumer products. Little is known, however, about their genotoxicity and potential to induce gene expression regulation. Despite recent efforts to study the underlying mechanisms of genotoxicity of SNPs, inconsistent results create a challenge. A variety of factors determine particle-cell interactions and underlying mechanisms. Further, high-throughput studies are required to carefully assess the impact of silica nanoparticle physicochemical properties on induction of genotoxic response in different cell lines and animal models. In this article, we review the strategies available for evaluation of genotoxicity of nanoparticles (NPs), survey current status of silica nanoparticle gene alteration and genotoxicity, discuss particle-mediated inflammation as a contributing factor to genotoxicity, identify existing gaps and suggest future directions for this research.

Epilobium angustifolium L.: A medicinal plant with therapeutic properties

Epilobium angustifolium L. is a medicinal plant belonging to the Onagraceae family, which includes more than 200 different species from all over the world. Traditional medicinal applications include treatment of prostate, gastrointestinal, menstrual disorders and recently it has been used for its analgesic and anti-inflammatory activity. In this investigation E. angustifolium was collected in Ternopil region of Ukraine. The obtained data demonstrated that E. angustifolium herb extract, rich in polyphenolic compounds such as flavonoids and tannins, display high antioxidant properties. In addition the potential anticancer activity has been investigated in vitro on human hepatocellular carcinoma cells (HepG2). Furthermore the cytotoxic and genotoxic effects of E. angustifolium have been investigated respectively by MTT and Comet assay. Results showed that at low concentration, up to 25 μg/mL, the cytotoxic effect was not observed. Increasing concentration from 50 to 75 μg/mL reduced significantly cell viability and induced an important DNA damage in hepatocellular carcinoma. These promising data were also confirmed with mitochondrial potential test. It is possible to conclude that E. angustifolium has beneficial properties in low concentration, in term of antioxidant activity, and it could be a potential antitumoral natural product if it will be used at high concentration

Bacterial Composition, Genotoxicity, and Cytotoxicity of Fecal Samples from Individuals Consuming Omnivorous or Vegetarian Diets

This study analyzes the composition of viable fecal bacteria and gut toxicology biomarkers of 29 healthy volunteers, who followed omnivorous, lacto-ovo-vegetarian, or vegan diets. In particular, the research was focused on the prevalence of some representative viable bacteria from the four dominant phyla (Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria) commonly present in human feces, in order to evaluate the relationship between microorganisms selected by the habitual dietary patterns and the potential risk due to fecal water (FW) genotoxicity and cytotoxicity, considered as biomarkers for cancer risk and protective food activity. The relative differences of viable bacteria among dietary groups were generally not statistically significant. However, compared to omnivores, lacto-ovo-vegetarians showed low levels of total anaerobes. Otherwise, vegans showed total anaerobes counts similar to those of omnivores, but with lower number of bifidobacteria and the highest levels of bacteria from the Bacteroides–Prevotella genera. FW genotoxicity of lacto-ovo-vegetarians resulted significantly lower either in relation to that of omnivores and vegans. Lacto-ovo-vegetarians also showed the lowest levels of cytotoxicity, while the highest were found for vegans. These results highlighted that lacto-ovo-vegetarian diet was particularly effective in a favorable modulation of microbial activity, thus contributing to a significant reduction of the genotoxic and cytotoxic risk in the gut.

Childhood Leukemia: A Preventable Disease

In contrast to most pediatric cancers, there is a growing body of literature, nationally and internationally, that has implicated the role of several environmental indoor and outdoor hazards in the etiology of childhood leukemia. For example, exposures to solvents, traffic, pesticides, and tobacco smoke have consistently demonstrated positive associations with the risk of developing childhood leukemia. Intake of vitamins and folate supplementation during the preconception period or pregnancy has been demonstrated to have a protective effect. Despite the strength of these findings, the dissemination of this knowledge to clinicians has been limited. Some children may be more vulnerable than others as documented by the high and increasing incidence of childhood leukemia in Hispanics. To protect children's health, it is prudent to establish programs to alter exposure to those factors with well-established associations with leukemia risk rather than to suspend judgment until no uncertainty remains. This is particularly true because other serious health outcomes (both negative and positive) have been associated with the same exposures. We draw from historical examples to put in perspective the arguments of association versus causation, as well as to discuss benefits versus risks of immediate and long-term preventive actions.

Genotoxicity of commercial fungicide Cabrio Plus on human cell

Cabrio Plus, a commercial fungicide, is used in agriculture as the control agent for a broad spectrum of diseases including black dot, early blight, late blight and powdery mildew. This study aimed to evaluate the genotoxicity of commercial formulation of Cabrio Plus which has been inadequately evaluated. The genotoxic potential of Cabrio Plus in isolated human peripheral blood lymphocytes was measured by means of an alkaline version of the comet assay (pH > 13) and in whole blood by use of the in vitro micronucleus test. Cabrio Plus induced a statistically significant increase in DNA damage assessed with the in vitro micronucleus assay and the comet assay. Cabrio Plus also induced cytotoxicity in a dose-dependent manner with the in vitro micronucleus assay. It can be concluded that a commercially available pesticide formulation, Cabrio Plus, has the ability to cause DNA damage and cytotoxicity.

