Effects of dietary flavonoids on the transport of cimetidine via P-glycoprotein and cationic transporters in Caco-2 and LLC-PK1 cell models

Abstract

1. The hypotheses tested were to study cimetidine as a substrate of P-glycoprotein (P-gp) and organic cation transport systems and the modulatory effects of eight flavonoid aglycones and glycosides on these transport systems using Caco-2 and LLC-PK1 cells.

2. Transport and uptake experiments of (20 µM) ³H-cimetidine were performed with and without co-exposure to quercetin, quercetrin, rutin, naringenin, naringin, genistein, genistin, and xanthohumol. Co-treatment decreased basolateral to apical (B to A) permeability (P_app) of cimetidine from 2.02 to 1.24 (quercetin), 1.06 (naringenin), 1.24 (genistein), and 0.96 (xanthohumol) × 10⁻⁶ cm s⁻¹ in Caco-2 cells and from 10.76 to 1.65 (quercetin), 2.05 (naringenin), 2.88 (genistein), and 1.95 (xanthohumol) × 10⁻⁶ cm s⁻¹ in LLC-PK1 cells. Genistin significantly reduced B to A P_app of cimetidine to 1.24 × 10⁻⁶ cm s⁻¹ in Caco-2 cells. Basolateral intracellular uptake rate of cimetidine was enhanced 145–295% when co-treated with flavonoids. Co-treatment with P-glycoprotein and organic cation transporter inhibitors, verapamil and phenoxybenzamine, resulted in reduced B to A permeability and slower basolateral intracellular uptake rate of cimetidine. Intracellular uptake rate of ¹⁴C-tetraethylammonium (TEA) was reduced in the presence of quercetin, naringenin and genistein in LLC-PK1 cells.

3. In conclusion, quercetin, naringenin, genistein, and xanthohumol reduced P-gp-mediated transport and increased the basolateral uptake rate of cimetidine. Quercetin, naringenin, genistein, but not xanthohumol, reduced intracellular uptake rate of TEA in LLC-PK1 cells. These results suggest that flavonoids may have potential to alter the disposition profile of cimetidine and possibly other therapeutics that are mediated by P-gp and/or cation transport systems.

Keywords::

• Caco-2 cells
• LLC-PK1 cells
• cimetidine
• flavonoids
• P-glycoprotein

Acknowledgements

The authors acknowledge Dr Cristobal Miranda for his helpful comments and suggestions. This publication was made possible by NIH grants AT00853, CA090890 and ES00210. AT00853 was from the National Center for Complementary and Alternative Medicine (NCCAM) and the contents are solely the responsibility of the authors and do not necessarily represent the official view of NCCAM, or the National Institutes of Health.