RBC age and potentiation of transfusion related pathology in trauma patients

描述（由申请人提供）： 建议给予RBC，特别是较旧的RBC单位，以增强接受输血的患者的毒性。与这一概念一致，来自我们机构的数据显示老化（> 2周储存）白细胞耗尽的RBC在促进创伤患者的组织损伤和死亡率方面的不利影响。这种所谓的“RBC病变”现象的机制尚不清楚。两种提出的机制包括i）RBC将血红蛋白的氧感测与血管系统中一氧化氮（NO）信号传导的刺激偶联的机制中的功能障碍。在这方面，已经提出了3种机制，S-亚硝基血红蛋白，亚硝酸盐还原和ATP。ii）免疫细胞的刺激和随后炎性组织损伤的加重。在这项提案中，我们建议通过将微血管血流动力学和免疫细胞功能的临床评价与基于机制的研究相结合来测试这两种机制的重要性，以确定衰老如何在这些背景下对RBC功能产生负面影响。我们假设，老化的红细胞有一个耗尽的能力，耦合氧传感NO-生物活性通过亚硝酸还原酶和ATP途径的缺陷，并增加能力，刺激受体的炎症。该假设将通过追求以下目标来测试：1）确定单个单位的白细胞耗尽的RBC对复苏的创伤患者中的微循环血流动力学和炎症的影响，2）确定库存RBC对控制缺氧NO信号传导的3种提出的机制的作用，和3）确定库存RBC对先天免疫活化和炎症的影响。我们将评估不同年龄的红细胞介导血管NO信号传导和调节免疫细胞功能的机制，在体内和体外配对的方式。拟议的研究将采用ICU中稳定创伤患者的标准护理方法，仅在临床指征时输血。我们将测量限制在1个单位血液给药前后，因此限制在一个年龄和血型（从而避免与包括不同年龄等的多个单位血液给药相关的潜在混杂变量）。此外，我们将研究限制在早晨接受血液的患者中，以评估机制（目标2和目标3）。预计完成拟定研究将为体内和离体评估的储存RBC损伤的性质提供关键的机制见解。 公共卫生相关性： 相关性声明在本提案中，我们旨在阐明输注浓缩红细胞（RBC），特别是储存时间较长的RBC如何导致需要输血的患者出现毒性。我们将重点关注两个特定领域，i）RBC如何通过调节血管扩张剂一氧化氮来控制血流，ii）RBC如何调节免疫细胞和补体功能以及随后的炎症反应。我们预计，这些机制的阐明将提高我们对输血中RBC功能的理解，并允许设计治疗方案以限制任何毒性作用。

DESCRIPTION (provided by applicant): Administration of RBC and particularly older RBC units is proposed to potentiate toxicity in patients receiving transfusions. Consistent with this concept, data from our institution show an adverse effect of aged (>2wk storage) leukocyte-depleted RBC in promoting tissue injury and mortality in trauma patients. The mechanisms underlying this so-called 'RBC-lesion' phenomenon remain unclear. Two proposed mechanisms include i) dysfunction in mechanisms by which RBC couple oxygen sensing by hemoglobin with the stimulation of nitric oxide (NO) signaling in the vasculature. In this context, 3 mechanisms have been forwarded, S-nitrosohemoglobin, nitrite-reduction and ATP. ii) stimulation of immune cells and subsequent exacerbation of inflammatory tissue injury. In this proposal we propose to test the importance of these two mechanisms by coupling clinical evaluation of microvascular hemodynamics and immune cell function with mechanism based studies to determine how ageing negatively impacts RBC function in these contexts. We hypothesize that Aged RBC have a depleted capacity to couple oxygen sensing to NO-bioactivity via defects in nitrite-reductase and ATP pathways, and an increased capacity to stimulate inflammation in the recipient. This hypothesis will be tested by pursuit of the following aims 1) Determine the effect of a single unit of leukocyte-depleted RBC on microcirculation hemodynamics and inflammation in resuscitated trauma patients, 2) Determine the role of banked RBC on the 3 proposed mechanisms of controlling hypoxic NO-signaling and 3) Determine the effects of banked RBC on innate immune activation and inflammation. We will evaluate mechanisms by which RBC of different ages mediate vascular NO-signaling and modulate immune-cell function both in vivo and in vitro in a paired fashion. The proposed studies will employ standard of care approaches with stable trauma patients in the ICU which will only be transfused if clinically indicated. We will restrict measurements to pre- and post administration of 1 unit of blood and hence one age and blood type (thereby avoiding potential confounding variables associated with administration of multiple units of blood comprising different ages etc). In addition, we will restrict the study to patients who receive blood in morning hours to allow assessment of mechanisms (aim 2 and aim 3). It is anticipated that completion of the proposed studies will provide key mechanistic insights into the nature of the stored RBC-lesion assessed both in vivo and ex-vivo. PUBLIC HEALTH RELEVANCE: Relevance Statement In this proposal we aim to elucidate how administration of packed Red blood cells (RBC) and particularly older stored RBC may contribute to toxicity in patients requiring transfusion. We will focus on two specific areas related to i) how RBC control blood flow via regulating the vasodilator nitric oxide and ii) how RBC modulate immune cell and complement function and subsequent inflammatory reactions. We anticipate that elucidation of these mechanisms will improve our understanding of RBC functions in transfusions and allow the design of therapies to limit any toxic effects.