短暂性脑缺血再灌注损伤对老年大鼠海马脑组织水通道蛋白4表达及神经元凋亡的影响

目的 探讨短暂性脑缺血再灌注损伤对老年大鼠海马脑组织水通道蛋白4表达及神经元凋亡的影响.方法 健康老年Wistar大鼠160只按Pnsinelli方法建立四动脉阻断法全脑缺血模型,随机分为脑缺血1 min组、脑缺血3 min组、脑缺血5 rain组和假手术组,每组40只.每组又按再灌注时间分为再灌注12 h、1 d.2 d.3 d和7 d 5个亚组,每个亚组8只.应用干湿重法计算脑含水量、组织病理学染色观察神经元微观结构,免疫组化方法观察AQP4的表达,TUNEL法检测神经元凋亡.结果 缺血1 rain及3 min组各再灌注时间点脑组织含水量及AQP4表达与假手术组比较差异无统计学意义(P0.05),而缺血5 min组各再灌注时间点脑组织含水量及AQP4表达与假手术组比较差异有统计学意义(P<0.05).假手术组及缺血1 min组有少量神经元凋亡,缺血3 min及缺血5 min后海马区神经元凋亡明显增加.神经元凋亡在缺血后再灌注12 h即有表达,在1 d达高峰,持续至第3天开始下降.结论 老年脑对缺血再灌注损伤的敏感性增加,短暂的脑缺血即可造成老年大鼠脑组织的水肿和AQP4表达及神经元凋亡的增加,神经元的凋亡较脑水肿或AQP4表达对缺血更为敏感;再灌注后神经元凋亡高峰出现得早,持续时间长.

Effects of transient cerebral ischemia and reperfusion Injury on expression of aquaporin-4 and apoptosis in hippocampal neurons of aged animals: experiment with rats

Objective To investigate the effects of transient cerebral ischemia and reperfusion injury on brain edema and apoptosis hippocampal neurons of aged animals. Methods 120 19-21-month old healthy Wistsr rats underwent four-vessel occlusion to estubhsh whole cerebral ischernia model and were randomly divided into 3 equal groups to undergo ischemia for 1 min, 3 min, and 5 min respectively. Every group was re-divided into 5 equal sub-groups to undergo reperfusion for 12 h, 1 d, 2 d, 3 d, and 7 d respectively. Another 40 rats underwent sham operation to be used as controls. At different reperfusion time points 4 rats from each subgroup were killed to measure the wet and dry weights of the hippocampus. The brains of the remaining 4 rats from each subgroup underwent HE staining and microscopy. The expression of aquaporin-4 (AQP4) was detected by SABC immunohistochemical technique, and the neuron apoptosis in hippocampus was detected by TUNEL method. Results There was no significant differences in brain water content and expression of AQP4 between the isehemia 1 rain and 3 rain subgroups and the corresponding sham-operation subgroups( all P0.05 ), however, the brain water contents and AQP4 expression levels of the ischemia 5 mln subgroups were all significantly higher than those of the corresponding sham-operation subgroups(all P<0.05). There were only a few TUNEL-positive ceils in the sham-operation subgroups and ischemia 1 rain subgroups, however, the numbers of TUNEL-positive cells of the isehemia 3 min and 5 min subgroups were all significantly higher. The number of TUNEL-positive cells raised 12 h after ischemia, peaked 1 day after, and began to go down 3 days later. Conclusion The aged animals are more sensitive to cerebral ischemia/reperfusion injury, and transient cerebral ischemia may cause brain edema, and increase of apoptotic cells and AQP4 expression. Neuron apoptesis is more sensitive to cerebral isehemia than brain edema and AQP4 expression. After reperfusion neuron apoptosis peaks esrlier and lasts longer in the aged animals.