Effects of the Integrated Stress Response in HIV Associated Dementia

描述（由申请人提供）：尽管引入了高效抗逆转录病毒疗法（HAART），但人类免疫缺陷病毒相关痴呆（HAD）的患病率一直在稳步上升。HAD中的神经元损伤和丢失是由hiv感染、激活的巨噬细胞/小胶质细胞通过可溶性神经毒性介质（包括活性氧（ROS）、兴奋毒素、其他代谢物以及病毒蛋白）引发的。这些诱导氧化应激的介质可直接损伤神经元，并改变星形胶质细胞的内稳态功能，如谷氨酸的内稳态，从而导致兴奋性神经元损伤。重要的是，一些体外和体内研究表明，氧化应激和兴奋性毒性可能是HAD发病的关键机制。神经元和星形胶质细胞如何在HIV感染的中枢神经系统（CNS）中对氧化应激作出反应在很大程度上是不明确和未充分探索的。氧化应激的主要下游反应是诱导最近描述的综合应激反应（ISR），这可能是氧化应激和兴奋性毒性之间的关键联系。ISR的激活导致翻译衰减、ER伴侣基因启动子的反激活、蛋白质降解途径的激活和内源性抗氧化反应的激活。这些反应的诱导受三种不同信号通路中的一种或多种调节：胰内质网激酶（PERK）、IRE1 α和ATF6。在HIV诱导的中枢神经系统损伤过程中，神经元或星形胶质细胞是否会诱导其中一种或全部途径尚不清楚；然而，我们已经证明，HIV感染单核细胞来源的巨噬细胞（HIV-M/M）的上清液在体外培养的原代星形胶质细胞中诱导了ISR的几种成分，包括PERK。此外，我们发现HAART中使用的几种抗逆转录病毒药物也能诱导原代星形胶质细胞的ISR。因此，我们假设暴露于HIV M/M和/或HAART后星形胶质细胞ISR的激活是HAD中神经元损伤/存活的主要决定因素。我们的目标是确定星形胶质细胞中ISR激活在体外和体内HAART治疗中介导HAD神经元损伤的作用。为此，我们将：1)确定HIV-M/M上清触发的ISR激活影响星形胶质细胞神经保护功能和存活的机制；2)确定HAART药物在星形胶质细胞ISR激活中的作用；3)确定并验证慢性激活ISR通路在HAD中的作用。通过研究ISR的作用，我们希望揭示HIVE中神经元功能障碍和丧失的新机制，并阐明当前HAART治疗对星形细胞介导的神经元存活的影响。由于炎症浸润和氧化应激，HIV相关痴呆患者的大脑细胞应激增加。已知这些压力源激活了非神经细胞中称为综合应激反应的保护性途径。本研究旨在评估暴露于hiv感染巨噬细胞产物和高活性抗逆转录病毒治疗剂的星形胶质细胞中综合应激反应的激活状态，并确定这种激活对神经元存活的影响。

DESCRIPTION (provided by applicant): Despite the introduction of highly active antiretroviral therapy (HAART), the prevalence of human immunodeficiency virus associated dementia (HAD) has been steadily increasing. Neuronal injury and loss in HAD is initiated by HIV-infected, activated macrophage/microglia via soluble neurotoxic mediators including reactive oxygen species (ROS), excitotoxins, and other metabolites as well as viral proteins. These mediators, which induce oxidative stress, are known to injure neurons directly and alter astrocytic homeostatic functions such as glutamate homeostasis which can lead to excitotoxic neuronal injury. Importantly, several studies in vitro and in vivo have shown that oxidative stress and excitotoxicity are likely critical mechanisms of pathogenesis in HAD. How neurons and astrocytes respond to oxidative stress in HIV infection of the central nervous system (CNS) is largely undefined and underexplored. A major downstream response to oxidative stress is induction of the recently described integrated stress response (ISR) which may be the critical link between oxidative stress and excitotoxicity. Activation of the ISR results in translational attenuation, transactivation of ER chaperone gene promoters, activation of protein degradation pathways and activation of the endogenous antioxidant response. Induction of these responses is regulated by one or more of three distinct signaling pathways: pancreatic endoplasmic reticulum kinase (PERK), IRE1 alpha, and ATF6. Whether one or all of these pathways are induced in neuronal or astrocytic cells during HIV induced CNS injury is not known; however, we have demonstrated that supernatants from HIV infected monocyte derived macrophages (HIV-M/M) induce several components of the ISR including PERK in primary astrocytes in vitro. In addition, we have found that several antiretroviral drugs used in HAART also induce ISR in primary astrocytes. Thus, we hypothesize that that activation of the ISR in astrocytes by HIV M/M and/or HAART exposure is a major determinant of neuronal injury/survival in HAD. Our goal is to determine the role of ISR activation in astrocytes by HIV M/M and HAART therapeutics in mediating neuronal damage in vitro and in vivo in HAD. To do this we will: 1) Determine the mechanism by which ISR activation triggered by HIV-M/M supernatants impacts astrocyte neuroprotective functions and survival, 2) Define the role of HAART drugs in ISR activation in astrocytes, and 3) Define and validate the contribution of chronic activation of the ISR pathways in HAD. By investigating the role of ISR, we expect to uncover a novel mechanism for neuronal dysfunction and loss in HIVE and elucidate the impact of current HAART therapeutics on astrocytic mediated neuronal survival. Patients with HIV associated dementia have increased cellular stress in their brain due to inflammatory infiltration and oxidative stress. These stressors are known activate a protective pathway called the integrated stress response in non-neural cells. This proposal aims to assess the state of activation of the integrated stress response in astrocytes exposed to HIV-infected macrophage products and highly active antiretroviral therapeutic agents and determine the impact of such activation on neuronal survival.