Modulation of redox and insulin signaling underlie the anti-hyperglycemic and antioxidant effects of diphenyl diselenide in zebrafish.

The organic selenium compound diphenyl diselenide (DD) has been recognized as an antioxidant and neuroprotective agent, exerting an anti-hyperglycemic effect in experimental models of diabetes. However, the precise mechanisms involved in the protection are unclear. Using the zebrafish (Danio rerio) as a model organism, here we investigated biomarkers underlying the protective effects of DD against hyperglycemia, targeting in a transcriptional approach the redox and insulin-signaling pathway. Fish were fed on a diet containing DD (3 mg/kg) for 74 days. In the last 14 days, they were exposed to a 111 mM glucose solution to induce a hyperglycemic state. DD reduced blood glucose levels as well as normalized the brain mRNA transcription of four insulin receptors-coding genes (Insra1, Insra2, Insrb1, Insrb2), which were down-regulated by glucose. DD alone caused an up-regulation of relative mRNA transcription in both Insra receptors and glucose transporter 3 genes. DD counteracted hyperglycemia-induced lipid peroxidation, protein and thiol depletion. Along with the decreased activity of antioxidant enzymes SOD and GPx, the brain of hyperglycemic fish presented a reduction in mRNA transcription of FoxO3A, FoxO3B, Nrf2, GPx3A, SOD1, and SOD2 genes. Besides normalizing the transcriptional levels, DD caused an up-regulation of relative mRNAs that encode Nrf2, FoxO1A, FOXO3A, GPx4A, PTP1B, AKT and SelP. Collectively, our findings suggest that the antioxidant and anti-hyperglycemic actions of DD in a zebrafish diabetes model are likely associated with the regulation of the oxidative stress resistance and the insulin-signaling pathway and that could be related to the modulation at mRNA level of two important transcription factors, Nrf2 and FoxO.

Exploring Object Discrimination in Zebrafish: Behavioral Performance and Scopolamine-Induced Cognitive Deficits at Different Retention Intervals.

The object discrimination test allows the testing of different memory retention periods. However, few behavioral endpoints have been measured in fish species such that retention is often assessed using a single parameter (time spent in object area). Here, we aimed to explore the object discrimination test in zebrafish by assessing their behavioral performance after 1 or 24 h retention interval periods. To characterize putative interaction-like behaviors, fish were tested in the absence or presence of scopolamine (1 h before test session). Zebrafish were habituated for 3 consecutive days in the experimental tank, and training session was performed for 10 min using two identical nonpreferred objects (black cube or sphere). After the retention intervals, a familiar object was replaced by a novel object (test session, 10 min). Fish were also exposed to the novel tank diving test to assess locomotion and anxiety-like behaviors. At 1 h retention interval, animals performed more circular-like investigation near the familiar object, whereas 24 h after training session, a prominent rapid investigation was observed when animals explore the nonfamiliar object. Because scopolamine abolished these phenotypes, as well as the increased time spent in the novel object area during the test without changing locomotion and anxiety-related parameters, the behavioral responses described here may predictively reflect interaction-like behaviors involved in object discrimination memory in zebrafish models.

Taurine Protects from Pentylenetetrazole-Induced Behavioral and Neurochemical Changes in Zebrafish.

Epilepsy is a common neurological disorder characterized by recurrent unprovoked seizures, which culminate in various neurobehavioral and neurochemical changes. Taurine (TAU) is an amino sulfonic acid which acts an endogenous inhibitory neuromodulator. Moreover, TAU displays intrinsic antioxidant activity, contributing to its beneficial actions in the CNS. Here, we evaluated whether TAU pretreatment protects from pentylenetetrazole (PTZ)-induced behavioral alterations and oxidative stress-related parameters in zebrafish brain tissue. Fish were pretreated with 42, 150, and 400 mg/L TAU (40 min) and further exposed to 10 mM PTZ (20 min) to analyze the seizure-like behaviors. As a positive control, another group was previously treated with 75 µM diazepam (DZP). Afterwards, biochemical experiments were performed. All TAU concentrations tested decreased seizure intensity in the first 150 s. Importantly, 150 mg/L TAU attenuated seizure-like behavioral scores, decreased seizure intensity, reduced the frequency of clonic-like seizures (score 4), and increased the latency to score 4. TAU (150 mg/L) also prevented oxidative stress in PTZ-challenged fish by decreasing lipid peroxidation and protein carbonylation and preventing changes on nonprotein thiol levels. No significant changes were observed in MTT assay and LDH activity. Differently than observed in DZP group, TAU did not affect the overall swimming activity of fish, suggesting different mechanisms of action. Collectively, we show that TAU attenuates PTZ-induced seizure-like behaviors and brain oxidative stress in zebrafish, suggesting the involvement of antioxidant mechanisms in neuroprotection.

