Efeitos do tratamento com chá verde (camellia sinensis) no dano oxidativo e déficit de memória induzido pelo acidente vascular cerebral (AVC) isquêmico e pelo AVC hemorrágico em ratos

Abstract

The stroke is classified in two types: Ischemic and Hemorrhagic. Among the consequences resulting from the stroke there are the functional changes, cognitive deficit and memory impairment. Furthermore, it is known that in a situation such as stroke is followed by disbalance of the redox state and, as a final result, neuronal damage. Currently, interventions to promote neuroprotection through natural compounds that may interfere in biochemical mechanisms aiming the reduction of damage are sought. The aim of this study was to investigate the effect of supplementation with green tea (Camellia sinensis) on oxidative damage and object recognition memory (OR) deficit induced by two experimental models of stroke: ischemic (ischemia-reperfusion, IR) and hemorrhagic (intracerebral hemorrhage, ICH), in rats. To this, 80 Wistar male rats divided into 8 groups according the stroke type induced were used (n=10/group): Sham IR, Sham IR and green tea, IR, IR and green tea, Sham ICH, Sham ICH and green tea, ICH, ICH and green tea. Supplementation with green tea was initiated 10 days before the stroke surgery and continued for 7 days after in a dose of 400 mg/kg per day. After all, the rats were subjected to object recognition task (OR) to assess short (STM) and long term memory (LTM). Additionally, hippocampus were used to measure parameters related to oxidative stress by determining the reactive species of oxygen levels (ROS), detection of reactive substances to thiobarbituric acid (TBARS) and the evaluation of the antioxidant capacity by the method of electron transfer determination - FRAP. OR results were analyses using one-sample t-test (theoretical mean 50%) and biochemical parameters using Student's t-test or one-way ANOVA followed by Dunn’s post hoc. Both types of stroke caused STM and LTM in OR test, so, the animals did not recognize the new object after stroke. On the other hand, animals that received green tea previous to stroke, and the animals of the sham group, spent significantly more than 50% of the total exploration time exploring the new object. The two types of stroke induced an increase in the levels of ROS, hemorrhagic stroke caused hippocampal lipid peroxidation and ischemic stroke caused the decrease of the total antioxidant capacity, which is related to the consequent mnemonic deficits observed. Supplementation with green tea showed neuroprotective effect and prevent cell damage caused by stroke models; the green tea was effective in preventing the increase of ROS in both models, and lipid peroxidation in hemorrhagic stroke group, besides keeping the total antioxidant capacity in both. These results show that stroke causes short and long term memory deficits and hippocampal oxidative damage, and that the green tea suplementation can protect against such damage. Keywords: memory, oxidative stress, green tea, neuroprotection, stroke