High cGMP Alters Signal Transduction in Cardiac Failure

描述(申请人提供)：一氧化氮-cGMP信号转导系统对心脏功能和新陈代谢起“刹车”作用，可能对肥厚时过度的交感紧张具有保护作用。在衰竭时，心肌cGMP水平会慢性升高，但由于其信号通路的缺陷，其负性功能和代谢效应会减少。这项建议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纠正它。需要检验的假设是，在失败时，高水平的cGMP会导致cGMP依赖的蛋白激酶下调，肌浆网钙ATPase和释放通道的磷酸化减少。其具体目的是通过在失败时慢性降低cGMP和在对照组中提高cGMP来确定和纠正该信号系统的缺陷。从正常、肥厚(主动脉狭窄)和衰竭(快速起搏)心脏的成年犬以及带和不带主动脉带的转基因小鼠(高/低基础cGMP)分离的心肌细胞将被用来确定cGMP信号的缺陷及其对功能(视频边缘检测)、钙瞬变和氧气消耗的影响。为了评估这些改变的信号过程的相对重要性，我们将检查它们对完整心脏的局部工作和氧气消耗的影响。体内研究将在麻醉开胸犬肥厚诱导6个月后进行，并与对照组进行比较。局部心肌作功将通过节段长度(超声尺寸晶体)和收缩力量(微型测力计)进行评估。同一区域的氧气消耗量将根据区域血流量和区域血红蛋白的氧气饱和度(显微分光光度法)来确定。这些生理测量将与cAMP和cGMP及其信号通路各自组成部分的生化分析相结合。最终目标是确定在故障中观察到的cGMP信号缺陷是否是启动失代偿的原因。建议的影响：对一氧化氮-cGMP信号转导系统缺陷的了解将有助于开发新的治疗策略，用于人类充血性心力衰竭的二级预防。

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.