缺血预适应改善猪急性心肌梗死再灌注后无复流和再灌注损伤的作用与通过蛋白激酶A通路减轻心肌水肿有关

Ischemic preconditioning attenuates myocardial no-reflow and reperfusion injury after revascularization of acute myocardial infarction by reducing myocardial edema via the protein kinase A pathway

目的心肌水肿在急性心肌梗死（AMI）冠状动脉再通治疗后心肌无复流和再灌注损伤的发展过程中起重要作用。本实验拟探讨缺血预适应（IPC）减轻心肌无复流和再灌注损伤的作用是否与减轻心肌水肿有关，以及这一作用是否受蛋白激酶A（PKA）通路的调节。方法小型猪24只，随机分为假手术组、心肌梗死（MI）组、IPC组和IPC＋H-89（PKA抑制剂，1．0μg·kg^-1·min^-1）组，每组6只。病理染色法测定心肌无复流和心肌坏死面积，干湿重法测定心肌组织含水量，荧光定量法测定毛细血管渗透性，苏木素伊红染色测定心肌细胞横切面面积，电镜下测定线粒体横切面面积，免疫印迹法测定心肌水通道蛋白（AQP）的表达。结果IPC组心肌无复流和梗死面积较MI组分别小31．9％和46．6％（P均〈0．01），IPC组复流区和无复流区心肌组织含水量较MI组分别低5．7％和4．6％（P均〈0．05），IPC组复流区毛细血管渗透性较MI组低29．8％（P〈0．01），IPC组复流区心肌细胞横切面面积较MI组小21．3％（P〈0．01），IPC组复流区和无复流区心肌细胞线粒体横切面面积较MI组分别小45．5％和34．8％（P均〈0．01），IPC组复流区和无复流区水通道蛋白－4、－8和－9的表达较MI组低。而在IPC＋H－89组IPC的这些作用被部分抑制。结论IPC可减轻AMI再灌注后心肌无复流和再灌注损伤，其机制与降低血管渗透性、抑制水通道蛋白表达，从而减轻心肌水肿有关，而IPC的这一作用部分受PKA通路调节。

Objective Myocardial edema plays an important role in the development of myocardial no-reflow and reperfusion injury after the revascularization of acute myocardial infarction （AMI）. The present study investigated whether the effect of ischemic preconditioning （IPC） against myocardial no-reflow and reperfusion injury was related to the reduction of myocardial edema through the protein kinase A （PKA） pathway. Methods Twenty-four minipigs were randomized into sham, AMI, IPC, and IPC ＋ H-89 （ PKA inhibitor, 1.0 μg·kg^-1·min^-1） groups. The area of no-refiow （ANR） , area of necrosis （AN） , and water content in left ventricle and ischemic-myocardium and non-ischemic area were determined by pathological studies. Microvascular permeability was determined by FITC-labeled dextran staining. Cardiomyocyte cross-sectional area （CSA） and mitochondria cross-sectional area （MSA） were evaluated by histological analysis. Myocardial expression of aquaporins （AQPs） was detected by Western blot. Results Compared with the MI group, the sizes of no-reflow and infarct were reduced by 31.9% and 46. 6% in the IPC group （all P 〈0. 01 ）, water content was decreased by 5.7% and 4. 6% in the reflow and no-reflow myocardium of the IPC group （ all P 〈 0. 05 ）, microvascular permeability and cardiomyocytes swelling in the reflow area were inhibited by 29. 8% and 21.3% in the IPC group （ all P 〈 0. 01 ）, mitochondrial water accumulation in the reflow and no-reflow areas of the IPC group were suppressed by 45.5% and 34. 8% respectively （ all P 〈 0. 01 ）, and the expression of aquaporin-4, -8, and -9 in the reflow and no-reflow myocardium were blocked in the IPC group. However, these beneficial effects of IPC were partially abolished in the IPC ＋ H-89 group. Conclusions The cardioprotective effects of IPC against no-reflow and reperfusion injury is partly related to the reduction of myocardial edema by inhibition of microvascular permeability and aquaporins up-regulation via PKA pathway.