CaMKⅡ 在心血管疾病中作用的研究进展

钙离子/钙调素依赖性蛋白激酶Ⅱ（CaMKⅡ）具有多重作用,并在心血管事件中有着举足轻重的地位。特别是其可以作用于多种分子信号通路中的下游靶点,促进血管疾病、心衰、心肌肥厚和心律失常发生发展。CaMKⅡ通过磷酸化L型钙通道,兰尼碱受体（RyR2）和受磷蛋白（PLN）等多种钙调蛋白能够影响心肌细胞钙平衡、增加钙渗漏,亦可影响钠通道及钾通道,调节晚钠电流及ATP敏感性钾电流IKATP。此外更可直接通过激活丝裂原活化蛋白激酶（MAPKs）及脱乙酰化酶（HDAC）影响心肌细胞转录调控。而这些机制在心肌肥厚、心力衰竭、心律失常的发生发展中都有着重要作用。因此深入了解CaMKⅡ的结构与作用机制将有助于制定新的心血管疾病治疗策略。     

阿片受体激动剂U50,488H通过Cx43介导的抗心律失常作用与抑制钙通道有关

目的研究U50,488H(选择性κ阿片受体激动剂)是否通过抑制钙通道减少外钙内流参与了κ阿片受体的抗缺血性心律失常作用。方法将30只SD大鼠完全随机设计分为5组(每组6只):对照组(Sham)、缺血组(Isc)、缺血+U50,488H组(Isc+U50)、缺血+U50,488H+钙离子通道激动剂Bay k8644组(Isc+U50+Bay)、缺血+Bay k8644组(Isc+Bay)。建立大鼠急性心肌缺血模型,施行30 min心肌缺血前应用U50,488H(1.5 mg.kg-1)及Bay k8644(66.7μg.kg-1)进行干预,观察各组心律失常发生情况及连接蛋白43(Cx43)在蛋白和基因水平表达的变化。结果①在体动物模型中,Bay k8644可以翻转U50,488H激活κ阿片受体后产生的抗心律失常作用(P<0.05)。②在蛋白表达水平,Bay k8644可以阻断U50,488H对缺血心肌Cx43的保护性上调作用(P<0.01)。③在mRNA表达水平,Bay k8644亦可翻转U50,488H激活κ阿片受体后对缺血心肌Cx43mRNA的调控作用(P<0.01)。结论 U50,488H可通过抑制钙通道减少外钙内流,参与κ阿片受体对缺血心肌Cx43的稳定性调控及抗缺血性心律失常作用。     

蛋白磷酸酶1与Ca~(2+)/钙调素依赖性蛋白激酶Ⅱ在心肌病中研究进展

蛋白质的磷酸化与去磷酸化是细胞信号转导过程中最重要的调控方式,其循环过程就像调控分子的开关一样,参与众多生理活动。负责这一修饰调节的是蛋白激酶与蛋白磷酸酶。报道显示人类染色体编码多达500个蛋白激酶,这些蛋白激酶满足人类高度多样性与差异性调控蛋白磷酸化作用,而有趣的是人类编码的蛋白磷酸酶却仅仅约为150个,其中约有40个是丝氨酸/苏氨酸蛋白磷酸酶。越来越多的证据表明蛋白磷酸酶/蛋白激酶调控异常在心肌病中起关键作用。蛋白磷酸酶1(protein phosphatase 1,PP1)是一多功能的丝氨酸/苏氨酸蛋白磷酸酶,研究显示PP1在心肌肥厚和心衰的发生发展过程中起重要作用。而Ca2+/钙调素依赖性蛋白激酶Ⅱ(Ca2+/calmodulin-dependent protein kinaseⅡ,CaMKⅡ)是一种多功能的丝氨酸/苏氨酸蛋白激酶,它作为Ca2+信号转导的关键因子,调节细胞的多种生物学功能,其功能异常可引起肥厚心肌胞内钙稳态失衡进而引起心律失常等心肌病。该文就PP1与CaMKⅡ的功能和心肌病的关系作一综述。     

