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Lou H, Ookhtens M, Stolz A, Kaplowitz N.
Chelerythrine stimulates GSH transport by rat Mrp2 (Abcc2)
expressed in canine kidney cells.
Am J Physiol Gastrointest Liver Physiol. 2003
Dec;285(6):G1335-44
Research Center for Liver Diseases, Keck School of Medicine,
University of Southern California, Los Angeles, California
90033, USA.
Rat multidrug resistant protein 2 (Mrp2; Abcc2), an
ATP-driven pump located on the canalicular domain of hepatocytes,
exports glutathione S-conjugates (GS-X) and GSH among its wide
variety of substrates. Previous studies have shown that
chelerythrine (CHEL), a quaternary benzophenanthridine cation,
reacts with GSH to form a reversible adduct under physiological
conditions. Here we report that CHEL can strongly stimulate GSH
efflux by Mrp2, when it is constitutively expressed in polarized
canine kidney cells, thereby leading to the depletion of
cellular GSH. Transepithelial transport experiments indicate
that Mrp2 transports GSH and CHEL with a 1:1 stoichiometry,
which can be readily inhibited by GS-bimane, a GS-X substrate
for Mrp2. Moreover, CHEL can block Mrp2-mediated leukotriene C4
uptake by membrane vesicles with an IC50 approximately 100
microM in the presence of GSH, but not S-methyl GSH or
ophthalmic acid. Thus the thiol group of GSH is required for
inhibition of Mrp2 in the presence of CHEL. Our results suggest
that CHEL stimulates GSH efflux by forming a reversible GS-CHEL
adduct, which is transported by Mrp2 and dissociates
extracellularly.
PMID: 12893631 |
