Nitric oxide protects against microcirculatory complications of malaria

我们认为，低的一氧化氮（NO）生物利用度介导的微循环并发症， 严重疟疾; NO淬灭的无细胞血红蛋白（Hb）释放作为一个不可避免的后果， 寄生虫复制和由于低维生素血症导致的低NO产生导致低NO生物利用度。血管 实验性脑出血的常见并发症是： 疟疾（ECM），拟议的研究将确定组织氧合不良是否也起作用， 疟疾发病机制通过改变血流或功能性毛细血管密度。我们的观察是（i）自由 血红蛋白（Hb）在ECM期间显著升高，（ii）游离Hb清除一氧化氮（NO），和（iii）显著升高 在ECM期间发生低维生素血症表明，与脓毒症相反，疟疾休克是由低NO引起 生物利用度微循环研究中的一个主要争议是NO在介导血管渗漏中的作用 和发病机制，我们提出的研究将确定其在ECM过程中的血管渗漏中的作用。 我们的假设的一个关键预测是，外源性NO应该保护免受ECM发病机制; 事实上，NO供体给药显著（P=0.003）保护动物免于疾病的发展。 明显受保护的NO供体处理的小鼠消除了血管渗漏，点状出血， 低血压，和受损的NO介导的信号传导（cGMP水平），检测到在盐水注射 ECM控制。这些研究将扩展到确定NO供体管理是否保护 对抗ECM期间的其他微循环功能障碍，如低组织灌注和氧合（目的 1）。寄生红细胞（pRBC）、血小板和白细胞的粘附发生在ECM期间， 所选细胞粘附分子的缺乏可防止疟疾发病。我们将相互联系 结果微循环并发症的ECM细胞粘附和eCAM表达，以确定 细胞粘附导致血脑屏障破坏的细胞和分子机制 和发病机制，并确定外源性NO是否以及如何防止ECM细胞粘附（目的2）。 最终目的将通过生物测定（小动脉扩张和小静脉渗漏）和实际测量（否）进行评估 电极）是否在ECM期间NO生物利用度受损并由保护性NO供体恢复。的 eNOS对ECM和NO供体治疗的反应也将得到阐明; 体内eNOS对游离Hb或在其他疾病（镰状细胞病）期间发生的低NO生物利用度的反应 目前缺乏。除了提供有关微循环的新信息外， 研究可能会导致疟疾的辅助治疗，挽救数百万儿童的死亡或损害 认知.这些研究还将解决长期存在的关于疟疾发病机制的争议，如 pRBC粘附是否导致缺氧和多器官衰竭（隔离假说）。

We propose that low nitric oxide (NO) bioavailability mediates the microcirculatory complications of severe malaria; NO quenching by cell-free hemoglobin (Hb) released as an unavoidable consequence of parasite replication and low NO production due to hypoargininemia lead to low NO bioavailability. Vascular eak, petechial hemorrhaging, and hypotension are well recognized complications of experimental cerebral malaria (ECM), and the proposed studies will determine whether poor tissue oxygenation also functions in malaria pathogenesis by altering blood flow or functional capillary density. Our observations that (i) free hemoglobin (Hb) is markedly elevated during ECM, (ii) free Hb scavenges nitric oxide (NO) and (iii)marked hypoargininemia occurs during ECM indicate that, in contrast to sepsis, malaria shock is caused by low NO bioavailability. A major controversy in microcirculation research is the role of NO in mediating vascular leak and pathogenesis, and our proposed studies will define its role in vascular leak during ECM. A key prediction of our hypothesis is that exogenous NO should protect against ECM pathogenesis; indeed, NO donor administration significantly (P=0.003) protects animals from the development of disease. The markedly protected NO donor-treated mice abrogated the vascular leak, petechial hemorrhage, hypotension, and impaired NO mediated signaling (cGMP levels) that were detected in saline-injected controls with ECM. These studies will be extended to define whether NO donor administration protects against other microcirculatory dysfunction during ECM, such as low tissue perfusion and oxygenation (aim 1). Adhesion of parasitized erythrocytes (pRBCs), platelets, and leukocytes occur during ECM and deficiency of selected cell adhesion molecules protects against malaria pathogenesis. We will inter relate the results of the microcirculatory complications of ECM to cell adhesion and eCAM expression to define the cellular and molecular mechanisms whereby cell adhesion contributes to disruption of the blood brain barrier and pathogenesis and identify whether and how exogenous NO protects against ECM cell adhesion (aim 2). The final aim will assess by bioassay (arteriolar dilation, and venular leak) and actual measurement (NO electrode) whether NO bioavailability is impaired during ECM and restored by the protective NO donor. The response of eNOS to ECM and NO donor treatment will also be elucidated; a detailed understanding of in vivo eNOS responses to free Hb or to low NO bioavailability that occurs during other diseases (sickle cell anemia) is currently lacking. Besides providing new information about the microcirculation, the proposed studies may lead to adjunct therapy for malaria that rescues millions of children from death or impaired cognition. These studies will also address long standing controversies about malaria pathogenesis, such as whether pRBC adhesion leads to hypoxia and multi-organ failure (sequestration hypothesis).