Multiple signaling pathways regulate NF-kappa B-dependent transcription ofthe monocyte chemoattractant protein-1 gene in primary endothelial cells

The cytokine-induced C-C chemokine monocyte chemoattractant protein-1 (MCP- 1) is an important regulator of leukocyte recruitment to sites of inflammat ory challenge. Here, it is demonstrated that the widely distributed contact hapten NiCl2, like tumor necrosis factor a (TNF alpha), induces monocyte-c hemoattractant activity in primary human endothelial cells via induction of MCP-1, NiCl2 rapidly activated mitogen-activated protein (MAP) kinase p38, and inhibition of p38 partially blocked NiCl2-induced MCP-1 messenger RNA and protein expression. Both NiCl2- and TNF alpha -induced MCP-1 synthesis was sensitive to D609, an inhibitor of phosphatidylcholine-dependent phosph olipase C (PC-PLCl. NiCl2-induced MCP-1 synthesis required activation of NF -kappaB since mutation of NF-kappaB-binding sites in the promoter resulted in complete loss of inducible promoter activity. Consistent with that findi ng, stimulation with NiCl2 or TNF alpha activated I kappaB kinase-p (IKK be ta), and transient transfection of dominant-negative IKK beta strongly inhi bited NiCl2- and TNF alpha -induced MCP-I expression. However, D609 and the specific p38 inhibitor SB202190 did not affect NiCl2- and TNF alpha -induc ed IKK beta activation, NF-kappaB DNA-binding activity, or transcriptional activity of a Gal4p65 fusion protein. This indicates that p38- and PC-PLC-d ependent pathways directly regulate the transcriptional activity of NF-kapp aB factors in the transcriptional complex, Consistent with that, inhibition of p38 blocked enhanced transcriptional activity induced by the transcript ional coactivator p300. Thus, it was concluded that at least 3 independent pathways regulate MCP-1 expression in endothelial cells, Its Induction requ ires activation of the IKK beta /1 kappaB alpha /NF-kappaB signaling pathwa y, resulting In nuclear accumulation of p65 and subsequent recruitment of c ofactors. Proper assembly and activity of this transcriptional complex is f urther modulated by the p38 MAP kinase cascade and a PC-PLC-dependent pathw ay. (C) 2001 by the American Society of Hematology.