The introduction of highly active antiretroviral therapy (HAART) in HIV-infected patients transformed HIV infection from a fatal condition into a manageable disease. However, recent evidence indicates that HIV- infected patients treated successfully with HAART develop age-associated pathologies at an accelerated rate, including cardiovascular disease, neurodegeneration and cancer. Many HIV-infected patients on HAART also show signs of persistent immune activation and accelerated immune aging with high levels of terminally differentiated (senescent) CD28- memory T cells accumulating at a young age. A similar premature aging syndrome occurs in chronic opiate and stimulant users who develop multi-system degenerative diseases in conjunction with symptoms of immune activation. We seek molecular insight into shared pathways linking HIV infection and drug abuse with chronic immune activation to develop novel therapies designed to slow accelerated immune aging and enhance the health span of HIV-infected drug users. We recently identified the NAD+-dependent deacetylase SIRT1 as a critical regulator of immune activation in HIV infection. SIRT1, a human homologue of the yeast sir2 enzyme, has been linked to prolonged lifespan in yeast and worms. The evidence that links SIRT1 to accelerated immune aging in HIV-infected drug users is threefold: 1) We showed that SIRT1 activity is inhibited by the HIV transactivator Tat, a process that leads to enhanced acetylation of downstream SIRT1 targets such as the immune stimulatory transcription factor NF-kappaB in infected T cells. 2) In unpublished preliminary studies, we find that SIRT1 protein expression is lost in CD28- senescent memory T cells, a finding tied to the altered metabolic state (enhanced glycolysis) of these cells. 3) The laboratory of Dr. Eric Nestler showed that cocaine, a powerful stimulant, activates SIRT1 expression in the nucleus accumbens in the brain, which triggers altered gene expression and enhanced drug reward. Here, we propose to test the model that HIV and drugs of abuse synergistically accelerate immune aging by reprogramming the transcriptional and metabolic profiles of T cells. We will test this model in a new in vitro system of T-cell senescence by adding drugs of abuse (stimulants, opiates) with and without HIV Tat to senescing T cells. We will also develop new technologies to measure key markers of immune activation and metabolism in primary T cells isolated from patients. Special emphasis lies on SIRT1 and posttranslational modifications of downstream transcription factors NF-kappaB, FoxO3A and HIF-1alpha. We expect that our studies will transform our understanding of immune aging in HIV-infected drug users by establishing novel links between HIV, abused substances and biological pathways of aging with direct therapeutic impact.
Emerging evidence suggests that the immune systems of HIV-infected individuals and those afflicted with drug abuse ages prematurely. We will perform detailed molecular studies at the interface of HIV infection, drug abuse and aging to identify potential new therapeutic strategies to slow the accelerated immune aging in HIV- infected drug users.
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