METHOTREXATE INHIBITS SUPEROXIDE PRODUCTION AND CHEMOTAXIS IN NEUTROPHILS ACTIVATED BY GRANULOCYTE-COLONY-STIMULATING FACTOR

Treatment of circulating human neutrophils with recombinant human gran ulocyte colony-stimulating factor (rhG-CSF) for 30 min augmented super oxide generation and chemotaxis induced by N-formylmethionyl-leucyl-ph enylalanine (fMLP) in a dose dependent manner. When neutrophils were t reated with 1 mu M of metho-trexate (MTX) for 60 min after incubation with rhC-CSF (10 ng/ml), the effects of rhC-CSF on superoxide generati on and chemotaxis were inhibited by approximately 49 and 29%, respecti vely. Although inhibitory effects of MTX were also seen in neutrophils not pretreated with rhG-CSF, the degree of inhibition was much less. The addition of either hypoxanthine or guanosine at a concentration of 100 mu M to the culture medium significantly attenuated the effects o f MTX. However, in neutrophils obtained from a patient with Lesch-Nyha n syndrome, which lacked hypoxanthine-guanine phosphoribosyl transfera se activity, neither hy poxanthine nor guanosine had any rescue effect . These results suggest that MTX inhibits superoxide generation and ch emotaxis in rhC-CSF-activated neutrophils, at least in part, by distur bing purine nucleotide biosynthesis. (C) 1996 Wiley-Liss, Inc.