Role of erythroid DAMP molecules in the pathogenesis of vascular injury in sepsis

描述(由申请人提供)：美国每年有超过75万人患有严重脓毒症，超过三分之一的人死亡。脓毒症是感染和宿主反应的一种表型表现，导致内皮功能障碍和血管损伤。这在很大程度上导致了多器官衰竭和死亡率的发展。脓毒症血管损伤的机制是多方面的，超越了病原体所阐述的循环因素的影响，也超出了宿主产生大量细胞因子和趋化因子的反应。血管和内皮损伤涉及天然和获得性免疫细胞、血小板、凝血因子、补体和循环血浆蛋白的复杂相互作用。这些细胞和循环分子聚集在内皮细胞上，导致细胞激活和损伤。这会导致完整的内皮和内皮动态平衡的丧失，血管渗漏和炎细胞渗入实质组织。其结果是，血流和氧气供应发生改变，组织暴露在相同的损伤因素下，导致实质细胞损伤和功能障碍，最终导致器官衰竭。导致器官衰竭的严重内皮功能障碍现在被认为是严重脓毒症的标志。脓毒症的溶血有不同程度的发生，并不是特定病原体独有的。红血球破裂会释放红系阻滞物(EDAMP)，包括血红素。这些eDAMPs可能通过氧化损伤或激活细胞信号通路而产生直接的细胞毒作用。在许多溶血性疾病中，游离血红蛋白和血红素与内皮损伤相关。在脓毒症中，游离血红蛋白与实验模型的结果相关，是严重脓毒症患者生存的预测因子。然而，eDAMPs在脓毒症诱导的内皮损伤中的作用和机制(S)仍不清楚，这是本提案的重点。线粒体已被证明是参与细胞对应激反应的关键信号细胞器。EDAMPs和血红素可以直接或通过PRRs影响线粒体信号转导。此外，作为内皮损伤重要放大因子的血小板和中性粒细胞的影响也将被考虑。这些概念将结合肺内皮细胞和急性肺损伤的发展来考虑，因为肺损伤可以说是脓毒症中器官损伤最常见的临床表现。基于我们已发表的和初步的数据，我们提出以下假设：包括血红素在内的红系湿润物质促进了脓毒症的血管细胞和内皮损伤。这一假说将通过以下特定目标来解决：特定目标1：确定红系阻滞剂在脓毒症中增强肺内皮损伤的作用和机制(S)。特异性目的2：探讨脓毒症时eDAMPS诱导内皮细胞损伤及适应的线粒体机制(S)。具体目的3：研究脓毒症时人体循环细胞线粒体的功能和动态变化，以及血浆eDAMPs水平与炎症环境、急性肺损伤和严重腹内脓毒症患者预后的关系。

DESCRIPTION (provided by applicant): Each year, over 750,000 people in the United States suffer from severe sepsis and more than a third die. Sepsis is a phenotypic manifestation of infection and the host response, resulting in endothelial dysfunction and vascular injury. This contributes significantly to the development of multiple-organ failure and mortality. The mechanisms contributing to vascular injury in sepsis are multifaceted and extend beyond the influence of circulating factors elaborated from pathogens or the host's response with production of a myriad of cytokines and chemokines. Vascular and endothelial injury involves a complex interplay of innate and adaptive immune cells, platelets, coagulation factors, complement, and circulating plasma proteins. These cells and circulating molecules converge upon the endothelium to result in cellular activation and injury. This results in loss of an intact endothelium and endothelial homeostasis, vascular leakage, and inflammatory cell infiltration into parenchymal tissue. As a consequence, perfusion and oxygen delivery is altered and tissues are exposed to the same injurious factors, leading to parenchymal cell injury and dysfunction, and ultimately organ failure. The severe endothelial dysfunction that results in organ failure is now considered a hallmark of severe sepsis. Hemolysis in sepsis occurs to varying degrees and is not unique to specific pathogens. Red blood cell breakdown releases erythroid DAMPs (eDAMPs), including heme. These eDAMPs could have direct cytotoxic effects via oxidative injury or activate cell signaling pathways. Cell free hemoglobin and heme have been correlated with endothelial injury in a number of hemolysis-associated diseases. In sepsis, cell free hemoglobin correlates with outcomes in experimental models and is a predictor of survival in humans with severe sepsis. However, the role and mechanism(s) of eDAMPs in sepsis-induced endothelial injury remains unclear and is the focus of this proposal. Mitochondria have proven to be critical signaling organelles involved in a cells response to stress. eDAMPs and heme can influence mitochondrial signaling either directly or via PRRs. Furthermore, the influence of platelets and neutrophils as important amplifiers of endothelial injury will also be considered. These concepts will be considered in the context of the pulmonary endothelium and the development of acute lung injury, as lung injury arguably represents the most common clinical manifestations of organ injury in sepsis. Based on our published and preliminary data we propose the following hypothesis: Vascular cell and endothelial injury in sepsis is promoted by erythroid DAMPs, including heme. This hypothesis will be addressed by the following specific aims: Specific Aim 1: To determine the role and mechanism(s) of erythroid DAMPs to potentiate pulmonary endothelial injury in sepsis. Specific Aim 2: To determine the mitochondrial mechanism(s) by which eDAMPS induce endothelial injury and adaptation in sepsis. Specific Aim 3: To characterize mitochondrial function and dynamics in response to sepsis in human circulating cells and correlate plasma levels of eDAMPs with the inflammatory milieu, acute lung injury and outcomes in humans with severe intra-abdominal sepsis.