高位脊髓损伤对大鼠心肌细胞线粒体电压依赖性阴离子通道2表达的影响

Effect of high-level spinal cord injury on expression of mitoehondrial voltage-dependent anion channel 2 in rat cardiomyocytes

目的评价高位脊髓损伤对大鼠心肌细胞线粒体电压依赖性阴离子通道2（VDAC2）表达的影响。方法清洁级健康成年雄性SD大鼠48只，体重200～250g。采用随机数字表法分为2组（n=24）：假手术组（s组）和高位脊髓损伤组（H组）。H组采用Allens打击法，制备大鼠高位脊髓损伤模型，S组只暴露脊髓，不进行打击。于打击后6、12、24和48h（T1-4）时各组随机取6只大鼠麻醉后处死，剪取心尖部心肌组织，透射电镜下观察心肌细胞形态学；采用原位末端标记法检测心肌细胞凋亡率；分别采用Westernblot法和RT—PCR法检测心肌细胞Bax、Bcl-2和VDAC2及其mRNA的表达水平，计算Bax／Bcl-2蛋白及其mRNA比值。结果与S组比较，H组T1-4时细胞凋亡率和Bax／Bcl-2蛋白及其mRNA比值升高，T2-4时VDAC2及其mRNA表达下调（P〈0．05或0．01），心肌细胞病理学损伤加重。结论高位脊髓损伤大鼠心肌损伤的机制与心肌细胞线粒体VDAC2表达下调，促进细胞凋亡有关。

Objective To evaluate the effect of high-level spinal cord injury （SCI） on the expres- sion of mitochondrial voltage-dependent anion channel 2 （VDAC2） in rat cardiomyocytes. Methods For- ty-eight pathogen-free healthy adult male Sprague-Dawley rats, weighing 200-250 g, were divided into 2 groups （n= 24 each） using a random number table： sham operation group （group S） and high-level SCI group （group H）. The animals were anesthetized with intraperitoneal chloral hydrate and subjected to SCI using the modified Allen weight-drop method in group H. The spinal cord was only exposed in group S. At 6, 12, 24 and 48 h after SCI （T1-4） , 6 rats in each group were randomly selected and sacrificed, and myocardial specimens were collected from the cardiac apex for microscopic examination of the cell morpholo- gy （with a transmission electron microscope） and for determination of cell apoptosis （by TUNEL assay） , expression of Bax, Bcl-2 and VDAC2 protein and mRNA in cardiomyocytes （ by Western blot and real-time polymerase chain reaction, respectively）. The apoptosis rate and ratios of Bax/Bci-2 protein and mRNA were calculated. Results Compared with group S, the apoptosis rate and ratios of Bax/Bcl-2 protein and mRNA were significantly increased at T1-4, the expression of VDAC2 protein and mRNA was significantly down-regulated at T2-4 （P〈0.05 or 0.01 ） , and the pathologic changes of cardiomyocytes were aggravated in group H. Conclusion The mechanism of myocardial damage is related to down-regulation of mitochondrial VDAC2 expression in cardiomyocytes and promotion of cell apoptosis in rats with high-level SCI.