Study of the mechanisms of pulse-pressure dependent regulation of vascular tone

脉动血流滋养器官，取决于心脏的收缩能力、外周阻力和大电导动脉僵硬。很少有研究报道脉动血流可以更好地调节血压、改善肾脏血流灌注和减少炎症反应。脉动流对脑血流(CBF)调节的影响，以及参与机械传感和机械转导的分子机制尚不清楚。我们假设这些生理通路是决定性的，了解它们将有助于开发跟踪CBF反应性的创新诊断工具，这被认为是年龄相关认知功能受损的基础。 目标 我们的研究计划有三个目标，并将集中于脑循环：1)在分离的小鼠脑动脉上展示脉压调节脑血管肌源性张力和内皮依赖性切应力敏感性；2)确定连接脉压和脑血管张力的机械传感和机械转导的分子通路；3)在体内和体外调节脑血管脉压，以研究体外和长期CBF调节的功能结果。 科学方法 我们与蒙特利尔理工学院的弗雷德里克·莱萨奇博士合作开发了一种独特的脉冲发生器。我们的新数据现在在线表明，脉压增加肌源性张力和血管内皮细胞切应力敏感性，同时调节一氧化氮合酶活性，这一反应在动脉粥样硬化前条件和衰老中受损：这将通过HSFC的拨款进行研究(2015/2018)。与NSERC的应用直接相关的是，我们未发表的数据表明M受体是一种机械传感器，而机械转导可能依赖于NADPH氧化酶2和血管生成素样蛋白-2(Angptl2)来调节细胞内的活性氧。我们将使用体外药理学工具，使用体内递送表达靶向shRNA的内皮特异性相关腺病毒2，以及使用我们的angptl2-/-小鼠来挑战这些途径。为了增加脑血管循环中的脉压，我们将产生一种横向主动脉收缩，导致立即单侧(右侧)脉压升高。成像将由7T-MRI和OCT分别进行，以测量全球脑血流量和软脑膜血管的搏动性和血流量。 作品的新颖性和预期意义 技术方法是独一无二的，旨在解决我们的问题：脉压是静息和代谢需求时CBF整体调节的一个组成部分吗？这将有助于确定生理上调节脑血管反应性和脑血流的脉压范围，以及脉压如何将其信号传递到大脑小动脉。

Pulsatile blood flow nourishes the organs and depends on cardiac contractility, peripheral resistances and large conductance artery stiffness. Few studies reported that pulsatile flow leads to better blood pressure regulation, kidney perfusion and a reduced inflammation. Neither the impact of pulsatile flow on cerebral blood flow (CBF) regulation, nor the molecular mechanisms involved in mechanosensing and mechanotransduction are known. We hypothesize that these physiological pathways are determinant and knowing them will help develop innovative diagnostic tools tracking CBF reactivity, that is believed to be at the basis of age-related cognitive decline when impaired. Objectives Our research program has 3 objectives and will focus on the cerebral circulation: 1) to demonstrate in isolated mouse cerebral arteries that pulse pressure regulates cerebrovascular myogenic tone and endothelium-dependent shear stress sensitivity; 2) to identify the molecular pathways involved in mechanosensing and mechanotransduction connecting pulse pressure to cerebrovascular tone; 3) to modify cerebrovascular pulse pressure both in vivo and ex vivo to study the functional outcome ex vivo and on long term CBF regulation. Scientific approach We developed a unique pulse-generator in collaboration with Dr. Frédéric Lesage from the Polytechnic School of Montreal. Our new data now online demonstrate that pulse pressure increases myogenic tone and endothelial shear stress sensitivity ex vivo while regulating nitric oxide synthase activity, a response that is impaired in proatherogenic conditions and aging: this will be studied through a grant of the HSFC (2015/2018). Directly in relation to this NSERC application, our unpublished data point to the muscarinic type 5 receptor as a mechanosensor, while mechanotransduction may be dependent on NADPH oxidase 2 and angiopoietin like-2 (angptl2) to regulate cellular reactive oxygen species. We will challenge these pathways using pharmacological tools ex vivo; using in vivo delivery of endothelial-specific associated adenovirus 2 expressing targeted shRNA; and using our angptl2-/- mice. To increase pulse pressure in the cerebrovascular circulation, we will produce a transverse aortic constriction that leads to an immediate unilateral (right side) increase in pulse pressure. Imaging will be performed by 7T-MRI and OCT to measure global CBF, and pial vessel pulsatility and flow, respectively. Novelty and expected significance of the work The technical approach is unique and designed to address our question: is the pulse pressure an integrated component of the overall regulation of CBF at rest and during metabolic demand? This will help determining the range of pulse pressure that physiologically regulates cerebrovascular reactivity and CBF, and how pulse pressure transduces its signal to the cerebral arterioles.