Up-regulation of vascular endothelial growth factor receptor Flt-1 after endothelial denudation: role of transcription factor Egr-1

Vascular endothelial growth factor (VEGF) is highly expressed in vascular r emodeling processes and accelerates reendothelialization after mechanical d enudation, Two VEGF tyrosine kinase receptors have been reported-fms-like-t yrosine kinase-1 (Flt-1) and kinase domain region (KDR), Little is known ab out the regulation of the expression of these receptors after vascular inju ry. Herein, we have analyzed the expression of Flt-1 after mechanical denud ation of primary cultures of endothelial cells, which has been considered a useful in vitro model to study endothelium responses to vascular injury. A fter denudation, the Flt-1 protein and mRNA levels are clearly up-regulated , and transient transfection experiments showed a strong induction of the f lt-1 promoter-dependent transcription. Analysis of the flt-1 promoter seque nce revealed the presence of a putative binding site for the early growth r esponse factor-1 (Egr-1) at positions -24 to -16, Electrophoretic mobility shift and supershift assays showed that Egr-1 was able to bind to this DNA sequence, and cotransfection of the flt-1 promoter reporter plasmid with an Egr-1 expression vector resulted in enhancement of its transcriptional act ivity. Furthermore, the mutation of the Egr-1 binding site markedly reduced the denudation-induced flt-1 promoter activity, These data demonstrate tha t Flt-1 is up-regulated after endothelial denudation and that Egr-1 plays a relevant role in this process. (Blood, 2000;95:3387-3395) (C) 2000 by The American Society of Hematology.