In vitro cytotoxic and cell transforming activities exerted by the pesticides cyanazine, dithianon, diflubenzuron, procymidone, and vinclozolin on BALB/c 3T3 cells

Evaluation of the effects of the recommended oral dose of diflubenzuron on bovine sperm and oocyte quality using CASA and OPU-IVEP

Introduction

The aim of this study was to evaluate potential effects of diflubenzuron on the production and quality of gametes, and on in vitro embryo production (IVEP) outcomes, in cattle.

Methods

Two experiments were performed, the first to evaluate effects on semen, and the second on cumulus-oocyte complexes (COC) and on IVEP. Nelore (Bos taurus indicus) bulls (n = 14) or heifers (n = 16) were allocated into control (CG) or treatment (DIF) groups. All groups received a mineral mix supplement added (DIF) or not (CG) with diflubenzuron (30 mg/head/day), during 8 weeks. Animals were weighed and blood samples were collected throughout the experimental period. Every other week, bulls were subjected to semen collection and heifers to transvaginal ultrasound-guided follicle aspiration sessions. Semen underwent physical and morphological evaluation, and samples were stored for further computer-assisted sperm analysis. The COC recovered were evaluated according to morphology and those classified as viable were sent to an IVEP laboratory.

Results

Diflubenzuron had no effect (P > 0.05) on average body weight or in any blood hematological or biochemical endpoints, regardless of gender. In experiment 1, there was no difference (P > 0.05) between DIF and CG groups for sperm concentration, morphology, or kinetics. In experiment 2, there was also no effect of diflubenzuron on the number of total, viable, or grade I oocytes, as well as on cleavage or blastocyst rates (P > 0.05).

Discussion

In summary, the oral administration of diflubenzuron, within the recommended dose, has no short-term negative effects on sperm production and quality or on oocyte yield and developmental potential in vitro, in cattle.

Enhanced photodegradation of applied dithianon fungicides on plant leaves by dissolved substances in atmosphere under simulated sunlight

Photolysis of pesticides has been widely investigated for evaluating their environmental behavior and agricultural effectiveness after crop spraying. However, little information about the effects of the water-soluble substances in atmosphere on photodegradation of pesticides is available. In current study, we found that photolysis of applied dithianon fungicides on real plant leaves was much faster than that in sealed stock aqueous suspensions under simulated sunlight. To simulate the natural conditions, for the first time, photodegradation of dithianon in air-saturated solutions containing typical dissolved atmospheric substances (DAS) including CO₂ (HCO₃^-/CO₃^2-), NO₂ (NO₃^-), Fe³⁺ (Fe³⁺-complexes), and humic-like substances (HULIS) exposed to simulated solar irradiations were carried out in lab-scale. Fulvic acid (FA) was used as a surrogate for atmospheric HULIS in this study. The dithianon photodegradation was significantly enhanced in the presence of DAS and the photo-generated reactive species such as ·OH, ¹O₂, CO₃·- and ³FA∗ play important roles according to the results of reactive species quenching, electron spin resonance spectroscopy, and laser flash photolysis experiments. Moreover, the photodegraded intermediates and final products of dithianon on plant leaves have been identified by HPLC-MS analysis, and its possible photodegradation pathways were proposed. This work indicated that, except for direct photolysis, indirect photosensitive degradation induced by the dissolved photo-active substances in atmosphere should be considered for evaluating the degradation of the applied pesticides on crops.

The implication of ROS production on triflumuron-induced oxidative stress and genotoxicity in human colon carcinoma (HCT-116) cells

The aim of this study is to evaluate the cytotoxic and the genotoxic effects of triflumuron (TFM) on human colon carcinoma cells (HCT-116). Indeed, TFM is used to protect vegetables, fruits, and domestic animals against a large spectrum of parasites causing animal and human disorders. However, studies revealing its toxicity and its mode of action in mammalian systems remain very limited. We monitored our work with the cytotoxicity assay starting with the cell viability test, the ROS generation, the malondialdehyde (MDA) production, the DNA fragmentation, and the measurement of some antioxidant enzymes activities such as catalase, superoxide dismutase, and the glutathione S-transferase. Also, we measured the mitochondrial transmembrane potential. We showed that TFM induced a dose-dependent cell death. This decrease in cell viability was accompanied by a significant reduction in the mitochondrial membrane potential. We also have shown that TFM induced oxidative stress as revealed by the generation of reactive oxygen species, the increase of the MDA levels, and the activation of the antioxidant enzymes. Moreover, our results indicated that TFM induced DNA damage in HCT-116 cells as monitored by the comet assay. We demonstrate, for the first time, the cytotoxic and the genotoxic potentials of TFM on human cultured cells.

