Sigma Receptor Signaling in Focal Ischemia

在过去的五年中，我们已经证明，Sigma1受体的药理激活极大地改善了短暂性局灶性脑缺血后脑损伤的自然过程。此外，众所周知，衰老导致的神经退化可能至少部分是由于已知为sigma1受体激动剂的内源性激素(如DHEA)的自然减少所致。我们之前的工作表明，系统管理 Sigma1受体激动剂的使用可改善实验性卒中的预后，即使这些药物是在再灌注开始后使用的。此外，我们还证明了Sigma1受体激动剂干扰了缺血性脑损伤的一个主要机制(NMDA受体介导的NO毒性)。目前提案的总体目标是验证Sigma1受体激动剂通过作用于Sigma1受体并干扰特定的平行脑损伤机制而导致神经保护的假设。目的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。需要检验的假设是，典型的Sigma1受体激动剂PPBP间接损害NMDA与其受体的结合，并且不对 信号转导途径中的后续步骤。无论作用的确切部位如何，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，Aim 2将描述G-蛋白在基础和缺血后Sigma1受体信号机制中的作用。假设是PPBP削弱了NMDA刺激 通过一种涉及G蛋白的机制来激活一氧化氮合酶。作为一个平行途径，我们还将评估全身应用PPBP是否会影响细胞凋亡的发生。为此，目标3将验证PPBP治疗与缺血交界区bcl2和bclx-1增加以及bax表达减少有关的假设。目的4将评估已知为Sigma1受体激动剂的内源性激素的治疗效果。我们将验证这样一种假设，即DHEA对短暂性局灶性脑缺血的治疗效果与NO的减少有关，并可被特定的Sigma1受体拮抗剂阻断。目的5旨在确定在再灌流时给予Sigma1受体激动剂的保护机制。我们将验证这一假设，即局灶性缺血再灌注期间延迟给予PPBP与iNOS表达减少有关，这一机制可被Sigma1受体拮抗剂阻断。

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.