Transcriptome of Angiopoietin 1–Activated Human Umbilical Vein Endothelial Cells

Abstract

Angiopoietin 1 (Ang-1) is the main ligand for endothelial cell-specific tyrosine kinase (Tie-2) receptors and it promotes migration and proliferation and inhibits apoptosis and vascular leakage. The exact mechanisms through which the Ang-1 exerts these effects remain unclear. The authors exposed human umbilical vein endothelial cells (HUVECs) to Ang-1 (300 ng/mL) for 4 h and conducted gene expression profiling using oligonucleotide microarrays. Real-time polymerase chain reaction (PCR) was also conducted to verify several of the genes that were regulated by Ang-1. Exposure to Ang-1 resulted in induction of 86 genes that are involved in endothelial cell (EC) proliferation, differentiation, migration, and survival. Thirty-six of these genes, including stanniocalcin, cyclin D1, vascular endothelial growth factor C, fms-related tyrosine kinase 1, interleukin 8, and CXCR4 have previously been shown to be induced by vascular endothelial growth factor (VEGF), suggesting significant similarities between VEGF and Ang-1 pathways. Ang-1 exposure also inhibited mRNA expressions of 49 genes, most of which are involved in cell cycle arrest, apoptosis, and suppression of transcription. These results indicate that Ang-1 triggers coordinated responses in endothelial cells designed to inhibit the expression of proapoptotic and antiproliferative genes and up-regulate proproliferative, proangiogenic, and antiapoptotic pathways. Moreover, we also found that the Erk1/2, phosphatidylinositol (PI) 3-kinase, and the mTOR pathways are involved in Ang-1-induced gene expression in HUVECs.

Early Growth Response-1 Regulates Angiopoietin-1-Induced Endothelial Cell Proliferation, Migration, and Differentiation

“…We have recently reported that mTOR and its downstream effector, p70S6 kinase, are activated downstream from Tie-2 receptors in HUVECs and that mTOR participates in Ang-1-induced alterations in the HUVEC transcriptome. 4 Very little is known about interactions between Egr-1 and the mTOR network, although it has been demonstrated that induction of Egr-1 expression is mediated, in part, through the mTOR/P70S6 kinase pathway during skeletal myoblast differentiation. 18 We also confirm here that the p38 MAPK pathway inhibits Egr-1 transcription and that this effect is mediated through a negative influence on Erk1/2 pathway activation.…”

“…These genes are known targets of the Ang-1/Tie-2 receptor pathway and Egr-1-mediated transcription. 4,5 Genes were detected 24 hours after transfection of HUVECs with siRNA oligonucleotides or DNAzymes. Results were analyzed using the comparative threshold cycle (C T ), as previously described.…”

“…4 Egr-1 is an immediateearly gene that is rapidly and transiently induced by many stimuli, including hypoxia, shear stress, and injury. On activation it binds promoter regions of several growth factors, cytokines, receptors, and adhesion molecules.…”

Angiopoietin-1 promotes endothelial cell proliferation and migration through AP-1–dependent autocrine production of interleukin-8

“…7 Exposure to Ang-1 resulted in induction of 86 genes that are involved in EC proliferation, differentiation, migration, and survival. In addition, Ang-1 elicited a significant decline in the expression of 49 genes, most of which are involved in cell-cycle arrest, apoptosis, and suppression of transcription.…”

Differential Cytokine Responses in Human and Mouse Lymphatic Endothelial Cells to Cytokinesin Vitro

“…38 VEGF-C released by platelets, monocytes, macrophages, and BEC, 39 also regulates BEC proliferation, vascular permeability, 40 capillary formation, 41 inflammatory-activation, 42 and leukocyte binding to BEC. 37 VEGF-C and VEGF-D also play dominant roles in BEC and LEC survival, proliferation, migration, capillary formation in vivo and in vitro; 43 their effects in inflammation are less well characterized.…”