Hippocampal Synaptic Structure

描述(由申请人提供)：这是一个长期项目的重新提交的续签申请，该项目涉及老化过程中海马神经元钙(Ca~(2+))相关过程的失调以及神经元功能/脆弱性改变的后果。该项目最初源于一项发现，即海马锥体神经元动作电位爆发后的钙依赖慢后超极化(SAHP)，老年动物比年轻成年动物更大。重要的是，较大的sAHP与神经元兴奋性降低和学习和记忆受损相关。相反，在学习一项任务的动物身上发现了较小的sAHP。从那时起，我们和其他人已经确定，在老年神经元中，钙离子动作电位、钙瞬变和L型钙电流也会增加。这些结果导致了一种脑老化的钙调节失调假说，其中L通道活性的增加起着关键的启动作用，由此产生的更大的SAHP降低了神经元的兴奋性。兰尼定受体(RyRs)增强的钙诱导钙释放(CICR)调节锥体神经元衰老相关的钙瞬变和sAHP的幅度也已变得明显。这个项目的主要目标是从根本上促进我们对导致不健康大脑衰老的钙离子失调的潜在分子机制的理解。基于我们新的有趣的结果，我们提出了一个新的与年龄相关的钙调节失调的工作假说，该假说表明免疫亲和素，特别是FK-506结合蛋白1b和/或1a(FKBP1b/1a)的下调导致RyR失稳、更大的CICR和更大的sAHP。其结果是神经元兴奋性和行为可塑性受损。这些研究将通过显微注射病毒载体在体内操纵FKBP-钙调节通路中FKBP1b/1a和其他蛋白在海马区的表达/功能。将使用多学科方法在同一动物身上评估多种结果，包括广泛的行为测试、最先进的细胞内电生理学以及伴随的钙成像、免疫组织化学和基因微阵列分析。这些研究应该实质上阐明依赖于钙离子失调的衰老变化，并明确测试FKBPs在衰老过程中钙离子失调和海马区功能中的作用。提出了慢性干预研究，这些研究可能具有直接的翻译相关性，并直接导致针对衰老相关的脑功能下降的新的预防和治疗方法。鉴于老龄化人口的急剧增加，识别和开发此类疗法以维持老年人的认知功能变得越来越重要。 公共卫生相关性： 美国的老龄化人口预计将以惊人的速度增长，这无疑将影响我们的医疗体系(到2030年，20%的人口将达到65岁)。认知功能衰退经常伴随着年龄的增长，根据严重程度的不同，可能会显著影响生活质量。我们的结果表明，在心力衰竭中起主要作用的特定途径(FKBP-钙离子)也可能在脑老化和认知功能下降中发挥关键作用；因此，本项目的目标是利用基因治疗技术来确定这种干预措施是否可以预防或减缓与年龄相关的脑功能衰退的发生。这一结果可能具有实质性的治疗意义。

DESCRIPTION (provided by applicant): This is the resubmission of a renewal application for a longstanding project on dysregulation of calcium (Ca2+)-related processes in hippocampal neurons during aging and the consequences for altered neuronal function/vulnerability. The project initially derived from the finding that the Ca2+-dependent slow afterhyperpolarization (sAHP), that follows a burst of action potentials in hippocampal pyramidal neurons, is larger in aged than in young-adult animals. Importantly, larger sAHPs are correlated with reduced neuronal excitability and impaired learning and memory. Conversely, smaller sAHPs are found in animals that learn a task. Since then, we and others have determined that Ca2+ action potentials, Ca2+ transients and L-type Ca2+ currents also are increased in aged neurons. These results led to a Ca2+ dysregulation hypothesis of brain aging, in which increased activity of L-channels plays a key initiating role and the resulting larger sAHP reduces neuronal excitability. It also has become apparent that enhanced Ca2+-induced Ca2+ release (CICR) from ryanodine receptors (RyRs) modulates the magnitude of aging-related Ca2+ transients and sAHPs in pyramidal neurons. The major objective of this project is to fundamentally advance our understanding of the underlying molecular mechanisms of Ca2+ dysregulation that lead to unhealthy brain aging. Based on our new intriguing results, we have formulated a novel working hypothesis of age-related Ca2+ dysregulation that suggests that downregulation of immunophilins, particularly FK-506 binding protein 1b and/or 1a (FKBP1b/1a), leads to a cascade of RyR destabilization, greater CICR and larger sAHPs. The resulting effect is impaired neuronal excitability and behavioral plasticity. These studies will manipulate hippocampal expression/function of FKBP1b/1a and other proteins in the FKBP- Ca2+ regulatory pathway in vivo using microinjection of viral vectors. Multiple outcomes will be assessed in the same animals using a multidisciplinary approach comprising extensive behavioral testing, state-of-the-art intracellular electrophysiology with concomitant Ca2+ imaging, immunohistochemistry, and gene microarray analysis. These studies should substantially elucidate aging changes that depend on Ca2+ dysregulation and should clearly test the role of FKBPs in Ca2+ dysregulation and hippocampal function during aging. Chronic intervention studies are proposed that could have direct translational relevance and lead directly to novel preventative and therapeutic treatments against aging-related decline of brain function. Given the dramatic increase in the aging population, it is becoming increasingly important to identify and develop such therapies to maintain cognitive function in the elderly. PUBLIC HEALTH RELEVANCE: The aging population of the United States is projected to increase at a dramatic rate with numbers that will undoubtedly impact our healthcare system (20% of the population will be >65 years of age by the year 2030). Cognitive decline frequently accompanies aging and depending on the severity, can significantly affect quality of life. Our results indicate that a specific pathway (FKBP-Ca2+) that plays a major role in cardiac failure may also play a critical role in brain aging and cognitive decline; thus the goal of this project is to use gene therapy techniques to determine whether such interventions can prevent or slow the onset of age-related brain decline. The outcomes may have substantial therapeutic implications.