Aoki M, Abe K, Kawagoe J, Nakamura S, Kogure K
Department of Neurology, Tohoku University School of Medicine, Sendai, Japan.
J Cereb Blood Flow Metab. 1993 Sep;13(5):781-8. doi: 10.1038/jcbfm.1993.99.
To evaluate the mechanism of tolerance to ischemia, inductions of heat shock protein (HSP) 70 and heat shock cognate protein (HSC) 70 mRNAs in gerbil hippocampus were compared with in situ hybridization between cases of a single 3.5-min period of forebrain ischemia and a 3.5-min period of ischemia 2 days after 2-min pretreatment with ischemia. Immunohistochemistry for HSP70 protein and morphological studies were also performed in the same brains up to 7 days after the reperfusion. Following a single 3.5-min period of ischemia, HSP70 and HSC70 mRNAs were induced in all hippocampal cells. However, the hippocampal CA1 cells produced only a minimum of HSP70 protein, and the cells were almost lost by 7 days. Following 3.5 min of ischemia after 2-min pretreatment, large populations of the CA1 cells survived at 7 days. The peak time of the HSP70 and HSC70 mRNA induction shifted to an earlier period of reperfusion in all hippocampal cells as compared with the case of a single episode of ischemia. The peak of HSP70 and HSC70 mRNA induction shifted from 1 day to 3 h in the CA1 cells. The CA1 cells produced strongly immunoreactive HSP70 from 3 hr to 2 days. These results suggest that pretreatment with an initial period of ischemia (for 2 min) accelerated HSP70 and HSC70 gene expression at the transcriptional level, ameliorated the translational disturbance of HSP70 mRNA to protein, and saved the CA1 cells from subsequent lethal ischemia (for 3.5 min). These changes of heat shock gene expression might play important roles in the acquisition of ischemic tolerance of hippocampal CA1 neurons.
为评估缺血耐受机制，采用原位杂交技术，比较沙土鼠海马中热休克蛋白（HSP）70和热休克同源蛋白（HSC）70 mRNA在单次3.5分钟前脑缺血及在2分钟缺血预处理2天后再进行3.5分钟缺血两种情况下的诱导情况。在再灌注后长达7天的同一批大脑中，还进行了HSP70蛋白的免疫组织化学检测和形态学研究。单次3.5分钟缺血后，所有海马细胞均诱导出HSP70和HSC70 mRNA。然而，海马CA1区细胞仅产生极少量的HSP70蛋白，且这些细胞在7天时几乎全部丧失。在2分钟预处理后再进行3.5分钟缺血，大量CA1区细胞在7天时存活。与单次缺血情况相比，所有海马细胞中HSP70和HSC70 mRNA诱导的峰值时间提前至再灌注的更早阶段。CA1区细胞中HSP70和HSC70 mRNA诱导的峰值从1天提前至3小时。CA1区细胞在3小时至2天产生强免疫反应性的HSP70。这些结果表明，初始阶段的缺血预处理（2分钟）在转录水平加速了HSP70和HSC70基因表达，改善了HSP70 mRNA到蛋白的翻译障碍，并使CA1区细胞免受随后的致死性缺血（3.5分钟）损伤。热休克基因表达的这些变化可能在海马CA1神经元缺血耐受的形成中起重要作用。
