Differences in arachidonic acid metabolism by human myelomonocytic cell lines

The production of arachidonic acid metabolites by the HL60, ML3, and U937 human phagocyte cell lines was determined after incubation with interferon-gamma (IFN-gamma, 500 U/ml) or vehicle for 4 days. Cells were prelabeled with tritiated arachidonic acid, [3H]AA, for 4 h, and media supernatants were analyzed by high-performance liquid chromatography. None of the cell lines produced [3H]AA metabolites in large amounts during an unstimulated, basal release period (30 or 60 min). In response to 10 microM calcium ionophore A23187 incubation (30 min), undifferentiated and IFN-gamma-differentiated HL60 cells formed both cyclooxygenase products (thromboxane and prostaglandins) and lipoxygenase products (leukotrienes and hydroxyeicosatetraenoic acids). In contrast to the HL60 cells, IFN-gamma-differentiated U937 cells formed primarily cyclooxygenase products and undifferentiated and IFN-gamma-differentiated ML3 cells did not form any [3H]AA metabolites in response to A23187. These results indicate the need to be careful in selecting a cell line for use in a phagocyte assay system when cyclooxygenase and/or lipoxygenase products could influence the assay results.