Soluble FLT1 sensitizes endothelial cells to inflammatory cytokines by antagonizing VEGF receptor-mediated signalling.
OBJECTIVE
Pre-eclampsia affects 5-7% of pregnancies, and is a major cause of maternal and foetal death. Elevated serum levels of placentally derived splice variants of the vascular endothelial growth factor (VEGF) receptor, soluble fms-like tyrosine kinase-1 (sFLT1), are strongly implicated in the pathogenesis but, as yet, no underlying mechanism has been described. An excessive inflammatory-like response is thought to contribute to the maternal endothelial cell dysfunction that characterizes pre-eclampsia. We hypothesized that sFLT1 antagonizes autocrine VEGF-A signalling, rendering endothelial cells more sensitive to pro-inflammatory factors also released by the placenta. We tested this by manipulating VEGF receptor signalling and treating endothelial cells with low doses of tumour necrosis factor-α (TNF-α).


RESULTS
Application of recombinant sFLT1 alone did not activate human umbilical vein endothelial cells (HUVECs). However, antagonizing the autocrine actions of endothelial VEGF-A and/or placenta growth factor (PlGF) by pre-incubation with recombinant sFLT1, anti-FLT1, anti-VEGF receptor 2 (KDR), anti-VEGF-A, VEGF receptor tyrosine kinase inhibitor SU5614, or knocking-down FLT1 or KDR transcripts rendered cells more sensitive to low doses of TNF-α. Each treatment increased activation, as measured by increases in endothelial intercellular adhesion molecule 1 (ICAM1), vascular cell adhesion molecule 1 (VCAM1), endothelin 1 (ET-1), von Willebrand factor (vWF), and leucocyte adhesion, and led to reduction in AKT Ser⁴⁷³ and endothelial nitric oxide synthase (eNOS) Ser¹¹⁷⁷ phosphorylation.


CONCLUSIONS
Our data describe a mechanism by which sFLT1 sensitizes endothelial cells to pro-inflammatory factors, providing an explanation for how placental stress may precipitate the pre-eclamptic syndrome.
Centre for Trophoblast Research, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
Tereza
T
Cindrova-Davies
Deborah A
DA
Sanders
Graham J
GJ
Burton
D Stephen
DS
Charnock-Jones
D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D005260:Female; D018922:HL-60 Cells; D006801:Humans; D010920:Placenta / Q000276:immunology / Q000378:metabolism; D011225:Pre-Eclampsia / Q000276:immunology / Q000378:metabolism*; D011247:Pregnancy; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D012995:Solubility; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014471:Umbilical Veins / Q000166:cytology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D014657:Vasculitis / Q000276:immunology / Q000378:metabolism*
D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C501162:FLT1 protein, human; D040281:Vascular Endothelial Growth Factor Receptor-1; D051057:Proto-Oncogene Proteins c-akt