Involvement of cytosolic phospholipase A(2) and secretory phospholipase A(2) in arachidonic acid release from human neutrophils

The purpose of this study was to define the role of secretory phospholipase A(2) (sPLA(2)), calcium-independent PLA(2), and cytosolic PLA(2) (cPLA(2)) in arachidonic acid (AA) release from fMLP-stimulated human neutrophils, W hile fMLP induced the release of extracellular sPLA(2) activity and AA, 70% of sPLA(2) activity remained associated with the cell. Treatment with the cell-impermeable sPLA(2) inhibitors DTT or LY311-727, or the anti-sPLA(2) A b 3F10 all inactivated extracellular sPLA(2) activity, but had minimal effe ct on neutrophil AA mass release. In contrast, coincubation of streptolysin -O toxin-permeabilized neutrophils with DTT, LY311-727, or 3F10 all decreas ed [H-3(8)]AA release from [H-3(8)]AA-labeled, fMLP-stimulated cells. Expos ure to fMLP resulted in a decrease in the electrophoretic mobility of cPLA( 2), a finding consistent with cPLA(2) phosphorylation,and stimulated the tr anslocation of cPLA(2) from cytosolic to microsomal and nuclear compartment s. The role of cPLA(2) was further evaluated with the cPLA(2) inhibitor met hyl arachidonyl fluorophosphonate, which attenuated cPLA(2) activity in vit ro and decreased fMLP-stimulated AA mass release by intact neutrophils, but had no effect on neutrophil sPLA(2) activity. Inhibition of calcium-indepe ndent PLA(2) with haloenol lactone suicide substrate had no effect on neutr ophil cPLA(2) activity or AA mass release. These results indicate a role fo r cPLA(2) and an intracellular or cell-associated sPLA(2) in the release of AA from fMLP-stimulated human neutrophils, The Journal of Immunology, 2000 , 164: 2084-2091.