In vitro assessment of the genotoxicity of ethyl paraoxon in newborns and adults

This in vitro experiment measured the genotoxic effects of ethyl paraoxon, the active metabolite of ethyl parathion. To assess genotoxicity, we used the micronuclei (MN) technique by blocking cytokinesis, and the ‘comet’ assay. We cultured peripheral blood samples from healthy adults and umbilical cord blood samples from four clinically healthy newborns to identify the frequency of MN. After 48 hours, we added the following ethyl paraoxon concentrations to the cultures: 0.0, 0.075, 0.100, 0.160, and 0.200 μg/mL. For the comet assay, following Singh's technique, we treated the blood samples for 2 hours with similar doses of the metabolite. The comet assay results, at a concentration of 0.075 μg/mL, showed that ethyl paraoxon causes a greater DNA migration that followed a dose-response pattern, a greater intensity being observed in lymphocytes from newborns. A comparison of the treatment and control groups indicated that only the 0.200 μg/mL concentration produced a slight increase in MN. In conclusion, our study identified primary DNA damage due to ethyl paraoxon, with a major effect on newborn lymphocytes, as well as an effect on the frequency of MN in the study groups at high concentrations only.

PM10 in a background urban site: chemical characteristics and biological effects

PM10 was sampled in a background urban site in Torino, a northern Italian city. PM10 extracts were tested with THP-1 and A-549 cells to evaluate their effects on cell proliferation, LDH activity, TNFα, IL8 and CYP1A1 expression, and genotoxic damage induction (Comet assay). Through Principal Component Analysis (PCA), it was observed that (1) the aqueous extracts induced the inhibition of cell proliferation in the warm season that clustered together to total ions, (2) organic extracts determined a winter cell viability reduction and (3) there was a genotoxic effect associated with PAH and metal concentrations. The analysed low PAH levels were unable to induce significant CYP1A1 expression. The results obtained confirmed that PM composition and seasonality play an important role in particle-induced toxicity. The presence of PM10-induced biological effects at a low polluted site suggested that a reduction of PM10 mass did not seem to be sufficient to reduce its toxicity.

Short term exposure to multi-walled carbon nanotubes induce oxidative stress and DNA damage in Xenopus laevis tadpoles

The potential impact of Multiwalled Carbon NanoTubes (MWCNTs) was investigated on Xenopus laevis tadpoles exposed to 0.1, 1 and 10mg/L. Oxidative stress was measured in entire larvae exposed and DNA damage (Comet assay) was carried out in erythrocytes of circulating blood from 2h to 24h according to standardized recommendations. Results showed significant H2O2 production when larvae were exposed to 1mg/L and 10mg/L of MWCNTs after 4h and 2h of exposure, respectively. Antioxidant enzyme activities showed significant induction of catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) from only 2h of exposure to 10mg/L of MWCNTs. In presence of 1mg/L of MWCNTs, only GR and CAT activities were significantly induced at 4h. Enzyme activities do not follow a simple dose-effect relation, but the time of induction is shortened in relation with the tested concentration. The Comet assay results showed significant DNA damages with a dose dependent response. The profiles of DNA damages show fluctuations, in course of time, which are characteristics of oxidative stress response in relation with the continuous balance between damage and compensation process.

Comparative evaluation in vitro of the herbicide flurochloridone by cytokinesis-block micronucleus cytome and comet assays

The in-vitro effects of flurochloridone and its formulations Twin Pack Gold® (25% a.i.) and Rainbow® (25% a.i.) were evaluated in Chinese Hamster Ovary K1 (CHO-K1) cells. The cytokinesis-block micronucleus cytome (CBMN-cyt) and single-cell gel electrophoresis (SCGE) assays were used. The activities were tested within the range of final concentrations of 0.25-15 μg flurochloridone/mL. The results demonstrated that both the flurochloridone and Rainbow® were not able to induce micronuclei (MN). On the other hand, Twin Pack Gold® only increased the frequency of MN at 5 μg/mL. Furthermore, 10 and 15 μg/mL of both formulations resulted in a cellular cytotoxicity demonstrated by alterations in the nuclear division index and cellular death. SCGE assay appeared to be a more sensitive bioassay for detecting primary DNA strand breaks at lower concentrations of flurochloridone than MN did. A marked increase in the genetic damage index was observed when 5 and 15 μg/mL of both flurochloridone and Rainbow® but only when 15 μg/mL of Twin Pack Gold® were used. This is the first report demonstrating that flurochloridone and its two commercial formulations are able to induce single-strand DNA breaks in vitro on mammalian cells.

