Myocardial Effects of PDE5 Inhibition in Single Ventricle Heart Disease

 描述(申请人提供)：单心室先天性心脏病(SV)是婴儿期心血管死亡的主要原因和心脏移植的适应症。室性心动过速包括一系列青紫型先天性心脏畸形，其特征是缺氧和单室循环。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步，但在当前时代，SV的一年存活率仅为68.7%。虽然单心室可以是形态上的右心室(RV)、左心室 对于LV或混合形态的RV，其结果最差，这可能是由于RV对增加的后负荷的耐受能力的内在限制。当单个RV同时作为体循环和肺循环的唯一泵时，毫不奇怪，RV故障既是这些患者死亡的常见原因，也是心脏移植的适应症。目前尚无针对心力衰竭的有效治疗方法，需要针对心力衰竭患者进行针对性的靶向治疗，以改善预后。磷酸二酯酶-5抑制剂(PDE5I)，如西地那非，被用于治疗儿童原发性肺动脉高压，因为它们被证明有血管扩张作用。在过去的几年里，PDE5i在室性心衰患者中的应用显著增加，目的是降低肺血管阻力，增加肺静脉回流到心脏，从而改善心输出量。在小系列的SV患者中，西地那非通过ECHO与血流动力学、运动耐量和心肌功能的改善有关。虽然SV患者的治疗目标是肺血管床，但在成人和HF动物模型中，越来越多的证据表明PDE5i具有有益的心肌重塑和功能影响。目前尚不清楚PDE5i在室性心动过速患者中的有益作用是否与心力衰竭患者的后负荷减少、直接的心肌效应或两者的结合有关。这一假设的中心假设是PDE5i在SV中具有直接的心肌效应，导致心功能增强，影响cGMP调节的信号通路，并改变肌节蛋白的磷酸化。由于在体内对脆弱的儿科人群进行研究存在困难，目前的应用利用正在进行的移植的人类心脏组织库和细胞培养模型来解决特定目标，从而将对儿童的风险降至最低。我们将分析PDE5i对移植心脏小梁的肌原纤维力学和肌节磷酸化以及力产生的影响。目前的应用将是第一次确定PDE5i对移植的儿童SV心脏的心肌影响，并开始将分子研究结果与功能联系起来。最后，我们将使用药理学和遗传学方法来研究PDE5i对新生大鼠心室肌细胞(NRVMs)的细胞内作用。

 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).