Since the introduction of the highly active antiretroviral combinatorial therapies for HIV (HAART) the pathogenesis of HIV infection is now more commonly a chronic, long-term infection that has dramatically changed the epidemiology of this disease. Long-term exposure to low levels of viral replication has unmasked susceptibilities to a number of cardiac and pulmonary diseases that are now more common causes of morbidity and mortality. For example, HIV-associated pulmonary arterial hypertension (HIV-PAH) PAH is approximately 25 times more prevalent among HIV infected individuals than in the general population. We have found that the HIV Tat protein promotes a number of pro-oxidative and pro-inflammatory responses that are not directly related to its function as a viral transcriptional regulator. For example, we and others have demonstrated that Tat induces oxidative stress via depletion of glutathione and alteration of manganese- dependent superoxide dismutase (MnSOD). In endothelial cells, the resultant increase in oxidants can promote a number of physiological responses such as inflammation, apoptosis and subsequent proliferation of apoptosis-resistant cells that can contribute to the occlusion of pulmonary vessels. Thus, we propose that Tat- induced oxidative stress has a central role in initiating the pathogenic cascade that ultimate leads to pulmonary vascular remodeling in HIV-PAH. In this application, we seek to examine the mechanisms whereby the HIV-1 Tat protein modulates sod2 expression thereby contributing to a state of oxidative stress. We have defined a Tat-sensitive Sp-responsive element (TSS) containing multiple binding sites for the oxidant sensitive Sp family of transcription factors in the regions of the sod2 promoter proximal (up to nucleotide -210) to the transcriptional start and have shown that Tat decreases the Sp1/Sp3 ratio on the TSS. Given that Sp3 has reduced transcriptional activity compared to Sp1 and an inhibitory domain that that represses transcription, this shift in occupancy of the promoter will result in alteration of sod2 transcription. Our hypothesis is that HIV-1 Tat dysregulates sod2 expression via modulation of Sp1 and Sp3 transcription factors and contributes to a state of oxidative stress during HIV infection. In order to address the hypothesis we have crafted a research plan that combines in vivo mouse models to examine the oxidative state in the lungs during HIV infection and in vitro mechanistic experiments to probe potential molecular mechanisms for how Tat alters the Sp1/Sp3 ratio on the sod2 promoter. Lastly we will leverage our current bank of bronchalveolar lavage (BAL) and blood biospecimens from HIV+ individuals with and without PAH to address whether in HIV-infected patients, to investigate oxidative stress in human biological specimens of HIV-PAH and to ask mechanistic questions regarding the modulation of sod2 in HIV infection.
With a combination of human specimens, animal and cell culture models we will address how the HIV viral protein Tat dysregulates expression of MnSOD (sod2) via modulation of the oxidant sensitive transcription factors, Sp1 and Sp3. The studies proposed in this application will use existing clinical specimens, mouse models and in vitro molecular tools to examine the mechanisms whereby this HIV protein influences oxidative stress that could contribute to pulmonary vascular remodeling in the pathogenesis of pulmonary hypertension associated with HIV. (End of Abstract)
