Regulation of AT1R-signaling and pathology in vessels through microRNA

描述（由申请人提供）：我们研究项目的长期目标是阐明microRNA机制，该机制改变了血管紧张素II 1型受体（AT 1 R）过度活性对基因的正常调节。血管紧张素II（AngII）是肾素-血管紧张素系统调节心血管稳态的经典介质。该受体调节AT 1 R阻断剂（ARB）靶向的基因表达，ARB是一类广泛使用的抗高血压药物，目前正在试验中用于预防血管、肾脏和心脏肥大、主动脉粥样硬化、血管纤维化、乳腺肿瘤生长和血管生成。ARB抑制肾脏、血管和心脏细胞中的AT 1 R具有保护作用，但受体的激活会导致相应器官/组织的肥大和进行性纤维化。 在初步研究中，我们发现AT 1 R的慢性激活通过转录和转录后机制来解除基因表达。为了将基因表达失调与肥大和纤维化直接联系起来，我们分析了AT 1 R TG小鼠主动脉、心脏以及HL 1-AT 1 R（心肌细胞）和VSMC-AT 1 R细胞系中的mRNA和microRNA（miRNA）表达。在所有实验模型中，典型的转录和miRNA调控机制都发生了显著改变。在另一项研究中，我们发现扩张型心肌病患者心脏中的miRNA表达谱发生了显著改变。改变的miRNAs靶向基因网络，这些基因网络确实解释了人类心力衰竭的代偿性重塑。这些新的研究表明，mRNA和miRNA谱一起有助于健康和疾病中的AT 1 R生物学。我们目前的建议将集中在两个AT 1 R调节的microRNA的新作用：miR-205和mir-483。提出了三个特定的目的来检验特定的转录和转录后调节机制使典型的肥大和纤维化信号传导的动力学向疾病内涵倾斜的假设。它们是：（i）确定改变肥大和纤维化模型中的关键信号传导组分的miR-205机制，（ii）确定上调肾素血管紧张素系统的miR-483机制，和（iii）确定miR-205和miR-483的生物发生和稳定性的AT 1 R调节机制。 如果AT 1 R活性没有得到适当的调节，AngII刺激会变成慢性的，并可能损害组织，以及导致血管、肾脏和心脏的慢性疾病。清楚地了解这些机制对于改善ARB的治疗应用非常重要。这些拟议的研究将推进我们对AT 1 R信号传导导致肥大和纤维化的生物学知识。该知识库在理解正常功能的主动脉、脑、肾和心脏中的脉管系统以及心力衰竭、动脉粥样硬化和主动脉瘤的病理学方面具有潜在的相关性。

DESCRIPTION (provided by applicant): The long-term goal of our research program is to elucidate microRNA mechanisms that alter normal regulation of genes in response to overactivity of the angiotensin II type 1 receptor (AT1R). Angiotensin II (AngII) is the classical mediator of the effects of the renin-angiotensin system on the cardiovascular homeostasis. This receptor regulates gene expression targeted by the AT1R-blockers (ARB), a widely used class of anti- hypertensive drugs that are currently in trial for the prevention of vascular, renal and cardiac hypertrophy, aortic aneurism, vascular fibrosis, breast tumor growth and angiogenesis. Inhibition of AT1R in renal, vascular and cardiac cells by ARBs is protective, but the activation o the receptor causes hypertrophy and progressive fibrosis of the respective organs/tissues. In preliminary studies we have discovered that chronic activation of AT1R deregulates gene expression through both transcriptional and post-transcriptional mechanisms. To directly link deregulation of gene expression to hypertrophy and fibrosis, we profiled mRNA and microRNA (miRNA) expression in the AT1R TG mice aorta, heart, and in HL1-AT1R (cardiomyocyte) and the VSMC-AT1R cell lines. Typical transcriptional and miRNA regulatory mechanisms are significantly altered in all of the experimental models. In a separate study, we have shown significantly altered miRNA expression profile in dilated cardiomyopathy human hearts. The altered miRNAs target gene networks that do account for compensatory remodeling in human heart failure. These novel studies suggest that mRNA and miRNA profiles, together, contribute to AT1R biology in health and disease. Our current proposal will focus on the novel roles of two AT1R-modulated microRNAs: miR-205 and mir-483. Three Specific Aims are proposed to test the hypothesis that specific transcriptional and post-transcriptional regulatory mechanisms tilt the dynamics of typical hypertrophy and fibrosis signaling towards a disease connotation. They are: (i) to determine miR-205 mechanisms which alter critical signaling components in models of hypertrophy and fibrosis, (ii) to determine the miR-483 mechanism of up-regulation of the rennin angiotensin system, and (iii) to determine the AT1R regulated mechanisms of biogenesis and the stability of miR-205 and miR-483. If the AT1R activity is not regulated properly, AngII stimulus becomes chronic and can damage the tissue, as well as contribute to chronic disorders of blood vessels, kidney and heart. A clear understanding of these mechanisms is important to improve the therapeutic application of ARBs. These proposed studies will advance our knowledge of the biology of AT1R signaling causing hypertrophy and fibrosis. There is potential relevance for this knowledge base in understanding normal functioning aorta, vasculature in brain, kidney and heart, as well as the pathology of heart failure, atherosclerosis and aortic aneurysm.