Maternal PlGF and umbilical Dopplers predict pregnancy outcomes at diagnosis of early-onset fetal growth restriction

BACKGROUNDSevere, early-onset fetal growth restriction (FGR) causes significant fetal and neonatal mortality and morbidity. Predicting the outcome of affected pregnancies at the time of diagnosis is difficult, thus preventing accurate patient counseling. We investigated the use of maternal serum protein and ultrasound measurements at diagnosis to predict fetal or neonatal death and 3 secondary outcomes: fetal death or delivery at or before 28+0 weeks, development of abnormal umbilical artery (UmA) Doppler velocimetry, and slow fetal growth.METHODSWomen with singleton pregnancies (n = 142, estimated fetal weights [EFWs] below the third centile, less than 600 g, 20+0 to 26+6 weeks of gestation, no known chromosomal, genetic, or major structural abnormalities) were recruited from 4 European centers. Maternal serum from the discovery set (n = 63) was analyzed for 7 proteins linked to angiogenesis, 90 additional proteins associated with cardiovascular disease, and 5 proteins identified through pooled liquid chromatography and tandem mass spectrometry. Patient and clinician stakeholder priorities were used to select models tested in the validation set (n = 60), with final models calculated from combined data.RESULTSThe most discriminative model for fetal or neonatal death included the EFW z score (Hadlock 3 formula/Marsal chart), gestational age, and UmA Doppler category (AUC, 0.91; 95% CI, 0.86-0.97) but was less well calibrated than the model containing only the EFW z score (Hadlock 3/Marsal). The most discriminative model for fetal death or delivery at or before 28+0 weeks included maternal serum placental growth factor (PlGF) concentration and UmA Doppler category (AUC, 0.89; 95% CI, 0.83-0.94).CONCLUSIONUltrasound measurements and maternal serum PlGF concentration at diagnosis of severe, early-onset FGR predicted pregnancy outcomes of importance to patients and clinicians.TRIAL REGISTRATIONClinicalTrials.gov NCT02097667.FUNDINGThe European Union, Rosetrees Trust, Mitchell Charitable Trust.

Mechanisms of Acquired Resistance to Anti-VEGF Therapy for Neovascular Eye Diseases

Purpose

The purpose of this study was to evaluate clinical reports of response-loss in patients with neovascular eye diseases, such as neovascular age-related macular degeneration (AMD) and diabetic macular edema (DME), after repeated anti-vascular endothelial growth factor (VEGF) therapy. To assess experimental evidence of associations of other angiogenic growth factors and endothelial glycolytic pathways with the diseases and to propose the underlying mechanisms.

Methods

Review of published clinical studies and experimental investigations.

Results

Intravitreal injection of anti-VEGF biologic drugs (e.g. bevacizumab, ranibizumab, and aflibercept) is the front-line treatment for neovascular AMD and DME, and acts by halting the progression of excess blood vessel growth and leakage. Despite favorable clinical results, exudation returns in a number of patients after repeated administrations over time. Patients suffering from disease recurrence may have developed an acquired resistance to anti-VEGF therapy. We have analyzed clinical and preclinical findings on changes to angiogenic signaling pathways following VEGF-targeted treatment and hypothesize that switching to alternative pathways could potentially bypass VEGF blockade, accounting for development of resistance to anti-VEGF therapy. We have also discussed potential reprogramming of ocular endothelial glycolysis in response to VEGF antagonism and proposed that metabolic adaptations could impair blood-retinal barrier function, counteracting the clinical efficacy of VEGF-targeted therapies and contributing to a decline of response to them.

Conclusions

Future studies of the mechanisms proposed in this review may shed some light on how these adaptations result in the development of acquired resistance to anti-VEGF therapy, which should help discover new therapeutic strategies for overcoming anti-VEGF resistance and improving clinical efficacy.

