Role of NCKX2 in the activation of toxic Zn2+ influx in ischemic neurons

NCKX2 在激活缺血神经元有毒 Zn2 流入中的作用

• 批准号: 7826946
• 负责人: LECH Kiedrowski
• 金额: $ 19.63万
• 依托单位: UNIVERSITY OF ILLINOIS AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-15 至 2012-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7826946
• 关键词: Acute; Affect; Apoptosis; B-Lymphocytes; Brain; Brain Injuries; Brain Ischemia; Cardiac Surgery procedures; Cardiopulmonary Bypass; Cell Survival; Cells; Cessation of life; Clinical Trials; Cognitive deficits; Cytosol; Data; Development; Drug Design; Event; Future; Glucose; Heterozygote; Hour; Intervention; Ischemic Brain Injury; Knock-out; Knockout Mice; Lead; Link; Mediating; Monitor; Mus; Myocardial Infarction; N-Methylaspartate; NCKX2; Necrosis; Neurons; Neuroprotective Agents; Operative Surgical Procedures; Outcome; Oxygen; Pathway interactions; Pharmaceutical Preparations; Phase; Postoperative Period; Protein Isoforms; Recovery; Reporting; Research; Risk; Role; Safety; Simulate; Stroke; Testing; Time; Vascular blood supply; Work; brain tissue; channel blockers; deprivation; design; disability; extracellular; improved; inhibitor/antagonist; neurotoxic; novel; operation; prevent; public health relevance; research study

DESCRIPTION (provided by applicant): Ischemic brain damage leads to cognitive deficits, long-term disability, and even death. This damage occurs when the blood supply to the brain is arrested, which takes place during cardiac surgeries, stroke, or myocardial infarction. NMDA channel blockers and other drugs designed to protect the brain from ischemic damage have failed in clinical trials. Therefore, the need to identify novel targets for pharmacological intervention during brain ischemia is very urgent. Our preliminary data indicate that we may be able to identify such novel target(s). The toxic phase of brain ischemia is executed at the time when neurons are profoundly depolarized by highly elevated extracellular K+ ([K+]o). This [K+]o elevation is caused by K+ efflux from the cytosol to the extracellular medium and coincides with a reciprocal Na+ influx. As a result, ischemic neurons are depolarized and contain elevated cytosolic Na+. In preliminary work, we simulated such ischemic depolarization in cultured neurons and found that cytosolic [Ca2+] ([Ca2+]c) elevations resulted from an Na-dependent Ca2+ influx that could not be prevented by blocking NMDA channels. Interestingly, the Na-dependent [Ca2+]c elevations activated a pathway of potentially even more neurotoxic Zn2+ influx. The Na-dependent [Ca2+]c elevations in depolarized ischemic neurons are likely mediated by plasmalemmal K-dependent Na+/Ca2+ exchangers, NCKXs. Since NCKX2 is a major NCKX isoform expressed in the brain cortex, we would like to explore the idea that there is a causal link between NCKX2-mediated Ca2+ influx and an activation of Zn2+ influx. To test this idea, we plan to use cultured cortical neurons obtained from wild type and NCKX2 knockout mice. Our project has 2 specific aims and will be completed in 2 years. In Aim 1, we will determine the impact of the NCKX2 knockout on the rate of cytosolic Zn2+ ([Zn2+]c) elevation in ischemic neurons. In Aim 2, we will determine the impact of the NCKX2 knockout and Zn2+ on ischemic neuronal death. If we find that NCKX2 operation is causally linked to the activation of neurotoxic Zn2+ influx in ischemic neurons, our data will provide support for developing inhibitors of Zn2+influx activation by NCKX2. Such agents may become neuroprotective drugs that could be used to improve the safety of cardiac surgeries. PUBLIC HEALTH RELEVANCE: About 32% of the very commonly performed cardiac surgeries involving cardiopulmonary bypass (CPB) cause ischemic events in the brain and carry a significant risk of post-operative cognitive deficits. This project explores the idea that the brain damage relevant to CPB is caused by the abnormal operation of a K- dependent Na+/Ca2+ exchanger that activates a neurotoxic Zn2+ influx. This research may lead to the development of a novel therapy that could be applied prior to CPB surgeries to improve their safety.

描述（由申请人提供）：缺血性脑损伤导致认知缺陷，长期残疾，甚至死亡。这种损害发生在心脏手术、中风或心肌梗死期间，当大脑的血液供应被阻止时。NMDA通道阻滞剂和其他旨在保护大脑免受缺血性损伤的药物在临床试验中失败了。因此，需要确定新的药物干预脑缺血的目标是非常迫切的。我们的初步数据表明，我们可能能够确定这样的新目标。脑缺血的毒性阶段在神经元被高度升高的细胞外K+（[K+]o）深度去极化时执行。这种[K+]o升高是由K+从细胞质流出到细胞外介质引起的，并且与Na+的相互流入相一致。结果，缺血神经元被去极化并含有升高的胞质Na+。在初步工作中，我们模拟了这种缺血性去极化培养的神经元，发现胞浆[Ca 2 +]（[Ca 2 +]c）的升高导致Na依赖性Ca 2+内流，不能阻止阻断NMDA通道。有趣的是，Na依赖性[Ca 2 +]c升高激活了一条潜在的更具神经毒性的Zn 2+内流途径。去极化缺血神经元Na依赖性[Ca ~（2+）]c升高可能由质膜K依赖性Na ~+/Ca ~（2+）交换体（NCKX）介导。由于NCKX 2是在大脑皮层中表达的主要NCKX同种型，因此我们想探索NCKX 2介导的Ca 2+内流和Zn 2+内流激活之间存在因果关系的想法。为了验证这一想法，我们计划使用从野生型和NCKX 2敲除小鼠中获得的培养皮层神经元。我们的项目有两个具体目标，将在2年内完成。在目标1中，我们将确定NCKX 2敲除对缺血神经元中胞质Zn 2+（[Zn 2 +]c）升高速率的影响。在目标2中，我们将确定NCKX 2敲除和Zn 2+对缺血性神经元死亡的影响。如果我们发现NCKX 2操作与缺血神经元中神经毒性Zn 2+内流的激活有因果关系，我们的数据将为开发NCKX 2激活Zn 2+内流的抑制剂提供支持。这些药物可能成为神经保护药物，可用于提高心脏手术的安全性。公共卫生相关性：大约32%的非常常见的涉及心肺转流（CPB）的心脏手术会导致脑缺血事件，并具有术后认知缺陷的显著风险。本项目探讨了与CPB相关的脑损伤是由K依赖性Na+/Ca 2+交换器的异常操作引起的，该交换器激活神经毒性Zn 2+内流。这项研究可能会导致开发一种新的治疗方法，可以在CPB手术前应用，以提高其安全性。