目的:缺血后处理,长期缺血性损伤后短暂的缺血发作,已发现可以减少中风后延迟的神经元丢失。然而,这种内源性神经保护策略的潜在机制仍然不清楚.在这项研究中,我们试图探讨兴奋性突触后信号事件与缺血后处理的神经保护作用有关。
方法:采用4血管阻断法诱导雄性SD大鼠全脑缺血15分钟。10分钟后通过单次再闭塞3分钟进行缺血后处理。
结果:再灌注5天后,严重的全脑缺血几乎破坏了所有的海马CA1区锥体神经元。短暂的缺血后处理强烈减少了缺血后的神经元损失。前服用磷酸肌醇3-激酶抑制剂LY294002阻断了后处理的神经保护作用,而丝裂原活化蛋白激酶激酶1抑制剂PD98059则没有作用。缺血后处理显著增加了Akt磷酸化(Ser473)。此外,后处理不仅干扰了突触后密度蛋白95与谷氨酸能的海藻酸盐受体亚基2和混合谱系激酶3的结合,而且还抑制了混合谱系激酶3,丝裂原活化蛋白激酶7和c-JunN-末端激酶3的下游激活。LY294002,而不是PD98059,消除了后处理诱导的谷氨酸能海藻酸盐受体亚基2-突触后密度蛋白-95混合谱系激酶3复合物和混合谱系激酶3-c-JunN末端激酶3信号传导的减少。Akt抑制剂IV,一种特定的Akt抑制剂,显示与LY294002相同的效果。
结论:缺血后处理通过减弱突触后谷氨酸能海藻酸盐受体亚基2-突触后密度蛋白-95混合谱系激酶3-c-JunN末端激酶3信号级联,通过磷酸肌醇3-激酶-Akt通路,保护神经元免受中风。
OBJECTIVE: Ischemic postconditioning, a brief episode of ischemia after a prolonged ischemic insult, has been found to reduce the delayed neuronal loss after stroke. However, the mechanisms underlying such endogenous neuroprotective strategy remain obscure. In this study, we try to explore the excitatory postsynaptic signal events associated with neuroprotective effect of ischemic postconditioning.
METHODS: Global cerebral ischemia was induced for 15 minutes by the 4-vessel occlusion method in male Sprague-Dawley rats. Ischemic postconditioning was conducted 10 minutes later by a single reocclusion for 3 minutes.
RESULTS: A severe global cerebral ischemia after 5 days of reperfusion destroyed almost all hippocampal CA1 pyramidal neurons. A brief ischemic postconditioning robustly reduced the neuronal loss after ischemia. Preadministration of phosphoinositide 3-kinase inhibitor LY294002 blocked the neuroprotection of postconditioning, whereas mitogen-activated protein kinase kinase 1 inhibitor PD98059 had no effect. Ischemic postconditioning significantly increased the Akt phosphorylation (Ser473). In addition, postconditioning not only perturbed the binding of postsynaptic density protein-95 with glutamatergic kainate receptor subunit 2 and mixed lineage kinase 3 but also suppressed the downstream activation of mixed lineage kinase 3, mitogen-activated protein kinase kinase 7, and c-Jun N-terminal kinase 3. LY294002, but not PD98059, abolished the postconditioning-induced decreases in the assembly of glutamatergic kainate receptor subunit 2-postsynaptic density protein-95-mixed lineage kinase 3 complex and in the mixed lineage kinase 3-c-Jun N-terminal kinase 3 signaling. Akt inhibitor IV, a specific Akt inhibitor, showed the same effects as LY294002.
CONCLUSIONS: Ischemic postconditioning protects neurons against stroke by attenuating the postsynaptic glutamatergic kainate receptor subunit 2-postsynaptic density protein-95-mixed lineage kinase 3-c-Jun N-terminal kinase 3 signal cascade via phosphoinositide 3-kinase-Akt pathway.