ANP Modulates Cardiac Remodeling via Cardiac Fibroblasts

心钠素(ANP)是胎儿基因程序中的一个众所周知的成分，在 成人心脏在应激状态下。然而，心钠素在心钠素中的作用还没有引起足够的重视。 紧张/肥大的心脏。目前的应用将检验ANP具有直接抗生长作用的假设 以及与转化生长因子-β的促纤维化作用相反的抗纤维化作用 和血管紧张素II(AngII)，已知在压力条件下心脏过度表达，通过 中断它们的信号级联。我们已经证明，与非转基因(NTG)对照组相比，小鼠 ANP基因纯合子突变(NPPA-/-)在基线和 过度的心脏重塑/纤维化，以及早期向衰竭的过渡，对横断面的反应 主动脉缩窄(TAC)诱导的压力超负荷应激。初步研究显示，值得注意的是 心肌成纤维细胞转化和细胞外基质分子表达的增加 对NPPA-/-小鼠进行标记。我们还证明了TAC诱导的心脏重塑和 表达可诱导的转化生长因子-β受体显性负突变的小鼠的纤维化被消除 II型基因(DriTGFbRIl)，因此对转化生长因子-β信号没有反应。最近，我们已经做出了 ANP信号抑制转化生长因子-β诱导的大鼠心肌细胞核移位的初步观察 小鼠心脏成纤维细胞中的磷酸化Smads，首次定义了一个精确的分子 心钠素信号对心脏重构/纤维化和反应性衰竭的保护机制 对血流动力学的压力。这项建议的目的是：1)建立NPPA-/-的表型， DnTGFbRII和对照NTG小鼠心脏在静息状态和不同时期(急性应激， 早期代偿阶段的纤维化和重塑，以及晚期的失代偿/向衰竭的过渡阶段) 在压力过载过程中，应紧跟在标签后面。这一目标将提供第一个严格的体内角色测试 转化生长因子-β信号通路在介导压力超负荷所致左心室纤维化/重构及心钠素表达中的作用 调节这些过程。2)以分离的CFs为体外模型，确定细胞内信号转导。 促纤维化/生长因子刺激的CFs增殖/转化和细胞外基质的机制 表情。这一目标将对ANP信号具有负性的假设进行严格的测试，并且 转化生长因子-β(和/或血管紧张素Ⅱ)信号在这些过程中具有积极的刺激作用。ANP和/或 其信号通路的组件将用于定义ANP级联的特定位置(S 阻断促纤维化/生长因子信号，从而抑制CFs和ECM的表型转化 制作。这些机制研究将为临床治疗干预提供更合理的依据。 心功能不全/衰竭的患者，其中许多人的心钠素水平降低。

Atrial natriuretic peptide (ANP) is a well known component of the fetal gene program that is overexpressed in adult heart under stress conditions. Yet little attention has been devoted to the function of ANP in the stressed/hypertrophic heart. The current application will test the hypothesis that ANP has direct anti-growth and anti-fibrogenic effects that oppose the pro-fibrogenic actions of transforming growth factor (TGF)-beta and angiotensin II (ANGII), which are known to be overexpressed in heart under stress conditions, by interrupting their signaling cascades. We have shownthat, compared to nontransgenic (NTG) controls, mice with homozygousdisruption of the ANP gene (Nppa-/-) exhibit cardiac enlargement at baseline and exaggerated cardiac remodeling/fibrosis, as well as an early transition to failure, in response to transverse aortic constriction (TAC)-induced pressure overload stress. Preliminary studies revealed remarkable increases in myofibroblast transformation and expression of extracellular matrix (ECM) molecules in hearts of Nppa-/- mice subjected to TAG. We have also demonstrated that TAC-induced cardiac remodeling and fibrosis are abolished in mice that express an inducible dominant negative mutation of the TGF-beta receptor type II gene (DriTGFbRIl), andthus do not respond to TGF-beta signaling. Most recently, we have made the exciting preliminary observation that ANP signaling inhibits TGF-beta-induced nuclear translocation of phosphorylated-SmadS in mouse cardiac fibroblasts (CFs), defining for the first time a precise molecular mechanism by which ANP signaling may protect against cardiac remodeling/fibrosis and failure in response to hemodynamic stress. The Aims of this proposal are: 1)To establish the phenotypes of Nppa-/-, DnTGFbRII and control NTG mouse hearts under resting conditions and at various phases (acute stress, early compensatory stage of fibrosis and remodeling, and late decompensate/transition stage to failure) during pressure overload stress following TAG. This Aim will provide the first rigorous in vivo test of the role of TGF-beta signaling in mediating pressure overload-induced LV fibrosis/remodeling and of ANP in modulating these processes. 2) Using isolated CFs as an in vitro model, to define the intracellular signaling mechanisms leading to pro-fibrogenic/growth factor-stimulated CF proliferation/transformation andECM expression. This Aim will provide a rigorous test of the hypothesis that ANP signaling has negative, and TGF-beta (and/or ANGII) signaling has positive stimulatory effects on these processes. ANP and/or components of its signaling pathwaywill be used to define the specific site(s) at which the ANP cascade intercepts pro-fibrogenic/growth factor signaling, thus inhibiting phenotypic transformation of CFs andECM production. These mechanistic studies will provide a more rational basis for therapeutic intervention in patients with cardiac dysfunction/failure, many of whom have decreased levels of ANP.