Interferon-gamma modulates cytosolic free calcium in human neutrophilic granulocytes.
To investigate the role of cytosolic free calcium ([Ca2+]i in interferon-gamma (IFN-gamma) pre-activation (priming) of human neutrophilic granulocytes (PMN) we used three different fluorescence methods, i.e. digital imaging of single, adherent, Fura-2 loaded cells, flow cytometric measurements of single, non-adherent, Fluo-3 loaded cells, and spectrofluorometry of Indo-1 loaded PMN in suspension. IFN-gamma increased the [Ca2+]i level in single, adherent PMN during the second phase of the fMLP response. The bacterial peptide fMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine) is a known stimulant of the calcium/inositol phosphate system. The [Ca2+]i increase was abolished in Ca(2+)-free test buffer. Furthermore, the baseline [Ca2+]i level was found to be slightly increased in IFN-gamma primed PMN as analysed with flow cytometry. On the other hand, these [Ca2+]i responses were not detectable with the other methods used. We suggest that IFN-gamma increases the plasma membrane permeability for calcium in PMN, and substantiate this by demonstrating compliance with a capacitative model for intracellular calcium regulation. Mathematical modeling also suggested that IFN-gamma primed human PMN may sequester 13% more Ca2+ than unprimed cells in fMLP-insensitive intracellular stores. Thus, the Ca2+ responses to IFN-gamma are modest and not easily detectable with some of the methods currently in use. They nevertheless explain why fMLP elicits brisker responses from PMN after IFN-gamma priming.
Røtnes
J S
JS
Department of Physiology, University of Oslo, Norway.
Aas
V
V
Iversen
J G
JG
D002118:Calcium / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D005434:Flow Cytometry; D016257:Fura-2; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008433:Mathematics; D008954:Models, Biological; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D013729:Terpenes; D004533:Egtazic Acid; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019284:Thapsigargin; D007371:Interferon-gamma; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2