It has been shown that patients carrying HIV-1 accumulate damage to cells and tissues that are not directly infected by the virus itself (e.g. neurons). Importantly, these include changes known as HIV- Associated Neurodegenerative Disorder (HAND) leading to the loss of neuronal functions. HAND is an outstanding problem in the clinical management of HIV-1 patients, because suppression of infectious virus by c-ART does not completely block neurodegenerative changes. Neuropsychological studies disclose cognitive alteration (such as loss of Spatial and Declarative Memory) in a substantial proportion of HIV-1 infected patients, and analysis of post-mortem brain tissues isolated from HIV-1 patients treated with c- ART show signs of neurodegeneration. In the absence of HIV-1 infection of neurons, a number of mechanisms have been proposed for HAND, including indirect inflammatory effects in the CNS and direct effects of viral proteins (e.g. Tat) shed from activated HIV-1-infected cells. The fact that these viral proteins enter the neurons through several pathways suggest the presence of many competing mechanisms that can contribute to HAND, each of which has its advocates. Their relative contributions to clinical disease in vivo remain to be sorted out, and this is an outstanding problem in HIV research. Studies from other neurodegenerative diseases described the cAMP responsive-element binding (CREB)-1 protein as a Key Regulator of the Memory. These studies also showed that loss of CREB protein expression and phosphorylation contributes to the development of neurocognitive impairments such as Spatial and Declarative Memory Alteration. Recently, we have obtained data showing a clear-cut effect of HIV-1 Tat on CREB protein phosphorylation and function in vitro (primary human and mouse neurons and in the neuronal cell line, SH-SY5Y) and in vivo (in mice injected with Tat then treated with Rolipram [activator of CREB]) (see BACKGROUND AND PRELIMINARY RESULTS). This finding is exciting for two reasons: (1) A correlation between CREB protein and neurodegeneration has been well-established in the literature, suggesting that this may be a significant contributory mechanism in HAND; and (2) Agents are available which can specifically restore CREB protein levels and function, offering an opportunity to test directly the contribution of this mechanism in vivo in mice. Our hypothesis is that Tat contributes to neurodegeneration via reduction of mitochondrial function, mediated by a decrease in CREB protein activity. We propose to test this hypothesis in tissue culture cells and in vivo in mice, and verify the intermediate role of CREB protein using the specific CREB activator: Rolipram. Therefore, in this revised application, we asked more specific and focus questions that will allow us to perform additional in vitro and in vivo studies to determine the exact mechanisms used by Tat leading to the loss of Memory by focusing mainly on the Tat-CREB function and to restore this lost declarative memory and learning. Completion of these studies will determine for the first time involvement of HIV-1 Tat in cognitive disorders such as, Learning Deficit and Spatial & Declarative Memory Impairment that is commonly observed in HIV- 1 patients as well as in aged persons. Using an Intervention (Rolipram) approach to prevent CREB loss of functions will help establishing a new therapeutic strategy (high throughput screening) to mitigate cognitive impairments associated with HIV-1 infection in HIV/AIDS patients. (Since the relation between Tat and BDNF was amply studied, we will propose BDNF experiments to validate our hypothesis only). !
Sharing Plan Data, cell line and plasmids generated from this project will be made freely available to the scientific research community after the work is published. Tat plasmids, proteins or mice tissues (proteins or DNA) will be also made available and distributed when requested.
