Platelets and complement in antibody-mediated rejection

项目摘要/摘要 抗体是肾移植急性和慢性排斥反应的主要原因。一些病态的 进展为移植物功能障碍的急性抗体介导的排斥反应(AMR)的表现 已定义。然而，显然并不是AMR的所有调解人都被确定了。潜在的 移植物受损前的可逆期在临床研究中即使用方案也很难解决。 活组织检查，因为患者本身存在不可控的变量。我们已经在体外和体内使用了 模型证明抗体刺激内皮细胞分泌von Willebrand因子和P- 选择素。我们认为活化的血小板在早期AMR中具有关键功能，并极大地扩大 通过与内皮细胞和白细胞相互作用而引起的炎症。我们报告了血小板第4因子和 5-羟色胺在移植肾中的积聚浓度是其他药物的100-1000倍 血小板运输的介体。大量的血小板因子4在同种异体移植物中的定位 对巨噬细胞功能的多重影响。这些交互作用特别相关，因为 巨噬细胞渗入是AMR的一个特征。从血小板释放5-羟色胺也 有可能将白细胞招募到肾移植中。此外，血小板可以刺激单核细胞和 炎症部位的巨噬细胞，内皮细胞在炎症部位间接释放大量的 细胞外基质蛋白透明质酸。活化的血小板表达的透明质酸酶2将HA裂解成 作为危险信号的片段通过Toll样受体刺激巨噬细胞。潜力 调节AMR中的血小板活化的有益效果尚未得到充分的测试。除了屏蔽之外 特异性的血小板介体，我们发现临床相关的补体抑制剂是一种 减少血小板在同种异体移植物中的定位。我们提出的假设是抗体启动了血小板，并 肾移植中增强白细胞与血管相互作用的内皮反应 在AMR期间。我们将在3个具体目标上检验这一假说：1)检测血小板衍生介质在 直接对肾移植造成损伤；2)检测C1抑制剂对肾移植的多重影响。 激活血小板和巨噬细胞；以及3)检测血管内皮细胞释放的透明质酸的作用 并在肾移植中被血小板裂解，增加炎症和促进纤维化。至 为了实现这些特定的目标，我们将在肾移植中使用AMR的小鼠模型 由费尔柴尔德博士和Valujskikh博士在上一个资助期的项目1和3中开发，以及 被动迁移模型是在我们的项目2中开发的。我们针对每个特定目标的目标是理解 血小板参与AMR的机制，识别血小板诱导的损伤的生物标志物和 测试潜在的治疗干预措施。

Project Summary / Abstract Antibodies are a major cause of acute and chronic rejection in renal transplants. Some pathologic manifestations of acute antibody-mediated rejection (AMR) that has progressed to graft dysfunction have been defined. However, it is evident that not all of the mediators of AMR have been identified. The potentially reversible stages that precede graft impairment are difficult to resolve in clinical studies even with protocol biopsies because of uncontrollable variables inherent among patients. We have used in vitro and in vivo models to demonstrate that antibodies stimulate endothelial cells to exocytose von Willebrand factor and P- selectin. We propose that activated platelets have critical functions in early AMR and greatly expand inflammation by interacting with endothelial cells and leukocytes. We reported that platelet factor 4 and serotonin accumulated in renal allografts at 100- to 1000-fold higher concentrations compared with other platelet-transported mediators. The localization of large quantities of platelet factor 4 in the allograft has multiple consequences on macrophage function. These interactions are particularly relevant because macrophage infiltrates in human biopsies are a characteristic of AMR. Release of serotonin from platelets also has potential to recruit leukocytes to renal transplants. In addition, platelets can stimulate monocytes and macrophages indirectly at sites of inflammation where endothelial cells release increased amounts of the extracellular matrix protein hyaluronan. Hyaluronidase 2 expressed by activated platelets cleaves HA into fragments that act as danger signals to stimulate macrophages through toll like receptors. The potential beneficial effects of modulating platelet activation in AMR have not been tested fully. In addition to blocking specific platelet mediators, we have found that clinically relevant complement inhibitors are one approach to decrease platelet localization in allografts. We propose the hypothesis that antibodies initiate platelet and endothelial responses that augment leukocyte interactions with blood vessels in renal transplants during AMR. We will test this hypothesis in 3 specific aims: 1) Test the role of platelet-derived mediators in directly causing injury to renal transplants; 2) Test the multiple effects of C1 inhibitor on recruitment and activation of platelets and macrophages; and 3) Test the role of hyaluronan released by vascular endothelium and cleaved by platelets in augmenting inflammation and contributing to fibrosis in renal transplants. To accomplish these specific aims, we will use mouse models of AMR in renal transplants that have been developed by Drs. Fairchild and Valujskikh in Projects 1 and 3 in the previous funding period as well as the passive transfer models developed in our Project 2. Our goals for each specific aim are to understand mechanisms by which platelets contribute to AMR, identify biomarkers of platelet-induced injury and test potential therapeutic interventions.