Macrophage-specific deletion of neuropilin-2 inhibits inflammatory signalling and attenuates atherosclerotic plaque development in apolipoprotein e-deficient mice

Background

Atherosclerosis is the underlying pathology in most cases of ischaemic heart disease, which itself remains the leading cause of mortality worldwide. Atherosclerosis is a multifaceted vascular disease characterised by arterial wall inflammation resulting from the subendothelial retention, and modification, of lipoproteins by macrophages. Macrophages exhibit a high degree of plasticity, and undergo polarisation to a pro-inflammatory phenotype in response to pro-inflammatory cytokines and other environmental stimuli, making them an attractive therapeutic target. Neuropilin-2 (NRP2) is a cell-surface co-receptor with essential roles in angiogenesis and axonal guidance, and is also expressed by macrophages. However, little is known about the role of NRP2 in macrophage function or atherosclerosis.

Purpose

To investigate whether NRP2 is important for macrophage involvement in atherosclerosis, we characterised the effects of conditional NRP2 deletion on macrophage function and atherosclerotic plaque development.

Methods

We generated mice with macrophage-specific (LysM-Cre) deletion of Nrp2, and lineage tracing via EYFP transgene expression, on the pro-atherogenic Apolipoprotein E-deficient background (Nrp2-KOMac, Apoe−/−, EYFP). These mice were fed a high-fat diet (HFD) for 16 weeks before their aortas were stained with Oil-red-O to assess plaque coverage. Plaque content was then characterised by sectioning and staining the aortic roots. The role of NRP2 in modulating pro-inflammatory macrophage polarisation and signalling, was assessed using functional assays and transcriptome analysis in Nrp2-KO bone marrow-derived macrophages (BMDMs).

Results

HFD-induced plaque development was significantly reduced in Nrp2-KOMac, Apoe−/−, EYFP mice, with 17.4% total aortic plaque coverage in Nrp2-KOMac, Apoe−/−, EYFP mice, compared to 24.9% in WTApoe−/−, EYFP mice (p=0.0021, n=10). Plaques from Nrp2-KOMac, Apoe−/−, EYFP mice also displayed features consistent with increased plaque stability, including reduced necrotic core area and plaque lipid content, and increased cap thickness. NRP2 was significantly upregulated upon M-CSF-mediated differentiation of bone marrow progenitors into BMDMs, and further upregulated by pro-inflammatory polarisation using LPS and IFN-gamma. Furthermore, upregulation of Il1β, Tnfα and Il6, induced by LPS and IFN-gamma, was significantly reduced in Nrp2-KO BMDMs, and MCP-1 induced migration was also decreased in these cells. Transcriptome analysis revealed that NF-kappaB signalling pathway genes, and genes regulating monocyte chemotaxis, were downregulated in Nrp2-KO BMDMs.

Conclusion

Macrophage-derived NRP2 is pro-atherogenic, likely resulting from its role in positively regulating pro-inflammatory signalling and macrophage migration. Targeting NRP2 expressed on the surface of macrophages could therefore offer a novel therapeutic approach for reducing the disease burden associated with atherosclerosis.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation (MB PhD Studentship)

Bcar1/p130Cas is essential for ventricular development and neural crest cell remodelling of the cardiac outflow tract

AIMS

The adapter protein p130Cas, encoded by the Bcar1 gene, is a key regulator of cell movement, adhesion, and cell cycle control in diverse cell types. Bcar1 constitutive knockout mice are embryonic lethal by embryonic days (E) 11.5-12.5, but the role of Bcar1 in embryonic development remains unclear. Here, we investigated the role of Bcar1 specifically in cardiovascular development and defined the cellular and molecular mechanisms disrupted following targeted Bcar1 deletions.

METHODS AND RESULTS

We crossed Bcar1 floxed mice with Cre transgenic lines allowing for cell-specific knockout either in smooth muscle and early cardiac tissues (SM22-Cre), mature smooth muscle cells (smMHC-Cre), endothelial cells (Tie2-Cre), second heart field cells (Mef2c-Cre), or neural crest cells (NCC) (Pax3-Cre) and characterized these conditional knock outs using a combination of histological and molecular biology techniques. Conditional knockout of Bcar1 in SM22-expressing smooth muscle cells and cardiac tissues (Bcar1SM22KO) was embryonically lethal from E14.5-15.5 due to severe cardiovascular defects, including abnormal ventricular development and failure of outflow tract (OFT) septation leading to a single outflow vessel reminiscent of persistent truncus arteriosus. SM22-restricted loss of Bcar1 was associated with failure of OFT cushion cells to undergo differentiation to septal mesenchymal cells positive for SMC-specific α-actin, and disrupted expression of proteins and transcription factors involved in epithelial-to-mesenchymal transformation (EMT). Furthermore, knockout of Bcar1 specifically in NCC (Bcar1PAX3KO) recapitulated part of the OFT septation and aortic sac defects seen in the Bcar1SM22KO mutants, indicating a cell-specific requirement for Bcar1 in NCC essential for OFT septation. In contrast, conditional knockouts of Bcar1 in differentiated smooth muscle, endothelial cells, and second heart field cells survived to term and were phenotypically normal at birth and postnatally.

