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

方法：(1)在大鼠海马锥体神经元中检测凋亡诱导蛋白caspase3在缺血坏死模型中的酶活性，以及(2)热休克蛋白等凋亡抑制蛋白对坏死模型的影响。结果：(1)体外缺血6min后，CA1区锥体神经元膜迅速去极化(快速去极化：RD)，即使在缺血结束后，这种去极化仍然存在。此时可见气球状神经元，表现为神经元坏死。在该模型中，caspase3的酶活性随缺血时间的延长而增加。(2)小剂量海人酸(KA)(5 mg/kg)腹腔注射可诱导大鼠海马CA1区热休克蛋白表达，KA可减少体内缺血所致的CA1区神经元的凋亡。经预处理后，体外缺血所产生的RD明显延长，使膜电位恢复到缺血前水平的神经元数目增加。这些作用在治疗后3d达到最大，对RD的作用可被蛋白质合成抑制剂放线菌酮所抑制。未用药组与用药组大鼠脑海马神经元电膜特性、神经末梢谷氨酸释放效率及谷氨酸受体敏感性均无显著差异。KA可使缺血终止所激活的DC慢电位升高。结论：KA可激活坏死模型中的凋亡诱导蛋白，并同时抑制坏死和细胞凋亡，提示可能存在细胞凋亡和坏死之间的串扰。

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.