Pesticide-induced alterations in zebrafish (Danio rerio) behavior, histology, DNA damage and mRNA expression: An integrated approach

To assess the impact of glyphosate and 2,4-D herbicides, as well as the insecticide imidacloprid, both individually and in combination, the gills of adult zebrafish were used due to their intimate interaction with chemicals diluted in water. Bioassays were performed exposing the animals to the different pesticides and their mixture for 96 h. The behavior of the fish was analyzed, a histological examination of the gills was carried out, and the genotoxic effects were also analyzed by means of the comet assay (CA) and the change in the expression profiles of genes involved in the pathways of the oxidative stress and cellular apoptosis. The length traveled and the average speed of the control fish, compared to those exposed to the pesticides and mainly those exposed to the mixture, were significantly greater. All the groups exposed individually exhibited a decrease in thigmotaxis time, indicating a reduction in the behavior of protecting themselves from predators. Histological analysis revealed significant differences in the structures of the gill tissues. The quantification of the histological lesions showed mild lesions in the fish exposed to imidacloprid, moderate to severe lesions for glyphosate, and severe lesions in the case of 2,4-D and the mixture of pesticides. The CA revealed the sensitivity of gill cells to DNA damage following exposure to glyphosate, 2,4-D, imidacloprid and the mixture. Finally, both genes involved in the oxidative stress pathway and those related to the cell apoptosis pathway were overexpressed, while the ogg1 gene, involved in DNA repair, was downregulated.

DNA damage, alterations in the expression of antioxidant enzyme genes and in the histoarchitecture of gill cells of zebrafish exposed to 17-α-ethinylestradiol

Endocrine disruptors, such as estrogen, are chemical substances with the potential to alter the hormonal balance of organisms. Their origin can be natural or artificial, and they can act at very low doses. The estrogen 17α-ethinylestradiol (EE2) is used worldwide as an oral contraceptive and is a potential contaminant in aquatic ecosystems. It is well documented that these environmental pollutants can act directly or indirectly on the reproductive system, impairing development and fertility. However, little is known about the alteration of the cell oxidative status induced by EE2. The main objective of this study was to evaluate the effect on the gill cells of adult zebrafish exposed in vivo to EE2, analyzing cell histology, DNA damage and the expression levels of genes encoding the main enzymes involved in oxidative stress pathways. The histological study showed that EE2 produces moderate to high damage to the gill tissue, an increase in gill cell DNA damage and the mRNA levels of the genes corresponding to the manganese superoxide dismutase (Mn-sod) and catalase (cat) after exposure to 5 ng/L EE2. The results indicate that EE2 causes tissue alterations, DNA damage and oxidative stress. EE2 produced important alterations in the gills, a fundamental organ for the survival of fish. There is a clear need for further research on the ecological consequences of EDCs on non-target organisms.

Alterations in the Expression of Antioxidant Enzyme Genes in Response to Pesticide Exposure During Embryonic Development in the Native Reptile Species Caiman latirostris

The aim of this study was to quantify the expression levels of Catalase (cat) and copper, zinc Superoxide dismutase (Cu, Zn-sod) genes involved in the antioxidant response in Caiman latirostris (broad-snouted caiman) blood, after embryonic exposure to the formulations cypermethrin (CYP), chlorpyrifos (CPF), glyphosate (GLY), and their binary and ternary mixtures. Experimental groups were: negative control (NC-distilled water), vehicle control (VC-ethanol), GLY-2%, CYP- 0.12%, CPF- 0.8%, a ternary mixture of them (TM), and three binary mixtures. The applications were made on the nest material in contact with the eggs at the beginning of the incubation period. After hatching, RNA was isolated from blood and expression levels analyzed through qPCR. The results showed downregulation in the expression of sod and cat genes in the three binary mixtures studied, compared to the controls. In addition, we found a possible antagonistic effect between different pesticides in the TM on the expression of both genes.

Genotoxicity and oxidative stress in Caiman latirostris hatchlings exposed to pesticide formulations and their mixtures during incubation period