Triflumuron induces cytotoxic effects on hepatic and renal human cell lines

Insect growth regulator insecticides are a new class of pesticides, commonly used around the world to control insect damages. Among those compounds, we focused our interest on triflumuron (TFM), which is less toxic than other conventional insecticides. However, not much is known about its toxic effects on mammalian systems. Therefore, our study aimed toward evaluating the cytotoxic and genotoxic effects of TFM using two different cell lines, the human renal embryonic cells (HEK 293) and hepatocytes (Hep G2). We showed, according to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, that TFM reduced significantly the cell viability and increased the reactive oxygen species generation, malondialdehyde levels, and mitochondrial membrane potential in both cell lines. The antioxidant system was disturbed as assessed by the increased activities in both catalase and superoxide dismutase. We demonstrated also, that TFM is an inductor of DNA damages quantified by the comet assay. Moreover, we showed an overexpression of proapoptotic Bax and a decrease in antiapoptotic Bcl-2 expression. As a conclusion, we demonstrate that the liver presents the major target organ to TFM, in which the cytotoxicity and the genotoxic effects were significantly higher in hepatic cells than in renal cells and by consequence its uses must be controlled.

Necrotic cell death induced by dithianon on Saccharomyces cerevisiae

Dithianon is a broad-spectrum anthraquinone fungicide used to control several diseases of grapes, apples, and other fruits and vegetables. Its mode of action is described as multi-site and associated to thiol-reactivity. As other fungicides can affect non-phytopathogenic organisms as yeasts and bacteria, with impact on microbial population, diversity, and fermentation processes. In this context, we study the effect of dithianon on the model organism and fermentative yeast Saccharomyces cerevisiae in order to elucidate the mechanisms involved in yeast cell death., and explain its interference on wine fermentation kinetics. Thus for, we analyzed cellular protein and non-protein thiols, membrane and cell wall integrity, reactive oxygen species accumulation, mitochondrial membrane potential, and phosphatidylserine externalization. The results showed that when exponentially aerobic growing cells of S. cerevisiae are submitted to acute dithianon treatment they loss cell wall and membrane integrity, dying by necrosis, and this behavior is associated to a depletion of reduced proteic and non-proteic thiol groups. We also detected an important increase of cellular reactive oxygen species (ROS) associated to mitochondrial membrane potential modifications on dithianon treated cells. ROS accumulation was not associated to apoptotic cell death, but can be responsible for intracellular damages. Moreover, necrotic cell death induced by dithianon explains its effect on the kinetics of wine fermentations.

Differentiating true androgen receptor inhibition from cytotoxicity-mediated reduction of reporter-gene transactivation in-vitro

In vitro effect-based reporter assays are applied as biodetection tools designed to address nuclear receptor mediated-modulation. While such assays detect receptor modulating potential, cell viability needs to be addressed, preferably in the same well. Some assays circumvent this by co-transfecting a second constitutively-expressed marker gene or by multiplexing a cytotoxicity assay. Some assays, such as the CALUX®, lack this feature. The cytotoxic effects of unknown substances can confound in vitro assays, making the interpretation of results difficult and uncertain, particularly when assessing antagonistic activity. It's necessary to determine whether the cause of the reporter signal decrease is an antagonistic effect or a non-specific cytotoxic effect. To remedy this, we assessed the suitability of multiplexing a cell viability assay within the CALUX® transcriptional activation test for anti-androgenicity. Tests of both well-characterized anti-androgens and cytotoxic compounds demonstrated the suitability of this approach for discerning between the molecular mechanisms of action without altering the nuclear receptor assay; though some compounds were both cytotoxic and anti-androgenic. The optimized multiplexed assay was then applied to an uncharacterized set of polycyclic aromatic compounds. These results better characterized the mode of action and the classification of effects. Overall, the multiplexed protocol added value to CALUX test performance.

