Shear stress, SIRT1, and Arterial Stiffening

描述（由申请人提供）：动脉硬化，表现为导管动脉增厚和弹性降低，是中风和心脏病的独立风险因素。虽然动脉硬化的病因与衰老密切相关，但其潜在的细胞和分子基础仍不清楚。在体内，血液动力学力动态地作用于血管壁，这极大地影响动脉功能和机械特性。动脉硬化可能涉及内皮对这些血流动力学力引起的剪切应力的异常反应。我们最近发现，SIRT 1，一种抗衰老的调节因子，在血管内皮细胞（ECs）中受到剪切应力的调节。此外，钙调蛋白依赖性蛋白激酶（CaMKK）似乎是一种剪切应力敏感的激酶，调节SIRT 1。因此，我们假设，剪切应力上调SIRT 1在血管内皮细胞，从而改善病理生理重塑导致动脉硬化。在上游，CaMKKb响应于生理相关的剪切应力而被激活。由于激活的CaMKKb-SIRT 1途径，内皮型一氧化氮合酶（eNOS）衍生的NO生物利用度和PGC-1a调节的ROS清除剂表达增加。因此，剪切应力增强SIRT 1的有利作用包括降低氧化应激和细胞外基质重塑。为了验证我们的假设，提出了三个具体目标。具体目标1将检查在培养的EC中诱导SIRT 1的关键血流动力学因素。然后进行分子信号传导实验以研究CaMKKb调节内皮细胞中SIRT 1对所定义的切应力的响应的机制。具体目标2将阐明剪切应力诱导的SIRT 1在EC/血管平滑肌细胞共培养系统中发挥抗硬化作用的细胞和分子机制。我们将解读SIRT 1和AMP活化蛋白激酶（AMPK）在eNOS衍生的NO生物利用度和PGC-1a调节的活性氧（ROS）清除剂中的协同作用。具体目标3将研究剪切应力激活的SIRT 1在小鼠模型动脉硬化中的作用。具体而言，我们将比较EC-sirt 1-/-敲除、Tg-EC-sirt 1和CaMKKb-/-小鼠动脉硬化的时空变化。将测量血流动力学因素、主动脉壁重塑和基因表达谱的动脉硬化相关变化并进行关联。这些研究的结果，如果如预期的那样，将有助于了解动脉硬化的机械和分子基础。 公共卫生相关性：与衰老过程相关的动脉硬化是许多心血管疾病的独立危险因素。SIRT 1是一个参与许多抗应激反应的主调节因子，我们最近发现血流动力学可以激活血管细胞中的SIRT 1。本研究将探讨SIRT 1的血流诱导机制和分子基础，这将是抗动脉硬化。该建议将显着增加我们的了解机制，血液流动与动脉硬化老化过程中的相互作用。从拟议的实验结果可能有助于其预防和/或治疗的新疗法。

DESCRIPTION (provided by applicant): Arterial stiffening, manifested by thickening and reduced elasticity of conduit arteries, is an independent risk factor for stroke and heart disease. Although the etiology of arterial stiffening correlates well with aging, the underlying cellular and molecular basis remains unclear. In vivo, hemodynamic forces dynamically act on the vascular wall, which greatly affect arterial function and mechanical properties. Arterial stiffening may involves aberrant endothelial response to shear stress resulted from these hemodynamic forces. We recently found that SIRT1, an anti-aging regulator is modulated by shear stress in vascular endothelial cells (ECs). Moreover, calmodulin-dependent protein kinase (CaMKK) appears to be a shear stress-sensitive kinase that regulates SIRT1. We thus hypothesize that shear stress upregulates SIRT1 in the endothelium of conduit arteries, which ameliorates pathophysiological remodeling leading to arterial stiffening. At the upstream, CaMKKb is activated in response to the physiologically relevant shear stress. As a consequence of the activated CaMKKb-SIRT1 pathway, the endothelial nitric oxide synthase (eNOS)-derived NO bioavailability and PGC-1a-regulated ROS scavenger expression are augmented. Thus, the advantageous effects of shear stress-augmented SIRT1 include decreased oxidative stress and remodeling of extracellular matrices. To test our hypothesis, three Specific Aims are proposed. Specific Aim 1 will examine the hemodynamic factors critical for the induction of SIRT1 in cultured ECs. Molecular signaling experiments will then be conducted to study the mechanism by which CaMKKb regulates SIRT1 in ECs responding to the defined shear stress. Specific Aim 2 will elucidate the cellular and molecular mechanisms by which shear stress-induced SIRT1 exerts anti- stiffening effects in an EC/vascular smooth muscle cell co-culture system. We will decipher the synergistic effect of SIRT1 and AMP-activated protein kinase (AMPK) in eNOS-derived NO bioavailability and PGC-1a-regulated reactive oxygen species (ROS) scavengers. Specific Aim 3 will investigate the role of shear stress-activated SIRT1 in arterial stiffening in mouse models. Specifically, we will compare the spatiotemporal changes of arterial stiffening in EC-sirt1-/- knockout, Tg-EC-sirt1, and CaMKKb-/- mice. The arterial stiffening-associated changes in hemodynamic factors, aortic wall remodeling, and gene expression profiles will be measured and correlated. Results from these proposed studies, if as anticipated, will help to understand the mechano and molecular basis of arterial stiffening. PUBLIC HEALTH RELEVANCE: Arterial stiffening, associated with the aging process, is an independent risk factor for many cardiovascular diseases. SIRT1 is a master regulator involved in many anti-stress responses and we recently found that hemodynamic force can activate SIRT1 in vascular cells. This proposed study will investigate the mechano and molecular basis of flow induction of SIRT1, which would be anti-arterial stiffening. The proposal will significantly increase our understanding of mechanisms by which blood flow interplays with aging process in arterial stiffening. Results from the proposed experiments are likely to contribute to novel therapies for its prevention and/or treatment.