[Protective effect and mechanism of AKAP1 on myocardial injury induced by highland hypobaric hypoxia].

Objective: To investigate the protective effect and its possible mechanism of A-kinase anchored protein 1 (AKAP1) on the myocardial injury induced by highland hypobaric hypoxia. Methods: From January 2021 to May 2022, male C57BL/6 SPF grade mice were divided into wild type control (WT) group and highland hypobaric hypoxia (HH) group with 6 mice in each group. HH group simulated 6000 m altitude with low pressure oxygen chamber for 4 weeks to build the model. Primary myocardial cells of SD rats were divided into normoxia control group and hypoxia experimental group (n=3). Cell models were constructed in a three-gas hypoxia incubator with 1% oxygen concentration for 24 h. AKAP1 protein and mRNA expression in myocardial tissue and cells were detected by western blotting, immunohistochemistry and quantitative real-time polymerase chain reaction (qPCR). After myocardial point injection of the AKAP1 or the control adenovirus, the mice were divided into 3 groups (n=6) : WT group, highland hypobaric hypoxia overexpression control group (HH+Ad-Ctrl group) and highland hypobaric hypoxia overexpression experimental group (HH+Ad-AKAP1 group). The cardiac function of mice was detected by noninvasive M-type ultrasonic cardiomotive, myocardial fibrosis was detected by Masson and Sirius Red staining, and cardiomyocyte hypertrophy was detected by wheat germ agglutinin. After the expression of AKAP1 in primary cardiomyocytes was downregulated by siRNA and upregulated by adenovirus, the cells were divided into three groups (n=3) : normoxia control group, hypoxia interference control group (hypoxia+siCtrl group), hypoxia AKAP1 knockdown group (hypoxia+siAKAP1 group) ; normoxia control group, hypoxia overexpression control group (hypoxia+Ad-Ctrl group), hypoxia AKAP1 overexpression group (hypoxia+Ad-AKAP1 group). Apoptosis was detected by flow cytometry, AKAP1, apoptosis-related protein and mRNA expression levels were detected by western blotting and qPCR, mitochondrial membrane potential was detected by JC-1 staining, and mitochondrial reactive oxygen specie (ROS) level was detected by MitoSOX. Results: The expression of AKAP1 in cardiac muscle of HH group was lower than that in the WT group, and the expression of AKAP1 in hypoxia experimental group was lower than that in normoxia control group (P<0.01). Compared with WT group, the left ventricular ejection fraction and fraction shortening of left ventricle in HH+Ad-Ctrl group were decreased (P<0.01), myocardial fibrosis and hypertrophy were aggravated (P<0.01), and the expression of B-cell lymphoma-2 (BCL-2) was decreased, the expressions of BCL-2-associated X protein (BAX), Caspase 3 and Caspase 9 were increased (P<0.01). After AKAP1 overexpression, compared with HH+Ad-Ctrl group, the left ventricular ejection fraction and left ventricular fraction shortening were increased in HH+Ad-AKAP1 group (P<0.01), myocardial fibrosis and hypertrophy were reduced (P<0.01), and the expression of BCL-2 was increased, the expressions of BAX, Caspase 3 and Caspase 9 were decreased (P<0.01). Compared with normoxia control group, the expression of BCL-2 in hypoxia+siCtrl group was decreased, the expressions of BAX, Caspase 3, Caspase 9 were increased, the apoptosis level was increased (P<0.01), the mitochondrial membrane potential was decreased and the production of ROS was increased (P<0.01). After AKAP1 knockdown, compared with hypoxia+siCtrl group, the expression of BCL-2 in hypoxia+siAKAP1 group was decreased, the expressions of BAX, Caspase 3, Caspase 9 were increased, the apoptosis level was increased (P<0.01), mitochondrial membrane potential was decreased, and the production of ROS was increased (P<0.01). After AKAP1 overexpression, compared with hypoxia+Ad-Ctrl group, the expression of BCL-2 in hypoxia+Ad-AKAP1 group was increased, the expressions of BAX, Caspase 3 and Caspase 9 were decreased (P<0.05), the apoptosis level was decreased (P<0.01), and the mitochondrial membrane potential was enhanced, and the production of ROS was decreased (P<0.01) . Conclusion: The downregulation of AKAP1 in cardiomyocytes under highland hypobaric hypoxia may lead to the decrease of mitochondrial membrane potential and the increase of ROS generation, leading to the apoptosis of cardiomyocytes, and thus aggravating the myocardial injury at highland hypobaric hypoxia.目的： 探讨A型激酶锚定蛋白1（A-kinase anchored protein1，AKAP1）在高原低压低氧环境导致心肌损伤中的保护作用及可能机制。 方法： 于2021年1月至2022年5月，将SPF级雄性C57BL/6小鼠分为常氧野生对照（wild type，WT）组及高原低压低氧实验（hypobaric hypoxia，HH）组，各6只小鼠；HH组用动物实验低压氧舱模拟6 000 m海拔持续4周构建模型。分离SD大鼠乳鼠原代心肌细胞后分为常氧对照组及低氧实验组（n=3），用三气低氧培养箱以1%氧浓度低氧24 h构建细胞模型。用蛋白质印迹法、免疫组化及实时荧光定量聚合酶链反应检测心肌组织和细胞中AKAP1蛋白及mRNA表达。心肌点注射AKAP1或对照腺病毒后将小鼠分3组（n=6）：WT组、高原低压低氧过表达对照组（HH+Ad-Ctrl组）、高原低压低氧过表达实验组（HH+Ad-AKAP1组）。用无创M型超声心动机检测小鼠心脏功能，马松及天狼猩红染色检测心肌纤维化程度，麦胚凝集素检测心肌细胞肥大状况。用siRNA干涉或腺病毒上调原代心肌细胞AKAP1表达后将细胞分3组（n=3）：常氧对照组，低氧干涉对照组（低氧+siCtrl组），低氧AKAP1敲低组（低氧+siAKAP1组）；常氧对照组，低氧过表达对照组（低氧+Ad-Ctrl组），低氧AKAP1过表达组（低氧+Ad-AKAP1组）。用流式细胞术检测细胞凋亡，蛋白质印迹法及实时荧光定量聚合酶链反应检测AKAP1、凋亡相关蛋白及mRNA的表达水平，JC-1染色检测线粒体膜电位，MitoSOX检测线粒体活性氧水平。 结果： HH组小鼠心肌AKAP1表达低于WT组，低氧实验组细胞AKAP1表达低于常氧对照组（P<0.01）。与WT组比较，HH+Ad-Ctrl组小鼠左心室射血分数及左心室短轴缩短率降低（P<0.01），心肌纤维化及肥大程度加重（P<0.01），B细胞淋巴瘤-2（B-cell lymphoma-2，BCL-2）降低，BCL-2相关X蛋白（BCL-2-associated X protein，BAX）、半胱氨酸天冬氨酸蛋白酶3（Caspase 3）、半胱氨酸天冬氨酸蛋白酶9（Caspase 9）表达升高（P<0.01）。过表达AKAP1后，与HH+Ad-Ctrl组比较，HH+Ad-AKAP1组小鼠左心室射血分数及左心室短轴缩短率升高（P<0.01），心肌纤维化及肥大程度减轻（P<0.01），BCL-2表达升高，BAX、Caspase 3、Caspase 9表达下降（P<0.01）。与常氧对照组比较，低氧+siCtrl组大鼠原代心肌细胞BCL-2表达降低，BAX、Caspase 3、Caspase 9表达升高，凋亡水平增加（P<0.01），线粒体膜电位降低，活性氧生成增加（P<0.01）。敲低AKAP1后，与低氧+siCtrl组比较，低氧+siAKAP1组细胞BCL-2表达降低，BAX、Caspase 3、Caspase 9表达升高，凋亡水平增加（P<0.01），线粒体膜电位降低，活性氧生成增加（P<0.01）。过表达AKAP1后，与低氧+Ad-Ctrl组比较，低氧+Ad-AKAP1组细胞BCL-2表达升高，BAX、Caspase 3、Caspase 9表达降低（P<0.05），凋亡水平降低（P<0.01），线粒体膜电位增强，活性氧水平降低（P<0.01）。 结论： 高原低压低氧条件下心肌细胞AKAP1下调，可能导致线粒体膜电位降低、活性氧生成增加，引发心肌细胞凋亡，从而加重高原低压低氧心肌损伤。.