Interferon-gamma acutely induces calcium influx in human microglia.
The acute actions of the cytokine, interferon-gamma (IFN-gamma), on intracellular calcium [Ca(2+)](i) levels in human microglia were investigated. In the presence of a calcium-containing physiological solution (Ca(2+)-PSS), IFN-gamma caused a progressive increase in [Ca(2+)](i) to a plateau level with a mean rate of increase of 0.81 +/- 0.17 nM/s and mean amplitude of 102 +/- 12 nM (n = 67 cells). Washout of the cytokine did not alter the plateau established with IFN-gamma in Ca(2+)-PSS; however, introduction of a Ca(2+)-free PSS diminished [Ca(2+)](i) to baseline levels. The decrease in [Ca(2+)](i) with Ca(2+)-free PSS would indicate that the response to IFN-gamma was mediated by an influx pathway. This result was confirmed in separate experiments showing the lack of an induced change in [Ca(2+)](i) with IFN-gamma applied in Ca(2+)-free PSS. The increase in [Ca(2+)](i) induced in Ca(2+)-PSS was reduced to near baseline levels when the external solution contained low Cl(-) in the maintained presence of IFN-gamma suggesting that cellular depolarization inhibited the cytokine mediated entry pathway. The compound SKF96365, which blocks store operated influx of Ca(2+) in human microglia, was ineffective in altering the increase in [Ca(2+)](i), however, La(3+) completely inhibited the Ca(2+) response induced by IFN-gamma. Whole-cell patch clamp studies showed no effect of IFN-gamma to alter outward currents and inward rectifier K(+) currents. The influx of Ca(2+) may serve a signaling role in microglia linking IFN-gamma to functional responses of the cells to infiltrating T lymphocytes into the central nervous system (CNS) during inflammatory processes.
Franciosi
Sonia
S
Department of Pharmacology, University of British Columbia, Vancouver, British Columbia, Canada.
Choi
Hyun B
HB
Kim
Seung U
SU
McLarnon
James G
JG
D002118:Calcium / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology*; D007811:Lanthanum / Q000494:pharmacology; D017628:Microglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology; D013050:Spectrometry, Fluorescence / Q000379:methods
D002712:Chlorides; D007093:Imidazoles; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D007811:Lanthanum; D007371:Interferon-gamma; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium