Sigma Receptor Signaling in Focal Ischemia

在过去的五年中，我们已经证明，药理学激活sigma 1受体大大改善了自然过程中的脑损伤后，短暂的局灶性缺血。此外，已知衰老的神经功能恶化可能至少部分是由于已知为σ 1受体激动剂的内源性激素（例如DHEA）的天然减少。我们以前的工作表明，系统管理 sigma 1受体激动剂改善实验性中风的结果，即使这些药物是在再灌注开始后给药。此外，我们证明了sigma 1受体激动剂干扰缺血性脑损伤的主要机制（NMDA受体介导的NO毒性）。目前的建议的总体目标是测试的假设，sigma 1受体激动剂引起神经保护作用的sigma 1受体和干扰脑损伤的具体平行机制。目的1利用细胞培养技术研究sigma 1受体激动剂对NMDA诱导的NO产生的干扰机制。待检验的假设是原型σ 1受体激动剂PPBP间接损害NMDA与其受体的结合，并且不直接影响NMDA受体。 信号转导途径中的后续步骤。无论确切的作用部位如何，由于一些sigma 1受体激动剂已被证明通过G蛋白机制起作用，因此目标2将描述G蛋白在基础和缺血后sigma 1受体信号传导机制中的作用。假设PPBP损害NMDA刺激的 NOS活性通过涉及G蛋白的机制。作为一个平行的途径，我们还将评估PPBP的全身给药是否会影响细胞凋亡的发生。为此，目的3将检验PPBP给药与缺血边缘区bcl-2和bcl-x-1表达增加和bax表达减少相关的假设。目的4将评估已知为σ 1受体激动剂的内源性激素的治疗功效。我们将测试这一假设，即短暂性局灶性缺血后DHEA的治疗效果与NO的产生减少有关，并且可以被特异性σ 1受体拮抗剂阻断。目的5旨在确定在再灌注时施用σ 1受体激动剂时的保护机制。我们将测试的假设，即延迟管理局灶性缺血再灌注期间的PPBP与iNOS的表达减少，通过管理的sigma 1受体拮抗剂阻断的机制。

During the past five years we have demonstrated that pharmacologic activation of sigma1 receptors greatly ameliorates the natural process of brain injury following transient focal ischemia. In addition, it is known that neurologic deterioration of aging, may be at least partially result from the natural reducation in endogenous hormones (e.g. DHEA) that are known to be agonists of the sigma1 receptor. Our previous work demonstrates that systemic administration of sigma1-receptor agonists improve outcome from experimental stroke, even when these agents are administered after the onset of reperfusion. In addition, we demonstrated that sigma1receptor agonists interfere with a primary mechanism of ischemic brain injury (NMDA receptor mediated NO toxicity). The overall goal of the current proposal is to test the hypothesis that sigma1receptor agonists cause neuroprotection by acting at sigma1receptors and interfering with specific parallel mechanisms of brain injury. Aim 1 will use cell culture techniques to determine the mechanism by which sigma1 receptors agonists interfere with NMDA induced NO production. The hypothesis to be tested is that the prototypic sigma1 receptor agonist PPBP indirectly impairs binding of NMDA to its receptor and does not have a direct effect on subsequent steps in the signal transduction pathway. Regardless of the exact site of action, since some sigma1 receptor agonists have been demonstrated to work through G-protein mechanisms, aim 2 will characterize the role of G-protein in basal and post-ischemic sigma1 receptor signaling mechanisms. The hypothesis is that PPBP impairs NMDA-stimulated NOS activity via a mechanism that involves a G-protein. As a parallel pathway we will also evaluate whether systemic administration of PPBP will impact the occurance of apoptosis. To this end aim 3 will test the hypothesis that PPBP administration is associated with increased bcl-2 and bcl-x-1 and decreased expression of bax in ischemic borderzones. Aim 4 will assess the therapeutic efficacy of endogenous hormones that are known to be agonists of the sigma1 receptor. We will test the hypothesis that the therapeutic efficacy of DHEA following transient focal ischemia is linked to decreased production of NO and can be blocked by specific sigma1 receptor antagonists. Aim 5 is designed to determine the mechanism for protection when the sigma1 receptor agonist is administered at the time of reperfusion. We will test the hypothesis that that delayed administration of PPBP during reperfusion from focal ischemia is associated with decreased expression of iNOS via a mechanism that is blocked by administration of a sigma1 receptor antagonist.