Differential regulation of protein tyrosine kinase on free radical production, granule enzyme release, and cytokine synthesis by activated murine peritoneal macrophages

Abstract

The present study examined the regulatory effect of tyrosine kinase inhibitors (genistein, tyrphostin, and 2,5-dihydroxycinnamate) on the free radical production, granule enzyme release, and synthesis of interleukin (IL)-8 and granulocyte macrophage-colony stimulating factor (GM-CSF) in murine peritoneal macrophages exposed to different stimulators [10 ng/mL of IL-1, 1 μg/mL of lipopolysaccharide (LPS), and 1 μM N-formyl-methionyl-leucyl-phenylalanine (fMLP)]. Protein tyrosine kinase (PTK) inhibitors attenuated the stimulated superoxide, hydrogen peroxide, and nitric oxide production in macrophages stimulated with IL-1, LPS, or fMLP. N,N-Dimethylsphingosine (DMS) alone stimulated superoxide and hydrogen peroxide production by intact macrophages, but at 45 μM the stimulatory effect on superoxide production was not found. In contrast, DMS attenuated nitric oxide production by macrophages. High concentrations of DMS, tyrphostin, and 2,5-dihydroxycinnamate showed cytotoxic effects. PTK inhibitors did not exhibit a significant effect on granule enzyme release induced by IL-1, whereas they attenuated the effect of LPS and fMLP on degranulation. Genistein and tyrphostin decreased the production of IL-8 and GM-CSF in macrophages activated by IL-1, whereas 2,5-dihydroxycinnamate did not affect it. The results suggest that tyrosine kinases exposed to IL-1, LPS, and fMLP may exert different modulatory actions on macrophage responses. The IL-1-activated macrophage responses, particularly degranulation, appear to be differently regulated by tyrosine kinases compared with the responses activated by LPS and fMLP.