Soluble FLT1 sensitizes endothelial cells to inflammatory cytokines by antagonizing VEGF receptor-mediated signalling

Cardiovasc Res. 2011 Feb 15;89(3):671-9. doi: 10.1093/cvr/cvq346. Epub 2010 Dec 7.

Abstract

Aims: 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).

Methods and 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Adhesion / drug effects
  • Cell Adhesion / immunology
  • Cells, Cultured
  • Endothelial Cells / cytology
  • Endothelial Cells / immunology
  • Endothelial Cells / metabolism*
  • Female
  • HL-60 Cells
  • Humans
  • Placenta / immunology
  • Placenta / metabolism
  • Pre-Eclampsia / immunology
  • Pre-Eclampsia / metabolism*
  • Pregnancy
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Small Interfering
  • Signal Transduction / drug effects
  • Signal Transduction / immunology*
  • Solubility
  • Tumor Necrosis Factor-alpha / pharmacology
  • Umbilical Veins / cytology
  • Vascular Endothelial Growth Factor A / metabolism
  • Vascular Endothelial Growth Factor Receptor-1 / genetics
  • Vascular Endothelial Growth Factor Receptor-1 / metabolism*
  • Vascular Endothelial Growth Factor Receptor-1 / pharmacology
  • Vasculitis / immunology
  • Vasculitis / metabolism*

Substances

  • RNA, Small Interfering
  • Tumor Necrosis Factor-alpha
  • VEGFA protein, human
  • Vascular Endothelial Growth Factor A
  • FLT1 protein, human
  • Vascular Endothelial Growth Factor Receptor-1
  • Proto-Oncogene Proteins c-akt