Hércules Ribeiro Leite

Differential brain and spinal cord cytokine and BDNF levels in experimental autoimmune encephalomyelitis are modulated by prior and regular exercise

The interactions between a prior program of regular exercise and the development of experimental autoimmune encephalomyelitis (EAE)-mediated responses were evaluated. In the exercised EAE mice, although there was no effect on infiltrated cells, the cytokine and derived neurotrophic factor (BDNF) levels were altered, and the clinical score was attenuated. Although, the cytokine levels were decreased in the brain and increased in the spinal cord, BDNF was elevated in both compartments with a tendency of lesser demyelization volume in the spinal cord of the exercised EAE group compared with the unexercised.

Swim training attenuates oxidative damage and promotes neuroprotection in cerebral cortical slices submitted to oxygen glucose deprivation.

Although it is well known that regular exercise may promote neuroprotection, the mechanisms underlying this effect are still not fully understood. We investigated if swim training promotes neuroprotection by potentiating antioxidant pathways, thereby decreasing the effects of oxidative stress on glutamate and nitric oxide release. Male Wistar rats (n=36) were evenly randomized into a trained group (TRA) (5 days/week, 8 weeks, 30 min) and a sedentary group (SED). Forty‐eight hours after the last session of exercise, animals were killed and brain was collected for in vitro ischemia. Cortical slices were divided into two groups: a group in which oxidative stress was induced by oxygen and glucose deprivation (OGD), and a group of non‐deprived controls (nOGD). Interestingly, exercise by itself increased superoxide dismutase activity (nOGD, SED vs. TRA animals) with no effect on pro‐oxidative markers. In fact, TRA‐OGD slices showed lowered levels of lactate dehydrogenase when compared with SED‐OGD controls, reinforcing the idea that exercise affords a neuroprotective effect. We also demonstrated that exercise decreased glutamate and nitrite release as well as lipid membrane damage in the OGD cortical slices. Our data suggest that under conditions of metabolic stress, swim training prevents oxidative damage caused by glutamate and nitric oxide release.

Differential effects of swimming training on neuronal calcium sensor-1 expression in rat hippocampus/cortex and in object recognition memory tasks.

Physical activity has been proposed as a behavioral intervention that improves learning and memory; nevertheless, the mechanisms underlying these health benefits are still not well understood. Neuronal Calcium Sensor-1 (NCS-1) is a member of a superfamily of proteins that respond to local Ca(2+) changes shown to have an important role in learning and memory. The aim of the present study was to investigate the effects of swimming training on NCS-1 levels in the rat brain after accessing cognitive performance. Wistar rats were randomly assigned to sedentary (SG) or exercised groups (EG). The EG was subject to forced swimming activity, 30 min/day, 5 days/week, during 8 weeks. Progressive load trials were performed in the first and last week in order to access the efficiency of the training. After the 8 week training protocol, memory performance was evaluated by the novel object preference and object location tasks. NCS-1 levels were measured in the cortex and hippocampus using immunoblotting. The EG performed statistically better for the spatial short-term memory (0.73 ± 0.01) when compared to the SG (0.63 ± 0.02; P<0.05). No statistically significant exercise-effect was observed in the novel object preference task (SG 0.65 ± 0.02 and EG 0.68 ± 0.02; p>0.05). In addition, chronic exercise promoted a significant increase in hippocampal NCS-1 levels (1.8 ± 0.1) when compared to SG (1.17 ± 0.08; P<0,05), but had no effect on cortical NCS-1 levels (SG 1.6 ± 0.1 and EG 1.5 ± 0.1; p>0.05). Results suggest that physical exercise would modulate the state of the neural network regarding its potential for plastic changes: physical exercise could be modulating NCS-1 in an activity dependent manner, for specific neural substrates, thus enhancing the cellular/neuronal capability for plastic changes in these areas; which, in turn, would differentially effect ORM task performance for object recognition and displacement.

Vesicular acetylcholine transporter knock down-mice are more susceptible to inflammation, c-Fos expression and sickness behavior induced by lipopolysaccharide

