Failure of the glutamate uptake-ascorbic acid exchange drives seizure susceptibility and severity

谷氨酸吸收-抗坏血酸交换的失败会导致癫痫发作的易感性和严重程度

• 批准号: 10179345
• 负责人: JAMES M. MAY
• 金额: --
• 依托单位: VETERANS HEALTH ADMINISTRATION
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2022-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10179345
• 关键词: Acute; Aging; Agonist; Alzheimer' s Disease; Alzheimer' s disease model; Amyloid beta-Protein; Animal Model; Animals; Antioxidants; Ascorbic Acid; Astrocytes; Atherosclerosis; Behavioral; Blood; Brain; Caregivers; Ceftriaxone; Cell Death; Chronic; Clinical; Coculture Techniques; Cognitive; Coupled; Culture Media; Culture Techniques; DNA Sequence Alteration; Data; Deterioration; Diabetes Mellitus; Disease; Dose; Elderly; Electroencephalography; Ensure; Epilepsy; Equilibrium; Event; Exposure to; Extracellular Fluid; Failure; Glutamates; Goals; Gulo; Health; Home; Human; Impaired cognition; Intake; Investigation; Kainic Acid; Lead; Liver; Measures; Messenger RNA; Mitochondria; Modeling; Modification; Mus; Mutation; Nerve Degeneration; Neurons; Oxidative Stress; Oxidative Stress Pathway; Pathogenesis; Pathologic; Pathway interactions; Pattern; Pharmacology; Phenotype; Population; Predisposition; Prevalence; Prevention strategy; Process; Production; Prognosis; Property; Proteins; Quality of life; Reactive Oxygen Species; Rodent; Rodent Model; Role; Seizures; Severities; Signal Transduction; Smoking; Speed; Supplementation; Synapses; System; Telemetry; Testing; Toxic effect; Traumatic Brain Injury; Up-Regulation; Veterans; Wireless Technology; abeta accumulation; ascorbate; brain tissue; care costs; clinically relevant; cognitive ability; cognitive function; comorbidity; dietary; excitotoxicity; experimental study; familial Alzheimer disease; family burden; functional outcomes; improved; military veteran; mouse model; neuronal survival; neuropathology; neurotoxic; novel; oxidative damage; patient population; presenilin-1; preservation; relating to nervous system; synaptic failure; tau Proteins; therapeutic target; treatment planning; uptake

Co-occurrence of seizures with Alzheimer's disease dramatically alters prognosis, and speeds cognitive de- cline. Even mild seizures that may go undetected by caregivers can increase Alzheimer's disease pathogene- sis and also independently lead to neurodegeneration and cognitive dysfunction. Subclinical (non-scorbutic) vitamin C (ascorbate) deficiency is widespread in the USA, particularly among the elderly, and veteran popula- tions where smoking and oxidative stress-related diseases such as atherosclerosis and diabetes are common. A critical, but understudied, mechanism of neuronal protection during excitatory signaling is the glutamate up- take-ascorbate release exchange in astrocytes. As glutamate is taken up into perisynaptic astrocytes via GLT- 1, ascorbate is released into the extracellular fluid providing acute protection against oxidative damage. If GLT- 1 transporter function is compromised by oxidative damage, or if insufficient ascorbate is available for release, then this protection is diminished and the neurotoxic effects of prolonged glutamate exposure are magnified. Recent data support the role of ascorbate treatments in mitigating the effects of seizures, but previous re- search has been critically limited by the use of rodent models that synthesize ascorbate and thus cannot be- come deficient. Decreased brain ascorbate, at levels relevant to human deficiency, is achieved in mice by ge- netic modification of the ability to synthesize ascorbate in liver (Gulo-/-) combined with differential ascorbate supplementation. These mice can also be crossed with the APP/PSEN1 mouse model of Alzheimer's disease to model dietary insufficiency in combination with a disease in which co-occurrence of seizures is common. Specific Aim 1) Demonstrate the role of ascorbate in supporting glutamate clearance by cultured astrocytes. Using cultured astrocytes from both mice and humans we will investigate how conditions that alter the oxida- tive balance of the culture media (e.g. ascorbate and β-amyloid) determine the properties of GLT-1 in gluta- mate uptake. We will also test how altered glutamate clearance under these situations impacts neuronal sur- vival using co-culture techniques and measuring survival and dendritic branching of primary cultured neurons following exposure to glutamate. These experiments will provide direct support for the importance of the gluta- mate-ascorbate exchange mechanism in supporting neuronal health and protecting against glutamate toxicity. Specific Aim 2) Determine relationship between low brain ascorbate conditions and susceptibility to spontane- ous and pharmacologically-induced seizures. We will record neuronal hyper excitability and measure seizure events through electroencephalography (EEG) under baseline conditions and following seizure induction using kainic acid. Such studies have not previously been conducted in low ascorbate conditions owing to lack of widespread access to appropriate models. We will use an implantable telemetry (wireless) system that allows long-term measuring of EEG in animals within their home cages. This is a significant advance on more tradi- tional `tethered' EEG systems. We will also determine the extent to which repeated exposures to glutamatergic agonists, even without a clear behavioral (seizure) correlate, can negatively impact both cognitive ability, and β-amyloid production in the APP/PSEN1 mice to explore the functional outcome of seizures in an Alzheimer's disease model in addition to wild-type and Gulo-/- mice. Specific Aim 3) Establish the extent to which upregulation of GLT-1 improves glutamate clearance and de- creases detrimental effects of kainic acid treatments. GLT-1, and therefore glutamate clearance, represents a targetable strategy to reduce the extent of neural damage following hyperexcitability, or seizure events. We will investigate a compound, ceftriaxone, known to up-regulate GLT-1 expression, and assess its ability to de- crease seizure susceptibility and severity. Our long-term goal is to show that protecting glutamate uptake and avoiding ascorbate deficiency can minimize effects of seizure in specific populations, and provide a cheap pre- ventative strategy against cognitive decline.

