BACKGROUND Severe malaria is associated with impaired nitric oxide (NO) synthase (NOS)-dependent vasodilation, and reversal of this deficit improves survival in murine models. Malaria might have selected for genetic polymorphisms that increase endothelial NO signaling and now contribute to heterogeneity in vascular function among humans. One protein potentially selected for is alpha globin, which, in mouse models, interacts with endothelial NOS (eNOS) to negatively regulate NO signaling. We sought to evaluate the impact of alpha globin gene deletions on NO signaling and unexpectedly found human arteries use not only alpha but also beta globin to regulate eNOS. METHODS The eNOS-hemoglobin complex was characterized by multiphoton imaging, gene expression analysis, and coimmunoprecipitation studies of human resistance arteries. Novel contacts between eNOS and hemoglobin were mapped using molecular modeling and simulation. Pharmacological or genetic disruption of the eNOS-hemoglobin complex was evaluated using pressure myography. The association between alpha globin gene deletion and blood pressure was assessed in a population study. RESULTS Alpha and beta globin transcripts were detected in the endothelial layer of the artery wall. Imaging colocalized alpha and beta globin proteins with eNOS at myoendothelial junctions. Immunoprecipitation demonstrated that alpha globin and beta globin form a complex with eNOS and cytochrome b5 reductase. Modeling predicted negatively charged glutamic acids at positions 6 and 7 of beta globin to interact with positively charged arginines at positions 97 and 98 of eNOS. Arteries from donors with a glutamic acid-to-valine substitution at beta globin position 6 (sickle trait) exhibited increased NOS-dependent vasodilation. Alpha globin gene deletions were associated with decreased arterial alpha globin expression, increased NOS-dependent vasodilation, and lower blood pressure. Mimetic peptides that targeted the interactions between hemoglobin and eNOS recapitulated the effects of these genetic variants on human arterial vasoreactivity. CONCLUSIONS Alpha and beta globin subunits of hemoglobin interact with eNOS to restrict NO signaling in human resistance arteries. Malaria-protective genetic variants that alter the expression of alpha globin or the structure of beta globin are associated with increased NOS-dependent vasodilation. Targeting the hemoglobin-eNOS interface could potentially improve NO signaling in diseases of endothelial dysfunction such as severe malaria or chronic cardiovascular conditions.

中文翻译：

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镰状特征和 α 地中海贫血通过破坏内皮血红蛋白-eNOS 相互作用来增加人体动脉的 NOS 依赖性血管舒张。


背景 严重的疟疾与一氧化氮 （NO） 合酶 （NOS） 依赖性血管舒张受损有关，逆转这种缺陷可以提高小鼠模型的生存率。疟疾可能选择了增加内皮 NO 信号传导的遗传多态性，现在导致人类血管功能的异质性。一种可能选择的蛋白质是 α 珠蛋白，在小鼠模型中，它与内皮 NOS （eNOS） 相互作用以负向调节 NO 信号传导。我们试图评估 α 珠蛋白基因缺失对 NO 信号传导的影响，出乎意料地发现人类动脉不仅使用 α 珠蛋白，还使用 β 珠蛋白来调节 eNOS。方法 通过多光子成像、基因表达分析和人抵抗动脉免疫共沉淀研究对 eNOS-血红蛋白复合物进行表征。使用分子建模和模拟绘制 eNOS 和血红蛋白之间的新接触。使用压力肌图评估 eNOS-血红蛋白复合物的药理学或遗传破坏。在一项人群研究中评估了 α 珠蛋白基因缺失与血压之间的关联。结果 在动脉壁内皮层检测到 α 和 β 珠蛋白转录物。在肌内皮连接处使用 eNOS 共定位的 α 和 β 珠蛋白成像。免疫沉淀表明，α 珠蛋白和 β 珠蛋白与 eNOS 和细胞色素 b5 还原酶形成复合物。建模预测了 β 珠蛋白第 6 位和第 7 位带负电荷的谷氨酸与 eNOS 第 97 位和第 98 位带正电的精氨酸相互作用。在 β 珠蛋白位置 6 （镰状性状） 具有谷氨酸-缬氨酸取代的供体的动脉表现出 NOS 依赖性血管舒张增加。 α 珠蛋白基因缺失与动脉 α 珠蛋白表达降低、NOS 依赖性血管舒张增加和血压降低相关。靶向血红蛋白和 eNOS 之间相互作用的模拟肽概括了这些遗传变异对人类动脉血管反应性的影响。结论 血红蛋白的 α 和 β 珠蛋白亚基与 eNOS 相互作用以限制人类抵抗动脉中的 NO 信号传导。改变 α 珠蛋白表达或 β 珠蛋白结构的疟疾保护性遗传变异与 NOS 依赖性血管舒张增加有关。靶向血红蛋白-eNOS 界面可能会改善内皮功能障碍疾病（如严重疟疾或慢性心血管疾病）中的 NO 信号传导。