Vascular Mechanisms of Cerebral Ischemic Tolerance

脑缺血耐受的血管机制

• 批准号: 7248172
• 负责人: JEFFREY M GIDDAY
• 金额: $ 9.16万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7248172
• 关键词: apoptosis; cerebral ischemia /hypoxia; cerebrovascular system; cytoprotection; disease /disorder model; gene expression; human tissue; ischemic preconditioning; laboratory mouse; microcirculation; nitric oxide synthase; protein structure function; stroke; survivin; tissue /cell culture; transcription factor; vascular endothelium

DESCRIPTION (provided by applicant): Vascular dysfunction and vascular injury, as manifested by impairments in microvascular perfusion, autoregulation, and vascular reactivity, as well as by vasogenic edema, hemorrhage, inflammation, and coagulation, contribute importantly to outcome following focal stroke. Treatment strategies may derive from studies of "ischemic tolerance", wherein endogenous mechanisms of protection are activated by different "preconditioning" stimuli. Studies outlined in this proposal will focus on elucidating the innate mechanisms responsible for protection of cerebrovascular endothelium following hypoxic preconditioning, utilizing a mouse model of induced tolerance to focal stroke and a human cerebrovascular endothelial cell culture model of ischemic tolerance, both developed and characterized in our laboratory. Key induction and expression mechanisms whereby hypoxic preconditioning attenuates diverse endpoints of ischemia-induced vascular/endothelial dysfunction and injury will be elucidated in each model. Specific Aim 1: Elucidate the role of endothelial nitric oxide synthase (eNOS) in the induction and expression pathways responsible for hypoxic preconditioning-induced cerebrovascular ischemic tolerance in vivo and in vitro. We hypothesize that eNOS-derived NO is integral to the signaling pathways responsible for inducing the transcription/translation of vasculoprotective genes. We also hypothesize that eNOS is an effector protein contributing to the ischemia-tolerant phenotype of the preconditioned cerebral microcirculation. Specific Aim 2: Delineate the involvement of the transcription factor HIF-2alpha in mediating cytoprotective gene expression in endothelial cells in vivo and in vitro in response to hypoxic and chemical preconditioning. We will test the hypothesis that the activity of HIF-2alpha, highly expressed in endothelial cells, is upregulated by these preconditioning stimuli, is modulated by eNOS-derived NO and phosphorylated Akt, and is critical to mediating the expression of cytoprotective genes in endothelium that lead to ischemic tolerance. Specific Aim 3: Elucidate the participation of survivin, a specific inhibitor-of-apoptosis family member, in the resistance of in vivo- and in vitro-preconditioned endothelium to ischemic injury, and the mechanisms by which this protein affords protection. We hypothesize that hypoxic preconditioning upregulates survivin expression, which blocks caspase-mediated endothelial injury, thereby preserving post-ischemic microcirculatory homeostasis. Identification of endogenous mechanisms of endothelial cell resistance to ischemic injury may provide novel molecular targets for the therapeutic treatment of vascular dysfunction and vascular injury following focal stroke.

描述(申请人提供)：血管功能障碍和血管损伤，表现为微血管灌注、自我调节和血管反应性的损害，以及血管源性水肿、出血、炎症和凝血，对局灶性卒中后的预后有重要影响。治疗策略可能源于对“缺血耐受”的研究，其中内源性保护机制由不同的“预适应”刺激激活。这项建议中概述的研究将集中在阐明负责低氧预适应后脑血管内皮细胞保护的固有机制，利用我们实验室建立并表征的局灶性卒中诱导耐受小鼠模型和人脑血管内皮细胞缺血耐受培养模型。在每个模型中，低氧预适应减轻缺血诱导的血管/内皮功能障碍和损伤的不同终点的关键诱导和表达机制将被阐明。 具体目的1：阐明内皮型一氧化氮合酶(ENOS)在体内、外低氧预适应诱导脑血管缺血耐受诱导和表达途径中的作用。我们假设eNOS来源的NO是诱导血管保护基因转录/翻译的信号通路中不可或缺的一部分。我们还假设eNOS是一种效应蛋白，与脑微循环预适应的缺血耐受表型有关。 特异性目的2：探讨转录因子HIF-2α在体内、外低氧和化学预适应诱导内皮细胞细胞保护基因表达中的作用。我们将验证一种假设，即在内皮细胞中高表达的HIF-2α的活性受这些预适应刺激的上调，受eNOS来源的NO和磷酸化Akt的调节，并且对于介导内皮细胞中导致缺血耐受的细胞保护基因的表达至关重要。 具体目的3：阐明凋亡抑制因子Survivin家族成员Survivin参与体内和体外预适应的内皮细胞对缺血损伤的抵抗，以及该蛋白发挥保护作用的机制。我们假设低氧预适应上调Survivin的表达，从而阻断caspase介导的内皮损伤，从而维持缺血后微循环的动态平衡。 识别血管内皮细胞抵抗缺血损伤的内源性机制可能为治疗局灶性卒中后血管功能障碍和血管损伤提供新的分子靶点。