Dynamics of Regulating Oxygen Supply by Erythrocytes

红细胞调节供氧的动力学

• 批准号: RGPIN-2014-04615
• 负责人: Ellis, Christopher
• 金额: $ 2.19万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566634
• 关键词: Dynamics; Regulating; Oxygen; Supply; Erythrocytes

Arguably the most important function of the vasculature is the delivery of adequate oxygen (O2) to every cell of the body. Since the distance O2 can diffuse from red blood cells (RBCs) in a vessel to where it is consumed in the cell to produce energy is <0.1-mm, the vasculature must properly distribute O2 supply down to the level of a single terminal arteriole (very small artery) supplying a small number of capillaries supporting these cells. This level of accuracy in distributing O2 cannot be built into the vascular structure during development, it must be dynamically regulated to respond to varying needs of the tissue being served (e.g. in skeletal or cardiac muscle depending on the level of physical activity). We were the first to propose that the red blood cell, which is the primary carrier of O2, is also the sensor which enables this fine level of control of the distribution of O2. RBCs sense the balance between the O2 supply and O2 consumption by the change in the amount of O2 carried by hemoglobin in the RBC. As O2 binds to hemoglobin the shape of the molecule changes which both activates enzymes within the RBC to produce adenosine triphosphate (ATP) and triggers a signalling pathway in the RBC membrane for ATP to be released from the RBC. The ATP activates specialized receptors (P2y) on the inner surface of endothelial cells lining the vessel which result in an increase in arteriolar diameter, either locally in arterioles by the release of nitric oxide or prostaglandins or remotely from capillaries and venules via a electrical signal conducted through endothelial cells to the arterioles. There are unresolved issues about the O2 dependent release of ATP which existing technologies cannot answers. The primary question is how long does it take for ATP to be released from the RBC following a change in hemoglobin O2 saturation? The answer is important since the release time determines the spatial accuracy with which O2 saturation levels can be reported to the vascular endothelium. Existing techniques only provide the how much ATP is released for a change in O2 saturation and cannot be used to determine fast ATP is released. Recent advances by my Ph.D. student, Richard Sové, make it possible for us to answer this question and, in doing so; gain new insights into the mechanisms regulating ATP release. Sové developed and published a computational model for the potential design of a microfluidic device which could be used to measure the dynamics of ATP release. He added a dynamic signaling pathway model for ATP release into his microfluidic model and has demonstrated that this microfluidic approach is able to reveal how the speed of each stage in the signaling pathway. Sové’s approach can also answer the question is the release rate of ATP from the RBC governed by the level of O2 saturation or by the rate at which O2 saturation is changing? Another model predicts that O2 distribution can only be regulated by RBCs if ATP release depends on the rate of O2 saturation change; thus the answer is critical to our understanding of the RBC’s role in regulating O2 supply. This proposal focuses on developing the microfluidic system proposed by Sové for fully characterizing the dynamics of O2 dependent ATP release from RBCs. All research will be carried out on rat blood to maintain consistency with previous research. This technology creates the opportunity for other graduate student projects investigating the impact of conditions the RBC would encounter in the microvasculature in vivo and forms the basis for a future collaborative health research projects to translate this research into a screening to tool for patients with cardiovascular disease.

可以说，血管系统最重要的功能是向身体的每个细胞输送足够的氧气（O2）。由于O2可以从血管中的红细胞（RBC）扩散到细胞中消耗以产生能量的地方的距离<0.1 mm，因此血管系统必须将O2供应适当地分配到单个末端小动脉（非常小的动脉）的水平，从而供应少量毛细血管来支持这些细胞。在发育过程中，这种分配O2的准确性水平不能建立在血管结构中，它必须动态调节以响应所服务的组织的不同需求（例如，在骨骼肌或心肌中，取决于身体活动的水平）。我们是第一个提出红细胞，这是氧气的主要载体，也是传感器，使这种精细的控制水平的氧气分布。红细胞通过红细胞中血红蛋白携带的O2量的变化来感知O2供应和O2消耗之间的平衡。当O2与血红蛋白结合时，分子的形状发生变化，这既激活RBC内的酶以产生三磷酸腺苷（ATP），又触发RBC膜中的信号通路以从RBC释放ATP。ATP激活内衬血管的内皮细胞内表面上的特化受体（P2 γ），这导致小动脉直径的增加，或者通过释放一氧化氮或胰高血糖素在小动脉中局部地增加，或者通过经由内皮细胞传导到小动脉的电信号远离毛细血管和小静脉增加。关于ATP的O2依赖性释放存在现有技术无法解决的未解决的问题。主要问题是血红蛋白O2饱和度发生变化后，ATP从RBC中释放需要多长时间？答案很重要，因为释放时间决定了向血管内皮报告氧饱和度水平的空间准确性。现有技术仅提供了对于O2饱和度的变化释放了多少ATP，并且不能用于确定快速释放ATP。我的博士学位的最新进展学生，理查德·索夫，使我们有可能回答这个问题，并在这样做;获得新的见解调节ATP释放的机制。Sové开发并发表了一个计算模型，用于微流体装置的潜在设计，该装置可用于测量ATP释放的动力学。他在他的微流体模型中添加了ATP释放的动态信号通路模型，并证明了这种微流体方法能够揭示信号通路中每个阶段的速度。Sové的方法也可以回答这样一个问题：红细胞释放ATP的速率是由氧饱和度的水平决定的，还是由氧饱和度变化的速率决定的？另一个模型预测，如果ATP释放取决于O2饱和度变化率，则O2分布只能由RBC调节;因此，答案对于我们理解RBC在调节O2供应中的作用至关重要。该提案的重点是开发Sové提出的微流体系统，以充分表征RBC中O2依赖性ATP释放的动力学。所有研究将在大鼠血液中进行，以保持与先前研究的一致性。这项技术为其他研究生项目创造了机会，研究红细胞在体内微血管系统中遇到的条件的影响，并为未来的合作健康研究项目奠定了基础，将这项研究转化为心血管疾病患者的筛查工具。