先心病患儿线粒体ALDH2活化对深低温停循环期间突触可塑性的影响及机制研究

Cerebral injury after deep hypothermic circulatory arrest (DHCA) is of great concerns in infants with congenital heart disease. The newly study discovered that synaptic plasticity is associated with postoperative neurological changes, learning and memory ability. Synaptic plasticity and its mechanism is not yet clear in infants with complex congenital heart disease during DHCA. Studies in hibernator found that synaptic plasticity is associated with the integrity of the nerve function, and that 4–HNE induces damage of synaptic NMDA receptors and synaptic protein is a key link in the process of impact synaptic plasticity. ALDH2, an aldehyde oxidase in the mitochondria, could effectively remove 4-HNE. Our preliminary experiment found that 4-HNE is related to synaptic damage, and ALDH2 activity is inhibited during DHCA. Therefore we propose a hypothesis that 4-HNE induces the damage of synaptic NMDA receptors and protein, thus synaptic plasticity is damaged, and the activation of ALDH2 by Alda-1 could effectively remove 4-HNE, thus improve the synaptic plasticity. The study would performed based on piglet DHCA model and PCCN, and explore the mechanism of the change in synaptic plasticity, to provide theoretical basis in cerebral protective effect in infants with complex congenital heart disease during DHCA.

深低温停循环（DHCA）后脑损伤是临床亟待解决的难题，研究发现突触可塑性与术后神经功能及学习能力相关，但DHCA期间突触可塑性改变及机制未明。在冬眠动物中发现，突触可塑性参与了神经功能的完整保存，而4-HNE介导NMDA受体及突触相关蛋白损伤是影响突触可塑性的关键环节。ALDH2作为线粒体中的醛类氧化酶，可有效清除神经元中4-HNE。预实验发现DHCA期间ALDH2活性明显抑制,且4-HNE含量与突触损伤存在明显的相关性，故本研究提出“先心病患儿DHCA期间4-HNE通过干扰NMDA介导的钙离子内流而影响突触可塑性，经Alda-1特异性激活ALDH2可有效清除4-HNE，进而改善突触可塑性”的新假说。本课题拟以原代皮质神经元氧糖剥夺/复糖复氧模型和幼猪DHCA模型为基础，探讨ALDH2的激活加强清除4-HNE诱导突触可塑性的可能机制，为改善复杂先心病患儿DHCA期间脑保护效果提供理论基础。

深低温停循环（DHCA）后脑损伤是临床亟待解决的问题，研究发现突触可塑性与术后神经功能及学习能力相关，冬眠动物中发现，突触可塑性参与了神经功能的完整保存，而4-HNE这类醛类物质的蓄积可能会导致神经元损伤。通过特异性激活ALDH2酶活性可以增加4-HNE的清除从而发挥脑保护作用。.我们通过给予ALDH2激活剂，Alda-1，预处理大鼠并建立深低温停循环模型发现，ALDH2蛋白质及mRNA表达量在各组中均未见差异，同时，脑海马神经元中4-HNE加合物在深低温停循环组明显增加，Alda-1组增高不具有统计学意义（12.56±7.67 ug/mg vs 102.18±39.56 ug/mg vs 38.39±15.81 ug/mg, Sham vs DHCA vs Alda-1, n=5），说明DHCA或Alda-1预处理并不会导致ALDH2蛋白及mRNA表达水平的变化，而是会降低或升高酶活性而发挥作用。TUNEL凋亡细胞染色可以发现， Alda-1预处理可明显减少DHCA后神经元凋亡数量。透视电镜结果提示DHCA组中海马神经元神经元细胞核、突触结构受损；Alda-1预处理可减轻突触结构损伤程度。通过对突触可塑性相关的蛋白检测发现，深低温停循环组及Alda-1预处理组中突触有关修复蛋白Gap43明显增高，且Alda-1组中Gap 43升高较DHCA组明显，差值具有统计学意义（P＜0.05）。Alda-1预处理发挥脑保护作用的潜在机制可能是通过激活ALDH2活性进而在一定程度降低深低温停循环导致的pP38-P38通路的激活，同时增加对Bcl-2 /Bax凋亡通路的激活进而减少神经元坏死。.研究结果发现激活ALDH2酶活性会减轻神经元损伤，促进神经元突触可塑性的恢复，为临床工作中实现更好的神经系统保护提供了分子学依据，为降低DHCA后脑并发症打下坚实的理论基础。