Agricultural expansion and the consequent use of pesticides lead to the loss and fragmentation of natural habitats of several wild species. Then, many species are inevitably exposed to a wide amount of pesticide formulations. Glyphosate (GLY)-based formulations are the most used herbicide, whereas two of the most employed insecticides are chlorpyrifos (CPF) and cypermethrin (CYP). The aim of this study was to evaluate genotoxicity, oxidative damage, and the modulation of antioxidants defenses in peripheral blood of Caiman latirostris after embryonic exposure to pesticide formulations and their mixtures. Pesticides concentrations employed were equivalent to those recommended in agricultural practices for application in soybean crops and a half of them: GLY: 2% and 1%; CYP: 0.12% and 0.06%; CPF: 0.8% and 0.4%. Two similar experiments (E1 and E2) were carried out in consecutive years, where C. latirostris eggs were exposed to pesticide formulations separately and in different mixtures through application on the incubation material. After hatching, blood samples were taken and genotoxicity and oxidative stress was evaluated through the micronucleus (MN) test, the modified comet assay, the lipid peroxidation (LPO) levels and the activities of catalase (CAT) and superoxide dismutase (SOD) antioxidant enzymes. The results indicated the presence of DNA damage, oxidation of purines and pyrimidines, and increased frequency of micronucleus (FMN) in the case of GLY, CYP, and CPF formulations exposure, as well as in all the mixtures tested, with respect to the control groups. Specifically, the results observed for the mixtures would indicate independent action or antagonism of the components for DNA damage and base oxidation (purines and pyrimidines) and a possible potentiation interaction for the FMN in two binary mixtures. However, there were not differences regarding lipid peroxidation, the activity of antioxidant enzymes and growth parameters. This study proved that the use of pesticide formulations at concentrations used in the field generate deleterious genetic effects on this species, then, exposure to them could threaten its survival and health status.

Cypermethrin induction of DNA damage and oxidative stress in zebrafish gill cells

Cypermethrin (CYP) is a synthetic pyrethroid insecticide, used to control pests in domestic, industrial and agricultural environments. According to recent reports, it is one of the most common contaminants in freshwater aquatic systems. The aim of this study was to evaluate its potential genotoxic effect and the activation of the superoxide dismutase (SOD) and catalase (CAT) systems of adult zebrafish gill cells after in vivo exposure. The comet assay (CA) demonstrated that gill cells are sensitive to DNA damage after in vitro exposure to hydrogen peroxide (H₂O₂), showing a dose-dependent response. We also found an increase in DNA damage of gill cells following a dose- and time-dependent treatment with CYP. Moreover, it was verified that SOD and CAT activities significantly increased after exposure to 0.6 µg/L CYP, both during six and nine days. The same treatment caused a significant up-regulation of the mRNA levels of Mn-sod and cat genes. These data indicate that CYP causes gill cell's DNA damage and oxidative stress, modifying the activities of the enzymes responsible for maintaining ROS balance, as well as in their corresponding gene expression levels.

Oxidative damage and antioxidant defense in Caiman latirostris (Broad-snouted caiman) exposed in ovo to pesticide formulations

The surface used for agricultural production in Argentina significantly increased in recent years, mainly due to the expansion of soybean crops. As a result, the use of agrochemicals increased too. Many natural populations of Caiman latirostris (broad-snouted caiman) are affected by habitat fragmentation and the constant exposure to pesticides. This exposure could produce Reactive Oxygen Species. The negative imbalance between ROS generation and the capacity of the biological systems to eliminate the reactive intermediaries or avoid the damage is called Oxidative Stress. The aim of this study was to evaluate oxidative damage and antioxidant defense in C. latirostris hatchlings after in ovo exposure to widely used pesticide formulations. Embryos were exposed by topical exposure on the eggshell, from the beginning of incubation period, to sub-lethal concentrations of two glyphosate formulations: PanzerGold® (PANZ) and Roundup® Full II (RU): 500, 750, 1000 μg/egg; to the endosulfan (END) formulation Galgofan® and the cypermethrin (CYP) formulation Atanor®: 1, 10, 100, and 1000 μg/ egg. Blood samples were taken to all animals immediately after hatching for the application and comparison of the following oxidative stress biomarkers between the exposed groups and their respective controls: lipoperoxidation through thiobarbituric acid reactive substances (TBARS), DNA base oxidation through the modified comet assay, and the activities of Catalase (CAT) and Superoxide dismutase (SOD) in erythrocytes. Our results showed lipoperoxidation in caiman exposed to END (10, 100, 1000 µg/egg), CYP (1, 10, 1000 µg/egg), RU (500, 1000 µg/egg) and PANZ (500, 1000 µg/egg), DNA base oxidation in those exposed to END (10, 100, 1000 µg/egg), CYP (1, 10 µg/egg) and PANZ (500, 750 µg/egg) as well as alteration in the activity of SOD in END 1 µg/egg and CYP (10, 1000 µg/egg). This study demonstrated the incidence of oxidative stress in animals exposed to pesticide formulations widely used in agricultural activity associated mainly with soybean crops, and add further information to that previously reported about pesticide effects in this native reptile species.