Single pentylenetetrazole exposure increases aggression in adult zebrafish at different time intervals.

Epilepsy is characterized by abnormal and recurrent hyperexcitability in brain cells. Various comorbidities are associated with epilepsy, including irritability and aggressive behavior. Aggression is a negative effect observed in epileptic patients that may be harmful to other individuals, impairing social relations. Thus, developing novel experimental models to assess behavioral phenotypes that may comorbid with neurological disorders are of great interest. Here, we investigate whether pentylenetetrazole (PTZ) increases aggression in zebrafish following a single exposure. Animals were exposed to 10 mM PTZ for 20 min and aggression-towards mirror was measured at different time intervals after recovering period (1 h, 3 h, 6 h, 24 h, 48 h, and 72 h). We observed that zebrafish showed exacerbated aggression, as well as an increased number of entries in the virtual conspecific area from 1 h to 48 h after PTZ. However, no behavioral differences were observed after 72 h. Overall, our novel findings show that a single PTZ exposure evokes aggression in a time-dependent manner, reinforcing the use of zebrafish models to explore epilepsy-related comorbidities.

Oxidative effects of the acute exposure to a pesticide mixture of cypermethrin and chlorpyrifos on carp and zebrafish - A comparative study.

The use of commercial pesticides combinations increases the risk of intoxication in non-target aquatic organisms. Here, we investigate the potential of a commercial pesticide formulation containing (CYP) plus chlorpyrifos (CPF) to induce oxidative damage on two fish species (common carp and zebrafish). Carp and zebrafish were exposed for 96 h under laboratory conditions. Fish were divided in three different groups: CTL, 0.3 µg L-1 or 0.6 µg L-1 of CYP and 0.5 or 1 µg L-1 of CPF in commercial formulation. Both carp and zebrafish showed an increase in lipid peroxidation (LPO) and glutathione-S-transferase (GST) activity when compared to control group. Other oxidative parameters responded differently to exposure in carp and zebrafish. There were an increase in ascorbic acid (ASA) levels and decrease in catalase (CAT) activity and non-protein thiols (NPSH) levels in treated groups of carps. In the other hand, zebrafish showed significant decrease in ASA and increase in CAT activity and NPSH levels. Overall, we demonstrate noxious effects on redox parameters in two fish experimental models and different effects were observe in each fish species exposed to commercial pesticide formulation. This difference responses observed can be related with specific mechanisms of detoxification and antioxidant defense system of each species.

Sodium Selenite Prevents Paraquat-Induced Neurotoxicity in Zebrafish.

Considering the antioxidant properties of sodium selenite (Na2SeO3) and the involvement of oxidative stress events in paraquat-induced neurotoxicity, this study investigated the protective effect of dietary Na2SeO3 on biochemical and behavioral parameters of zebrafish exposed to paraquat (PQ). Fish were pretreated with a Na2SeO3 diet for 21 days and then PQ (20 mg/kg) was administered intraperitoneally with six injections for 16 days. In the novel tank test, the Na2SeO3 diet prevented the locomotor impairments, as well as the increase in the time spent in the top area of the tank, and the exacerbation of freezing episodes. In the preference for conspecifics and in the mirror-induced aggression (MIA) tasks, Na2SeO3 prevented the increase in the latency to enter the area closer to conspecifics and the agonistic behavior of PQ-treated animals, respectively. Na2SeO3 prevented the increase of carbonylated protein (CP), reactive oxygen species (ROS), and nitrite/nitrate (NOx) levels, as well as the decrease in non-protein thiols (NPSH) levels. Regarding the antioxidant enzymatic defenses, Na2SeO3 prevented the increase in catalase (CAT) and glutathione peroxidase (GPx) activities caused by PQ. Altogether, dietary Na2SeO3 improves behavioral and biochemical function impaired by PQ treatment in zebrafish, by modulating not only redox parameters, but also anxiety- and aggressive-like phenotypes in zebrafish.

