Sigma Receptor Signaling in Focal Ischemia

局灶性缺血中的 Sigma 受体信号传导

• 批准号: 7553576
• 负责人: JEFFREY R KIRSCH
• 金额: $ 23.29万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7553576
• 关键词: BCL2 gene /protein; G protein; apoptosis; artery occlusion; autoradiography; biological signal transduction; brain disorder chemotherapy; brain injury; cerebral ischemia /hypoxia; dehydroepiandrosterone; drug receptors; enzyme linked immunosorbent assay; excitatory aminoacid; gene expression; in situ hybridization; laboratory rat; microdialysis; neuroprotectants; nitric oxide synthase; piperidine; radioimmunoassay; reperfusion; terminal nick end labeling; western blottings

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.

在过去的五年中，我们已经证明，sigma1 受体的药理激活可以极大地改善短暂性局灶性缺血后脑损伤的自然过程。此外，众所周知，衰老引起的神经系统恶化可能至少部分是由于已知是 sigma1 受体激动剂的内源性激素（例如 DHEA）的自然减少造成的。我们之前的工作表明，系统管理 sigma1 受体激动剂可以改善实验性中风的结果，即使这些药物是在再灌注开始后施用的。此外，我们还证明 sigma1 受体激动剂会干扰缺血性脑损伤的主要机制（NMDA 受体介导的 NO 毒性）。当前提案的总体目标是检验 sigma1 受体激动剂通过作用于 sigma1 受体并干扰脑损伤的特定并行机制而引起神经保护的假设。目标 1 将使用细胞培养技术来确定 sigma1 受体激动剂干扰 NMDA 诱导的 NO 产生的机制。待检验的假设是原型 sigma1 受体激动剂 PPBP 间接损害 NMDA 与其受体的结合，并且不会直接影响 信号转导途径的后续步骤。无论确切的作用位点如何，由于一些 sigma1 受体激动剂已被证明通过 G 蛋白机制发挥作用，目标 2 将描述 G 蛋白在基础和缺血后 sigma1 受体信号传导机制中的作用。假设 PPBP 损害 NMDA 刺激 NOS 活性通过涉及 G 蛋白的机制进行。作为平行途径，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，目标 3 将检验以下假设：PPBP 给药与缺血性边界区 bcl-2 和 bcl-x-1 增加以及 bax 表达减少相关。目标 4 将评估已知为 sigma1 受体激动剂的内源性激素的治疗​​效果。我们将检验这样的假设：短暂性局灶性缺血后 DHEA 的治疗功效与 NO 产生减少有关，并且可以被特定的 sigma1 受体拮抗剂阻断。目标 5 旨在确定再灌注时给予 sigma1 受体激动剂时的保护机制。我们将检验以下假设：局灶性缺血再灌注期间延迟给予 PPBP 与 iNOS 表达减少相关，而这一机制可通过 sigma1 受体拮抗剂的给药来阻断。