Brain oxidative stress mediates anxiety-like behavior induced by indomethacin in zebrafish: protective effect of alpha-tocopherol.

RATIONALE: Indomethacin (INDO) is a widely utilized non-steroidal anti-inflammatory drug (NSAID) with recognized effect on the central nervous system. Although previous reports demonstrate that prolonged treatment with indomethacin can lead to behavioral alterations such as anxiety disorder, the biochemical effect exerted by this drug on the brain are not fully understood. OBJECTIVES: The aim of present study was to evaluate if anxiety-like behavior elicited by indomethacin is mediated by brains oxidative stress as well as if alpha-tocopherol, a potent antioxidant, is able to prevent the behavioral and biochemical alterations induced by indomethacin treatment. METHODS: Zebrafish were utilized as experimental model and subdivided into control, INDO 1 mg/Kg, INDO 2 mg/Kg, INDO 3 g/Kg, α-TP 2 mg/Kg, α-TP 2 mg/Kg + INDO 1 mg/Kg and α-TP + INDO 2 mg/Kg groups. Vertical distributions elicited by novelty and brain oxidative stress were utilized to determinate behavioral and biochemical alterations elicited by indomethacin treatment, respectively. RESULTS: Our results showed that treatment with indomethacin 3 mg/kg induces animal death. No changes in animal survival were observed in animals treated with lower doses of indomethacin. Indomethacin induced significant anxiogenic-like behavior as well as intense oxidative stress in zebrafish brain. Treatment with alpha-tocopherol was able to prevent anxiety-like behavior and brain oxidative stress induced by indomethacin. CONCLUSIONS: Data presented in current study demonstrated for the first time that indomethacin induces anxiety-like behavior mediated by brain oxidative stress in zebrafish as well as that pre-treatment with alpha-tocopherol is able to prevent these collateral effects.

Putative Activation of Cannabinoid Receptor Type 1 Prevents Brain Oxidative Stress and Inhibits Aggressive-Like Behavior in Zebrafish.

Background: Aggression is a set of complex behaviors commonly described in different neurological disorders, such as schizophrenia, autistim spectrum disorder, and anxiety. Previous studies have described that some changes in the redox status of the brain are closely associated with aggressive behavior in different species. In addition, the endocannabinoid system acts as a neuromodulator of the central nervous system, however, its participation in aggressive behavior needs to be elucidated. Danio rerio (zebrafish) is an important model in the study of aggression, in this context, the present study investigated whether the activation of type 1 cannabinoid receptors (CB1r) alters the cerebral redox state and aggressive behavior in zebrafish. Materials and Methods: We performed pharmacological manipulations with the CB1r agonist (ACEA) and antagonist (AM-251) to assess the role of this receptor in aggressive behavior. Individuals were isolated in pairs, without physical contact for 24 h, treated with the drugs of interest, and after 30 minutes of pharmacokinetics, the fights were filmed for 30 min, and the individuals were identified as dominant or subordinate. Results: A consistent decrease in the strike and bite aggressive behavior was observed in the group treated with the ACEA agonist compared with that in the control and AM-251 groups. When evaluating the cerebral redox state, we observed that treatment with the ACEA agonist reduced malondialdehyde (MDA) levels and increased the levels of sulfhydryl groups compared with those in the control group. These results indicate that the activation of CB1r by the ACEA agonist inhibited aggressiveness and attenuated the levels of oxidative stress in both subjects (dominant or subordinate) in the treated group. Conclusion: Thus, we suggest that zebrafish is an alternative model to study common aggressive behavior disorders among species and that CB1r represent a potential target for the development of treatments for aggressive disorders.

Açaí (Euterpe oleracea) pulp-enriched diet induces anxiolytic-like effects and improves memory retention.

Background: Açaí (Euterpe oleracea) has a rich nutritional composition, showing nutraceutical and protective effects in several organs. In this study, the effects of an açaí-enriched diet on motor performance, anxiety-like behavior, and memory retention were deeply investigated. Methods: Eight-week male Wistar rats were fed with an Euterpe oleracea (EO) pulp-enriched diet, an olive oil-enriched (OO) diet (polyunsaturated fatty acid [PUFA] fat control diet), or a chow diet for 31 days (28 days pre-treatment and 3 days during behavioral tests). Afterward, animals were submitted to a battery of behavioral tests to evaluate spontaneous motor behavior (open-field test), anxiety-like behavior (elevated plus maze and open-field test), and memory retention (step-down). Oxidative stress in the hippocampus was evaluated by a lipid peroxidation assay. Results: EO-enriched diet did not influence the body weight and food intake but increased the glucose plasmatic level after 31 days under this diet. However, a similar fat-enriched diet stimulated a marked weight gain and reduced the food intake, followed by changes in the plasmatic lipid markers. EO-enriched diet preserved the motor spontaneous performance, increased the exploration in the aversive environment (anxiolytic-like effects), and elevated the latency to step-down (improved memory retention). The EO-enriched diet also reduced the level of lipid peroxidation in the hippocampus. These positive effects of EO-enriched diet can greatly support the usage of this diet as a preventive therapy. Conclusion: Taken together, the current study suggests that Euterpe oleracea-enriched diet promotes anxiolytic-like effects and improves memory consolidation, possibly due to the reduced levels of lipid peroxidation in the hippocampus.

