San Diego Biomedical Research Institute, San Diego, CA, United States of America.
Department of Neurosciences, The Scripps Research Institute, La Jolla, CA, United States of America.
PLoS One. 2018 Jun 26;13(6):e0199861. doi: 10.1371/journal.pone.0199861. eCollection 2018.
The Human Immunodeficiency Virus (HIV) infects cells in the Central Nervous System (CNS), where the access of antiretrovirals and antibodies that can kill the virus may be challenging. As a result of the early HIV entry in the brain, infected individuals develop inflammation and neurological deficits at various levels, which are aggravated by drugs of abuse. In the non-human primate model of HIV, we have previously shown that drugs of abuse such as Methamphetamine (Meth) increase brain viral load in correlation with a higher number of CCR5-expressing myeloid cells. CCR5 is a chemokine receptor that may be involved in increasing inflammation, but also, it is a co-receptor for viral entry into target cells. CCR5-expressing myeloid cells are the main targets of HIV in the CNS. Thus, the identification of factors and mechanisms that impact the expression of CCR5 in the brain is critical, as changes in CCR5 levels may affect the infection in the brain. Using a well-characterized in vitro system, with the THP1 human macrophage cell line, we have investigated the hypothesis that the expression of CCR5 is acutely affected by Meth, and examined pathways by which this effect could happen. We found that Meth plays a direct role by regulating the abundance and nuclear translocation of transcription factors with binding sites in the CCR5 promoter. However, we found that the main factor that modifies the CCR5 gene promoter at the epigenetic level towards transcription is Dopamine (DA), a neurotransmitter that is produced primarily in brain regions that are rich in dopaminergic neurons. In THP1 cells, the effect of DA on innate immune CCR5 transcription was mediated by DA receptors (DRDs), mainly DRD4. We also identified a role for DRD1 in suppressing CCR5 expression in this myeloid cell system, with potential implications for therapy. The effect of DA on innate immune CCR5 expression was also detectable on the cell surface during acute time-points, using low doses. In addition, HIV Tat acted by enhancing the surface expression of CCR5, in spite of its poor effect on transcription. Overall, our data suggests that the exposure of myeloid cells to Meth in the context of presence of HIV peptides such as Tat, may affect the number of HIV targets by modulating CCR5 expression, through a combination of DA-dependent and-independent mechanisms. Other drugs that increase DA may affect similar mechanisms. The implications of these epigenetic and translational mechanisms in enhancing HIV infection in the brain and elsewhere are demonstrated.
人类免疫缺陷病毒 (HIV) 感染中枢神经系统 (CNS) 中的细胞，而抗逆转录病毒药物和能够杀死病毒的抗体进入中枢神经系统可能具有挑战性。由于 HIV 早期进入大脑，感染个体在各个层面都会出现炎症和神经功能缺损，而滥用药物会加剧这种情况。在 HIV 的非人类灵长类动物模型中，我们之前已经表明，诸如甲基苯丙胺 (Meth) 等滥用药物会增加大脑中的病毒载量，这与表达 CCR5 的髓样细胞数量增加有关。CCR5 是一种趋化因子受体，可能与炎症增加有关，但也是病毒进入靶细胞的共受体。表达 CCR5 的髓样细胞是 HIV 在中枢神经系统中的主要靶标。因此，确定影响大脑中 CCR5 表达的因素和机制至关重要，因为 CCR5 水平的变化可能会影响大脑中的感染。我们使用了一种经过充分表征的体外系统，即 THP1 人巨噬细胞系，研究了 CCR5 表达是否会被 Meth 急性影响的假说，并研究了可能发生这种影响的途径。我们发现，Meth 通过调节 CCR5 启动子上具有结合位点的转录因子的丰度和核易位来直接发挥作用。然而，我们发现，主要因素是在表观遗传水平上调节 CCR5 基因启动子向转录的多巴胺 (DA)，DA 主要在富含多巴胺能神经元的脑区产生。在 THP1 细胞中，DA 对先天免疫 CCR5 转录的影响是通过 DA 受体 (DRD) 介导的，主要是 DRD4。我们还发现，DRD1 在抑制该髓样细胞系统中的 CCR5 表达方面也发挥了作用，这可能对治疗有影响。在急性时间点，使用低剂量，DA 也可以在细胞表面检测到对先天免疫 CCR5 表达的影响。此外，HIV Tat 通过增强 CCR5 的表面表达来发挥作用，尽管其对转录的影响不佳。总的来说，我们的数据表明，髓样细胞暴露于 Meth 时，如果存在 HIV 肽，如 Tat，可能会通过调节 CCR5 表达，通过 DA 依赖和非依赖机制的组合，影响 HIV 靶标的数量。其他增加 DA 的药物可能会影响类似的机制。这些表观遗传和翻译机制在增强大脑和其他部位的 HIV 感染中的作用得到了证明。
