Effects of protein kinase C and phospholipase C inhibitors on IgE-dependent and IgE-independent basophil histamine release

Objective and Design: This study was aimed to evaluate the effects of two p rotein kinase C (PKC) inhibitors (staurosporine and chelerythrine) and one phospholipase C (PLC) inhibitor (U73122) on basophil histamine release indu ced by anti-IgE, N-formyl-methionyl-leucyl-phenylalanine (FMLP), IL-3 and G M-CSF. Methods: Leukocytes were suspended in solutions containing physiological or low Na+ concentrations, since IL-3 and GM-CSF were shown to induce histami ne release only when the inhibitory effect of extracellular Na+ has been re moved. After incubation with PKC and PLC inhibitors, the stimuli were added and histamine release was measured by an automated fluorometric method. Results: Staurosporine and chelerythrine exerted a significant inhibitory e ffect on histamine release induced by anti-IgE, IL-3 and GM-CSF at concentr ations much higher than those required to inhibit PKC. FMLP-induced histami ne release in a physiological Na+-containing medium was not significantly m odified by staurosporine, although it was reduced by high concentrations of chelerythrine. A slight inhibition by high concentrations of staurosporine was found when basophils were suspended in a low Na+ medium. U73122 exerte d a significant and dose-dependent inhibitory effect on basophil histamine release induced by anti-IgE, FMLP, IL-3 and GM-CSF Conclusion: These results suggest that a prodegranulatory role of PKC in ba sophil histamine release induced by anti-IgE, FMLP, IL-3 and GM-CSF is unli kely; conversely, it is conceivable that PLC has a role in signal transduct ion and histamine release induced by the above stimuli.