Abstract
This study was undertaken to examine whether the production of active oxygen species by bleomycin (BLM) could be enhanced by various cytokines in human neutrophils.Peripheral blood neutrophils were obtained from normal volunteers, and the production of superoxide radical (O-2) and the generation of luminol dependent chemiluminescence (LDCL) were measured by the cytochrome C reduction method and an ATP photometer, respectively. IL-1α, IL-1β, IL-2, IL-6, IL-8, G-CSF, IFN-γ, and TNF-α were used as cytokincs, and neutrophils were treated with these cytokines for 10 minutes at 37°C. Phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (FMLP) were used as stimulants of O-2 and LDCL production, respectively.
The results of these experiments revealed slight production of O-2 from neutrophils by BLM, and the production of O-2 by PMA was enhanced by BLM concentrations over 0.3 μg/ml. With a concentration of 2, 500 U/ml of IFN-γ, and at concentrations over l ng/ml of TNF-α, small amounts of O-2 wcre produced without the stimulants or BLM. Thc production of O-2 by BLM was enhanced by IL-1α, IL-1β, IL-8, G-CSF, IFN-γ and TNF-α, that produced by PMA was enhanced by IFN-γ or TNF-α, and O-2 produccd by BLM and PMA in combination was enhanced by IL-8, G-CSF, IFN-γ and TNF-α.
These results suggest that the production of active oxygen species by BLM in vivo may be enhanced by these cytokines, except for IL-2 and IL-6. Through this mechanism, cytokines might enhance the antitumor activity of BLM.
