Erythrocyte Nitric Oxide Links Rheology and Vasculopathy in Sickle Cell Disease

描述(申请人提供)：镰状细胞病是一种进行性血管病变，源于红细胞变形性降低。血管疾病是急性和慢性镰状疾病的核心，包括疼痛危象、急性胸部综合征、中风、皮肤溃疡和肺动脉高压。然而，将红细胞变形性降低与慢性血管病变联系起来的机制是多因素的，而且缺乏特征性。一氧化氮(NO)是连接血液力学与血管紧张性和血管重塑的关键介质。当血流剪切血管内皮细胞时，一氧化氮被释放，导致血管扩张，抑制血小板聚集。在SCD中，NO的生物利用度降低，因为溶血过程中释放的脱细胞血红蛋白和精氨酸酶清除NO，并降低内皮NO的生成。最近的证据表明，50%的生物可利用的NO是通过剪切激活的eNOS酶在红细胞内合成的。当组织含氧量较高时，RBC NO主要转化为亚硝酸盐和亚硝化血红蛋白，但脱氧血红蛋白在低氧传导下将这些物种转化为一氧化氮。因此，RBC产生的NO似乎是氧供需的重要中介，其在镰状细胞血管病变中的作用完全未被探讨。我们的基本假设是，红细胞变形性降低会减少红细胞本身产生的剪切力介导的一氧化氮，削弱维他命“储存”形式的一氧化氮，导致血管系统多个层面的血管功能障碍。这项研究建议将RBC一氧化氮产生的新实验室方法与镰状细胞病患者血管功能障碍的临床研究相结合。不同血管床的多模式特征将导致改进的表型分类和与潜在的RBC生物物理/生化紊乱的病理生理联系。我们还将探讨RBC产生的NO是否有能力通过主动脉环准备直接影响血管系统，以及RBC产生的NO是否会降低血小板聚集。这笔赠款的支持从三个方面使SCD患者受益：1)它改善了跨专科(即血液学和心脏病学)；2)它将基于实验室的新方法转化为使用血管准备和血小板聚集测量的患者RBC产生NO；3)它将为更大规模的临床翻译研究奠定基础，将RBC产生的NO和流变学与SCD患者血管功能的复杂测量联系起来。K23机制代表了我迄今为止职业发展的自然延伸，将我以前的实验室和以患者为导向的研究专业知识与对血管功能障碍的新靶点进行大型转化性研究所必需的特定临床研究培训结合在一起。

DESCRIPTION (provided by applicant): Sickle cell disease is a progressive vasculopathy stemming from decreased red blood cell (RBC) deformability. Vascular disease is at the heart of both acute and chronic sickle disease, including pain crisis, acute chest syndrome, stroke, skin ulcers, and pulmonary hypertension. However, the mechanisms linking decreased RBC deformability to chronic vasculopathy are multifactorial and poorly characterized. Nitric oxide (NO) is the key mediator linking blood mechanics to vessel tone and vascular remodeling. As bloodflow shears the endothelium, NO is released, causing vasodilation and inhibiting platelet aggregation. NO bioavailability is diminished in SCD because decellularized hemoglobin and arginase, released during hemolysis, scavenge NO and lower endothelial NO production. Recent evidence suggests that 50% of bioavailable NO is synthesized within RBC, themselves, though a shear-activated eNOS enzyme. RBC NO is primarily converted to nitrite and nitrosylated hemoglobins when tissue oxygenation is high, but deoxygenated hemoglobin converts these species to nitric oxide under hypoxic conductions. Thus, RBC generated NO appears to be a vital mediator of oxygen supply and demand and its role in sickle cell vasculopathy is completely unexplored. Our fundamental hypothesis is that decreased red cell deformability reduces shear-mediated nitric oxide production by the red cell itself, crippling vita "storage" forms of nitric oxide, causing vascular dysfunction at several levels of the vascular system. This research proposal merges novel laboratory methods in RBC nitric oxide production with clinical investigation of vascular dysfunction in patients with sickle cell disease Multimodal characterization of the different vascular beds will lead to improved phenotypic categorization and pathophysiological links to the underlying RBC biophysical/biochemical derangements. We will also explore whether RBC-generated NO has the ability to directly affect the vasculature using aortic ring preps and whether RBC-generated NO decreases platelet aggregation. Support from this grant benefits SCD patients in three ways: 1) it improves cross- specialization (i.e. hematology and cardiology), 2) it translates novel lab based methods in RBC generation of NO to patients using vascular preps and measurement of platelet aggregation, and 3) it will set the ground work for larger clinical translational studies linking RBC-generated NO and rheology with sophisticated measures of vascular function in patients with SCD. The K23 mechanism represents the natural extension my career development to date, combining my previous laboratory and patient-oriented research expertise with the specific clinical research training necessary to conduct large translational studies of novel targets in vascular dysfunction.