Perturbation of murine liver cyp-superfamily of isoforms by different combinations of pesticide mixtures

It was previously found that fenarimol, vinclozolin or acephate, three of the most used pesticides worldwide, provoked a marked perturbation of murine cytochrome P450 (CYP)-linked monooxygenases. Here, to more closely mimic human exposure, it was investigated whether different pesticide combinations administered i.p. in male Swiss Albino CD1 mice in single or repeated fashion (daily, for three consecutive days), affect CYP-dependent oxidations. The four simulated mixtures showed a complex pattern of CYP induction and suppression, especially after repeated injection. For example, while fenarimol alone was the most inducing agent--reaching a 79-fold increase over control in testosterone 2alpha-hydroxylase--followed by vinclozolin and acephate, coadministration with the former markedly reduced induction. Coadministration with vinclozolin, determined various positive and negative modulations. An increase of CYP2B1/2 and CYP3A1/2-associated oxidases and a decrease of ethoxycoumarin metabolism was observed in the acephate and vinclozolin mixture. An equivalent or reduced CYP expression, if compared to double combinations, was seen using the complete mixture. Taken as a whole, the unpredictability of the recorded effects with simple mixtures, shrinks the misleading extrapolation performed on a single pesticide. If reproduced in human, such changes, altering either endogenous metabolism or biotransformation of ubiquitous toxins, might have public health implications.

Neoplastic transformation of BALB/3T3 cells and cell cycle of HL-60 cells are inhibited by mango (Mangifera indica L.) juice and mango juice extracts

The mango, Mangifera indica L., is a fruit with high levels of phytochemicals, suggesting that it might have chemopreventative properties. In this study, whole mango juice and juice extracts were screened for antioxidant and anticancer activity. Antioxidant activity of the mango juice and juice extracts was measured by 3 standard in vitro methods. The results of the 3 methods were in general agreement, although different radicals were measured in each. Anticancer activity was measured by examining the effect on cell cycle kinetics and the ability to inhibit chemically induced neoplastic transformation of mammalian cell lines. Incubation of HL-60 cells with whole mango juice and mango juice fractions resulted in an inhibition of the cell cycle in the G(0)/G(1) phase. A fraction of the eluted mango juice with low peroxyl radical scavenging ability was most effective in arresting cells in the G(0)/G(1) phase. Whole mango juice was effective in reducing the number of transformed foci in the neoplastic transformation assay in a dose-dependent manner. These techniques provide valuable screening tools for health benefits derived from mango phytochemicals.

Vinclozolin, a widely used fungizide, enhanced BaP-induced micronucleus formation in human derived hepatoma cells by increasing CYP1A1 expression

Vinclozolin, a widely used fungicide, can be identified as a residue in numerous vegetable and fruit samples. To get insight in its genetic toxicity, we investigated the genotoxic effect of vinclozolin in the human derived hepatoma cell line HepG2 using the micronucleus (MN) assay. Additionally, to evaluate the co- or anti-mutagenic potency of vinclozolin, we treated HepG2 cells with different concentrations of vinclozolin for 24 h. Subsequently, the cells were exposed to benzo[a]pyrene (BaP) for 1h. Exposure of HepG2 cells to 50-400 microM vinclozolin alone did not cause any induction of micronuclei. However, a pronounced co-mutagenic effect was observed. MN frequencies caused by BaP increased by 30.6%, 52.8% and 65.3% after pretreatment of the cell cultures with 50, 100 and 200 microM vinclozolin, respectively. The highest concentration (400 microM) of vinclozolin tested caused cytotoxicity. Therefore, micronuclei were not considered for that concentration. To clarify the mechanism of cogenotoxicity, we assayed cytochrome P450 1A1 (CYP1A1), which plays a pivotal role in activation of BaP. Cells exposed to vinclozolin led to significant increase of CYP1A1 expression in Western blot. The result suggested that induction of CYP1A1 by vinclozolin account for its enhancing effect on genotoxicity caused by BaP.

