Inhibition by dexamethasone of c-jun n-terminal kinase in rbl-2h3 cells

The antigen stimulation of rat basophilic leukemia RBL-2H3 cells induces I42 MAP kinase (Erk) activation, and the activation is inhibited by dexamethasone (J. Immunol. 157: 2374-2380. 1996). Recently, c-Jun N4erminal kinase (JNK) was identified as a member of MAP kinase family and was reported to be activated in the antigen stimulated mast cells. In the present study, tile effect of dexamethasone on the antigen induced J N K activation in rat basophilic leukemia RBL-2H3 cells was examined. JNK activity was determined by italicize in vitro kinase assay using GSF-c-Jun (1-79) as a substrate. JNK was activated within a few minutes and its activity reached a maximum 40 min after the antigen stimulation. Pretreatment with dexamethasone (1 to 100 nM) for 18 h inhibited JNK activation in a concentration-dependenl manner. The inhibition was time-dependent, being apparent after 6 h pretreatment (60, inhibition by 100 nM dexametlasone). These results indicate that dexamethasone inhibits the antigen-induced JNK activation as well as Erk activation in mast cells.