Granulocyte Colony-Stimulating Factor Promotes Functional Maturation of O−2Generating System during Differentiation of HL-60 Cells to Neutrophil-like Cells

Abstract

The effects of granulocyte colony-stimulating factor (G-CSF) on development of O−2generating system during differentiation of HL-60 cells to neutrophil-like cells have been studied. G-CSF enhanced O−2generating ability of HL-60 cells whose differentiation had been initiated by dimethylsulfoxide (DMSO) or retinoic acid (RA). The O−2generations by the differentiated HL-60 cells in response to opsonized zymosan (OZ), formyl-Met-Leu-Phe (fMLP), and IgG-coated zymosan were increased two- to fourfold as a result of incubation of the cells undergoing the differentiation with G-CSF. The potentiation by G-CSF occurred in a dose-dependent manner with the maximum effect at about 10 ng/ml G-CSF. The effect of G-CSF could not be fully explained by up-regulation of the receptor expression on the HL-60 cells, because the number of C3bi receptors was not altered by G-CSF, whereas the expression of fMLP receptor was enhanced by G-CSF. On the other hand, the O−2generation of the differentiated cells activated byphorbol 12-myristate 13-acetate was not affected by the G-CSF treatment, suggesting that the biochemical events in the cells after PKC activation might not be enhanced by G-CSF. Assuming that the signaling pathways linking OZ or fMLP receptor might be enhanced by G-CSF, alteration in the cellular sn-1,2-diacylglycerols (DAG) level upon stimulation with OZ or fMLP was compared between the G-CSF-treated and nontreated cells. Whereas DAG level was not increased by the stimulation in the cells treated with DMSO alone, a significant increase in DAG level upon the stimulation was observed in the cells treated with G-CSF and DMSO. These results suggest that G-CSF would enhance the organization of a receptor-linked DAG generating system in the differentiating cells, leading the cells to generate more O−2.