Removal of triazine herbicides from aqueous systems by a biofilm reactor continuously or intermittently operated

The impact of pesticide movement via overland flow or tile drainage water on the quality of receiving water bodies has been a serious concern in the last decades; thus, for remediation of water contaminated with herbicides, bioreaction systems designed to retain biomass have been proposed. In this context, the aim of this study was to evaluate the atrazine and terbutryn biodegradation capacity of a microbial consortium, immobilized in a biofilm reactor (PBR), packed with fragments of porous volcanic stone. The microbial consortium, constituted by four predominant bacterial strains, was used to degrade a commercial formulation of atrazine and terbutryn in the biofilm reactor, intermittently or continuously operated at volumetric loading rates ranging from 44 to 306 mg L(-1) d(-1). The complete removal of both herbicides was achieved in both systems; however, higher volumetric removal rates were obtained in the continuous system. It was demonstrated that the adjuvants of the commercial formulation of the herbicide significantly enhanced the removal of atrazine and terbutryn.

Assessment of genotoxic effects of flumorph by the comet assay in mice organs

The present study investigated the genotoxic effects of flumorph in various organs (brain, liver, spleen, kidney and sperm) of mice. The DNA damage, measured as comet tail length (µm), was determined using the alkaline comet assay. The comet assay is a sensitive assay for the detection of genotoxicity caused by flumorph using mice as a model. Statistically significant increases in comet assay for both dose-dependent and duration-dependent DNA damage were observed in all the organs assessed. The organs exhibited the maximum DNA damage in 96 h at 54 mg/kg body weight. Brain showed maximum DNA damage followed by spleen > kidney > liver > sperm. Our data demonstrated that flumorph had induced systemic genotoxicity in mammals as it caused DNA damage in all tested vital organs, especially in brain and spleen.

Effect of triazole pesticide formulation on bovine culture cells

To date, most data about the possible genotoxic effect of triazole pesticides are focused on laboratory animals resulting in limited information on further non-target organisms such as cattle. The objective of the present study was to investigate the effect of triazole (tebuconazole/prothioconazole) fungicide formulation on the induction of chromosomal aberrations (CAs), sister chromatid exchanges (SCEs) and DNA fragmentation in bovine cultured lymphocytes. Our results showed that the fungicide formulation did not induce significant number of CAs in bovine cells after 24 h treatment. Nevertheless, the dose-dependent reduction of mitotic division was observed, with the strongest effect at 30.0 μg mL(-1) in both donors (P < 0.01 and P < 0.001, respectively). Prolonged 48 h exposure caused the increased level of breaks in treated cultures (3.0-15.0 μg mL(-1); P < 0.05) and significant decrease in mitotic index (MI). The tested fungicide failed to produce any statistical changes in the SCE frequency neither after 24 h nor 48 h treatment. However, the significant decline of the proliferation index (PI) was observed after 24 h indicating the fungicide influence on cell cycle kinetics. Prolonged 48 h exposure caused cytotoxicity reflecting in lower PI value relative to control mainly at the highest fungicide concentrations (30.0 μg mL(-1), P < 0.001). Using painting probes for bovine chromosomes 1, 5 and 7 (BTA1, BTA5 and BTA7) only low levels of aneuploidies were detected. Significant increase of polyploidy cells (P < 0.05) was induced by a 3.0 μg mL(-1) dose of the fungicide after 48 h. DNA fragmentation assay didn't reveal the presence of DNA nucleosome ladder in cell cultures at any time (24 h and 48 h) and fungicide concentration.

A protocol for the evaluation of genotoxicity in bile of carp (Cyprinus carpio) exposed to lake water treated with different disinfectants

A sensitive and rapid method to evaluate toxic and genotoxic properties of drinking water supplied from Lake Trasimeno (Umbria, Central Italy) was worked out analysing bile in Cyprinus carpio exposed for 20 d to lake water treated with 3 different disinfectants, sodium hypochlorite (NaClO), chlorine dioxide (ClO(2)) and peracetic acid (PAA). Fish were sacrificed at 0, 10 and 20 d in order to investigate the time course of these endpoints. An aliquot of bile samples was fractionated by adsorption on C(18) silica cartridges and the genotoxic potential of whole bile and of bile fractions was evaluated by the single-cell microgel-electrophoresis (comet) assay on human colonic adenocarcinoma cells (Caco-2). Bile (both whole and fractionated) from specimens exposed to the three disinfectants always showed a genotoxic activity as compared to the control group. The results of this study provide evidence that all three disinfectants cause an increase in bile genotoxicity of chronically exposed fish.

