Pannexin channels in cardiac arrhythmias

心律失常中的 Pannexin 通道

• 批准号: 9231086
• 负责人: Sabine Huke
• 金额: $ 36.75万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2019-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9231086
• 关键词: Accounting; Action Potentials; Adult; Antibodies; Arrhythmia; Blood Vessels; Brain; Calsequestrin; Cardiac Myocytes; Catecholaminergic Polymorphic Ventricular Tachycardia; Cell membrane; Cells; Cessation of life; Coronary; Coronary artery; Coupled; Data; Defect; Generations; Genetic; Health; Heart; Heart Diseases; Histology; Hour; Infarction; Inherited; Knock-out; Knockout Mice; Label; Lead; Ligation; Measurement; Mediating; Membrane; Membrane Potentials; Molecular; Mus; Muscle Cells; Myocardial Infarction; Paracrine Communication; Physiological; Play; Predisposition; Probenecid; Protein Isoforms; Purkinje Cells; Regulation; Research; Reverse Transcriptase Polymerase Chain Reaction; Risk; Role; Sarcoplasmic Reticulum; Staining method; Stains; Stretching; Telemetry; Testing; Tissues; United States; Ventricular; contactin; density; drinking water; extracellular; implantation; in vivo; inhibitor/antagonist; mouse model; novel; patch clamp; premature; prevent; receptor; research study; sudden cardiac death; synaptic function

 DESCRIPTION (provided by applicant): Pannexin (Px) channels, first been described in 2000, have been mostly studied in the brain where they reportedly play a role in synaptic function, propagation of Ca waves and regulation of vascular tone. Much less is known about their role in the heart. In general, three isoforms have been described (Px1, 2, 3). Px channels from large pores permeable to molecules up to 1 kDa and can open at physiological extracellular Ca. In ventricular cardiomyocytes Px channels are expressed in very low density, but single channel conductance is so large (>300 pS) that it can be resolved in whole cell patch clamp. The objective of the proposal is to test the novel hypothesis that Px channel activation during diastolic Ca release facilitates triggered heart beats. Diastolic Ca releases from the sarcoplasmic reticulum (SR) Ca store and triggered beats are hallmarks of inherited catecholaminergic polymorphic ventricular tachycardia (CPVT) and are also found as acquired defect after myocardial infarction (MI). Diastolic Ca releases cause a transient inward current (Iti) that depolarizes the cell membrane (termed delayed after depolarization's, DADs), which, when large enough to activate the Na channel, trigger an action potential (AP) and a propagated beat. It is generally accepted that Iti is foremost generated by the Na Ca exchanger (NCX) transporting Ca out of the cell. However, it remains unclear how NCX can generate enough current to trigger an AP in intact tissue, where ventricular myocytes are electrically coupled and effectively stabilized by a large current "sink". Our preliminary data indicate that Px channel opening during diastolic Ca release contributes to Iti in cardiomyocytes from a CPVT mouse model, the calsequestrin KO mice (Casq2-/-). Moreover, pharmacologic inhibition of Px channels or genetic KO of Px1 effectively reduced triggered arrhythmia in Casq2-/- mice. Thus, our central hypothesis is that Px channels importantly increase DADs caused by premature SR Ca release and elevate arrhythmia susceptibility. The proposed experiments will investigate Px channel activation and contribution to Iti in isolated cardiomyocytes (Aim 1) and test arrhythmia susceptibility in vivo using Casq2-/- mice (Aim 2) and mice with coronary artery ligation (Aim 3). Accomplishing these aims will provide new mechanistic information on Px channels in arrhythmia and may lead to a new paradigm for treating Ca triggered arrhythmia in common heart diseases such as MI.

 描述(申请人提供)：PAnnexin(Px)通道于2000年首次被描述，主要在大脑中进行研究，据报道它们在突触功能、钙波的传播和血管张力的调节中发挥作用。人们对它们在心脏中的作用知之甚少。一般来说，已经描述了三种亚型(PX1，2，3)。Px通道可从大孔道通透至1 kDa的分子，并可在生理细胞外钙处开放。在心室肌细胞中，Px通道的表达密度很低，但单通道电导很大(&gt；300ps)，可以在全细胞膜片钳中分辨。该提案的目的是验证这一新的假设，即舒张期钙释放过程中Px通道的激活促进了触发的心跳。肌浆网(SR)钙库的舒张期钙释放和触发搏动是遗传儿茶酚胺能多形性室性心动过速(CPVT)的特征，也被发现为心肌梗死(MI)后获得性缺陷。舒张期钙释放引起瞬时内向电流(Iti)，使细胞膜去极化(称为去极化后延迟，DADS)，当其大到足以激活Na通道时，触发动作电位(AP)和传播的搏动。通常认为，Iti首先是由钠钙交换器(NCX)将钙输送出细胞而产生的。然而，目前尚不清楚NCX如何在完整的组织中产生足够的电流来触发AP，在完整的组织中，心室肌细胞电耦合并有效地被大电流“槽”稳定。我们的初步数据表明，在CPVT小鼠模型Calequestrin KO小鼠(Casq2-/-)的心肌细胞中，舒张期钙释放过程中Px通道的开放有助于心肌细胞的Iti。此外，药物抑制PX通道或PX1的遗传KO可有效减少Casq2-/-小鼠触发的心律失常。因此，我们的中心假设是，Px通道显著增加了过早释放SR Ca引起的DAD，并增加了心律失常的易感性。拟议的实验将研究分离的心肌细胞中Px通道的激活和对Iti的贡献(Aim 1)，并使用Casq2-/-小鼠(Aim 2)和冠状动脉结扎小鼠(Aim 3)测试体内心律失常的易感性。这些目标的实现将为心律失常的Px通道提供新的机制信息，并可能为治疗心肌梗死等常见心脏疾病中的钙性心律失常提供新的范式。