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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

基本信息

批准号：
10683056
负责人：
JAMES M. MAY
金额：
--
依托单位：
VETERANS HEALTH ADMINISTRATION
依托单位国家：
美国
项目类别：
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/10683056
关键词：
Acute Aging Agonist Alzheimer&apos s Disease Alzheimer&apos 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 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 wireless

项目摘要

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共同发生极大地改变了预后，并加速了认知能力的下降。渐变群即使是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病致病基因- 并独立地导致神经变性和认知功能障碍。亚临床（非坏血病）维生素C（抗坏血酸）缺乏症在美国很普遍，特别是在老年人和退伍军人中，吸烟和氧化应激相关疾病如动脉粥样硬化和糖尿病是常见的。兴奋性信号传导过程中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，摄取-抗坏血酸释放交换星形胶质细胞。当谷氨酸通过GLT被摄取到突触周围的星形胶质细胞中时， 1，抗坏血酸盐被释放到细胞外液中，提供急性保护免受氧化损伤。如果GLT- 1转运蛋白功能受到氧化损伤的损害，或者如果可用于释放的抗坏血酸盐不足，那么这种保护作用就会减弱，长期暴露于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，但以前的研究表明，研究受到了合成抗坏血酸的啮齿动物模型的严重限制，因此不能- 来不足。降低脑抗坏血酸，在相关水平的人类缺乏，是实现在小鼠的ge- 肝脏合成抗坏血酸盐能力的遗传修饰（Gulo-/-）与差异抗坏血酸盐组合补充。这些小鼠也可以与阿尔茨海默病的APP/PSEN 1小鼠模型杂交以模拟饮食不足与癫痫发作常见的疾病的组合。具体目的1）证明抗坏血酸在支持培养的星形胶质细胞清除谷氨酸中的作用。使用培养的小鼠和人类星形胶质细胞，我们将研究如何改变氧化应激的条件，培养基（例如抗坏血酸盐和β-淀粉样蛋白）的动态平衡决定了GLT-1在谷氨酰胺中的性质。配偶摄取我们还将测试在这些情况下改变谷氨酸清除率如何影响神经元表面，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暴露在谷氨酸盐中。这些实验将为gluta的重要性提供直接支持- 在支持神经元健康和保护免受谷氨酸毒性中的配偶-抗坏血酸交换机制。具体目标2）确定低脑抗坏血酸条件和对spontane的易感性之间的关系- 癫痫和药物诱发的癫痫。我们将记录神经元的超兴奋性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）检测的事件，红藻氨酸这些研究以前没有在低抗坏血酸盐条件下进行过，广泛使用适当的模型。我们将使用植入式遥测（无线）系统，长期测量动物在其饲养笼内的EEG。这是一个重大的进步，对更多的传统- 传统的“拴系”EEG系统。我们还将确定重复暴露于放射性物质的程度激动剂，即使没有明确的行为（癫痫发作）相关，也会对认知能力和 APP/PSEN 1小鼠中β-淀粉样蛋白的产生，以探索阿尔茨海默病患者癫痫发作的功能结局疾病模型以及野生型和Gulo-/-小鼠。具体目的3）确定GLT-1的上调改善谷氨酸清除和去磷酸化的程度。增加了红藻氨酸处理的有害作用。GLT-1，因此谷氨酸清除率，代表有针对性的策略，以减少过度兴奋或癫痫发作事件后神经损伤的程度。我们将研究已知可上调GLT-1表达的化合物头孢曲松，并评估其去癫痫发作的易感性和严重性。我们的长期目标是证明保护谷氨酸摄取和避免抗坏血酸缺乏可以最大限度地减少癫痫发作对特定人群的影响，并提供一种廉价的预防措施，对抗认知能力下降的冒险策略