Stimulation of calcium influx in HL60 cells by cholesteryl-modified homopolymer oligodeoxynucleotides.
Cholesteryl-modified 15-mer homopolymers of cytidine and thymidine phosphodiester oligodeoxynucleotides (chol-OdC15 and chol-OdT15), but not chol-modified heteropolymeric oligos or chol-modified phosphorothioate oligos, were found to increase cytosolic free Ca2+ in HL60 cells. A flow cytometer and the calcium-sensitive dye indo-1 were used to make multiparameter measurements on the HL60 cells. Chol-OdC15 (5-10 microM) triggered a rapid increase (within 1 min) in [Ca2+]i, with a subsequent slow decline to baseline over 15 min in the continuous presence of agonist. The effect was preserved after unloading the intracellular Ca2+ stores with caffeine and ryanodine. The effect was not sensitive to membrane depolarization by KCl (60 mM) or nimodipine, a dihydropyridine calcium channel antagonist. An increase in [Ca2+]i was absent in a Ca(2+)-free solution and was inhibited by the inorganic Ca2+ channel blocker Cd2+. The results suggest that Ca2+ influx activated by the chol-oligomer is probably mediated by receptor-operated Ca2+ channels. This effect may be due to direct binding of the chol-oligo to the channel or to induced conformational changes due to modification of the local microenvironment.
Saxon
M
M
Department of Medicine, Columbia University, College of Physicians and Surgeons, New York.
Schieren
I
I
Zhang
L M
LM
Tonkinson
J L
JL
Stein
C A
CA
D001483:Base Sequence; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000494:pharmacology; D003597:Cytosine Nucleotides / Q000494:pharmacology; D006801:Humans; D007951:Leukemia, Myeloid / Q000378:metabolism*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D013942:Thymine Nucleotides / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D015220:Calcium Channels; D003597:Cytosine Nucleotides; D009838:Oligodeoxyribonucleotides; D013942:Thymine Nucleotides; D002784:Cholesterol; D002118:Calcium