BW755C inhibits the 5-lipoxygenase in E-mast cells without affecting degranulation.

The inhibitory effect of the drug BW755C on the 5-lipoxygenase pathway was analyzed for bone marrow-derived murine mast cells, termed E-mast cells. The drug prevented the formation of 5-HETE from exogenous [14C]arachidonic acid when IgE-sensitized cells were challenged by the antigen. BW755C also prevented formation of leukotriene C4 in a dose-dependent fashion when IgE-sensitized mast cells, preincubated with the drug, were activated with either the specific antigen or the ionophore. Leukotriene C4 inhibition occurred with a minimal drug preincubation period of 1 min before the cells were subjected to antigen-dependent activation. BW755C did not affect the degranulation response of these cells. Thus in an intact cell system BW755C prevents 5-lipoxygenation of arachidonic acid. Furthermore, this study reveals that even with transmembrane activation of E-mast cells through their IgE-Fc receptors, granule secretion is not dependent upon corresponding metabolites from the 5-lipoxygenase pathway.