Comparison of Terbutryn Acute Toxicity to Danio rerio and Poecilia reticulata

The aim of the present study was to determine and compare acute toxicity of terbutryn in Danio rerio and Poecilia reticulata, and in two different developmental stages of D. rerio – embryonic and juvenile. Acute toxicity tests were performed according to OECD methodology. The LC50 values were assessed by probit analysis using EKO-TOX 5.2 programme. The 96hLC50 terbutryn mean value of 5 tests was 2.85 ± 0.75 mg·l-1 for the juvenile stage of P. reticulata and 5.71 ± 0.46 mg·l-1 for the juvenile stage of D. rerio. For the embryonic stage of D. rerio the 144hLC50 terbutryn mean value of 6 tests was estimated as 8.04 ± 1.05 mg·l-1. The study proved significantly higher (p < 0.01) sensitivity of the juvenile stage of D. rerio to terbutryn compared to the embryonic stage of D. rerio and significantly higher (p < 0.01) sensitivity of the juvenile stage of P. reticulata to terbutryn compared to the juvenile stage of D. rerio. herbicides. This study documented differences in sensitivity of several fish species and different developmental stages of fish to one of triazine.

Leucocytes DNA damage in mice exposed to JS-118 by the comet assay

JS-118 is an extensively used insecticide in China. The present study investigated the genotoxic effect of JS-118 on whole blood at 24, 48, 72 and 96 h by using alkaline comet assay. Male Kunming mice were given 6.25, 12.5, 25, 50 and 100 mg/kg BW of JS-118 intraperitoneally. A statistically significant increase in all comet parameters indicating DNA damage was observed at 24 h post-treatment (p < 0.05). A clear concentration-dependent increase of DNA damage was revealed as evident by the OTM (arbitrary units), tail length (µm) and tail DNA (%). From 48 h post-treatment, a gradual decrease in mean comet parameters was noted. By 96 h of post-treatment, the mean comet tail length reached control levels indicating repair of damaged DNA. This study on mice showed different DNA damage depending on the concentration of JS-118 and the period of treatment. The present study provided further information of the potential risk of the genetic damage caused by JS-118.

Effects of sub-chronic exposure to terbutryn in common carp (Cyprinus carpio L.)

The sub-chronic effects of terbutryn at concentrations 0.02 (reported concentration in Czech rivers), 4, 20, and 40 microg L(-1) were assessed in one-year-old common carp (Cyprinus carpio L.) exposed for 28 days and compared to a non-treated control group. Its influence on biometric parameters, hematology, blood biochemistry, and histology was investigated. Exposure to terbutryn at 0.02 microg L(-1) showed no observable effect, whereas exposure to 4, 20, and 40 microg L(-1) showed significantly higher erythrocyte counts, ammonia levels, aspartate aminotransferase, lactate dehydrogenase, creatine kinase, and lactate, but significantly lower mean corpuscular volume, mean corpuscular hemoglobin, and creatine. Cell shape changes and lipid inclusions were found in hepatocytes, and there was destruction of caudal kidney tubules when compared to control fish.

DNA damage in A549 cells exposed to different extracts of PM(2.5) from industrial, urban and highway sites

The aim of this research is to investigate the role played by the chemical fraction of PM(2.5) in the DNA damage induction in human lung cells (A549): in particular the effects of samples collected in urban, industrial and highway sites were compared. Organic and water-soluble extracts of PM(2.5) were analysed to quantify PAHs (by GC-MS technique) and metals (by ICP-MS technique) and tested on A549 cells to evaluate, by the Comet assay (without and with Fpg enzyme), genotoxic and oxidative damage. The chemical analysis showed a variability of PAH composition in PM organic extracts of the three different sites and pointed out the presence of 14 metals (being Fe, Cu, Zn, Sb and Ba the most abundant) in all the PM water extracts. Regarding the biological effect, all the PM(2.5) organic extracts caused a significant dose-dependent increase of the A549 DNA damage. The genotoxic effect was related to the PM(2.5) PAH content and the highest effect was observed for the highway site sample. The DNA oxidative damages were observed for the PM(2.5) water extracts of the samples collected in industrial and highway sites. The extent of the oxidative damage seems to be related to the kind and concentration of the metals present. The results of this study emphasize the importance of PM chemical composition on the biological effects and highlight the need, when evaluating the effects on health and exposure management, to always consider, beside size and concentration of PM, also their qualitative composition.

Application of semipermeable membrane device (SPMD) to assess air genotoxicity in an occupational environment

Semipermeable membrane device (SPMD) is a passive sampler that sequesters lipophilic contaminants, mimicking the bioconcentration in the fatty tissue of organisms. This study was designed to assess the use of SPMD and biological tests (Comet assay and Ames test) for air monitoring. For this purpose an occupational environment with expected polycyclic aromatic hydrocarbons (PAHs) contamination (coke plant) was selected for a case study. The SPMDs were deployed in five occupational contaminated sites and in a control site. The SPMD dialysates were chemically analysed and examined for in vitro DNA-damaging activity in human cells (Jurkat) by Comet assay and for mutagenicity with the Ames test (TA98 strain, w/o S9). Total suspended particulates were also collected and analysed (GC-MS). No biological effect of SPMD extract was revealed in the control site. On the other hand, air samples collected with SPMDs within the coke plant showed variable degrees of genotoxic and mutagenic activity. The highest effects were associated with the highest PAH level recovered in the SPMDs extracts and in particulate samples. Results obtained support the sensitivity of biological tests associated to SPMD sampling for evaluating the health risk of potentially contaminated work environments highlighting the usefulness of SPMDs for environmental air quality monitoring.

