Effect of Nitric Oxide on End Organ Injury in a Canine M

在人类疾病的血管内溶血过程中，无细胞血浆血红蛋白与一氧化氮(NO)的反应性增加可能会损害血管运动张力和器官灌注量。我们在犬的实验模型中制造了急性血管内溶血，以验证低水平分解的或无细胞的血浆血红蛋白将严重降低NO的生物利用度并产生血管运动不稳定性的假设。重要的是，在这个模型中，总的血管内血红蛋白水平没有变化，只有红细胞膜内的血红蛋白的区隔被破坏。使用完全析因设计，我们证明了游离水诱导的血管内溶血产生剂量依赖性的全身血管收缩并损害肾功能。我们发现，这些生理变化是内源性NO被游离血浆氧合血红蛋白化学计量氧化所次要的。在这个模型中，吸入的80ppm的NO气体将85-90%的血浆氧合血红蛋白氧化成高铁血红蛋白，从而抑制了无细胞血红蛋白对内源性NO的清除。结果，急性溶血引起的血管收缩减弱，对系统输注NO供体的反应性恢复。这些观察证实，血管内溶血的急性毒性继发于血浆氧合血红蛋白与内皮来源的NO加速的双氧合反应，形成生物活性的硝酸盐。这些生化和生理学研究证实了完整红细胞在NO内稳态中的重要作用，并为人类存在溶血相关的一氧化氮失调综合征提供了机制支持，该综合征可能导致遗传性、获得性和医源性溶血状态的血管病变。 这项研究目前正在《临床调查》杂志上发表，这是一系列研究亚硝酸盐在治疗溶血性疾病中作用的第一项研究。

During intravascular hemolysis in human disease, vasomotor tone and organ perfusion may be impaired by the increased reactivity of cell-free plasma hemoglobin with nitric oxide (NO). We experimentally produced acute intravascular hemolysis in a canine model in order to test the hypothesis that low levels of decompartmentalized or cell-free plasma hemoglobin will severely reduce NO bioavailability and produce vasomotor instability. Importantly, in this model the total intravascular hemoglobin level is unchanged, only the compartmentalization of hemoglobin within the erythrocyte membrane is disrupted. Using a full factorial design, we demonstrate that free water-induced intravascular hemolysis produces dose dependent systemic vasoconstriction and impairs renal function. We find that these physiologic changes are secondary to the stoichiometric oxidation of endogenous NO by cell free plasma oxyhemoglobin. In this model, 80 ppm of inhaled NO gas oxidized 85-90% of plasma oxyhemoglobin to methemoglobin, thereby inhibiting endogenous NO scavenging by cell-free hemoglobin. As a result, the vasoconstriction caused by acute hemolysis was attenuated and the responsiveness to systemically infused NO donors was restored. These observations confirm that the acute toxicity of intravascular hemolysis occurs secondary to the accelerated dioxygenation reaction of plasma oxyhemoglobin with endothelium-derived NO to form bioinactive nitrate. These biochemical and physiological studies demonstrate a major role for the intact erythrocyte in NO homeostasis and provide mechanistic support for the existence of a human syndrome of hemolysis-associated nitric oxide dysregulation, which may contribute to the vasculopathy of hereditary, acquired and iatrogenic hemolytic states. This study which is presently in press in the Journal of Clinical Investigation is the first of a series of studies investigating the role of Nitrites in the treatment of hemolytic diseases.