KLF2 as a regulator of endothelial cell biology

描述(申请人提供)：血管内皮细胞是血管功能的重要调节因子。越来越多的临床和实验研究有力地支持了动脉粥样硬化是一种慢性炎症性疾病的假说。暴露在炎性细胞因子下会导致因子的表达和/或细化，从而允许免疫细胞募集和黏附到血管壁。然而，尽管有这种全身性炎症状态，动脉粥样硬化的病变表现出非随机的分布模式，如分支点和主要弯曲区。这些观察结果导致了一种假设，即局部事件，如流体机械力，可以影响内皮功能。事实上，实验研究表明，均匀的层流赋予内皮细胞抗增殖、抗血栓、抗粘连和抗氧化的特性。为了更好地了解炎症刺激和流体作用力如何影响内皮细胞生物学，我们采用了基因组图谱方法来评估基因表达的全球模式。这些研究证实，转录因子KLF2是由层流切应力诱导的，并被炎性细胞因子IL-1β抑制。KLF2在内皮细胞中的过表达强烈地诱导了内皮一氧化氮合酶的表达和活性，内皮型一氧化氮合酶是血管内稳态的中枢调节因子。此外，KLF2还能有效抑制血管内皮细胞黏附分子如VCAM-1和E-选择素对多种炎症刺激的诱导。与这些观察结果一致的是，体外流动分析表明，免疫细胞与内皮单层的附着和滚动明显减弱。最后，我们的研究表明，转录共激活因子cAMP反应元件结合蛋白(CBP/p300)的招募是KLF2这些不同作用的统一机制。这些观察结果支持了KLF2作为调节内皮功能的“分子开关”的重要作用。在本提案的目的1和2中，将进行研究，以了解KLF2诱导eNOS和抑制细胞因子介导的黏附分子诱导的分子基础。在目标3中，我们将在体内以内皮特异的方式过度表达KLF2，并评估其对血管炎症和血管反应性的影响。这些研究将提供对KLF2在健康和疾病状态下内皮细胞生物学中的作用的详细了解。

DESCRIPTION (provided by applicant): The vascular endothelium is a critical regulator of vascular function. Accumulating clinical and experimental studies strongly support the hypothesis that atherosclerosis is a chronic inflammatory disease state. Exposure to inflammatory cytokines results in the expression and/or elaboration of factors, which allow for immune cell recruitment and adhesion to the blood vessel wall. However, despite this systemic inflammatory state, the lesions of atherosclerosis show a non-random pattern of distribution such as branch points and areas of major curvature. These observations have led to the hypothesis that local events such as fluid mechanical forces can affect endothelial function. Indeed, experimental studies demonstrate that uniform laminar flow confers anti-proliferative, anti-thrombotic, anti-adhesive, and anti-oxidant properties to the endothelium. To obtain a greater understanding of how inflammatory stimuli and fluid forces impact on endothelial cell biology, we undertook a genomic profiling approach to assess global patterns of gene expression. These studies identified the transcription factor KLF2 as being induced by laminar shear stress and inhibited by the inflammatory cytokine IL-lbeta. Over expression of KLF2 in endothelial cells robustly induced the expression and activity of endothelial nitric oxide synthase - a central regulator of vascular homeostasis. In addition, KLF2 potently inhibits the induction of endothelial adhesion molecules such as VCAM-1 and E-selectin in response to diverse inflammatory stimuli. Consistent with these observations, in vitro flow assays demonstrate that immune cell attachment and rolling to an endothelial monolayer is markedly attenuated. Finally, our studies implicate recruitment of the transcriptional coactivator cyclic AMP response element-binding protein (CBP/p300) as a unifying mechanism for these distinct effects of KLF2. These observations support an important role for KLF2 as a "molecular switch" which regulates endothelial function. In AIM 1 and 2 of this proposal studies will be undertaken to understand the molecular basis for KLF2 ability to both induce eNOS and inhibit the cytokine- mediated induction of adhesion molecules. In AIM 3 we will overexpress, in an endothelial specific manner, KLF2 in vivo and assess for effects on vascular inflammation and vasoreactivity. These studies will provide a detailed understanding of KLF2 role in endothelial cell biology in health and disease states.