Role of VEGF in Glomerular Endothelial Health & Diseases

描述(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)、血栓性微血管病理性紫癜(TTP)、肾移植排斥反应和各种毛细血管内肾小球肾炎。然而，这些疾病中内皮细胞损伤和蛋白尿的机制尚不清楚。在肾小球疾病如肾小球肾炎和TTP的实验模型中，血管内皮生长因子(VEGF)不仅是肾小球发生和肾脏发育所必需的分子，而且对肾小球毛细血管的修复也很重要。在非疾病状态下，血管内皮生长因子在成人肾小球中也大量表达，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，在PE患者中，胎盘产生过量的SFIT-1(一种循环中的血管内皮生长因子拮抗剂)是导致蛋白尿、高血压和。肾小球内皮细胞增生症，PE的经典病理损害。此外，最近在肾小球足细胞特异性的血管内皮生长因子基因敲除小鼠中发现了大量的蛋白尿并伴有肾小球内皮细胞增生症。此外，在临床癌症试验中使用血管内皮生长因子信号抑制剂已导致人类出现蛋白尿和高血压。因此，我们推测，血管内皮生长因子及其受体不仅在维持肾小球内皮健康方面发挥重要作用，而且在维持正常的肾小球完整性和蛋白尿屏障方面也发挥着重要作用。拮抗剂阻断血管内皮细胞生长因子信号转导，短期内可导致蛋白尿，长期可导致肾小球硬化。在这个提案中，我们将首先描述我们的SFIT-1诱导的蛋白尿和血管内皮细胞增生症的模型，以了解在血管内皮生长因子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的血管内皮生长因子受体来阐明介导蛋白尿屏障和维持内皮健康的血管内皮生长因子信号通路，随后将使用血管内皮生长因子受体激动剂(如只激活FIT-1而不激活Fik-L的胎盘生长因子)和针对各种血管内皮生长因子受体的中和抗体在大鼠身上进行明确的体内试验。然后，我们将研究阻断血管内皮生长因子对大鼠肾脏和血管的长期影响，特别是寻找肾小球硬化和高血压的发展。最后，我们将研究血管内皮生长因子抑制剂和血管内皮生长因子激动剂在抗Thyl1肾炎中的作用，这是一种具有良好特征的肾小球肾炎实验模型，在该模型中，毛细血管修复被认为是肾炎的重要解决方法。总之，这些研究将有助于我们实现了解血管内皮生长因子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，并可能导致治疗肾小球内皮疾病的新选择，以及澄清正在开发的用于癌症等其他疾病的血管内皮生长因子信号抑制剂的肾脏毒性。

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.