肌肽对皮质下缺血性血管性痴呆小鼠海马损伤的防护作用

Protective effect of carnosine on hippocampus injury induced by subcorticai ischemic vascular dementia in mice

目的 探讨肌肽对皮质下缺血性血管性痴呆（SIVD）小鼠海马损伤的防护作用.方法 将40只雄性C57B L/6小鼠完全随机分为假手术组、模型组、肌肽低剂量组、肌肽中剂量组、肌肽高剂量组（每组8只）.模型组小鼠给予永久性结扎单侧颈总动脉（rUCCAO）并腹腔注射0.9％氯化钠注射液（手术前30 min开始给药,隔天1次）;肌肽低剂量组、肌肽中剂量组和肌肽高剂量组小鼠分别给予rUCCAO并腹腔注射肌肽200、500及750 mg/kg（手术前30 min开始给药,隔天1次）;假手术组不予rUCCAO.术后34～37 d采用水迷宫实验检测小鼠行为学指标,术后37 d采用劳克坚牢蓝染色检测小鼠海马部位白质损伤情况、采用甲苯胺蓝染色观察小鼠海马神经元的改变、采用免疫荧光染色检测小鼠大脑海马部位星型胶质细胞标记物胶质细胞原纤维酸性蛋白（GFAP）的表达.结果 水迷宫实验第1～3天学习记忆获得训练中,模型组小鼠寻找平台潜伏期较假手术组明显延长;肌肽低剂量组第2天和第3天寻找平台潜伏期明显短于模型组,第3天肌肽中剂量组寻找平台潜伏期明显短于模型组,差异有统计学意义（P＜0.01或P＜0.05）,肌肽高剂量组第1～3天寻找平台潜伏期与模型组比较差异均无统计学意义（P＞0.05）.与假手术组比较,模型组白质劳克坚牢蓝染色明显变浅,与模型组比较肌肽低剂量组和肌肽高剂量组白质劳克坚牢蓝染色变深;与假手术组比较,海马部位白质纤维密度模型组下降至（70±8）％,肌肽低剂量组和肌肽中剂量组明显高于模型组[（92±8）％、（85±8）％]（P＜0.05）,肌肽高剂量组与模型组比较差异无统计学意义（P＞0.05）.4组小鼠海马部位神经元细胞密度差异无统计学意义（P＞0.05）.与假手术组比较,模型组星形胶质细胞GFAP免疫荧光强度增加至（259±58）％,肌肽低剂量组和肌肽中剂量组[（157±19）％和（175±43）％]则明显低于模型组（P＜0.01）,肌肽高剂量组与模型组比较差异无统计学意义（P＞0.05）.结论 肌肽对SIVD小鼠大脑海马部位白质损伤及学习记忆下降具有防护作用,其机制可能与抑制海马部位星形胶质细胞的激活有关.

Objective To explore protective effect of carnosine on hippocampus injury induced by subcortical ischemic vascular dementia （SIVD） in mouse.Methods Totally 40 C57BL/6 mice were were randomly divided into sham group,model group,carnosine low dose group,carnosine middle dose group and carnosine high dose group （n =8 in each group）.Occlusion of the right unilateral common carotid arteries （rUCCAO） and intraperitoneal injection of 0.9% sodium chloride （started 30 min before operation,1 time every other day） were given in model group;rUCCAO and intraperitoneal injection of carnosine （200,500 and 750 mg/kg,started 30 min before operation,1 time every other day） were given in carnosine low,middle and high dose group;rUCCAO was not given in sham group.Water maze model was used to detect the mice behavior;Klüver-Barrera staining,toluidine blue staining and immunohistochemical analyse was respectively used to detect the white matter damage,neurons changes and glial fibrillary acidic protein （GFAP） in astrocyte cells.Results In water maze model,the mice in model group had much longer incubation time of seeking the platform on the first to third day of learning and memory training compared with sham group;while the time in carnosine low dose group on the second and the third day and in carnosine middle dose group on the third day was significantly shorter than that in model group （P 〈 0.01 or P 〈 0.05）;it was not significantly different between model group and carnosine high dose group （P 〉 0.05）.The Klüver-Barrera staining of white matter in model group was significantly lighter than that in sham group,while was deepened in carnosine low and middle dose group compared with model group;the density of white matter fibers was decreased to （70 ± 8）% compared with sham group,and was significantly higher in carnosine low and middle dose group [（92 ±8）%,（85 ±8）%] （P 〈0.05）,was not significantly different in carnosine high dose group compared with that in model group （P 〉 0.05）.The neurons number was not significantly different among groups （P 〉 0.05）.The Fluorescence intensity of GFAP was increased to （259 ±58）% in model group compare with sham group,and was significantly higher in cannosine low and middle dose group [（157 ± 19） %,（175 ± 43） %] （P 〈 0.05）,was not significantly different in carnosine high dose group compared with that in model group （P 〉 0.05）.Conclusion Carnosine has neuroprotective effect on the damaged white matter and decreased learning and memory iu SIVD mice,and the mechanism may be related with suppression of glia activation.