长期耐力运动对大鼠右心室MMP-2和TIMP-2的影响

Effects of Long-term Endurance Exercise on the Right Ventricular MMP-2 and TIMP-2 of Rats

目的:通过建立长期大强度运动模型,研究长期不同强度耐力运动对大鼠右心室心功能和羟脯氨酸的含量影响以及基质金属蛋白酶2(matrix metalloproteinase-2,MMP-2)和金属蛋白酶抑制剂2(tissue inhibitor of metalloproteinase-2,TIMP-2)的调节作用,为运动性心肌纤维化和心律失常的发生机制提供实验依据。方法:24只健康成年雄性SD大鼠随机分为安静对照组、中强度运动组和大强度运动组,每组8只。中强度组和大强度组进行16周的运动,每周训练5天,休息2天,每次1 h。16周后采用小动物超声心动仪检测大鼠右心室心功能。随后,立刻麻醉处死大鼠,摘取心脏,分离出右心室。采用样本碱水解法检测羟脯氨酸的含量;荧光定量PCR检测MMP-2和TIMP-2 m RNA的相对表达。Western Blot检测MMP-2和TIMP-2蛋白的表达。结果:(1)与安静组相比,中强度组右室射血分数(RVEF)和右室缩短分数(RVFS)增加,但无显著性差异。大强度组RVEF显著低于安静组和中强度组(P<0.05),大强度组RVFS均低于安静组和中强度组,但无显著性差异。(2)中强度组羟脯氨酸的含量高于安静对照组,但无显著性差异;而大强度组羟脯氨酸的含量显著高于安静组和中强度组(P<0.01)。(3)与安静组相比,中强度组MMP-2 m RNA和蛋白的表达具有增加趋势,但无显著性差异。大强度组MMP-2 m RNA的表达显著高于安静组(P<0.05),大强度组MMP-2蛋白的表达显著高于安静组和中强度组(P<0.01);与安静组比较,中强度组和大强度组TIMP-2 m RNA的表达均无显著性差异;通过计算发现,三组间MMP-2/TIMP-2m RNA的比值无明显差异,大强度组MMP-2/TIMP-2蛋白的比值显著高于安静组和中强度组(P<0.01)。结论:长期大强度运动造成大鼠右心室羟脯氨酸含量显著增加,心肌MMP-2的表达增加,MMP-2/TIMP-2比例失调可能是右心室心功能异常和运动性心肌纤维化的发生机制之一。

Objective To explore the effects of long-term exercise on the content of hydroxyproline and right ventricular function,and to investigate the role of matrix metalloproteinase-2（MMP-2）and matrix metalloproteinase tissue inhibitor-2（TIMP-2）during the exercise in order to provide experimental evidence for clarifying the mechanism of exercise-induced myocardial fibrosis and arrhythmia. Methods 24 SD rats were divided into control group（C）,moderate intensity exercise group（M,15.2 m/min,5° slope）and high intensity exercise group（H,28 m/min,10° slope）. Rats in groups M and H were conditioned to run 1 hour per day,5 days per week for a total of 16 weeks. The right ventricular function of the rats was measured by echocardiography. The rats were euthanized within 24 h after the last exercise,and their right ventricles were collected. Ventricular hydroxyproline was measured by alkaline hydrolysis method. MMP-2 and TIMP-2 gene expression were evaluated by real-time PCR. MMP-2 and TIMP-2 proteins were quantified by Western Blot.Results（1）There was significant difference in ventricular ejection fraction（RVEF）between group H and groups C and M（P〈0.05）,and insignificant difference in RVEF and right ventricular fractional shortening（RVFS）between group C and group M,and in RVFS between group H and groups C and M.（2）There was significant difference in hydroxyproline content between group H and groups C and M（P〈0.01）,while insignificant difference between group C and group M.（3）There was significant difference in the expression of MMP-2m RNA between group H and group C（P〈0.05）,and in the expression of MMP-2 protein between group C and group H（P〈0.01）,while insignificant difference between group H and group C. Though there was no significance in the MMP-2/TIMP-2 m RNA and MMP-2/TIMP-2 m RNA among the three group,while significant significance in the MMP-2/TIMP-2 m RNA between group H and groups C and M（P〈0.01）.Conclusion Long-term intensive exercise induce increase in hydroxyproline content in right ventricle of rats,resulting in right ventricular dysfunction,increased MMP-2,and disproportionality of MMP-2/TIMP-2,which probably is one of the factors that cause the exercise-induced cardiac dysfunction and arrhythmia.