Stress oxidative and genotoxicity in Prochilodus lineatus (Valenciennes, 1836) exposed to commercial formulation of insecticide cypermethrin

The use of toxic pesticides has become a world problem because they can contaminate streams and rivers, producing an adverse impact on non-target aquatic biota, including fishes. Cypermethrin is one of the most important insecticides to control ectoparasites in wide-scale. The aim of this study was to evaluate the effect of commercial formulations of cypermethrin, SHERPA O (0.0, 0.075, 0.15, and 0.3 µg/L of cypermethrin) in fish Prochilodus lineatus for 96 h in semi-static condition, using biomarkers of genotoxicity: micronucleus frequency (MNF) in erythrocytes and biomarkers of oxidative damage: lipid peroxidation (TBARS) and antioxidant defenses, catalase (CAT) and glutathione (GSH) in liver tissue. Our results showed a significant decrease (p < 0.05) of CAT at pesticide concentrations of 0.150 and 0.300 μg/L, but no significant difference was observed in TBARS or GSH in any exposed group (p > 0.05) in comparison to the control. A significant increase was observed in the MNF in the group exposed to 0.3 μg/L of cypermethrin compared to negative control (p < 0.05). Finally, P. lineatus proved to be a sensitive species to the commercial formulations of cypermethrin and that CAT and MNF are effective indicators of these toxic effects.

Cypermethrin: Oxidative stress and genotoxicity in retinal cells of the adult zebrafish

Cypermethrin (CM), widely used for control of indoor and field pests, is one of the most common contaminants in freshwater aquatic systems. We evaluated CM genotoxicity and the activities of superoxide dismutase (SOD) and catalase (CAT) in retinal cells of adult zebrafish. Histological and immunofluorescence techniques show the presence of apoptotic cells in the zebrafish retina after 9 d of treatment with 0.6 μg/L CM. Histone γ-H2AX, a marker of DNA damage, was detected in both outer and inner nuclear layers; caspase-3, an apoptotic marker, was detected in the outer nuclear layer. In the comet assay, the cells were sensitive to hydrogen peroxide-induced DNA damage, showing a dose-dependent response. We observed a positive comet assay response to CM that was dose- and time-dependent. Following exposure to CM, SOD and CAT enzyme activities, and sod and cat mRNA levels, increased. These results indicate that CM causes DNA damage and oxidative stress and can induce apoptosis in retinal cells.

Altered development, oxidative stress and DNA damage in Leptodactylus chaquensis (Anura: Leptodactylidae) larvae exposed to poultry litter

Poultry litter (PL), which is usually used as organic fertilizer, is a source of nutrients, metals, veterinary pharmaceuticals and bacterial pathogens, which, through runoff, may end up in the nearest aquatic ecosystems. In this study, Leptodactylus chaquensis at different development stages (eggs, larval stages 28 and 31 here referred to as stages I, II and III respectively) were exposed to PL test sediments as follows: 6.25% (T1), 12.5% (T2); 25% (T3); 50% (T4); 75% (T5); 100% PL (T6) and to dechlorinated water as control. Larval survival, development endpoints (growth rate -GR-, development rate -DR-, abnormalities), antioxidant enzyme activities (Catalase -CAT- and Glutathione-S-Transferase -GST-), and genotoxic effect (DNA damage index by the Comet assay) were analyzed at different times. In stage I, no egg eclosion was observed in treatments T3-T6, and 50% of embryo mortality was recorded after 24h of exposure to T2. In stages II and III, mortality in treatments T3-T6 reached 100% between 24 and 48h. In the three development stages evaluated, the DR and GR were higher in controls than in PL treatments (T1, T2), except for those T1-treated larvae of stage II. Larvae of stage I showed five types of morphological abnormalities, being diamond body shape and lateral displacement of the intestine the most prevalent in T1, whereas larvae of stages II and III presented lower prevalence of abnormalities. In stage I, CAT activity was similar to that of control (p>0.05), whereas it was higher in T1- and T2- treated larvae of stages II and III than controls (p<0.05). In stages I and III, GST activity was similar to that of controls (p>0.05), whereas it was inhibited in T1-treated larvae of stage II (p<0.05). T1- and T2-treated larvae of stages II and III caused higher DNA damage respect to controls (p<0.05), varying from medium to severe damage (comet types II, III and IV). These results showed that PL treatments altered development and growth and induced oxidative stress and DNA damage, resulting ecotoxic for L. chaquensis larvae.

Different end-points to assess effects in systemic lupus erythematosus patients exposed to pesticide mixtures

Systemic Lupus Erythematosus (SLE) is an autoimmune disease with high female predominance in reproductive years. It is characterized by a pronounced inflammation and production of a variety of autoantibodies. SLE pathogenesis is influenced by genes, hormones and environmental agents. The aim of this study was assess the possible effect of environmental pesticide mixtures in SLE patients. Oxidative DNA damage was measured using the comet assay modified by enzyme Endo III for detection of oxidized bases (Endo Sites), and oxidative stress by the measurement of the activity of catalase (CAT), superoxide dismutase (SOD) and lipid peroxidation (TBARS). Eighty-nine patients with diagnosis of SLE were included, 46% of them came from areas highly sprayed with pesticides and were compared with patients from urban areas with the same clinical and socio-demographic characteristics (p≥0.155). In order to identify factors that could predict DNA damage and oxidative stress, a binary logistic regression model with independent variables was developed: place of residence (p=0.007) have 75% of positive predictive value while smoking habit (p=0.186) have a 56% negative predictive value. The Odd Ratio (OR) obtained indicate that lupus patients living in rural areas presented 3.52 times more oxidative DNA damage compared to those living in the city. The prospects of applying biomarkers to assess exposure and biological effects, such as DNA damage and oxidative stress in autoimmune diseases, allow improving the characterization of individual risk.