癫痫发作与阿尔茨海默病的同时发生会极大地改变预后，并加速认知能力的丧失。 克莱恩。即使护理人员可能未发现的轻微癫痫发作也会增加阿尔茨海默氏病的病原体。 sis 也独立导致神经退行性变和认知功能障碍。亚临床（非坏血病） 维生素 C（抗坏血酸）缺乏症在美国很普遍，尤其是老年人和退伍军人。 吸烟和氧化应激相关疾病（如动脉粥样硬化和糖尿病）很常见。 兴奋信号传导期间神经元保护的一个关键但尚未充分研究的机制是谷氨酸上调 星形胶质细胞中的抗坏血酸释放交换。由于谷氨酸通过 GLT- 被吸收到突触周围星形胶质细胞中 1、抗坏血酸被释放到细胞外液中，提供针对氧化损伤的急性保护。如果 GLT- 1 转运蛋白功能因氧化损伤而受损，或者如果抗坏血酸可供释放不足， 那么这种保护作用就会减弱，而长期接触谷氨酸的神经毒性作用就会放大。 最近的数据支持抗坏血酸治疗在减轻癫痫发作影响方面的作用，但之前的研究 由于使用合成抗坏血酸的啮齿动物模型，搜索受到严重限制，因此无法- 来不足。通过基因组在小鼠体内实现了将大脑抗坏血酸降低到与人类缺乏相关的水平。 肝脏合成抗坏血酸能力的网络修饰（Gulo-/-）与差异抗坏血酸相结合 补充。这些小鼠还可以与阿尔茨海默病的 APP/PSEN1 小鼠模型杂交 建立饮食不足与癫痫发作常见疾病相结合的模型。 具体目标 1) 证明抗坏血酸在支持培养的星形胶质细胞清除谷氨酸方面的作用。 使用来自小鼠和人类的培养星形胶质细胞，我们将研究如何改变氧化的条件 培养基的活性平衡（例如抗坏血酸和 β-淀粉样蛋白）决定了 GLT-1 在谷氨酸中的特性。 伴侣吸收。我们还将测试在这些情况下改变的谷氨酸清除率如何影响神经元表面 vival 使用共培养技术并测量原代培养神经元的存活和树突分支 接触谷氨酸后。这些实验将为谷氨酸的重要性提供直接支持。 伴侣-抗坏血酸交换机制支持神经元健康并防止谷氨酸毒性。 具体目标 2) 确定低脑抗坏血酸状况与自发性易感性之间的关系 自然和药物引起的癫痫发作。我们将记录神经元过度兴奋并测量癫痫发作 在基线条件下和癫痫发作诱导后通过脑电图 (EEG) 记录事件 红藻氨酸。由于缺乏抗坏血酸水平，此类研究以前并未在低抗坏血酸条件下进行过。 广泛获得适当的模型。我们将使用植入式遥测（无线）系统，该系统允许 长期测量家中笼子内动物的脑电图。这是更多传统技术的重大进步 和“系留”脑电图系统。我们还将确定重复暴露于谷氨酸的程度 激动剂，即使没有明确的行为（癫痫发作）相关性，也会对认知能力和认知能力产生负面影响。 APP/PSEN1 小鼠中 β-淀粉样蛋白的产生，探索阿尔茨海默病癫痫发作的功能结果 除了野生型和 Gulo-/- 小鼠外，还建立了疾病模型。 具体目标 3) 确定 GLT-1 的上调改善谷氨酸清除和去-的程度 增加红藻氨酸治疗的有害影响。 GLT-1，以及谷氨酸清除率，代表 有针对性的策略，以减少过度兴奋或癫痫事件后的神经损伤程度。我们将 研究一种已知可上调 GLT-1 表达的化合物头孢曲松，并评估其去- 折痕癫痫发作​​的易感性和严重程度。我们的长期目标是证明保护谷氨酸的吸收和 避免抗坏血酸缺乏可以最大限度地减少特定人群癫痫发作的影响，并提供廉价的预防措施 对抗认知能力下降的发泄策略。