The Role of KCa3.1 in Neuroinflammation in Alzheimer Disease

描述（由申请人提供）：阿尔茨海默病（AD）是老年人痴呆症的最常见原因。为了应对阿尔茨海默病带来的公共卫生挑战，国家阿尔茨海默病项目法案设定的目标是到2025年预防或治疗阿尔茨海默病。因此，目前迫切需要发现新的治疗靶点并开发相应的化合物。一种沉积在阿尔茨海默病大脑中的蛋白被认为在阿尔茨海默病的发病机制中起关键作用。Abeta可以激活小胶质细胞清除Abeta，但同时也刺激小胶质细胞释放细胞毒性物质，导致神经元损伤。利用本课题组合成的小分子TRAM-34作为药理学工具，我们最近证明了钙活化的钾通道KCa3.1在小胶质细胞活化和小胶质细胞神经毒性中起重要作用。体内证据表明，TRAM-34阻断KCa3.1可以抑制小胶质细胞介导的神经元杀伤，而不影响其迁移和吞噬活性。与AD相关，我们的

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is the most common cause of dementia in the elderly. To meet the public health challenge posed by AD, a goal set by the National Alzheimer's Project Act is to prevent or treat AD by 2025. Therefore currently there is an urgent need for new therapeutic target discovery and corresponding compound development. A protein deposited in AD brains called amyloid-beta (Abeta) has been hypothesized to play a critical role in AD pathogenesis. Abeta can activate microglia to clear Abeta but at the same time also stimulate microglia to release cytotoxic substances that cause neuronal damage. Using the small molecule TRAM-34, which was synthesized by our group, as a pharmacological tool we recently demonstrated that the calcium-activated potassium channel KCa3.1 plays an important role in microglia activation and microglial neurotoxicity. In vivo evidence indicates that blockade of KCa3.1 by TRAM-34 can inhibit microglia-mediated neuronal killing without affecting their migration and phagocytotic activities. Relevant to AD, our results suggest that TRAM-34 blocks the neurotoxicity induced by Abeta-activated microglia, but does not inhibit their beneficial function of phagocytosing Abeta. KCa3.1 blockade, therefore, is a potential new approach for the treatment of AD. With the help of this grant we wish to perform proof-of-principle studies to validate KCa3.1 as a novel therapeutic target for reducing microglia-mediated neurotoxicity and microglial dysfunction in Alzheimer's disease (AD), through the following three Specific Aims: Aim-1: Determine the effect of KCa3.1 blockade on Ab-induced microglial activation. We will treat cultured microglia with Abeta aggregates (oligomer and fibril) and evaluate the effect of KCa3.1 blockade by TRAM-34 treatment (Aim-1a) or genetic knockout (Aim-1b) on chemotactic and phagocytotic activities, signaling pathways, and the production of chemokines, cytokines, reactive oxygen species, and nitric oxide. Aim-2: Assess the contribution of KCa3.1 to AD-like pathology and cognitive deficits seen in the APPswe/PS1dE9 (APP-PS1) model using the genetic knockout approach. We will cross-breed APP-PS1 mice with KCa3.1-/- mice and evaluate whether KCa3.1 reduction affects neuropathological and behavioral abnormalities in APP-PS1 mice. We will further determine if KCa3.1 reduction can alleviate microglial dysfunction seen in APP-PS1 mice. Aim-3: Validate KCa3.1 as a therapeutic target for AD by performing preclinical studies with TRAM-34. We will determine if a 2-month course of TRAM-34, a selective inhibitor of KCa3.1, administered to APP-PS1 mice will reduce neuroinflammation, alleviate microglial dysfunction, and improve the neuropathological and behavioral outcomes of APP-PS1 mice. Because KCa3.1 blockade is relatively safe, our preclinical studies will have translational significance for future developmen of drugs for treating individuals with mild cognitive impairment or AD through inhibition of detrimental microglia functions.