title: Ca2+ priming during vitamin D-induced monocytic differentiation of a human leukemia cell line.
abstract: 1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) induces monocytic differentiation of the human promyelocytic leukemia line, HL-60, and enhances Ca2+ transport in target cells of the mineral metabolism system. Hence, we determined whether the steroid's maturational effect on HL-60 involves alterations of intracellular calcium [( Ca2+]i). We found that, as detected by indo-1 fluorescence, [Ca2+]i increases in a slow tonic manner from 99 +/- 11 nM in virgin HL-60 to 182 +/- 19 nM (p less than 0.001) in those treated with 1,25-(OH)2D3 for 24 h. The first apparent rise in [Ca2+]i occurs at between 6 and 12 h and parallels expression of alpha-thrombin and N-formyl-methionyl-leucyl-phenylalanine (fMLP) receptors. This increase in [Ca2+]i is derived from extracellular calcium as its reduction abolishes the effect. The increase in [Ca2+]i is associated with an increase in inositol trisphosphate-stimulated Ca2+ flux from intracellular stores. Interestingly, 1,25-(OH)2D3-mediated HL-60 differentiation as manifest by expression of the macrophage-specific antigen, 63D3, is not blocked by low extracellular calcium. In contrast, the fMLP-induced superoxide ion generation is diminished if the increase in [Ca2+]i is prevented. Furthermore, fMLP-stimulated signal transduction is also reduced by limiting the stimulation of [Ca2+]i during 1,25-(OH)2D3 treatment. Thus, although differentiation of HL-60 to the monocytic phenotype by 1,25-(OH)2D3 is Ca2+-independent, expression of response to regulatory stimuli requires priming of cellular Ca2+ stores. The latter appears to be induced by 1,25-(OH)2D3 via stimulated Ca2+ entry through the plasma membrane.
authors.affiliation: Department of Medicine, Jewish Hospital, Washington University Medical Center, St. Louis, Missouri 63110.
authors.forename: K A
authors.initials: KA
authors.lastname: Hruska
authors.forename: Z
authors.initials: Z
authors.lastname: Bar-Shavit
authors.forename: J D
authors.initials: JD
authors.lastname: Malone
authors.forename: S
authors.initials: S
authors.lastname: Teitelbaum
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015470:Leukemia, Myeloid, Acute; D009000:Monocytes / Q000166:cytology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology
chemical_list: D009240:N-Formylmethionine Leucyl-Phenylalanine; D002117:Calcitriol; D002118:Calcium