Angiopoietin-2 Signaling Targeted Therapeutics for Arteriovenous Malformations

项目摘要 遗传性出血性毛细血管扩张症（HHT）是一种血管遗传性疾病，其特征是血管扩张，渗漏， 小血管（毛细血管扩张）和动脉和静脉之间不适当的脆弱连接， 动静脉畸形（AVM）。HHT患者在主要器官的特定子集中发生AVM， 可能破裂导致严重出血和贫血，以及动脉瘤、中风甚至死亡。原因 HHT与转化生长因子-β（TGF-β）信号通路有关，超过90%的患者 在激活素受体样激酶1（Acvrl 1/Alk 1）或内皮糖蛋白中表现出杂合性功能丧失突变 (Eng)共受体，或下游转录因子，Smad相关蛋白4（Smad 4）。尽管知道 虽然我们对致病突变的认识还存在很大差距， 负责HHT病理的信号传导组分。此外，目前还没有治愈HHT的方法。我们 已经发现Alk 1、Eng和Smad 4功能丧失的直接下游，血管生成因子和 Tie 2受体的拮抗配体血管生成素-2（Angpt 2/ANG 2）在转录上升高， HHT血管病理学; ANG 2中和在两种HHT小鼠模型中有效减少AVM病理学。 此外，Alk 1信号传导的丧失导致了对转录和信号传导的稳健且一致的抑制。 Tek/Tie 2.总之，这些观察结果强烈支持ANG 2升高且Tie 2升高的工作模型 在HHT中AVM发展的致病过程中，信号传导受到抑制。此外，代谢 PI 3 K/Akt/mTOR通路在HHT中失调以维持AVM的发展，然而其与ANG 2 前AVM信号不清楚。使用不同遗传形式的HHT和原发性内皮细胞 细胞（EC），我们已经获得了强有力的试验数据，表明ANG 2-Tie 2失调，与 增强FoxO 1转录活性和通过CXCR 4连续过度激活mTOR通路 趋化因子信号传导，驱动HHT表型。本应用程序的中心目标是回答3个基本问题 问题：1）ANG 2升高和Tie 2信号抑制如何指导AVM发病机制，2） mTOR过度激活受ANG 2-Tie 2信号转导失调控制的机制，以及3） 普遍靶向ANG 2和新鉴定的ANG 2调节的致病性信号级联的方法 有效治疗HHT血管病变？我们将通过测试以下特定的 目的：1）评估在最受生理影响的器官中的ANG 2和Tie 2信号传导失调， 确定ANG 2抑制是否普遍阻断HHT小鼠模型中的血管病理; 2）确定FoxO 1 对ANG 2和CXCR 4升高和HHT血管病理学的贡献;和3）测试TGF-β-Tie 2- FoxO 1介导的CXCR 4升高驱动mTOR激活。这些研究将推动我们的机械 了解AVM的发病机制，并发现治疗HHT的新的潜在靶点。

PROJECT SUMMARY Hereditary Hemorrhagic Telangiectasia (HHT) is a vascular genetic disorder characterized by enlarged, leaky small vessels (telangiectasias) and inappropriate, fragile connections between arteries and veins called arteriovenous malformations (AVMs). HHT patients develop AVMs in a specific subset of major organs, which can rupture causing severe hemorrhage and anemia, as well as aneurysms, stroke and even death. Causes of HHT are linked to the Transforming Growth Factor-beta (TGF-beta) signaling pathway, with over 90% of patients exhibiting heterozygous loss-of-function mutations in the Activin receptor-like kinase 1 (Acvrl1/Alk1) or Endoglin (Eng) co-receptors, or the downstream transcription factor, Smad-related protein 4 (Smad4). Despite knowing the causative mutations, a significant gap remains in our understanding of the immediate TGF-beta downstream signaling components responsible for HHT pathologies. Furthermore, no cure is currently available for HHT. We have found that directly downstream of Alk1, Eng and Smad4 loss-of-function, the angiogenic factor and antagonistic ligand to the Tie2 receptor, angiopoietin-2 (Angpt2/ANG2), is transcriptionally elevated to trigger HHT vascular pathologies; ANG2 neutralization efficiently reduced AVM pathology in two HHT mouse models. In addition, loss of Alk1 signaling led to a robust and consistent transcriptional and signaling inhibition of Tek/Tie2. Together, these observations strongly support the working model that ANG2 is elevated and Tie2 signaling is repressed during the pathogenic process of AVM development in HHT. Moreover, the metabolic PI3K/Akt/mTOR pathway is deregulated in HHT to sustain AVM development, however its connection to ANG2 pro-AVM signals is unclear. Using mouse models of the different genetic forms of HHT and primary endothelial cells (ECs), we have obtained strong pilot data indicating that ANG2-Tie2 deregulations, working in concert with enhanced FoxO1 transcriptional activity and sequential overactivation of the mTOR pathway via CXCR4 chemokine signaling, drive HHT phenotypes. The central objective of this application is to answer 3 fundamental questions: 1) how does ANG2 elevation and Tie2 signaling repression direct AVM pathogenesis, 2) what is the mechanism by which mTOR overactivation is controlled by ANG2-Tie2 signaling deregulations and 3) are approaches targeting ANG2 and the newly identified ANG2-regulated pathogenic signaling cascade universally effective in treating HHT vascular pathologies? We will address these topics by testing the following specific aims: 1) Assess ANG2 and Tie2 signaling deregulations in the most physiologically affected organs and determine if ANG2 inhibition universally blocks vascular pathologies in HHT mouse models; 2) Determine FoxO1 contributions to ANG2 and CXCR4 elevations and HHT vascular pathologies; and 3) Test if TGF-beta-Tie2- FoxO1-mediated CXCR4 elevations drive mTOR activation. These studies will advance our mechanistic understanding of AVM pathogenesis and uncover new potential targets for treating of HHT.