Acute Restraint Stress Evokes Anxiety-Like Behavior Mediated by Telencephalic Inactivation and GabAergic Dysfunction in Zebrafish Brains.

Acute stress is an important factor in the development of anxiety disorders. Zebrafish are an organism model widely used by studies that aim to describe the events in the brain that control stress-elicited anxiety. The goal of the current study was to evaluate the pattern of cell activation in the telencephalon of adult zebrafish and the role of the GABAergic system on the modulation of anxiety-like behavior evoked by acute restraint stress. Zebrafish that underwent acute restraint stress presented decreased expression of the c-fos protein in their telencephalon as well as a significant decrease in GABA release. The data also supports that decreased GABA levels in zebrafish brains have diminished the activation of GABAA receptors eliciting anxiety-like behavior. Taken together these findings have helped clarify a neurochemical pathway controlling anxiety-like behavior evoked by acute stress in zebrafish while also opening the possibility of new perspective opportunities to use zebrafish as an animal model to test anxyolitic drugs that target the GABAergic system.

Oxidative Stress Mediates Anxiety-Like Behavior Induced by High Caffeine Intake in Zebrafish: Protective Effect of Alpha-Tocopherol.

Anxiety is a common symptom associated with high caffeine intake. Although the neurochemical mechanisms of caffeine-induced anxiety remain unclear, there are some evidences suggesting participation of oxidative stress. Based on these evidences, the current study is aimed at evaluating the possible protective effect of alpha-tocopherol (TPH) against anxiety-like behavior induced by caffeine (CAF) in zebrafish. Adult animals were treated with CAF (100 mg/kg) or TPH (1 mg/kg)+CAF before behavioral and biochemical evaluations. Oxidative stress in the zebrafish brain was evaluated by a lipid peroxidation assay, and anxiety-like behavior was monitored using light/dark preference and novel tank diving test. Caffeine treatment evoked significant elevation of brain MDA levels in the zebrafish brain, and TPH treatment prevented this increase. Caffeine treatment also induced anxiety-like behavior, while this effect was not observed in the TPH+CAF group. Taken together, the current study suggests that TPH treatment is able to inhibit oxidative stress and anxiety-like behavior evoked by caffeine.

Adenosine A1 receptors modulate the Na+-Hypertonicity induced glutamate release in hypothalamic glial cells.

Glutamate release in response to a hypertonic stimulus is a well described phenomenon in the hypothalamus. Evidence suggests that hypothalamic glial cells release glutamate into the extracellular environment in hypertonic conditions. In the current study, we described autocrine regulation of adenosine on glutamate release induced by Na+hypertonicity in hypothalamic glial cell cultures. We showed that glial cells cultured from the cerebral cortex did not release glutamate or adenosine under hypertonic conditions. The findings suggest that the hypothalamus has specialized glial cells, which are responsive to osmotic variations. Stimulation or inhibition of adenosine A1 receptors modulates extracellular glutamate levels in hypothalamic glial cell cultures under hypertonic stimulation. Our results extend previous observations regarding the role of glial cells in the control of hypothalamic physiology. They further demonstrate for the first time that hypothalamic glial cells regulate Na+-hypertonicity-induced glutamate release by activation of adenosine A1 receptors via adenosine release.

Ascorbic acid prevents chloroquine-induced toxicity in inner glial cells.

Ototoxicity is a collateral effect of prolonged treatment with chloroquine which is a widely utilized as an anti-lupus and anti-malarial drug. Glial cells of inner ear are responsible for maintenance of neuronal cells homeostasis in auditory system. In the current study we have evaluated chloroquine-induced toxicity and protective effect of ascorbic acid treatment on Schwann glial cell cultures of inner ear. Glial cells were cultured from organ of Corti of mice cochlear structure. Purity of Schwann glial cell was confirmed by S100 protein staining. Cell viability was evaluated in control and cultures treated with different concentrations of chloroquine. Glutamate uptake and ROS production were measured by HPLC and DCFH-DA probe fluorescence, respectively. Results have shown that chloroquine treatment evoked concentration and time -dependent toxicity (LC50 = 70 µM) as well as significant decrease on glutamate uptake and high production of ROS in glial cell cultures. Co-treatment with ascorbic acid has prevented both chloroquine-induced ROS production and chloroquine toxicity on glial cell cultures. This pre-clinical study is the first one to demonstrate chloroquine-induced ROS production by glial cells of inner ear as well as the protective effect exerted by ascorbic acid on these cells.