Jean Pierre Oses

Unpredictable chronic stress model in zebrafish (Danio rerio): Behavioral and physiological responses

Zebrafish (Danio rerio) have emerged as a promising model organism to study development, toxicology, pharmacology, and neuroscience, among other areas. Despite the increasing number of studies using zebrafish, behavioral studies with this species are still elementary when compared to rodents. The aim of this study was to develop a model of unpredictable chronic stress (UCS) in zebrafish. We evaluated the effects of UCS protocol during 7 or 14 days on behavioral and physiological parameters. The effects of stress were evaluated in relation to anxiety and exploratory behavior, memory, expression of corticotrophin-releasing factor (CRF) and glucocorticoid receptor (GR), and cortisol levels. As expected, UCS protocol increased the anxiety levels, impaired cognitive function, and increased CRF while decreased GR expression. Moreover, zebrafish submitted to 7 or 14 days of UCS protocol presented increased cortisol levels. The protocol developed here is a complementary model for studying the neurobiology and the effects of chronic stress in behavioral and physiological parameters. In addition, this protocol is less time consuming than standard rodent models commonly used to study chronic stress. These results confirm UCS in zebrafish as an adequate model to preclinical studies of stress, although further studies are warranted to determine its predictive validity.

Neuron-Specific Enolase, S100B, and Glial Fibrillary Acidic Protein Levels as Outcome Predictors in Patients With Severe Traumatic Brain Injury

BACKGROUND:The availability of markers able to provide an early insight related to prognostic and functional outcome of patients with traumatic brain injury (TBI) are limited. OBJECTIVE:The relationship of clinical outcome with CSF neuron-specific enolase (NSE), S100B and glial fibrillary acidic protein (GFAP) levels in patients with severe TBI was investigated. METHODS:Twenty patients with severe TBI (7 days at unit care) and controls were studied. Patients were grouped according to the outcome: (1) nonsurvival (n = 5): patients who died; (2) survival A (n = 15): CSF sampled between 1st and 3rd day from patients who survived after hospital admission; and (3) survival B (n = 7): CSF sampled between 4th and 7th day from patients who survived after hospital admission and were maintained with intraventricular catheter up to 7 days. RESULTS:Up to 3 days, S100B and NSE levels (ng/mL) were significantly elevated in the nonsurvival compared with survival A group (S100: 12.45 ± 5.46 vs 5.64 ± 3.36; NSE: 313.20 ± 45.51 vs 107.80 ± 112.10). GFAP levels did not differ between groups. In the survival B group S100B, GFAP, and NSE levels were still elevated compared with control (4.59 ± 2.19, 2.48 ± 2.55, and 89.80 ± 131.10, respectively). To compare S100B and NSE for the prediction of nonsurvival and survival patients we performed receiver operating characteristic curves. At admission, CSF NSE level predicts brain death more accurately than S100B. CONCLUSION:Early elevations (up to 3 days) of S100B and NSE secondary to severe TBI predict deterioration to brain death. However, this feature was more prominently associated with NSE than S100B.

The role of CRH in behavioral responses to acute restraint stress in zebrafish.

In teleosts, changes in swimming, exploring, general locomotor activity, and anxious state can be a response to stress mediated by the corticotropin-releasing hormone system activation and its effects on glucocorticoid levels. Zebrafish has been widely used to study neuropharmacology and has become a promising animal model to investigate neurobehavioral mechanisms of stress. In this report the animals were submitted to acute restraint stress for different time lengths (15, 60 and 90 min) for further evaluation of behavioral patterns, whole-body cortisol content, and corticotropin-releasing hormone expression. The results demonstrated an increase in the locomotor activity and an alteration in the swimming pattern during a 5-min trial after the acute restraint stress. Interestingly, all groups of fish tested in the novel tank test exhibited signs of anxiety as evaluated by the time spent in the bottom of the tank. Whole-body cortisol content showed a positive correlation with increased behavioral indices of locomotion in zebrafish whereas molecular analysis of corticotropin-releasing hormone showed a late reduction of mRNA expression (90 min). Altogether, we present a model of acute restraint stress in zebrafish, confirmed by elevated cortisol content, as a valid and reliable model to study the biochemical basis of stress behavior, which seems to be accompanied by a negative feedback of corticotropin-release hormone mRNA expression.

