A Delta GABA Receptor as a Target for Essential Tremor Therapy

Delta GABA 受体作为特发性震颤治疗的靶点

• 批准号: 9495274
• 负责人: Charles Adrian Handforth
• 金额: --
• 依托单位: VA GREATER LOS ANGELES HEALTHCARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-03-01 至 2018-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9495274
• 关键词: Affect; Age; Alcohols; American; Animal Model; Behavior; Brain; Brain Mapping; Breeding; Calcium; Cells; Cerebellar Nuclei; Cerebellar cortex structure; Cerebellum; Clinical Trials; Data; Development; Disabled Persons; Dose; Essential Tremor; Ethanol; Exons; Formulation; GABA Receptor; General Population; Genes; Goals; Guidelines; Harmaline; Human; Impairment; In Vitro; Inferior; Intention Tremor; Knock-out; Knockout Mice; Laboratory Research; Lead; Measures; Mediating; Modeling; Molecular Target; Motion; Mus; Muscimol; Occupational; Occupations; Olives - dietary; Patients; Persons; Pharmaceutical Preparations; Pharmacotherapy; Prevalence; Receptor Activation; Recommendation; Reporting; Retirement; Role; Sedation procedure; Slice; Specificity; Testing; Tremor; Upper Extremity; Veterans; Wild Type Mouse; Wine; Withdrawal; Work; alcohol effect; base; delta opioid receptor; design; digital; disability; drug development; experimental study; gamma-Aminobutyric Acid; ganaxolone; granule cell; interest; motor impairment; nervous system disorder; neurosteroids; prevent; programs; promoter; public health relevance; receptor; social; therapy development

DESCRIPTION (provided by applicant): Essential tremor affects 0.5-0.9% of the general population and about 4.5% of those above age 65. Medications for tremor are re-purposed drugs found empirically rather than through laboratory research. As such they lack potency and specificity, and are often not well tolerated. In our program we seek to identify molecular targets to which anti-tremor drugs could be designed, offering greater on-target specificity and potency. A clue is that patients often report that as little as 1-2 glasses of wine can suppress tremor. Brain mapping studies in essential tremor indicate that hyper-oscillatory activity within circuits of the cerebellum underlies tremor. When patients are given low doses of alcohol, not only does the tremor diminish, but excessive activity in the cerebellar cortex also diminishes. We postulate that low-dose alcohol works on tremor by activating GABAA receptors that contain alpha6, beta3 and delta subunits, found only in the cerebellar cortex. If we can show that this receptor can mediate tremor suppression, it could represent an important target for anti-tremor therapy. The GABAA receptor is a pentamer made of alpha, beta, and either gamma or delta subunits. Delta GABAA receptors exert tonic inhibition, and are much more sensitive to GABA. Studies with receptors expressed in cells, and with brain slices, have shown that THIP, muscimol and neurosteroids such as ganaxolone selectively activate delta GABAA receptors rather than gamma GABAA receptors. In addition, ethanol in the range of 1-2 glasses of wine has been found to activate those delta GABAA receptors that use beta3 subunits. We hypothesize that activation of delta GABAA receptors by THIP, muscimol, ganaxolone, and low-dose alcohol will suppress tremor in the harmaline model of essential tremor in wild-type but not littermate delta knockout mice. In addition, the tremor-suppressing effect of alcohol in wild-type mice should be reversed by the alcohol antagonist Ro15-4513, providing further evidence that alcohol is suppressing tremor via a GABAA receptor. We use the harmaline tremor model, which has many similarities to tremor of essential tremor. Motion power is digitally analyzed to provide measures of motion in the tremor bandwidth as a ratio of overall motion power. Our pilot data indicate that THIP, muscimol, ganaxolone, and low-dose alcohol all suppress harmaline tremor in wild-type but not in delta knockout mice. The effect of low-dose alcohol was blocked by Ro15-4513. We propose to replicate these findings (Aim 1). The delta subunit is associated with either alpha 4 or with alpha 6 in GABAA receptors. The alpha4- delta receptors mediate sedation and motor impairment when activated, whereas no behavior has previously been found associated with alpha6-delta receptor activation. Our pilot experiments showed that THIP and low-dose alcohol suppress harmaline tremor in wild-type but not in alpha6 knockout mice, indicating the alpha6-delta receptor mediates tremor suppression. We propose to replicate this finding and test ganaxolone as well (Aim 2). GABAA receptors containing alpha6-delta are found only in the cerebellar cortex, where they associate with beta3, beta2 or beta1. The next step is to investigate whether cerebellar beta3 is important for tremor suppression by these delta-receptor acting drugs by breeding mice with beta3 missing in the part of the cerebellum where alpha6 is expressed (Aim 3). It is anticipated that beta3 will be critical for low-dose alcohol's anti-tremor action, but itmay not be critical for THIP or ganaxolone. Should appropriate strains of knockout mice become available, we will test whether beta2 or beta1 are important for mediating the anti-tremor action of THIP and ganaxolone. These experiments are expected to lead to the identification of a GABAA receptor subtype, alpha6-beta2/3- delta, found only in the cerebellar cortex that will constitute a molecular target to which anti-tremor therapies can be designed to activate. Such a therapy, through its high selectivity, is anticipated to be potent and well tolerated. As the first drug to be developed specifically for essential tremor from laboratory research, it would be expected to confer greater efficacy than existing drugs, preventing disability and loss of occupation in veterans with essential tremor.

