SK2 Channels as Novel Neuroprotective Targets Against Cerebral Ischemia

SK2 通道作为抗脑缺血的新型神经保护靶点

• 批准号: 8074360
• 负责人: JOHN P ADELMAN
• 金额: $ 32.7万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8074360
• 关键词: Adverse effects; Area; Attenuated; Brain; Brain Injuries; Brain Ischemia; Calcium-Activated Potassium Channel; Cardiopulmonary Resuscitation; Cause of Death; Cell Death; Cerebral Ischemia; Cessation of life; Chemosensitization; Clinical Trials; Cognitive; Cyclic AMP-Dependent Protein Kinases; Dose; Electrophysiology (science); Endocytosis; Excitatory Amino Acid Antagonists; Excitatory Postsynaptic Potentials; Frequencies; Genetic; Glutamate Receptor; Glutamates; Health; Heart; Heart Arrest; Hippocampus (Brain); Human; Image; Immune; Immunoelectron Microscopy; Impaired cognition; Intervention; Ischemia; Learning; Long-Term Effects; Long-Term Potentiation; Measures; Mediating; Memory; Memory impairment; Modification; Mus; Myocardial Infarction; N-Methylaspartate; Neurological outcome; Neurons; Outcome; Pattern; Performance; Pharmaceutical Preparations; Phosphorylation; Physiological; Positioning Attribute; Quality of life; Research; Role; Slice; Stimulus; Stroke; Synapses; Synaptic plasticity; Testing; Therapeutic; Time; United States; Update; Vertebral column; disability; excitotoxicity; improved; in vivo; mouse model; neuronal survival; neuroprotection; neurotransmission; novel; postsynaptic; prevent; response; therapeutic target; transmission process; two-photon

DESCRIPTION (provided by applicant): Cardiac arrest/cardiopulmonary resuscitation (CA/CPR) causes ischemia, neuronal excitotoxicity and cognitive decline. Despite intensive efforts, outcome remains poor. Excitotoxicity results from increased glutamate neurotransmission, and the consequent excessive Ca2+ influx through NMDA-type glutamate receptors (NMDAr). Hippocampal CA1 neurons are important to learning and memory and are acutely sensitive to excitotoxicity. We have shown that small conductance Ca2+-activated K+ channels, type 2 (SK2 channels) are expressed together with NMDAr in the spines on hippocampal CA1 neurons where they act to attenuate Ca2+ influx through NMDAr. In addition, SK2 channels are removed from synapses following patterned activity, either normally as for the induction of long term potentiation (LTP), or abnormally after CA/CPR. The loss of synaptic SK2 channels removes the SK channel 'brake' on Ca2+ influx through NMDAr and is due to protein kinase A phosphorylation of the SK2 channels. Our results further show that increasing SK2 channel activity substantially improves neuronal survival after CA/CPR. Therefore, we will use an integrated technical repertoire to test these specific hypotheses: 1. Genetic or pharmacologic enhancement of SK2 channel activity protects CA1 neurons and improves cognitive outcome. We will use genetic mouse models and SK enhancing drugs to determine the i) survival of CA1 neurons and, ii) cognitive performance. 2. CA/CPR-induced ischemia causes a delayed and prolonged loss of synaptic SK2 channels in CA1 neurons, increasing the NMDAr-dependent Ca2+ transient that causes excitotoxicity. Preserving synaptic SK2 channel activity after CA/CPR protects CA1 neurons. We will measure the time course and effects of ischemia on the SK2 and NMDAr contributions to glutamate transmission (EPSP), and NMDAr-mediated Ca2+ transients. 3. CA/CPR-induced ischemia causes PKA phosphorylation of spine SK2 channels, inducing channel endocytosis. Expression of PKA-immune SK2 channels will normalize the SK2 and NMDAr contributions to the EPSP, the NMDAr-dependent Ca2+ transient, and protect CA1 neurons from excitotoxic cell death. We will use control mice or mice expressing PKA-immune SK2 channels to determine: i) the sub-spine distribution of SK2 channels; ii) the SK2 and NMDAr contributions to the EPSP; iii) the spine Ca2+ transient; iv) CA1 viability. 4. The aberrantly sustained ischemia-induced loss of synaptic SK2 channels results in ischemic LTP (iLTP) that shifts ?m, the modification threshold, to higher stimulus frequencies and impairs further potentiation. Maintained expression of functional synaptic SK2 channels prevents iLTP and normalizes ?m. We will measure the long-term effects of CA/CPR-induced ischemia on synaptic plasticity. PUBLIC HEALTH RELEVANCE: Heart attack and the consequent cerebral ischemia is one of the leading causes of death and disability in the United States and, unfortunately, there are currently no drugs available that improve outcome following severe heart attack requiring cardio-pulmonary resuscitation. SK2 channels, one type of Ca2+- activated K+ channel, are anatomically and functionally poised to ameliorate brain damage following stroke. The proposed studies will demonstrate the neuroprotective role of SK2 channels and suggest novel interventional strategies to protect the brain following heart attack, improving survival, diminishing memory deficits, and improving quality of life.

