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Updated: Aug 17, 2026
Purification of Mouse Brain Vessels
Published on: November 10, 2015
Expression of multidrug resistance-associated protein (MRP) in brain microvessel endothelial cells
H Huai-Yun1, D T Secrest, K S Mark
1Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha 68198-6025, USA.
Abstract:
Multidrug resistance-associated protein (MRP) is a recently identified drug efflux transport system that actively transports organic acids and selected glucuronide or glutathione conjugates out of the cell. The current study presents, for the first time, both functional and biochemical data demonstrating the presence of MRP in the brain microvessel endothelial cells that form the blood-brain barrier (BBB). Using known MRP inhibitors, such as indomethacin and probenecid, fluorescein accumulation in primary cultured bovine brain microvessel endothelial cell (BBMEC) monolayers was significantly enhanced compared to control. The specificity of the MRP inhibitors on cellular fluorescein accumulation was confirmed using both MRP positive (Panc-1) and MRP negative (KBv) cell lines. Furthermore, western blot analysis using a specific antibody for MRP (MRPm6) and RT-PCR studies using a complementary sequence probe for human MRP demonstrate the expression of MRP in BBMEC. Previous studies have demonstrated the significance of the P-glycoprotein drug efflux transporter in the BBB. Given its function as a drug efflux transport system, it is anticipated that MRP in the BBB will also have an important role in limiting the exposure of the brain to many endogenous and exogenous compounds, including both toxic and therapeutic agents.
Insights
Multidrug resistance-associated protein (MRP) is present in brain endothelial cells forming the blood-brain barrier. This MRP transporter may limit the brain
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Multidrug resistance-associated protein (MRP) is an efflux transporter system.
- The blood-brain barrier (BBB) protects the brain from harmful substances.
- P-glycoprotein is a known efflux transporter at the BBB.
Purpose of the Study:
- To investigate the presence and function of MRP in brain microvessel endothelial cells (BMECs).
- To determine if MRP contributes to the efflux transport at the BBB.
Main Methods:
- Primary cultured bovine brain microvessel endothelial cell (BBMEC) monolayers.
- Functional assays using MRP inhibitors (indomethacin, probenecid) and fluorescein.
- Biochemical validation using Western blot and RT-PCR for MRP expression.
Main Results:
- MRP inhibitors significantly increased fluorescein accumulation in BBMEC monolayers.
- MRP expression was confirmed at both protein (Western blot) and mRNA (RT-PCR) levels in BBMEC.
- Inhibitor specificity was confirmed using MRP-positive and MRP-negative cell lines.
Conclusions:
- This study provides the first functional and biochemical evidence for MRP in the BBB.
- MRP likely plays a role in limiting the brain's exposure to various compounds.
- MRP represents a significant efflux transporter at the BBB, alongside P-glycoprotein.
