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，血管紧张素和器官灌注可能因无细胞血浆血红蛋白与一氧化氮（NO）的反应性增加而受损。我们实验性地在犬模型中产生急性血管内溶血，以检验低水平的去部分化或无细胞血浆血红蛋白将严重降低NO生物利用度并产生血管不稳定性的假设。重要的是，在该模型中，总血管内血红蛋白水平不变，仅红细胞膜内血红蛋白的区室化被破坏。使用一个完整的析因设计，我们证明了自由水诱导的血管内溶血产生剂量依赖性全身血管收缩和损害肾功能。我们发现，这些生理变化是继发于内源性NO的化学计量氧化的无细胞血浆氧合血红蛋白。在该模型中，80 ppm的吸入NO气体将85-90%的血浆氧合血红蛋白氧化为高铁血红蛋白，从而抑制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，对全身输注NO供体的反应性恢复。这些观察结果证实，血管内溶血的急性毒性继发于血浆氧合血红蛋白与内皮源性NO的加速双氧合反应，以形成无生物活性的硝酸盐。这些生物化学和生理学研究表明，完整的红细胞在NO稳态中发挥着重要作用，并为溶血相关的一氧化氮失调的人类综合征的存在提供了机制支持，这可能导致遗传性、获得性和医源性溶血状态的血管病变。 这项研究目前在临床研究杂志上发表，是调查亚硝酸盐在溶血性疾病治疗中作用的一系列研究中的第一项。

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.