XXXX up-regulates phosphodiesterase IV activity in U-937 cells through H2 receptor stimulation and @entity268 increase.

@entity1 @entity483 @entity268 @entity3933 @entity1980 @entity7428 @entity1880 @entity377 @entity112 @entity5616
BACKGROUND: An increase of @entity1980 ( @entity1980 ) has been described in blood mononuclear white cells of @entity1 with @entity483 ( @entity483 ). This study was intended to search for the putative relationship between @entity112 and @entity1980 in inflammatory cells. MATERIAL/METHODS: The @entity1 monocyte cell line U-937 was used as a model of blood mononuclear leucocytes. @entity1980 activity was determined as the increase of @entity268 degradation, which is specifically inhibited by @entity7428 . Intracellular @entity268 content was measured and correlated to @entity1980 activity. RESULTS: 1 microM @entity112 produced a 2- to 3-fold selective increase in @entity1980 activity in U-937 cells after 4 hours of incubation. Enzyme activation was reversible, concentration- and time dependent. @entity1880 (10 microM) prevented @entity112 -induced stimulation of @entity1980 . The H2-receptor antagonist, @entity5616 , but not the H1-receptor antagonist, @entity3933 , prevented @entity112 -induced activation of @entity1980 in a concentration-dependent manner. Inhibition of @entity268 degradation in the presence of @entity112 plus rolipram after 4 h of incubation further increased @entity268 levels and @entity1980 activity. CONCLUSIONS: These results suggest that @entity112 -induced stimulation of @entity1980 is mediated by the H2 receptor and related to intracellular levels of @entity268 . AMPc enhancement of the cyclic @entity377 levels may trigger expression and synthesis of this enzyme.
