Investigation on therapeutic potentials of inducing ischemic tolerance against ischemic neuronal damage in the spinal cord

截瘫是胸腹部动脉瘤手术中由于脊髓缺血引起的严重并发症。没有制定预防和治疗措施。大量资料表明，中枢神经系统在受到致死性损伤之前，先受到非致死性应激，可获得对缺血损伤的耐受性。本研究采用大鼠和家兔脑缺血模型，观察高压氧（HBO）对脑缺血后神经元存活的影响，并探讨HBO对脑缺血耐受的机制。高压氧预处理在2.5 ~ 3.5ATA（1h/d，共5d）。基因表达和翻译的蛋白质的顺序变化进行了评估，使用DNA微阵列，蛋白质印迹，和RT-PCR。在接受短期缺血预处理的家兔中，在脊髓运动神经元的胞质中检测到HSP-70。在大鼠脊髓中检测到谷胱甘肽过氧化物酶和缺氧诱导因子-1（HIF-1）基因。当动物进行8分钟前脑缺血后HBO治疗，海马CA 1区神经元死亡显着减少，改善是最突出的HBO后12小时。基因组反应的聚类分析显示p75神经营养因子受体（p75 NTR）和CCAAT增强子结合蛋白δ（C/EBPδ）的表达。RT-PCR和Western blotting结果表明，神经生长因子受体和炎症/免疫反应相关的信号转导参与了中枢神经系统的缺血耐受。调控这些相关基因可能为中枢神经系统缺血性损伤提供新的治疗策略。

Paraplegia is a serious complication caused by spinal cord ischemia during thoracoabdominal aneurysm surgery. Preventive and therapeutic measures are not established. Accumulated data show that central nervous system acquires tolerance against ischemic insult when the neuronal tissues are exposed to non-lethal stress before it is subjected to lethal insult. In the present study we examined the effects of hyperbaric oxygen (HBO) on neuronal survival after ischemia and the mechanism for ischemic tolerance.We used ischemic model in rats and rabbits. Preconditioning with HBO was performed at 2.5〜3.5 ATA (1h/day for 5days). Sequential changes of gene expression and of translated protein were evaluated using DNA microarray, Western blotting, and RT-PCR. In the rabbit that received preconditioning with a short period of ischemia, HSP-70 was detected in the cytoplasm in the motor neurons in the spinal cord. In rats, genes of glutathione peroxidase and hypoxia inducible factor-1 (HIF-1) were detected in the spinal cord. When the animals were subjected to 8-min forebrain ischemia following HBO treatment, neuronal death in the hippocampal CA1 was markedly curtailed, the amelioration being most prominent at 12 hour after HBO. Cluster analysis of the genomic response demonstrated expressions of p75 neurotrophin receptor (p75NTR) and CCAAT-enhancer binding protein δ(C/EBPδ). These changes were confirmed also with RT-PCR and Western blotting.The results suggest that the signal transduction related to nerve growth factor receptor and inflammatory/immune response is involved in ischemic tolerance in the central nervous system. Modulation of these related genes may provide new therapeutic strategy against ischemic damage in the central nervous system.