Cadmium accumulation and biochemical responses in Sparus aurata following sub-lethal Cd exposure

Cadmium (Cd), a heavy metal with limited biological function, is widely distributed in the aquatic environment as a result of natural and anthropogenic activities. The effect of 4 and 11 days exposure of gilthead sea bream Sparus aurata to sub-lethal concentrations of Cd was evaluated as levels of Cd content and Cd-metallothionein (MT) presence in different organs. The possible genotoxic effect was also evaluated in erythrocytes by using the "comet assay", a promising tool for estimating DNA damage at the single-cell level. The results obtained show that in the controls, Cd content was significantly higher in gills compared to in liver, but the treatment of fish with 0.1mg/l Cd induced a stronger accumulation of metal in liver depending on the length of the exposure period. Cd traces were found in plasma, muscle and kidney. Cd forms complexes in the cytosol with MT only in the liver but Cd-MT content significantly increased after 11 days of exposure to the metal, while after 4 days of treatment the protein level was similar to the control. The "comet assay" performed on S. aurata eryhtrocytes isolated from fish treated for 4 and 11 days with 0.1mg/l Cd, showed that there was no DNA damage at both exposure periods.

Modulatory activity of a Lactobacillus casei strain on 1,2-dimethylhydrazine-induced genotoxicity in rats

The present study was designed to investigate the putative antigenotoxic effects of supplementing the diet of rats treated with the colon carcinogen 1,2-dimethylhydrazine hydrochloride (DMH) with a Lactobacillus casei strain using an in vivo approach. The antigenotoxic response was evaluated in colon and liver cells using the alkaline comet assay. Since the balance between the bioactivation and detoxification metabolic pathways is crucial for the formation of toxic and genotoxic metabolites, alterations in the level of some xenobiotic metabolizing enzymes (XME) were studied in liver preparations. In the challenge group (L. casei + DMH), lactobacilli-supplemented diet, there was a decrease in the extent of DMH-induced DNA damage, especially in colon cells. Compared with control rats, there was less basal DNA damage in colon cells of rats fed on a lactobacilli-supplemented diet. These findings are the first to give clear evidence of DNA-protective effects of lactobacilli against basal DNA damage. Moreover, the chemopreventive effects were accompanied by changes in the activities of several XME. The observed decrease in the concentration of nonenzymatic antioxidants (i.e. GSH) and the reduced activity of enzymatic antioxidants (i.e., GST, GPx, and SOD) in liver could reflect an overall reduction in the level of oxidative stress in rats on a diet supplemented with the L. casei suspension compared with control rats (basal state). Thus, the concentrations of GSH and the activities of GST, GPx, and SOD could be downregulated by supplementing the diet with L. casei as a response to an improved antioxidant status.

Evaluation of genotoxic and antigenotoxic effects of hydroalcoholic extracts of Zuccagnia punctata Cav

Zuccagnia punctata Cav. (Fabaceae), a widely used plant species in Argentine folk medicine, has been shown to have a broad spectrum of antibacterial, antifungal, antioxidant and cytoprotective activities. In this study, the hydroalcoholic extract of Zuccagnia punctata and 2',4'-dihydroxychalcone isolated from it were investigated for genotoxicity/antigenotoxicity in the in vitro comet assay test on human hepatoma HepG2 cells. No acute toxicity of the extract could be determined. HepG2 cells were treated with three different concentrations (2.5, 5.0 and 10.0 microg/mL) or 2',4'-dihydroxychalcone (0.01, 0.10 and 1.00 microg/mL). To explore the potential mechanisms of action, two approaches were followed: co-treatment with 4-nitroquinoline-N-oxyde (4-NQO), a direct genotoxic compound, and a pre-treatment protocol with benzo[a]pyrene (B[a]P), an indirect genotoxic compound. The natural products neither affected cell viability nor induced DNA damage in the concentration range tested. Zuccagnia punctata tinctures were able to diminish the DNA damage induced in HepG2 cells by 4-NQO and B[a]P in 31% and 10%, respectively at 10 microg/mL. Pre-treatment of HepG2 cells with 2',4'-dihydroxychalcone was highly effective in decreasing B[a]P-induced DNA damage at a statistically significant level, with an almost clear dose-response relationship. The inhibition values were 28.2-43.9% for the tested concentrations of 0.01-1 microg/mL, respectively. The results clearly indicate that the phytoextract from Zuccagnia punctata, under the experimental conditions tested, is not genotoxic and that 2',4'-dihydroxychalcone contributes to a high degree to the antigenotoxic effects of Zuccagnia punctata tincture.

