Changes in the expression and function of transport proteins within the blood-brain barrier (BBB) are known to occur during the natural aging process. In the present proposal, the effects of age on the expression and function of P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) in the brain microvessel endothelial cells that form the BBB will be evaluated. Both P-gp and MRP are efflux transport proteins that actively transport a wide variety of drugs and macromolecules out of the cell. The development of drug resistance in cancer cells has been attributed to over expression of P-gp and MRP. The expression of these same efflux transport proteins in normal cells, such as the brain microvessel endothelial cells that form the BBB, are believed to play a protective role, preventing the accumulation of potentially toxic compounds in the brain. The hypothesis of the current proposal is that the expression and/or functional activity of P-gp and MRP in the BBB changes as a function of age. Using brain microvessel endothelial cells harvested from female Fisher 344 rats at 3, and 18 months of age, the specific aims of the proposal are to: 1) examine age-related differences in the expression of P-gp and MRP in freshly isolated brain microvessel endothelial cells and primary cultured rat BMEC monolayers; and 2) examine age-related differences in the cellular accumulation and transcellular permeability of P-gp and MRP probes in confluent rat BMEC monolayers. Expression of P-gp and MRP will be evaluated at both the protein and RNA level using quantitative immunoblot and RT-PCR techniques, respectively. Functional activity of P-gp and MRP in the BBB will be assessed by examining the cellular accumulation and bi-directional differences in the permeability of selected P-gp and MRP probes in primary rat BMEC monolayers. Given the putative protective role of these two drug efflux transporters in the BBB, age- related alterations in the expression or function of P-gp and MRP could lead to increased susceptibility to endogenous factors and xenobiotics that impair central nervous system function.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Small Research Grants (R03)
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Special Emphasis Panel (ZAG1-BJS-3 (M9))
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University of Nebraska Medical Center
Schools of Pharmacy
United States
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Bachmeier, Corbin J; Trickler, William J; Miller, Donald W (2004) Drug efflux transport properties of 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM) and its fluorescent free acid, BCECF. J Pharm Sci 93:932-42
Zhang, Yan; Bachmeier, Corbin; Miller, Donald W (2003) In vitro and in vivo models for assessing drug efflux transporter activity. Adv Drug Deliv Rev 55:31-51
Sun, H; Miller, D W; Elmquist, W F (2001) Effect of probenecid on fluorescein transport in the central nervous system using in vitro and in vivo models. Pharm Res 18:1542-9
Elmquist, W F; Miller, D W (2001) The use of transgenic mice in pharmacokinetic and pharmacodynamic studies. J Pharm Sci 90:422-35