Role of RhoA in the Molecular Pathogenesis of Heart Disease.

7.项目摘要/摘要 心力衰竭是一种进行性疾病，其特征是心肌细胞(CM)丢失，间质纤维化，丢失 心脏顺应性和心腔重塑。CMS对病理刺激的反应变化， 改变它们的细胞形态，增加蛋白质合成，上调胎儿基因。虽然一开始 代偿性的，这些变化最终会变得不适应，导致纤维化和不良心脏 回应。心脏成纤维细胞(FBS)参与调节这一有害特征的某些方面，但是 调节它们功能的具体分子机制尚不清楚。然而，FBS是众所周知的 心功能的重要影响因素，其中它们是心脏功能的主要决定因素 应激和损伤后的重塑和纤维化。然而，在慢性疾病状态下，这种纤维化 反应导致室壁顺应性降低，扩散效率降低，并出现心律失常。因此， 限制慢性应激条件下的纤维化和肌成纤维细胞的活性 有益于预防心力衰竭。作为我们最初拨款的一部分，我们产生了患有CM的小鼠- 特异性缺失RAS相关的小G蛋白RhoA以确定其分子机制 特别是在心肌中的活动。为了应对慢性压力，我们发现这些小鼠的心脏 出现加速扩张，收缩功能明显丧失。然而，尽管 在心力衰竭病理中，他们也显著减少了心脏纤维化，具有明显的 参与纤维化反应的基因转录激活减少，包括血清 反应因子(SRF)和心肌钙蛋白相关转录因子(MRTF)。总而言之，我们的数据表明 RhoA在心脏损伤中是一种关键的节点酶，其功能是保存 收缩能力和介导促纤维化基因的激活。 在这里，在这个更新申请中，我们建议具体询问功能和机械 RhoA信号在纤维化中的作用(S)。我们假设RhoA直接调节FB的活性， 在激活的FB内，以及通过CM特定的旁分泌信号间接地调节 心肌成纤维细胞的激活和/或对心脏应激和损伤的反应。我们建议1)检查 CM特异的RhoA介导的旁分泌信号，驱动肌成纤维细胞的转化和激活； 2)确定RhoA信号是否是肌成纤维细胞在活化的FBS中增殖的必要条件和充分条件； 3)利用新型纳米靶向技术将RhoA效应器的细胞特异性抑制物输送到 改善纤维化，防止心脏疾病进展。这些数据将第一次得到验证 时间，RhoA通路在体内纤维化反应中的首要地位，并将识别新的 治疗心脏纤维化和心力衰竭的靶点和治疗策略。

7. Project Summary/Abstract Heart failure is a progressive disease characterized by cardiomyocyte (CM) loss, interstitial fibrosis, loss of ventricular compliance and chamber remodeling. CMs change in response to pathological stimuli, altering their cell morphology, increasing protein synthesis and upregulating fetal genes. Though initially compensatory, these changes eventually become maladaptive, inducing fibrosis and adverse cardiac responses. Cardiac fibroblasts (FBs) are implicated in regulating aspects of this deleterious profile, but specific molecular mechanisms regulating their function remain unclear. FBs are, however, known to be significant effectors of cardiac function, where they act as principal determinants of ventricular remodeling and fibrosis in response to stress and injury. In chronic disease states, however, this fibrotic response leads to reduced wall compliance, decreased diffusion efficiency, and arrhythmias. Thus, limiting fibrosis and the activity of myofibroblasts under conditions of chronic stress would be beneficial in preventing heart failure. As part of our original grant, we generated mice with CM- specific deletion of RhoA, a Ras-related small G protein, to determine the molecular mechanisms of its activity specifically in myocardium. In response to chronic stress, we found that hearts from these mice developed accelerated dilation, with significant loss of contractile function. However, and despite the heart failure pathology, they also had significantly reduced cardiac fibrosis, with a demonstrated decrease in transcriptional activation of genes involved in the fibrotic response, including the serum response factor (SRF) and myocardin related transcription factors (MRTF). Together, our data suggest that RhoA is a critical and nodal enzyme in cardiac injury, functioning to both preserve contractility and to mediate activation of profibrotic genes. Here, in this renewal application, we propose to specifically interrogate the functional and mechanistic role(s) for RhoA signaling in fibrosis. We hypothesize that RhoA modulates FB activity both directly, within the activated FB, as well as indirectly, through CM-specific paracrine signals, to mediate myofibroblast activation and/or response to cardiac stress and injury. We propose to 1) examine the CM-specific RhoA-mediated paracrine signals that drive myofibroblast transformation and activation; 2) determine if RhoA signaling is necessary and sufficient for myofibroblast propagation in activated FBs; 3) utilize novel nanoparticle targeted technology to deliver cell specific inhibitors of RhoA effectors to ameliorate fibrosis and to prevent cardiac disease progression. These data will verify, for the first time, the primacy of the RhoA pathway in the fibrotic response in vivo and will identify novel targets and therapeutic strategies for the treatment of cardiac fibrosis and heart failure.