Effects of the Integrated Stress Response in HIV Associated Dementia

描述(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性痴呆(HAD)的患病率一直在稳步上升。HAD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)、兴奋性毒素和其他代谢物以及病毒蛋白启动的。这些诱导氧化应激的介质直接损伤神经元，改变星形细胞的稳态功能，如谷氨酸稳态，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。在HIV感染中枢神经系统(CNS)中，神经元和星形胶质细胞如何应对氧化应激在很大程度上是未知的，也是研究不足的。氧化应激的一个主要下游反应是诱导最近描述的整合应激反应(ISR)，这可能是氧化应激与兴奋性毒性之间的关键联系。ISR的激活导致翻译减弱、ER伴侣基因启动子的反式激活、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个不同的信号通路中的一个或多个调控：胰腺内质网激酶(PERK)、IRE1α和ATF6。在HIV诱导的中枢神经系统损伤过程中，神经细胞或星形胶质细胞是否诱导了上述途径中的一条或全部尚不清楚；然而，我们已经在体外证明了HIV感染的单核细胞衍生巨噬细胞(HIV-M/M)的培养上清液在原代星形胶质细胞中诱导了包括PERK在内的ISR的几个组成部分。此外，我们还发现，几种用于HAART的抗逆转录病毒药物也可以诱导原代星形胶质细胞发生ISR。因此，我们推测，HIV M/M和/或HAART暴露对星形胶质细胞ISR的激活是HAD神经元损伤/存活的主要决定因素。我们的目标是确定HIV M/M和HAART疗法对星形胶质细胞ISR激活在介导HAD体外和体内神经元损伤中的作用。为此，我们将：1)确定由HIV-M/M上清液触发的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)确定和验证HAD中ISR通路的慢性激活的贡献。通过研究ISR的作用，我们期望揭示蜂巢中神经元功能障碍和丢失的新机制，并阐明当前HAART疗法对星形胶质细胞介导的神经元存活的影响。艾滋病毒相关性痴呆患者由于炎症渗透和氧化应激而增加了大脑中的细胞压力。众所周知，这些应激源激活了非神经细胞中一种名为综合应激反应的保护性途径。这项建议旨在评估暴露于HIV感染的巨噬细胞产品和高效抗逆转录病毒治疗药物的星形胶质细胞中整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.