离子通道磷酸化,心律失常和新药的靶点

心律失常是心脏猝死的主要因素,心肌离子通道病变是导致心律失常发生的主要机制。对Na 、K 、Ca2 通道,肌浆网钙调控系统,钠钙交换体过磷酸化等心肌离子通道病的主要分子生物学基础进行阐述,为寻找新型抗心律失常药物提供新的靶点。     

内皮素受体拮抗剂CPU0213对异丙肾上腺素心肌病SERCA2a表达的改善作用

目的：研究异丙肾上腺素心肌病模型心肌细胞肌浆网钙ATP酶（sarco-endoplasmic reticulum ATPase 2a,SERCA2a）表达的改变,以及新型内皮素受体拮抗剂CPU0213的治疗作用。方法：雄性SD大鼠皮下给予异丙肾上腺素（2mg·kg^-1·d^-1）10d,治疗组动物在第6到第10天皮下给予CPU0213（30mg·kg^-1·d^-1）。各组动物颈动脉插管记录心功能指标：左心室收缩压（LVSP）,左心室舒张末期压（LVEDP）,和左心室压力变化最大速率（±dp/dtmax）。左心室心肌组织SERCA2a的mRNA及蛋白表达分别用逆转录聚合酶链反应（RT-PCR）和蛋白免疫印迹法（Western blotting）测定。结果：异丙肾上腺素引起左心室收缩和舒张功能明显下降,同时SERCA2a的mRNA及蛋白表达均显著下调（P〈0.05）。CPU0213显著提高SERCA2a表达（P〈0.05）,明显改善心功能（P〈0.05）。结论：CPU0213可通过逆转肌浆网钙调控蛋白SERCA2a的表达下调,使异丙肾上腺素引起的心功能下降得以恢复。本实验证明SERCA2a是β受体过度激活引发心衰过程中的重要靶点。内皮素受体介导了β受体过度激活状态下SER-CA2a的表达下调,是内皮素受体拮抗剂治疗心衰的重要依据之一。     

新型抗心衰药物--钙增敏剂作用机制的研究进展

钙增敏剂是新一类治疗充血性心衰的静脉注射剂,它通过心肌兴奋-收缩偶联过程提高心肌收缩力而不增加细胞内Ca2 的释放.由于钙增敏剂可降低心肌耗氧量,故有希望避免传统强心药的严重不良反应--心律失常的发生.多数钙增敏剂具有不同程度的磷酸二酯酶Ⅲ(PDE-Ⅲ)抑制活性.     

左西孟旦治疗急性心衰的发展前景

急性心衰是与血流动力学改变有关的疾病 ,治疗需从血流动力学角度入手。慢性心衰则与神经激素有关 ,治疗时需调节神经激素。现行急性心衰治疗手段主要有静注利尿剂 ,血管扩张剂和心肌收缩力增强剂。Ｐａｃｋｅｒ博士认为 ,急性心衰的治疗应与慢性心衰相同 ,即改善症状 ,降低死亡或严重心衰的危险。心肌收缩力增强剂长期应用有害 ,但短期应用有益。新的心肌收缩力增强剂主要有 :磷酸二酯酶抑制剂 ,α受体阻滞剂和钙敏剂。钙敏剂不会增加钙循环的能量需求 ,可单独通过ｃＡＭＰ途径增加心肌收缩力。其对正常的和衰竭的心脏具有同等的效果。左西…     

钙增敏剂左西孟旦降低心衰死亡率

新的研究发现一种新的钙增敏剂左西孟旦(levosimendan,Simdax)可降低患有低心输出量心衰的病人的死亡率，改善其心脏功能。左西孟旦由Orion制药公司开发用于治疗急性失代偿性心衰，具有双重作用机制。它可与一种影响心肌收缩的蛋白——肌钙蛋白C结合，使其对钙离子的敏感性增强，增加心脏收缩力，避免因钙过度蓄积而引起的心律失常；还可通过开放血管平滑肌上的ATP敏感型钾通道引起血管扩张。研究者认为左西孟旦影响心肌收缩和血管舒张作用进而增加心输出量的同时并不增加心肌的耗氧量。研究者就203例患有严重低心输出量心衰的病人比较了…     

左西孟旦的作用机制及临床应用研究进展

左西孟旦由Orion制药公司开发用于治疗急性失代偿性心衰,具有双重作用机制.它可与一种影响心肌收缩的蛋白——肌钙蛋白C结合,使其对钙离子的敏感性增强,增加心脏收缩力,避免因钙过度蓄积而引起的心律失常;还可通过开放血管平滑肌上的ATP敏感型钾通道引起血管扩张.研究者认为左西需旦影响心肌收缩和血管舒张作用进而增加心输出量的同时并不增加心肌的耗氧量.     

