RELEASE OF PLATELET-ACTIVATING FACTOR FROM HL-60 HUMAN-LEUKEMIC CELLS FOLLOWING MACROPHAGE-LIKE DIFFERENTIATION

  • 1 January 1982
    • journal article
    • research article
    • Vol. 59  (1) , 16-22
Abstract
Platelet-activating factor (PAF), a phospholipid mediator of anaphylaxis, is released in vitro from phagocytic polymorphonuclear neutrophils (PMN) and monocytes in response to a variety of stimuli. The fact that human myeloid cells of the HL-60 line can be made to differentiate in vitro into macrophage-like cells by 12-O-tetradodecanoylphorbol-13-acetate (TPA) prompted this investigation of the generation and release of PAF during this transformation. Passive release of PAF at pH 9.5, and active release, following phagocytosis of C3b- and C3d-opsonized yeast spores, and stimulation with C5a anaphylatoxin from untreated and TPA-treated HL-60 cells, PMN, and plastic-adherent normal human monocytes were studied. After 3 days of TPA treatment, HL-60 cells released PAF following phagocytosis of C3b- and C3d-opsonized yeast spores. Inhibition of PAF release by a selective inhibitor of phospholipase A2 and labeling of PAF with sodium 14C-acetate indicated that PAF generation is a 2-step process: release of PAF precursor from cell membranes and its acetylation. A model for the in vitro study of mechanisms and metabolic events involved in PAF generation and release could perhaps be built on these findings.