Éditeur(s) : HAL CCSD Wiley-Blackwell Wiley
Résumé : International audience
Rhodamine 123 is a fluorescent cationic dye commonly used as a mitochondrial probe and known or suspected to be transported by certain drug membrane transporters. The present study was designed to characterize the putative interactions of rhodamine 123 with human organic cation transporter (OCT) 1 and OCT2. Intracellular uptake of the dye was demonstrated to be enhanced in both hOCT1- and hOCT2-overexpressing HEK293 cells when compared with control HEK293 cells. This increase of rhodamine 123 influxes was found to be a saturable carrier-mediated process, with low K(m) values (K(m) = 0.54 μm and K(m ) = 0.61 μm for transport of the dye in hOCT1- and hOCT2-positive HEK293 cells, respectively). Known inhibitors of hOCT1 and hOCT2 activities such as verapamil, amitriptyline, prazosin, and quinine were next demonstrated to decrease rhodamine 123 accumulation in hOCT1- and hOCT2-overexpressing HEK293 cells. In addition, the dye was found to inhibit hOCT1- and hOCT2-mediated uptake of tetraethylammonium (TEA), a model substrate for both hOCT1 and hOCT2; rhodamine 123 appeared nevertheless to be a more potent inhibitor of hOCT1-mediated TEA transport (IC(50) = 0.37 μm) than of that mediated by hOCT2 (IC(50 ) = 61.5 μm). Taken together, these data demonstrate that rhodamine 123 is a high-affinity substrate for both hOCT1 and hOCT2. This dye may be therefore useful for fluorimetrically investigating cellular hOCT1 or hOCT2 activity, knowing, however, that other factors potentially contributing to cellular accumulation of rhodamine 123, including mitochondrial membrane potential or expression of the efflux transporter P-glycoprotein, have also to be considered.
ISSN: 0767-3981

inserm-00872840
http://www.hal.inserm.fr/inserm-00872840
DOI : 10.1111/j.1472-8206.2012.01071.x
PUBMED : 22913740

Éditeur(s) : HAL CCSD
Résumé : International audience
In vitro evaluation of P-glycoprotein (P-gp) inhibitory potential is now a regulatory issue during drug development, in order to predict clinical inhibition of P-gp and subsequent drug-drug interactions. Assays for this purpose, commonly based on P-gp-expressing cell lines and digoxin as a reference P-gp substrate probe, unfortunately exhibit high variability, raising thus the question of developing alternative or complementary tests for measuring inhibition of P-gp activity. In this context, the present study was designed to investigate the use of the fluorescent dye rhodamine 123 as a reference P-gp substrate probe for characterizing P-gp inhibitory potential of 16 structurally-unrelated drugs known to interact with P-gp. 14/16 of these P-gp inhibitors were found to increase rhodamine 123 accumulation in P-gp-overexpressing MCF7R cells, thus allowing the determination of their P-gp inhibitory potential, i.e., their half maximal inhibitor concentration (IC50) value towards P-gp-mediated transport of the dye. These IC50 values were in the range of variability of previously reported IC50 for P-gp and can be used for the prediction of clinical P-gp inhibition according to Food and Drug Administration (FDA) criteria, with notable sensitivity (80%). Therefore, the data demonstrated the feasibility of the use of rhodamine 123 for evaluating the P-gp inhibitory potential of drugs
Pharmaceutics

hal-01305488
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01305488
DOI : 10.3390/pharmaceutics8020012
PUBMED : 27077878