Tat-Mediated Brain Endothelial Cell Dysfunction

Impaired function of the brain vasculature can contribute to HIV trafficking into the CNS and the development of neurodegenerative changes associated with HIV infection. Indeed, activation or dysfunction of brain microvascular endothelial cells (BMEC) can lead to the breakdown ofthe blood-brain barrier (BBB), induction of inflammatory responses, and provide an entry route for the HIV into the CNS. The leading hypothesis of our research is that the viral gene product, HIV Tat protein, can be responsible for BMEC injury and impaired function of the BBB. Furthermore, we hypothesize that alterations of redox balance may be the common denominator of Tat-induced activation and dysfunction ofBMEC. In support of these hypotheses, we obtained strong evidence that Tat treatment can dramatically downregulate peroxisome proliferator activated receptor (PPAR) activation and thus suppress physiological functions of these critical anti-inflammatory nuclear receptors. This research proposal will focus on the consequences of Tat-induced alterations of PPAR activation, namely, overexpression of proinflammatory genes, dysregulation of junctional protein expression, and disturbances of endothelial barrier function. In addition, we hypothesize that Tat-induced alterations of BMEC redox status can lead to up regulation of the efflux transport systems on the brain endothelium and thus prevent an effective anti-HIV therapy in the CNS. The proposed research combines elements of clinical approaches, such as disruption of the BBB and the development of drug resistance, with molecular and vascular biology. It is based on the unique and innovative co-cultures of human brain endothelial cells with astrocytic cell lines which produce Tat (the SVGA-Tat cells). In addition, part of the project involves animal studies. The long-term goals of this proposal are to determine the mechanisms responsible for Tat-induced injury to BMEC, disruption of the BBB and HIV entry into the CNS. In a broader aspect, this proposal will contribute to better knowledge of how injury to brain endothelium can contribute to the development ofneuroAIDS.