Effect of Neutrophil Priming on Chemotaxis and Signaling

描述(由申请人提供)： 多形核白细胞(PMN)是一种固有的可移动的细胞类型，可以被引导向上移动趋化梯度。趋化运动是PMN在组织损伤或感染部位聚集所必需的，然而，为这些细胞提供导向所需的导航信号的机制尚不完全清楚。白色念珠菌是医院感染的第四大原因，手术后、创伤和免疫抑制患者的风险最高。尽管β-葡聚糖在系统性念珠菌病的病理生物学中的作用尚不清楚，但酵母细胞壁的主要成分β-葡聚糖已深入到系统性念珠菌病患者的血液中。这个实验室的最新发现表明，β-葡聚糖可以将PMN的随机迁移转化为直接迁移。这种转换是由白细胞β2整合素CR3(CD11b/CD18)识别β-葡聚糖介导的，是此前未知的β-葡聚糖对中性粒细胞功能的影响。我们工作的长期目标是了解在系统性真菌感染过程中，β-葡聚糖是如何影响宿主防御的。目前这项提议的重点是确定CR3识别β-葡聚糖改变中性粒细胞功能的机制。Aim I的实验将调查几个细胞内信号通路的作用，根据我们目前的发现，这些信号通路被假设为介导中性粒细胞在添加β-葡聚糖的基质上迁移的趋化能力增加。特殊目的II将应用一个具有良好特性的创伤模型来演示β-葡聚糖对宿主中性粒细胞对损伤的反应能力的影响。体外研究表明，β-葡聚糖激活CR3调节了β-葡聚糖家族整合素的功能。创伤模型将确定β-葡聚糖和/或系统性念珠菌病是否类似地改变了β1整合素在介导PMN进入损伤部位的功能。最后，几种致炎介质(内毒素、免疫复合体、尿激酶型纤溶酶原激活剂)与糖基磷脂酰肌醇(GPI)连接的受体(CD14、CD16、CD87)结合，后者又依赖CR3进行细胞内信号转导。《特殊目的III》将测试一种新的途径，即β1整合素串扰将GPL连接的受体从CR3分子中分离出来的假设。由于β-葡聚糖和GPL连接的受体共享一个共同的CR3结合部位，GPL连接的受体与CR3的分离将同时增加可用于β-葡聚糖结合的CR3分子的数量，并削弱对GPL连接受体的特异性配体的反应。拟议的研究将进一步阐明β-葡聚糖启动中性粒细胞作为系统性真菌感染的组成部分和具有治疗多菌败血症治疗潜力的生物反应调节剂的作用机制。

DESCRIPTION (provided by applicant): Polymorphonuclear leukocytes (PMN) are an inherently motile cell type, which can be directed to move up a chemoattractant gradient. Chemotactic movement is essential for PMN accumulation at sites of tissue injury or infection, however, mechanisms which provide the navigational signals needed to give direction to these cells are incompletely understood. Candida albicans is the fourth leading cause of nosocomial infections with post-surgical, trauma and immunosuppressed patients being at highest risk. Beta-glucan, a major component of the yeast cell wall, is elaborated into the bloodstream of patients with systemic candidiasis although the role of beta-glucan in the pathobiology of the disease is not clear. Recent findings from this laboratory have shown beta-glucan, converts PMN migration from random to direct. The conversion is mediated by recognition of beta-glucan by the leukocyte beta2integrin CR3 (CD11 b/CD18) and is a previously unrecognized effect of beta-glucan on neutrophil function. The long-term goal of our work is to understand how host defenses are affected by beta-glucan during the course of systemic fungal infections. The focus of the current proposal is to determine the mechanisms through which beta-glucan recognition by CR3 alters neutrophil function. Experiments in Aim I will investigate the role of several intracellular signaling pathways that, based on our current findings, are hypothesized to mediate the increased chemotactic capacity of neutrophils migrating on beta-glucan supplemented matrix. Specific Aim II will apply a well-characterized wound model to demonstrate the effect of beta-glucan on the ability of the host neutrophils to respond to injury. In vitro findings have determined that activation of CR3 by beta-glucan regulates the function of integrins of the beta1 family. The wound model will determine whether beta-glucan and/or systemic candidiasis similarly alters the function of beta1 integrins in mediating PMN entry into a site of injury. Finally, several proinflammatory mediators (LPS, immune complexes, urokinase plasminogen activator) bind to glycosylphosphatidylinositol (GPI)-Iinked receptors (CD14, CD16, CD87), which in turn rely on CR3 for intracellular signaling. Specific Aim III will test the hypothesis that a novel pathway of beta1 integrin crosstalk dissociates GPl-linked receptors from CR3 molecules. Since beta-glucan and GPl-linked receptors share a common CR3 binding site, dissociation of GPl-linked receptor from CR3 would simultaneously increase the number of CR3 molecules available for beta-glucan binding and blunt the response to ligands specific for GPl-linked receptors. The proposed studies will further elucidate the mechanism of action through which beta-glucan primes neutrophils both as a component of systemic fungal infections and as a biological response modifier with therapeutic potential for treating polymicrobial sepsis.