CYP superfamily perturbation by diflubenzuron or acephate in different tissues of CD1 mice

This work aimed to investigate whether the insecticide acephate (125 or 250 mg/kg b.w.) or diflubenzuron (752 or 1075 mg/kg b.w.), two of the most widely used pesticides worldwide, impairs CYP-linked murine metabolism in liver, kidney and lung microsomes after repeated (daily, for three consecutive days) i.p. administration. The regio- and stereo-selective hydroxylation of testosterone was used as multibiomarker of different CYP isoforms. Both gender and tissue specific effects were observed. Lung was the most responsive tissue to induction by lower diflubenzuron dose, as exemplified by the marked increase of testosterone 7alpha-hydroxylation (CYP2A) (up to 13-fold) in males. Higher dose produced a generalized inactivation. At the lower dose acephate induced 6beta- (CYP3A1/2, liver) as well as 2beta- (CYP2B1/2, kidney) hydroxylase activities ( approximately 5 and approximately 4-fold increase, respectively) in males. In females, a marked suppression of the various hydroxylations was observed. At 250 mg/kg of acephate, animals did not survive. Induction of the most affected isoforms was sustained by immunoblotting analysis. Corresponding human CYP modulations might disrupt normal physiological functions related to these enzymes. Furthermore, the co-mutagenic and promoting potential of these pesticides, phenomena linked to CYP upregulation (e.g. increased bioactivation of ubiquitous pollutants and generation of oxygen free radicals) are of concern for a more complete definition of their overall toxicological potential.

Inhibition of Neoplastic Transformation of Benzo[α]pyrene-Treated BALB/c 3T3 Murine Cells by a Phytochemical Extract of Passionfruit Juice

The phytochemical composition of passionfruit juice (PFJ) was hypothesized to have valuable anti-cancer activity, and this was tested in a BALB/c 3T3 neoplastic transformation model. A higher concentration of PFJ compared with a lower concentration was effective in reducing the number, size, and invasiveness of transformed foci. When incubated with another mammalian cell line, the MOLT-4, PFJ was unable to alter the cell cycle kinetics while at the same time was successful in inducing the activity of caspase-3, an enzyme that commits the cell to apoptosis. This suggests that phytochemicals found in PFJ were able to produce the changes in transformed foci due to apoptotic mechanisms rather than by a reduction in cell proliferation. These beneficial results were achieved at levels that could theoretically be attained in the plasma after consumption of the juice.

Induction and suppression of cytochrome P450 isoenzymes and generation of oxygen radicals by procymidone in liver, kidney and lung of CD1 mice

Although chronic administration of procymidone (a widely used dicarboximide fungicide) leads to an increased incidence of liver tumors in mice, short-term genotoxicity studies proved negative. As cytochrome P450 (CYP) induction has been linked to non-genotoxic carcinogenesis, we investigated whether procymidone administration causes induction of CYP-dependent monooxygenases in liver, kidney and lung microsomes of male Swiss Albino CD1 mice after single or repeated (daily for three consecutive days) i.p. treatment with either 400 or 800 (1/10 or 1/20 of the DL(50)) mgkg(-1) b.w. procymidone. CYP content and CYP3A1/2, 1A1, 1A2, 2B1/2, 2E1, 2A, 2D9 and 2C11 supported oxidations were studied using either the regio- and stereo-selective hydroxylation of testosterone as multibiomarker or highly specific substrates as probes of various CYPs. While a single dose was uneffective, multiple procymidone administration lead to marked inductions of various monooxygenases: CYP3A1/2 in liver and lung (as measured by N-demethylation of aminopyrine and testosterone 6 beta-hydroxylase); CYP2E1 in liver (p-nitrophenol hydroxylation); CYP1A1 in liver and kidney (deethylation of ethoxyresorufin). Several hydroxylations were induced in the liver, including the CYP2A-linked 7 alpha (14-fold) as well as 6 alpha (22-fold), 6 beta, 16 beta and 2 beta hydroxylases. The pattern of inductions/suppressions recorded in the three different tissues suggests that procymidone exerts complex effects on the CYP profile. Tissue-specific trends included a large number of inductions in the liver and suppressions in the lung. The main inductions were corroborated by immunoblotting analyses and Northern blotting showed that inductions of CYP3A1/2, CYP2E1 and CYP1A1/2 were paralleled by increased mRNA levels. It was also found that CYP over-expression generates large amounts of reactive oxygen species (ROS), especially in liver. These data may explain why in vitro short-term genotoxicity studies on procymidone were negative, whereas in vivo long-term carcinogenesis studies turned out positive: long-term CYP induction (e.g. oxygen centered free radicals over-production) can have a co-carcinogenic and/or promoting potential.