Comet assay in gill cells of Prochilodus lineatus exposed in vivo to cypermethrin

Agricultural chemicals can induce genetic alterations on aquatic organisms that have been associated with effects on growth, reproduction and population dynamics. The evaluation of DNA damage in fish using the comet assay (CA) frequently involves the utilization of erythrocytes. However, epithelial gill cells (EGC) can be more sensitive, as they are constantly dividing and in direct contact with potentially stressing compounds from the aquatic environment. The aim of the present study was to evaluate (1) the sensitivity and suitability of epithelial gill cells of Prochilodus lineatus in response to different genotoxic agents through the application of the CA, (2) the induction of DNA damage in this cell population after in vivo exposure to cypermethrin. Baseline value of the CA damage index (DI) for EGC of juvenile P. lineatus was 144.68±5.69. Damage increased in a dose-dependent manner after in vitro exposure of EGC to methyl methanesulfonate (MMS) and H2O2, two known genotoxic agents. In vivo exposure of fish to cypermethrin induced a significant increase in DNA DI of EGC at 0.150μg/l (DI: 239.62±6.21) and 0.300μg/l (270.63±2.09) compared to control (150.25±4.38) but no effect was observed at 0.075μg/l (168.50±10.77). This study shows that EGC of this species are sensitive for the application of the CA, demonstrating DNA damage in response to alkylation (MMS), oxidative damage (H2O2), and to the insecticide cypermethryn. These data, together with our previous study on DNA damage induction on erythrocytes of this species, provides useful information for future work involving biomonitoring in regions where P. lineatus is naturally exposed to pesticides and other genotoxic agents.

Hepatic enzymes activity in the fish Prochilodus lineatus (Valenciennes, 1836) after sublethal cypermethrin exposure

Prochilodus lineatus, a fish, was exposed to sublethal concentrations of cypermethrin: 0.075, 0.150, and 0.300 μg L(-1) and a control group (without cypermethrin) for 96 h. Five specimens were exposed in each concentration for triplicate (n = 60). Hepatic biochemical values and behavioral changes were studied. The results revealed a significantly higher level of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase in hepatic tissue at different concentrations of cypermethrin tested compared to control (p < 0.05). A decrease in total protein was observed in exposed groups but not significantly (p > 0.05). This study provides information to know toxic mechanisms of cypermethrin on hepatic enzymes of P. lineatus that are poorly understood.

Alkaline comet assay for genotoxic effect detection in neotropical fish Prochilodus lineatus (Pisces, Curimatidae)

Toxicants on fish may induce genetic alterations that can be used as genotoxic markers. We evaluated DNA damage using alkaline comet assay applied on erythrocytes after in vivo exposure of Prochilodus lineatus to different concentrations of Cypermethrin (0.300, 0.150, 0.075 and 0.000 microg/L) as a probable chemical mutagen. The results revealed a significantly higher level of DNA damage at all concentrations of Cypermethrin tested compared to control and background level (p < 0.05). We have standardized the technique for one of the most common native fish species that will be useful for biomonitoring genotoxicity in polluted waters of the region.

DNA damage in workers occupationally exposed to pesticide mixtures

Pesticides are used in agriculture to protect crops but represent at the same time a potential risk to farmers and environment. The aim of this work is the evaluation of 54 subjects occupationally exposed to pesticides and 30 subjects as a control group using the quantification of DNA damage level by means of the alkaline Comet assay and the evaluation of repair processes. Damage index Comet assay (DICA) and damage index repair assay (DIRA) were studied in 27 pesticide applicator workers, 27 non-pesticide applicators and controls. Our results show that both exposed groups revealed significant increase in DICA when compared with controls (P < 0.0001), as well as in DIRA (P < 0.0001). However, the spraying group exhibited a marginally significant difference in DICA (P = 0.05) when years of exposure are considered and a significant difference (P < 0.05) when the personal protective equipment used by individuals was taken as a comparison factor. The influence of confounding factors on the genotoxic effects of occupational exposure to pesticides was investigated and no significant differences were observed considering age, gender, smoking and alcohol consumption in relation to DICA and DIRA. Since DNA damage is an important step in events leading from carcinogen exposure to cancer disease, our study highlights the potential health risk associated with agrochemical exposure in developing countries with vast cultivated areas, such as Argentina.