描述（由申请人提供）： 基本震颤影响了0.5-0.9％的普通人群，约为65岁以上的人中约4.5％。震颤的药物是经验上发现的，而不是通过实验室研究发现的药物。因此，它们缺乏效力和特异性，并且通常不太容忍。在我们的计划中，我们试图确定可以设计抗晶状体药物的分子靶标，从而提供更大的目标特异性和效力。一个线索是患者经常报告说，只有1-2杯酒可以抑制震颤。基本震颤中的大脑映射研究表明，小脑回路内的高振荡活性是震颤的基础。 当患者的酒精含量低时，震颤不仅会减少，而且小脑皮层的活动过多也会减少。我们假设低剂量酒精通过激活含有α6，beta3和三角洲亚基的GABAA受体（仅在小脑皮层中发现）来震颤。如果我们可以证明该受体可以介导震颤抑制​​，则可以代表抗移植治疗的重要靶标。 GABAA受体是由Alpha，Beta和Gamma或Delta亚基制成的五聚体。 Delta Gabaa受体会施加补品抑制作用，并且对GABA更加敏感。用在细胞中表达的受体以及脑切片表达的研究表明，thip，麝香酚和神经类似物（例如甘诺酮）选择性地激活Delta Gabaa受体，而不是伽马GABAA受体。此外，已经发现乙醇在1-2杯葡萄酒范围内激活那些使用beta3亚基的Delta Gabaa受体。我们假设通过Thip，Muscimol，Ganaxolone和低剂量酒精激活Delta Gabaa受体会抑制野生型中必需震颤的Harmaline模型中的震颤，但不是同窝式三角洲敲除小鼠。另外，酒精拮抗剂RO15-4513应逆转酒精对野生型小鼠的震颤抑制作用，从而进一步证明酒精正在通过GABAA受体抑制震颤。我们使用Harmaline震颤模型，该模型与必需震颤的震颤具有许多相似之处。对运动功率进行数字分析，以在震颤带宽中提供运动量度作为总体运动功率的比率。我们的飞行员数据表明​​，Thip，Muscimol，Ganaxolone和低剂量酒精都抑制了野生型中的Harmaline Tremor，但在Delta敲除小鼠中却不抑制。低剂量酒精的作用被RO15-4513阻塞。我们建议复制这些发现（AIM 1）。三角洲亚基与Alpha 4或Alpha相关 6在GABAA受体中。激活时α4-三角洲受体会介导镇静和运动障碍，而以前没有发现与α6-DELTA受体激活相关的行为。我们的试点实验表明，thip和低剂量的酒精抑制野生型中的Harmaline震颤，但在Alpha6敲除小鼠中不抑制Harmaline震颤，表明α6-DELTA受体介导了震颤的抑制。我们建议复制这一发现并测试甘诺酮（AIM 2）。只有在小脑皮层中发现了含有α6-戴尔塔的GABAA受体，它们与beta3，beta2或beta1相关。下一步是研究小脑β3对于这些三角肌作用药物抑制震颤是否很重要，通过繁殖小鼠在表达α6的小脑部分中缺少β3的小鼠（AIM 3）。预计Beta3对于低剂量酒精的抗晶状体作用至关重要，但ITMAY对于Thip或Ganaxolone并不是至关重要的。如果适当的敲除小鼠可用，我们将测试beta2或beta1对于介导Thip和Ganaxolone的反营养作用是否重要。这些实验有望导致仅在小脑皮层中发现的GABAA受体亚型Alpha6-Beta2/3-三角洲，该实验将构成一个分子靶标的抗trimor疗法，该靶标可用于激活。通过其高选择性，这种疗法预计将有效且耐受性良好。作为第一个 专门针对实验室研究的基本震颤开发的药物，预计比现有药物具有更大的功效，从而防止残疾和具有必要震颤的退伍军人的职业丧失。