Chalcogenopyrylium dyes as inhibitors/modulators of P-glycoprotein in multidrug-resistant cells.
A series of chalcogenopyrylium dyes were evaluated as modulators/inhibitors of P-glycoprotein (Pgp). Their ability to inhibit verapamil (VER)-dependent ATPase activity (IC(50) values) in lipid-activated, mouse Cys-less mdr3 Pgp was determined. Their ability to promote calcein-AM (CAM) uptake in MDCKII-MDR1 cells and their capacity to be transported by Pgp in monolayers of MDCKII-MDR1 cells were also evaluated. The chalcogenopyrylium dyes promoted CAM uptake with values of EC(50) between 5 x 10(-6) and 3.5 x 10(-5)M and 7 of the 9 dyes examined in transport studies were substrates for Pgp with efflux ratios (P(BA/AB)) between 14 and 390. Binding of three compounds (1-S, 3-S, and 4-S) to Pgp was also assessed by fluorescence. These three thiopyrylium dyes showed increased fluorescence upon binding to Pgp, giving apparent binding constants, K(app), on the order of 10(-7) to 10(-6)M. Compound 8-Te was particularly intriguing since it appeared to influence Pgp at low micromolar concentrations as evidenced by its influence on VER-stimulated ATPase activity (IC(50) of 1.2 x 10(-6)M), CAM uptake (EC(50) of 5.4 x 10(-6)M), as well as [(3)H]-vinblastine transport by Pgp in cells (IC(50) of 4.3 x 10(-6)M) and within inside-out membrane vesicles (IC(50) of 9.6 x 10(-6)M). Yet, Pgp did not influence the distribution of 8-Te in MDCKII-MDR1 monolayers suggesting that 8-Te may bind to an allosteric site.
Drug Disposition, Eli Lilly and Company, Indianapolis, IN 46285, USA.
Geri A
GA
Sawada
Thomas J
TJ
Raub
J
J
William Higgins
Nancy K
NK
Brennan
Teiah M
TM
Moore
Gregory
G
Tombline
Michael R
MR
Detty
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002121:Calcium Channel Blockers / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D016764:Cell Polarity; D002478:Cells, Cultured; D018011:Chalcogens / Q000737:chemistry*; D004285:Dogs; D018432:Drug Resistance, Multiple; D005452:Fluoresceins / Q000737:chemistry / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D014700:Verapamil / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002121:Calcium Channel Blockers; D018011:Chalcogens; D005452:Fluoresceins; D005456:Fluorescent Dyes; C085925:calcein AM; D014700:Verapamil; D000251:Adenosine Triphosphatases