Endothelial Akt in Vascular Injury

描述(申请人提供)：蛋白激酶B/Akt是一种丝氨酸-苏氨酸激酶，作用于磷脂酰肌醇3-激酶(PI3K)下游，由许多内源性配体诱导，如胰岛素、胰岛素样生长因子-1、类固醇激素和他汀类药物。Akt的磷酸化导致多种信号通路的调节，具有潜在的心血管保护作用，包括糖原合成酶激酶(GSK)-3b的失活，葡萄糖转运体(GLUT)-4的激活，以及caspase-9的抑制。然而，内皮Akt在血管损伤和动脉粥样硬化中的作用尚不清楚。在内皮细胞中，最近的研究集中在Akt对内皮型一氧化氮合酶(ENOS)的激活。内皮一氧化氮合酶是Akt的底物，Akt在Ser1179处使eNOS磷酸化，导致eNOS活性增加和NO产生。内皮来源的一氧化氮由于其扩张血管、抗炎和抗氧化的特性而具有心血管保护作用。因此，通过Akt刺激内皮细胞中的eNOS可能成为减轻动脉粥样硬化和血管炎症的一个有前途的靶点。虽然Akt可能在血管内稳态中发挥重要作用，但关于内皮Akt在血管疾病中的作用还不是很清楚。这一限制主要是由于缺乏可用于组织特异性调节Akt的药理学工具。因此，使用组织限制性靶向基因破坏或调节的遗传学方法更有可能阐明Akt在内皮细胞中的特定功能。为此，我们建立了过量表达AKT基因的转基因小鼠，利用Cre/loxP系统可诱导其靶向内皮细胞。提出了三个具体目标，将研究血管内皮细胞Akt在血管损伤和动脉粥样硬化模型中的作用。

DESCRIPTION (provided by applicant): Protein kinase B/Akt is a serine-threonine kinase which acts downstream of phosphatidylinositol 3-kinase (PI3K) and is induced by many endogenous ligands such as insulin, insulin-like growth factor-1, steroid hormones, and statins. Phosphorylation of Akt leads to modulation of a variety of signal pathways with potential cardiovascular protective effects including inactivation of glycogen synthase kinase (GSK)-3b, activation of glucose transporter (Glut)-4, and inhibition of caspase-9. However, the role of endothelial Akt in vasculary injury and atherosclerosis is not known. In endothelial cells, recent studies have focused on the activation of endothelial nitric oxide synthase (eNOS) by Akt. Endothelial NOS is a substrate for Akt, which phosphorylates eNOS at Ser 1179, leading to increased eNOS activity and NO production. Endothelium- derived NO is cardiovascularly protective due to its vasodilating, anti-inflammatory, and antioxidative properties. Stimulation of eNOS via Akt in endothelial cells, therefore, may be a promising target for attenuating atherosclerosis and vascular inflammation. Although Akt could potentially play a critical role in vascular homeostasis, not much is known regarding the contribution of endothelial Akt in vascular disease. This limitation is mostly due to the lack of pharmacological tools available for a tissue-specific modulation of Akt. Consequently, a genetic approach using tissue-restricted targeted gene disruption or modulation is more likely to elucidate the specific function of Akt in the endothelium. For this purpose, we have developed transgenic mice overexpressing constitutively-active or dominant-negative mutants of Akt, which could be inducibly targeted to the endothelium using the Cre/loxP system. Three specific aims are proposed, which will study the role of endothelial Akt in models of vascular injury and atherosclerosis.