Efeitos do inseticida permetrina sobre o desenvolvimento de peixes-zebra

Abstract

Permethrin (PM) is a Type I synthetic pyrethroid (SP) widely used in crops and especially in domestic environments to control harmful insects. Pyrethroids are considered safe, with low mammalian toxicity. However, studies have indicated the potential toxic effects of this compound to developing organisms. The present work aimed to investigate the toxicity mechanisms of PM on behavior, redox homeostasis and cellular respiration from early stages of development until the adulthood. This work was divided into two chapeters: (I) lethal and non-lethal PM concentrations were determined in acutely exposed zebrafish larva, where the LC50 was found to be 108 μg/L in this model and the sublethal concentrations of 25 and 50 μg/L were determined and used for subsequent analyzes. It was observed that both concentrations were able to cause redox unbalance, leading to the increased reactive oxygen species (ROS). Consequently, oxidative damage on biomolecules, genotoxicity and apoptosis induction was also observed. On the other hand, there was activation of the antioxidant defense system, which was not sufficient to neutralize oxidative damage, characterizing the oxidative stress state due to exposure to PM. At this same stage itwas observed a significant decrease in cellular respiration and a shift in aerobic energy metabolism, which, alltogether with oxidative damage, could influence the anxiety-related non-motor behavioral changes observed in chapter I. In chapter (II) the effects of PM exposure on zebrafish development were assessed by determining behavioral patterns at key developmental stages. At this stage the zebrafish embryos were exposed only during the first 24h of development. We observed that exposure was able to alter basal behaviors such as spontaneous movements even during the embryonic stage, as well as in the later stages of development until adulthood. Behaviors related to anxiety and fear were altered during the larval period and persisted until adulthood, when increase of aggressiveness parameters were also observeded. These results indicate that damage caused by embryonic exposure to PM persisted during development and led to behavioral changes in adulthood, which may be related to anxiety and depression disorders. Taken together, the two chapters of the study corroborate to the understanding of the toxicity mechanisms of PM on developing organisms and their relationship with behavioral disorders, and contribute to the validation of the zebrafish model for neurodevelopmental studies linked to environmental contaminants.