Hereditary hemorrhagic telangiectasia (HHT) is a genetic disease characterized by
vascular dysplasia. Mutations of the endoglin (ENG) gene that encodes a co-receptor of the transforming growth factor β1 signaling pathway
cause type I HHT. ENG is primarily expressed in endothelial cells (ECs), but its interaction
with other key angiogenic pathways to control angiogenesis has not been well addressed.
The aim of this study is to investigate ENG interplay with VEGFR2, FGFR1 and TIE2
in primary human ECs. ENG was knocked-down with siRNA in human umbilical vein ECs (HUVECs) and human lung microvascular
ECs (HMVEC-L). Gene expression was measured by RT-qPCR and Western blotting. Cell
signaling pathway activation was analyzed by detecting phosphor-ERK and phosphor-AKT
levels. Cell migration and apoptosis were assessed using the Boyden chamber assay
and the CCK-8 Kit, respectively. Loss of ENG in HUVECs led to significantly reduced
expression of VEGFR2 but not TIE2 or FGFR1, which was also confirmed in HMVEC-L. HUVECs
lacking ENG had significantly lower levels of active Rac1 and a substantial reduction
of the transcription factor Sp1, an activator of VEGFR2 transcription, in nuclei.
Furthermore, VEGF- but not bFGF- or angiopoietin-1-induced phosphor-ERK and phosphor-AKT
were suppressed in ENG deficient HUVECs. Functional analysis revealed that ENG knockdown
inhibited cell migratory but enhanced anti-apoptotic activity induced by VEGF. In
contrast, bFGF, angiopoietin-1 and -2 induced HUVEC migration and anti-apoptotic activities
were not affected by ENG knockdown. In conclusion, ENG deficiency alters the VEGF/VEGFR2
pathway, which may play a role in HHT pathogenesis.
Abbreviations:
HHT (Hereditary hemorrhagic telangiectasia), ENG (Endoglin), EC (Endothelial cell), HUVEC (Human umbilical vein endothelial cell), HMVEC-L (Human lung microvascular endothelial cell), AVM (Arteriovenous malformation), ALK (Activin receptor-like kinase), SMAD (Mothers against decapentaplegic homolog), TGF-β (Transforming growth factor-beta), ANGPT (Angiopoietin), siRNA (Small interfering RNA), RT-qPCR (Reverse transcription-quantitative polymerase chain reaction), ERK (Extracellular signal-regulated kinase), VEGF-A (Vascular endothelial growth factor A), VEGFR2 (Vascular endothelial growth factor receptor 2), TIE2 and TEK (Tyrosine-protein kinase receptor), FGF2 (fibroblast growth factor 2), FGFR (Fibroblast growth factor receptor), NF-kB (Nuclear factor kappa B), Sp1 (Specific protein 1), Rac1 (Ras-related C3 botulinum toxin substrate 1), GAPDH (Glyceraldehyde 3-phosphate dehydrogenase)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: April 21, 2021
Accepted:
April 14,
2021
Received in revised form:
March 29,
2021
Received:
July 16,
2020
Identification
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