ANP Modulates Cardiac Remodeling via Cardiac Fibroblasts

心房利钠肽（ANP）是一种众所周知的胎儿基因程序的组成部分，在胚胎发育中过度表达。 成年人的心脏处于应激状态。然而，很少有人注意到ANP在脑缺血中的作用。 应激/肥大心脏。目前的应用将测试ANP具有直接抗生长的假设 和对抗转化生长因子（TGF）-β的促纤维化作用的抗纤维化作用 和血管紧张素II（ANGII），已知其在应激条件下在心脏中过表达， 中断他们的信号级联我们已经表明，与非转基因（NTG）对照组相比， 具有ANP基因同源性破坏（Nppa-/-）的患者在基线时表现出心脏增大， 过度的心脏重塑/纤维化，以及对横向 主动脉缩窄（TAC）诱导的压力超负荷应激。初步研究显示， 心脏中肌成纤维细胞转化和细胞外基质（ECM）分子表达增加 的Nppa-/-小鼠。我们还证明了TAC诱导的心脏重塑和 在表达TGF-β受体的可诱导显性负突变的小鼠中， II型基因（DriTGF β RI 1），因此不响应TGF β信号。最近，我们 令人兴奋的初步观察，ANP信号抑制TGF-β诱导的核转位， 磷酸化SmadS在小鼠心脏成纤维细胞（CFs），首次定义了一个精确的分子， ANP信号传导可保护心脏重塑/纤维化和响应失败的机制 血流动力学压力。本发明的目的是：1）建立Nppa-/-的表型， DnTGFbRII和对照NTG小鼠心脏在静息条件下和在各个阶段（急性应激， 纤维化和重塑的早期代偿阶段，以及晚期失代偿/向衰竭的过渡阶段） 在TAG之后的压力过载应力期间。这一目标将提供第一个严格的体内测试的作用 TGF-β信号在介导压力超负荷诱导的左室纤维化/重塑中的作用和 调节这些过程。2)使用分离的CFs作为体外模型，以确定细胞内信号传导 导致促纤维化/生长因子刺激的CF增殖/转化和ECM的机制 表情该目的将为ANP信号传导具有负性的假设提供严格的测试， TGF-β（和/或ANGII）信号传导对这些过程具有积极的刺激作用。ANP和/或 其信号通路的组成部分将用于定义ANP级联的特定位点 阻断促纤维化/生长因子信号传导，从而抑制CF和ECM的表型转化 生产这些机制研究将为治疗性干预提供更合理的依据。 心功能不全/心力衰竭患者，其中许多人的ANP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.