Population growth study of the rotifer Brachionus sp. fed with triazine-exposed microalgae

Few data exist on potential toxic effects that pollutants may have on zooplankton fed microalgae exposed to pesticides. For that reason, microalgal cultures were exposed to different concentrations of the triazine herbicide terbutryn, and used as exclusive food source to Brachionus sp. females, with the aim to evaluate potential deleterious effects upon population growth, survival, reproduction and feeding of the rotifer. Chlorella vulgaris cells were able to accumulate terbutryn, removing more than 90% of the total amount of herbicide in all the exposed cultures. Growth curves of Brachionus sp. showed that population density decreased as terbutryn concentration increased in the microalgal cells. In fact, this species of rotifer did not survive beyond four days when fed with microalgae exposed to 500 nM terbutryn. Percentage of reproductive females in rotifer populations fed with terbutryn-exposed microalgae decreased significantly as herbicide concentration increased. In control cultures, reproductive females laid a maximum of three eggs per individual; whereas in 100 nM cultures, reproductive females laid only one egg per individual throughout the treatment period. Terbutryn accumulated in C. vulgaris provoked a decrease in the feeding rate of Brachionus sp. cultures fed with these microalgae with respect to control cultures. After this treatment period, all the rotifer populations, except those fed with 500 nM terbutryn-exposed microalgae, showed recovery patterns when they were returned to fresh medium containing herbicide-free microalga. Taking into account the results obtained, uptake of pesticides by phytoplankton can directly affect higher trophic levels.

Metabolic activation of herbicide products by Vicia faba detected in human peripheral lymphocytes using alkaline single cell gel electrophoresis

Ametryn and metribuzin S-triazines derivatives and EPTC thiocarbamate are herbicides used extensively in Mexican agriculture, for example in crops such as corn, sugar cane, tomato, wheat, and beans. The present study evaluated the DNA damage and cytotoxic effects of three herbicides after metabolism by Vicia faba roots in human peripheral lymphocytes using akaline single cell gel electrophoresis. Three parameters were scored as indicators of DNA damage: tail length, percentage of cells with DNA damage (with comet), and level DNA damage. The lymphocytes were treated for 2 h with 0.5-5.0 microg/ml ametryn or metribuzin and 1.5-10 microg/ml EPTC. Lymphocytes also were coincubated for 2 h with 20 microl V. faba roots extracts that had been treated for 4 h with 50-500 mg/l of the two triazines or with the thiocarbamate herbicide or with ethanol (3600 mg/l), as positive control. The lymphocytes treated with three pesticides without in vivo metabolic activation by V. faba root did not show significant differences in the mean values between genotoxic parameters compared with negative control. But when human cells were exposed to three herbicides after they had been metabolized the frequency of cell comet, tail length and level DNA damage all increased. At highest concentrations of the three herbicides produced severe DNA damage compared with S10 fraction and negative control. The linear regression analysis of the tail length values of three herbicides indicated that there was genotoxic effect concentration-response relationship with ametryn and ametribuzin but no EPTC. The ethanol induced major increase DNA damage compared with S10 fraction and the three pesticides. There were not effects in cell viability with treatment EPTC and metribuzin whether or not it had been metabolized. High concentrations of ametryn alone and after it had been metabolized decreased cell viability compared with the negative control. The results demonstrated that the three herbicides needed to be activated by the V. faba root metabolism to produce DNA damage in human peripheral lymphocyte. The alkaline comet technique is a rapid and sensitive assay, to quickly evaluate DNA damage the metabolic activation of herbicide products by V. faba root in human cells in vitro.

Non-omnia moriantur-toxicity of mancozeb on dead wood microarthropod fauna

The effect of Dithane M-45 (dithiocarbamate fungicide; active substance: mancozeb) was studied on microarthropod fauna inhabiting dead wood. Although the exposure was almost never 100% lethal for the majority of observed taxa, almost all (Mesostigmata, Oribatida, some Uropodina, Actinedida, Collembola and Diplopoda) showed very high correlation between concentration of the fungicide and mortality (r > 0.86). Only Stigmaeidae showed low correlation (r = 0.293). For the majority of taxa LC(50 )values were close to the concentrations used during agrochemical activities in woods. Only Trachytes aegrota showed full susceptibility to the fungicide within the range of recommended field concentrations used in forestry (characterised by the low LC(95 )value). Tolerance of mesostigmatid and oribatid mites was found to differ between juveniles and adults, but not consistently. Related Uropodina species varied in susceptibility to the fungicide.

