Angiopoietin-2 Signaling Targeted Therapeutics for Arteriovenous Malformations

项目总结 遗传性出血性毛细血管扩张症(HHT)是一种以增大、渗漏为特征的血管遗传性疾病 小血管(毛细血管扩张)和动脉和静脉之间不适当、脆弱的连接称为 动静脉畸形(Avms)。HHT患者在主要器官的特定亚群中发生动静脉畸形，这 破裂可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，90%以上的患者 表现出激活素受体样激酶1(Acvrl1/Alk1)或内源性的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(Smad4)。尽管知道 致病突变，在我们对直接的转化生长因子-β下游的理解上仍然存在着显著的差距 负责HHT病理的信号组件。此外，目前还没有治愈HHT的方法。我们 已发现在Alk1、Eng和Smad4功能丧失的直接下游，血管生成因子和 Tie2受体的拮抗配体血管生成素-2(Angpt2/Ang2)在转录水平上上调，以触发 HHT血管病理；ANG2中和有效地减少了两个HHT小鼠模型的AVM病理。 此外，Alk1信号的丢失导致了对转录和信号的抑制 Tek/Tie2.总之，这些观察结果有力地支持了工作模型，即ANG2被提升，Tie2被提升 在HHT的AVM发病过程中，信号转导受到抑制。此外，新陈代谢 PI3K/Akt/mTOR通路在HHT中被解除调控以维持AVM的发展，但其与ANG2的联系 支持AVM的信号尚不清楚。使用不同遗传形式的HHT和初级内皮细胞的小鼠模型 细胞(ECs)，我们已经获得了强有力的试点数据，表明ANG2-Tie2放松管制，与 通过CXCR4增强FoxO1转录活性和mTOR通路的顺序过度激活 趋化因子信号，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)ANG2升高和Tie2信号抑制如何指导AVM的发病；2)AVM的发病机制是什么？ ANG2-Tie2信号失控控制mTOR过度激活的机制和3) 针对ANG2和新发现的ANG2调节的致病信号级联反应的途径普遍存在 能有效治疗高血压血管病变吗？我们将通过测试以下特定主题来解决这些主题 目的：1)评估ANG2和Tie2信号在最受生理影响的器官和 确定血管紧张素转换酶2抑制是否普遍阻断HHT小鼠模型的血管病变；2)测定FoxO1 对ANG2和CXCR4升高和HHT血管病理的作用；以及3)检测是否有转化生长因子-β-Tie2- Foxo1介导的CXCR4升高驱动mTOR激活。这些研究将推进我们的机械化 了解AVM的发病机制，为HHT的治疗发现新的潜在靶点。

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.