INHIBITION OF TUMOR-NECROSIS-FACTOR SIGNAL-TRANSDUCTION IN ENDOTHELIAL-CELLS BY DIMETHYLAMINOPURINE

Tumor necrosis factor (TNF) promotes diverse responses in endothelial cells that are important to the host response to infections and malign ancies; however, less is known of the postreceptor events important to TNF action in endothelial cells than in many other cell types. Since phosphorylation cascades are implicated in cytokine signaling, the eff ects of the protein kinase inhibitor dimethylaminopurine (DMAP) on TNF action in bovine aortic endothelial cells (BAEC) were investigated. I n BAEC, TNF promotes phosphorylation of eukaryotic initiation factor 4 E (eIF-4E), c-Jun N-terminal kinase (JNK) and ceramide-activated prote in kinase activities, Jun-b expression, prostacyclin production, and, when protein synthesis is inhibited, cytotoxicity. DMAP abrogated or s ignificantly attenuated each of these responses to TNF, without affect ing the specific binding of TNF to its receptors. Histamine, another a gent active in the endothelium, promotes phosphorylation of elongation factor-2 (EF-2) and prostacyclin production, but not phosphorylation of eIF-4E in BAEC. Histamine-stimulated EF-2 phosphorylation was not i nhibited and prostacyclin production was unaffected by DMAP. These obs ervations demonstrate that a distinct signal transduction cascade, whi ch can be selectively inhibited by DMAP, promotes the response of BAEC to TNF. Thus, we have identified a reagent, DMAP, that may be useful for characterizing the TNF signal transduction pathway.