In addition to the well-known functions as a neurotransmitter, acetylcholine (ACh) can modulate of the immune system. Nonetheless, how endogenous ACh release inflammatory responses is still not clear. To address this question, we took advantage of an animal model with a decreased ACh release due a reduction (knockdown) in vesicular acetylcholine transporter (VAChT) expression (VAChT-KD(HOM)). These animals were challenged with lipopolysaccharide (LPS). Afterwards, we evaluated sickness behavior and quantified systemic and cerebral inflammation as well as neuronal activation in the dorsal vagal complex (DVC). VAChT-KD(HOM) mice that were injected with LPS (10mg/kg) showed increased mortality rate as compared to control mice. In line with this result, a low dose of LPS (0.1mg/kg) increased the levels of pro-inflammatory (TNF-α, IL-1β, and IL-6) and anti-inflammatory (IL-10) cytokines in the spleen and brain of VAChT-KD(HOM) mice in comparison with controls. Similarly, serum levels of TNF-α and IL-6 were increased in VAChT-KD(HOM) mice. This excessive cytokine production was completely prevented by administration of a nicotinic receptor agonist (0.4mg/kg) prior to the LPS injection. Three hours after the LPS injection, c-Fos expression increased in the DVC region of VAChT-KD(HOM) mice compared to controls. In addition, VAChT-KD(HOM) mice showed behavioral changes such as lowered locomotor and exploratory activity and reduced social interaction after the LPS challenge, when compared to control mice. Taken together, our results show that the decreased ability to release ACh exacerbates systemic and cerebral inflammation and promotes neural activation and behavioral changes induced by LPS. In conclusion, our findings support the notion that activity of cholinergic pathways, which can be modulated by VAChT expression, controls inflammatory and neural responses to LPS challenge.

Neuroprotective effect of exercise in rat hippocampal slices submitted to in vitro ischemia is promoted by decrease of glutamate release and pro-apoptotic markers.

The role of physical exercise as a neuroprotective agent against ischemic injury has been extensively discussed. Nevertheless, the mechanisms underlying the effects of physical exercise on cerebral ischemia remain poorly understood. Here, we investigate the hypothesis that physical exercise increases ischemic tolerance by decreasing the induction of cellular apoptosis and glutamate release. Rats (n = 50) were submitted to a swimming exercise protocol for 8 weeks. Hippocampal slices were then submitted to oxygen and glucose deprivation. Cellular viability, pro‐apoptotic markers (Caspase 8, Caspase 9, Caspase 3, and apoptosis‐inducing factor), and glutamate release were analyzed. The percentage of cell death, the amount of glutamate release, and the expression of the apoptotic markers were all decreased in the exercise group when compared to the sedentary group after oxygen and glucose deprivation. Our results suggest that physical exercise protects hippocampal slices from the effects of oxygen and glucose deprivation, probably by a mechanism involving both the decrease of glutamatergic excitotoxicity and apoptosis induction.

Pharmacological induction of ischemic tolerance in hippocampal slices by sarcosine preconditioning

Brain ischemic tolerance is a protective mechanism induced by a preconditioning stimulus, which prepare the tissue against harmful insults. Preconditioning with N-methyl-d-aspartate (NMDA) agonists induces brain tolerance and protects it against glutamate excitotoxicity. Recently, the glycine transporters type 1 (GlyT-1) have been shown to potentiate glutamate neurotransmission through NMDA receptors suggesting an alternative strategy to protect against glutamate excitotoxicity. Here, we evaluated the preconditioning effect of sarcosine pre-treatment, a GlyT-1 inhibitor, in rat hippocampal slices exposed to ischemic insult. Sarcosine (300 mg/kg per day, i.p.) was administered during seven consecutive days before induction of ischemia in hippocampus by oxygen/glucose deprivation (OGD). To access the damage caused by an ischemic insult, we evaluated cells viability, glutamate release, nitric oxide (NO) production, lactate dehydrogenase (LDH) levels, production of reactive oxygen species (ROS), and antioxidant enzymes as well as the impact of oxidative stress in the tissue. We observed that sarcosine reduced cell death in hippocampus submitted to OGD, which was confirmed by reduction on LDH levels in the supernatant. Cell death, glutamate release, LDH levels and NO production were reduced in sarcosine hippocampal slices submitted to OGD when compared to OGD controls (without sarcosine). ROS production was reduced in sarcosine hippocampal slices exposed to OGD, although no changes were found in antioxidant enzymes activities. This study demonstrates that preconditioning with sarcosine induces ischemic tolerance in rat hippocampal slices submitted to OGD.

Swimming training attenuates oxidative damage and increases enzymatic but not non-enzymatic antioxidant defenses in the rat brain

Although it is well known that physical training ameliorates brain oxidative function after injuries by enhancing the levels of neurotrophic factors and oxidative status, there is little evidence addressing the influence of exercise training itself on brain oxidative damage and data is conflicting. This study investigated the effect of well-established swimming training protocol on lipid peroxidation and components of antioxidant system in the rat brain. Male Wistar rats were randomized into trained (5 days/week, 8 weeks, 30 min; n=8) and non-trained (n=7) groups. Forty-eight hours after the last session of exercise, animals were euthanized and the brain was collected for oxidative stress analysis. Swimming training decreased thiobarbituric acid reactive substances (TBARS) levels (P<0.05) and increased the activity of the antioxidant enzyme superoxide dismutase (SOD) (P<0.05) with no effect on brain non-enzymatic total antioxidant capacity, estimated by FRAP (ferric-reducing antioxidant power) assay (P>0.05). Moreover, the swimming training promoted metabolic adaptations, such as increased maximal workload capacity (P<0.05) and maintenance of body weight. In this context, the reduced TBARS content and increased SOD antioxidant activity induced by 8 weeks of swimming training are key factors in promoting brain resistance. In conclusion, swimming training attenuated oxidative damage and increased enzymatic antioxidant but not non-enzymatic status in the rat brain.

