Histamine Receptor/Norepinephrine in Cardiac Dysfunction

描述（由申请人提供）：在心肌缺血时，过度释放去甲肾上腺素（NE）引起的心律失常导致高发病率和死亡率。因此，减少心肌缺血时心脏交感神经末梢（SNE）的NE释放是一个关键目标。我们将研究内源性调节剂在正常和缺血情况下如何调节心脏交感神经传递。在Aim 1中，我们将研究组胺h3受体（H3R）分别减弱与短期和长期缺血/再灌注（I/R）相关的Ca2+依赖性NE胞分泌和载体介导的NE释放的转导机制。这将在转染H3R的细胞和来自表达天然H3R的豚鼠心脏的SNE中进行研究。对于NE胞分泌和短期I/R，我们将评估H3R激活如何限制Ca2+通过n型Ca2+通道进入，以及PKC和PLAa在实现这一过程中的作用。对于载体介导的NE释放和延长I/R，我们将研究H3R激活与Na+/H+交换器（NHE）抑制的耦合，并将评估H3R与血管紧张素ATI受体在SNE中NHE水平的相互作用。缺乏H3R的小鼠心脏将被研究。内源性组胺对H3R激活的心脏保护作用的贡献将在肥大细胞缺陷小鼠的缺血心脏中确定。在参与h3r介导的NHE活性降低和载体介导的NE释放的转导信号中，PKC和钙调蛋白将被研究。在目的2中，我们将确定组织纤溶酶原激活剂在正常和缺血心脏中促进NE释放的机制。将使用纤维蛋白溶解级联的各种成分基因缺失的小鼠。这些研究将阐明内源性控制NE释放的机制。由于NE释放的减少对心肌缺血具有保护作用，因此确定和表征控制NE释放的因素将有助于开发心血管疾病的新治疗策略。

DESCRIPTION (provided by applicant): In myocardial ischemia, arrhythmias due to excessive norepinephrine (NE) release cause high morbidity and mortality. Thus, reduction of NE release from cardiac sympathetic nerve endings (SNE) in myocardial ischemia is a critical goal. We will study how endogenous modulators regulate cardiac sympathetic neurotransmission in normal and ischemic conditions. In Aim 1, we will investigate the transductional mechanisms by which histamine H3-receptors (H3R) attenuate Ca2+- dependent NE exocytosis and carrier-mediated NE release, associated with short-term and protracted ischemia/reperfusion (I/R), respectively. This will be studied in H3R-transfected cells and in SNE from guinea-pig hearts expressing native H3R. For NE exocytosis and short-term I/R we will assess how H3R activation limits Ca2+ entry through N-type Ca2+-channels, and the roles of PKC and PLAa in implementing this. For carrier-mediated NE release and protracted I/R, we will investigate the coupling of H3R activation to Na+/H+ exchanger (NHE) inhibition, and will assess the interaction between H3R and angiotensin ATI receptors at the NHE level in SNE. Mouse hearts lacking H3R will be studied. The contribution of endogenous histamine to the cardioprotective effects of H3R activation will be determined in ischemic hearts from mast-cell-deficient mice. Among the transductional signals involved in the H3R-mediated reduction of NHE activity and carrier- mediated NE release, PKC and calmodulin will be investigated. In Aim 2, we will determine by which mechanisms tissue plasminogen activator promotes NE release in normal and ischemic hearts. Mice with genetic deletions of various components of the fibrinolytic cascade will be used. These studies will elucidate the mechanisms for endogenous control of NE release. Since reduction of NE release is protective in myocardial ischemia, identification and characterization of the factors controlling NE release will help in the development of novel therapeutic strategies in cardiovascular diseases.