Abstract:

Objective To explore the neuroprotective effect of remote ischemic conditioning (RIC) and the corresponding mechanism in rats with vascular cognitive impairment (VCI) due to cerebral ischemia-reperfusion injury. Methods Male Sprague-Dawley rats were selected and randomly assigned to sham operation group (sham group), control group (VCI group) and RIC group (VCI+RIC group). The VCI animal models were established by bilateral common carotid arteries occlusion (BCCAO) method. The RIC was initiated after 24 hours of establishing the VCI models and lasted for 21 days only in RIC group. After the completion of RIC, the Morris water maze test was performed for place navigation test and space probe test in the three groups. In navigation test, the rats received 5 daily swim trials, the escape latency of rats were recorded on day 1, 3 and 5, and the platform stay time and the times of crossing platform of rats on day 6 were recorded to evaluate their cognitive function. After completing the whole procedure, 5 rats in each group were randomly selected to take brain tissue for HE staining. The pathological changes of brain white matter and hippocampus and neuron apoptosis were observed under the electron microscope. Results The Morris water maze test results showed that the escape latency of control group and RIC group were prolonged compared with sham group on day 1, 3, and 5 (P <0.05). Except sham group, the escape latency of the other two groups were gradually shortened with the increase of training times. There were no statistical difference between the two groups on day 1 and 3, and the performance of RIC group was better than that of control group on day 5 (P <0.05). In the space probe test on day 6, the sham group was similar to RIC group in the platform stay time (47.2±10.2 s vs 41.2±9.7 s, P >0.05), and they were better than control group (33.5±11.3 s) (both P <0.05). The sham group was similar to RIC group in the times of crossing platform (5.3±1.6 vs 4.7±1.2, P >0.05), and they were more than control group (2.8±1.3) (both P <0.05). In the probe test, compared with sham group, the control group showed a chaotic curve trajectory lacking purpose; compared with control group, the RIC group showed a more regular curve with a clear purpose. Compared with sham group (CA1: 93.53±5.01; CA3: 104.63±8.26), the number of surviving pyramidal neurons in CA1 and CA3 areas in control group (CA1: 51.03±4.95; CA3: 78.53±5.31) decreased significantly (both P <0.05); compared with control group, the survival number of surviving pyramidal neurons in CA1 and CA3 areas in RIC group (CA1: 80.57±7.30; CA3: 92.43±8.16) increased significantly (both P <0.05). Conclusions Cerebral ischemia-reperfusion injury can cause VCI presenting with learning and memory impairment. RIC can significantly improve VCI by playing neuroprotective effect.

Key words: Remote ischemic conditioning; Cerebral ischemia reperfusion; Cognitive impairment; Neuroprotective effect

摘要：

目的 观察远隔缺血处理对缺血再灌注损伤所致认知障碍大鼠的神经保护作用及其作用机理。 方法 选用雄性SD大鼠，采用双侧颈动脉闭塞（bilateral common carotid arteries occlusion，BCCAO）方 法建立脑缺血再灌注致血管性认知障碍（vascular cognitive impairment，VCI）动物模型，将大鼠随机分 为假手术组、对照组（VCI组）及远隔缺血处理（remote ischemic conditioning，RIC）组（VCI+RIC组）。VCI 建模成功24 h后对RIC组大鼠进行RIC连续干预21 d，RIC期满后对三组大鼠采用Morris水迷宫实验进行 定位航行实验和空间探索实验，定位航行实验连续进行5 d，记录第1天、第3天、第5天检测大鼠逃避 潜伏期，第6天检测平台停留时间和穿越平台次数以评估认知功能。实验完成后在各组大鼠中随机 选择5只取脑进行HE染色，电镜下观察各组大鼠脑白质及海马病理改变和神经元凋亡情况。 结果 Morri s水迷宫实验结果显示第1天、第3天、第5天对照组及RI C组大鼠逃避潜伏期较假手术组 均有延长（P＜0.05）。除假手术组外，另外两组大鼠逃避潜伏期时长随着训练次数增加逐渐缩短。 第1天、第3天两组间差异无统计学意义，第5天RIC组成绩好于对照组（P＜0.05）。第6天空间探索实验 中，目标象限停留时间假手术组与RIC组相近（47.2±10.2 s vs 41.2±9.7 s，P＞0.05），均优于对照组 （33.5±11.3 s），差异均具有统计学意义；穿越平台次数假手术组与RIC组相近（5.3±1.6 vs 4.7±1.2， P＞0.05），均多于对照组（2.8±1.3），差异均具有统计学意义。在空间探索实验中，与假手术组比较， 对照组大鼠的运动缺乏目的性而呈现出杂乱的曲线轨迹，RIC组相对于对照组具有明确的目的呈现 出较规则的曲线。HE染色显示与假手术组（CA1：93.53±5.01；CA3：104.63±8.26）相比，对照组CA1区 和CA3区存活的锥体神经元数目（CA1：51.03±4.95；CA3：78.53±5.31）明显减少（均P＜0.05）；而与 对照组相比，RIC组大鼠CA1区和CA3区锥体神经元存活数目（CA1：80.57±7.30；CA3：92.43±8.16）明 显增加（均P＜0.05）。 结论 脑缺血再灌注损伤可引起大鼠学习记忆障碍而导致VCI。RIC能够明显改善VCI，发挥神经保护 作用。

关键词: 远隔缺血处理; 脑缺血再灌注; 认知功能障碍; 神经保护