婴幼儿肺炎心衰患儿血清钙和心肌肌钙I的变化

目的探讨婴幼儿肺炎心衰患儿血清钙和心肌肌钙蛋白I的变化及其对预后的影响。方法用多功能生化分析仪对60例婴幼儿肺炎心衰患儿急性期检测血清钙,心肌肌钙蛋白I。选择普通肺炎及同期正常体检的婴幼儿作为对照组。计算均数和标准差,统计学处理采用F检验、X2检验。结果心衰组血清钙水平显著低于普通组和对照组,肌钙蛋白I显著高于普通组和对照组;心衰组低钙患儿死亡率显著增高。结论婴幼儿肺炎心衰患儿存在血清钙异常和心肌损伤,在其预后的判断中有重要价值。     

Ryanodine receptors as pharmacological targets for heart disease

Calcium release from intracellular stores plays an important role in the regulation of muscle contraction and electrical signals that determine the heart rhythm. The ryanodine receptor （RyR） is the major calcium （Ca^2＋） release channel required for excitation-contraction coupling in the heart. Recent studies have demonstrated that RyR are macromolecular complexes comprising of 4 pore-forming channel subunits, each of which is associated with regulatory subunits. Clinical and experimental studies over the past 5 years have provided compelling evidence that intracellular Ca^2＋ release channels play a pivotal role in the development of cardiac arrhythmias and heart failure. Changes in the channel regulation and subunit composition are believed to cause diastolic calcium leakage from the sarcoplasmic reticulum, which could trigger arrhythmias and weaken cardiac contractility. Therefore, cardiac RyR have emerged as potential therapeutic targets for the treatment of heart disease. Consequently, there is a strong desire to identify and/or develop novel pharmacological agents that may target these Ca^2＋ signaling pathways. Pharmacological agents known to modulate RyR in the heart, and their potential application towards the treatment of heart disease are discussed in this review.     

Acute heart failure: inotropic agents and their clinical uses

Inotropic agents are indispensable for the improvement of cardiac contractile dysfunction in acute or decompensated heart failure. Clinically available agents, including sympathomimetic amines (dopamine, dobutamine, noradrenaline) and selective phosphodiesterase-3 inhibitors (amrinone, milrinone, olprinone and enoximone) act via cAMP/protein kinase A (PKA)-mediated facilitation of intracellular Ca2+ mobilisation. Phosphodiesterase-3 inhibitors also have a vasodilatory action, which plays a role in improving haemodynamic parameters in certain patients, and are termed inodilators. The available inotropic agents suffer from risks of Ca2+ overload leading to arrhythmias, myocardial cell injury and ultimately, cell death. In addition, they are energetically disadvantageous because of an increase in activation energy and cellular metabolism. Furthermore, they lose their effectiveness under pathophysiological conditions, such as acidosis, stunned myocardium and heart failure. Pimobendan and levosimendan (that act by a combination of an increase in Ca2+ sensitivity and phosphodiesterase-3 inhibition) appear to be more beneficial among existing agents. Novel Ca2+ sensitisers that are under basic research warrant clinical trials to replace available inotropic agents.     

