High cGMP Alters Signal Transduction in Cardiac Failure

描述（由申请人提供）：一氧化氮-cGMP信号转导系统对心脏功能和代谢起“制动”作用，可能对肥大中过度的交感神经紧张具有保护作用。在衰竭中，心肌cGMP水平长期升高，但由于其信号传导途径的缺陷，其负面的功能和代谢作用降低。本研究的目的是确定心力衰竭时一氧化氮-cGMP系统适应不良的机制并加以纠正，假设心力衰竭时cGMP水平升高导致cGMP依赖性蛋白激酶下调，肌浆网钙ATP酶和释放通道磷酸化水平降低。其具体目的是通过长期降低失败的cGMP和提高控制来确定和纠正该信号系统的缺陷。从正常、肥大（主动脉瓣狭窄）和衰竭（快速起搏）心脏的成年犬中分离的心肌细胞，以及从有和无主动脉缩窄的转基因小鼠（高/低基础cGMP）中分离的心肌细胞，将用于确定cGMP信号传导缺陷及其对功能（视频边缘检测）、钙瞬变和O2消耗的影响。为了评估这些改变的信号传导过程的相对重要性，我们将研究它们对完整心脏的局部工作和O2消耗的影响。将在诱导肥大（有或无失败）后6个月在麻醉开胸犬中进行体内研究，并与对照组进行比较。将从节段长度（超声尺寸晶体）和收缩力（微型测力计）评估局部心肌功。将根据局部血流量和血红蛋白的局部氧饱和度（显微分光光度法）确定相同区域的氧消耗量。这些生理测量将与cAMP和cGMP及其信号传导途径的相应组分的生化测定相结合。最终目标是确定在失败中观察到的cGMP信号缺陷是否是引起失代偿的原因。提案的影响：对一氧化氮-cGMP信号转导系统缺陷的理解将允许开发用于人类充血性心力衰竭二级预防的新治疗策略。

DESCRIPTION (provided by applicant): The nitric oxide-cGMP signal transduction system acts as a "brake" on cardiac function and metabolism and may be protective against excessive sympathetic tone in hypertrophy. In failure, the myocardial cGMP level is chronically elevated but its negative functional and metabolic effects are reduced due to a defect in its signaling pathway. The objective of this proposal is to determine the mechanism responsible for the maladaptation of the nitric oxide-cGMP system in heart failure and correct it. The hypothesis to be tested is that high cGMP levels in failure result in down-regulation of the cGMP dependent protein kinase and decreased phosphorylation of sarcoplasmic reticulum calcium ATPase and release channel. The specific aim is to determine and correct the defect of this signaling system by chronically lowering cGMP in failure and raising it in controls. Cardiac myocytes isolated from adult dogs with normal, hypertrophied (aortic stenosis) and failing (rapid pacing) hearts, as well as from transgenic mice (high/low basal cGMP) with and without aortic banding will be used to determine the defect in cGMP signaling and its effect on function (video-edge detection), calcium transients and O2 consumption. To assess the relative importance of these altered signaling processes, we will examine their effects on local work and O2 consumption in the intact heart. The in vivo studies will be conducted in anesthetized, open-chest dogs 6 months after induction of hypertrophy with or without failure and compared to controls. Regional myocardial work will be assessed from segment length (ultrasonic dimension crystals) and contractile force (miniature force gauges). O2 consumption of the same area will be determined from regional blood flow and regional O2 saturation of hemoglobin (microspectrophotometry). These physiological measurements will be combined with biochemical assays for cAMP and cGMP and the respective components of their signaling pathway. The ultimate goal is to determine if the cGMP signaling defect observed in failure is what initiates decompensation. Impact of the proposal: the understanding of the defect in the nitric oxide-cGMP signal transduction system will permit the development of novel treatment strategies for the secondary prevention of congestive heart failure in man.