Molecular and Biochemical Evidence of the Toxic Effects of Terbuthylazine and Malathion in Zebrafish

SIMPLE SUMMARY: Due to the global increase in pesticide applications, aquatic animals are constantly subjected to their action in natural reservoirs. Terbuthylazine and malathion, two commonly detected pesticides in water and soil samples elsewhere, have been shown to have a significant negative impact on zebrafish, even at environmentally realistic concentrations. They can induce oxidative stress, mitochondrial and lysosomal destabilization, leading to immune toxicity, cytotoxicity, and DNA damage. All of these adverse outcomes might severely impact the health status of fish before being translated into an effect on the population. The present study should emphasize the importance of paying attention to pesticide traces in the environment, which can have devastating effects on biota even at low concentrations. ABSTRACT: 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.