Dissecting the impact of senescence on microglia function and neurodegeneration

项目摘要/摘要 细胞衰老是一种普遍的应激反应，由许多刺激触发，包括端粒 功能障碍、DNA损伤、氧化应激、致癌信号异常和慢性炎症。衰老 细胞停止增殖，经历代谢和转录变化，并分泌各种促炎因子 分子，统称为衰老相关分泌表型(SASP)。SASP调解了许多 许多组织中随年龄增长而衰老的病理生理效应。大脑中的最新数据 表明神经退行性变过程中神经胶质细胞会衰老。这包括小胶质细胞，一种常驻的中枢神经系统 巨噬细胞。重要的是，消融所有衰老的胶质细胞，包括小胶质细胞、星形胶质细胞和少突胶质细胞 祖细胞在阿尔茨海默病(AD)相关和tau依赖的小鼠模型中具有神经保护作用 神经退行性变。然而，衰老是如何影响小胶质细胞功能以及如何衰老的，目前尚不清楚。 然后，小胶质细胞参与了疾病的进程。神经退行性疾病的一个共同特征是 反应性、促炎性、吞噬功能障碍的小胶质细胞，现在我们将检验这一假设 衰老抑制正常的小胶质细胞吞噬功能，促进促炎细胞类型，这 加速AD相关的神经退行性变。我们将使用衰老调节剂S-2来验证这一假设 作为一种遗传工具。使用细胞培养或条件过表达SMurf2的小鼠，我们有独特的 在体外和体内以高时间分辨率特异性地诱导小胶质细胞衰老的能力。我们 也可以表达连接酶死亡的SMurf2，作为蛋白质过度表达的优雅控制。使用这些工具，我们 将研究小胶质细胞的衰老是否影响其吞噬细胞突触和淀粉样蛋白Aβ的能力 目标1.在目标2中，我们将评估衰老如何影响小胶质细胞的动态平衡和向反应性的转变， 促炎状态。在目标3中，我们将确定衰老的小胶质细胞对神经退行性变的影响 阿尔茨海默病相关神经变性APP/PS1模型的表型和识别感觉神经溶解治疗是否 去除衰老细胞可以减轻或逆转神经退行性变。这些目标得到了我们强大的 初步数据表明，我们可以在体外和体内过表达SMurf2并诱导小胶质细胞衰老。 此外，在体外衰老的小胶质细胞对细胞碎片的吞噬能力降低，这让人想起 在AD和吞噬Aβ中观察到。利用我们独特的遗传工具包和我们在 小胶质细胞生物学(Schafer)和衰老机制(Zhang)，我们处于有利地位 对细胞衰老如何影响小胶质细胞功能的基本见解，进而， 神经退行性变过程。从长远来看，我们的目标是确定新的、基于衰老的治疗靶点 AD和其他相关疾病，其中衰老是一个主要的风险因素。

Project Summary/Abstract Cellular senescence is a general stress response that is triggered by many stimuli, including telomere dysfunction, DNA damage, oxidative stress, aberrant oncogenic signaling and chronic inflammation. Senescent cells cease proliferation, undergo metabolic and transcriptional changes and secrete various pro-inflammatory molecules, collectively known as senescence-associated secretory phenotype (SASP). SASP mediates many of the pathophysiological effects of senescence with advancing age in many tissues. Recent data in the brain suggest that glial cells become senescent during neurodegeneration. This includes microglia, a resident CNS macrophage. Importantly, ablating all senescent glial cells, including microglia, astrocytes, and oligodendrocyte progenitor cells, is neuroprotective in mouse models of Alzheimer’s disease (AD)-related and tau-dependent neurodegeneration. However, it is unknown how senescence impacts microglial function and how senescent microglia then contribute to the disease process. A common feature among neurodegenerative diseases are reactive, pro-inflammatory microglia with dysfunctional phagocytic function, we will now test the hypothesis that senescence inhibits normal microglial phagocytic function and promotes a pro-inflammatory cell type, which accelerates AD-relevant neurodegeneration. We will test this hypothesis using a senescence regulator Smurf2 as a genetic tool. Using cell culture or mice with conditional overexpression of Smurf2, we have the unique capability to induce senescence specifically in microglia with high temporal resolution in vitro and in vivo. We also can express a ligase-dead Smurf2 as an elegant control for protein overexpression. Using these tools, we will investigate whether senescence in microglia affects their ability to phagocyte synapses and amyloid Aβ in Aim 1. In Aim 2, we will assess how senescence affects microglial homeostasis and transition into a reactive, pro-inflammatory state. In Aim 3, we will determine the impact of senescent microglia on neurodegenerative phenotypes in the APP/PS1 model of AD-relevant neurodegeneration and identify whether senolytic treatment to ablate senescent cells can attenuate or reverse neurodegeneration. These aims are supported by our strong preliminary data that we can overexpress Smurf2 and induce senescence in microglia in vitro and in vivo . Further, in vitro senescent microglia exhibit reduced phagocytosis of cellular debris, reminiscent of what is observed in AD and engulfment of Aβ. Leveraging our unique genetic tool kit and our combined expertise in microglial biology (Schafer) and senescence mechanisms (Zhang), we are in a strong position to gain fundamental insight into how cellular senescence affects microglial function and, in turn, the neurodegenerative process. Long-term, we aim to identify novel, senescence-based therapeutic targets for AD and other related diseases where aging is a major risk factor.