缺血预处理对心瓣膜置换术中心肌细胞Bcl-2及线粒体的影响

目的:研究体外循环下(CPB)心瓣膜置换术中缺血预处理(IP)对心肌细胞Bcl-2及线粒体的影响。方法:取2004年4月-2004年12月我院接受心脏瓣膜置换手术治疗的患者54例,随机分成2组,IP组(n=22):主动脉阻断前实行单次缺血2min和开放3min的IP方案,阻断主动脉后采用冷晶体心脏停搏液心肌保护进行手术;对照组(n=32):未进行IP方案,余步骤同IP组。比较2组术前和术后射血分数(EF)、短轴缩短百分率(FS)及每搏心输出量(SV)变化,观察肌钙蛋白T(c-TnT)、Bcl-2蛋白表达以及电镜下心肌细胞线粒体的改变。结果:对照组术后EF、FS及SV均较术前降低,P0.05;IP组术前后EF、FS及SV变化不明显,IP组术后6h、24h、48h、72h及第5dc-TnT水平均低于对照组,且随时间呈下降趋势;2组术前Bcl-2表达无显著差异(P0.05),术后IP组为19.85±5.88,较术前显著上升(P0.05);对照组为14.17±3.39,与术前无明显差别(P0.05)。术后2组Bcl-2表达具有显著差异(P0.05)。电镜观察:对照组心肌细胞线粒体肿胀,线粒体膜模糊不清,部分线粒体膜破裂;线粒体嵴明显疏松溶解,大量空泡形成;IP组心肌细胞线粒体膜基本完整,线粒体嵴密集,电子密度增高,无空泡形成。结论:IP可能上调心肌抗凋亡蛋白Bcl-2的表达,对心肌细胞线粒体起保护作用,减轻缺血再灌注对心肌细胞的损伤作用,一定程度上维护心脏功能。

Effect of ischemic preconditioning on myocardial Bcl-2 expression and mitochondrial structure during heart valve replacement surgery

AIM: To investigate the effect of ischemic preconditioning (IP) on myocardial Bcl-2 expression and mitochondrial structure during heart valve replacement surgery under cardiopulmonary bypass. METHODS: Fifty-four patients were prospectively randomized to receive or not ischemic preconditioning (IP) before cold cardioplegic arrest. Ischemic preconditioning in the IP patients (n=22) was induced by a single 2-min ischemia followed by 3-min reperfusion just before aortic clamping and cold crystalloid cardioplegia for myocardial protection. The control group (n=32) received no ischemic preconditioning before cold cardioplegic arrest. The levels of ejection fraction (EF), fractional shortening(FS) and stroke volume (SV) in both groups were measured and compared. troponin T (c-TnT) level, Bcl-2 protein expression and microscopic changes of myocardial mitochondrial structure were recorded for each group before and after surgery. RESULTS: The level of EF, FS and SV in IP group was higher than those in control group (P<0.05). No significant difference in preoperative c-TnT levels between two groups was observed. The level of c-TnT in IP group was lower than that in control group and with a declining trend over time of 6 h, 24 h, 48 h, 72 h and 5 d after surgery, respectively. The preoperative positive unit of Bcl-2 expression between two groups showed no statistical difference (P> 0.05). Postoperatively, the positive unit of Bcl-2 expression in IP group was 19.85±5.88, significantly increased as compared to the preoperative value (P<0.05). In control group, the positive unit of Bcl-2 expression was 14.17±3.39, showed no statistically significant difference to the preoperative value (P>0.05). Postoperative Bcl-2 expression between two groups showed a significant difference (P<0.05). In the control group, microscopic observation revealed swollen mitochondrion, with a hardly visible or disrupted membrane for some mitochondrion; mitochondrial crista were obviously dissolved and loose with a large number of vacuoles formation. However in IP group, myocardial mitochondrion appeared with intact membrane, concentrated mitochondrial cristae with high electron density and no vacuoles formation was observed. CONCLUSION: IP may up-regulate the expression of myocardial anti-apoptotic protein Bcl-2 to protect the mitochondrion, thus protecting cardiocytes and cardiac functions.