Interplay between neuroprotective pathways, HIV, and astrocytes

描述(申请人提供)：艾滋病毒引起神经疾病(神经艾滋病)，从轻微的认知和运动障碍到艾滋病毒相关性痴呆(HAD)。需要更好地了解神经艾滋病的潜在机制，因为这将为神经艾滋病的治疗方法提供建议。为了实现这一目标，我们的战略是确定内源性神经保护机制与脑细胞中艾滋病毒之间的相互作用。WNT/2-catenin活性是神经元和星形胶质细胞中的促生存信号。WNT/2-catenin调控约500个基因，参与多种细胞功能，如细胞增殖和全身生存，包括中枢神经系统。越来越多的证据表明，2-连环素和神经退行性变的水平降低了。然而，Wnt/2-catenin活性在神经艾滋病中的作用尚不清楚。我们报告了Wnt/2-catenin活性与HIV复制之间的负相关关系。具体地说，我们证明了活性Wnt/2-catenin抑制HIV复制，而非活性Wnt/2-catenin诱导HIV复制。此外，与HAD严重程度相关的促炎细胞因子IFN3和HIV编码的调节蛋白TAT都降低了星形胶质细胞中的Wnt/2-catenin信号。我们认为(I)Wnt/2-catenin信号(Wnt)是HIV复制和脑内稳态的关键调节因子，(Ii)Wnt下调(由TAT或IFN3介导)促进星形胶质细胞和神经元的凋亡，这在中枢神经系统HIV疾病的发病机制中起着重要作用。在目标1中，利用星形胶质细胞(具有高内源性Wnt/2-catenin表达)，我们将确定Wnt/2-catenin调节HIV复制的机制。在目标2中，使用星形胶质细胞、小胶质细胞和单核细胞来源的巨噬细胞，我们将确定宿主(IFN3)和病毒(TAT)因子在调节Wnt/2-catenin信号和HIV复制中的作用。在目标3中，使用原代培养的人胎儿神经胶质/神经细胞混合培养，我们将确定大脑Wnt活性调节对星形胶质细胞和神经元存活的影响。总而言之，这些研究将有助于更好地理解大脑Wnt/2-catenin活性在HIV复制和神经胶质/神经元存活中的作用。这些研究还可以加快2-连环蛋白信号激活剂的开发，这种信号可以穿透中枢神经系统，抑制艾滋病毒复制，并提高星形胶质细胞和神经元的存活率。公共卫生相关性：尽管接受抗艾滋病毒药物治疗，但大约50%的艾滋病毒感染者会出现认知和运动障碍。这可能是因为目前的抗艾滋病毒药物对大脑的渗透性很差。由于神经元不会直接感染艾滋病毒，因此它们的死亡/调节失调被认为是通过间接事件发生的。我们的应用将研究被定义为神经保护(Wnt/2-catenin)的途径、脑细胞中的HIV复制和星形胶质细胞在介导HIV相关神经发病中的作用之间的相互作用。我们已经确定Wnt/2-catenin途径抑制HIV复制。当这条通路开启时，艾滋病毒水平较低，而当它关闭时，艾滋病毒水平较高。我们在星形胶质细胞中证实了这种关系，星形胶质细胞表达高水平的WNT/2-连环蛋白。当星形胶质细胞先用IFN3处理后再感染时，HIV水平较高。这表明，关闭这一途径的信号，如IFN3，将允许爆发低水平的艾滋病毒。这将导致TAT水平升高(一种与星形胶质细胞和神经元凋亡有关的病毒蛋白)。我们证明，Tat反过来关闭Wnt/2-catenin途径，导致HIV目标细胞中更高水平的HIV复制。这些事件的后果是大脑中Wnt/2-catenin活性降低，这将导致星形胶质细胞和神经元对细胞死亡的易感性增加。该模型通过直接(活跃的HIV复制)和间接(增强的细胞死亡)事件将Wnt/2-catenin途径置于HIV介导的神经发病的界面上。澄清这种相互作用可能导致抗击大脑中艾滋病毒感染的新药物策略。

DESCRIPTION (provided by applicant): HIV causes neurologic disorders (NeuroAIDS) ranging from minor cognitive and motor disorders to HIV- associated dementia (HAD). A better understanding of the underlying mechanisms of NeuroAIDS is needed because it would suggest therapeutic approaches for NeuroAIDS. Towards this goal, our strategy is to define the interplay between endogenous neuroprotective mechanisms and HIV in brain cells. Wnt/2-catenin activity is a pro-survival signal in neurons and astrocytes. Wnt/2-catenin regulates ~500 genes involved in diverse cell functions such as cell proliferation and survival throughout the body, including the CNS. Mounting evidence links decreased levels of 2-catenin and neurodegeneration. Yet, the role of Wnt/2-catenin activity in NeuroAIDS is unclear. We reported an inverse relationship between Wnt/2-catenin activity and HIV replication. Specifically, we demonstrated that active Wnt/2-catenin inhibits whereas inactive Wnt/2-catenin induces HIV replication. Further, IFN3, a proinflammatory cytokine associated with HAD severity, and Tat, an HIV-encoded regulatory protein, both diminished Wnt/2-catenin signaling in astrocytes. We propose that (i) Wnt/2-catenin signaling (Wnt) is a key regulator of HIV