Pharmacological mechanisms contributing to the clinical efficacy of levosimendan

Acute decompensation of chronic heart failure is a direct life-threatening situation with short-term mortality approaching 30%. A number of maladaptive changes are amplified within the cardiovascular system during the progression of chronic heart failure that makes the decompensation phase difficult to handle. Levosimendan is a new Ca2+-sensitizer for the treatment of acutely decompensated heart failure that has proved to be effective during the decompensation of chronic heart failure and acute myocardial infarction. Levosimendan differs from other cardiotonic agents that are used for acute heart failure in that it utilizes a unique dual mechanism of action: Ca2+-sensitization through binding to troponin C in the myocardium, and the opening of ATP-sensitive K+ channels in vascular smooth muscle. In general, these mechanisms evoke positive inotropy and vasodilation. Clinical studies suggested long-term benefits on mortality following short-term administration. It may, therefore, be inferred that levosimendan has additional effects on the cardiovascular system that are responsible for the prolongation of survival. Results of preclinical and clinical investigations suggest that the combination of levosimendan-induced cardiac and vascular changes has favorable effects on the coronary, pulmonary and peripheral circulations. Redistribution of the circulating blood offers an improved hemodynamic context for the development of a positive inotropic effect through Ca2+-sensitization of the contractile filaments, without a proportionate increase in myocardial oxygen consumption or the development of arrhythmias. Activation of ATP-sensitive K+ channels, both on sarcolemma and mitochondria, may protect against myocardial ischemia, and decreased levels of cytokines may prevent the development of further myocardial remodeling. Collectively, these effects of levosimendan shift the disturbed cardiovascular parameters towards normalization, thereby halting the perpetuation of the vicious cycle of heart failure progression. This may contribute to stabilization of the circulation and improved life expectancy of patients with chronic heart failure.     

槲皮素对异丙肾上腺素所致大鼠心肌肥厚的影响

目的　研究槲皮素（ Ｑｕｅ） 对异丙肾上腺素（ Ｉｓｏ） 所致大鼠心肌肥厚的抑制作用及作用机制。方法　 Ｉｓｏ ００２ ｍｇ·ｋｇ－ １ ,每日两次,连续ｓｃ ６ ｗｋ ,形成大鼠心肌肥厚模型,分别测定心脏各重量参数、心肌过氧化脂质（ Ｌ Ｐ Ｏ） 含量、超氧化物歧化酶（ Ｓ Ｏ Ｄ） 活性及心肌 Ｃａ２ ＋ 和主动脉 Ｃａ２ ＋ 含量,培养乳鼠心肌细胞,应用 Ｆｕｒａ ２／ Ａ Ｍ 钙荧光指示剂技术测定心肌细胞内游离钙浓度。结果　 Ｉｓｏ 连续ｓｃ ６ ｗｋ 后,心肌和左心室重量明显增加,心肌 Ｌ Ｐ Ｏ 含量显著增加, Ｓ Ｏ Ｄ 活性下降,心肌 Ｃａ２ ＋ 和主动脉 Ｃａ２ ＋ 含量明显增加,给 Ｑｕｅ ７５ ｍｇ·ｋｇ－ １ ,１５０ ｍｇ·ｋｇ － １ 和维拉帕米１０ ｍｇ·ｋｇ － １ 后均能明显减轻心肌肥厚,降低 Ｌ Ｐ Ｏ 含量,增加 Ｓ Ｏ Ｄ 活性,降低心肌 Ｃａ２ ＋和主动脉 Ｃａ２ ＋ 的含量,应用 Ｆｕｒａ ２／ Ａ Ｍ 钙荧光指示剂技术发现 Ｉｓｏ 和 Ｈ２ Ｏ２ 能引起培养乳鼠心肌细胞内游离钙浓度明显升高。槲皮素对心肌细胞静息钙无明显影响,能抑制 Ｉｓｏ和 Ｈ２ Ｏ２ 致培养乳鼠心肌细胞内游离钙浓度的升高。结论　 Ｑｕｅ 能抑制 Ｉｓｏ 所引起的心肌肥厚, 该作用与清     

