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Multidrug resistance-associated protein-1 functional activity in Calu-3 cells.
K O Hamilton1, E Topp, I Makagiansar
1Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, Kansas 66047-3729, USA.
The Journal of Pharmacology and Experimental Therapeutics
|August 16, 2001
Summary
Calu-3 cells exhibit multidrug resistance-associated protein-1 (MRP1) efflux pump activity, though it is less dominant than P-glycoprotein (Pgp) efflux. This study characterizes MRP1 function in this bronchial epithelial cell model.
Area of Science:
- Pharmacology
- Cell Biology
- Drug Transport
Background:
- Bronchiolar epithelial cells play a crucial role in lung defense and drug disposition.
- Efflux pumps, such as multidrug resistance-associated protein-1 (MRP1) and P-glycoprotein (Pgp), significantly influence cellular drug concentrations.
- Understanding efflux pump activity in airway epithelial models is vital for predicting drug behavior in the lungs.
Purpose of the Study:
- To investigate the presence and functional activity of MRP1 in the Calu-3 human bronchiolar epithelial cell line.
- To determine the relative contribution of MRP1 and Pgp to the efflux of substrates in Calu-3 cells.
- To characterize the localization and functional characteristics of MRP1 in this in vitro model.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) to confirm MRP1 gene expression.
- Indirect immunofluorescence to determine the subcellular localization of MRP1 and Pgp.
- Calcein accumulation and efflux assays using specific inhibitors (indomethacin, probenecid, cyclosporin A, MK571) and energy depletion.
- Etoposide efflux studies utilizing a panel of transporter inhibitors.
Main Results:
- MRP1 gene expression and basolateral membrane localization were confirmed in Calu-3 cells.
- MRP1 substrate (calcein) accumulation increased with MRP1 inhibitors and energy depletion, indicating functional activity.
- Calcein efflux was significantly reduced by MRP1 inhibitors, and net secretion was enhanced.
- Etoposide efflux was predominantly mediated by Pgp, with a minor contribution from MRP1.
- Calu-3 cells exhibit functional MRP1 activity, but Pgp-mediated efflux is the dominant pathway.
Conclusions:
- The Calu-3 cell line expresses functional MRP1, localized to the basolateral membrane.
- While MRP1 contributes to efflux in Calu-3 cells, Pgp-mediated transport is the primary efflux mechanism.
- These findings provide valuable insights into drug transport mechanisms in an in vitro model of human bronchiolar epithelium.