Deferoxamine Enhances Phagocytic Function of Human Polymorphonuclear Leukocytes

Abstract

Inhibition of the iron-mediated generation of toxic oxygen species by polymorphonuclear leukocytes (PMN) might prevent oxidative damage and thus enhance phagocytic function of PMN. To investigate this point, we studied the effect of the specific iron chelator, deferoxamine, on the antibacterial function of PMN. PMN were incubated for 20 hr with various concentrations of deferoxamine at 37 degrees C in medium containing 0.54 microM endogenous iron. The cells were then washed, and the phagocytic cell function was assessed. The results were compared with those for control PMN preincubated for 20 hr without deferoxamine, and those of nonincubated PMN. Compared with that of control PMN, the uptake of radiolabeled Staphylococcus aureus by PMN treated with 1 microM-1 mM deferoxamine was, on average, 10%-20% higher. This effect was not observed when iron-saturated deferoxamine (DFO) was used. Bacterial uptake was similarly increased in nonpreincubated PMN or PMN preincubated for 20 hr at 4 degrees C instead of 37 degrees C. The intracellular killing capacity of both deferoxamine-treated and control PMN exceeded 90%. PMN incubated for 20 hr at 37 degrees C with DFO not only phagocytosed more bacteria than control cells, but were also capable of killing the greater number of bacteria ingested. This increased activity of deferoxamine-treated PMN was accompanied by enhanced generation of chemiluminescence and production of superoxide during phagocytosis of S. aureus. These findings indicate that deferoxamine may enhance the antibacterial activity of PMN by protecting the cells against damage by iron-mediated generation of toxic oxygen metabolites in resting PMN.