Leukotoxicity of pyoverdin, production of reactive oxygen species, and effect of UV radiation

Pyoverdin was purified by solvent extraction, gel filtration, and ionic exc hange chromatography, Assays of cytotoxic of pyoverdin were done with human leukocytes and macrophages from the peritoneum of mice. Both cell quantiti es showed a significant reduction. Death was followed by lysis in a dose-de pendent form. The mechanism of action of pyoverdin involved the stimulation of reactive oxygen species (ROS) measured by Nitroblue Tetrazolium (NBT) r eaction and chemiluminescence (CL), UV radiation at 368 nm increased the le ukotoxicity; expositions of 5 min were enough to photostimulate the effect of pyoverdin on cellular oxydative metabolism, which increased between 35.4 and 53.2%. Genestein, an inhibitor of tyrosine kinases, counteracted the R OS stimuli of pyoverdin, suggesting endocytic mechanism of action for this pigment. The little chloroquine interference on oxydative stress indicated that intraphagosomal pH and the stimuli of reactive nitrogen intermediaries (RNI) seem to be of less importance than ROS in pyoverdin action on leukoc ytes. (C) 2001 Academic Press.