Can apoptosis-suppressing proteins inhibit neuronal necrosis induced by brain ischemia?

目的：研究缺血性神经元细胞死亡中凋亡与坏死之间的串扰。方法：(1)检测大鼠海马锥体神经元中凋亡诱导蛋白caspase3在缺血性坏死模型中的酶促活性，(2)检测凋亡抑制蛋白如热休克蛋白在缺血性坏死模型中的作用。结果：(1)体外缺血后6min， CAl锥体神经元膜快速去极化（rapid depolarization: RD），即使缺血终止，去极化现象仍持续存在。此时可见球囊状神经元，显示神经元坏死。在坏死模型中，caspase3酶活性随着缺血暴露时间的延长而升高。(2)大鼠腹腔注射低剂量（5mg/kg） kainic acid （KA）可诱导海马CAl区产生热休克蛋白，KA预处理可减少体内缺血引起的CAl神经元凋亡。经预处理后，体外缺血产生的RD明显延长，膜电位恢复到缺血前水平的神经元数量增加。这些作用在治疗后3天达到最大，对RD的作用可以被蛋白质合成抑制剂环己亚胺所抑制。未给药和给药大鼠CAl神经元电膜特性、神经末梢谷氨酸释放效率和谷氨酸受体敏感性均无显著差异。ka预处理大鼠缺血终止激活的慢直流电电位升高。结论：KA预处理对坏死模型中凋亡诱导蛋白的激活和对坏死和凋亡的抑制提示凋亡和坏死之间可能存在串扰。

Purpose : Study of cross talk between apoptosis and necrosis in the ischemic neuronal cell death.Method : (1) Enzymatic activities of apoptosis-inducing protein, caspase3 in the ischemic necrosis model and (2) the effect of the apoptosis-suppressing protein, such as heat shock proteins for the necrosis model were examined in the hippocampal pyramidal neurons of the rat.Results : (1) The membrane of the CAl pyramidal neuron rapidly depolarized 6min after in vitro ischemia (rapid depolarization : RD) and the depolarization persisted even when the ischemia was teminated. At this point balloon-shaped neurons were observed, showing neuronal necrosis. In this necrosis model, the enzymatic activity of caspase3 was increased according as exposure time of the ischemia was prolonged. (2) Intra-peritoneum administration of low dose of kainic acid (KA)(5mg/kg) to the rat induces heat shock proteins in CAl area of the hippocampus, and apoptosis of CAl neuron caused by in vivo ischemia can be reduced by pretreatment of KA. By the pretreatment, the RD produced by in vitro ischemia was significantly prolonged and the number of neurons that the membrane potential was restored to the pre-ischemic level was increased. These effects were maximal at 3 days after the treatment and the effect for the RD could be inhibited by protein synthesis inhibitor, cycloheximide. There were no significant differences in electrical membrane properties of CAl neuron, release efficiency of glutamate from nerve terminals and glutamate receptor sensitivity between non-treated and treated rats. the slow DC potential that was activated by termination of ischemi was increased in KA-pretreated rats.Conclusion : Activation of apoptosis-inducing protein in necrosis model and inhibition of both necrosis and apoptosis by pretreatment of KA suggest the possibility of existence of cross talk between apoptosis and necrosis.