Regulation and Function of Phosphodiesterase in the Heart

 描述(申请人提供)：心力衰竭是一种多因素疾病，特征是心室肥大、扩张、心肌细胞死亡、纤维化和收缩功能障碍。CAMP和cGMP参与正常的生理适应和病理重塑，受多个空间离散和功能不同的环核苷酸信号控制。催化降解反应的环核苷酸磷酸二酯酶(PDE)对于维持环核苷酸的动态平衡、区隔化和特异性是必不可少的。越来越多的证据表明，不同PDE表达/激活的变化代表了许多疾病的致病机制，其中许多疾病已被发现通过药物靶向这些PDE而得到改善。因此，明确导致病理性心脏重构和功能障碍的特定PDE亚型对于开发新的治疗策略可能是至关重要的。通过对疾病心脏中改变的PDE的系统筛选，我们发现在衰竭心脏中，钙/钙调蛋白刺激的PDE1家族成员(包括PDE1A和1C)显著上调。然而，PDE1家族成员在心脏病进展中的作用和潜在机制仍不清楚。我们的体外研究表明，PDE1A在心肌细胞肥大和成纤维细胞激活中起重要作用，这可能是通过依赖cGMP/PKG抑制肌钙蛋白相关转录因子(MRTF)而实现的，而MRTF是心肌细胞肥大和成纤维细胞激活的关键。为了探索PDE1A在活体动物疾病模型中的作用，我们最近开发了一种PDE1A小鼠品系，允许在体内整体或以细胞类型特异性的方式耗尽PDE1A。相反，PDE1C在促进心肌细胞死亡方面发挥关键作用，可能是通过拮抗保护性的腺苷/cAMP信号。PDE1C也促进心肌细胞肥大，但通过不同的分子机制，包括cAMP/PKA依赖的组蛋白脱乙酰酶HDAC5的磷酸化和核质穿梭。PDE1C似乎与TRPC1/3(瞬时受体电位通道)相互作用，TRPC1/3可能是刺激PDE1C激活的钙来源。在我们的初步体内研究中，全球PDE1C基因敲除小鼠显示出一种趋势，即对压力超负荷诱导的心脏重构和功能障碍具有保护作用。基于这些令人兴奋的初步发现，我们假设PDE1A和PDE1C通过调节心肌细胞和/或成纤维细胞中不同的环核苷酸信号通路，在病理性心脏重塑和衰竭中发挥重要而不同的作用。这项建议的总体目标是通过建立成熟的体外和体内模型，研究不同的PDE1A和PDE1C调节的环核苷酸信号在心脏重塑和心力衰竭的关键发病过程中的功能作用和潜在机制。这些研究的结果可能有助于开发新的治疗策略，并有助于预测在使用PDE1抑制剂治疗其他疾病时的心脏副作用。

 DESCRIPTION (provided by applicant): Heart failure is a multifactorial disease, characterized by ventricular hypertrophy, dilation, myocyte death, fibrosis, and contractile dysfunction. cAMP and cGMP contribute to both normal physiological adaptation and pathological remodeling, which is controlled by multiple spatially discrete and functionally distinct cyclic nucleotide signaling. Cyclic nucleotide phosphodiesterases (PDEs) that catalyze the degradation reaction are essential for maintaining homeostasis, compartmentalization and specificity of cyclic nucleotides. Increasing evidence has indicated that alterations in the expression/activation of different PDEs represent causative mechanisms for a number of diseases, many of which have been found to be improved by pharmacologically targeting these PDEs. Thus, defining the specific PDE isoforms responsible for the pathological cardiac remodeling and dysfunction could be essential for developing new therapeutic strategies. Through systematic screening for PDEs that are altered in diseased hearts, we found that Ca2+/calmodulin-stimulated PDE1 family members (including PDE1A and 1C) are significantly up-regulated in failing hearts. However, the roles and underlying mechanisms of PDE1 family members in cardiac disease progression are still not well understood. Our in vitro studies showed that PDE1A plays important roles in cardiac myocyte hypertrophy and fibroblast activation, which is likely mediated by cGMP/PKG-dependent inhibition of myocardin-related transcription factor (MRTF) known to be critical for cardiac myocyte hypertrophy and fibroblast activation. To explore the role of PDE1A in animal disease models in vivo, we have recently developed a floxed PDE1A mouse strain, allowing in vivo depletion of PDE1A either globally or in a cell-type specific manner. In contrast, PDE1C plays a critical role in promoting myocyte death, likely by antagonizing the protective adenosine/cAMP signaling. PDE1C also promotes myocyte hypertrophy, but via a different molecular mechanism that involves cAMP/PKA- dependent phosphorylation of histone deacetylase HDAC5 and nucleocytoplasmic shuttling. PDE1C appears to interact with TRPC1/3 (transient receptor potential channels) that may functions as a source of Ca2+ for stimulating PDE1C activation. In our preliminary in vivo study, global PDE1C knockout mice showed a tendency towards protection from pressure overload-induced cardiac remodeling and dysfunction. Based on these exciting preliminary findings, we hypothesize that both PDE1A and PDE1C play essential but distinct roles in pathological cardiac remodeling and failure through modulating different cyclic nucleotide signaling pathways in cardiac myocytes and/or fibroblasts. The overall objective of this proposal is to investigate the functional roles and underlying mechanisms of distinct PDE1A- and PDE1C-regulated cyclic nucleotide signaling in the key pathogenic processes of cardiac remodeling and heart failure, by using well-established in vitro and in vivo models. Findings from these studies may facilitate the development of novel therapeutic strategies and help predict the cardiac side effects when using PDE1 inhibitors in treating other diseases.