Effect of theanine pretreatment on DNA repair function in neurons during brain ischemia-reperfusion injury in rats

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. Key words: Tea; Glutamates; Brain; Reperfusion injury; DNA Repair; Apoptosis; Neurons