Stimulation of platelet-activating factor (PAF) receptors increases inositol phosphate production and cytosolic free Ca2+ concentrations in N1E-115 neuroblastoma cells.
Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine, PAF) has recently been recognized as an important mediator in the pathophysiology of brain injury. This study demonstrates that, in suspended populations of N1E-115 cells loaded with Indo-1, biologically relevant concentrations of PAF produce a rapid and transient elevation in cytosolic free calcium concentration ([Ca2+]i). Moreover, nanomolar concentrations of PAF increase [3H]-inositol phosphate production. Using lyso-PAF and the specific PAF-receptor antagonists BN52021 and BN50739, we show that these effects were mediated by stimulation of PAF receptors. Experiments performed in Ca2+ free medium show that PAF-induced [Ca2+]i increase is the result of an influx of Ca2+ and of the release of intracellular Ca2+ stores. Studies of Mn2+ influx argue in favour of additional pathways for the PAF-induced Ca2+ influx other than the pathway for the thapsigargin-induced Ca2+ influx. Using the whole-cell voltage-clamp technique, we observe that PAF induces an increase of Ltype Ca2+ current. However, the effects of La3+, nifedipine and KCl-induced depolarization on the PAF-induced [Ca2+]i increase suggest a minor participation of these voltage-gated Ca2+ channels in the response to PAF. Altogether the results point to the existence of a PAF-induced Ca2+ influx through receptor-operated Ca2+ permeant channels.
Diserbo
M
M
Centre de Recherches Emile Pardé, La Tronche, France.
Cand
F
F
Ziade
M
M
Verdetti
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002273:Carcinogens; D003470:Culture Media; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D007211:Indoles; D007295:Inositol Phosphates / Q000378:metabolism*; D007811:Lanthanum / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology; D010716:Phosphatidylinositols / Q000378:metabolism; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000187:drug effects*; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D002273:Carcinogens; D003470:Culture Media; D007211:Indoles; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D013729:Terpenes; C039351:platelet activating factor receptor; D008345:Manganese; D019284:Thapsigargin; D007811:Lanthanum; D000252:Calcium-Transporting ATPases; C048960:indo-1; D002118:Calcium