Modulation of erythrocyte function by complement

描述（由申请人提供）：过度补体激活与多种病理学相关，包括疟疾、镰状细胞病、自身免疫性疾病、创伤性损伤和败血症。在美国，每年仅脓毒症就造成超过210，000人死亡，相关费用估计超过167亿美元。我们目前对脓毒症的理解是，补体介导的宿主对感染的免疫反应是微循环窘迫和严重器官损伤的原因。红细胞（RBC）通过补体受体1（CR 1）捕获补体调理颗粒并将其递送至肝脏和脾脏中的巨噬细胞，在维持非炎性血管内环境中具有关键的、非冗余的作用。我们已经发现，在过度补体激活过程中，可溶性补体片段对血型糖蛋白A（GPA）的额外接合显著抑制RBC膜变形性并促进RBC ATP释放。我们的新数据挑战了RBC作为单一非炎症细胞的经典范式，揭示了在过度补体激活期间，RBC停止维持非炎症环境并积极促进促炎性血管内环境。负责将RBC转变为促炎细胞的机制尚不清楚。更好地理解红细胞的“重编程”为促炎细胞将允许开发新的，有效的治疗败血症患者。这项工作的长期目标是了解红细胞和补体在脓毒症期间对组织和器官损伤的贡献。我们的总体假设是，在过度补体激活期间，GPA与过量补体片段的接合通过关键的ATP依赖性自分泌信号传导机制将RBC重编程为促炎细胞。我们建议的总体目标是确定补体片段参与GPA促进ATP释放和抑制RBC功能的机制。这些研究的理由是，我们已经揭示了一个独特的和关键的嘌呤需要GPA介导的补体对RBC功能的有害影响，这表明RBC产生的ATP，通过自分泌和旁分泌嘌呤能机制，促进和维持炎症血管内环境。我们研究的创新之处在于，我们发现了RBC-补体相互作用的一个新方面，这可能会显著影响靶向治疗方法的疗效和设计，从而显著降低脓毒症的发病率和死亡率。我们的研究将对我们理解红细胞和嘌呤能信号作为与过度补体激活相关的病理情况下治疗的新靶点的潜力以及我们对正常和病理情况下红细胞生物学的基本理解产生重大影响。 公共卫生相关性：本提案的目的是确定补体和嘌呤能信号对红细胞（RBC）功能在脓毒症的影响。我们在体外的研究结果，补体启动的CR 1和GPA（血型糖蛋白A）信号传导的功能后果将在体内使用败血症患者的红细胞进行验证。此外，由于RBC膜变形能力降低，血液流变学的变化将使用侧流暗视野显微镜在脓毒症患者的毛细血管循环中直接可视化和直接定量。因此，该研究的结果将独特地增强对脓毒症和脓毒性休克后多器官损伤机制的理解。这些研究将通过解决新认识到的红细胞在脓毒症中的促炎作用，对目前对脓毒症相关死亡率和发病率机制的理解产生重大影响。通过揭示补体和嘌呤能依赖性机制，负责改变红细胞在脓毒症，研究可能允许开发新的，有效的和有针对性的治疗方法，将拦截补体和嘌呤能信号级联，并显着降低发病率和死亡率脓毒症。

DESCRIPTION (provided by applicant): Excessive complement activation is associated with a wide spectrum of pathologies including malaria, sickle cell disease, autoimmune diseases, trauma injury, and sepsis. In the U.S., sepsis alone is responsible for over 210,000 deaths each year, with associated costs estimated at over $16.7 billion. Our current understanding of sepsis is that complement-mediated host immune responses to infection are responsible for microcirculatory distress and severe organ damage. Red blood cells (RBCs) have critical, non- redundant roles in maintaining a non-inflammatory intravascular environment by capturing complement- opsonized particles through complement receptor 1 (CR1) and delivering them to macrophages in the liver and spleen. We have found that during excessive complement activation the additional engagement of glycophorin A (GPA) by soluble complement fragments significantly inhibits RBC membrane deformability and promotes RBC ATP release. Our new data challenge the classic paradigm of RBCs as singularly non-inflammatory cells, revealing that during excessive complement activation, RBCs cease to maintain a non-inflammatory environment and actively promote a pro-inflammatory intravascular milieu. Mechanisms responsible for changing RBCs into proinflammatory cells have not been known. A better understanding of the "reprogramming" of RBCs into proinflammatory cells will allow the development of novel, effective therapies for septic patients. The long-term objective of this work is to understand the contribution of RBCs and complement to tissue and organ damage during sepsis. Our overall hypothesis is that during excessive complement activation, engagement of GPA by excess complement fragments reprograms RBCs into pro- inflammatory cells through a critical ATP-dependent autocrine signaling mechanism. The overall objective of our proposal is to determine the mechanisms by which engagement of GPA by complement fragments promote ATP release and inhibit RBC functions. The rational for these studies is that we have revealed a unique and crucial purinergic requirement for the GPA-mediated detrimental effect of complement on RBC functions, which suggests that RBC-generated ATP, through autocrine and paracrine purinergic mechanisms, promotes and maintains an inflammatory intravascular milieu. The innovation of our studies is that we have discovered a novel facet of RBC-complement interaction that may considerably impact the efficacy and design of targeted therapeutic approaches that will significantly lower the morbidity and mortality of sepsis. Our studies will have a significant impact on our understanding of the potential of RBCs and purinergic signaling as novel targets for therapy in pathological situation associated with excessive complement activation, as well as on our basic understanding of RBC biology in normal and pathological situations. PUBLIC HEALTH RELEVANCE: The objectives of this proposal are to determine the effects of complement and purinergic signaling on red blood cell (RBC) functions during sepsis. Our in vitro findings regarding the functional consequences of complement-initiated CR1 and GPA (glycophorin A) signaling will be validated in vivo using RBCs from septic patients. In addition, changes in hemorrheology, due to decreased RBC membrane deformability, will be directly visualized and quantified directly in capillary circulation from septic patients using sidestream darkfield microscopy. Therefore, the results of the study will uniquely enhance understanding of the mechanisms responsible for multiorgan injury following sepsis and septic shock. The studies will have a significant impact on the current understanding of the mechanisms responsible for mortality and morbidity associated with sepsis by addressing the newly recognized pro-inflammatory role of RBCs in sepsis. By uncovering the complement- and purinergic-dependent mechanisms responsible for altering RBCs in sepsis, the studies may allow the development of novel, effective and targeted therapeutic approaches that will intercept the complement and purinergic signaling cascades, and significantly lower morbidity and mortality of sepsis.