Myocardial Effects of PDE5 Inhibition in Single Ventricle Heart Disease

 描述（由申请人提供）：单心室先天性心脏病（SV）是心血管死亡的主要原因，也是婴儿期心脏移植的指征。SV包括一系列由缺氧和单心室循环定义的紫绀型先天性心脏畸形。这些缺陷在没有干预的情况下普遍是致命的，尽管内科和外科治疗取得了进展，但目前SV的1年生存率仅为68.7%。虽然单心室可以是形态学上的右心室（RV）、左心室（RV）或左心室（RV）。 (LV)或混合形态，单RV病变的结局最差，可能是由于RV耐受增加后负荷的能力的固有限制。当单个RV充当体循环和肺循环的唯一泵时，毫不奇怪，RV衰竭既是这些患者死亡的常见原因，也是心脏移植的指征。目前尚无经证实的SV心力衰竭治疗方法，需要确定针对衰竭SV的靶向治疗以改善结局。磷酸二酯酶-5抑制剂（PDE 5i），如西地那非，由于其经证实的血管舒张作用，被用于治疗儿童原发性肺动脉高压。在过去的几年中，在SV HF患者中使用PDE 5i的数量急剧增加，目的是降低肺血管阻力，增加肺静脉回流到心脏，随后改善心输出量。在小系列SV患者中，通过超声心动图发现西地那非可改善血流动力学、运动耐量和心肌功能。虽然SV患者的既定治疗目标是肺血管床，但在成人和HF动物模型中有越来越多的证据表明PDE 5i具有有益的心肌重塑和功能作用。尚不清楚PDE 5i在SV人群中的有益作用是否与衰竭SV的后负荷减少、直接心肌效应或两者的组合有关。该提议的中心假设是PDE 5i在SV中具有直接的心肌效应，其导致增强的心脏功能、对cGMP调节的信号传导途径的效应和改变的肌节蛋白磷酸化。由于难以在脆弱的儿科人群中进行体内研究，本申请利用正在进行的人心脏组织库和细胞培养模型来解决特定目标，从而最大限度地降低对儿童的风险。我们将分析PDE 5i对来自收缩的SV心脏的肌原纤维力学和肌节磷酸化以及小梁中的力产生的影响。目前的应用将是第一个确定PDE 5 i在心脏移植的小儿SV心脏中的心肌效应，并开始将分子结果与功能相关联。最后，我们将使用药理学和遗传学方法研究PDE 5i在新生大鼠心室肌细胞（NRVM）中的细胞内效应。

 DESCRIPTION (provided by applicant): Single ventricle congenital heart disease (SV) is the leading cause of cardiovascular death and indication for heart transplantation in infancy. SV comprises a spectrum of cyanotic congenital cardiac malformations that are defined by hypoxia and a univentricular circulation. These defects are universally fatal without intervention and despite advances in medical and surgical therapies, the 1-year survival for SV in the current era is only 68.7%. While the single ventricle can be a morphologic right ventricle (RV), left ventricle (LV) or of mixed morphology, it is the single RV lesions that have the worst outcome, presumably due to inherent limitations in the RV's ability to tolerate increased afterload. When a single RV serves as the sole pump to both the systemic and pulmonary circulations, not surprisingly, failure of the RV is both a common cause of death and indication for heart transplant in these patients. There are currently no proven therapies for SV heart failure and identification of targeted therapies specific to the failing SV are needed in order to improve outcomes. Phosphodiesterase-5 inhibitors (PDE5i), such as sildenafil, are used for the treatment of primary pulmonary hypertension in children due to their proven vasodilatory effects. Over the past few years, use of PDE5i in those with SV HF has increased dramatically with the intention of lowering pulmonary vascular resistance, increasing pulmonary venous return to the heart and subsequently improving cardiac output. Sildenafil has been associated with improved hemodynamics, exercise tolerance and myocardial function by echo in small series of SV patients. While the stated target of therapy in SV patients is the pulmonary vascular bed, there is increasing evidence in adults and animal models of HF that PDE5i has beneficial myocardial remodeling and functional effects. Whether the beneficial effects of PDE5i in the SV population specifically are related to afterload reduction of the failing SV, direct myocardial effects or a combination of both is unknown. The central hypothesis of this proposal is that PDE5i has direct myocardial effects in SV that result in augmented cardiac function, effects on cGMP-regulated signaling pathways and altered sarcomeric protein phosphorylation. Due to difficulties performing research in the vulnerable pediatric population in vivo, the current application utilize an ongoing explanted human heart tissue bank and a cell culture model to address the specific aims, thereby minimizing risk to children. We will analyze the effect of PDE5i on myofibril mechanics and sarcomere phosphorylation as well as force generation in trabeculae from explanted SV hearts. The current application will be the first to determine myocardial effects of PDE5i in explanted pediatric SV hearts and begin to correlate molecular findings with function. Finally, we will use pharmacologic and genetic methods to investigate the intracellular effects of PDE5i in neonatal rat ventricular myocytes (NRVMs).