Cholesterol modulates PAF-stimulated Ca2(+)-mobilization in monocytic U937 cells.
We investigated the effect of cellular cholesterol content on platelet activating factor (PAF)-stimulated Ca2+ mobilization in the human monocytic cell line U937. When cholesterol auxotroph U937 cells were depleted of cellular cholesterol by a 48-h incubation in delipidated medium, a 40% reduction in the PAF (100 nM)-stimulated increase in cytosolic Ca2+ concentration was seen. Ca2+ mobilization following stimulation with LTD4 (10 nM) or ATP (10 microM) was not affected. Addition of LDL (100 micrograms/ml, 24 h) to the delipidated medium completely recovered cellular cholesterol content and PAF-induced Ca2+ mobilization. These two LDL effects had very similar time- and dose-dependences. Partial recoveries of PAF-induced Ca2+ mobilization, seen after addition of pure cholesterol dissolved in ethanol (30 micrograms/ml, 24 h) or acetyl-LDL (100 micrograms/ml, 24 h), were associated with partial recoveries of cellular cholesterol content. Our results indicate that cellular cholesterol influences PAF-stimulated events in monocytic cells.
Aepfelbacher
M
M
Institut für Prophylaxe und Epidemiologie, Universität München, F.R.G.
Hrboticky
N
N
Lux
I
I
Weber
P C
PC
D000255:Adenosine Triphosphate / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002784:Cholesterol / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology; D009000:Monocytes / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011973:Receptors, LDL / Q000378:metabolism; D013189:SRS-A / Q000494:pharmacology
D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D010972:Platelet Activating Factor; D011973:Receptors, LDL; D013189:SRS-A; D000255:Adenosine Triphosphate; D002784:Cholesterol; D002118:Calcium