Astrocyte Activation, Dysfunction & Apoptosis in HAD

HIV相关性痴呆(HAD)的主要病理特征包括星形胶质细胞增生/激活、巨噬细胞/小胶质细胞(M/M)激活、突触损伤以及神经元和星形胶质细胞的凋亡。HAD中M/M激活的机制尚不清楚，但HIV激活的M/M释放的因子(谷氨酸、Fas-L、肿瘤坏死因子-α、病毒蛋白等)可能通过多种机制参与星形胶质细胞和神经元的损伤。此外，星形胶质细胞的激活和损伤很可能是放大神经元损伤的关键。 通过损害星形胶质细胞的高亲和力谷氨酸清除和相关的神经保护功能。尽管有证据表明这在HAD发病机制中是关键的，但HIV/MM损伤ASTO的机制受到的关注相对较少。我们的假设是，HIV激活的M/M诱导星形胶质细胞和神经元的损伤和凋亡以及星形胶质细胞的激活和相关功能障碍；这通过丧失神经保护功能(如谷氨酸清除)来加剧神经元损伤。我们已经建立了神经细胞和星形胶质细胞的细胞凋亡和功能障碍的体外模型，并表明由HIV-M/M兴奋性毒素触发的线粒体介导的(内在)细胞凋亡定义了一条主要的途径，通过这种途径 HIV-M/M损伤神经元。我们还建立了一种独特的人星形胶质细胞模型，并通过表达Bcl2来调节线粒体介导的星形胶质细胞的凋亡。此外，我们还发现在HAD脑中未调控的Fas-L抑制星形胶质细胞中谷氨酸的运输。肿瘤坏死因子-α抑制星形胶质细胞谷氨酸转运，促进M/M转运。最后，我们在体内进行了 研究使用一种新的单细胞信使核糖核酸扩增/基因图谱方法，开始定义HAD中单个脑细胞的基因表达模式。我们的目标是利用我们的体外模型来确定HIV/MM引起的星形胶质细胞激活及其相关功能障碍和凋亡的途径，并利用我们的体内基因表达分析方法来确定HAD在体内激活的途径。我们将：1)确定HIV-M/M诱导星形胶质细胞激活和凋亡的机制和途径以及Fas死亡受体的作用；2)确定死亡受体(Fas、TNF)调控星形胶质细胞和M/M高亲和力谷氨酸转运的机制及其对神经元存活的影响；3)利用我们的单细胞mRNA分析来确定星形胶质细胞凋亡的体内途径和激活调节HAD高亲和力谷氨酸转运体表达的模式，以验证和推广体外发现的结果。了解HAD中星形胶质细胞损伤的机制可能会确定更多的靶点 HAD的全面神经保护。

The cardinal pathological features of HIV-associated dementia (HAD) include astrogliosis/activation, macrophage/microglia (M/M) activation, synaptic damage, and apoptosis of neurons and astrocytes. The mechanisms of M/M activation in HAD remain uncertain, but factors released by HIV-activated M/M (glutamate, Fas-L, TNF-alpha, viral proteins, others) are likely responsible for astrocytic & neuronal injury through multiple mechanisms. Moreover, astrocyte activation and injury are critical in amplifying neuronal damage, most likely through impairment of astrocyte high-affinity glutamate scavenging and related neuroprotective functions. The mechanisms by which HIV/MM injure astrocvtes have received relatively little attention despite the evidence that this is critical in HAD pathogenesis. Our hypothesis is that HIV-activated M/M induce both astrocyte and neuronal injury and apoptosis as well as astrocyte activation and associated dysfunction; and that this exacerbates neuronal injury through loss of neuroprotective functions such as glutamate scavenging. We have developed in vitro models for neuronal and astrocytic apoptosis and dysfunction and have shown that mitochondrial-mediated (intrinsic) apoptosis triggered by HIV-M/M excitotoxins defines a major pathway by which HIV-M/M injure neurons. We also established a unique human astrocyte cell model with inducible trans-gene expression, and have modulated mitochondrial-mediated astrocyte apoptosis through Bcl-2 expression. Furthermore, we found that Fas-L, which is unregulated in HAD brain, suppresses glutamate transport in astrocytes. and that TNF-alpha suppresses glutamate transport in astrocytes and enhances transport in M/M. Finally, we have carried out in vivo studies using a novel single cell mRNA amplification/gene profiling approach to begin to define gene expression patterns of individual brain cells in HAD. Our goal is to utilize our in vitro models to define the pathways of astrocyte activation and associated dysfunction & apoptosis elicited by HIV/MM, and exploit our in vivo gene expression analysis approach to define the pathways activated in vivo in HAD. We will: 1) Identify the mechanisms and pathways of astrocyte activation and apoptosis induced by HIV-M/M and the role of Fas death receptors; 2) Determine the mechanisms of death receptor (Fas, TNF) modulation of high-affinity glutamate transport in astrocytes and M/M and the effects on neuronal survival; and 3) Define the in vivo pathways of astrocyte apoptosis and the patterns of activation regulating high-affinity glutamate transporter expression in HAD using our single-cell mRNA analysis to validate and extend in vitro findings. Understanding the mechanisms of astrocyte injury in HAD may identify additional targets for comprehensive neuroprotection in HAD.