【作者】 何萍；

【导师】 陈忠；

【作者基本信息】 浙江大学 ， 药理学， 2010， 硕士

【摘要】 缺血后处理是近期发现的一种基于内源性保护策略的新干预措施,它是在缺血后给予一系列重复的间隔缺血再灌循环的处理手段,目前虽然在整体和离体的模型上都验证了缺血后处理的保护作用,但是关于脑缺血后处理的保护机制目前还不清楚,尤其是缺糖和缺氧两大因素在再灌中究竟发挥了怎样的作用尚不明确。有研究提示对兴奋性递质谷氨酸的调节可能是后处理的保护机制之一。而星型胶质细胞通过GLT-1转运体和谷氨酰胺合成酶(GS)代谢谷氨酸,对维持细胞间谷氨酸的稳态起了重要作用。因此本课题将着重探讨缺血后处理中缺糖和缺氧的作用,并进一步探讨其是否通过调节星形胶质细胞谷氨酸代谢发挥作用。本实验采用小鼠的暂时性局灶性脑缺血模型,观察低氧后处理对缺血损伤的影响,发现低氧后处理呈时间依赖性的增加了小鼠的脑梗死体体积。我们建立了小鼠皮层纹状体脑片缺血后处理模型,探索了后处理持续时间和再灌时间窗,发现缺糖缺氧(OGD)15 min后再灌5 min给予1 min的OGD后处理能显著逆转OGD再灌损伤。在此基础上比较了缺糖和缺氧在缺血后处理中的作用,发现脑片OGD或缺糖后处理能显著逆转OGD再灌引起的损伤,然而给予缺氧后处理则无明显保护作用。并且OGD后处理和缺糖后处理均可显著逆转谷氨酸含量的升高和GABA含量的下降,同时逆转OGD再灌引发的GLT-1表达下调和GS活性下降,缺氧后处理则无明显逆转作用。以上结果提示缺糖可能是OGD后处理形成保护作用的主要原因,这种作用可能与调节星型胶质细胞GLT-1表达和GS活性,进而调节谷氨酸和GABA含量,降低脑缺血后兴奋性损伤有关。更多还原

【Abstract】 Cerebral ischemic postconditioning has emerged recently as a kind of endogenous strategies for neuroprotection, which was defined as a sub-threshold ischemic insult applied to the brain after ischemic reperfusion. It may have great clinical potential. However, protective mechanisms of ischemic postconditioning are largely unknown, especially the roles of glucose deprivation and oxygen deprivation as two factors in ischemia postconditioning has not been reported. Several lines of evidence imply that regulating the level of excitability neurotransmitter glutamate may be involved in ischemic postconditioning induced neuroprotection. Astrocytes play an important role in maintaining balance of extracellular glutamate by glutamate transporter(GLT-1) and glutamine synthetase (GS). Therefore, in present study we investigated the roles of glucose deprivation and oxygen deprivation in ischemic postconditioning, and whether the protection is associated with glutamate metabolism regulated by astrocytes. At first, we found that hypoxic postconditioning aggravated neurological function and increased infarct size after transient middle cerebral artery occlusion in mice. We also established a model of oxygen-glucose deprivation (OGD) postconditioning in mouse corticostriatal slices. Corticostriatal slices injury induced by OGD and reperfusion (OGD/R) was significantly inhibited by OGD postconditioning with 1 min of OGD treated at 5 min after 15 min of OGD. Furthermore, glucose deprivation postconditioning with 1 min of glucose deprivation treated at 5 min after 15min of OGD also produced significantly neuroprotection which is comparable with OGD postconditioning. However, oxygen deprivation postconditioning with the same procedure has no neuroprotection on OGD/R-induced injury. And OGD or glucose deprivation postconditioning significantly reversed the up-regulation of glutamate and down-regulation of GABA. They also remarkably reversed down-regulation of Glt-1 expression and GS activity induced by OGD/R. These results suggest that glucose deprivation in ischemic postconditioning is the main factor which induces neuroprotection. And this effect may be associated with up-regulating GLT-1 expression and GS activity in astrocytes and furthermore regulating glutamate and GABA levels, which probably inhibits neurotoxicity induced by ischemia reperfusion.更多还原