mTOR and VEGFR2 pathways in HHT pathogenesis

项目总结/摘要（描述） 遗传性出血性毛细血管扩张症（HHT）是一种常染色体显性遗传病，其特征是： 发生全身性和可能危及生命的血管畸形，称为动静脉畸形 （反车辆地雷）。HHT突变主要存在于ALK 1和ENG基因中，并导致BMP 9/10功能丧失。 内皮细胞（EC）中的ALK 1-ENG信号传导。最近的证据表明，HHT发病机制和AVM 这些疾病的发展需要内皮mTOR和VEGFR 2途径的异常过度活化。整体 该计划的目标是描述mTOR和VEGFR 2过度激活的精确机制， ALK 1-ENG功能丧失，并确定这些机制的靶向是否具有疾病修饰作用。 在HHT的细胞和小鼠模型中的性质和治疗潜力。使用全转录组询问， 我们的初步研究表明，mTOR和VEGFR 2的联合药理学抑制 证明了在校正肿瘤中的病理基因表达特征方面的显著协同作用和功效。 HHT的BMP 9/10-免疫阻断（BMP 9/10 ib）小鼠模型。引人注目的是，双重mTOR-VEGFR 2抑制阻断了 血管病理学和视网膜、肝脏、肺和粘膜中的AVM，以避免BMP 9/10 ib中的出血和贫血 小鼠从机制上讲，我们的初步数据显示，在ALK 1-ENG抑制的下游， 血管生成素-2（ANG 2）/Tie 2受体信号转导是mTOR-VEGFR 2激活和AVM的重要触发因素 HHT小鼠的发育。因此，我们的数据支持HHT发病机制是由以下因素引起的工作模型： 有缺陷的ANG 2-mTOR-VEGFR 2通路，针对这些机制缺陷的干预措施可能 在HHT中提供治疗益处。基于这些结果，我们在目标1中提出评估内皮细胞是否 mTOR和VEGFR 2是独立激活的，以及它们是否都是AVM发展所需的。 HHT小鼠。为此，药理学和基因缺失方法独立地靶向mTOR， VEGFR 2将用于两种HHT小鼠模型：BMP 9/10 ib小鼠和新产生的敲入（KI）小鼠。 表达HHT引起的ALK 1突变的小鼠。在目标2中，我们将描述mTOR的确切机制 和通过ANG 2/Tie 2信号传导的VEGFR 2过度活化，在HHT小鼠体内和在原代EC体外， 包括在HHT患者血液生长EC中。最后，在目标3中，我们将确定Tie 2去阻遏是否 阻断HHT小鼠的血管病变。

PROJECT SUMMARY/ABSTRACT (DESCRIPTION) Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant genetic disorder characterized by the development of systemic and potentially life-threatening vascular anomalies called arteriovenous malformations (AVMs). HHT mutations are mostly found in the ALK1 and ENG genes and lead to a loss-of-function of BMP9/10- ALK1-ENG signaling in endothelial cells (ECs). Recent evidence suggests that HHT pathogenesis and AVM development require the aberrant overactivation of the endothelial mTOR and VEGFR2 pathways. The overall goal of this program is to characterize the precise mechanisms of mTOR and VEGFR2 overactivations upon ALK1-ENG loss-of-function, and determine whether targeting of these mechanisms has disease-modifying properties and therapeutic potential in cell and mouse models of HHT. Using whole-transcriptome interrogation, our preliminary investigation has shown that combined pharmacological inhibition of mTOR and VEGFR2 demonstrated a remarkable synergy and efficacy in correcting a pathological gene expression signature in the BMP9/10-immunoblocked (BMP9/10ib) mouse model of HHT. Strikingly, dual mTOR-VEGFR2 inhibition blocked vascular pathology and AVMs in the retina, liver, lungs, and mucosa to avert bleeding and anemia in BMP9/10ib mice. Mechanistically, our preliminary data revealed that, downstream of ALK1-ENG inhibition, changes in angiopoietin-2 (ANG2)/Tie2 receptor signaling were important triggers for mTOR-VEGFR2 activation and AVM development in HHT mice. Therefore, our data support the working model that HHT pathogenesis is caused by defective ANG2-mTOR-VEGFR2 pathways, and that interventions targeting these mechanistic defects might provide therapeutic benefit in HHT. Based on these results, we propose in Aim 1 to assess whether endothelial mTOR and VEGFR2 are independently activated and whether they are both required for AVM development in HHT mice. To this end, pharmacological and gene deletion approaches independently targeting mTOR and VEGFR2 will be employed in two HHT mouse models: the BMP9/10ib mice and a newly generated knockin (KI) mouse expressing a HHT-causing ALK1 mutation. In Aim 2, we will delineate the precise mechanism of mTOR and VEGFR2 overactivation by ANG2/Tie2 signaling, both in vivo in HHT mice and in vitro in primary ECs, including in HHT patient blood outgrowth ECs. Lastly in Aim 3, we will determine whether Tie2 derepression blocks vascular pathology in HHT mice.