In vitro cytotoxicity of neutrophil-like human HL-60 cells undergoing an oxidative burst with Escherichia coli reporter strains

Abstract

Neutrophil-like human promyelocytic HL-60 cells produced substantial amounts of reactive oxygen intermediates (ROIs) after stimulation with the tumour promoter phorbol myristate acetate (TPA). Escherichia coli PQ37 and PQ300 reporter strains incurred high levels of toxicity after co-incubation with neutrophil-like HL-60 cells undergoing an oxidative burst. Toxicity was dependent on (a) the differentiation of HL-60 cells into neutrophil-like cells, (b) the stimulation of HL-60 cells with TPA and (c) the ratio of HL-60 to target cells. It is concluded that Escherichia coli PQ37 and PQ300 reporter strains can effectively be used to evaluate the cytotoxicity of neutrophils in vitro. The toxicity of HL-60 cells was, however, only marginally inhibited by the antioxidative enzymes catalase or superoxide dismutase. This indicates that, under the conditions chosen, cytotoxicity of HL-60 cells to Escherichia coli is mainly determined by factors other than ROIs and appears to be the result of complex interactions of the numerous reactive compounds that are released in addition to ROIs.