INHIBITION OF SUPEROXIDE PRODUCTION AND CHEMOTAXIS BY METHOTREXATE INNEUTROPHILS PRIMED BY TNF-ALPHA OR LPS

We have demonstrated recently that methotrexate (MTX) inhibits superox ide generation and chemotaxis induced by N-formylmethionyl-leucyl-phen ylalanine (fMLP) in neutrophils primed by granulocyte colony-stimulati ng factor (G-CSF). To extend these observations, we examined the in vi tro effect of MTX on fMLP-stimulated superoxide generation and chemota xis in neutrophils primed by either tumor necrosis factor alpha (TNF-a lpha) or bacterial lipopolysaccharide (LPS). MTX inhibited superoxide generation and chemotaxis more efficiently in TNF-alpha- or LPS-primed neutrophils than in unprimed neutrophils. When either hypoxanthine or guanosine was added to the culture medium, the effects of MTX were pa rtially counteracted. Furthermore, MTX caused a significant inhibition of both superoxide production induced by phorbol 12-myristate-13-acet ate and chemotaxis induced by interleukin 8 in G-CSF-primed neutrophil s. These results may support the hypothesis that neutrophils primed by different stimuli are more susceptible to the inhibitory effects of M TX on superoxide generation and chemotaxis irrespective of chemoattrac tants. Such an effect can be partly attributed to the perturbation of purine nucleotide biosynthesis.