缺血再灌注预处理对血浆MDA、SOD及脊髓AQP4mRNA的表达影响

Effect of Ischemic Preconditioning on the expression of blood plasma MDA, SOD and AQP4 mRNA of spinal cord

目的探讨腹主动脉缺血预处理对再灌注不同时间血浆丙二醛（MDA）、超氧化物歧化酶（SOD）及脊髓组织中水通道蛋白4（AQP4）mRNA表达的影响。方法将54只体质量189—207g雌雄不拘的sD大鼠随机分为假手术组（Sham组）、缺血再灌注组（I／R组）和缺血预处理组（IPC组）3组。采用肾下腹主动脉阻断法，建立脊髓缺血再灌注模型；Sham组6只，手术开始步骤同其他两组，但不作肾下腹主动脉阻断即缝合伤口；I／R组24只，直视下采用动脉夹夹闭腹主动脉段左肾动脉分支起始处下方5mm处（即肾动脉后型），仅阻断腹主动脉60min后开放灌注；而IPC组24只，先阻断腹主动脉5min，开放5min，再阻断60min后开放灌注。再灌注后12h、1、2、5、10天分别进行神经功能评分，同时观察大鼠血浆MDA、SOD指标的水平，以及预处理对脊髓AQP4mRNA表达的影响。结果54只大鼠术后全部存活，I／R组行为学评分降低（P〈0．01），IPC组的神经功能评分在再灌注5天内均高于I／R组（P〈0．01），随着再灌注时间的延长行为学评分逐渐增加。I／R组血浆SOD水平仅在再灌注1天时较Sham组显著下降，随时间延长SOD水平逐渐升高与Sham组无差异，血浆各时间点MDA水平比Sham组低（P〈0．05）；IPC组SOD、MDA水平与Sham组比较没有差异。I／R组再灌注2天时AQP4mRNA表达显著增高（P〈0．01），之后降低至与Sham组无差异；IPC组在再灌注1天时即出现AQP4mRNA表达明显升高（P〈0．05），之后表达逐渐降低，第5天时与Sham组无差异。IPCAQP4mRNA峰值明显低于I／R组（P〈0．01）。结论大鼠腹主动脉缺血再灌注的预处理IPC可能通过减轻由缺血再灌注造成的全身氧化应激反应和下调AQP4mRNA的表达，进而保护脊髓组织。

Objective To investigate the protective effect of Ischemic preconditioning （ IPC ） on the expression of MDA, SOD and AQP4 mRNA of spinal cord following abdominal aorta occlusion. Methods Fifty-four SD rats were randomly divided into three experimental groups： group Sham, group I/R and group IPC. In group Sham, only laparotomy was performed without further treatment. In group I/R （ischemia reperfusion injury group）, a 60 min abdominal aorta occlusion was induced with bulldog clamping. In group IPC, preconditioning of 5 rain ischemia and 5 min unclamp by the clamping abdominal aorta were followed by 60 min of reperfusion. At times of 12 hours, 1, 2, 5, 10 days after reperfusion behavior scores were respectively given. The contents of malondialdehyde （MDA） and superoxide dismutase （SOD） in blood plasma were determined withenzyme-labeled instrument. Real-time PCR was used to detect the AQP4 mRNA in different treated groups. Results After op- eration 54 SD rats were all survival. Behavioral score of group I/R decreased until 5 days after reperfusion and the scores of group IPC were all higher than group I/R, by increasing as time went by. The SOD content of group I/R 24 h after reperfusion was dramatically decreased than group Sham, and the MDA contents were all lower（ P 〈 0.05 ） than group Sham. In group IPC the contents of SOD and MDA showed no significance with group Sham. At the same time, compared with group Sham, AQP4 mRNA expression of group I/R in spinal cord after reperfusion 2 days showed obviously statistical increasing （P 〈 0.01 ）, and that of group IPC after reperfusion 1 day showed increasing（ P 〈 0.05 ）, and then AQP4 mRNA expression was kept decreasing until 5 days after reperfusion. The peak value of AQP4 mRNA in group IPC was lower than group I/R （ P 〈 0.01 ）. Conclusion Ischemia preconditioning in rats could protect spine from I/R injury by reducing oxidative stress and AQP4 mRNA expression.