Akt／GSK-3β信号通路和线粒体渗透性转换孔在吸入性麻醉药预处理对老年大鼠心肌缺血保护的研究

Age-associated Differences and Mechanism in Isoflurane Preconditioning

目的Akt／GSK．3β信号通路的激活参与了吸人麻醉药心肌保护预处理。在该研究中观察了老年和成年大鼠在异氟醚心肌保护预处理中的差异，包括Akt／GSK-3β信号通路和线粒体渗透性转换孔在异氟醚预处理中的差异。方法雄性Fisher344大鼠按照各自的年龄，成年（3—5月）、老年（20～24月），随机分配到阴性对照组（sc）、缺血再灌注组（I／R）、异氟醚组（ISO）中。ISO组，大鼠接受30min1．0MAC的异氟醚预处理。I／R组，大鼠接受30min的心肌缺血。方案A中，大鼠接受2h再灌注，用来检测梗死面积。方案B中，大鼠接受10min再灌注，用Westcrn来检测P-Akt，Akt，P—GSK-3β，GSK．3β的表达；并且用分光光度法分析组织中烟酰胺腺嘌呤二核苷酸（NAD＋）水平，作为反映线粒体渗透性转换孔（mPTP）开放的指标。结果成年组大鼠，异氟醚预处理组（YISO＋I／R）心肌梗死面积为29．9％±1．9％，明显低于缺血再灌注组（YI／R，51．8％±2．1％，P〈0．001）。而老年组大鼠，异氟醚预处理失去心肌保护作用（OISO＋I／R--39．9％4-3．7％VSOI／R=46．9％±2．5％，P〉0．05）。比较成年阴性对照组（YSC组）和成年缺血再灌注组（YI／R组），异氟醚预处理显著提高了成年异氟醚组（YISO组）和成年异氟醚＋缺血再灌注组（YISO＋I／R组）的Akt和GSK-3B的磷酸化水平（P〈0．05）。但是老年组大鼠，Akt和GSK-39磷酸化水平已经在阴性对照组（osc组）提高（对比YSC组）。异氟醚预处理没有进一步提高老年异氟醚组（OISO组）和老年异氟醚＋缺血再灌注组（OISO＋I／R组）的Akt和GSK-3B的磷酸化水平（P〈0．05）。同样，异氟醚预处理减少了成年组大鼠心肌组织中NAD’的减少，而异氟醚预处理失去了对老年组大鼠的NAD＋流失保护作用。结论老年大鼠失去异氟醚预处理心肌保护作用，失去进一步提高Akt、GSK．3β的磷酸化水平能力和失去关闭mPTP是其机理之一。

Objective To investigate the age-associated effects of isoflurane preconditioning and activation of Akt signaling pathways.Methods Fisher 344 male rats were assigned to their respective age groups, young（Y）,or old（O）,and then to （n= 10） ischemia/reperfusion injury（I/R） or Isoflurane（ISO）＋I/R.After anesthesia, left anterior descending was occluded for 30min followed by 2h reperfusion.For ISO＋I/R group, rats were preconditioned with 1.0 MAC isoflurane for 30min followed by 15min washout.Five animals from each group were used for measure the infarction area. The expression of p-Akt and Akt were assessed by Western blotting.Results Isoflurane decreased myocardial infarction size while increased pAkt/Akt in young rats,whereas isoflurane did not significantly affect myocardial infarction size and the expression level of pAkt/Akt in old rats.Conclusion Male aged Fisher 344 lost cardioprotection after isoflurane preconditioning, which could be explained by age-related differences in the Akt pro-survival signaling pathway.