Functional expression of multidrug resistance proteins in brain parenchyma:  Relevance to the pharmacology of HIV-infection in the brain.
Published: 2004
Language: eng
Number of pages: 247
Description: We further investigated the activity of MRP4/5 in MLS-9 cells by measuring export of 9-(2-phosphonylmethoxyethyl)adenine (PMEA), an established MRP4/5 substrate. PMEA efflux was rapid, ATP-dependent but not glutathione-dependent, and inhibited by MRP inhibitors: genistein, sulfinpyrazone, indomethacin and the nucleoside analog azidothymidine-monophosphate. Finally, we provide the first evidence that permeation of an antiretroviral drug (i.e., saquinavir) into microglia can be directly regulated by MRP transporter expression. Our results imply that the overall distribution of several classes of antiretroviral drugs, including nucleoside analogs and protease inhibitors can be highly regulated in cellular targets of HIV infection in the CNS.The development of "pharmacological resistance" to antiretroviral (AR) drugs used for the treatment of human immunodeficiency virus (HIV) infection is a serious limitation of current treatment regimens. In particular, cells that express high levels of membrane bound, energy-dependent drug transporters (e.g., ATP binding cassette transporter superfamily) may experience insufficient antiviral effect due to lowered intracellular drug concentrations. In the brain, microglia act as the primary cellular target of HIV infection. Once infected, microglia initiate inflammatory responses that result in neuronal cell death and act as a "hard to reach" pharmacological reservoir for the virus. At present, mechanisms governing the entry, distribution and exit of antiretroviral drugs in the central nervous system (CNS) are poorly understood. The overall intent of this project was to examine whether microglia can act as a "second barrier" to HIV therapies in the brain via expression of multidrug resistance proteins (MRPs). We examined the molecular expression and function of MRP1 through 6 in cultured microglia using a combination of molecular, biochemical, immunocytochemical and drug transport techniques. Our studies demonstrate that gene and protein products of several MRPs (i.e., MRP1, MRP4, and MRP5) are expressed and functionally active in cultured microglia. Uptake/accumulation of the MRP1 substrate vincristine by MLS-9 monolayers was saturable, ATP and glutathione-dependent, and significantly enhanced in the presence of MRP inhibitors: MK571, genistein, and sulfinpyrazone. Furthermore, we observed MRP1 localization at the plasma membrane, as well as in membrane vesicles.
Notes: Adviser:  Reina Bendayan.

Thesis (Ph.D.)--University of Toronto, 2004.

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Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5095.