Cytosolic phospholipase A2 is responsible for prostaglandin E2 and leukotriene B4 formation in phagocyte-like PLB-985 cells: studies of differentiated cPLA2-deficient PLB-985 cells

AbstractOur previously established model of cytosolic phospholipase A2 (cPLA2)-deficient, differentiated PLB-985 cells (PLB-D cells) was used to determine the physiological role of cPLA2 in eicosanoid production. Parent PLB-985 (PLB) cells and PLB-D cells were differentiated toward the monocyte or granulocyte lineages using 5 × 10−8 M 1,25 dihydroxyvitamin D3 or 1.25% dimethyl sulfoxide, respectively. Parent monocyte- or granulocyte-like PLB cells released prostaglandin E2 (PGE2) when stimulated by ionomycin, A23187, opsonized zymosan, phorbol 12-myristate 13-acetate, or formyl-Met-Leu-Phe (fMLP), and monocyte- or granulocyte-like PLB-D cells did not release PGE2 with any of the agonists. The kinetics of cPLA2 translocation to nuclear fractions in monocyte-like PLB cells stimulated with fMLP or ionomycin was in correlation with the kinetics of PGE2 production. Granulocyte-like PLB cells, but not granulocyte-like PLB-D cells, secreted leukotriene B4 (LTB4) after stimulation with ionomycin or A23187. Preincubation of monocyte-like parent PLB cells with 100 ng/ml lipopolysaccharide (LPS) for 16 h enhanced stimulated PGE2 production, which is in correlation with the increased levels of cPLA2 detected in these cells. LPS preincubation was less potent in increasing PGE2 and LTB4 secretion and did not affect cPLA2 expression in granulocyte-like PLB cells, which may be a result of their lower levels of surface LPS receptor expression. LPS had no effect on monocyte- or granulocyte-like PLB-D cells. The lack of eicosanoid formation in stimulated, differentiated cPLA2-deficient PLB cells indicates that cPLA2 contributes to stimulated eicosanoid formation in monocyte- and granulocyte-like PLB cells.