Role of RBC NO and ATP in Sickle Vasculopathy

描述(由申请人提供)：血管收缩、血细胞粘连和炎症都是镰状细胞病(SCD)的潜在破坏性事件。镰刀状红细胞(SS RBC)表现为复杂的细胞膜和生物学异常。红细胞释放的一氧化氮(NO)既是维持血管扩张的关键物质，也是一种有效的抗炎药。红细胞也释放三磷酸腺苷，血流中的信号增加以满足氧气需求，通常是通过促进一氧化氮的合成。正常(AA)红细胞通过释放三磷酸腺苷(ATP)和生物活性一氧化氮(NO)而发挥缺氧感受器的作用，导致NO依赖的血管扩张，而SS红细胞缺乏释放NO和ATP的含量和能力。SS红细胞黏附内皮细胞、激活白细胞和其他细胞的能力，以及它们不能诱导肺血管扩张的能力，可能部分是由于它们缺乏膜结合的生物活性S-亚硝硫醇(SNO)和三磷酸腺苷。我们的初步数据表明，携带NO/SNO的SS红细胞在体内下调了SS红细胞黏附、S红细胞刺激的白细胞黏附和血管闭塞，并调节了血管收缩肺表型。抑制红细胞释放三磷酸腺苷还可引起红细胞黏附和肺血管收缩。在SCD中，异常的血管张力、细胞黏附、白细胞激活和炎症都被认为是血管闭塞的病理生理机制，而血管闭塞是疼痛危象和急、慢性器官损害的核心。因此，我们的中心假设是SS红细胞中NO和ATP的缺乏直接参与了SS红细胞的黏附、S红细胞诱导的白细胞活化和肺血管收缩。我们进一步推测，恢复SS或输注(储存)的AA红细胞中的NO和ATP含量也将改善SS红细胞在肺中的一些可测量的不良影响。为了验证我们的假设和在改善治疗SCD方面的进展，我们结合了SS RBC生物学、输血医学和肺生理学方面的专业研究人员的努力，以1)确定NO/SNO-和ATP-再充血对单独输注SS RBC或与调节RBC黏附事件的策略结合的完整小鼠肺血流动力学和气体交换的影响；2)在活体小鼠模型中测试SS RBC或储存的AA RBC的NO和ATP再充盈是否可以缓解血管闭塞；3)体外检测SS、RBC、NO和ATP对RBC黏附受体激活的影响及其信号转导途径，以及对RBC激活的影响。我们的长期目标是通过识别可补救的SS红细胞异常来改善SCD的血管张力、细胞黏附和细胞激活，从而减少血管闭塞。这项工作将使开发新的治疗方法来预防和控制SCD的血管闭塞和组织损伤。

DESCRIPTION (provided by applicant): Vasoconstriction, blood cell adhesion, and inflammation are each potentially devastating events in sickle cell disease (SCD). Sickle red cells (SS RBCs) demonstrate complex membrane and biologic abnormalities. Nitric oxide (NO) delivered by RBCs is both critical in the maintenance of vasodilation and a potent anti-inflammatory agent. ATP is also released by RBCs and signals increases in blood flow to meet O2 demand, typically by enhancing NO synthesis. While normal (AA) RBCs act as a hypoxia sensor by releasing both ATP and bioactive nitric oxide (NO), leading to NO-dependent vasodilation, SS RBCs are deficient in both content and ability to release both NO and ATP. The ability of SS RBCs to adhere to the endothelium and to activate leukocytes as well as other cells, along with their failure to induce pulmonary vasodilation, may result in part from their deficiencies in membrane-bound bioactive S-nitrosothiol (SNO) and ATP. Our preliminary data show that loading SS RBCs with NO/SNO down-regulates SS RBC adhesion, S RBC-stimulated leukocyte adhesion, and vaso-occlusion in vivo and modulates the vasoconstrictive pulmonary phenotype. Inhibition of ATP release by RBCs also induces RBC adhesion and pulmonary vasoconstriction. In SCD, abnormal vascular tone, cell adhesion, leukocyte activation, and inflammation are all believed to contribute to the pathophysiology of vaso-occlusion, which is central to both painful crises and acute and chronic organ damage. Thus, our central hypothesis is that NO and ATP deficits in SS RBCs directly contribute to both SS RBC adhesion, S RBC-induced activation of leukocytes, and pulmonary vasoconstriction. We further postulate that restoration of NO and ATP content in either SS or transfused (stored) AA RBCs will also improve some of the measurable adverse effects of SS RBCs in the lung. To test our hypothesis and progress toward achieving improved therapies for SCD, we have combined the efforts of investigators with expertise in SS RBC biology, transfusion medicine, and pulmonary physiology in order to 1) Determine the influence of NO/SNO- and ATP-repletion on pulmonary hemodynamics and gas exchange in isolated lungs and intact mice transfused with SS RBCs alone or in combination with strategies that modulate RBC adhesive events; 2) Test whether NO and ATP repletion of SS RBCs or stored AA RBCs can relieve vaso-occlusion in a mouse model in vivo; and 3) Determine the effect of SS RBC NO and ATP on the activation of RBC adhesion receptors in vitro, the signaling pathways involved, and RBC activation of leukocytes. Our long-term goal is to improve vascular tone, cell adhesion, and cell activation in SCD by identifying remediable SS RBC abnormalities and thereby reduce vaso-occlusion. This work will allow development of new therapeutic approaches to prevent and control vaso-occlusion and tissue damage in SCD.