Histopathological and Behavioral Impairments in Zebrafish (Danio rerio) Chronically Exposed to a Cocktail of Fipronil and Pyriproxyfen.

BACKGROUND: Lately, the high incidence of pesticide usage has attracted everyone's interest due to the serious effects produced. Fipronil (FIP) is a phenylpyrazole compound that acts on the insect's GABA neurotransmitter by inhibiting its activity. Moreover, the literature reports highlight its implication in neurodevelopmental abnormalities and oxidative stress production in different organisms. Similarly, pyriproxyfen (PYR) is known to affect insect activity by mimicking the natural hormones involved in the maturation of the young insects. The aim of the present study was to investigate the impact of the mixture of these pesticides on the tissues and behavior of zebrafish. METHODS: To assess the influence of this cocktail on zebrafish, three groups of animals were randomly selected and exposed to 0, 0.05, and 0.1 mg L-1 FIP and PYR mixture for five days. The fish were evaluated daily by the T-maze tests for locomotor activity and the light-dark test and recordings lasted four min. The data were quantified using the EthoVision software. RESULTS: Our results indicated significant changes in locomotor activity parameters that showed increased levels following exposure to the mixture of FIP and PYR. On the other hand, the mixture also triggered anxiety in the zebrafish, which spent more time in the light area than in the dark area. In addition, mixture-induced histological changes were observed in the form of numerous hemosiderin deposits found in various zebrafish tissues. CONCLUSIONS: The current findings indicate that the mixture of FIP and PYR can have considerable consequences on adult zebrafish and may promote or cause functional neurological changes in addition to histological ones.

Assessing the Neurotoxicity of a Sub-Optimal Dose of Rotenone in Zebrafish (Danio rerio) and the Possible Neuroactive Potential of Valproic Acid, Combination of Levodopa and Carbidopa, and Lactic Acid Bacteria Strains.

Parkinson's disease (PD) is an enigmatic neurodegenerative disorder that is currently the subject of extensive research approaches aiming at deepening the understanding of its etiopathophysiology. Recent data suggest that distinct compounds used either as anticonvulsants or agents usually used as dopaminergic agonists or supplements consisting of live active lactic acid bacteria strains might alleviate and improve PD-related phenotypes. This is why we aimed to elucidate how the administration of rotenone (ROT) disrupts homeostasis and the possible neuroactive potential of valproic acid (VPA), antiparkinsonian agents (levodopa and carbidopa - LEV+CARB), and a mixture of six Lactobacillus and three Bifidobacterium species (PROBIO) might re-establish the optimal internal parameters. ROT causes significant changes in the central nervous system (CNS), notably reduced neurogenesis and angiogenesis, by triggering apoptosis, reflected by the increased expression of PARKIN and PINK1 gene(s), low brain dopamine (DA) levels, and as opposed to LRRK2 and SNCA compared with healthy zebrafish. VPA, LEV/CARB, and PROBIO sustain neurogenesis and angiogenesis, manifesting a neuroprotective role in diminishing the effect of ROT in zebrafish. Interestingly, none of the tested compounds influenced oxidative stress (OS), as reflected by the level of malondialdehyde (MDA) level and superoxide dismutase (SOD) enzymatic activity revealed in non-ROT-exposed zebrafish. Overall, the selected concentrations were enough to trigger particular behavioral patterns as reflected by our parameters of interest (swimming distance (mm), velocity (mm/s), and freezing episodes (s)), but sequential testing is mandatory to decipher whether they exert an inhibitory role following ROT exposure. In this way, we further offer data into how ROT may trigger a PD-related phenotype and the possible beneficial role of VPA, LEV+CARB, and PROBIO in re-establishing homeostasis in Danio rerio.

Toxicity and chronic effects of deltamethrin exposure on zebrafish (Danio rerio) as a reference model for freshwater fish community.

In this study zebrafish specimens were exposed for 15 days to 0.25, 0.5, 1 and 2 µg L-1 non-lethal concentrations of deltamethrin (DM) knowing that is the active compound in insecticides used on agricultural crops. They were investigated important issues resulted during the chronic exposure with DM: effects on aggressive behavior and swimming performances knowing that is a high neurotoxic compound; toxicity on nervous system investigated on telencephalon, optic tectum and cerebellum; activity of PCNA, p53 and TUNEL as toxicity markers in immunocytochemistry of the histological samples; changes of elements concentrations in the fish body and their role in detoxification of DM. This scenario investigated the harmful effects of this compound for freshwater fish communities. The aggressive behavior significantly increased and remained constant for the concentration 0.5 µg L-1. They were not evidences in changing of anxiety level and swimming performances. The nervous system suffered significant damage for all studied concentrations and confirmed the changes in the behavior. Selenium concentration in the body decreased and may be involved in the detoxification processes.

Acute exposure to gold induces fast changes in social behavior and oxidative stress of zebrafish (Danio rerio).

Gold is a noble metal having a long history of human usage and a variety of applications. The present paper was designed in order to see the changes on social and swimming behavior of zebrafish caused by acute gold exposure to high concentrations dissolved in aquatic medium from a standard solution with the highest purity. Some main oxidative stress markers were determined such as: superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and glutathione peroxidase (GPx). We also focused our attention on the bioaccumulation capacity of gold in exposed zebrafish and its competition with essential elements for the body: sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn) and copper (Cu). They were studied the effects of the follow gold concentrations dissolved in experimental aquariums: 1 mg L-1 (Au 1 mg/L), 2 mg L-1 (Au 2 mg/L), 4 mg L-1 (Au 4 mg/L) and 8 mg L-1 (Au 8 mg/L). Our data showed that each group treated with gold had a higher concentration compared with the others suggesting that it can be absorbed into the zebrafish body from environment and may be accumulated. The results obtained in the oxidative stress parameters demonstrated that it can produce changes as a response to its toxicological effects.