Pesticides are well known for their high levels of persistence and ubiquity in the environment, and because of their capacity to bioaccumulate and disrupt the food chain, they pose a risk to animals and humans. With a focus on organophosphate and triazine pesticides, the present review aims to describe the current state of knowledge regarding spatial distribution, bioaccumulation, and mode of action of frequently used pesticides. We discuss the processes by which pesticides and their active residues are accumulated and bioconcentrated in fish, as well as the toxic mechanisms involved, including biological redox activity, immunotoxicity, neuroendocrine disorders, and cytotoxicity, which is manifested in oxidative stress, lysosomal and mitochondrial damage, inflammation, and apoptosis/autophagy. We also explore potential research strategies to close the gaps in our understanding of the toxicity and environmental risk assessment of organophosphate and triazine pesticides.

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The aim of the present work was to investigate the response of zebrafish to the effects of widely-used organophosphates roundup and chlorpyrifos and putative effectiveness of chlorella in terms of decreasing pesticides toxicity. Studied organophosphate pesticide roundup and chlorpyrifos in ecologically relevant concentrations, both individually and in a mixture, evoked the prominent suppression of catalase and total antioxidant capacity in the liver of Danio rerio which were consistent with higher levels of lipid peroxidation, protein carbonylation, and DNA strand break. Also, both roundup and chlorpyrifos provoked endocrine disorders registered as induction of vitellogenin and depletion of triiodothyronine as well as neurotoxicity appeared as inhibition of acetylcholinesterase after individual action or activation after combined action. The rate of apoptosis observed by caspase 3 activity was decreased, but in different manner depends on the exposure. The potency of toxicity followed the order: roundup > chlorpyrifos > roundup + chlorpyrifos (due to some kind of antagonistic action between chlorpyrifos and roundup in the binary mixture). Based on the results of CART analysis triiodothyronine, TBARS and caspase 3 were determined as the most significant indices for discrimination of the studied groups. The introduction of Chlorella vulgaris in the amount of about 100 thousand cells L-1 into the environment did not show a significant bioremediation effect on the harmful effect of studied pesticides for Danio rerio, which does not exclude the positive impact of algae on the functioning of the ecosystem as a whole and requires further comprehensive research.

The ecological potential of microalgae for purification of aquatic and soil ecosystems and natural restoration of their homeostatic functional state is considered to be high due to the rapid growth and development of algae, their labile and dynamic metabolism and simple growth conditions. The aim of present work was to study the effectiveness of Chlorella as a potential bioremediator to reduce the toxic effects of pesticides, roundup and chlorpyrifos after their individual and complex influence on zebrafish Danio rerio. The effect of environmental concentrations of roundup (15 μg⋅L-1) and chlorpyrifos (0,1 μg⋅L-1) provoked partial depletion of the cell thiols pool when compared to the control, which appeared as a decrease in glutathione transferase activity (under combined exposure) and total glutathione concentration. A decrease in the level of total antioxidant capacity, which was consistent with an increase in the level of reactive oxygen species in the liver tissue was also shown. Meanwhile, the studied organophosphate pesticides didn’t cause severe signs of neurotoxicity, but activated acetylcholinesterase in line with no visual manifestations of locomotion reactions. Chlorpyrifos determined an increase in the concentration of methylglyoxal and the most noticeable sign of endocrine disruption from all studied groups in terms of vitellogenin concentration. Principal component analysis allowed to identify a separate localization of each of the studied groups and the interim position of animals after combined exposure when compared to the individual action. The introduction of Chlorella vulgaris in the exposure media in the amount of about 100 thousand cells / dm3 did not show a significant corrective effect on the toxicity of pesticides for non-target species Danio rerio, which doesn’t exclude the positive impact of algae on the functioning of the ecosystem in general and requires a more detailed analysis.

In the context of the global increase in pesticide applications, aquatic animals are constantly subjected to their action in natural reservoirs. Our research sought to determine the molecular and biochemical effects of an environmental exposure to commonly used chloro-s-triazine herbicide terbuthylazine and organophosphate insecticide malathion on zebrafish. To this aim, mature zebrafish were exposed to 2 and 30 µg L−1 terbuthylazine and 5 and 50 µg L−1 malathion alone and in combination for 14 days. Following exposure, induction of reactive oxygen and nitrogen species, lipid peroxidation, and protein carbonylation in the liver of treated zebrafish have been registered. Aside from the accumulation of oxidative lesions, a decrease in antioxidants and succinate dehydrogenase activity, an increase in oxidized glutathione, and enhanced apoptosis via Caspase-3 and BAX overexpression (in the case of terbuthylazine) were observed. Furthermore, terbuthylazine and malathion induced mitochondrial swelling and lactate dehydrogenase leakage in a concentrationdependent manner. Significant upregulation of ubiquitin expression and increasing cathepsin D activity were characteristics that appeared only upon terbuthylazine exposure, whereas induction of IgM was identified as the specific characteristic of malathion toxicity. Pesticides in the studied concentration didn’t provoke significant alterations in the hypothalamic-pituitary-thyroid axis in zebrafish. Co-exposure increased adverse effects of individual pesticides to zebrafish. This study should improve understanding of the mechanisms of pesticide toxicity that leads to fish impairment and biodiversity decline, as well as emphasize the importance of paying attention to pesticide traces in the environment and fish, which can have devastating effects on biota even at low concentrations.

Our research sought to determine the molecular and biochemical effects of environmentally relevant exposure to commonly used chloro-s-triazine herbicide terbuthylazine and organophosphate insecticide malathion on zebrafish. To this aim, mature zebrafish were exposed to 2 and 30 µg L−1 terbuthylazine and 5 and 50 µg L−1 malathion alone and in combination for 14 days. Aside from the accumulation of TBARS and protein carbonyls, a decrease in antioxidants and succinate dehydrogenase activity, an increase in oxidized glutathione, and enhanced apoptosis via Caspase-3 and BAX overexpression were observed. Furthermore, terbuthylazine and malathion induced mitochondrial swelling (up to 210% after single exposure and up to 470% after co-exposure) and lactate dehydrogenase leakage (up to 268% after single exposure and up to 570% after co-exposure) in a concentration-dependent manner. Significant upregulation of ubiquitin expression and increased cathepsin D activity were characteristics that appeared only upon terbuthylazine exposure, whereas the induction of IgM was identified as the specific characteristic of malathion toxicity. Meanwhile, no alterations in the zebrafish hypothalamic-pituitary-thyroid axis was observed. Co-exposure increased the adverse effects of individual pesticides on zebrafish. This study should improve the understanding of the mechanisms of pesticide toxicity that lead to fish impairment and biodiversity decline.