VEGF Signaling in Endothelial and Glomerular Epithelial Cells in Preeclampsia

描述(由申请人提供)：先兆子痫是一种妊娠特有的疾病，临床特征是妊娠20周后出现高血压和蛋白尿。这种情况的病因和发病机制仍然不清楚，导致未能制定具体的预防和治疗策略。最近的研究表明，子痫前期与血管内皮生长因子(VEGF)的可溶性受体水平升高有关。这种可溶性受体，通常被称为sFlt-1(来源于fms样酪氨酸激酶受体-1)，可以结合和中和血管内皮生长因子，从而降低怀孕期间活跃的血管生成所需的游离血管内皮生长因子水平。我们推测，低水平的游离VEGF可能通过双重方式参与子痫前期的发病：1)内皮功能障碍；2)肾小球上皮细胞(足细胞)调节失调，分别导致两种主要的临床表现：高血压和蛋白尿。我们已经证明，与正常妊娠相比，患有严重子痫前期的女性肾脏组织中缝隙隔膜蛋白neparin的表达下调。狭缝隔膜是一种特殊的细胞间连接，连接相邻的足细胞，代表肾脏中主要的、大小选择性的过滤器。此外，我们还发现，先兆子痫患者的蛋白尿与尿液中有活力的足细胞丢失有关，即足细胞尿。在特定的目标1中，我们将研究血浆sFlt-1水平升高、裂隙横隔膜蛋白(包括neaffin)下调和足细胞尿之间的相关性，并探索足细胞尿作为先兆子痫可能的早期标志的作用。我们推测足囊尿症可能发生在蛋白尿和先兆子痫发展之前。 我们还假设，内皮功能障碍是导致高血压的先兆子痫的一个标志，部分是由低游离血管内皮生长因子水平介导的，这可能导致内皮一氧化氮合酶活性和一氧化氮产生减少。这一假说将在特定目标2中得到验证。在特定目标3中，我们将研究先兆子痫患者中，有缺陷的血管内皮生长因子信号可能下调neparin、扰乱裂隙横隔膜、导致足细胞尿并最终导致蛋白尿的机制。这些研究将提供对先兆子痫病理生理学基础的基本机制的见解，这对于开发更具体的诊断和治疗方法至关重要。 相关性：在美国，先兆子痫影响5%的妊娠，并且仍然是母婴发病率和死亡率的主要原因之一。目前，唯一的治疗方法是分娩，这往往会导致早产和新生儿发病率高。开发更有效的治疗策略至关重要地取决于对潜在致病机制的更好理解。

DESCRIPTION (provided by applicant): Preeclampsia is a pregnancy-specific disorder clinically characterized by hypertension and proteinuria that occurs after 20 weeks of gestation. The etiology and pathogenesis of this condition remain elusive, resulting in a failure to develop specific preventive and treatment strategies. Recent studies have provided evidence that preeclampsia is associated with elevated levels of the soluble receptor for vascular endothelial growth factor (VEGF). This soluble receptor, commonly referred to as sFlt-1 (from fmslike tyrosine kinase receptor-1), may bind and neutralize VEGF and thus decrease free VEGF levels that are required for active angiogenesis in pregnancy. We postulate that low free VEGF levels may contribute to the pathogenesis of preeclampsia in a dual fashion by causing: i) endothelial dysfunction and ii) glomerular epithelial cell (podocyte) dysregulation, leading to the two main clinical findings of preeclampsia, hypertension and proteinuria, respectively. We have demonstrated that nephrin, a slit diaphragm protein, is down-regulated in kidney sections of women who had severe preeclampsia compared to normal pregnancies. The slit diaphragm is a specialized cell-to-cell junction that connects neighboring podocytes and represents the main, size-selective filter in the kidney. In addition, we have shown that proteinuria in preeclampsia is associated with urinary loss of viable podocytes, i.e., podocyturia. In Specific Aim 1, we will study the correlations among elevated levels of plasma sFlt-1 levels, down-regulation of slit diaphragm proteins (including nephrin), and podocyturia, and explore the role of podocyturia as a possible early marker for preeclampsia. We postulate that podocyturia may occur before proteinuria and preeclampsia develop. We also hypothesize that endothelial dysfunction, a hallmark of preeclampsia that leads to hypertension, is mediated in part by low free VEGF levels that may cause a decrease in endothelial nitric oxide synthase activity and nitric oxide production. This hypothesis will be tested in Specific Aim 2. In Specific Aim 3, we will study the mechanisms by which defective VEGF signaling may down-regulate nephrin, disrupt the slit diaphragm, lead to podocyturia and, ultimately, proteinuria in preeclampsia. These studies will provide insights into basic mechanisms underlying the pathophysiology of preeclampsia, which are essential for developing more specific diagnostic and treatment approaches. Relevance: Preeclampsia affects 5% of pregnancies in the USA and remains one of the leading causes of both maternal and fetal morbidity and mortality. Currently, the only therapy is delivery, which frequently leads to premature birth and high neonatal morbidity. Development of more effective treatment strategies is critically dependent upon better understanding of underlying pathogenic mechanisms.