Nitric Oxide Donor Compounds for the Treatment of Hemolytic Conditions

说明(申请人提供)：一氧化氮(NO)是一种内皮衍生的松弛因子；它在血管周围的内皮细胞中合成，并发出信号来放松平滑的肌肉和增加血液流量。血红蛋白(Hb)以几乎扩散受限的速度主动清除NO。在正常生理学中，由于血液中红细胞的区域化，Hb对NO的清除作用会减少。几种疾病包括溶血性贫血，如镰状细胞病和阵发性睡眠性血红蛋白尿(PNH)，中间地中海贫血，疟疾，血栓性血小板减少性紫癜，溶血性尿毒症综合征和体外循环，导致Hb释放到血浆中，有效地清除NO。这增加了NO清除导致的一系列并发症，导致发病率和死亡率。通过吸入给予NO已被证明可以恢复正常的NO反应性，并显示出作为溶血性疾病的治疗方法的前景。然而，吸入NO作为慢性治疗的一种手段是不现实的。该项目的目标是测试(并在一定程度上合成)最终可以静脉或口服治疗溶血性疾病的化合物。与许多治疗化合物不同，这里提出的化合物是不透细胞的，作用于血浆腔，以便优先与无细胞的Hb反应，从而灭活其清除NO的能力。要研究的先导化合物包括NONOates(无供体)、氮氧基供体以及可能的硝化脂和亚硝酸盐。人们提出了多种生物物理方法来测试所合成化合物的潜在功效，包括吸收光谱、电子顺磁共振光谱和激光衍射变形能力分析。理想的化合物应该优先与无细胞(而不是红血球包裹)的Hb在允许其在血浆寿命内发挥作用的时间范围内反应。

DESCRIPTION (provided by applicant): Nitric oxide (NO) is an endothelial derived relaxation factor; it is synthesized in the endothelium surrounding blood vessels and signals to relax smooth muscles and increase blood flow. Hemoglobin (Hb) actively scavenges NO at nearly diffusion-limited rates. In normal physiology, NO scavenging by Hb is reduced due to compartmentalization in red blood cells in the blood. Several diseased conditions including hemolytic anemias such as sickle cell disease and paroxysmal nocturnal hemoglobinuria (PNH), thalassemia intermedia, malaria, thrombotic thrombocytopenic purpura, hemolytic uremic syndrome and cardiopulmonary bypass result in release of Hb into the plasma compartment which efficiently scavenges NO. This increased NO scavenging leads to a host of complications contributing to morbidity and mortality. Administration of NO through inhalation has been shown to restore normal NO responsiveness and shows promise as a treatment for hemolytic conditions. However, NO inhalation is not practical as a means of chronic treatment. The goal of this project is to test (and to some extent synthesize) compounds that can eventually be taken intravenously or orally to treat hemolytic conditions. Unlike many therapeutic compounds, the ones proposed here would be cell-impermeable, acting in the plasma compartment so as to react preferentially with cell-free Hb and thereby inactivate its NO scavenging ability. Lead compounds to be studied include NONOates (NO donors), nitroxyl donors and possibly nitrated lipids and nitrites. A variety of biophysical methods are proposed to test the potential efficacy of the synthesized compounds including absorption and electron paramagnetic resonance spectroscopy and laser diffraction deformability assays. An ideal compound would react preferentially with cell-free (as opposed to red blood cell encapsulated) Hb in a time frame that would allow it to act within its plasma lifetime.