von Willebrand factor and thrombocytopenia in infective endocarditis

感染性心内膜炎中的冯维勒布兰德因子和血小板减少症

• 批准号: 10472517
• 负责人: Emily Rose Legan
• 金额: $ 3.08万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10472517
• 关键词: Address; Adherence; Adhesions; Adopted; Affect; Animal Model; Animals; Antibiotic Therapy; Bacteria; Bacterial Infections; Bacterial Proteins; Basic Science; Binding; Binding Proteins; Biological; Biomechanics; Blood; Blood Circulation; Blood Coagulation Disorders; Blood Platelets; Blood flow; Cardiac Surgery procedures; Clinical Data; Coagulation Process; Collagen; Complex; Deuterium; Development; Diagnosis; Diagnostic; Disease; Endothelium; Enzyme-Linked Immunosorbent Assay; Event; Exhibits; Flow Cytometry; Future; Glycoproteins; Goals; Gram-Positive Bacteria; Heart; Heart Valves; Hemorrhage; Hemostatic Agents; Hemostatic function; Hydrogen; Infection; Infective endocarditis; Lead; Ligand Binding; Ligand Binding Domain; Mass Spectrum Analysis; Measures; Mediating; Mediator of activation protein; Membrane; Molecular; Mus; Operative Surgical Procedures; Outcome Study; Pathogenesis; Patients; Plasma Proteins; Platelet Activation; Platelet Count measurement; Prevalence; Prognosis; Proteins; Recombinants; Regulation; Research; Role; Severities; Signal Transduction; Staphylococcal Protein A; Staphylococcus aureus; Structure; Surface; Surface Plasmon Resonance; Therapeutic; Thrombocytopenia; Thrombosis; Time; Tissues; Work; analytical ultracentrifugation; chronic infection; glycoprotein receptor GPIb-IX; heart damage; ineffective therapies; molecular pathology; monomer; mortality; new therapeutic target; receptor; stoichiometry; therapeutic development; thrombotic; valve replacement; vascular injury; von Willebrand Factor

PROJECT SUMMARY Infective endocarditis (IE) is a serious and often deadly disease in which bacteria colonize the heart valves and cause severe damage. The exact prevalence of the illness has been difficult to define due to diagnostic challenges; however, of the thousands of cases diagnosed annually around the world, as many as 40% of them are fatal. The high mortality rate of IE is due mostly to ineffective treatment options, which are currently limited to aggressive antibiotic treatments and cardiac surgeries. IE caused by the Gram-positive bacteria Staphylococcus aureus has been the deadliest and most common form of IE for over a decade. Recent clinical data demonstrate a correlation between platelet levels in circulation and severity of IE, as patients who develop thrombocytopenia, or low platelet levels, have lower chances of survival compared to patients with normal platelet levels. Additionally, S. aureus expresses two proteins, von Willebrand factor binding protein (VWbp) and staphylococcal protein A (SPA), that bind von Willebrand factor (VWF), a large plasma protein that mediates platelet adherence to the endothelium and facilitates platelet clearance from the bloodstream. Animal models in which VWF is absent exhibit reduced bacterial colonization in both the heart and endothelial tissue. Clinical data and basic research have therefore implicated VWF as a critical mediator in the early development and later progression of IE, yet the molecular mechanism underlying this role of VWF is unknown. Recently, our lab identified the autoinhibitory module (AIM) in VWF that limits its association to platelets. Our lab has also elucidated the molecular mechanisms of platelet activation and clearance when VWF binds and stimulates platelet receptor GPIba under shear flow. Aberrant binding of VWF to GPIba can lead to enhanced platelet activation and cause thrombosis or increased platelet clearance which leads to thrombocytopenia. We hypothesize that S. aureus proteins SPA and VWbp facilitate early bacterial colonization and later thrombocytopenic conditions by activating VWF to enhance platelet binding and yield platelet activation and clearance. In Specific Aim 1, we will determine how SPA and VWbp affect VWF autoinhibition by assessing changes in binding and AIM dynamics. In Specific Aim 2, we will investigate how these S. aureus proteins modulate VWF-mediated platelet activation by assessing binding of VWF and GPIba in the presence of these proteins, measuring hallmarks of platelet clearance signals via flow cytometry, and determining the ability of these proteins to facilitate platelet clearance in mice. My proposed studies will elucidate a molecular mechanism underlying S. aureus pathogenesis and IE development to facilitate potential therapeutic strategies as well as contribute to our fundamental understanding of hemostatic and thrombotic regulation during bacterial infection.

项目摘要 感染性心内膜炎（IE）是一种严重且通常是致命的疾病，细菌在心脏瓣膜和心脏瓣膜上定居 造成严重损坏。由于诊断性，难以定义疾病的确切患病率 挑战；但是，在全球每年被诊断出的数千例病例中，其中多达40％ 致命。 IE的高死亡率高于目前有限的治疗方法，主要是由于无效的治疗方法 进行侵略性抗生素治疗和心脏手术。 IE是由革兰氏阳性细菌引起的 十多年来，金黄色葡萄球菌一直是IE的最致命，最常见的IE形式。最近的临床 数据表明，随着发育的患者的流通和严重程度的血小板水平之间的相关性 与正常患者相比 血小板水平。此外，金黄色葡萄球菌表达了两种蛋白质，即von Willebrand因子结合蛋白（VWBP）和 结合Von Willebrand因子（VWF）的葡萄球菌蛋白A（SPA），这是一种介导的大血浆蛋白 血小板依从于内皮，并促进血液中血小板清除。动物模型 在心脏和内皮组织中，哪些VWF均显示出降低的细菌定殖。临床数据 因此，基础研究已将VWF牵涉到早期发展和后期的关键调解人 IE的进展，但是VWF的这种作用的分子机制尚不清楚。最近，我们的实验室 在VWF中确定了自身抑制模块（AIM），该模块限制了其与血小板的关联。我们的实验室也有 当VWF结合并刺激时，阐明了血小板激活和清除的分子机制 剪切流下的血小板受体GPIBA。 VWF与GPIBA的异常结合会导致血小板增强 激活并导致血栓形成或血小板清除率增加，从而导致血小板减少症。我们 假设金黄色葡萄球菌蛋白水疗中心和VWBP促进了早期细菌定殖，然后 通过激活VWF来增强血小板结合并产生血小板激活，并产生血小板激活和 清除。在特定的目标1中，我们将通过评估来确定水疗中心和VWBP如何影响VWF自动抑制作用 绑定和目标动态的变化。在特定目标2中，我们将研究这些金黄色葡萄球菌蛋白如何 通过评估VWF和GPIBA的结合，调节VWF介导的血小板激活 蛋白质，通过流式细胞仪测量血小板清除信号的标志，并确定 这些蛋白质可促进小鼠血小板清除率。我提出的研究将阐明分子机制 金黄色葡萄球菌的发病机理和IE发育，以促进潜在的治疗策略以及 有助于我们对细菌感染期间止血和血栓性调节的基本理解。