Abnormal Mitochondrial Dynamics and Mitochondrial Dysfunction in Alzheimer's Dise

描述(申请人提供)：多条证据表明线粒体功能障碍在阿尔茨海默病的发病机制中起着关键作用；然而，其潜在的分子机制及其在阿尔茨海默病发病中的作用尚不清楚。线粒体是不断分裂和融合的动态细胞器。我们最近的体外研究表明，线粒体动力学异常可能是AD患者线粒体功能障碍和突触/神经元功能障碍的原因之一。在这些研究的基础上，我们假设线粒体分裂/融合的平衡受损在AD的发病机制中起着关键作用，导致线粒体过度碎裂和重新分布，并导致线粒体超微结构缺陷和功能障碍，从而对神经元功能产生不利影响，包括AD的突触功能障碍和认知/行为障碍。然而，由于体外细胞培养模型的限制，由于AD或APP小鼠线粒体肿胀可能表现出大小和/或长度增加，因此仍有待确定是体内发生的线粒体碎裂还是延长。此外，线粒体动力学异常是否与体内APP小鼠的线粒体/突触功能障碍和认知障碍有关还有待确定。我们的初步结果显示，在3个月大的CRND8 APP转基因小鼠的海马区，线粒体功能障碍，线粒体碎裂，线粒体分裂/融合蛋白表达减少，这表明在疾病过程的早期，线粒体动力学发生了改变。更重要的是，我们能够通过在海马区过度表达Mfn2来促进体内线粒体的融合，这使我们能够解决体内知识中的这些关键缺口。因此，我们建议将这些Mfn2小鼠与CRND8 APP转基因小鼠杂交，并确定线粒体动力学正常化将如何影响CRND8小鼠的线粒体功能、神经元/突触功能障碍和病理/行为/认知缺陷。本研究的目的是在APP小鼠模型中获得线粒体断裂或延长的确切答案，并确定线粒体动力学在AD小鼠模型中线粒体/神经元功能障碍和认知/行为障碍中的因果作用，这也将为Mfn2定向治疗AD提供概念验证研究。为了补充体内研究，我们将确定异常线粒体动力学在Abeta诱导的线粒体/神经元功能中的因果关系，并进一步探讨Abeta诱导的线粒体动力学变化的潜在机制，以及Mfn2过表达如何拯救Abeta诱导的线粒体缺陷。

DESCRIPTION (provided by applicant): Multiple lines of evidence indicate that mitochondrial dysfunction plays a critical role in the pathogenesis of Alzheimer disease; however, the underlying molecular mechanism and its role in AD pathogenesis remain poorly understood. Mitochondria are dynamic organelles that undergo continuous fission and fusion. Our recent in vitro studies suggest that abnormal mitochondrial dynamics likely contributes to mitochondrial dysfunction and synaptic/neuronal dysfunction in AD. Based on these studies, we hypothesized that impaired balance in mitochondrial fission/fusion plays a critical role in the pathogenesis of AD by causing excessive mitochondrial fragmentation and redistribution as well as causes mitochondrial ultrastructural defects and dysfunction which in turn adversely affects neuronal functions including synaptic dysfunction and cognitive/behavioral deficits in AD. However, due to the limitation of in vitro cell culture models, it remains to be determined whether it is mitochondrial fragmentation or elongation that occurs in vivo since swollen mitochondrial in AD or APP mice may demonstrate increased size and/or length. Moreover, it also remains to be determined whether abnormal mitochondrial dynamics is causally involved in mitochondrial/synaptic dysfunction and cognitive deficits in APP mice in vivo. Our preliminary results demonstrated mitochondrial dysfunction, fragmented mitochondria, and decreased expression of mitochondrial fission/fusion proteins in the hippocampus of 3 month-old CRND8 APP transgenic mice, suggesting an altered mitochondrial dynamics early in the disease process. More importantly, we were able to enhance mitochondrial fusion in vivo by overexpressing Mfn2 expression in hippocampus, which enables us to address these critical gaps in our knowledge in vivo. Therefore, we propose to cross these Mfn2 mice with CRND8 APP transgenic mice and determine how normalization of mitochondrial dynamics will affect mitochondrial function, and neuronal/synaptic dysfunction and pathological/behavioral/cognitive deficits in CRND8 mice. The goal is to obtain a definite answer on the involvement of mitochondrial fragmentation or elongation in APP mice and to determine the causal role of mitochondrial dynamics in mitochondrial/neuronal dysfunction and cognitive/behavioral deficits in AD mouse models, which will also serve as a proof-of-concept study for Mfn2-directed therapy for AD. To complement the in vivo studies, we will determine the causal involvement of abnormal mitochondrial dynamics in Abeta-induced mitochondrial/neuronal function and further pursue mechanisms underlying Abeta-induced changes in mitochondrial dynamics and how Mfn2 overexpression rescues Abeta-induced mitochondrial deficits.