Sodium calcium exchange as a target for antiarrhythmic therapy

In search of better antiarrhythmic therapy, targeting the Na/Ca exchanger is an option to be explored. The rationale is that increased activity of the Na/Ca exchanger has been implicated in arrhythmogenesis in a number of conditions. The evidence is strong for triggered arrhythmias related to Ca2+ overload, due to increased Na+ load or during adrenergic stimulation; the Na/Ca exchanger may be important in triggered arrhythmias in heart failure and in atrial fibrillation. There is also evidence for a less direct role of the Na/Ca exchanger in contributing to remodelling processes. In this chapter, we review this evidence and discuss the consequences of inhibition of Na/Ca exchange in the perspective of its physiological role in Ca2+ homeostasis. We summarize the current data on the use of available blockers of Na/Ca exchange and propose a framework for further study and development of such drugs. Very selective agents have great potential as tools for further study of the role the Na/Ca exchanger plays in arrhythmogenesis. For therapy, they may have their specific indications, but they carry the risk of increasing Ca2+ load of the cell. Agents with a broader action that includes Ca2+ channel block may have advantages in other conditions, e.g. with Ca2+ overload. Additional actions such as block of K+ channels, which may be unwanted in e.g. heart failure, may be used to advantage as well.     

Long term regulation of cardiac L-type calcium channel by small G proteins

Calcium ions are crucial elements of excitation-contraction coupling in cardiac myocytes. The intracellular Ca(2+ ) concentration changes continously during the cardiac cycle, but the Ca(2+ ) entering to the cell serves as an intracellular second messenger, as well. The Ca(2+ ) as a second messenger influences the activity of many intracellular signalling pathways and regulates gene expression. In cardiac myocytes the major pathway for Ca(2+ ) entry into cells is L-type calcium channel (LTCC). The precise control of LTCC function is essential for maintaining the calcium homeostasis of cardiac myocytes. Dysregulation of LTCC may result in different diseases like cardiac hypertrophy, arrhytmias, heart failure. The physiological and pathological structural changes in the heart are induced in part by small G proteins. These proteins are involved in wide spectrum of cell biological functions including protein transport, regulation of cell proliferation, migration, apoptosis, and cytoskeletal rearrangement. Understanding the crosstalk between small G proteins and LTCC may help to understand the pathomechanism of different cardiac diseases and to develop a new generation of genetically-encoded Ca(2+ ) channel inhibitors.     

Clinical potential of sodium-calcium exchanger inhibitors as antiarrhythmic agents

The Na(+)/Ca(2+) exchanger (NaCaX) plays an important role in calcium handling in myocytes, but in the setting of calcium overload NaCaX can also contribute to the activation of an arrhythmogenic transient inward current (I(ti)). Therefore, approaches to inhibit NaCaX could have potential antiarrhythmic effects in pathophysiological states such as heart failure (HF) or myocardial ischaemia and reperfusion. NaCaX typically functions in a forward (Ca(2+) extrusion) mode but can also function in a reverse (Ca(2+) influx) mode. The determining factors for the directionality of NaCaX ion movement are the electrochemical gradients of calcium and sodium, and membrane potential (E(m)). In HF, upregulated NaCaX plays a dual role: it decreases sarcoplasmic reticulum (SR) calcium load, which leads to contractile dysfunction, and it underlies the I(ti) responsible for delayed after-depolarisations (DADs) and ventricular arrhythmias. In myocardial ischaemia and reperfusion, increases in [Na(+)](i) (as a result of acidosis and activation of the Na(+)/H(+) exchanger [NHE]) lead to calcium overload via the NaCaX and arrhythmogenesis is probably mediated by I(ti) activation due to NaCaX. As such, inhibition of NaCaX could provide a novel therapeutic approach to the prevention and treatment of arrhythmias. Unfortunately, it is difficult to assess the efficacy of such an approach since there are no specific NaCaX inhibitors. Currently available agents are hampered by their nonspecific effects on other ion channels and carriers. The potential utility of specific inhibition of forward or reverse mode NaCaX as an antiarrhythmic approach in the settings of HF and ischaemia/ reperfusion is discussed within the context of current knowledge of myocyte calcium and sodium handling. NaCaX is a challenging and complex therapeutic target because of the delicate balance of SR calcium load (too little contributes to contractile dysfunction and too much leads to calcium overload and arrhythmogenesis). Further understanding of NaCaX function, [Na(+)](i) and [Ca(2+)](i) in HF and ischaemia/reperfusion, combined with the development and assessment of specific NaCaX inhibitors, will ultimately define the potential role of NaCaX inhibition in the prevention and treatment of ventricular arrhythmias.     

