Vascular endothelial growth factor-A inhibits EphB4 and stimulates delta-like ligand 4 expression in adult endothelial cells

Abstract

Background During vein graft adaptation to the arterial circulation, vascular endothelial growth factor (VEGF)-A expression transiently increases before becoming down-regulated; however the role of VEGF-A in venous remodeling is not clear. In addition, although VEGF-A stimulates angiogenesis and determines arterial identity in nascent arterial endothelial cells (EC), the role of VEGF-A in regulating identity in adult venous EC is also not clear. Materials and Methods EC, wild type (EphB4+/+) or heterozygous knockout (EphB4+/−), were stimulated with VEGF-A (0–100ng/ml) and examined with qPCR and Western blotting. Results VEGF-A (100ng/ml) inhibited expression of EphB4 and stimulated expression of dll4 but did not stimulate either notch or EphrinB2 expression in adult venous EC. Pretreatment with VEGFR2 neutralizing antibody abolished VEGF-stimulated down-regulation of EphB4 but not the up-regulation of Dll4. Pretreatment with PD98059 or wortmannin showed that VEGF-A down-regulation of EphB4 and up-regulation of dll4 are MEK-ERK-dependent but PI3k-Akt-independent. Compared to VEGF-induced EphB4 down-regulation and Dll4 up-regulation in control EC, reduced EphB4 signaling in EphB4+/− EC showed even further down-regulation of EphB4 and up-regulation of dll4. Conclusions Despite the genetic programming of arterial and venous EC fate, VEGF-A can repress venous identity in adult venous EC without induction of arterial identity. These changes in adult EC in vitro recapitulate the changes in identity described during vein graft adaptation to the arterial environment in vivo.

Pathophysiologic Role of Molecules Determining Arteriovenous Differentiation in Adult Life

“…Thus, the early phase increase in VEGF-A inhibits the expression of Eph-B4 and upregulates the expression of Dll4 (a Notch ligand), but without stimulating its downstream signaling events such as Notch activation or ephrin-B2 expression in these adult ECs. These results are consistent with the effects of blocking the VEGF/COUP-TFII-Notch signaling-Eph-B4/ephrin-B2 pathway in adult ECs [55]. Therefore, vein grafts lose their venous identity markers without acquiring arterial identity.…”

Eph-B4 Mediates Vein Graft Adaptation By Regulation of eNOS

“…We previously showed that MLEC express both Eph-B4 and Ephrin-B2, consistent with a venous phenotype. 16 As expected, stimulation of endothelial cells with Ephrin-B2/Fc stimulated Eph-B4 phosphorylation, in a bimodal temporal distribution, with an early peak at approximately 1 minute and a later peak at approximately 30-60 minutes ( Figure 1A). In addition to Ephrin-B2/Fc stimulating Eph-B4 phosphorylation, Ephrin-B2/Fc also stimulated eNOS phosphorylation, in a similar bimodal pattern ( Figure 1B), that was inhibited in cells pretreated with the Eph-B4 inhibitor NVP-BHG712 ( Figure 1C).…”

Coculture of Stem Cells from Apical Papilla and Human Umbilical Vein Endothelial Cell Under Hypoxia Increases the Formation of Three-Dimensional Vessel-Like Structuresin Vitro

“…44 Another study showed that VEGF upregulates Delta-like 4 (DLL4) and presenilin expression, and increases activation of Notch4, leading to upregulation of ephrinB2 and downregulation of EphB4 in venous ECs. 45 In contrast, Yang et al 46 found that VEGF-A inhibits expression of EphB4 and stimulates expression of DLL4, but does not stimulate either Notch or ephrinB2 expression in adult venous ECs. Pretreatment with a VEGFR-2 neutralizing antibody abolishes VEGF-stimulated downregulation of EphB4, but not the upregulation of DLL4.…”