Expression of vascular permeability factor/vascular endothelial growth factor in pig cerebral microvascular endothelial cells and its upregulation by adenosine.
Porcine brain-derived microvascular endothelial cells (BMEC) express the mRNA of the polypeptide mitogen vascular permeability factor/vascular endothelial growth factor (VPF/VEGF). The VEGF mRNA expression in BMEC could be upregulated 2.5 fold after 6 h of treatment with 5 microM adenosine and adenosine agonists. Adenosine A1 and A2 receptor antagonists completely abolished the upregulation of the VEGF mRNA caused by adenosine. Agents like forskolin and cAMP phosphodiesterase inhibitors which are known to increase the cAMP level decreased the VEGF mRNA expression slightly whereas agents like phorbolester which activate the proteinkinase C (PKC) pathway enhanced the VEGF mRNA expression 3.2 fold. The specific inhibitor of the PKC bisindolymaleimide (BIM) abolished the upregulation of the VEGF mRNA by adenosine completely. The BMEC conditioned medium stimulated the proliferation of BMEC itself and Western blot analysis of the BMEC conditioned medium using a polyclonal antibody to human VEGF showed one band at 18 kDa which was slightly upregulated after treatment with adenosine. Results suggest that the effect of adenosine on the VEGF mRNA expression is mediated via the A1 receptor and that an activation of the PKC may be involved in the observed effects of adenosine on the VEGF mRNA expression. VEGF produced by BMEC and which is inducible by adenosine may function via the autocrine pathway and may be involved in repair reactions of brain blood vessels and/or the maintenance of these cells.