AQP4 knockout mice manifest abnormal expressions of calcium handling proteins possibly due to exacerbating pro-inflammatory factors in the heart

We tested the hypothesis that aquaporin-4 (AQP4) knockout (KO) mice might exhibit abnormal Ca²⁺ modulating proteins resulting from the exacerbation of pro-inflammatory factors in the heart. Downregulation of FKBP12.6, SERCA2a, and CASQ2 and calcium leak in diastole have been recognized as endpoints for assessing cardiac failure and arrhythmias. The AQP4 KO mice and wild-type (WT) mice were randomly divided into 3 groups, such as control, isoproterenol (ISO, β-receptor agonist) injected (1 mg/kg, sc, 5 d), and treated with aminoguanidine (AMG, 100 mg/kg, po, a selective inhibitor of the iNOS) during the last 3 d. RT-PCR, western blot and calcium transient measurements were conducted. The results demonstrated that the cardiac weight index was increased in AQP4 KO mice and further increased following treatment with ISO. The expression levels of FKBP12.6, SERCA2a, and CASQ2 were downregulated and diastolic calcium concentrations were elevated in the AQP4 KO mice, indicative of a calcium leak. In the myocardium, expressions of pro-inflammatory biomarkers, including ET_A, pPKC?, NADPH oxidase p67^phox were upregulated and associated with downregulation of Cx43. The aforementioned changes were exacerbated in response to ISO medication and were attenuated by AMG; however, its treatment effectiveness was less in the AQP4 KO mice. We concluded AQP4 KO caused abnormalities of calcium modulating proteins leading to an exacerbation of risk for cardiac arrhythmias and failure. These changes are likely due to an increase in pro-inflammatory factors which are exacerbated by stress. Therefore, AQP4 KO mice are prone to cardiac failure and arrhythmias through exacerbating pro-inflammatory factors in the myocardium.     

前列腺素E_1、川芎嗪合用对大鼠心肌缺血再灌注损伤的保护作用

目的观察前列腺素Ｅ１（３１２５μｇ·ｋｇ－１）与川芎嗪（２５ｍｇ·ｋｇ－１）合用对大鼠心肌缺血再灌注损伤的影响。方法麻醉大鼠冠脉结扎３０ｍｉｎ后，再灌６０ｍｉｎ诱发心律失常，硫代巴比妥酸法和分光光度法分别测定ＭＤＡ、ＳＯＤ及ＧＳＨ Ｐｘ，原子吸收光度法测定心肌细胞内Ｃａ２＋含量。结果两药小剂量合用的效果优于各药较大剂量单用。联合用药不仅更显著提高缺血再灌心肌ＳＯＤ、ＧＳＨ Ｐｘ活力（Ｐ＜００１），尚可显著降低ＭＤＡ、Ｃａ２＋及血清ＣＫ ＭＢ含量（Ｐ＜００１），防止缺血再灌室性心律失常的发生（Ｐ＜００１）。结论前列腺素Ｅ１与川芎嗪合用对心肌缺血再灌注损伤的保护作用有显著的协同作用。其作用与提高自由基清除酶活性、抑制脂质过氧化反应和防止心肌细胞内“钙超负荷”有关     

Sarcoplasmic reticulum and cardiac oxidative stress: an emerging target for heart disease

The sarcoplasmic reticulum (SR) is a major player in maintaining cardiac function, as it is intimately involved in the regulation of Ca2+-movements on a beat-to-beat basis. SR dysfunction due to abnormalities in SR protein content has been reported in different cardiac diseases such as ischaemic heart disease, myocardial infarction, congestive heart failure and various cardiomyopathies; thus the genes expressing the SR Ca2+-pump, Ca2+-channels, calsequestrin, phospholamban and other regulatory proteins are considered important targets for drug development. In our experience, ischaemic preconditioning (IP) and pharmacological therapies, such as anti-oxidants, beta-adrenergic receptor blockers, angiotensin receptor (AT-1) blockers, angiotensin converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers are effective therapies that improve cardiac performance in the failing heart by improving SR function. Accordingly, this paper is intended to shed light on the knowledge in the field of cardiac therapy targeted to improve and protect SR function.