CONCLUSION

Our work reveals a cell-specific requirement for Bcar1 in NCC, early myogenic and cardiac cells, essential for OFT septation, myocardialization and EMT/cell cycle regulation and differentiation to myogenic lineages.

Comparison of Efficiency and Function of Vascular Endothelial Growth Factor Adenovirus Vectors in Endothelial Cells for Gene Therapy of Placental Insufficiency

Severe fetal growth restriction (FGR) affects 1:500 pregnancies, is untreatable and causes serious neonatal morbidity and death. Reduced uterine blood flow (UBF) and lack of bioavailable VEGF due to placental insufficiency is a major cause. Transduction of uterine arteries in normal or FGR sheep and guinea pigs using an adenovirus (Ad) encoding VEGF isoforms A (Ad.VEGF-A₁₆₅) and a FLAG-tagged pre-processed short form D (D^ΔNΔC, Ad.VEGF-D^ΔNΔC-FLAG) increases endothelial nitric oxide expression, enhances relaxation and reduces constriction of the uterine arteries and their branches. UBF and angiogenesis are increased long term, improving fetal growth in utero. For clinical trial development we compared Ad.VEGF vector transduction efficiency and function in endothelial cells (ECs) derived from different species. We aimed to compare the transduction efficiency and function of the pre-clinical study Ad. constructs (Ad.VEGF-A₁₆₅, Ad.VEGF-D^ΔNΔC-FLAG) with the intended clinical trial construct (Ad.VEGF-D^ΔNΔC) where the FLAG tag is removed. We infected ECs from human umbilical vein, pregnant sheep uterine artery, pregnant guinea pig aorta and non-pregnant rabbit aorta, with increasing multiplicity of infection (MOI) for 24 or 48 hours of three Ad.VEGF vectors, compared to control Ad. containing the LacZ gene (Ad.LacZ). VEGF supernatant expression was analysed by ELISA. Functional assessment used tube formation assay and Erk-Akt phosphorylation by ELISA. VEGF expression was higher after Ad.VEGF-D^ΔNΔC-FLAG and Ad.VEGF-D^ΔNΔC transduction compared to Ad.VEGF-A₁₆₅ in all EC types (*p < 0.001). Tube formation was higher in ECs transduced with Ad.VEGF-D^ΔNΔC in all species compared to other constructs (***p < 0.001, *p < 0.05 with rabbit aortic ECs). Phospho-Erk and phospho-Akt assays displayed no differences between the three vector constructs, whose effect was, as in other experiments, higher than Ad.LacZ (***p < 0.001). In conclusion, we observed high transduction efficiency and functional effects of Ad.VEGF-D^ΔNΔC vector with comparability in major pathway activation to constructs used in pre-clinical studies, supporting its use in a clinical trial.

Public health delivery in the information age: the role of informatics and technology

AIM

Public health systems have embraced health informatics and information technology as a potential transformational tool to improve real-time surveillance systems, communication, and sharing of information among various agencies. Global pandemic outbreaks like Zika and Ebola were quickly controlled due to electronic surveillance systems enabling efficient information access and exchange. However, there is the need for a more robust technology to enhance adequate epidemic forecasting, data sharing, and effective communication. The purpose of this review was to examine the use of informatics and information technology tools and its impact on public health delivery.

METHOD

Investigators searched six electronic databases. These were MEDLINE, Cumulative Index to Nursing and Allied Health Literature (CINAHL) Complete, Cochrane Database of Systematic Reviews, COMPENDEX, Scopus, and Academic Search Premier from January 2000 to 31 March 2016.

