大鼠急性心肌梗死后的心肌细胞凋亡和凋亡相关基因表达的变化

Cardiomyocyte apoptosis and related gene expression after acute myocardial infarction in rats

目的:观察大鼠急性心肌梗死(AM I)后的心肌细胞凋亡和caspase-3、Bc l-2和Bax表达的变化。方法:105只雌性SD大鼠,随机取78只结扎左冠状动脉建立AM I模型,24 h存活43只作为心肌梗死组(M I组);另27只设为假手术组(S组);两组再按观察时点随机分为48 h和4周两亚组,即:M I 48 h(n=11)和M I 4周(n=13)组,S48 h(n=10)和S4周(n=10)组。末端脱氧核糖核苷酸转移酶介导的dUTP切口末端标记技术(TUNEL)和DNA凝胶电泳检测心肌细胞凋亡。免疫组化方法和W estern b lotting检测caspase-3、Bc l-2和Bax的表达。结果:M I 48 h组动脉收缩压(SBP)、舒张压(DBP)、平均压(MAP)、左心室收缩压(LVSP)和左心室内压最大上升下降速率(±dp/dt)均显著低于S组(P<0.05,P<0.01),左心室舒张末压(LVEDP)显著高于S组(P<0.05);M I 4周组除SBP、DBP和MAP无显著差异(均P>0.05)外,上述其它指标的变化与M I 48 h组相同,且LVEDP升高更为显著(P<0.01);M I 48 h和4周两组梗死/疤痕区、梗死边缘区和非梗死区的心肌细胞凋亡指数均显著升高(P<0.05,P<0.01),心肌细胞中“凋亡执行因子”caspase-3和“凋亡促进基因”Bax的表达亦均显著增高(P<0.05,P<0.01),而“凋亡抑制基因”Bc l-2仅在M I 48 h组梗死区心肌细胞中表达增加,“抑制凋亡复合基因”Bc l-2/Bax的比值仅在M I 48 h组降低。结论:大鼠AM I后,梗死区及其边缘区和非梗死区均有心肌细胞凋亡发生,伴“凋亡执行因子”caspase-3和“凋亡促进基因”Bax的表达增加;AM I早期,“凋亡抑制基因”Bc l-2在梗死区表达增加,但“抑制凋亡复合基因”Bc l-2/Bax的比值下降。

AIM： To investigate cardiomyocyte apoptosis and the expression of caspase -3, Bcl -2 and Bax af- ter acute myocardial infarction （AMI） in rats. METHODS： AMI model was established with the ligation of left coronary ar- tery in 78 randomly selected female SD rats. Twenty - four hours after operation, 43 survivors were randomly divided into 48 - hour and 4 - week two groups according to the time points ： MI 48 h （ n = 11 ） and MI4 weeks （ n = 13 ） groups, sham - operated rats （S, n = 27） were also randomly selected and reassigned to $48 h （ n = 10） and $4 weeks （ n = 10） groups. Cardiomyocyte apoptosis was detected with in situ terminal deoxynucleotidyl transferase （TdT） - dUTP nick - end labeling （TUNEL staining） and DNA gel electrophoresis. Caspase -3, Bcl -2 expression and Bax expression were detected with im- munohistochemistry and Western blotting analysis. RESULTS： Compared with sham -operated group, after AMI, systolic, diastolic, and mean arterial blood pressures （SBP, DBP, MAP）, left ventricular systolic pressure （LVSP） and the maximum change rate of left ventricular pressure rise and fall （ ＋ dp/dt） were significantly decreased （ P 〈 0. 05, P 〈 0. 01 ）, while left ventricular end diastolic pressure （LVEDP） was significantly increased （P 〈0. 05） in MI 48 h group. All the a- bove indices in MI 4 weeks group had the same change as that in MI48h group, with the LVEDP significantly higher （P 〈 0. 01 ）, except for a non - significantly change in SBP, DBP and MAP （ all P 〉 0. 05）. In both MI 48 h and MI 4 weeks groups, myocyte apoptotic index was significantly increased in the infracted/scar, border and non -infarcted areas （P 〈 O. 05, P 〈 O. O1 ） with caspase - 3 and Bax expressions increased significantly （ P 〈 O. 05, P 〈 0. O1 ） in myocytes of the a- bove three areas and Bcl - 2 expression increased only in myocytes of the infracted area in MI 48 h group. Western blotting indicated that Bcl - 2/Bax ratio was also decreased in MI 48 h subgroup. CONCLUSIONS ： After AMI in rats, cardiomyo- cyte apoptosis happened in the infarction/scar, border and non - infarcted areas, with caspase - 3 and Bax expression in myocytes increased, and with Bcl -2 expression increased in myocytes of infracted area and Bcl -2/Bax ratio decreased only early after AMI.