Molecular basis for activation of cardiovascular sensory afferents

心血管感觉传入激活的分子基础

• 批准号: 6704847
• 负责人: FRANCOIS M ABBOUD
• 金额: $ 28.24万
• 依托单位: UNIVERSITY OF IOWA
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-21 至 2007-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6704847
• 关键词: acidity /alkalinity; afferent nerve; aorta; baroreceptors; baroreflex; biological signal transduction; dystrophin; gene targeting; genetically modified animals; heart failure; heart innervation; intracardiac volume; laboratory mouse; mechanical pressure; mechanoreceptors; myocardial ischemia /hypoxia; neuroregulation; protein localization; protein structure function; sensory mechanism; sensory signal detection; sodium channel; spinal ganglion

For decades, studies ofbaroreceptor activity have depended on measurements of action potentials in single fibers or whole nerve. We had no insight into the molecular components of the mechanoelectrical transducers that initiate depolarization and trigger action potentials. In fact, transduction of mechanical stimuli is one of the least understood of the vertebrate senses. Our goal has been to define the molecular basis for mechanical activation of arterial and cardiac sensory afferents. In earlier studies we defined the characteristics of aortic baroreceptor neurons (BRNs) in culture. These channels are cation-selective, non voltage-gated, and blocked by amiloride or gadolinium. However, their molecular identity remains unknown. A candidate family of evolutionary-conserved ion channels, the degenerin/epithelial Na+-channels (DEG/ENaC), was discovered in a genetic screen for mechanosensitive genes in C. elegans. During the past 4 years we made important discoveries to advance our hypothesis that DEG/ENaC channels function as the mechanoelectrical transducer in mammalian meehanoreceptors: 1) DEG/ENaC subunits are expressed in mechanoreceptive neurons and in their sensory terminals. 2) The functions of BRNs, both in vivo and in vitro are reduced by inhibitors of DEG/ENaC channels. 3) Most important, targeted disruption of a DEG/ENaC subunit in mice reduced mechanosensation in aortic BRNs and in cutaneous mechanoreceptors but did not abolish it. We believe the mammalian mechanosensitive channels may be a heteromultimeric complex of multiple DEG/ENaC proteins, along with associated intra and extracellular "tethering" proteins. Thus, our first hypothesis is aimed at defining the subunits of the DEG/ENaC family and associated proteins that form the mechanosensitive complex in BRNs. Additionally, we have evidence that DEG/ENaC channels also play an important role in cardiac sensory neurons, not only as mechanosensors, but also as H+-sensors in the setting of myocardial ischemia. Thus, these channels could be the mediators of activation of cardiac sympathetic afferents, causing the pronounced reflex increase in sympathetic outflow in heart failure states. Therefore, our second hypothesis is aimed at defining the proton- and mechano-sensitive DEG/ENaC channels of cardiac sensory afferents in dorsal root ganglia (sympathetic afferents) and nodose ganglia (vagal afferents) and determining their function under normal physiological and in myocardial ischemia and heart failure.

几十年来，压力感受器活性的研究一直依赖于单纤维或整个神经动作电位的测量。 我们对启动去极化和触发动作电位的机电传感器的分子成分一无所知。 事实上，机械刺激的转导是脊椎动物感官中最不为人所知的感觉之一。我们的目标是确定动脉和心脏机械激活的分子基础 感觉传入。 在早期的研究中，我们定义了培养物中主动脉压力感受器神经元（BRN）的特征。 这些通道是阳离子选择性的、非电压门控的，并被阿米洛利或钆阻断。然而，它们的分子身份仍然未知。 进化保守离子通道的候选家族，即退化蛋白/上皮Na+通道（DEG/ENaC），是在秀丽隐杆线虫机械敏感基因的遗传筛选中发现的。在过去的 4 年中，我们取得了重要发现，以推进我们的假设，即 DEG/ENaC 通道在哺乳动物机械感受器中充当机械电传感器：1）DEG/ENaC 亚基在机械感受神经元及其感觉末梢中表达。 2) DEG/ENaC 通道抑制剂会降低 BRN 的体内和体外功能。 3) 最重要的是，DEG/ENaC 亚基的定向破坏 在小鼠中，减少了主动脉 BRN 和皮肤机械感受器的机械感觉，但并未消除它。 我们相信哺乳动物的机械敏感通道可能是多种 DEG/ENaC 蛋白以及相关的细胞内和细胞外“束缚”蛋白的异多聚体复合物。 因此，我们的第一个假设旨在定义 DEG/ENaC 家族的亚基以及在 BRN 中形成机械敏感复合物的相关蛋白。 此外，我们有证据表明 DEG/ENaC 通道在心脏感觉神经元中也发挥着重要作用，不仅作为机械传感器，而且在心肌缺血的情况下作为 H+ 传感器。因此，这些通道可能是心脏交感神经传入激活的介体，导致心力衰竭状态下交感神经流出的反射性显着增加。 因此，我们的第二个假设旨在定义背根神经节（交感传入神经）和结状神经节（迷走神经传入神经）中心脏感觉传入的质子和机械敏感DEG/ENaC通道，并确定它们在正常生理和心肌缺血下的功能和心力衰竭。