CYP2B6 516 G>T polymorphism and side effects of the central nervous system in HIV-positive individuals under Efavirenz treatment: Study of a sample from southern Brazil.

This study aimed to identify the 516 G>T polymorphism of the CYP2B6 gene and evaluate its influence on central nervous system (CNS) side effect development in HIV-positive individuals undergoing Efavirenz (EFV) treatment in a population from southern Brazil. Additionally, we performed a survey on the clinical and epidemiological characteristics of our sample. In addition to medical records evaluation, whole blood of 89 individuals was analyzed for viral load, T lymphocyte count (CD4+ and CD8+), and the polymorphism. Considering the side effects of the CNS reported by individuals but without considering the genetic variables, no statistically significant association was noted between the adverse effects and the antiretroviral treatment (including or not EFV). In addition, no statistically significant difference was noted for the influence of genotype on the viral load or the number of T lymphocytes (CD4+ and CD8+) among individuals undergoing EFV treatment. This is the first study that investigated the impact of the 516 G>T polymorphism of the CYP2B6 gene among HIV-positive individuals from southern Brazil. Its clinical significance indicates the need for prospective studies in this population.

CYP2B6 516 G>T polymorphism and side effects of the central nervous system in HIV-positive individuals under Efavirenz treatment: Study of a sample from southern Brazil

ABSTRACT This study aimed to identify the 516 G>T polymorphism of the CYP2B6 gene and evaluate its influence on central nervous system (CNS) side effect development in HIV-positive individuals undergoing Efavirenz (EFV) treatment in a population from southern Brazil. Additionally, we performed a survey on the clinical and epidemiological characteristics of our sample. In addition to medical records evaluation, whole blood of 89 individuals was analyzed for viral load, T lymphocyte count (CD4+ and CD8+), and the polymorphism. Considering the side effects of the CNS reported by individuals but without considering the genetic variables, no statistically significant association was noted between the adverse effects and the antiretroviral treatment (including or not EFV). In addition, no statistically significant difference was noted for the influence of genotype on the viral load or the number of T lymphocytes (CD4+ and CD8+) among individuals undergoing EFV treatment. This is the first study that investigated the impact of the 516 G>T polymorphism of the CYP2B6 gene among HIV-positive individuals from southern Brazil. Its clinical significance indicates the need for prospective studies in this population.

Chronic Treatment with Paraquat Induces Brain Injury, Changes in Antioxidant Defenses System, and Modulates Behavioral Functions in Zebrafish.

Paraquat (PQ) administration consists in a chemical model that mimics phenotypes observed in Parkinson's disease (PD), due to its ability to induce changes in dopaminergic system and oxidative stress. The aim of this study was to evaluate the actions of PQ in behavioral functions of adult zebrafish and its influence on oxidative stress biomarkers in brain samples. PQ (20 mg/kg) was administered intraperitoneally with six injections for 16 days (one injection every 3 days). PQ-treated group showed a significant decrease in the time spent in the bottom section and a shorter latency to enter the top area in the novel tank test. Moreover, PQ-exposed fish showed a significant decrease in the number and duration of risk assessment episodes in the light-dark test, as well as an increase in the agonistic behavior in the mirror-induced aggression (MIA) test. PQ induced brain damage by decreasing mitochondrial viability. Concerning the antioxidant defense system, PQ increased catalase (CAT) and glutathione peroxidase (GPx) activities, as well as the non-protein sulfhydryl content (NPSH), but did not change ROS formation and decreased lipid peroxidation. We demonstrate, for the first time, that PQ induces an increase in aggressive behavior, alters non-motor patterns associated to defensive behaviors, and changes redox parameters in zebrafish brain. Overall, our findings may serve as useful tools to investigate the interaction between behavioral and neurochemical impairments triggered by PQ administration in zebrafish.