Abstract
Members of the multidrug resistance protein (MRP/ABCC) subfamily of ATP-binding cassette proteins transport a wide array of anionic compounds, including sulfate, glucuronide, and glutathione (GSH) conjugates. The present study tested the ATP-dependent vesicular transport of leukotriene C4 and 17β-estradiol 17-(β-d-glucuronide) (E217βG) mediated by the MRP1 and MRP2 transporters in the presence of six potential modulators from three different classes of GSH-conjugated catechol metabolites: the ecstasy metabolite 5-(glutathion-S-yl)-N-methyl-α-methyldopamine (5-GS-N-Me-α-MeDA), the caffeic acid metabolite 2-(glutathion-S-yl)-caffeic acid (2-GS-CA), and four GSH conjugates of 2-hydroxy (OH) and 4-OH estrogens (GS estrogens). MRP1-mediated E217βG transport was inhibited in a competitive manner with a relative order of potency of GS estrogens (IC50 <1 μM) > 2-GS-CA (IC50 3 μM) > 5-GS-N-Me-α-MeDA (IC50 31 μM). MRP2-mediated transport was inhibited with a similar order of potency, except the 2-hydroxy-4-(glutathion-S-yl)-estradiol and 4-hydroxy-2-(glutathion-S-yl)-estradiol conjugates were approximately 50- and 300-fold less potent, respectively. Transport activity was unaffected by N-acetylcysteine conjugates of N-Me-α-MeDA and CA. The position of GSH conjugation appears important as all four GS estrogen conjugates tested were potent inhibitors of MRP1 transport, but only the 2-hydroxy-1-(glutathion-S-yl)-estradiol and 2-hydroxy-1-(glutathion-S-yl)-estrone conjugates were potent inhibitors of MRP2-mediated transport. In conclusion, we have identified three new classes of MRP1 and MRP2 modulators and demonstrated that one of these, the estrogen conjugates, shows unanticipated differences in their interactions with the two transporters.
Footnotes
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This work was supported by Grant MOP-10519 from the Canadian Institutes of Health Research (CIHR). A.J.S. is the recipient of a CIHR Doctoral Research Award and a Queen's University Robert John Wilson Fellowship. S.P.C.C. is the recipient of a Canada Research Chair in Cancer Biology and is the Queen's University Bracken Chair in Genetics and Molecular Medicine.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.107.019661.
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ABBREVIATIONS: MRP, multidrug resistance protein; ABC, ATP-binding cassette; LTC4, leukotriene C4; GSH, glutathione; E217βG, 17β-estradiol 17-(β-d-glucuronide); MDMA, methylenedioxymethamphetamine; CA, caffeic acid, 3,4-dihydroxycinnaminic acid; OH, hydroxy; N-Me-α-MeDA, N-methyl-α-methyldopamine; HEK, human embryonic kidney; 5-GS-N-Me-α-MeDA, 5-(glutathione-S-yl)-N-methyl-α-methyldopamine; 2-GS-CA, 2-(glutathion-S-yl)-caffeic acid; 2-OH-1-GS-E2, 2-hydroxy-1-(glutathion-S-yl)-17β-estradiol; 2-OH-1-GS-E1, 2-hydroxy-1-(glutathion-S-yl)-estrone; 2-OH-4-GS-E2, 2-hydroxy-4-(glutathion-S-yl)-17β-estradiol; 4-OH-2-GS-E2, 4-hydroxy-2-(glutathion-S-yl)-17β-estradiol; LY475776, (N-(4-azido-3-phenyl)-2-[3-(9-chloro-3-methyl-4-ozo-4H-isoxazolo[4,3-c]quinolin-5-yl)-cyclohexyl]-acetamide); MK571, 3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid; GS, (glutathion-S-yl).
- Received November 6, 2007.
- Accepted December 12, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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