REGULATION OF CYTOKINE EXPRESSION BY HIV

HIV 对细胞因子表达的调节

• 批准号: 6436378
• 负责人: K. A CLOUSE-STREBEL
• 金额: --
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6436378
• 关键词: AIDS dementia complex; astrocytes; colony stimulating factor; cytokine; gene induction /repression; human immunodeficiency virus 1; human tissue; lipopolysaccharides; macrophage; mixed tissue /cell culture; monocyte; neurotoxicology; nitric oxide; nitric oxide synthase; nuclear factor kappa beta; polymerase chain reaction; virus replication

HIV-1 infects the brain in the early stage of systemic viral infection, but HIV-associated cognitive/motor complex develops later in the course of disease, suggesting that host responses mediated by brain cells may inhibit the early productive infection in the brain and the development of neurologic disease. Macrophages play a critical role in the pathogenesis of HIV infection, both as targets for viral replication and as a source of multifunctional cytokines. Our previous studies revealed that monocyte-derived ET-1 is stimulated during HIV infection and suggested that its potent vasoactive properties could cause alterations in the cerebral perfusion pattern associated with AIDS dementia complex (JI 1993). However, our studies with monocyte derived macrophages (MDM) showed that HIV-1 infection neither induces secretion of ET-1 nor potentiates its production by the known inducer, LPS, in vitro. In addition, expression of the genes for ET-1 and nitric oxide synthase (NOS), an enzyme responsible for production of the potent vasodilator, NO, are not detected by RT-PCR in mRNA prepared from HIV-infected MDM. Thus, the in vitro system looking only at MDM most likely fails to reflect the more complex cellular interactions occurring in vivo. Since HIV-1 producing cells in the brain, such as blood-derived macrophages and brain microglia, are surrounded by astrocytes, we studied the effect of astrocytes on HIV-1 expression in MDM. Co-culture of HIV-infected MDM with primary human astrocytes resulted in diminished virus replication. This effect was mediated in part by an unidentified secreted factor, since astrocyte conditioned medium could suppress HIV replication MDM and paraformaldehyde fixed astrocytes unable to secrete cytokines failed to inhibit HIV. In contrast, cell-to-cell contact with astrocytes augmented HIV-1 replication in MDM, which correlated with enhanced production of M-CSF (AIDS 1999). Additional studies revealed the expression of inducible NOS (iNOS)and production of NO by astrocytes, but not MDM, when astrocytes were cocultured with HIV-infected MDM. This coincided with decreased HIV replication. Supernatants from cocultures of HIV-infected MDM and astrocytes stimulated iNOS expression in astrocytes, but cytokines known to induce iNOS expression were not detected, suggesting a novel factor may mediate this effect. A competitive NOS inhibitor partially reversed the HIV-1 suppressive effect of astrocytes (BLOOD 1999), consistent with a dual mechanism for astrocyte-mediated HIV inhibition. Furthermore, studies utilizing NO donor compounds with variable half lives and flux of production reveal that NO inhibits HIV-1 replication directly via a mechanism most likely involving NFkB. This suggests that astrocytes play a pivotal role in determining the course of neurologic HIV disease via production of HIV modulating cytokines and expression of iNOS/NO. It also leads us to speculate that neurologic damage observed in HIV disease may ensue from prolonged, high level production of NO by astrocytes, which may reflect a host attempt to inhibit virus replication.

HIV-1在全身性病毒感染的早期阶段感染大脑，但HIV相关的认知/运动复合体在疾病过程中发展较晚，这表明由脑细胞介导的宿主反应可能抑制大脑中的早期生产性感染和神经系统疾病的发展。巨噬细胞在HIV感染的发病机制中起着关键作用，既作为病毒复制的靶点，又作为多功能细胞因子的来源。我们之前的研究表明，单核细胞衍生的ET-1在HIV感染期间受到刺激，并表明其强大的血管活性特性可能会导致与艾滋病痴呆综合症相关的脑灌注模式改变（JI 1993）。然而，我们对单核细胞衍生的巨噬细胞（MDM）的研究表明，HIV-1感染既不诱导ET-1的分泌，也不通过已知的诱导剂LPS在体外增强其产生。此外，ET-1和一氧化氮合酶（NOS），一种负责生产有效的血管扩张剂，NO的酶的基因的表达，没有检测到从HIV感染的MDM制备的mRNA的RT-PCR。因此，仅观察MDM的体外系统很可能无法反映体内发生的更复杂的细胞相互作用。由于脑中产生HIV-1的细胞，如血液来源的巨噬细胞和脑小胶质细胞，被星形胶质细胞包围，我们研究了星形胶质细胞对MDM中HIV-1表达的影响。HIV感染的MDM与原代人星形胶质细胞的共培养导致病毒复制减少。这种效应部分由一种未鉴定的分泌因子介导，因为星形胶质细胞条件培养基可以抑制HIV复制MDM和多聚甲醛固定的星形胶质细胞不能分泌细胞因子，不能抑制HIV。相比之下，细胞与星形胶质细胞的接触增加了MDM中HIV-1的复制，这与M-CSF的产生增加相关（AIDS 1999）。进一步的研究表明，诱导型一氧化氮合酶（iNOS）的表达和生产的星形胶质细胞，但不是MDM，当星形胶质细胞与HIV感染的MDM共培养。这与艾滋病毒复制减少相吻合。HIV感染的MDM和星形胶质细胞共培养物的上清液刺激星形胶质细胞中的iNOS表达，但未检测到已知诱导iNOS表达的细胞因子，这表明一种新的因子可能介导这种效应。竞争性NOS抑制剂部分逆转了星形胶质细胞的HIV-1抑制作用（BLOOD 1999），这与星形胶质细胞介导的HIV抑制的双重机制一致。此外，利用具有可变半衰期和生产通量的NO供体化合物的研究揭示，NO通过最可能涉及NF κ B的机制直接抑制HIV-1复制。这表明，星形胶质细胞在确定神经系统HIV疾病的过程中发挥了关键作用，通过生产HIV调节细胞因子和iNOS/NO的表达。这也使我们推测，在HIV疾病中观察到的神经系统损伤可能会导致长期的，高水平的星形胶质细胞产生NO，这可能反映了主机试图抑制病毒复制。