RESULTS

A total of 60 articles met the eligibility criteria for inclusion. These studies were organized into three areas as (1) definition of the term public health informatics; (2) type of public health surveillance systems and implications for public health; and (3) electronic surveillance systems functionality, capability, training, and challenges. Our analysis revealed that due to the growing expectations to provide real-time response and population-centered evidence-based public health in this information-driven age there has been a surge in informatics and information technology adoption. Education and training programs are now available to equip public health students and professionals with skills in public health informatics. However, obstacles including interoperability, data standardization, privacy, and technology transfer persist.

CONCLUSION

Re-engineering the delivery of public health is necessary to meet the demands of the 21st century and beyond. To meet this expectation, public health must invest in workforce development and capacity through education and training in informatics.

VEGF (Vascular Endothelial Growth Factor) Induces NRP1 (Neuropilin-1) Cleavage via ADAMs (a Disintegrin and Metalloproteinase) 9 and 10 to Generate Novel Carboxy-Terminal NRP1 Fragments That Regulate Angiogenic Signaling

Objective- NRP1(neuropilin-1) acts as a coreceptor for VEGF (vascular endothelial growth factor) with an essential role in angiogenesis. Recent findings suggest that posttranslational proteolytic cleavage of VEGF receptors may be an important mechanism for regulating angiogenesis, but the role of NRP1 proteolysis and the NRP1 species generated by cleavage in endothelial cells is not known. Here, we characterize NRP1 proteolytic cleavage in endothelial cells, determine the mechanism, and investigate the role of NRP1 cleavage in regulation of endothelial cell function. Approach and Results- NRP1 species comprising the carboxy (C)-terminal and transmembrane NRP1 domains but lacking the ligand-binding A and B regions are constitutively expressed in endothelial cells. Generation of these C-terminal domain NRP1 proteins is upregulated by phorbol ester and Ca²⁺ ionophore, and reduced by pharmacological inhibition of metalloproteinases, by small interfering RNA-mediated knockdown of 2 members of ADAM (a disintegrin and metalloproteinase) family, ADAMs 9 and 10, and by a specific ADAM10 inhibitor. Furthermore, VEGF upregulates expression of these NRP1 species in an ADAM9/10-dependent manner. Transduction of endothelial cells with adenoviral constructs expressing NRP1 C-terminal domain fragments inhibited VEGF-induced phosphorylation of VEGFR2 (VEGF receptor tyrosine kinase)/KDR (kinase domain insert receptor) and decreased VEGF-stimulated endothelial cell motility and angiogenesis in coculture and aortic ring sprouting assays. Conclusions- These findings identify novel NRP1 species in endothelial cells and demonstrate that regulation of NRP1 proteolysis via ADAMs 9 and 10 is a new regulatory pathway able to modulate VEGF angiogenic signaling.

Smooth muscle cell-specific knockout of neuropilin-1 impairs postnatal lung development and pathological vascular smooth muscle cell accumulation

Neuropilin 1 (NRP1) is important for neuronal and cardiovascular development due to its role in conveying class 3 semaphorin and vascular endothelial growth factor signaling, respectively. NRP1 is expressed in smooth muscle cells (SMCs) and mediates their migration and proliferation in cell culture and is implicated in pathological SMC remodeling in vivo. To address the importance of Nrp1 for SMC function during development, we generated conditional inducible Nrp1 SMC-specific knockout mice. Induction of early postnatal SMC-specific Nrp1 knockout led to pulmonary hemorrhage associated with defects in alveogenesis and revealed a specific requirement for Nrp1 in myofibroblast recruitment to the alveolar septae and PDGF-AA-induced migration in vitro. Furthermore, SMC-specific Nrp1 knockout inhibited PDGF-BB-stimulated SMC outgrowth ex vivo in aortic ring assays and reduced pathological arterial neointima formation in vivo. In contrast, we observed little significant effect of SMC-specific Nrp1 knockout on neonatal retinal vascularization. Our results point to a requirement of Nrp1 in vascular smooth muscle and myofibroblast function in vivo, which may have relevance for postnatal lung development and for pathologies characterized by excessive SMC and/or myofibroblast proliferation.

