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Cocaine is one of the most widely abused drugs in the United
States; it is also considered a cofactor in human
immunodeficiency virus infection as a result of its frequent
association with such high risk behaviors as sharing
contaminated needles and practicing unsafe sex. Also
recognized is the role of cocaine on the modulation of the
immune response and its ability to potentiate HIV
replication and disease progression. However, the mechanism
by which cocaine mediates these effects remains ill-defined.
HAART (highly active antiretroviral therapy) controls viral
replication, significantly improving survival and quality of
life. It is widely recognized that adherence to HAART is not
easy. Recently it was recognized that P-glycoprotein (Pgp),
which is encoded by the MDR1 gene (multi-drug resistance),
acts as an efflux pump; one of its substrates is a protease
inhibitor (PI), a component of HAART. Our preliminary data
revealed that chronic cocaine users had increased levels of
Pgp expression on CD4+ T cells, CD8+ T cells, and monocytes.
In addition, CXCR4 (a major HIV-1 coreceptor) levels were
also increased. These results suggest that cocaine may also
play a role in the efficacy of HAART by reducing the
bioavailability of the protease inhibitor and by promoting
disease progression through the up-regulation of CXCR4. Our
study hypothesis is that cocaine primarily alters cytokine/chemokine
cascade function, consequently yielding up-regulation of Pgp
and CXCR4, which in turn leads to both the decreased
bioavailability of the PI and the promotion of HIV-1
replication, respectively. Our specific aims will address
this hypothesis in an effort to clarify the relationship
between cocaine use and the expression of Pgp and CXCR4. The
in vitro effects of cocaine on immunological cell function
and Pgp and CXCR4 expression will be examined in specific
aim 1 through microarray analysis, flow cytometry, and
Western blot analysis, among others. This will be followed
by specific aim 2, in which we are going to determine the
effects of PI and Pgp inhibitors on HIV-1 replication in
cells previously exposed to cocaine. Finally, in specific
aim 3, we will generate an MDR1 gene knockdown on T cells/monocytes
and determine its effect on CXCR4 expression and HIV-1
replication in the presence of PIs. At the conclusion of
this study, we will have significantly advanced our
understanding of the effects of cocaine on HIV-1
pathogenesis. Our long term goal is to provide a better
understanding of the effect of cocaine use on immunological
cells and HAART efficacy for the possible inclusion of Pgp
inhibitors in therapy regimens.
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