Red Blood Cell S-nitrosothiols and Oxygenation

描述(申请人提供)：肺的摄氧量取决于肺泡通气量(VA)与血流(灌注量，Q)的局部匹配。VA/Q匹配是由动脉压反映操作的生理反应，即缺氧性肺血管收缩(HPV)的PO2依赖的血管平滑肌张力调节所介导的。尽管PO2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-血液界面控制氧气摄取中的新角色。我们已经证明，红细胞调节HPV，从而调节肺动脉压，并改善氧合，这些作用是通过PO2依赖的S亚硝基血红蛋白(SNO-Hb)的形成和随后的血管扩张性一氧化氮(NO)等价物的传递来实现的。此外，我们发现，令人惊讶的是，SNO-HB提供的NO相关生物活性改善了通风，至少部分是通过扩张呼吸道。因此，这一建议的中心假设是，红细胞通过调节肺泡单位的通气性和灌注性，在VA/Q匹配中发挥重要作用。为了阐明红细胞在VA/Q匹配中的作用以及控制肺中NO相关生物活性形成和传递的酶机制，我们建立了小鼠和兔缺氧性肺动脉高压模型，其中SNO-Hb水平通过遗传和生化方法进行调控。我们将使用这些模型来检验特定的假设：1)SNO-Hb的不足或过量通过扰乱VA/Q匹配来干扰肺内最佳的气体交换；2)SNO-Hb的形成(从而为最佳血液氧合所需的NO等价物)的酶来源是eNOS(因此eNOS在VA/Q匹配中的作用在很大程度上是通过红细胞的作用进行的)；3)红细胞内的SNO-HB水平(从而肺对O2的摄取)受到酶S亚硝基谷胱甘肽还原酶的关键调节；4)红细胞传递基于NO的生物活性需要γ-谷氨酰转肽酶的重要作用。了解红细胞如何调节协调的肺血管和呼吸道反应以优化气体交换，将有助于肺功能障碍的新诊断和治疗方法，包括急性肺损伤、输血相关发病率和慢性缺氧性肺疾病，并指出红细胞衍生的血管活性在其他以组织低氧血症(例如败血症和心力衰竭)为特征的疾病中的潜在作用。 与公共健康相关：红细胞(RBC)含有扩张血管的S亚硝硫醇(SNO)，已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的缺乏，这会损害RBC的血管扩张，而SNO的恢复与RBC生物活性和肺功能的改善有关。在这里，我们使用药理学和遗传学方法来探索红细胞可以调节肺血管和呼吸道张力，从而优化气体交换(氧摄取)的可能性，我们提供了可能广泛影响心、肺和血液疾病的诊断和治疗的新的分子见解，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.