Cytotoxic effects of two antimolting insecticides in mammalian CHO-K1 cells

Cytotoxicity of two insect growth regulators, diflubenzuron, a benzoylphenylurea derivative that inhibits the synthesis of new chitin in target organisms, and pyriproxyfen, an insect juvenile hormone analogue, were tested on CHO-K1 cultures, using the neutral red incorporation assay. Both compounds displayed cytotoxic effects that rise with time exposure. The presence of either fetal calf serum or bovine serum albumin diminished significantly the cytotoxicity of both compounds, thus pointing to a strong protein binding. In addition, extensive metabolization with rat liver submitochondrial fraction gave rise to metabolites less toxic than the parent compounds, implying the relative safety of both diflubenzuron and pyriproxyfen in mammals.

Induction and suppression of murine CYP-mediated biotransformation by dithianon: organ- and sex-related differences

With the aim of evaluating the co-carcinogenic properties of dithianon, the regio- and stereo-selective hydroxylation of testosterone was used as a multibiomarker of effect for cytochrome P450 (CYP) changes. CYP-catalysed reactions have been studied in liver, kidney and lung microsomes from male and female Swiss albino CD1 mice treated i.p. with single (3 or 6 mg/kg body wt.) or repeated (3 mg/kg body wt. daily for 3 days) doses of this fungicide. Induction or suppression was recorded under various situations in different organs and sexes. In liver, all testosterone hydroxylase (TH) activities were increased in the single treatment from 2.8- (6beta-, 16alpha- and 16beta-TH activities) to 16-fold (2beta-TH activity) in males at the lower dose. In contrast, activities were reduced from 33.3% (16beta- and 17-TH activities, lower dose) to 66.4% (16beta-TH activity, higher dose) in females. In kidney, a similar pattern of modulation was achieved: induction from 2.9- to 5-fold (6beta- and 2alpha-TH activities, higher and lower doses, respectively) in males; suppression from 47.4 to 50.2% (2alpha- and 2beta-TH activities, either at lower or higher doses) in females. In lung, a significant induction ranging from 7.1- to 29.3-fold (16alpha- and 2alpha-TH activities, respectively, lower dose) in males, and up to a 7-fold increase (2beta-TH activity, higher dose) in females was obtained. After repeated treatment, hepatic 6beta-, 16beta-, 2alpha- and 2beta-TH activities were reduced up to approximately 60% in males, whereas no effect was seen in females. In extrahepatic tissues, a generalized increase of different THs was observed. The increase of 6beta-TH activity (CYP3A-linked), one of the most representative isoforms in humans, was sustained in liver and kidney by means of Western immunoblotting, using rabbit polyclonal antibodies anti CYP3A1/2. On the whole, a complex pattern of induction/suppression of CYP-dependent reactions was achieved depending on sex and tissue. The data are consistent with co-toxic, co-carcinogenic and promoting potentials of this fungicide and provide information of interest in evaluating the risk associated with human exposure.

