Aging and Alzheimer's Disease Potential Link with IGF1-R

描述（由申请人提供）：年龄是迟发性阿尔茨海默病（AD）最重要的危险因素，占所有AD痴呆病例的97%。我们最近的研究表明，大脑正常衰老的特征是从TrkA到p75NTR受体系统的逐步转换，导致第二信使神经酰胺的激活和淀粉样蛋白2肽（A2）的产生增加。这些作用可以通过p75NTR的遗传破坏和中性鞘磷脂酶（nSMase）的生化抑制来阻断，nSMase是激活神经酰胺的酶。在“初步研究”一节中，我们发现IGF1-R信号的激活可以上调p75NTR，同时下调TrkA。IGF1-R下游的信号级联需要IRS2、PI3K、PIP3、Egr-1、HIPK2参与，受PTEN和p44的抑制控制。我们还发现IGF1-R在p75NTR/TrkA的上游调控A2的产生。此外，在p44+/+转基因小鼠中，IGF1-R信号的过度激活导致衰老加速，TrkA向p75NTR的转换提前，A2的产生增加。最后，p44+/+、APP695/swe双转基因小鼠会出现早期和严重的神经变性，并在出生后3个月导致死亡。上述事件均与神经酰胺的过量产生和BACE1的分子稳定有关。因此，我们的研究发现了衰老和阿尔茨海默病之间的一种新的分子联系，并将引领该领域朝着新的方向发展，如果成功，将对预防一种预计到2050年将影响约1500万美国人的疾病产生直接影响。本应用的长期目标是分析IGF1-R信号在AD发病机制中的作用，并评估其是否可以作为预防晚发性AD的新靶点。Specific Aim 1将分析IGF1-R下游的信号分子的作用。我们已经描述了在原代神经元和神经细胞系中进行的一些生化和遗传研究。生化方法包括体外检测和药理学抑制剂，而遗传方法包括siRNA、反义寡核苷酸和靶向信号分子的显性突变体。我们还将使用器官型脑培养和衰老动物模型，包括正常喂养（正常衰老）和热量限制（延迟衰老）野生型小鼠，以及p44+/+小鼠（加速衰老）。Specific Aim 2将在我们新开发的p44+/+， APP695/swe小鼠模型中分析IGF1-R信号在AD病理中的作用。为此，我们描述了生化、组织学和认知方法。此外，我们还将用马霉素A（抑制神经酰胺的产生）治疗p44+/+， APP695/swe小鼠，以评估我们是否可以阻断/延迟病理。最后，Aim 1（我们计划确定生化靶点）和Aim 2（我们计划表征第一个在过度活跃衰老程序控制下的AD小鼠模型）之间的协调将使我们能够测试新的药理学策略，以预防与衰老相关的AD风险。公共卫生相关性：衰老是阿尔茨海默病（AD）最重要的风险因素，AD是世界上最常见的痴呆原因。由于我们正在经历的预期寿命的增加，预计到2050年，全球将有4500万人患有阿尔茨海默病。在过去的三年中，我们已经确定了一种新的分子途径，将衰老与AD神经病理学联系起来。我们还开发了第一个可以研究衰老对阿尔茨海默病影响的小鼠模型。鉴于这些事件在阿尔茨海默病的发病机制中所起的作用，我们的研究结果对阿尔茨海默病的神经生物学以及与衰老相关的阿尔茨海默病风险的预防具有深远的意义。这项建议的长期目标是扩展我们的发现，并充分表征我们已经确定的分子途径。这将使我们能够设计新的药物方法来预防阿尔茨海默病。

DESCRIPTION (provided by applicant): Aging is the single most important risk factor for late-onset Alzheimer's disease (AD), which represents ~97% of all cases of AD dementia. We have recently shown that normal aging of the brain is characterized by a progressive switch from the TrkA to the p75NTR receptor system that leads to activation of the second messenger ceramide and increased production of amyloid 2-peptide (A2). These effects can be blocked by genetic disruption of p75NTR and biochemical inhibition of neutral sphingomyelinase (nSMase), the enzyme that activates ceramide. In the Preliminary Studies section we show that activation of IGF1-R signaling up- regulates p75NTR while down-regulating TrkA. The signaling cascade downstream of IGF1-R requires IRS2, PI3K, PIP3, Egr-1, HIPK2, and is under the inhibitory control of PTEN and p44. We also show that IGF1-R acts up-stream of p75NTR/TrkA in the regulation of A2 generation. In addition, hyperactivation of IGF1-R signaling in p44+/+ transgenic mice leads to an accelerated form of aging, early TrkA to p75NTR switch, and increased production of A2. Finally, p44+/+, APP695/swe double-transgenic mice develop an early and severe form of neurodegeneration that results in death by the 3rd month of life. The above events were all linked to overproduction of ceramide and molecular stabilization of BACE1. Therefore, our studies have uncovered a novel molecular link between aging and AD, and are leading the field toward new directions that, if successful, will have direct impact on the prevention of a disease that is projected to affect ~15 million Americans by the year 2050. The long-term objective of this application is to analyze the role of IGF1-R signaling in the pathogenesis of AD and to assess whether it can serve as a novel target for the prevention of late-onset AD. Specific Aim 1 will analyze the role of the signaling molecules that act down-stream of IGF1-R. We have described several biochemical and genetic studies in both primary neurons and neuronal cell lines. The biochemical approach includes in vitro-assays and pharmacologic inhibitors, whereas the genetic approach includes siRNA, antisense oligonucleotides, and dominant mutants of the targeted signaling molecules. We will also use organotypic brain cultures and animal models of aging, including normally-fed (normal aging) and caloric-restricted (delayed aging) wild-type mice, and p44+/+ mice (accelerated aging). Specific Aim 2 will analyze the role of IGF1-R signaling on AD pathology in a our newly developed p44+/+, APP695/swe mouse model. For this purpose, we have described biochemical, histological, and cognitive approaches. In addition, we will also treat p44+/+, APP695/swe mice with manumycin A (which inhibits the production of ceramide) to assess whether we can block/delay the pathology. Finally, the coordination between Aim 1, where we plan to identify biochemical targets, and Aim 2, where we plan to characterize the first AD mouse model that is under the control of a hyperactive aging program, will allow us to test novel pharmacological strategies to prevent the AD-risk associated with aging. PUBLIC HEALTH RELEVANCE: Aging is the single most important risk factor for Alzheimer's disease (AD), which represents the most common cause of dementia in the World. Because of the increase in life expectancy that we are experiencing, AD is predicted to affect 45 million individuals worldwide by the year 2050. During the last three years we have identified a novel molecular pathway that links aging to AD neuropathology. We have also developed the first mouse model that allows to study the effect of aging on AD. Given the role that these events play in the pathogenesis of AD, our results have profound implications for the neurobiology of the disease and for the prevention of the AD-risk associated with aging. The long-term objective of this proposal is to expand upon our findings and fully characterize the molecular pathway that we have identified. This will allow us to design new pharmacologic approaches for the prevention of AD.