Red Blood Cell S-nitrosothiols and Oxygenation

描述（由申请人提供）：肺的氧摄取由肺泡通气（VA）与血流（灌注，Q）的局部匹配控制。VA/Q匹配由血管中平滑肌张力的pO 2依赖性调节介导，其中动脉压反映生理反应、缺氧性肺血管收缩（HPV）的操作。虽然pO 2可以直接调节平滑肌，但VA/Q匹配的细胞机制尚未完全阐明。我们研究的中心主题是红细胞（RBC）在肺-血界面控制O2摄取中的新兴作用。我们已经证明，红细胞调节HPV，从而肺动脉压，并改善氧合，这些作用是通过pO 2依赖性的S-亚硝基血红蛋白（SNO-Hb）的形成和随后的血管舒张性一氧化氮（NO）当量的传递介导的。此外，我们已经令人惊讶地发现，从SNO-Hb递送NO相关的生物活性至少部分地通过扩张气道来改善通气。因此，该建议的中心假设是，通过调节肺泡单位的通气和灌注，由RBC调节的pO 2生物活性NO当量的产生和递送在VA/Q匹配中起着重要作用。为了阐明红细胞在VA/Q匹配中的作用以及控制肺中NO相关生物活性的形成和传递的酶机制，我们开发了小鼠和兔缺氧性肺动脉高压模型，其中使用遗传和生化方法操纵SNO-Hb水平。我们将使用这些模型来检验以下特定假设：1）SNO-Hb的缺乏或过量通过破坏VA/Q匹配来干扰肺内的最佳气体交换; 2）SNO-Hb形成所需的NO当量的酶源（因此对于最佳血氧）是eNOS（因此，eNOS在VA/Q匹配中的作用很大程度上是通过RBC的作用来实现的）; 3）RBC内的SNO-Hb水平（以及由此肺的O2摄取）受酶S-亚硝基谷胱甘肽还原酶的关键调节; 4）RBC递送基于NO的生物活性需要γ-谷氨酰转肽酶的重要作用。了解RBC如何调节优化气体交换的协调的肺血管和气道反应应有助于肺功能障碍的新的诊断和治疗方法，包括急性肺损伤、输血相关的发病率和慢性低氧血症性肺病，并且还指出RBC衍生的血管活性在以组织低氧血症为特征的其他病症中的潜在作用（例如，败血症和心力衰竭）。 公共卫生相关性：红细胞（RBC）含有血管扩张的S-亚硝基硫醇（SNO），并被认为在分配一氧化氮生物活性方面具有新的作用。我们最近发现，肺动脉高压患者存在RBC SNO缺乏，这会损害RBC血管舒张，而SNO的补充与RBC生物活性和肺功能的改善相关。在这里，我们采用药理学和遗传学方法来探索红细胞可以调节肺血管和气道张力的可能性，从而优化气体交换（氧摄取），我们提供了新的分子见解，可能会广泛影响心脏，肺和血液疾病的诊断和治疗，包括败血症，心力衰竭和肺动脉高压。

DESCRIPTION (provided by applicant): Oxygen uptake by the lung is governed by local matching of alveolar ventilation (VA) to blood flow (perfusion, Q). VA/Q matching is mediated by pO2-dependent regulation of smooth muscle tone in blood vessels where arterial pressure reflects operation of the physiological response, hypoxic pulmonary vasoconstriction (HPV). Although pO2 can directly regulate smooth muscle, the cellular mechanisms of VA/Q matching have not been fully elucidated. The central theme of our research is the emerging role of red blood cells (RBCs) in the control of O2 uptake at the lung-blood interface. We have demonstrated that RBCs regulate HPV and thus pulmonary artery pressure, and improve oxygenation, and that these effects are mediated through the pO2- dependent formation of S-nitroso-hemoglobin (SNO-Hb) and subsequent delivery of vasodilatory nitric oxide (NO) equivalents. In addition, we have found, surprisingly, that the delivery of NO-related bioactivity from SNO-Hb improves ventilation, at least in part by dilating airways. Thus, the central hypothesis of this proposal is that the pO2-regulated generation and delivery of bioactive NO equivalents by RBCs plays a significant role in VA/Q matching, by regulating both ventilation and perfusion of alveolar units. To elucidate the role of RBCs in VA/Q matching and the enzymatic mechanisms that govern the formation and delivery of NO-related bioactivity in the lung, we have developed murine and rabbit models of hypoxic pulmonary hypertension, in which SNO-Hb levels are manipulated using genetic and biochemical approaches. We will use these models to test the specific hypotheses that: 1) deficiency or excess of SNO-Hb interferes with optimal gas exchange within the lung by disrupting VA/Q matching; 2) the enzymatic source of NO equivalents required for SNO-Hb formation (and thus for optimal blood oxygenation) is eNOS (and therefore the role of eNOS in VA/Q matching is carried out in significant part through the agency of RBCs); 3) SNO-Hb levels within RBCs (and thereby O2 uptake by the lung) are critically regulated by the enzyme S-nitrosoglutathione reductase; 4) the delivery of NO-based bioactivity by RBCs entails an essential role for gamma-glutamyl transpeptidase. Understanding how RBCs regulate the coordinated pulmonary vascular and airway responses that optimize gas exchange should facilitate novel diagnostic and therapeutic approaches to lung dysfunction, including acute lung injury, transfusion-related morbidity and chronic hypoxemic lung disease, and also point to potential roles of RBC- derived vasoactivity in other disorders that are characterized by tissue hypoxemia (e.g., sepsis and heart failure). PUBLIC HEALTH RELEVANCE: Red blood cells (RBCs) contain vasodilatory S-nitrosothiols (SNO) and have been ascribed a novel role in dispensing nitric oxide bioactivity. We have recently shown that patients with pulmonary hypertension have a deficiency of RBC SNO that impairs RBC vasodilation, and that repletion of SNO is associated with improvements in both RBC bioactivity and pulmonary function. Here we employ pharmacologic and genetic approaches to explore the possibility that RBCs can modulate both pulmonary vascular and airway tone, thereby optimizing gas exchange (oxygen uptake), and we offer new molecular insights that may broadly impact the diagnosis and treatment of heart, lung and blood diseases, including sepsis, heart failure, and pulmonary arterial hypertension.