Biochemical brain markers and purinergic parameters in rat CSF after seizure induced by pentylenetetrazol

Cellular and molecular mechanisms involved in the generation of seizures and the magnitude of neural cells injury are not fully understood. We evaluated astrocyte and/or neuronal injury in rats in the pentylenetetrazol model of acute seizures by measuring S100B and NSE levels in cerebrospinal fluid. Additionally, we determined ADP and GDP hydrolysis by soluble nucleoside triphosphate diphosphohydrolase in the cerebrospinal fluid, and the concentration of nucleosides adenosine, inosine and guanosine as putative markers of brain injury. After pentylenetetrazol-induced seizures: (i) S100B values increased from 10 to 30 min, returning to control levels at 24 h; NSE levels presented a biphasic increase: an increase at 10 to 30 min returning to control levels, and again at 240 min followed by a decline at 24 h; (ii) nucleotidase activities increased from 10 min, returning to control levels at 240 min; (iii) guanosine and inosine levels increased exclusively after 30 min. In summary, this study showed biochemical changes in the cerebrospinal fluid occurring after seizures induced by pentylenetetrazol. Such events may have a modulating effect upon seizure expression, particularly nucleoside triphosphate diphosphohydrolase activities and nucleoside concentrations, but are nevertheless followed by neural death as evidenced by the increase in NSE and S100B levels.

Guanine and adenine nucleotidase activities in rat cerebrospinal fluid

Adenine and guanine nucleotides have been shown to exert multiple roles in central and peripheral nervous systems, and the sequential breakdown of these nucleotides by enzymatic systems is an important step in the modulation of their extracellular effects. The aim of this study was to investigate whether nucleotide hydrolysis also occurs in the cerebrospinal fluid (CSF) of rats. CSF was able to hydrolyze all guanine and adenine nucleotides investigated (2.0 mM): GDPz.Gt;ADP=ATP=GTPz.Gt;AMP=GMP. More detailed studies with the diphosphate nucleotides showed that the hydrolysis of ADP and GDP was linear with incubation time and protein concentration. The apparent K(M) (Henry-Michaelis-Menten constant) and V (maximal velocity) values for ADP and GDP were 164.3+/-54.7 microM and 12.2+/-3.8 nmol P(i)/min per mg protein, and 841.0+/-90.2 microM and 22.8+/-8.0 nmol P(i)/min per mg protein. The sum of ADP, GDP and UDP hydrolysis (2.0 mM) upon individual incubations with CSF was similar to the hydrolysis observed when all three nucleotides were incubated together. This pattern of hydrolysis strongly suggests the involvement of more than one enzyme activity. The higher maximum activity for GDP and UDP compared to ADP is compatible with presence of a soluble NTDPase5.

Immune dysfunction in bipolar disorder and suicide risk: is there an association between peripheral corticotropin‐releasing hormone and interleukin‐1β?

OBJECTIVE The aim of the present study was to investigate the relationship between peripheral levels of corticotropin-releasing hormone (CRH) and interleukin-1β (IL-1β) in individuals with bipolar disorder (BD) with and without suicide risk (SR), and controls. METHODS A total of 120 young adults (40 controls, 40 subjects with BD without SR, and 40 subjects with BD with SR) were enrolled from a population-based study carried out in the city of Pelotas, Brazil. BD and SR were assessed through the Mini International Neuropsychiatric Interview (MINI 5.0), and peripheral markers were evaluated by enzyme-linked immunosorbent assay (ELISA). RESULTS Levels of CRH were significantly lower both in subjects with BD without SR (p = 0.04) and subjects with BD with SR (p = 0.02) when compared to controls. However, levels of IL-1β were increased in subjects with BD with SR (p = 0.05) when compared to controls. Sociodemographic and clinical variables, current mood episode, and use of psychiatric medications were not associated with changes in these markers. No correlation was found between peripheral levels of CRH and IL-1β (p = 0.60) in the population or in the BD with SR group (p = 0.88). CONCLUSIONS These results suggest that peripheral mechanisms linking stress hormones and the immune system might be critical patterns involved in suicidal behavior associated with BD.

Dietary omega-3 fatty acids attenuate cellular damage after a hippocampal ischemic insult in adult rats ☆

The role of omega-3 polyunsaturated fatty acids (3PUFAs) on brain function is increasingly demonstrated. Here, the effect of dietary deprivation of essential 3PUFAs on some parameters related to neuroprotection was investigated. Rats were fed with two different diets: omega-3 diet and omega-3-deprived diet. To assess the influence of 3PUFAs on brain responses to ischemic insult, hippocampal slices were subjected to an oxygen and glucose deprivation (OGD) model of in vitro ischemia. The omega-3-deprived group showed higher cell damage and stronger decrease in the [(3)H]glutamate uptake after OGD. Moreover, omega-3 deprivation influenced antiapoptotic cell response after OGD, affecting GSK-3beta and ERK1/2, but not Akt, phosphorylation. Taken together, these results suggest that 3PUFAs are important for cell protection after ischemia and also seem to play an important role in the activation of antiapoptotic signaling pathways.

