Phosphoinositide breakdown is associated with Fc-gamma RII-mediated activation of 5'-lipoxygenase in murine eosinophils.
In this report we present data on the ability of murine eosinophils to generate inositol phosphate derivatives, and their relationship with the activation of 5'-lipoxygenase by a Fc-gamma R-dependent mechanism. The addition of anti-IgG F(ab')2 to mouse eosinophils, previously sensitized with IgG, induces inositol phosphate generation after 2 min and after 10 min of stimulation. Maximal generation of inositol tris and inositol tetrakis phosphate has been detected after 15 min of stimulation, and the optimal concentration of anti-IgG F(ab')2 was found to be 25 micrograms. Inositol tris phosphate formation is also observed at 5 min after the addition of the calcium ionophore A23187 (5 microM). We also report that neomycin, an inhibitor of phosphoinositide-phospholipase C, inhibits Fc-gamma R-mediated phosphoinositide breakdown in a dose-dependent manner (88% inhibition at 150 microM of neomycin). The possible involvement of phosphoinositide breakdown in the activation of 5'-lipoxygenase has been investigated. Using streptolysin-O permeabilized cells and different doses of neomycin that inhibit phosphoinositide breakdown, we have demonstrated a parallel decrease in LTC4 released by these cells, using either A23187 (86% inhibition at 200 microM of neomycin) or anti-IgG F(ab')2 (82.4% inhibition at 100 microM of neomycin). [Ca2+]i elevation has been observed by loading the cells with the fluorescent calcium indicator Fura-2 penta-acetoxy methyl ester and after stimulating with the anti-Fc-gamma RII mAb (2.4G2). It is likely that the activation of murine eosinophils by a Fc-gamma R mechanism stimulates phosphoinositide breakdown as a primary step that leads to the activation of murine 5'-lipoxygenase, producing the formation of leukotriene C4.
De Andres
B
B
Department of Immunology, Fundación Jimenez Diaz, Madrid, Spain.
Del Pozo
V
V
Cardaba
B
B
Martin
E
E
Tramon
P
P
Lopez-Rivas
A
A
Palomino
P
P
Lahoz
C
C
D000818:Animals; D000943:Antigens, Differentiation / Q000502:physiology*; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation; D004804:Eosinophils / Q000187:drug effects / Q000201:enzymology*; D005260:Female; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism; D007295:Inositol Phosphates / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D009355:Neomycin / Q000494:pharmacology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000502:physiology; D011961:Receptors, Fc / Q000502:physiology*; D017452:Receptors, IgG; D013189:SRS-A / Q000378:metabolism
D000943:Antigens, Differentiation; D007140:Immunoglobulin Fab Fragments; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D011961:Receptors, Fc; D017452:Receptors, IgG; D013189:SRS-A; D001094:Arachidonate 5-Lipoxygenase; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D009355:Neomycin; D002118:Calcium