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Expression and function of P-glycoprotein in human mesangial cells
1Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555.
Abstract:
P-glycoprotein (PGP), responsible for multidrug resistance (MDR) in cancer cells, is normally expressed in kidney proximal tubules and mesangium. PGP expression and function were studied in human mesangial cell cultures. MDR1 gene expression was demonstrated by reverse transcription-polymerase chain reaction. PGP expression was determined using MRK16 monoclonal antibody and its function was assessed by the efflux of rhodamine-123 (R123). R123 efflux had a half time of 25 +/- 5 s. Efflux was inhibited by cyclosporin A (10 microM), verapamil (10 microM), and vinblastine (100 microM) with half times of 380, 535, and 312 s, respectively. Incubation with MDR1-antisense oligonucleotide decreased R123 efflux (half time = 304 s). Verapamil, cyclosporin A, and PSC-833 augmented the cytotoxicity of Adriamycin by reducing the 50% maximal growth-inhibitory dose from 730 nM to 130, 110, and 90 nM, respectively. We conclude that human mesangial cells express MDR1 and demonstrate xenobiotic transport inhibitable by several known PGP substrates. Concomitant exposure of mesangial cells to PGP-transported drugs causes intracellular accumulation of toxic PGP substrates and ultimately damages the mesangial cells.
Insights
Human mesangial cells express P-glycoprotein (PGP), a protein linked to multidrug resistance (MDR). PGP function in these cells can be inhibited, potentially impacting drug efficacy and cellular damage.
Area of Science:
- Nephrology
- Cell Biology
- Pharmacology
Background:
- P-glycoprotein (PGP) mediates multidrug resistance (MDR) in cancer cells.
- PGP is normally expressed in kidney proximal tubules and mesangium.
Purpose of the Study:
- To investigate PGP expression and function in human mesangial cell cultures.
- To assess the impact of PGP substrates on mesangial cell viability.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) for MDR1 gene expression.
- Immunodetection of PGP using MRK16 monoclonal antibody.
- Rhodamine-123 (R123) efflux assay to assess PGP function.
Main Results:
- Human mesangial cells express functional PGP, demonstrated by R123 efflux.
- R123 efflux was inhibited by cyclosporin A, verapamil, and vinblastine.
- PGP inhibition augmented Adriamycin cytotoxicity, reducing the 50% maximal growth-inhibitory dose.
Conclusions:
- Human mesangial cells express MDR1 and exhibit xenobiotic transport inhibitable by known PGP substrates.
- Exposure to PGP-transported drugs can lead to intracellular accumulation of toxic substrates.
- This accumulation ultimately damages mesangial cells, suggesting a role in kidney drug toxicity.