Increase of nucleotidase activities in rat blood serum after a single convulsive injection of pentylenetetrazol

Adenosine has been shown to be a major regulator in convulsive disorders exerting its anticonvulsant effects on various seizure models. The ectonucleotidase pathway is an important metabolic source of extracellular adenosine. In this study, we evaluated ATP, ADP and AMP hydrolysis in rat serum after a single convulsive injection of pentylenetetrazol (PTZ). The animals were sacrificed at 5 and 30 min, 1, 5, 12, 24 and 48 h after an intraperitoneal injection of PTZ (60 mg/kg). ATP, ADP and AMP hydrolysis by rat blood serum were significantly increased (40-50%) until 24 h after PTZ injection. There were no significant differences in the nucleotide hydrolysis when the in vitro effect of different concentrations of PTZ was analyzed. Changes in nucleotide hydrolysis observed after acute administration of PTZ could not be attributed to phosphodiesterase activity since PTZ-treated rats did not demonstrate significant differences in the hydrolysis of the substrate marker of this enzyme when compared with control rats. These results suggest that the stimulation of the nucleotidase pathway may play an important role in attenuating seizure activity.

Childhood trauma and suicide risk in a sample of young individuals aged 14-35 years in southern Brazil

Suicide is among the main causes of death of people aged between 15 and 44 years old. Childhood trauma is an important risk factor for suicide. Hence, the objective of this study was to verify the relationship between childhood trauma and current suicide risk (suicidal behavior and ideation) in individuals aged 14-35 years, in the city of Pelotas, Brazil. This is a cross-sectional, population-based study. Sample selection was performed by clusters. Suicide risk was evaluated using the Mini International Neuropsychiatric Interview (MINI) and Childhood trauma was assessed with the Childhood Trauma Questionnaire (CTQ). Moreover, the participants responded to a questionnaire concerning socioeconomic status, work, and substance use. The sample was composed of 1,380 individuals. The prevalence of suicide risk was 11.5%. The prevalence figures of childhood trauma were 15.2% (emotional neglect), 13.5% (physical neglect), 7.6% (sexual abuse), 10.1% (physical abuse), and 13.8% (emotional abuse). Suicide risk was associated (p<.001) with gender, work, alcohol abuse, tobacco use, and all types of childhood trauma. The odds of suicide risk were higher in women (OR=1.8), people who were not currently working (OR=2.3), individuals who presented alcohol abuse (OR=2.6), and among tobacco smokers (OR=3.4). Moreover, suicide risk was increased in all types of trauma: emotional neglect (OR=3.7), physical neglect (OR=2.8), sexual abuse (OR=3.4), physical abuse (OR=3.1), and emotional abuse (OR=6.6). Thus, preventing early trauma may reduce suicide risk in young individuals.

Dietary omega-3 deficiency reduces BDNF content and activation NMDA receptor and Fyn in dorsal hippocampus: Implications on persistence of long-term memory in rats

Abstract Omega-3 (n-3) fatty acids are important for adequate brain function and cognition. The aim of the present study was to evaluate how n-3 fatty acids influence the persistence of long-term memory (LTM) in an aversive memory task and to explore the putative mechanism involved. Female rats received isocaloric diets that included n-3 (n-3 group) or not (D group). The adult litters were subjected to an inhibitory avoidance task (0.7 mA, 1.0 seconds foot shock) to elicit persistent LTM. Twelve hours after the training session, the fatty acid profile and the brain derived neurotrophic factor (BDNF) content of the dorsal hippocampus were assessed. In addition, we measured the activation of the NR2B subunit of the N-methyl-d-aspartate (NMDA) receptor and the SRC family protein Fyn. Despite pronounced learning in both groups, the persistence of LTM was abolished in the D group 7 days after the training session. We also observed that the D group presented reductions in hippocampal DHA (22:6 n-3) and BDNF content. Twelve hours after the training session, the D group showed decreased NR2B and Fyn phosphorylation in the dorsal hippocampus, with no change in the total content of these proteins. Further, there was a decrease in the interaction of Fyn with NR2B in the D group, as observed by co-immunoprecipitation. Taken together, these data suggest that n-3 fatty acids influence the persistence of LTM by maintaining adequate levels of DHA and BDNF as well as by influencing the activation of NR2B and Fyn during the period of memory formation.