基于不同钙释放机理的花萼海绵诱癌素A与去乙酰毛花苷的正性肌力作用研究

Comparative Studies of Calyculin A and Deslanoside on Rat Isolated Heart Inotropy and Their Underlying Mechanism

目的与洋地黄类正性肌力代表药去乙酰毛花苷比较,研究蛋白磷酸酶(PP)抑制剂花萼海绵诱癌素A(Calyculin A)对心脏收缩力作用特点,分析Calyculin A正性肌力作用的钙释放机理。探讨能否以PP为靶点,开发正性肌力药物治疗心力衰竭。方法分别用Calyculin A(1,4,10nmol/L)和去乙酰毛花苷(0.1,1,10μmol/L)对大鼠离体心脏灌流,分析大鼠心率(HR)、左心室舒张压(LVDP)和最大上升速率(+dp/dtmax)的变化。采用Calyculin A(100nmol/L)和去乙酰毛花苷(10μmol/L)对大鼠左心室心肌细胞进行灌流,测定钙释放幅值、舒张期胞浆钙浓度(Ibaseline)及胞浆钙浓度恢复到静息状态值50%水平的时间(CTD50);分析Calyculin A(100nmol/L)和去乙酰毛花苷(10μmol/L)对咖啡因(20mmol/L)诱导的大鼠心肌细胞钙释放的影响,分析肌浆网钙泵活性(SERCA2a)、钠-钙交换体(NCX)及肌膜钙泵(PMCA)综合活性的变化。结果 Calyculin A(1,4,10nmol/L)与去乙酰毛花苷(0.1,1,10μmol/L)均能显著增加离体大鼠LVDP和+dp/dtmax(P<0.05),且减慢HR(P<0.05),并呈现浓度依赖性。Calyculin A(100nmol/L)与去乙酰毛花苷(10μmol/L)均显著增加钙释放幅值(P<0.05);Calyculin A还能显著降低Ibaseline(P<0.05),显著缩短CTD50(P<0.05)。Calyculin A(100nmol/L)显著增加肌浆网SERCA2a的速率常数(P<0.05);去乙酰毛花苷(10μmol/L)增加(NCX+PMCA)的速率常数(P<0.05),导致肌浆网SERCA2a在胞浆回吸收中所发挥作用的百分比下降(P<0.05)。结论 Calyculin A与去乙酰毛花苷对大鼠离体心脏作用没有显著区别,但Calyculin A通过增强肌浆网SERCA2a的活性,增加钙释放幅值并降低Ibaseline实现其正性肌力作用。Calyculin A的作用靶点PP,可作为一个潜在靶点用于开发正性肌力药物。

OBJECTIVE To investigate the inotropic effect and its underlying mechanism of calyculin A,a protein phosphatase(PP)inhibitor,compared to deslanoside,a digitalis positive inotropic agent.To provide inputs whether PP can be served as a potential therapeutic target to develop pharmacological inotropic agents in treatment of heart failure.METHODS Ex vivo study was used to record the effects of calyculin A and deslanoside on rat isolated contractilities.They were perfused to follow in order:normal perfusion solution→calyculin A(1,4,10 nmol/L)or normal perfusion solution→deslanoside(0.1,1,10μmol/L).Ca 2+transients triggered by field stimulation and by caffeine(20 mmol/L)were measured to analyze the Ca 2+handling effects of calyculin A(100 nmol/L)and deslanoside(10μmol/L).RESULTS Both calyculin A(1,4,10 nmol/L)and deslanoside(0.1,1,10μmol/L)significantly increased the left ventricular developed pressure and the peak rate of rise of left pressure(P<0.05)and decreased the heart rate(P<0.05).Calyculin A(100 nmol/L)and deslanoside(10μmol/L)significantly increased the amplitude of Ca 2+transient and shortened the Ca 2+transient duration at 50%full recovery level(P<0.05);Calyculin A also lowered diastolic cytoplasm Ca 2+concentration(P<0.05).Calyculin A(100 nmol/L)significantly increased the SERCA2a activity and combinational activities of Na+Ca 2+exchanger(NCX)and plasma membrane Ca 2+ATPase(PMCA)(P<0.05);Deslanoside(10μmol/L)only increased combinational activities of NCX and PMCA(P<0.05),resulting in lowering percentage of contribution of SERCA2a in Ca 2+reuptake phase of Ca 2+transient(P<0.05).CONCLUSION Calyculin A increases the amplitude of Ca 2+transient by enhancing activity of SERCA2a and combinational activities of NCX and PMCA,resulting in the positive inotropy and favorable relaxation.PP can be a potential therapeutic target to develop pharmacological inotropic agents in treatment of heart failure.