Role of VEGF in Glomerular Endothelial Health & Diseases

描述（由申请人提供）：肾小球内皮损伤在几种蛋白尿性肾脏疾病的发病机制中起重要作用，如先兆子痫（PE）、血栓性微血管病性紫癜（TTP）、肾移植排斥反应和各种毛细血管内肾小球肾炎。 然而，这些疾病中内皮损伤和蛋白尿的机制知之甚少。 血管内皮生长因子（vascular endothelial growth factor，VEGF）不仅是肾小球形成和肾脏发育的必需分子，而且在肾小球疾病如肾小球肾炎和TTP的实验模型中对肾小球毛细血管修复也很重要。 VEGF在非疾病状态下也在成人肾小球中大量表达，但其在肾小球健康和疾病中的作用尚不清楚。 最近，我们已经证明，胎盘分泌过量的sFIt-1（一种循环中的VEGF拮抗剂）是导致PE患者蛋白尿、高血压和高血压的原因。肾小球内皮增生，PE的典型病理损害。 此外，大量的蛋白尿与肾小球内皮细胞增生最近已被描述在肾小球足细胞特异性VEGF基因敲除小鼠。 此外，VEGF信号传导抑制剂在临床癌症试验中的使用导致人类蛋白尿和高血压。因此，我们推测VEGF及其受体不仅在维持肾小球内皮健康方面，而且在维持正常肾小球完整性和蛋白尿屏障方面发挥重要作用。拮抗剂破坏VEGF信号传导可能会导致短期蛋白尿和长期肾小球硬化。在这个提议中，我们将首先描述我们的sFIt-1诱导的蛋白尿和内皮增生模型，以了解VEGF缺乏状态下蛋白尿的机制。然后，我们将在体外肾小球内皮细胞培养研究中使用嵌合VEGF受体阐明介导针对蛋白尿的屏障并维持内皮健康的VEGF信号传导途径，随后在大鼠中使用VEGF受体激动剂（如仅激活Flt-I而不激活FIk-I的胎盘生长因子）和针对各种VEGF受体的中和抗体进行确定性体内研究。 然后，我们将研究VEGF阻断大鼠肾脏和血管的长期后果，特别是寻求肾小球硬化和高血压的发展。 最后，我们将研究VEGF抑制剂和VEGF激动剂在抗Thyl.1肾炎中的作用，抗Thyl.1肾炎是肾小球肾炎的良好表征的实验模型，其中毛细血管修复被认为对于肾炎的消退是重要的。总之，这些研究将有助于我们实现理解VEGF和肾小球内皮细胞功能障碍在蛋白尿发病机制中的作用的目标，并可能为肾小球内皮疾病提供新的治疗选择，并阐明正在开发的用于其他疾病（如癌症）的VEGF信号传导抑制剂的肾毒性特征。

DESCRIPTION (provided by applicant): Glomerular endothelial damage plays an important role in the pathogenesis of several proteinuric renal disorders such as preeclampsia (PE), thrombotic microangiopathic purpuras (TTP), renal transplant rejection and various endocapillary glomerulonephritides. However, the mechanisms of endothelial damage and proteinuria in these disorders are poorly understood. It has been shown that vascular endothelial growth factor (VEGF) is not only an essential molecule for glomerulogenesis and kidney development, but also important for glomerular capillary repair in experimental models of glomerular disorders such as glomerulonephritides and TTP. VEGF is also abundantly expressed in the adult glomerulus during nondiseased states, but its role in glomerular health and disease is unclear. Recently, we have demonstrated that excess placental production of sFIt-1 (a circulating VEGF antagonist) in patients with PE is responsible for proteinuria, hypertension and. qlomerular endotheliosis, the classic pathologic lesion of PE. Moreover, massive proteinuria with glomerular endotheliosis has been recently described in glomerular podocyte-specific VEGF knockout mice. Additionally, VEGF signaling inhibitors usage in clinical cancer trials have resulted in proteinuria and hypertension in humans. Therefore, we hypothesize that VEGF and its receptors play an important role in not only maintaining glomerular endothelial health but also in maintaining normal glomerular integrity and the barrier to proteinuria. Disruption of VEGF signaling by antagonists may result in proteinuria in the short term and glomerulosclerosis in the long term. In this proposal, we will first characterize our sFIt-1 induced model of proteinuria and endotheliosis to understand the mechanisms of proteinuria in VEGF-deficient states. We will then elucidate the VEGF signaling pathways that mediate the barrier against proteinuria and maintain endothelial health using chimeric VEGF receptors in glomerular endothelial cell culture studies in vitro to be followed by definitive in vivo studies in rats using VEGF receptor agonists (such as placental growth factor that activates only Fit-1 and not FIk-l) and neutralizing antibodies against various VEGF receptors. We will then study the long-term renal and vascular consequences of VEGF blockade in rats specifically seeking the development of glomerulosclerosis and hypertension. Finally, we will study the effects of VEGF inhibitors and VEGF agonists in anti-Thyl.1 nephritis, a well-characterized experimental model of glomerulonephritis, in which capillary repair is thought to be important for the resolution of nephritis. Together, these studies will facilitate us to achieve our goal of understanding the role of VEGF and glomerular endothelial cell dysfunction in the pathogenesis of proteinuria and may lead to novel therapeutic options for glomerular endothelial diseases as well as clarify the renal toxicity profile of VEGF signaling inhibitors being developed for other diseases such as cancer.