Novel role of occludin and pericytes in ischemic stroke in HIV infection

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 DESCRIPTION (provided by applicant): Heart, lung, and/or blood (HBL) complications of HIV infection are the emerging problem in HIV-related pathology. In the current proposal, we will study the mechanisms of HIV replication in cerebrovascular pericytes, addressing fundamental mechanistic questions focused on the impact of HIV infection on vascular tissue dysfunction contributing to the development of ischemic stroke. The integrity and functionality of the blood-brain barrier (BBB) are maintained by tight junctions (TJs) and the close interface between the cells of the neurovascular units, including pericytes interacting with microvascular endothelial cells. While cerebrovascular pericytes are arguably the most understudied cells of vascular tissue, recent literature reports provide compelling evidence on their involvement in the pathogenesis of stroke. In addition, we reported that they are susceptible to HIV infection, negatively affecting the integrity of the vascular endothelium. Our recently obtained critical preliminary data indicate that HIV replication in cerebrovascular pericytes is inversely correlated with the levels TJ protein occludin. The present application is built on these novel findings and we propose that cellular levels of occludin regulate HIV replication in cerebrovascular pericytes and thus influence the development of ischemic stroke in HIV-infected brain. Mechanistically, we identified that occludin has an NADH oxidase activity, resulting in increased cellular pool of NAD+. In Aim 1, we hypothesize that this activity leads to activation of sirtuin 1 (SIRT1), an NAD(+)-dependent deacetylase, which then suppresses activation of NF-κB and inhibits HIV replication in cerebrovascular pericytes. In Aim 2, we will focus on the role of occludin as a factor that limits a late stage of HIV replication by interfering with the ESCRT (endosomal complex required for transport) machinery, which is responsible for HIV budding and release. These studies are supported by another set of our exciting preliminary findings, indicating that occludin can interfere with ALIX, an early-acting ESCRT factor. While increased cellular occludin protects against HIV replication, an opposite effect is observed by decreased occludin levels. This is important because occludin upregulation in HIV infection is highly unique to cerebrovascular pericytes, with other cell types responding to infection by decreasing levels of this protein. Therefore, Aim 3 of our proposal is focused on an animal model of ischemic stroke in which we will utilize novel pericyte and occludin deficient mice infected with recently developed mouse-tropic EcoHIV strain. The proposed research is highly innovative by its focus on novel mechanisms to understand and control the mechanisms and pathogenesis underlying the development of HBL conditions. The completion of this proposal has the potential to change our understanding of the role of occludin and vascular pericytes in HIV infection and its HBL complications, including stroke.