[Reversal effect of haloperidol on doxorubicin resistance and chloride channel inhibition in erythroleukemic cell K562/Dox].
OBJECTIVE
To investigate the reversal effect of haloperidol (Hal) on doxorubicin (Dox) resistance and its inhibition effect on P-glycoprotein and swelling-activated chloride channel in Dox-resistant erythro-leukemic cell line K562/Dox.


METHODS
Tumor cell proliferation was measured by LDH assay. mRNA expressions of P-glycoprotein (MDR1), glutathione S-transferase Pi (GSTpi) and MDR-associated protein (MRP) of K562/Dox treated with Hal were assayed by RT-PCR. Chloride-sensitive dye MQAE was loaded into K562/Dox cells and the intracellular fluorescence intensity was measured to evaluate the effect of Hal on chloride channel in swelling-activated K562/Dox cells. Coulter counter ZM and Channelyzer 256 were used to measure cell volume regulation.


RESULTS
Hal significantly reversed Dox resistance in K562/Dox cells after 12.50, 6.25 and 3.12 micromol/L Hal treatment, the chemosensitivity to Dox increased by 8.61, 4.35 and 2.25 times respectively. After treatment with Hal 12.50 micromol/L, MDR1 and MRP mRNA expression were gradually down-regulated in a time-dependent manner on d1-d3, reducing to 76.3% and 64.6% of the control level on d3 (P < 0.05), while GSTpi mRNA expression decreased by 66.1% (P < 0.05) on d1-d2, and began to recover on d3. The swelling-activated chloride channel and cell regulatory volume decreased (RVD) in K562/Dox cells were also inhibited by Hal. Under hypotonic challenge the cellular fluorescence intensity which represented chloride concentration declined by (34.46 +/- 5.91)%. After adding 6.25 micromol/L and 18.75 micromol/L Hal, the hypotonic challenge only caused decrease in fluorescence intensity by (24.43 +/- 3.25)% and (16.63 +/- 4.98)% (P < 0.01). RVD in hypotonic condition was (84.95 +/- 5.69)%. RVD under hypotonic condition with 6.25 micromol/L and 18.75 micromol/L Hal were (51.12 +/- 6.01)% and (39.51 +/- 4.79)% respectively (P < 0.01).


CONCLUSIONS
A nontoxic concentration of haloperidol can significantly reverse drug resistance through a multi-pathway effect, including down-regulating mRNA expressions of MDR, GSTpi and MRP, inhibition of swelling-activated chloride channel and RVD in K562/Dox cells.
Zhou
Jing-hong
JH
Department of Clinical Pharmacology, Affiliated Hospital, Academy of Military Medical Sciences, Beijing 100850, China. jhzhou662002@yahoo.com.cn
Wu
De-zheng
DZ
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis* / Q000235:genetics; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D018118:Chloride Channels / Q000187:drug effects*; D004317:Doxorubicin / Q000494:pharmacology*; D018432:Drug Resistance, Multiple / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000235:genetics; D006220:Haloperidol / Q000494:pharmacology*; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D020014:K562 Cells; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D018118:Chloride Channels; D004317:Doxorubicin; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; D006220:Haloperidol; D007527:Isoenzymes; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012333:RNA, Messenger; C496556:GSTP1 protein, human