钙激活蛋白酶Ⅰ抑制剂对快速起搏犬心房结构重构的影响

Calpain Ⅰ inhibition prevents pacing-induced structural remodeling for atrial fibrillation in canine

目的观察钙激活蛋白酶Ⅰ(calpain Ⅰ)抑制剂对长期心房快速起搏致心房颤动犬的心房结构重构的影响。方法杂种犬15只,分为假手术组、起搏组、抑制剂组各5只。于犬右心耳缝置电极,起搏3周(600次/min)。起搏后抑制剂组每日给以 calpain Ⅰ抑制剂 N-Acetyl-Leu-Leu-Met(ALLM)1.0 mg·kg^(-1)·d^(-1)静脉注射,起搏组和假手术组给予等量溶剂二甲亚砜。采用荧光光度法测定心房肌 calpain Ⅰ活性,光镜观察肌溶解程度,电镜观察超微结构的变化,Western blot 技术测定心肌肌钙蛋白 T 蛋白含量,超声测定左心房容积的变化。结果起搏3周后,起搏组 calpain Ⅰ活性增加至假手术组的2.3倍(P<0.01),抑制剂组 calpain Ⅰ活性为假手术组的1.1倍(P>0.05);起搏组左心房肌溶解的比率为(76.7±5.9)%,抑制剂组左心房肌溶解的比率为(20.8±8.1)%,两组比较,P<0.01。calpain Ⅰ活性与肌溶解的比率呈高度正相关(r=0.89)。肌钙蛋白 T 蛋白含量在抑制剂组高于起搏组(P<0.01)。抑制剂组左心房容积的变化较起搏组显著减轻。结论 ALLM 通过抑制心房快速起搏犬心肌 calpain Ⅰ活性,防止了心房肌结构的改变,为心房颤动后心肌的保护提供了一种可能的有效途径。

Objective To study the relation of the structural remodeling processes and activation of calpain Ⅰ. Methods Fifteen dogs were randomly divided into three groups. The dogs in pacing group （n = 5） and inhibitor group （n = 5） were subjected to 3 weeks of rapid atrial pacing at 600 beats/min, control dogs （n = 5 ） were in sham-operated group. The dogs in inhibitor group were administered intravenous N- Acetyl-Leu-Leu-Met （ALLM）, a calpain inhibitor, and in pacing group and sham-operated group were administered intravenous DMSO. The activity of calpain Ⅰ was measured by hydrolyzing Suc-Leu-Leu-Val- Tyr- 7-amino-4-methyl-coumarin The ultrastructure of atrium was examined by light and electron microscopy. TnT expression was assessed by Western blot. Echocardiography examination was performed in all the three groups. Results Calpain Ⅰ activity was significantly increased in pacing group （2. 3-fold, P 〈 0.01）, and decreased in inhibitor group （1.1-fold, P 〉0.05 ）, compared to sham-operated group respectively. The percentages of myolysis were （76. 7 ± 5.9 ） % and （20. 8 ± 8. 1 ） % in pacing group and inhibitor group respectively （P 〈 0. 01 ）. TnT expression decreased in the rapid pacing-induced persistent atrial fibrillation, and these effects were inhibited by calpain Ⅰ inhibitor ALLM. The area and volume of left atrium tended to increase after 3 weeks ALLM treatment in inhibitor group, but the change was not as prominent as in pacing group （P 〈 0. 05 ）. Conclusions ALLM can decrease calpain Ⅰ activity, and prevent canine atrial cardiomyocyte structural remodeling during atrial fibrillation. This study provided a capacity of atrial cardiomyocyte protection.