Effects of co-exposure to extremely low frequency (50 Hz) magnetic fields and xenobiotics determined in vitro by the alkaline comet assay

In the present study, we used human peripheral blood leukocytes from 4 different donors, to investigate in vitro the possible genotoxic and/or co-genotoxic activity of extremely low frequency magnetic fields (ELF-MF) at 3 mT intensity. Two model mutagens were used to study the possible interaction between ELF-MF and xenobiotics: N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 4-nitroquinoline N-oxide (4NQO). Primary DNA damage was evaluated by the alkaline single-cell microgel-electrophoresis ("comet") assay. Control cells (leukocytes not exposed to ELF-MF, nor treated with genotoxins) from the different blood donors showed a comparable level of basal DNA damage, whereas the contribution of individual susceptibility toward ELF-MF and the tested genotoxic compounds led to differences in the extent of DNA damage observed following exposure to the genotoxins, both in the presence and in the absence of an applied ELF-MF. A 3 mT ELF-MF alone was unable to cause direct primary DNA damage. In leukocytes exposed to ELF-MF and genotoxins, the extent of MNNG-induced DNA damage increased with exposure duration compared to sham-exposed cells. The opposite was observed in cells treated with 4NQO. In this case the extent of 4NQO-induced DNA damage was somewhat reduced in leukocytes exposed to ELF-MF compared to sham-exposed cells. Moreover, in cells exposed to ELF-MF an increased concentration of GSH was always observed, compared to sham-exposed cells. Since following GSH conjugation the genotoxic pattern of MNNG and 4NQO is quite different, an influence of ELF-MF on the activity of the enzyme involved in the synthesis of GSH leading to different activation/deactivation of the model mutagens used was hypothesized to explain the different trends observed in MNNG and 4NQO genotoxic activity in the presence of an applied ELF-MF. The possibility that ELF-MF might interfere with the genotoxic activity of xenobiotics has important implications, since human populations are likely to be exposed to a variety of genotoxic agents concomitantly with exposure to this type of physical agent.

Screening of potential lactobacilli antigenotoxicity by microbial and mammalian cell-based tests

Antigenotoxicity is considered an important property for probiotic lactobacilli. The ability of non probiotic lactobacilli from dairy products and starters to inhibit two reference genotoxins: 4-nitroquinoline-1-oxide and N-methyl-N'-nitro-N-nitrosoguanidine was evaluated. The study was carried out using short-term assays with different targets, such as procaryotic cells (SOS-Chromotest for genotoxicity in Escherichia coli and Ames test for mutagenicity in Salmonella typhimurium) and eucaryotic cells (Comet assay for genotoxicity in Caco-2 enterocytes). A high proportion of strains inhibiting 4-nitroquinoline-1-oxide activity was found in Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus plantarum. Inhibition of N-methyl-N'-nitro-N-nitrosoguanidine activity occurred in only one L. acidophilus strain. All the strains with antigenotoxic properties also demonstrated antimutagenic activity and produced modifications in genotoxin spectroscopic profiles. Strain viability during and after genotoxin exposure was confirmed. Concordance of the results obtained with microbial and mammalian cell-based tests is underlined.

Effects of co-exposure to extremely low frequency (ELF) magnetic fields and benzene or benzene metabolites determined in vitro by the alkaline comet assay

In the present study, we investigated in vitro the possible genotoxic and/or co-genotoxic activity of 50 Hz (power frequency) magnetic fields (MF) by using the alkaline single-cell microgel-electrophoresis (comet) assay. Sets of experiments were performed to evaluate the possible interaction between 50 Hz MF and the known leukemogen benzene. Three benzene hydroxylated metabolites were also evaluated: 1,2-benzenediol (1,2-BD, catechol), 1,4-benzenediol (1,4-BD, hydroquinone), and 1,2,4-benzenetriol (1,2,4-BT). MF (1 mT) were generated by a system consisting of a pair of parallel coils in a Helmholtz configuration. To evaluate the genotoxic potential of 50 Hz MF, Jurkat cell cultures were exposed to 1 mT MF or sham-exposed for 1h. To evaluate the co-genotoxic activity of MF, the xenobiotics (benzene, catechol, hydroquinone, and 1,2,4-benzenetriol) were added to Jurkat cells subcultures at the beginning of the exposure time. In cell cultures co-exposed to 1 mT (50 Hz) MF, benzene and catechol did not show any genotoxic activity. However, co-exposure of cell cultures to 1 mT MF and hydroquinone led to the appearance of a clear genotoxic effect. Moreover, co-exposure of cell cultures to 1 mT MF and 1,2,4-benzenetriol led to a marked increase in the genotoxicity of the ultimate metabolite of benzene. The possibility that 50 Hz (power frequency) MF might interfere with the genotoxic activity of xenobiotics has important implications, since human populations are likely to be exposed to a variety of genotoxic agents concomitantly with exposure to this type of physical agent.

