RBC age and potentiation of transfusion related pathology in trauma patients

描述(由申请人提供)： 建议使用RBC，特别是较老的RBC单位，以增强接受输血的患者的毒性。与这一概念一致，我们机构的数据显示，老化(2周储存)的去白细胞红细胞在促进创伤患者的组织损伤和死亡率方面具有不利影响。这种所谓的“RBC损伤”现象背后的机制尚不清楚。提出的两种机制包括：1)红细胞通过血红蛋白感知氧气和刺激血管系统中的一氧化氮(NO)信号的机制的功能障碍。在此背景下，提出了S的3种作用机制：亚硝酸血红蛋白、亚硝酸盐还原和三磷酸腺苷。2)刺激免疫细胞，继而加重炎症组织损伤。在这项建议中，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估与基于机制的研究相结合来测试这两种机制的重要性，以确定在这些情况下衰老如何对红细胞功能产生负面影响。我们假设，衰老的红细胞通过亚硝酸盐还原酶和ATP途径的缺陷而将氧气感知与NO生物活性连接起来的能力耗尽，而刺激受体炎症的能力增强。这一假说将通过以下目标来验证：1)确定单个去白细胞红细胞对复苏创伤患者微循环血流动力学和炎症的影响，2)确定储存红细胞在控制缺氧NO信号的3种机制中的作用，以及3)确定储存红细胞对先天性免疫激活和炎症的影响。我们将以配对的方式评估不同年龄的红细胞在体内和体外介导血管NO信号和调节免疫细胞功能的机制。建议的研究将对ICU中稳定的创伤患者采用标准的护理方法，只有在临床指示下才会进行输血。我们将把测量限制在给药前和给血后，因此对一个年龄和血型的测量(从而避免了与给药包括不同年龄的多个单位血液相关的潜在混杂变量)。此外，我们将把这项研究限制在早晨接受血液的患者，以便评估机制(目标2和目标3)。预计拟议研究的完成将为体内和体外评估的储存的红细胞损伤的性质提供关键的机械学见解。 公共卫生相关性： 相关声明在这项建议中，我们的目的是阐明如何使用压缩红细胞(RBC)，特别是较老的储存红细胞，可能会对需要输血的患者造成毒性。我们将集中讨论两个具体领域：1)红细胞如何通过调节血管扩张剂一氧化氮来控制血液流动；2)红细胞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，阐明这些机制将提高我们对红细胞在输血中的功能的理解，并允许设计治疗方法来限制任何毒性作用。

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.