Gp120, Macrophage Activation & TNF in HIV Encephalopathy

HIV相关痴呆(HAD)是由HIV-1在脑内复制引起的，而未感染和感染的脑巨噬细胞/小胶质细胞(M/M)的激活是与临床疾病密切相关的关键因素。广泛的研究表明，HIV刺激的M/M产物参与了发病机制，如在HAD中升高的、由脑中激活的M/M产生的TNF-a，似乎在神经元损伤和激活的永续过程中发挥了重要作用。尽管对激活的M/M释放的潜在介质&神经毒素知道得很多 HAD，目前尚不清楚HIV-1如何触发M/M激活，启动最终导致神经元损伤的事件，这是我们对HAD发病机制理解的一个重要空白。 为了进入细胞，HIV与CD4结合，然后是两个趋化因子受体CCR5或CXCR4中的一个。趋化因子受体的正常功能是介导对细胞外刺激的激活和趋化。T细胞中CD_4的S功能和信号转导机制已明确，但对巨噬细胞中的CD_4功能或信号转导机制知之甚少。在初步研究中，我们发现HIV-1包膜糖蛋白gp120与M/M上的CD4和趋化因子受体结合，启动细胞内信号转导，并通过这些受体激活特定的通路导致细胞 炎症介质的激活和释放，包括肿瘤坏死因子-α等参与HAD发病的其他产物。我们的假设是，大脑中的M/M激活部分是由于gp120与CD4和趋化因子受体的相互作用，引发细胞内信号，导致炎症和神经毒性介质的产生，如肿瘤坏死因子-α，这引发了一系列炎症、激活，最终导致神经元损伤。我们的目标是确定HIV-1gp120在大脑中触发M/M激活的特定分子机制，与HAD发病相关。为此，我们将：(1)确定HIV-1 gp120的机制和途径 调节巨噬细胞中肿瘤坏死因子-α的产生：(2)确定原代巨噬细胞中CD4介导的信号传导途径：(3)确定与HAD相关的病毒和宿主遗传因素对巨噬细胞TNF-a诱导的影响；(4)确定和比较gp120在体外和体内诱导HAD中巨噬细胞基因表达变化的模式。我们预计这些研究将为HAD中细胞激活的启动机制提供洞察力，并最终为有针对性的干预这一过程提供合理的基础。

HIV-associated dementia (HAD) is initiated by HIV-1 replication within the brain, and activation of both uninfected & infected brain macrophage/microglia (M/M) is a critical element that is closely linked to clinical disease. Extensive research has implicated products of HIV-stimulated M/M in pathogenesis, such as TNF-a, which is elevated in HAD, produced by activated M/M in the brain, and appears to play an important role in neuronal injury & the perpetuation of activation. Although much is known about potential mediators & neurotoxins that are released by activated M/M in HAD, it remains unknown how HIV-1 triggers M/M activation to initiate the events that culminate in neuronal injury and this is an important gap in our understanding of HAD pathogenesis. To enter cells, HIV binds CD4 followed by one of two chemokine receptors, CCR5 or CXCR4. Chemokine receptors' normal function is to mediate activation & chemotaxis in response to extracellular stimuli. CD4's function and signaling are well-defined in T cells, but little is known about CD4 function or signaling in macrophages. In preliminary studies, we found that HIV-1 Env glycoprotein gp120 binding to both CD4 & chemokine receptors on M/M initiates intracellular signaling, and that activation of specific pathways through these receptors leads to cellular activation and release of inflammatory mediators including TNF-a & other products implicated in HAD pathogenesis. Our hypothesis is that M/M activation in the brain results, in part, from gp120 interaction with CD4 & chemokine receptors, eliciting intracellular signals that lead to production of inflammatory & neurotoxic mediators such as TNF-a, which initiates a cascade of inflammation, activation &, ultimately, neuronal injury. Our goal is to define specific molecular mechanisms by which HIV-1 gp120 triggers M/M activation in the brain relevant to HAD pathogenesis. To do this we will: (1) Identify mechanism & pathways by which HIV-1 gp120 regulates TNF-a production in M/M: (2) Define the pathways for CD4-mediated signaling in primary macrophages: (3) Determine the effect on macrophage TNF-a induction of viral & host genetic factors linked to HAD, and; (4) Define & compare the patterns of altered macrophage gene expression in vitro elicited by gp120 & in vivo in HAD. We anticipate that these studies will provide insight into initiating mechanisms of cellular activation in HAD, as well as, ultimately, provide a rational basis for targeted strategies to interfere with this process.