[Activation of retinoic acid (RA)-differentiated HL-60 cells by saponins]

The effect of saponins on the one of major functions of neutrophil, namely the generation of superoxide anion (O2-), was investigated using retinoic acid (RA)-differentiated HL-60 cells (promyelocytic leukemia cells). The generation of O2- from the cells induced by saponins was monitored by the reduction of cytochrome c. All five species of crude saponins studied here, i.e. tea-leaf saponins, tea-seed saponins, ginsenosides, soyasaponins and saikosaponins, stimulated the generation of O2- from RA-differentiated HL-60 cells. Tea-leaf saponins showed the highest stimulating activity, followed by soyasaponins and ginsenosides. The cytotoxic activity of saponins was determined by the dye exclusion method after the incubation of RA-differentiated HL-60 cells with various concentrations of saponins. Saikosaponins and tea-seed saponins exhibited considerable cytotoxic activity and hemolytic activity. To examine the involvement of protein kinase C (PKC) in the neutrophil activation by saponins, the effect of H-7, an antagonist of PKC, on the generation of O2- induced by saponins was investigated. H-7 was found to inhibit the generation of O2- in a dose-dependent manner, suggesting the participation of PKC in the neutrophil stimulating process by saponins. Tea-leaf saponins, ginsenosides and soyasaponins, which had high neutrophil stimulating activity and low cytotoxic activity, seemed to be useful as a biological response modifier (BRM) for the activation of neutrophil.