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

脉动血流滋养器官，并依赖于心脏收缩力、外周阻力和大导动脉硬度。很少有研究报道搏动血流导致更好的血压调节，肾脏灌注和减少炎症。脉动流对脑血流量（CBF）调节的影响，以及涉及机械传感和机械转导的分子机制都尚不清楚。我们假设这些生理途径是决定性的，了解它们将有助于开发跟踪CBF反应性的创新诊断工具，这被认为是受损时与年龄相关的认知能力下降的基础。******目的***我们的研究计划有三个目标，并将重点放在脑循环：1)在离体小鼠脑动脉中证明脉压调节脑血管肌原性张力和内皮依赖性剪切应力敏感性；2)确定连接脉压与脑血管张力的机械传感和机械转导的分子通路；3)在体内和离体调节脑血管脉压，研究离体功能结局和对脑血流的长期调节。******科学方法***我们与蒙特利尔理工学院的fracimazric Lesage博士合作开发了一种独特的脉冲发生器。我们现在在线的新数据表明，脉压增加肌原性张力和内皮剪切应力敏感性，同时调节一氧化氮合酶活性，这一反应在促动脉粥样硬化条件和衰老中受损：这将通过HSFC的资助进行研究（2015/2018）。与NSERC应用直接相关的是，我们未发表的数据指出毒碱5型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-2 （angptl2）来调节细胞活性氧。我们将使用体外药理工具挑战这些途径；体内递送表达靶向shRNA的内皮特异性相关腺病毒2；使用我们的angptl2-/-小鼠。为了增加脑血管循环中的脉压，我们将产生一个横向主动脉收缩，导致立即单侧（右侧）脉压升高。成像将分别通过7T-MRI和OCT测量全脑血流，以及头血管脉搏和血流。******工作的新颖性和预期意义***该技术方法是独特的，旨在解决我们的问题：脉冲压力是静止和代谢需求时CBF整体调节的一个综合组成部分吗？这将有助于确定在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导到脑小动脉。

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.