Participação das vias de estresse oxidativo na neuroproteção mediada pelo treinamento físico em fatias cerebrais submetidas à privação de oxigênio e glicose

Abstract

Ischemia leads to a variety of pathological events, including excitotoxicity, inflammation, delayed neuronal dysfunction and cell death through hyperactivation of glutamate receptors and production of free radicals, such as nitric oxide (NO). The mechanism by which cerebral excess formation of NO, which mediates neuronal death involving energy depletion, lipid peroxidation and protein nitrosylation of proteins and DNA damage have not been fully elucidated. In this context, there is evidence supporting the fact that regular exercise has beneficial effects on the brain, which activate cellular and molecular pathways that contribute to neuroprotection. Thus, the purpose of this study was to evaluate the role played by oxidative stress pathways in neuroprotection induced by exercise in brain slices submitted to oxygen and glucose deprivation (OGD). Male Wistar rats were divided into two groups: trained (TRA) and sedentary groups (SED). The TRA group was submitted to a swimming protocol 5x/week, 30 min/day for 8 weeks, with moderate training intensity (60% of maximum load). At the end of training protocol animals were decapitated and cerebral cortices and hippocampus were quickly removed and sliced (thickness 400 m). The slices of the same animal were then randomized into: (1) SED and TRE control slices not submitted to oxygen glucose deprivation (SED nOGD; nOGD TRE), and (2) submitted to oxygen glucose deprivation for 60 min (OGD SED; OGD TRE). Thereafter, both groups were submitted to 4-hours without OGD. Then, tissues and medium incubation were collected and stored at 80 ºC. The following parameters were evaluated: cell viability (lactate dehydrogenase/LDH, and homodimer-ethídium/EthD-1), glutamate, nitrite ([NO2-]), superoxide dismutase activity (SOD) and lipid peroxidation (thiobarbituric acid reactive substances/TBARS). In addition, parameters associated to physical training, such as muscle and liver glycogen, and the maximum load in the maximal effort test (MET), were also evaluated. For statistical analysis we used one-way and two-way ANOVA. The results were expressed as standard error mean (± S.E.M) with significance of p<0.05. It was observed that exercise training increased hepatic and muscle glycogen storage, and improves performance in MET. There was a reduction in the number of cell death in cortical slices from TRA OGD group (92.64 ± 19.18), and hippocampal TRA OGD (183.4 ± 46.84) and lower levels of glutamate in TRA OGD (2.26 ± 0.31), only in hippocampus. NO2- and TBARS concentration decreased only in cortical TRA OGD (1.0 ± 0.28) and (69.03 ± 10.16), respectively. Moreover, exercise, per se, increased cortical nPOG SOD activity (0.10 ± 0.22). The results suggest that, exercise training is able to induce neuroprotection in cerebral cortex and hippocampus submitted to OGD, decreasing the levels of NO2- and lipoperoxidation, besides increasing the SOD activity in these slices, and lower glutamatergic excitotoxicity in hippocampal OGD TRA slices.