Nitric oxide protects against microcirculatory complications of malaria

一氧化氮可预防疟疾的微循环并发症

• 批准号: 7393113
• 负责人: Leonardo Jose de Moura Carvalho
• 金额: $ 42.62万
• 依托单位: LA JOLLA BIOENGINEERING INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7393113
• 关键词: Address; Adhesions; Animals; Apoptosis; Arginine; Arts; Atherosclerosis; Biological Assay; Biological Availability; Blood; Blood - brain barrier anatomy; Blood Platelets; Blood Pressure; Blood Substitutes; Blood Vessels; Blood capillaries; Blood flow; Brain; Cell Adhesion; Cell Adhesion Molecules; Cells; Cerebral Malaria; Cessation of life; Child; Complex; Cyclic GMP; Daily; Data; Development; Disease; Disruption; Doctor of Philosophy; Dyes; E-Selectin; Electrodes; Endothelial Cells; Erythrocytes; Evans blue stain; Exhibits; Extravasation; Functional disorder; Generations; Hemoglobin; Hemorrhage; Hypotension; Hypoxia; ICAM1 gene; Impaired cognition; Infection; Inflammation; Lactic Acidosis; Lead; Leukocytes; Localized; Location; Malaria; Malignant Neoplasms; Measurement; Measures; Mediating; Microcirculation; Microvascular Permeability; Molecular; Mus; NBL1 gene; Necrosis; Nitric Oxide; Nitric Oxide Donors; Numbers; Organ failure; Oxygen; Parasite Control; Parasitemia; Parasites; Pathogenesis; Patients; Perfusion; Permeability; Plasmodium berghei; Production; Proteins; Radiolabeled; Reperfusion Injury; Research; Research Personnel; Role; Saline; Sepsis; Shock; Sickle Cell Anemia; Signal Transduction; Stroke; Superoxides; Techniques; Tissues; Toxic effect; Vascular Endothelial Growth Factors; Vascular Permeabilities; Venous; arteriole; base; brain tissue; capillary; day; density; in vivo; insight; intravital microscopy; killings; light microscopy; omega-N-Methylarginine; prevent; programs; radiotracer; response; tissue oxygenation; vasoconstriction; venule

DESCRIPTION (provided by applicant): 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 leak, 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 interrelate 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).

描述（由申请人提供）：我们提出低一氧化氮（NO）生物利用度介导严重疟疾的微循环并发症；寄生虫复制不可避免地会释放无细胞血红蛋白 (Hb)，导致 NO 猝灭，而低精氨酸血症导致 NO 产生量低，导致 NO 生物利用度低。血管渗漏、点状出血和低血压是实验性脑型疟疾 (ECM) 公认的并发症，拟议的研究将确定组织氧合不良是否也通过改变血流量或功能性毛细血管密度而在疟疾发病机制中发挥作用。我们观察到 (i) 游离血红蛋白 (Hb) 在 ECM 期间显着升高，(ii) 游离 Hb 清除一氧化氮 (NO)，以及 (iii) ECM 期间发生明显的低精氨酸血症，这表明，与败血症相反，疟疾休克是由低 NO 生物利用度引起的。微循环研究中的一个主要争议是 NO 在介导血管渗漏和发病机制中的作用，我们提出的研究将明确其在 ECM 期间血管渗漏中的作用。我们的假设的一个关键预测是外源性 NO 可以预防 ECM 发病机制；事实上，NO 供体给药可以显着 (P=0.003) 保护动物免受疾病的发展。经过显着保护的 NO 供体治疗的小鼠消除了血管渗漏、点状出血、低血压和 NO 介导的信号传导受损（cGMP 水平），这些现象在使用 ECM 注射盐水的对照组中检测到。这些研究将进一步扩展，以确定 NO 供体给药是否可以防止 ECM 期间的其他微循环功能障碍，例如低组织灌注和氧合（目标 1）。寄生红细胞 (pRBC)、血小板和白细胞在 ECM 过程中发生粘附，并且选定的细胞粘附分子的缺乏可防止疟疾发病。我们将 ECM 微循环并发症的结果与细胞粘附和 eCAM 表达联系起来，以确定细胞粘附导致血脑屏障破坏和发病机制的细胞和分子机制，并确定外源性 NO 是否以及如何防止 ECM 细胞粘附（目标 2）。最终目标将通过生物测定（小动脉扩张和小静脉渗漏）和实际测量（NO 电极）评估 NO 生物利用度是否在 ECM 过程中受损并由保护性 NO 供体恢复。 eNOS 对 ECM 和 NO 供体治疗的反应也将得到阐明；目前还缺乏对其他疾病（镰状细胞性贫血）期间发生的体内 eNOS 对游离 Hb 或低 NO 生物利用度的反应的详细了解。除了提供有关微循环的新信息外，拟议的研究还可能导致疟疾的辅助治疗，从而使数百万儿童免于死亡或认知受损。这些研究还将解决有关疟疾发病机制的长期争议，例如 pRBC 粘附是否会导致缺氧和多器官衰竭（隔离假说）。