Genotoxicity and oxidative stress induced by pesticide exposure in bovine lymphocyte cultures in vitro

The genotoxic activity of the pesticides gliphosate, vinclozolin and DPX-E9636 was studied in in vitro cultures of bovine lymphocytes, using chromosome aberration (CA) and sister chromatid exchange (SCE) frequencies as genetic end-points and a variation of glucose 6-phosphate dehydrogenase (G6PD) enzyme activity as a marker of changes in the normal cell redox state. Results indicated a statistically significant increase of structural aberrations, sister chromatid exchanges and G6PD activity, suggesting that the pesticides tested induce either oxidative stress or a mutagenic effect in this species. The evaluation of both mitotic index and cell viability, after pesticide exposure, demonstrates a high cytotoxic effect which is always associated with the observed genotoxic effect.

Cytotoxic and cell transforming activities of the fungicide methyl thiophanate on BALB/c 3T3 cells in vitro

Cytotoxic and cell-transforming activities of methyl thiophanate a systemic fungicide capable of entering plant cells and thus controlling fungal diseases that have already started were studied in an in vitro medium-term (6-8 weeks) experimental model utilizing BALB/c 3T3 cells. Cells were exposed to the chemical, dissolved in dimethyl sulfoxide, in the absence or presence of an exogenous metabolizing system derived from rat livers supplemented with cofactors (S9 mix). In the absence of metabolic activation, methyl thiophanate exerted cytotoxic activity, evidenced through the formation of cell colonies, at low doses (> 10 micrograms/ml). However, the cytotoxic activity was greatly reduced by the S9 mix-induced metabolic activation of the chemical. Without bioactivation, cell-transforming potential, evidenced through the induction of transformation foci, was observable only at the highest (weakly toxic) dose employed (25 micrograms/ml). On the contrary, in the presence of metabolic activation, the cell-transforming activity was detectable at all tested doses (i.e. from 20 to 200 micrograms/ml) and it was particularly evident in a level-II transformation amplification test when the cells were allowed to perform active proliferative activity. These results, providing further information on the activity of methyl thiophanate in multistep carcinogenesis as possible genotoxic and/or co-carcinogenic agent, may contribute to better evaluate the oncogenic risk to man.

Biomarkers of effect in evaluating dithianon cocarcinogenesis: selective induction and suppression of murine CYP3A isoform

The ability of dithianon, whose mutagenic/cocarcinogenic activity has as yet not been clarified, to affect specific biomarkers of effect related to non-genotoxic cocarcinogenesis was investigated. For this purpose, several CYP-dependent reactions have been studied in liver, kidney and lung microsomes derived from male and female Swiss Albino CD1 mice treated i.p. with single (3 or 6 mg kg(-1) b.w.) or repeated (3 mg kg(-1) b.w., daily for 3 days) administrations of such fungicide. No significant changes in both absolute and relative liver, kidney and lung weights were achieved after dithianon treatment. Whereas a single dose was able to significantly induce certain monooxygenases, with repeated treatments a loss of activity was observed. For example, a approximately 2.4-fold increase of CYP3A-dependent activity, probed by N-demethylation of aminopyrine, was achieved in the liver (both sexes, lower dose) and, to a lesser extent, in lung. A small, but significant increase in the hydroxylation of p-nitrophenol (2E1) and in the O-deethylation of ethoxycoumarin (mixed) was also found in liver. With the exception of a approximately 46% loss in the 3A-like activity, no appreciable changes of the selected biomarkers were observed in kidney. Repeated dithianon doses were able to significantly reduce the 3A- and 2E1-dependent monooxygenases (approximately 30% and approximately 30% loss, respectively, averaged between male and female), as well as ethoxycoumarin O-deethylase activity (approximately 54% loss) in the liver. On the contrary, no significant CYP modulation in both kidney and lung was recorded. On the whole, dithianon has a complex pattern of CYP induction or suppression in various tissues of both sexes, suggesting the possible toxic/cotoxic and cocarcinogenic potential of this fungicide. These data can contribute to a better understanding of its toxicological profile, providing more information concerning the risk associated to human exposure.

