Induction of NOS in rat blood PMN in vivo and in vitro: modulation by tyrosine kinase and involvement in bactericidal activity

Intravenous administration of lipopolysaccharide (LPS) to rats increased th e production of nitric oxide (NO) metabolites (NOx) by blood polymorphonucl ear neutrophils (PMN) in vitro, Both dexamethasone and L-NMMA, added in vit ro to neutrophil cultures, inhibited the production of NO, On the other han d, the production of NO was not affected by the treatment, ill vivo or in v itro, with different inhibitors of cyclooxygenase or 5-lipoxygenase or with a platelet-activating factor (PAF) antagonist. The incubation of blood FMN from normal rats in vitro with neutrophil activators (PAF, leukotriene B-4 , and interleukin-8) and different cytokines [interleukin-1, tumor necrosis factor alpha, and interferon-gamma (IFN-gamma)] showed that only IFN-gamma was able to induce the production of high amounts of NO, This induction wa s directly correlated with the expression of iNOS and an increase in in the enzyme activity in blood PMN, The tyrosine kinase inhibitor genistein inhi bited NO production induced by IFN-gamma, suggesting that the signal transd uction pathway leading to NOS induction in rat PMN involves phosphorylation by tyrosine kinase. We also showed that NO produced by IFN-gamma activated rat blood PMN involved hi the killing of Pseudomonas aeruginosa.