Effects of Nitric Oxide in Sickle Cell Blood

描述（由申请人提供）：镰状细胞病是由一种突变形式的血红蛋白引起的，当暴露于低氧张力时聚合。聚合使红细胞变得坚硬，因此它们不能穿过一些血管，导致这些血管堵塞，从而导致严重的发病率和死亡率。一氧化氮（NO）由于其血管扩张剂的作用，目前正被测试作为镰状细胞病的治疗方法。NO在血管内皮细胞中合成，并扩散到邻近的平滑肌细胞，作为信号分子，引起肌肉松弛和血管舒张。镰状红细胞也很脆弱，在循环过程中会破裂。多年来，镰状细胞病的溶血性贫血方面并未被视为在该疾病的病理生理学中起主要作用。然而，一些研究小组现在已经开始重新研究溶血的后果，并假设释放的无细胞血红蛋白有效地清除NO，导致与镰状细胞病相关的NO缺乏。本项目旨在阐明镰状细胞病中溶血的机制——血红蛋白突变如何导致红细胞脆弱性增加？此外，将深入探讨红细胞包裹血红蛋白（与无细胞血红蛋白相比）清除NO的机制。将确定NO在镰状细胞血液和志愿者非患者血液中的反应差异。最后，我们将探讨使用阴离子亚硝酸盐恢复患者有效NO反应的机制的基本科学方面。参与该项目的实验室最近表明，与现有的范例相反，亚硝酸盐在人体循环中起血管扩张剂的作用。此外，研究表明亚硝酸盐的这种作用可能是由于血红蛋白的一种新的变构控制功能。该研究采用了大量的生物物理技术，包括电子顺磁共振光谱、动力学吸收光谱、激光衍射和计算模拟。已经开发了一些技术，可以对全血进行研究，从而可以评估与生理有关的情况。

DESCRIPTION (provided by applicant): Sickle cell disease is caused by a mutant form of hemoglobin that polymerizes when exposed to low oxygen tension. Polymerization makes the red blood cells rigid so that they cannot traverse some blood vessels leading to blockage of these vessels which then leads to significant morbidity and mortality. Nitric Oxide (NO) is currently being tested as a treatment for sickle cell disease due to (among other things) its role as a vasodilator. NO is synthesized in endothelial cells of blood vessels and diffuses to neighboring smooth muscle cells where it acts as a signaling molecule, causing muscle relaxation and vasodilation. Sickle red blood cells are also fragile, rupturing during transit in the circulation. For many years, this hemolytic anemia aspect of sickle cell disease was not viewed as a playing a major role in the pathophysiology of the disease. However, several groups have now begun to re-examine the consequences of hemolysis and the hypothesis that cell-free hemoglobin that is released efficiently scavenges NO, leading to an NO-related deficiency associated with sickle cell disease. This project aims to elucidate the mechanism of hemolysis in sickle cell disease - how does the hemoglobin mutation lead to increased red blood cell fragility? In addition, the mechanism of reduced NO scavenging by red cell encapsulated hemoglobin (compared to cell-free hemoglobin) will be thoroughly explored. Differences in how NO reacts in sickle cell blood and that from volunteer non-patients will be determined. Finally, we will explore basic scientific aspects of a mechanism of restoring effective NO response in patients using the anion nitrite. The laboratories participating in this project have recently shown that, contrary to the existing paradigm, nitrite acts as a vasodilator in human circulation. In addition, it was shown that this action of nitrite may be due to a novel allosterically-controlled function of hemoglobin. The study employs a vast array of biophysical techniques including electron paramagnetic resonance spectroscopy, kinetic absorption spectroscopy, laser diffraction, and computational simulations. Techniques have been developed so that studies can be made on whole blood, so that physiologically relevant conditions can be assessed.