[Effect of intracellular acidification on drug resistance of leukemia cells with high P-glycoprotein expression].
OBJECTIVE
To investigate the impact of intracellular acidification (IA) on drug resistance of leukemia cells with high P-glycoprotein (P-gp) expression, and to provide a new method for the reversing of multidrug resistance (MDR).


METHODS
Real-time PCR was used to determine the expression level of mdr1 gene, and the leukemia cells with high P-gp expression were selected. The specific inhibitor of Na+/H+ exchanger 1 and the "high K+" buffer were used to acidify the cells, and the confocal laser microscopy was used to determine the intracellular pH (pHi) and effect of IA on the accumulation of doxorubicin. The MTT method was used to determine the effect of IA on the cell viability. The flow cytometry was used to detect the effect of IA on the P-gp function, and Western blotting was used to determine the effect of IA on the expression of P-gp.


RESULTS
The pHi was decreased to 7.0, and compared with that of control the mdr1 mRNA expression was decreased to (53.2+/-11.0)% after 1 h, and to (16.6+/-7.0)% after 3 h treatment. The P-gp expression was decreased to (56.0+/-9.0)% of the control after 3 h treatment. The accumulation of Rh123 was 71.03+/-0.47 at pHi 7.0, which was increased obviously as compared to the control group 20.07+/-0.39. The increased accumulation of doxorubicin was also observed by confocal laser microscopy.


CONCLUSIONS
The expression and function of P-gp on the patients cells are inhibited by IA.
Li
Qing-hua
QH
State key Laboratory of Experimental Hematology, Institute of Hematology and Blood Diseases Hospital, CAMS & PUMC, Tianjin 300020, China.
Lu
Ying
Y
Jin
Wei-na
WN
Lin
Ya-ni
YN
Hu
Rong-hua
RH
Zhu
Xiao-fan
XF
Wang
Jian-xiang
JX
Pang
Tian-xiang
TX
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D004317:Doxorubicin / Q000493:pharmacokinetics; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007938:Leukemia / Q000188:drug therapy / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D013450:Sulfones / Q000494:pharmacology; D014407:Tumor Cells, Cultured
C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D006146:Guanidines; D012333:RNA, Messenger; D013450:Sulfones; C093373:cariporide; D004317:Doxorubicin