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

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          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 Ser 473 and endothelial nitric oxide synthase (eNOS) Ser 1177 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.

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          Most cited references28

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          Circulating angiogenic factors and the risk of preeclampsia.

          The cause of preeclampsia remains unclear. Limited data suggest that excess circulating soluble fms-like tyrosine kinase 1 (sFlt-1), which binds placental growth factor (PlGF) and vascular endothelial growth factor (VEGF), may have a pathogenic role. We performed a nested case-control study within the Calcium for Preeclampsia Prevention trial, which involved healthy nulliparous women. Each woman with preeclampsia was matched to one normotensive control. A total of 120 pairs of women were randomly chosen. Serum concentrations of angiogenic factors (total sFlt-1, free PlGF, and free VEGF) were measured throughout pregnancy; there were a total of 655 serum specimens. The data were analyzed cross-sectionally within intervals of gestational age and according to the time before the onset of preeclampsia. During the last two months of pregnancy in the normotensive controls, the level of sFlt-1 increased and the level of PlGF decreased. These changes occurred earlier and were more pronounced in the women in whom preeclampsia later developed. The sFlt-1 level increased beginning approximately five weeks before the onset of preeclampsia. At the onset of clinical disease, the mean serum level in the women with preeclampsia was 4382 pg per milliliter, as compared with 1643 pg per milliliter in controls with fetuses of similar gestational age (P<0.001). The PlGF levels were significantly lower in the women who later had preeclampsia than in the controls beginning at 13 to 16 weeks of gestation (mean, 90 pg per milliliter vs. 142 pg per milliliter, P=0.01), with the greatest difference occurring during the weeks before the onset of preeclampsia, coincident with the increase in the sFlt-1 level. Alterations in the levels of sFlt-1 and free PlGF were greater in women with an earlier onset of preeclampsia and in women in whom preeclampsia was associated with a small-for-gestational-age infant. Increased levels of sFlt-1 and reduced levels of PlGF predict the subsequent development of preeclampsia. Copyright 2004 Massachusetts Medical Society
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            Accelerated metastasis after short-term treatment with a potent inhibitor of tumor angiogenesis.

            Herein we report that the VEGFR/PDGFR kinase inhibitor sunitinib/SU11248 can accelerate metastatic tumor growth and decrease overall survival in mice receiving short-term therapy in various metastasis assays, including after intravenous injection of tumor cells or after removal of primary orthotopically grown tumors. Acceleration of metastasis was also observed in mice receiving sunitinib prior to intravenous implantation of tumor cells, suggesting possible "metastatic conditioning" in multiple organs. Similar findings with additional VEGF receptor tyrosine kinase inhibitors implicate a class-specific effect for such agents. Importantly, these observations of metastatic acceleration were in contrast to the demonstrable antitumor benefits obtained when the same human breast cancer cells, as well as mouse or human melanoma cells, were grown orthotopically as primary tumors and subjected to identical sunitinib treatments.
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              Soluble endoglin and other circulating antiangiogenic factors in preeclampsia.

              Alterations in circulating soluble fms-like tyrosine kinase 1 (sFlt1), an antiangiogenic protein, and placental growth factor (PlGF), a proangiogenic protein, appear to be involved in the pathogenesis of preeclampsia. Since soluble endoglin, another antiangiogenic protein, acts together with sFlt1 to induce a severe preeclampsia-like syndrome in pregnant rats, we examined whether it is associated with preeclampsia in women. We performed a nested case-control study of healthy nulliparous women within the Calcium for Preeclampsia Prevention trial. The study included all 72 women who had preterm preeclampsia ( or =37 weeks), 120 women with gestational hypertension, 120 normotensive women who delivered infants who were small for gestational age, and 120 normotensive controls who delivered infants who were not small for gestational age. Circulating soluble endoglin levels increased markedly beginning 2 to 3 months before the onset of preeclampsia. After the onset of clinical disease, the mean serum level in women with preterm preeclampsia was 46.4 ng per milliliter, as compared with 9.8 ng per milliliter in controls (P<0.001). The mean serum level in women with preeclampsia at term was 31.0 ng per milliliter, as compared with 13.3 ng per milliliter in controls (P<0.001). Beginning at 17 weeks through 20 weeks of gestation, soluble endoglin levels were significantly higher in women in whom preterm preeclampsia later developed than in controls (10.2 ng per milliliter vs. 5.8 ng per milliliter, P<0.001), and at 25 through 28 weeks of gestation, the levels were significantly higher in women in whom term preeclampsia developed than in controls (8.5 ng per milliliter vs. 5.9 ng per milliliter, P<0.001). An increased level of soluble endoglin was usually accompanied by an increased ratio of sFlt1:PlGF. The risk of preeclampsia was greatest among women in the highest quartile of the control distributions for both biomarkers but not for either biomarker alone. Rising circulating levels of soluble endoglin and ratios of sFlt1:PlGF herald the onset of preeclampsia. Copyright 2006 Massachusetts Medical Society.

                Author and article information

                Journal
                Cardiovasc Res
                cvrese
                cardiovascres
                Cardiovascular Research
                Oxford University Press
                0008-6363
                1755-3245
                15 February 2011
                7 December 2010
                7 December 2010
                : 89
                : 3 , Review Focus on: Inorganic Nitrite and Nitrate in Cardiovascular Health and Disease
                : 671-679
                Affiliations
                [1 ]Centre for Trophoblast Research, Department of Physiology, Development and Neurosciencesimple, University of Cambridge , Downing Street, Cambridge CB2 3EG, UK
                [2 ]Department of Obstetrics and Gynaecology, simpleUniversity of Cambridge , Cambridge, UK
                [3 ]Cambridge Comprehensive Biomedical Research Centre, simpleCambridge , UK
                Author notes
                [* ]Corresponding author. Tel: +44 1223 333893; fax: +44 1223 333786, Email: gjb2@ 123456cam.ac.uk
                [†]

                These authors contributed equally to the study.

                Article
                cvq346
                10.1093/cvr/cvq346
                3028975
                21139021
                c7f0cd7d-4a34-4f91-8a7e-f2b35fd9df13
                Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2010. For permissions please email: journals.permissions@oxfordjournals.org.

                The online version of this article has been published under an open access model. Users are entitled to use, reproduce, disseminate, or display the open access version of this article for non-commercial purposes provided that the original authorship is properly and fully attributed; the Journal, Learned Society and Oxford University Press are attributed as the original place of publication with correct citation details given; if an article is subsequently reproduced or disseminated not in its entirety but only in part or as a derivative work this must be clearly indicated. For commercial re-use, please contact journals.permissions@oxfordjournals.org.

                History
                : 19 February 2010
                : 12 October 2010
                : 29 October 2010
                Categories
                Original Articles
                Custom metadata
                Time for primary review: 36 days

                Cardiovascular Medicine
                pre-eclampsia,endothelial dysfunction,sflt1
                Cardiovascular Medicine
                pre-eclampsia, endothelial dysfunction, sflt1

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