TY - JOUR
T1 - Lysosomal accumulation of drugs in drug-sensitive MES-SA but not multidrug-resistant MES-SA/Dx5 uterine sarcoma cells
AU - Wang, Exing
AU - Lee, Michele D.
AU - Dunn, Kenneth W.
PY - 2000
Y1 - 2000
N2 - Sequestration of drugs in intracellular vesicles has been associated with multidrug-resistance (MDR), but it is not clear why vesicular drug accumulation, which depends upon intracellular pH gradients, should be associated with MDR. Using a human uterine sarcoma cell line (MES-SA) and a doxorubicin (DOX)-resistant variant cell line (Dx-5), which expresses p- glycoprotein (PGP), we have addressed the relationship between multidrug resistance, vesicular acidification, and vesicular drug accumulation. Consistent with a pH-dependent mechanism of vesicular drug accumulation, studies of living cells vitally labeled with multiple probes indicate that DOX and daunorubicin (DNR) predominately accumulate in lysosomes, whose lumenal pH was measured at < 4.5, but are not detected in endosomes, whose pH was measured at 5.9. However, vesicular DOX accumulation is more pronounced in the drug-sensitive MES-SA cells and minimal in Dx5 cells even when cellular levels of DOX are increased by verapamil treatment. While lysosomal accumulation of DOX correlated well with pharmacologically induced differences in lysosome pH in MES-SA cells, lysosomal accumulation was minimal in Dx5 cells regardless of lysosomal pH. We found no differences in the pH of either endosomes or lysosomes between MES-SA and Dx5 cells, suggesting that, in contrast to other MDR cell systems, the drug-resistant Dx5 cells are refractory to pH-dependent vesicular drug accumulation. These studies demonstrate that altered endomembrane pH regulation is not a necessary consequence of cell transformation, and that vesicular sequestration of drugs is not a necessary characteristic of MDR. (C) 2000 Wiley-Liss, Inc.
AB - Sequestration of drugs in intracellular vesicles has been associated with multidrug-resistance (MDR), but it is not clear why vesicular drug accumulation, which depends upon intracellular pH gradients, should be associated with MDR. Using a human uterine sarcoma cell line (MES-SA) and a doxorubicin (DOX)-resistant variant cell line (Dx-5), which expresses p- glycoprotein (PGP), we have addressed the relationship between multidrug resistance, vesicular acidification, and vesicular drug accumulation. Consistent with a pH-dependent mechanism of vesicular drug accumulation, studies of living cells vitally labeled with multiple probes indicate that DOX and daunorubicin (DNR) predominately accumulate in lysosomes, whose lumenal pH was measured at < 4.5, but are not detected in endosomes, whose pH was measured at 5.9. However, vesicular DOX accumulation is more pronounced in the drug-sensitive MES-SA cells and minimal in Dx5 cells even when cellular levels of DOX are increased by verapamil treatment. While lysosomal accumulation of DOX correlated well with pharmacologically induced differences in lysosome pH in MES-SA cells, lysosomal accumulation was minimal in Dx5 cells regardless of lysosomal pH. We found no differences in the pH of either endosomes or lysosomes between MES-SA and Dx5 cells, suggesting that, in contrast to other MDR cell systems, the drug-resistant Dx5 cells are refractory to pH-dependent vesicular drug accumulation. These studies demonstrate that altered endomembrane pH regulation is not a necessary consequence of cell transformation, and that vesicular sequestration of drugs is not a necessary characteristic of MDR. (C) 2000 Wiley-Liss, Inc.
UR - http://www.scopus.com/inward/record.url?scp=0033921304&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033921304&partnerID=8YFLogxK
U2 - 10.1002/1097-4652(200008)184:2<263::AID-JCP15>3.0.CO;2-F
DO - 10.1002/1097-4652(200008)184:2<263::AID-JCP15>3.0.CO;2-F
M3 - Article
C2 - 10867652
AN - SCOPUS:0033921304
SN - 0021-9541
VL - 184
SP - 263
EP - 274
JO - Journal of Cellular Physiology
JF - Journal of Cellular Physiology
IS - 2
ER -