中国科学院昆明动物研究所机构知识库

心律失常是常见的心血管疾病之一，其种类繁多，病情复杂，严重者可导致患者猝死。世界心律失常大会公布的统计数字显示，亚太地区心血管病发病率呈逐年上升趋势，而中国心律失常患者已经超过两千万人，每年约54万人因心源性猝死。在世界范围内心血管疾病引起的死亡人数达到一千多万人，而其中约有25 % 的死者是心源性猝死。引起心源性猝死的最常见原因是致命性心律失常，如心室颤动、心室扑动、室性尖端扭转心动过速等。因此，心律失常疾病不容忽视。目前关于抗心律失常的药物众多，针对多种适应症具有良好的疗效。然而，现存的抗心律失常药物存在着许多弊端，可能在治疗心律失常的同时对心脏或其它组织存在潜在的危害性。因此，在开发抗心律失常药物的过程中，探索安全有效的药物是目前的首要任务。心律失常主要是由于心肌细胞膜上离子通道功能异常导致动作电位改变，进而引发心脏功能障碍。本课题旨在探讨以离子通道为靶点的两个潜在化合物的抗心律失常功效及机制。本课题利用计算机模拟筛选系统和天然化合物筛选流程，以多种与心肌相关的离子通道为靶点，筛选出两个活性化合物，分别是合成化合物C20和天然产物克班宁。本课题从分子水平、组织水平和动物水平上对这两个化合物的抗心律失常作用进行探索研究。1. C20抗心律失常作用的研究在计算机数学模拟系统中，选定KCNQ1钾通道的电压感受器（voltage sensor） 为作用靶点，筛选出可能与目的靶点位置结合的一批化合物。在功能验证实验中发现C20能够显著影响KCNQ1/KCNE1通道的电压门控特性，引发激活曲线左移，导致通道更容易开放。体外表达与心肌相关离子通道检测实验结果表明，在一定浓度下C20具有较强的特异性，仅对KCNQ1/KCNE1通道具有明显激活作用。在组织水平上，将C20作用于豚鼠左心室肌细胞，可有效缩短豚鼠心肌细胞动作电位的时长，并且能够逆转多非利特引发的豚鼠心室肌动作电位的延长，使动作电位恢复至正常时长。建立家兔的长QT间期综合征心律失常动物模型，心电图上可观察到造模兔出现明显的QT间期延长、心室尖端扭转心动过速（TdP）等心律失常表征。静脉注射C20注射剂给造模兔并观察其抗心律失常作用，结果表明5mg/kg C20 能够有效的改善造模兔的心律失常病症，约10分钟后家兔的心电图即可恢复正常，QT间期亦恢复到正常范围。本课题从离子通道水平、心肌组织动作电位水平和整体动物水平三个方面阐述C20的抗心律失常作用及机制。2. 克班宁抗心律失常作用的研究克班宁是从云南地不容中提取出的天然产物。云南地不容（Stephania. yunnanensis. H.S. Lo）是山乌龟亚属（Subgen. Tuberiphania Lo et M. Yang）中多年生藤本植物，山乌龟亚属系防已科（Menispermaceae）千金藤属（Stephania Lour.）山乌龟亚属（Subgen. Tuberiphania Lo）地不容组（Sect. Tanscostula Lo et M. Yang），在云南分布广泛，块根发达，富含生物碱等活性成分。在体外离子通道表达系统上，克班宁对心肌相关离子通道具有广谱的抑制作用，对心肌细胞上的钠通道、钾通道和钙通道均具有抑制作用。同时，克班宁可缩短豚鼠心室肌细胞动作电位时长，加快心肌细胞动作电位复极化，具有浓度依赖性。建立乌头碱诱发的家兔心律失常模型，主要表现为室性早搏、室性扑动、室性二联律、房室传导阻滞等恶性心律失常。结果表明静脉注射低、中、高剂量的克班宁均能够有效改善乌头碱诱发的心律失常，使心电图逐渐恢复正常。综上所述，我们首次发现并探讨了C20和克班宁的抗心律失常作用。研究提示C20可能通过改变单一通道的门控特性来发挥其抗心律失常作用，而克班宁则通过抑制多种离子通道达到其协同的抗心律失常作用。C20和克班宁分别代表合成化合物和传统天然产物的活性特点，可作为先导分子为抗心律失常药物的深层开发利用提供进一步参考依据，在天然产物开采和应用中具有重要的意义。 

Arrhythmia is one of the most common cardiovascular diseases, which cause more than 10 million death worldwide each year, with ~25% of them being caused by sudden cardiac death. Statistics released by the World Congress of Cardiology show that the incidence of cardiovascular diseases in the Asia-Pacific region has been increasing year by year. In China, the number of people suffering from arrhythmias has exceeded 20 million, and each year more than half a million people die from sudden cardiac death. The most common cause of sudden cardiac death is fatal arrhythmia, such as ventricular fibrillation, ventricular flutter, and ventricular tachycardia torsade de pointes (TdP). Currently a variety of anti-arrhythmia medicines are on the market. However, many existing anti-arrhythmic drugs have various drawbacks, including systemic side effects and potential harm to the heart and other organs. Searching for new antiarrhythmic medicines with high efficacy and low side effects is of great public interest and clinical importance.In this study, we used a combination of computer simulation and functional screening to search for novel synthetic and natural compounds that affect cardiac ion channel activities and produce antiarrhythmic effects. We identified two compounds, namely the synthetic compound C20 and the natural product crebanine. We studied their actions and antiarrhythmic mechanisms at the molecular, cellular and animal levels.1. The antiarrhythmic effect of C20In a computer simulation, we obtained a number of synthetic compounds that target the voltage sensor of the KCNQ1 potassium channel, including a molecule named C20. In vitro functional assays showed that at a concentration of 30 μM C20 significantly increased the activity of the KCNQ1/KCNE1 channel but had little effect on other types of potassium channels. C20 greatly shifted the activation curve of KCNQ1/KCNE1 to the left, making the channel easier to open. In guinea pig ventricular myocytes C20 shortened the action potential duration and reversed the action potential prolongation caused by dofetilide. In a rabbit arrhythmia model, 5mg/kg C20 (iv) effectively reversed the arrhythmia in 10 minutes.2. The antiarrhythmic effect of crebanineCrebanine is a natural product extracted from Stephania. Yunnanensis. H.S. Lo. In heterologous expression systems, crebanine inhibited a variety of cardiac ion channels, including voltage-gated sodium, potassium and calcium channels. Crebanine shortened the action potential duration in guinea-pig ventricular myocytes and changed the waveform of the action potentials. In a rabbit arrhythmia model induced by aconitine, which causes ventricular premature beating, ventricular flutter, atrioventricular block and other malignant arrhythmia, various doses of crebanine were able to effectively reverse the arrhythmia caused by aconitine.In summary, in this study we describe and investigate the antiarrhythmic effects of C20 and crebanine. Our results suggest that C20 exerts its antiarrhythmic effect by altering the gating properties of a single ion channel, while crebanine produces its antiarrhythmic effect by synergistically inhibiting multiple ion channels. Their different modes of action may be representative of synthetic compounds and natural products and offer mechanistic insights into the antiarrhythmic effects of these two classes of molecules. Crebanine may provide a starting point for the development of a new antiarrhythmic medicine.