Cytotoxic activity and transformation of BALB/c 3T3 cells in vitro by the insecticide acephate

Cytotoxic and cell transforming activity of the organophosphate insecticide acephate have been studied in an in vitro experimental model which foresees the exposure of BALB/c 3T3 cells to the chemical. The assay was performed in the presence or absence of metabolic activation system derived from phenobarbital and beta-naphthoflavone induced rats (S9-mix). Cytotoxicity of acephate was unaffected by the presence of the metabolizing fraction. Cell-transforming potential, evidenced through the induction of transformation foci, was observed at all tested doses (i.e. 100, 200 and 400 micrograms/ml) with or without exogenous bioactivation. This activity was related with cell proliferation since it was particularly evident in a level-II cell-transformation assay when the cells were allowed to perform active proliferative activity. These findings, obtained in a medium-term (6-8 weeks) test, may contribute to a better understanding of the action of acephate in the multistep carcinogenesis, proving more information on the oncogenic risk to humans.

In vitro transforming effect of the fungicides metalaxyl and zineb

The cytotoxic effects and the transforming properties of two fungicides, metalaxyl and zineb, whose mutagenic or carcinogenic activity has not been clarified yet, were analyzed in the in vitro BALB/c 3T3 cell transformation test both in the presence and in the absence of an exogenous metabolizing system. Zineb was completely detoxified when the exogenous metabolizing system was added to the target cells to increase their inherent metabolic capacity. Metalaxyl induced cell transformation at any assayed dosage, i.e., 500, 250, and 50 micrograms/ml, in the presence of bioactivation, and at the highest dosage (500 micrograms/ml) in the absence of bioactivation. The transforming effect was detectable only in the level-II transformation cultures and it was likely linked to the induction of additional cell proliferation which allowed obtaining the transformation amplification in these experimental conditions.

Genetic safety evaluation of pesticides in different short-term tests

Cyanazine, cyhexatin, dicamba and DNOC are pesticides commonly and broadly used in agriculture pest control. However, there is little information on their toxicity and mutagenicity in human cells and in whole animals. Therefore, UDS assay and SCE assay in human peripheral lymphocytes, and chromosome aberration analysis in bone marrow of rats have been used to assess the DNA-damaging activity of the above pesticides. Cyanazine proved non-genotoxic in all the test systems. Cyhexatin showed only weakly positive results for SCE induction in human lymphocytes, providing no concern for genotoxicological hazard. While dicamba did not show clastogenic effects in rodents, DNOC gave significant dose-related increases of structural chromosome aberrations in rat bone marrow cells. Female animals showed increased sensitivity to the toxic effects by DNOC at the highest dose. The results provide further information on the intrinsic genotoxic activity of the tested pesticides, which may contribute to the toxicological assessment of the risk associated with human exposure.

Genetic toxicity of a mixture of fifteen pesticides commonly found in the Italian diet

To determine the toxicological effects of complex mixtures of pesticides, we obtained data on 100 pesticide residues in common foods of central Italy. Fifteen pesticides were more regularly detected at higher levels (dithiocarbamates, benomyl/carbendazim, thiabendazole, diphenylamine, chlorthalonil, procymidone, fenarimol, chlorpropham, vinchlozolin, methidathion, chlorpyriphos-ethyl, parathion-methyl, parathion, chlorfenviphos, pirimiphos-ethyl). Using itemized data on daily food consumption in Italy, we calculated that the average exposure for an adult subject was 716 micrograms/day, ranging from 148 micrograms of dithiocarbamates to 1 microgram of pirimiphos-ethyl. We made a mixture of these 15 pesticides at concentrations proportional to the ratio determined in foods and tested it with the Salmonella-microsome assay, with and without metabolic activation with PCB-induced rat liver S9. No mutagenic activity was observed at concentrations up to 500 micrograms/plate. We also tested the same mixture at concentrations ranging from 0.1 to 20 micrograms/ml on human lymphocytes in vitro, and observed a slight but statistically significant increase in sister-chromatid exchanges at 1 microgram/ml. We also administered the mixture in corn oil by gavage to Wistar rats at doses of 1, 10, and 100 micrograms/kg. After 24 hr the ratio between bone marrow polychromatic and normochromatic lymphocytes (a sign of cellular toxicity) was decreased by the exposure, but we did not observe a significant increase in the frequency of micronuclei. We conclude that the pesticide mixture did not have appreciable genotoxic activity in the assays used.