replication and homeostasis in the brain, and (ii) Wnt down-regulation (mediated by Tat or IFN3) promotes astrocyte and neuronal apoptosis, which contributes to the pathogenesis of HIV disease in the CNS. In Aim 1, using astrocytes (which have high endogenous Wnt/2-catenin expression) we will define the mechanism by which Wnt/2-catenin regulates HIV replication. In Aim 2, using astrocytes, microglia, and monocyte-derived macrophages, we will determine the role of host (IFN3) and viral (Tat) factors in modulating Wnt/2-catenin signaling and HIV replication. In Aim 3, using primary human fetal mixed glial/neuronal brain cell cultures, we will determine the consequences of modulation of brain Wnt activity on the survival of astrocytes and neurons. Collectively, these studies will lead to a better understanding of the role of brain Wnt/2-catenin activity on HIV replication and glial/neuronal survival. These studies could also expedite the development of activators of 2-catenin signaling that can penetrate the CNS, suppress HIV replication, and enhance survival of astrocytes and neurons. PUBLIC HEALTH RELEVANCE: Despite anti-HIV drug therapy, approximately 50% of HIV-infected individuals develop cognitive and motor disorder. This may be due to the poor permeability of current anti-HIV drugs into the brain. Because neurons are not directly infected by HIV, their death/dysregulation is thought to occur through indirect events. Our application will examine the interplay between a pathway that is defined as neuroprotective (Wnt/2-catenin), HIV replication in brain cells, and role of astrocytes in mediating HIV-associated neuropathogenesis. We have established that the Wnt/2-catenin pathway inhibits HIV replication. When this pathway is on, HIV level is low and when it is off, HIV level is high. We demonstrated this relationship in astrocytes, which express high level of Wnt/2-catenin. When astrocytes were first treated with IFN3 then infected, HIV levels were higher. This then suggests that signals that turn off this pathway, such as IFN3, will allow for burst of low-level of HIV. This will then lead to increased Tat level (a viral protein that is linked to apoptosis of astrocytes and neurons). Tat, we demonstrated, in turn turns off the Wnt/2-catenin pathway, leading to higher level of HIV replication in HIV target cells. The consequence of these events is diminished Wnt/2-catenin activity in the brain, which will lead to increased susceptibility of astrocytes and neurons to cell death. This model places the Wnt/2-catenin pathway at the interface of HIV-mediated neuropathogenesis through both direct (active HIV replication) and indirect (enhanced cell death) events. Clarifying this interplay could lead to novel drug strategies to combat HIV infection in the brain.