Transcriptional and post‐transcriptional regulation of monocyte chemoattractant protein‐3 gene expression in human endothelial cells by phorbol ester andcAMP signalling

Monocyte chemoattractant protein-3 (MCP-3) is one of the most broadly active chemokines, potentially inducing chemotaxis of all leucocytic cells. In the present study, we examined the regulation of MCP-3 mRNA and protein production in endothelial cells by protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA) and cAMP signalling. On stimulation of endothelial cells with 10 nM PMA, MCP-3 mRNA increased to 300-fold the basal level at 3 hr and rapidly declined to 0.2-fold the basal level at 24 hr. PMA-induced MCP-3 mRNA and protein production of human endothelial cells were partially inhibited by pretreatment with the adenylate cyclase activator, forskolin, or membrane-permeable cAMP derivative. The PMA-induced MCP-3 mRNA increase was almost abrogated when cells were pretreated with cycloheximide (CHX). Forskolin inhibited the transcription of PMA-induced MCP-3 gene expression. Following PMA stimulation for 3 hr, subsequent addition of actinomycin D suppressed the rapid decay of PMA-induced MCP-3 mRNA. These results suggest that PMA induces the transcriptional activation of the MCP-3 gene through de novo protein synthesis and the rapid decay of PMA-induced MCP-3 mRNA through de novo synthesis of adenosine/uridine (AU)-rich element binding proteins and cAMP signalling inhibits the PMA-induced transcriptional activation of the MCP-3 gene expression.