Promutagen activation of triazine herbicides metribuzin and ametryn through Vicia faba metabolism inducing sister chromatid exchanges in human lymphocytes in vitro and in V. faba root tip meristems

The aim of our study was the induction of sister chromatid exchanges (SCE) in human lymphocytes in vitro and in root tip meristems of Vicia faba to evaluate the genotoxic effects of metribuzin and ametryn. Direct treatments of these herbicides on human lymphocytes in vitro applied 24 h after the beginning of culture did not induce SCE; however, they showed a cytotoxic effect in the cultures expressed as cellular death. On the contrary, when extracts of V. faba roots, treated for 4 h with metribuzin and ametryn (in vivo activation), were added to the lymphocyte cultures, SCEs were significantly induced with an asymptotic response. Negative responses appeared with the in vitro assays, in which metribuzin and ametryn were added directly to the 48 h lymphocyte cultures for 4 h. Nevertheless, in treatments in which the S10 metabolic mix was added, the SCE frequencies were significantly different to the control, although a concentration-response relationship was only observed with metribuzin. The results showed that both herbicides needed the V. faba metabolism to produce SCE in human lymphocyte cultures. Metribuzin and ametryn applied to V. faba root tip meristems for 4 h increased SCE frequency significantly, and a concentration-response relationship was observed with both herbicides.

Effects of pesticides on human peripheral lymphocytes in vitro: induction of DNA damage

Because of the widespread use of pesticides for domestic and industrial applications the evaluation of their genotoxic effects is of major concern to public health. Although various experimental data have provided evidence that pesticides can possess genotoxic properties in animals and in in vitro test systems after acute and chronic exposure, the information on the genotoxic effects of some of pesticides is limited and inconsistent. In the present study, the genotoxic potential of commonly used pesticides (i.e., dimethoate and methyl parathion from the organophosphate class, propoxur and pirimicarb from carbamates, and cypermethrin and permethrin from pyrethroids) have been evaluated. The genotoxic effects of these substances were examined using the single cell gel electrophoresis (comet) assay in freshly isolated human peripheral lymphocytes. The cells were incubated with 10, 50, 100 and 200 microg/ml concentrations of the test substances for 0.5 h at 37 degrees C and DNA damage was compared with that obtained in lymphocytes from the same donor not treated with substances. Hydrogen peroxide, 100 microM, was used as a positive control. Within the concentration ranges studied, no significant cytotoxic effects were observed. Dimethoate and methyl parathion at 100 and 200 microg/ml; propoxur at 50, 100 and 200 microg/ml, and pirimicarb, cypermethrin and permethrin at 200 microg/ml significantly increased DNA damage in human lymphocytes.

Assessment of the ability of Imazaquin herbicide to induce chromosomal aberrations in vitro in cultured Chinese hamster ovary cells and micronuclei in vivo in mice

The agricultural chemicals marketed to increase food production may not only combat pests and weeds but also present toxic properties and cause genetic damage to the fauna and flora. The Imazaquin herbicide (Scepter 70 DG-Cyanamid) has been widely used in soybean fields in Paraná (Brazil), but information on its genotoxicity is scarce. Thus, in vivo and in vitro studies were carried out to assess the possible clastogenic effect of this herbicide on eukaryote cells. In the in vitro studies, the Chinese hamster ovarian cell lines CHO-K1 (wild) and CHO xrs-5 (mutant) were treated at the three phases of the cell cycle (G1, S and G2) for chromosome aberration (CA) analysis. The in vivo assessment was carried out by the micronucleus test (MN) on Swiss mice (Mus musculus) bone marrow cells. The herbicide did not induce a significant increase in the CA frequency in any of the treatments. No statistically significant differences were observed in the MN frequencies among the groups treated with the herbicide and the negative control. From the test system used in this study, we can conclude that the Imazaquin herbicide did not act as a clastogenic agent either in vitro or in vivo.

Evaluation of EMS-induced DNA damage in the single cell gel electrophoresis (Comet) assay and with flow cytometric analysis of micronuclei

Toxic agents in the environment pose serious threats to ecosystems and to the public health. The single cell gel electrophoresis (SCGE) or Comet assay quantitatively measures genomic damage as DNA strand breaks. The micronucleus (MCN) test is an established assay that measures chromosomal damage. Micronuclei are formed from chromosome fragments or from whole chromosomes that have not undergone mitosis properly. This test is usually conducted microscopically. However, micronuclei can also be analyzed using flow cytometry. Chinese hamster ovary (CHO) cells were exposed to ethylmethanesulfonate (EMS), for 4 h in a total volume of 25 microl. These cells were immediately analyzed for genomic DNA damage by SCGE. In concurrent parallel experiments, CHO cells were treated with EMS in 6-well plates for 4 h, the cells were washed and fresh medium was added. The cells were allowed to grow for 45 to 48 h to express micronuclei. The data demonstrated that both DNA strand breaks and micronuclei were induced in a significant and concentration-dependent manner. There was a significant and high correlation (r = 0.91; P < or = 0.001) between the acute induction of DNA strand breaks and the subsequent generation of micronuclei. These data indicate that using molecular and computer technologies, the genotoxic impact of toxic and environmental agents can be rapidly and comprehensively evaluated in mammalian cell systems.