High intensity interval training modulates hippocampal oxidative stress, BDNF and inflammatory mediators in rats

Although High Intensity Interval Training (HIIT) are being associated to increase cardiovascular and metabolic adaptation, there is controversy and limited information about the effects of HIIT on hippocampal oxidative stress, pro- and anti-inflammatory cytokines balance and neurotrophic status. Thus, this study evaluated the effects of six weeks of HIIT on hippocampal redox state (oxidative damage and enzymatic and non-enzymatic antioxidant defenses), neuroimmune mediators (TNFα, IL-6, IL-1β and IL-10) and brain-derived neurotrophic (BDNF) levels. After six weeks of HIIT young adults male Wistar rats presented reduced oxidative damage and increased enzymatic (superoxide dismutase) and non-enzymatic activity in hippocampus. Moreover HIIT induced a decrease in cytokine content (TNFα, IL-6, IL-1β and IL-10) and enhanced hippocampal BDNF levels. In conclusion, the present study showed for the first time a positive effect of six weeks of HIIT on reducing hippocampal oxidative stress by decreasing lipoperoxidation and inflammatory markers, as well enhancing antioxidant defenses and BDNF content.

Association between obesity-related biomarkers and cognitive and motor development in infants

Background This study aimed to verify the association between obesity‐related biomarkers and cognitive and motor development in infants between 6 and 24 months of age. Methods A cross‐sectional study was conducted with 50 infants and plasma levels of leptin, adiponectin, resistin, soluble tumor necrosis factor receptors 1 and 2 (sTNFR1 and sTNFR2), chemokines, brain‐derived neurotrophic factor (BDNF), serum cortisol and redox status were measured. The Bayley‐III test was utilized to evaluate cognitive and motor development, and multiple linear stepwise regression models were performed to verify the association between selected biomarkers and cognitive and motor development. Results A significant association was found among plasma leptin and sTNFR1 levels with cognitive composite scores, and these two independents variables together explained 37% of the variability of cognitive composite scores (p = 0.001). Only plasma sTNFR1 levels were associated and explained 24% of the variability of motor composite scores (p = 0.003). Conclusions Plasma levels of sTNFR1 were associated with the increase in cognitive and motor development scores in infants between 6 and 24 months of age through a mechanism not directly related to excess body weight. Moreover, increase in plasma levels of leptin reduced the cognitive development in this age range.

Neuroendocrine Inflammatory Responses in Overweight/Obese Infants.

Childhood obesity is related to a cascade of neuroendocrine inflammatory changes. However, there remains a gap in the current literature regarding the possible occurrence of these changes in overweight/obese infants. The objective of this study was to evaluate adipokines, cortisol, brain-derived neurotrophic factor (BDNF) and redox status in overweight/obese infants versus normal-weight peers. A cross-sectional study was conducted with 50 infants (25 in the overweight/obese group and 25 in the normal-weight group) between 6 and 24 months. Plasma levels of leptin, adiponectin, resistin, soluble tumor necrosis factor (TNF) receptors, chemokines, BDNF, serum cortisol and redox status were measured. Unpaired Students t-test was used to analyze the results and a probability of p<0.05 was acceptable for rejection of the null hypothesis. The Pearson correlation was used to verify the association between the biomarkers analyzed in each group. Plasma levels of leptin (p = 0.0001), adiponectin (p = 0.0007) and BDNF (p = 0.003), and serum cortisol (p = 0.048) were significantly higher in overweight/obese infants than normal-weight infants. In contrast, the concentration of thiobarbituric acid reactive substances (TBARS) (p = 0.004), and catalase (p = 0.045) and superoxide dismutase activity (p = 0.02) were lower in overweight/obese infants than normal-weight peers. All the results together indicate neuroendocrine inflammatory response changes in overweight/obese infants between 6 and 24 months. Although there is already an environment that predisposes for a subsequent pro-inflammatory response, neuroendocrine secretion changes that permit the control of the inflammatory process in this age interval can be observed.