The role of VWF and platelets in BBB alterations associated with hypoxia

描述（由申请人提供）：缺氧后复氧通常用作研究与缺血/再灌注相关的病理学的模型，因为后一种情况存在于包括中风在内的几种疾病状态中。在动物模型中，缺氧后再氧合已被证明会导致紧密连接蛋白异常、BBB细胞旁通透性增加和水肿，然而，导致这些病理的完整机制仍不明确。血管性血友病因子（vonWillebrand Factor，VWF）是一种仅由内皮细胞和巨核细胞合成的糖蛋白。虽然已知VWF由脑内皮细胞（CEC）大量表达，但关于VWF在内皮生物学中的作用，特别是在应激条件下在BBB的调节中的作用知之甚少。我们已经产生的数据表明，VWF缺陷型小鼠在全身缺氧/复氧模型中具有比野生型显著更低的BBB通透性。VWF是内皮细胞活化过程中血小板的主要配体，我们收集的初步数据支持血小板在暴露于缺氧的存活中的作用。血小板以其在止血和炎症中的作用而闻名，血小板与内皮和暴露的内皮下结合的主要配体是VWF。血小板可以激活内皮，但也被发炎的内皮激活。支持暴露于缺氧后血小板数量和功能改变的数据已经被记录。然而，研究得出了相互矛盾的结果，为这一领域的进步留下了很大的空间。有趣的是，血小板在人脑内皮细胞培养物中作为细胞旁通透性增加的增效剂的作用已经被记录，最近的文献表明血小板在涉及BBB的各种CNS疾病中的作用。VWF和血小板在血脑屏障生物学中的作用还未得到充分研究，需要进一步研究，因此我们的总体目标是确定VWF和血小板在应激条件下促进血脑屏障通透性的程度。为了实现这一点，我们将使用一个模型，广泛常压缺氧，然后复氧。在我们的第一个目标中，我们建议研究血浆vs.内皮下VWF在与全身缺氧/复氧相关的BBB通透性增加中的作用。其次，我们将确定血小板与VWF和内皮的相互作用导致BBB通透性增加的程度。我们建议使用敲除小鼠技术、血脑屏障通透性测定、共聚焦显微镜、血小板耗竭研究和紧密连接蛋白测定来实现这些目标。本提案中概述的研究旨在进一步了解脑微血管系统表达的糖蛋白如何与造血谱系的细胞类型相互作用，从而在缺氧期间影响BBB，因此与NINDS的使命直接相关，特别是神经环境部门。

DESCRIPTION (provided by applicant): Hypoxia followed by reoxygenation is commonly used as a model to investigate pathology associated with ischemia/reperfusion as the latter condition is present in several disease states including stroke. In animal models, hypoxia followed by reoxygenation has been shown to cause tight junction protein abnormalities, increased BBB paracellular permeability and edema however, a complete mechanism leading to these pathologies is still undefined. von Willebrand Factor (VWF) is a glycoprotein that is only synthesized by endothelial cells and megakaryocytes. While it is known that VWF is expressed abundantly by cerebral endothelial cells (CECs), very little is known about the role of VWF in endothelial biology, particularly, in regulation of the BBB under stressful conditions. Data we have generated demonstrate that VWF-deficient mice have significantly less BBB permeability than wild type in a model of generalized hypoxia/reoxygenation. VWF is a major ligand for platelets during endothelial activation and preliminary data we have gathered support a role for platelets in survival of exposure to hypoxia. Platelets are best known for their role in hemostasis and inflammation and the primary ligand for platelet binding to the endothelium and exposed subendothelium is VWF. Platelets can activate endothelium but are also activated by inflamed endothelium. Data supporting alteration of platelet number and function after exposure to hypoxia have been documented. However, studies have yielded conflicting results leaving much room for advancements in this field. Intriguingly, a role for platelets as potentiators of increased paracellular permeability in human brain endothelial cell cultures has been documented and recent literature suggests a role for platelets in various CNS diseases involving the BBB. The role of VWF and platelets in BBB biology is understudied and warrants further investigation, thus our overall objective is to determine the extent VWF and platelets promote BBB permeability under stressful conditions. To accomplish this, we will use a model of generalized normobaric hypoxia followed by reoxygenation. In our first aim, we propose to examine the role of plasma vs. subendothelial VWF in increased BBB permeability associated with generalized hypoxia/reoxygenation. Secondly, we will determine the extent that platelet interactions with VWF and the endothelium lead to increased BBB permeability. We propose to accomplish these aims using knock out mouse technology, BBB permeability assays, confocal microscopy, platelet-depletion studies and tight junction protein assays. The studies outlined in this proposal aim to further our understanding of how a glycoprotein expressed by brain microvasculature interacts with a cell type of hematopoietic lineage to influence the BBB during hypoxia and thus are directly relevant to the mission of NINDS, specifically the neural environment division.