ISCHEMIC PROTECTION OF RETINA BY HYPOXIC PRECONDITIONING

描述（由申请人提供）：适应压力的能力是基本的生理学原理。 通过有意地对动物、组织或细胞施加特定的压力，并研究由此诱导的内源性保护反应，研究人员可以发现治疗干预的新策略。 最近，这种方法已被利用在缺血-再灌注领域，其中依赖于基因表达变化的对缺血损伤的强大“耐受性”可以通过预先暴露于短暂的非损伤性缺血或缺氧来触发。 迄今为止，这种“预处理”治疗在性质上是单一的，并且所产生的耐受持续时间是短暂的。 我们假设，重复预处理将赋予组织更长的缺血耐受持续时间。事实上，我们最近的研究结果在小鼠中使用重复介绍轻度全身缺氧或多次注射缺氧模拟去铁胺，以预处理视网膜支持这一假设。 通过形态学和功能标准，我们可以证明神经保护表型持续数月而不是数天。如此长时间的适应性变化，以及触发这种反应的能力，是前所未有的发现。 本申请中提出的研究旨在开始系统地阐明诱导机制，从而诱导这种持久的表型适应期;我们将重点关注转录因子“缺氧诱导因子-1 α”（HIF-1 a）的参与。 第一个目标的研究将检查我们的单一和重复缺氧和去铁胺为基础的预处理方案是如何影响HIF-1a蛋白表达的。 HIF-1a参与预处理反应的因果关系证据将在利用HIF-1a敲除小鼠和寡核苷酸阻断该转录因子的Aim 2研究中出现。 HIF-1a信号传导与预处理诱导的一氧化氮产生变化的关系将在Aim 3研究中阐明，这是基于我们在一氧化氮合酶缺失小鼠中不能实现视网膜缺血耐受的观察。了解这些内源性适应性反应的分子基础具有巨大的临床前景，因为这些机制可以作为缺血性视网膜病变和青光眼风险患者的新治疗靶点。

DESCRIPTION (provided by applicant): The ability to adapt to a stress is a fundamental physiologic principle. By intentionally imposing a particular stress on animals, tissues, or cells, and studying the endogenous protective responses so induced, investigators can uncover new strategies for therapeutic intervention. Recently, this approach has been leveraged in the field of ischemia-reperfusion, where a robust "tolerance" to ischemic injury that is dependent on changes in gene expression can be triggered by pre-exposure to brief, noninjurious ischemia or hypoxia. To date, such "preconditioning" treatments are singular in nature, and the resulting duration of tolerance is short lasting. We hypothesized that repetitive preconditioning treatments would confer a much longer lasting period of ischemic tolerance in the tissue. Indeed, results of our recent studies in mice using repetitive presentations of mild systemic hypoxia or multiple injections of the hypoxia-mimetic deferroxamine to precondition the retina support this hypothesis. By both morphologic and functional criteria, we can document a neuroprotective phenotype that lasts for months instead of days. Such protracted periods of adaptive change, and the ability to trigger this response pharmacologically, are unprecedented findings. Studies proposed in this application are designed to begin to systematically elucidate the induction mechanisms whereby this long-lasting period of phenotypic adaptation is induced; we will focus on the involvement of the transcription factor 'hypoxia-inducible factor-1 alpha' (HIF-1a). Studies in the first aim will examine how HIF-1a protein expression is affected by our single and repetitive hypoxic and deferroxamine-based preconditioning regimens. Causal evidence for HIF-1a involvement in the preconditioning response will be forthcoming in Aim 2 studies utilizing HIF-1a knockout mice and oligonucleotide blockade of this transcription factor. The relationship of HIF-1a signaling to preconditioning-induced changes in nitric oxide production will be elucidated in Aim 3 studies, based on our observation that retinal ischemic tolerance cannot be achieved in nitric oxide synthase null mice. Understanding the molecular basis of these endogenous adaptive responses holds tremendous clinical promise, as these mechanisms can serve as new therapeutic targets for patients at risk for ischemic retinopathies and glaucoma.