Red Cell Tranfusion: Modifier of Lung and Systemic Inflammatory Responses

描述(由申请人提供)：输注红细胞(RBC)在重症监护病房中仍然是一种非常常见的治疗方法，但在危重患者中会导致意想不到的后果。虽然肺部是一个靶器官，但人类的肺损伤很少由任何单一事件引起，仅靠输注红细胞通常不足以导致损伤，而需要具有更高的“易感性”的宿主。我们对红细胞输注的持续兴趣 及其在改变炎症反应中的潜在作用使我们关注输注的氧化损伤红细胞(OxRBC)和携带表面磷脂酰丝氨酸(PS)的微粒在改变单核吞噬细胞激活状态中的作用，以及宿主因子在保护持续性肺炎症和损伤中的作用。我们假设存在一种内源性对抗机制，即巨噬细胞(M)吞噬输入的oxRBC或标准RBC单位中包含的PS+微粒，通过释放抗炎信号IL-10来抑制巨噬细胞的激活。这种因摄取凋亡小体而产生的失活信号是抑制炎症和促进损伤消退所必需的。通过摄入凋亡小体后IL-10信号的缺陷而导致的不适当的失活可能会增加个体对红细胞输注风险的易感性。我们发现了一种新的“易感”宿主的小鼠模型，并提出通过M？清除受体CD36参与吞噬PS+凋亡小体的多功能粘附性糖蛋白-1(TSP1)缺乏的小鼠，在内毒素诱导的肺部炎症后表现出缺陷的IL-10反应，并且在输注oxRBC后肝脏中的IL-10信号缺陷也不能解决损伤。基于我们的发现，我们提出了一个总体假设，即TSP1作为一种细胞外的桥梁分子，介导CD36依赖的IL-10的产生，有助于正确解决输血后肺部炎症所需的M？失活。当被破坏时，宿主很容易受到红细胞输注的有害影响，并通过受损的M？失活表现出持续的炎症。利用人单核细胞来源的巨噬细胞(HMDM)、小鼠巨噬细胞集落刺激因子(TSP1-/-)和CD36-/-小鼠，我们将确定(1)TSP1介导的巨噬细胞在红细胞微粒或oxRBC接触后产生的IL-10是否需要CD36；(2)输注储存的RBC通过CD36依赖的IL-10产生损害TSP1-/-小鼠由内毒素或细菌引起的肺部炎症；(3)IL-10的重建加速了TSP1-/-小鼠肺部炎症的消退，并且可以利用RBC微粒的免疫调节特性来重新编程具有完整TSP-1/CD36轴的单核巨噬细胞。这些研究的完成将确定一个非常新的途径，潜在的免疫调节方面的红细胞输注及其对肺部炎症和易感宿主损伤的贡献。

DESCRIPTION (provided by applicant): Red blood cell (RBC) transfusion remains a very common therapeutic in intensive care units, but is associated with unintended consequences in the critically ill population. While the lungs are a target organ, human lung injury is seldom caused by any single event, and RBC transfusion alone is generally not sufficient to induce injury but requires a host with increased "susceptibility". Our ongoing interest in RBC transfusion and its potential role in modifying inflammatory responses have led us to focus upon the role of transfused oxidized, damaged RBC (oxRBC) and micro-particles bearing surface phosphatidylserine (PS) in altering the mononuclear phagocyte activation status and the role of host factors that protect from persistent lung inflammation and injury. We hypothesize that an endogenous countering mechanism exists whereby macrophage (M¿) engulfment of transfused oxRBC or PS+ micro-particles contained within standard RBC units results in suppression of macrophage activation through the release of the anti-inflammatory signal IL-10. This de-activating signal resulting from the ingestion of apoptotic bodies is required to curtail inflammation and promote the resolution phase of injury. Improper deactivation, through defective IL-10 signaling following ingestion of apoptotic bodies may increase the susceptibility of an individual to the risks of RBC transfusion. We have identified a novel murine model of the "susceptible" host and propose that mice deficient in thrombospondin-1 (TSP1), a multi-functional adhesive glycoprotein involved in phagocyte recognition of PS+ apoptotic bodies through the M¿ scavenging receptor CD36, show defective IL-10 responses following LPS- induced lung inflammation and fail to resolve injury in addition to defective IL-10 signaling in th liver following transfusion of oxRBC. Based upon our findings, we propose an overall hypothesis that TSP1 functions as an extracellular, bridging molecule that mediates CD36-dependent IL-10 production, contributing to M¿ deactivation necessary for proper resolution of lung inflammation following transfusion. When disrupted, the host is left vulnerable to the harmful effects of RBC transfusion and shows persistence of inflammation through impaired M¿ deactivation. Utilizing human monocyte derived M¿ (HMDM), murine M¿, tsp1-/-, and cd36-/- mice, we will determine whether (1) TSP1-mediated IL-10 production by M¿ following engagement of RBC micro-particles or oxRBC requires CD36; (2) transfusion of stored RBC impairs resolution of lung inflammation induced by either LPS or bacterial pathogen in tsp1-/- mice through CD36-dependent IL-10 production; and (3) reconstitution of IL-10 hastens resolution of lung inflammation in tsp1-/- mice and that immune-modulatory properties of RBC micro-particles can be harnessed to reprogram mononuclear phagocytes with intact TSP- 1/CD36 axis toward resolution. Completion of these studies will identify a highly novel pathway underlying the immune-modulatory aspect of RBC transfusion and its contribution to lung inflammation and injury in the susceptible host.