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.

COCHLEAR GLIAL CELLS MEDIATES GLUTAMATE UPTAKE THROUGH A SODIUM-INDEPENDENT TRANSPORTER

Since glutamate is the primary excitatory neurotransmitter in the mammalian cochlea, the mechanisms for the removal of glutamate from the synaptic and extrasynaptic spaces are critical for maintaining normal function of this region. Glial cells of inner ear are crucial for regulation of synaptic transmission throughout since it closely interacts with neurons along the entire auditory pathway, however little is known about the activity and expression of glutamate transporters in the cochlea. In this study, using primary cochlear glial cells cultures obtained from newborn Balb/C mice, we determined the activity of a sodium-dependent and sodium-independent glutamate uptake mechanisms by means of High Performance Liquid Chromatography. The sodium-independent glutamate transport has a prominent contribution in cochlear glial cells which is similar to what has been demonstrated in other sensory organs, but it is not found in tissues less susceptible to continuous glutamate-mediated injuries. Our results showed that x_CG^- system is expressed in CGCs and is the main responsible for sodium-independent glutamate uptake. The identification and characterization of the x_CG^- transporter in the cochlea suggests a possible role of this transporter in the control of extracellular glutamate concentrations and regulation of redox state, that may aid in the preservation of auditory function.

Euterpe oleracea fruit (Açai)-enriched diet suppresses the development of experimental cerebral malaria induced by Plasmodium berghei (ANKA) infection

Background

Cerebral malaria is one of the most severe complications attributed to protozoal infection by Plasmodium falciparum, gaining prominence in children mortality rates in endemic areas. This condition has a complex pathogenesis associated with behavioral, cognitive and motor sequels in humans and current antimalarial therapies have shown little effect in those aspects. Natural products with antioxidant and anti-inflammatory properties have become a valuable alternative therapeutic option in the treatment of distinct conditions. In this context, this study investigated the neuroprotective effect of Euterpe oleracea (açai) enriched diet during the development of experimental cerebral malaria induced by the inoculation of Swiss albino mice with Plasmodium berghei ANKA strain.

Methods

After Plasmodium infection, animals were maintained on a feeding with Euterpe oleracea enriched ration and parameters such as survival curve, parasitemia and body weight were routinely monitored. The present study has also evaluated the effect of açai-enriched diet on the blood-brain barrier leakage, histological alterations and neurocognitive impairments in mice developing cerebral malaria.

Results

Our results demonstrate that between 7th–19th day post infection the survival rate of the group treated with açai enriched ration was higher when compared with Plasmodium-infected mice in which 100% of mice died until the 11th days post-infection, demonstrating that açai diet has a protective effect on the survival of infected treated animals. The same was observed in the brain vascular extravasation, where Evans blue dye assays showed significantly less dye extravasation in the brains of Plasmodium-infected mice treated with açai enriched ration, demonstrating more preserved blood-brain barrier integrity. Açai-enriched diet also attenuate the histopathological alterations elicited by Plasmodium berghei infection. We also showed a decrease of the neurological impairments arising from the exposure of cerebral parenchyma in the group treated with açai diet, ameliorating motor and neuropsychiatric changes, analyzed through the SHIRPA protocol.

Conclusion

With these results, we conclude that the treatment with açai enriched ration decreased the mortality of infected animals, as well as protected the blood-brain barrier and the neurocognitive deficits in Plasmodium-infected animals.

Melatonin Prevents Brain Damage and Neurocognitive Impairment Induced by Plasmodium Berghei ANKA Infection in Murine Model of Cerebral Malaria

Cerebral malaria is characterized by permanent cognitive impairments in Plasmodium-infected children. Antimalarial therapies show little effectiveness to avoid neurological deficits and brain tissue alterations elicited by severe malaria. Melatonin is a well-recognized endogenous hormone involved in the control of brain functions and maintenance of blood–brain barrier integrity. The current study has evaluated the effect of melatonin on the histological alterations, blood–brain barrier leakage, and neurocognitive impairments in mice developing cerebral malaria. Swiss mice infected with Plasmodium berghei ANKA strain was used as cerebral malaria model. Melatonin treatment (5 and 10 mg/kg) was performed for four consecutive days after the infection, and data have shown an increased survival rate in infected mice treated with melatonin. It was also observed that melatonin treatment blocked brain edema and prevented the breakdown of blood–brain barrier induced by the Plasmodium infection. Furthermore, hematoxylin and eosin staining revealed that melatonin mitigates the histological alterations in Plasmodium-infected animals. Melatonin was also able to prevent motor and cognitive impairments in infected mice. Taken together, these results show for the first time that melatonin treatment prevents histological brain damages and neurocognitive alterations induced by cerebral malaria.

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.

Local treatment with ascorbic acid accelerates recovery of post-sutured Achilles tendon in male Wistar rats

Tendon rupture is a very frequent accident involving average people and high-performance athletes. Clinical studies describe tendon recovery as a painful and slow process involving different biochemical and histological events. Ascorbic acid (AA) is a potent antioxidant as well as an important cofactor for collagen synthesis. In the current study, we evaluated if local treatment with AA is able to promote tendon repair in tenotomized rats. Animals were submitted to Achilles tendon rupture followed by surgical suture. Control and AA groups received in loco injection of saline solution (0.9% NaCl) and 30 mM AA, respectively. Histological and functional recovery of Achilles tendon tissue was evaluated at 7, 14, and 21 days post-surgery. Hematoxylin/eosin staining and collagen fluorescence analysis showed intense disarrangement of tendon tissue in the saline group. Tenotomized animals also showed hypercellularity in tendon tissue compared with non-tenotomized animals. The Achilles functional index (AFI) showed a significant decrease of tendon functionality in tenotomized animals at 7, 14, and 21 days post-surgery. AA accelerated tissue organization and the recovery of function of the Achilles tendons. The beneficial effect of AA treatment was also observed in the organization of the collagen network. Data presented in the current work showed that in loco treatment with AA accelerated the recovery of injured Achilles tendon post-surgery.

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.

Interaction between 5-HT1B receptors and nitric oxide in zebrafish responses to novelty

Nitric oxide (NO) and serotonin (5-HT) interact at the molecular and systems levels to control behavioral variables, including agression, fear, and reactions to novelty. In zebrafish, the 5-HT1B receptor has been implicated in anxiety and reactions to novelty, while the 5-HT1A receptor is associated with anxiety-like behavior; this role of the 5-HT1A receptor is mediated by NO. This work investigated whether NO also participates in the mediation of novelty responses by the 5-HT1B receptor. The 5-HT1B receptor inverse agonist SB 224,289 decreased bottom-dwelling and erratic swimming in zebrafish; the effects on bottom-dwelling, but not on erratic swimming, were blocked by pre-treatment with the nitric oxide synthase inhibitor L-NAME. These effects underline a novel mechanism by which 5-HT controls zebrafish reactivity to novel environments, with implications for the study of neotic reactions, exploratory behavior, and anxiety-like states.