As of 2010, an estimated 34 million persons worldwide were living with human immunodeficiency virus (HIV) infection (Word Health Organization and UN estimations). Early after primary infection, HIV enters the CNS and causes cognitive and motor impairment in 30-60% of infected individuals, even in the antiretroviral era. As infected individuals are living longer, the prevalence of neurological complications due to HIV CNS infection has increased. The cellular basis and mechanisms by which HIV-1 causes neuropathogenesis, or NeuroAIDS, are still not well understood. Astrocytes are key cells in the CNS that regulate BBB integrity, CNS inflammation, immune responses and neuronal survival. HIV only infects a small percentage of these cells and minimal to undetectable viral production is detected. Nevertheless, our data demonstrate for first time that HIV infected astrocytes, through gap junction channels and perhaps hemichannels, can amplify inflammation and CNS damage. We hypothesize that Cx43 containing gap junctions (GJ) and hemichannels (uHC) amplify intercellular signals generated in few HIV infected astrocytes to surrounding uninfected cells resulting in cellular toxicity, BBB disruption and secretion of DKK1 leading to the CNS dysfunction often observed in the HIV infected population even in the current antiretroviral era, where viral replication is minimal. To address this hypothesis we will expand upon our extensive Preliminary Studies demonstrating the participation of these channels in astrocyte, neuronal and blood brain barrier (BBB) dysfunction, as well in amplification of cell activation and inflammation in HIV infected astrocytes and in uninfected cells. These data will characterize novel pathways of HIV toxicity within the brain and will identify the role of these channels in CNS dysfunction. The results obtained from this proposal should indicate potential novel therapeutic targets to limit the devastating consequences of NeuroAIDS. PHS 398/2590 (Rev. 06/09) Page Continuation Format Page
As individuals with HIV are living longer due to the success of antiretroviral therapies, the prevalence of cognitive and motor deficits in this infected populatio is increasing. Astrocytes play a key role in maintaining CNS functions. However, their role in the pathogenesis of NeuroAIDS has not been well characterized, mainly due to the lack of specific molecular tools to examine HIV infection of astrocytes. The development of novel techniques to examine HIV infection of astrocytes in vivo and in vitro and their consequences in brain enable us to demonstrate that gap junction (GJ) and hemichannels (uHC) in astrocytes are important in the pathogenesis of NeuroAIDS. Our studies already showed that GJ and uHC of Connexin43 (Cx43) are critical to spread damage to neighboring cells despite the few numbers of HIV infected cells and minimal viral replication. We propose to expand these studies to characterize bystander dysregulation of uninfected astrocytes, neurons and brain endothelial cells. In addition, we will study the molecular mechanism by which GJ and uHC transmit and amplify toxic signals to neighboring cells by examining their activation and regulation. Lastly, we will expand upon our preliminary data obtained in vivo by using a novel animal model of bystander toxicity mediated by microinjection of few human HIV infected human astrocytes into the brain of animals with astrocytes genetically deleted for Cx43. We will evaluate using these animals, apoptosis and BBB disruption in neighboring cells around the microinjected HIV infected astrocytes. The results of these studies may provide information for the development of therapies to treat the neurologic dysfunctions in HIV infected individuals.
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