Ang II and Norepinephrine in Cardiac Sympathetic Nerves

描述（由申请人提供）：在心肌缺血时，交感神经病理释放去甲肾上腺素（NE）导致心律失常和死亡。造成这种情况的机制仍然不清楚。该资助的总体目标是解决重要的生物学问题，即局部肾素-血管紧张素系统（RAS）是否在心肌缺血中加剧NE释放中起重要作用。我们的初步结果表明，心脏肥大细胞是肾素的一种新来源，肾素是一种限速酶，负责启动ANG的形成。我们假设心肌肥大细胞的脱颗粒在缺血时发生，是激活邻近神经元ATi受体（ATiR）的局部RAS和ANG II形成的关键。在Specific Aim I中，我们将从c-Kit敲除（KO）小鼠的同源对照（CC）和培养的人肥大细胞（HMC-1）中表征肥大细胞肾素。我们还将在豚鼠、CC和KO小鼠的常氧和缺血心脏模型中研究，肥大细胞源性肾素局部合成的ANG n是否会激活神经元ATiR，从而引发NE释放和再灌注心律失常。我们已经在缺血交感神经的培养细胞模型中确定，外源性ANG n刺激神经元Na+/H^交换（NHE），导致过度的载体介导的NE释放。因此，在Specific Aim n中，我们将研究在转染了克隆大鼠ATjA受体（SH-SYSY-ATu）的人神经母细胞瘤细胞中，这种ANG h介导的NHE刺激的信号转导。SH-SYSY-ATiA细胞的实验表明，AT)R激活刺激NHE和载体介导的NE释放是通过Ca +依赖途径发生的。因此，我们的研究将集中在阐明PLC、Ca2+、PKC和钙调蛋白在Ca2+依赖通路中的作用。这些实验的总体前提是，如果我们了解了缺血心脏中ANG n形成的病理生理基础，以及ANG II如何加剧NE的释放，那么我们也将找到缓解缺血性心律失常和相关心功能障碍的潜在治疗靶点。

DESCRIPTION (provided by applicant): In myocardial ischemia, pathologic release of norepinephrine (NE) from sympathetic nerves leads to arrhythmias and death. The mechanisms responsible remain obscure. The overall objective of this grant is to address the important biological issue of whether a local renin-angiotensin system (RAS) plays a significant role in exacerbating NE release in myocardial ischemia. Our preliminary results demonstrate that cardiac mast cells are a novel source of renin, the rate-limiting enzyme responsible for initiating ANG n formation. We hypothesize that degranulation of cardiac mast cells, as occurs in ischemia, is pivotal for activation of local RAS and ANG II formation in the proximity of neuronal ATi receptors (ATiR). In Specific Aim I, we will characterize mast-cell renin from congenic controls (CC) of c-Kit knock out (KO) mice, and from cultured human mast cells (HMC-1). We will also investigate in normoxic and ischemic cardiac models from guinea-pigs, and CC and KO mice, whether locally synthesized ANG n from mast-cell-derived renin activates neuronal ATiR to elicit NE release and reperfusion arrhythmias. We have already ascertained in a cultured-cell model of ischemic sympathetic nerves, that exogenous ANG n stimulates neuronal Na+/H^ exchange (NHE) leading to excessive carrier-mediated NE release. Thus, in Specific Aim n we will study, in human neuroblastoma cells transfected with the cloned rat ATjA receptor (SH-SYSY-ATu), the signal transduction of this ANG H-mediated NHE stimulation. Experiments in SH-SYSY-ATiA cells demonstrate that stimulation of NHE and carrier-mediated NE release by AT)R activation occurs via a Ca +-dependent pathway. Accordingly, our investigation will focus on elucidating the role of PLC, Ca2+, PKC, and calmodulin in this Ca2+-dependent pathway. The overall premise of these experiments is that if we understand the patho-physiological basis for the formation of ANG n in the ischemic heart, and how ANG II exacerbates NE release, then we will also have identified potential therapeutic targets to alleviate ischemic arrhythmias and associated cardiac dysfunctions.