ABSTRACT
Objective To investigate the effect of theanine pretreatment on DNA repair function in neurons during brain ischemia-reperfusion (I/R) injury in rats.Methods One hundred and eight male Sprague-Dawley rats,weighing 290-310 g,aged 15 weeks,were randomly divided into 3 groups (n =36 each) using a random number table:sham operation group (S group),I/R group and theanine pretreatment group (T group).Global cerebral I/R was produced by 4-vessel occlusion method.Bilateral vertebral arteries were electrically cauterized,and bilateral common carotid arteries were clamped for 6 min.Theanine 1 g/kg was injected intravenously at 4 h before clamping bilateral common carotid arteries in T group,and the equal volume of normal saline was given in the other two groups.At 2,6,12,24,48 and 72 h of reperfusion,6 rats were selected in each group and sacrificed,the brains were removed,and the hippocampus was isolated for determination of the number of viable neurons in the hippocampal CA1 region (with a light microscope),apoptosis in neurons in the hippocampal CA1 region (by TUNEL),and expression of DNA repair protein X-ray repair cross-complementing group 1 (XRCC1) and Ku70 (by immunohistochemistry).The apoptotic index was calculated.Results Compared with S group,the number of viable neurons was significantly decreased,and the apoptotic index was significantly increased at 6,12,24,48 and 72 h of reperfusion,and the expression of XRCC1 and Ku70 was significantly down-regulated at 2,6,12,24,48 and 72 h of reperfusion in I/R group (P＜0.01).Compared with I/R group,the number of viable neurons was significantly increased at 12,24,48 and 72 h of reperfusion,the apoptotic index was significantly decreased at 6,12,24,48 and 72 h of reperfusion,and the expression of XRCC1 and Ku70 was significantly up-regulated at 2,6,12,24,48 and 72 h of reperfusion in T group (P ＜ 0.01).Conclusion The mechanism by which theanine pretreatment attenuates brain I/R injury is related to enhancement of DNA repair function and reduction of neuronal apoptosis in rats.