Berman Joan W, Carvallo Loreto, Buckner Clarisa M, Luers Aimée, Prevedel Lisa, Bennett Michael V, Eugenin Eliseo A
Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA.
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA.
J Neuroinflammation. 2016 Mar 2;13(1):54. doi: 10.1186/s12974-016-0510-1.
HIV-associated neurocognitive disorders (HAND) are a major complication in at least half of the infected population despite effective antiretroviral treatment and immune reconstitution. HIV-associated CNS damage is not correlated with active viral replication but instead is associated with mechanisms that regulate inflammation and neuronal compromise. Our data indicate that one of these mechanisms is mediated by gap junction channels and/or hemichannels. Normally, gap junction channels shutdown under inflammatory conditions, including viral diseases. However, HIV infection upregulates Connexin43 (Cx43) expression and maintains gap junctional communication by unknown mechanism(s).
Human primary astrocytes were exposed to several HIV proteins as well as to HIV, and expression and function of Connexin43- and Connexin30-containing channels were determined by western blot, immunofluorescence, microinjection of a fluorescent tracer and chromatin immunoprecipitation (ChIP).
Here, we demonstrate that HIV infection increases Cx43 expression in vivo. HIV-tat, the transactivator of the virus, and no other HIV proteins tested, increases Cx43 expression and maintains functional gap junctional communication in human astrocytes. Cx43 upregulation is mediated by binding of the HIV-tat protein to the Cx43 promoter, but not to the Cx30 promoter, resulting in increased Cx43 messenger RNA (mRNA) and protein as well as gap junctional communication.
We propose that HIV-tat contributes to the spread of intracellular toxic signals generated in a few HIV-infected cells into surrounding uninfected cells by upregulating gap junctional communication. In the current antiretroviral era, where HIV replication is often completely suppressed, viral factors such as HIV-tat are still produced and released from infected cells. Thus, blocking the effects of HIV-tat could result in new strategies to reduce the damaging consequences of HIV infection of the CNS.
尽管有有效的抗逆转录病毒治疗和免疫重建，但至少一半的感染人群中，HIV相关神经认知障碍（HAND）仍是主要并发症。HIV相关的中枢神经系统损伤与活跃的病毒复制无关，而是与调节炎症和神经元损伤的机制有关。我们的数据表明，其中一种机制是由缝隙连接通道和/或半通道介导的。正常情况下，缝隙连接通道在包括病毒疾病在内的炎症条件下会关闭。然而，HIV感染会上调连接蛋白43（Cx43）的表达，并通过未知机制维持缝隙连接通讯。
将人原代星形胶质细胞暴露于几种HIV蛋白以及HIV中，通过蛋白质免疫印迹、免疫荧光、荧光示踪剂显微注射和染色质免疫沉淀（ChIP）来确定含连接蛋白43和连接蛋白30的通道的表达和功能。
在此，我们证明HIV感染会在体内增加Cx43的表达。病毒反式激活因子HIV-tat，而非其他测试的HIV蛋白，会增加人星形胶质细胞中Cx43的表达并维持功能性缝隙连接通讯。Cx43的上调是由HIV-tat蛋白与Cx43启动子结合介导的，而非与Cx30启动子结合，从而导致Cx43信使核糖核酸（mRNA）和蛋白质增加以及缝隙连接通讯增强。
我们提出，HIV-tat通过上调缝隙连接通讯，促使少数受HIV感染细胞中产生的细胞内毒性信号扩散到周围未感染细胞中。在当前抗逆转录病毒时代，HIV复制常常被完全抑制，而HIV-tat等病毒因子仍会从受感染细胞中产生和释放。因此，阻断HIV-tat的作用可能会带来减少HIV感染中枢神经系统破坏性后果的新策略。
