Differential effects of tyrosine kinase inhibitors on tumor necrosis factor and nitric oxide production by murine macrophages

The temporal requirements for tyrosine phosphorylation in the induction of tumor necrosis factor (TNF) and inducible nitric oxide synthase (iNOS) were compared in the murine macrophage cell line RAW 264.7. Preincubation of RAW 264.7 cells with herbimycin A or genistein (but not with either of three tyrphostins tested) significantly blocked TNF and iNOS production on exposure of these cells to combinations of lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma), The addition of either genistein or herbimycin A to RAW 264.7 cell cultures 1-6 h after stimulation with LPS and IFN-gamma had little or no effect on TNF production but markedly inhibited iNOS protein accumulation, Together these data indicate that tyrosine kinase inhibitors block iNOS production at a point well downstream of the initial wave of LPS- and IFN-gamma-mediated protein tyrosine phosphorylation.