Oxygen metabolism of the HL-60 cell line: comparison of the effects of monocytoid and neutrophilic differentiation.

HL-60 cells are promyelocytic leukemia cells that respond to culture conditions with differentiation into granulocytelike or macrophagelike phagocytes. O2 metabolism is critical to the microbicidal function of phagocytic cells. O2 metabolism was studied in HL-60 cells differentiated with dimethylsulfoxide (Me2SO) and 1,25(OH)2D3, with the objective of 1) determining the validity of these cells as models for human neutrophils and monocytes, respectively, and 2) determining whether these cells are capable of forming hydroxyl radical. Me2SO-treated cells had morphology consistent with human neutrophils. O2 consumption by these cells in response to phorbol myristate acetate (PMA; 100 ng/ml) or opsonized zymosan (3 mg/ml) was less than that by neutrophils, as was superoxide formation. O2 metabolism was not inhibited by KCN or antimycin A. Myeloperoxidase (MPO) activity decreased during differentiation but remained greater than that of human neutrophils. Cytochalasin B enhanced recovery of superoxide secreted in response to zymosan, implying its release from the phagosome. 1,25(OH)2D3-treated cells had morphology consistent with monocytes. O2 consumption and superoxide release were less than with Me2SO-treated cells. Unlike the case with human monocytes, O2 consumption was not inhibited by KCN or antimycin A. MPO activity was minimally reduced by differentiation. Cytochalasin B inhibited recovery of superoxide. Luminol-dependent luminescence was greater among 1,25(OH)2D3-treated cells than among Me2SO-treated cells. Free radicals were also measured with a spin trapping technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Spin trapping allows direct, simultaneous detection of superoxide and hydroxyl radicals. Regardless of the mechanism of differentiation, only superoxide was formed by HL-60 cells. These results show that Me2SO-treated HL-60 cells represent an excellent model for the study of human neutrophil oxidative function. However, 1,25(OH)2D3-treated cells are quite different in their O2 metabolism from peripheral blood monocytes.