描述（由申请人提供）：心脏骤停/心肺复苏（CA/CPR）会导致缺血、神经元兴奋性毒性和认知能力下降。尽管付出了巨大的努力，但结果仍然不佳。兴奋性毒性是由于谷氨酸神经传递增加以及随之而来的过量 Ca2+ 通过 NMDA 型谷氨酸受体 (NMDAr) 流入造成的。海马 CA1 神经元对于学习和记忆很重要，并且对兴奋性毒性非常敏感。我们已经证明，小电导 Ca2+ 激活的 K+ 通道 2 型（SK2 通道）与海马 CA1 神经元棘中的 NMDAr 一起表达，它们通过 NMDAr 减弱 Ca2+ 流入。此外，SK2 通道在模式化活动后从突触中移除，通常是为了诱导长时程增强 (LTP)，或者是在 CA/CPR 后异常。突触 SK2 通道的丧失消除了 SK 通道对通过 NMDA 的 Ca2+ 流入的“制动”，这是由于 SK2 通道的蛋白激酶 A 磷酸化所致。我们的结果进一步表明，增加 SK2 通道活性可显着提高 CA/CPR 后神经元的存活率。因此，我们将使用综合技术来测试这些具体假设： 1. SK2 通道活性的遗传或药理学增强可保护 CA1 神经元并改善认知结果。我们将使用遗传小鼠模型和 SK 增强药物来确定 i) CA1 神经元的存活和 ii) 认知表现。 2. CA/CPR 诱导的缺血导致 CA1 神经元中突触 SK2 通道延迟且长期丧失，增加了导致兴奋性毒性的 NMDAr 依赖性 Ca2+ 瞬变。 CA/CPR 后保留突触 SK2 通道活性可保护 CA1 神经元。我们将测量缺血对 SK2 和 NMDAr 对谷氨酸传输 (EPSP) 贡献的时间进程和影响，以及 NMDAr 介导的 Ca2+ 瞬变。 3. CA/CPR诱导的缺血导致脊柱SK2通道的PKA磷酸化，诱导通道内吞作用。 PKA 免疫 SK2 通道的表达将使 SK2 和 NMDAr 对 EPSP（NMDAr 依赖性 Ca2+ 瞬态）的贡献正常化，并保护 CA1 神经元免受兴奋性毒性细胞死亡。我们将使用对照小鼠或表达 PKA 免疫 SK2 通道的小鼠来确定： i) SK2 通道的亚脊柱分布； ii) SK2 和 NMDAR 对 EPSP 的贡献； iii) 脊柱Ca2+瞬态； iv) CA1 活力。 4. 异常持续的缺血引起的突触 SK2 通道丧失导致缺血性 LTP (iLTP)，其将修改阈值 ?m 转变为更高的刺激频率并损害进一步的增强。功能性突触 SK2 通道的维持表达可预防 iLTP 并使 ?m 正常化。我们将测量 CA/CPR 诱导的缺血对突触可塑性的长期影响。公共卫生相关性：心脏病发作和随之而来的脑缺血是美国死亡和残疾的主要原因之一，不幸的是，目前没有药物可以改善需要心肺复苏的严重心脏病发作后的预后。 SK2 通道是 Ca2+ 激活的 K+ 通道的一种，在解剖学和功能上都可以改善中风后的脑损伤。拟议的研究将证明 SK2 通道的神经保护作用，并提出新的干预策略来保护心脏病发作后的大脑、提高生存率、减少记忆缺陷并提高生活质量。