乙醛脱氢酶3A1对紫绀先心病矫治术后肺缺血再灌注损伤的影响及作用机制

Pulmonary complications caused by ischemia and reperfusion (I/R) injury are the main contribution of postoperative respiratory dysfunction in cyanotic congenital heart disease. Aldehyde Dehydrogenase (including ALDH2 and ALDH3A1) can detoxify aldehydes generated in the process of I/R into nontoxic acetic acid. The accumulation of aldehydes inactivate ALDH2 while the activity of ALDH3A1 is not effected and its expression is upregulated. Our preliminary experiment showed that ALDH2 and ALDH3A1 contribute to 56% and 30% of the total ALDH activity of the normal lung, respectively. Our previous studies have found that chronic hypoxia (cyanosis) can significantly influence the activity of ALDH2 in myocardial and lung tissue, so we speculate that ALDH3A1 may play the main role in aldehyde metabolism in the lung with cyanotic congenital heart disease. In this research, we will employ pulmonary I/R model of rats exposed to chronic hypoxia to confirm the effection of ALDH3A1 on lung aldehydes metabolism. We will also examine if ALDH3A1 agonist could reduce lung I/R injury. Finally, we will observe if ALDH3A1 reduce cell injury through activation of ERK/MAPK and PI3K-Akt pathways. We are willing to provide new therapeutic targets for the prevention and treatment of I/R lung injury in surgical correction of cyanotic congenital heart diseases.

缺血/再灌注（I/R）损伤所导致的肺部并发症是紫绀型先心病术后呼吸功能不全的主要原因。乙醛脱氢酶（ALDH2、ALDH3A1）可将I/R过程中产生的醛类物质代谢为无毒的乙酸。我们预实验发现正常状态下ALDH2和ALDH3A1的活性分别占肺ALDH总活性的56%和30%。当醛类蓄积时ALDH2易失活而ALDH3A1不易失活且表达增加。前期研究中发现紫绀（慢性缺氧）明显诱导心肌和肺组织的醛类毒物蓄积，因此我们推测ALDH3A1可能是紫绀型先心病肺内主要的醛类代谢酶。本研究利用慢性缺氧大鼠及肺I/R模型，明确紫绀状态下ALDH3A1在肺内醛类物质代谢中的作用，检验ALDH3A1特异性激动剂可否减轻肺I/R损伤，同时观察ALDH3A1是否通过激活ERK/MAPK和PI3K-Akt信号通路减轻细胞损伤，从而为紫绀型先心病矫治术肺I/R损伤的临床防治提供特异性的治疗靶点。

目的：肺缺血再灌注损伤（lung ischemia-reperfusion injury, LIRI）常导致体外循环（cardiopulmonary bypass, CPB）辅助下心脏手术术后呼吸功能不全，而过度氧化应激是其最主要原因。既往研究表明，激活乙醛脱氢酶2（aldehyde dehydrogenase-2, ALDH2）可以显著减少氧化应激导致的毒性醛类物质蓄积，从而减轻心脏和脑的缺血再灌注（ischemia-reperfusion, I/R）损伤。然而，在肺缺血再灌注损伤中，醛类物质毒性和ALDH2激动剂Alda-1可能发挥的保护作用均尚无研究。.方法：本研究以原代人肺泡上皮细胞（human pulmonary alveolar epithelial cells, HPAEpiC），原代人肺微血管内皮细胞（human pulmonary microvascular endothelial cells, HPMEC）和Sprague–Dawley大鼠为研究对象。分别使用体外缺氧复氧 （hypoxia/reoxygenation, H/R）细胞培养模型，和在体原位肺I/R模型模拟LIRI。检测和评价Alda-1对ALDH2含量活性、醛类物质含量和肺损伤程度的影响。.结果：I/R导致肺损伤，伴随肺组织和HPAEpiC内醛类物质蓄积，但HPMEC内并无明显醛类物质蓄积。Alda-1预处理可以显著提高ALDH2活性，增加表面活性物质相关蛋白C （surfactant associated protein C, SP-C）表达，减轻4-羟基壬烯醛 （4-hydroxy-2-nonenal, 4-HNE）蓄积、细胞凋亡、细胞间粘附分子-1 （intercellular adhesion molecule-1, ICAM-1）上调、炎症反应和肺泡毛细血管屏障 （permeability of pulmonary alveolar capillary barrier, PACB）通透性增加，从而缓解肺损伤。.结论：4-HNE蓄积在LIRI中发挥重要作用。Alda-1预处理可以通过激活ALDH2活性，减轻HPAEpiC内4-HNE蓄积，从而减轻LIRI。Alda-1预处理对CPB期间的肺保护有临床应用价值。