Architecture and hydration of the arginine-binding site of neuropilin-1

Neuropilin‐1 (NRP1) is a transmembrane co‐receptor involved in binding interactions with variety of ligands and receptors, including receptor tyrosine kinases. Expression of NRP1 in several cancers correlates with cancer stages and poor prognosis. Thus, NRP1 has been considered a therapeutic target and is the focus of multiple drug discovery initiatives. Vascular endothelial growth factor (VEGF) binds to the b1 domain of NRP1 through interactions between the C‐terminal arginine of VEGF and residues in the NRP1‐binding site including Tyr297, Tyr353, Asp320, Ser346 and Thr349. We obtained several complexes of the synthetic ligands and the NRP1‐b1 domain and used X‐ray crystallography and computational methods to analyse atomic details and hydration profile of this binding site. We observed side chain flexibility for Tyr297 and Asp320 in the six new high‐resolution crystal structures of arginine analogues bound to NRP1. In addition, we identified conserved water molecules in binding site regions which can be targeted for drug design. The computational prediction of the VEGF ligand‐binding site hydration map of NRP1 was in agreement with the experimentally derived, conserved hydration structure. Displacement of certain conserved water molecules by a ligand's functional groups may contribute to binding affinity, whilst other water molecules perform as protein–ligand bridges. Our report provides a comprehensive description of the binding site for the peptidic ligands’ C‐terminal arginines in the b1 domain of NRP1, highlights the importance of conserved structural waters in drug design and validates the utility of the computational hydration map prediction method in the context of neuropilin.

Database

The structures were deposited to the PDB with accession numbers PDB ID: 5IJR, 5IYY, 5JHK, 5J1X, 5JGQ, 5JGI.

Maternal Therapy with Ad.VEGF-A165 Increases Fetal Weight at Term in a Guinea-Pig Model of Fetal Growth Restriction

In a model of growth-restricted sheep pregnancy, it was previously demonstrated that transient uterine artery VEGF overexpression can improve fetal growth. This approach was tested in guinea-pig pregnancies, where placental physiology is more similar to humans. Fetal growth restriction (FGR) was attained through peri-conceptual nutrient restriction in virgin guinea pigs. Ad.VEGF-A₁₆₅ or Ad.LacZ (1 × 10¹⁰vp) was applied at mid-gestation via laparotomy, delivered externally to the uterine circulation with thermosensitive gel. At short-term (3-8 days post surgery) or at term gestation, pups were weighed, and tissues were sampled for vector spread analysis, VEGF expression, and its downstream effects. Fetal weight at term was increased (88.01 ± 13.36 g; n = 26) in Ad.VEGF-A₁₆₅-treated animals compared with Ad.LacZ-treated animals (85.52 ± 13.00 g; n = 19; p = 0.028). The brain, liver, and lung weight and crown rump length were significantly larger in short-term analyses, as well as VEGF expression in transduced tissues. At term, molecular analyses confirmed the presence of VEGF transgene in target tissues but not in fetal samples. Tissue histology analysis and blood biochemistry/hematological examination were comparable with controls. Uterine artery relaxation in Ad.VEGF-A₁₆₅-treated dams was higher compared with Ad.LacZ-treated dams. Maternal uterine artery Ad.VEGF-A₁₆₅ increases fetal growth velocity and term fetal weight in growth-restricted guinea-pig pregnancy.

Structural studies of neuropilin-2 reveal a zinc ion binding site remote from the vascular endothelial growth factor binding pocket

Neuropilin-2 is a transmembrane receptor involved in lymphangiogenesis and neuronal development. In adults, neuropilin-2 and its homologous protein neuropilin-1 have been implicated in cancers and infection. Molecular determinants of the ligand selectivity of neuropilins are poorly understood. We have identified and structurally characterized a zinc ion binding site on human neuropilin-2. The neuropilin-2-specific zinc ion binding site is located near the interface between domains b1 and b2 in the ectopic region of the protein, remote from the neuropilin binding site for its physiological ligand, i.e. vascular endothelial growth factor. We also present an X-ray crystal structure of the neuropilin-2 b1 domain in a complex with the C-terminal sub-domain of VEGF-A. Zn(2+) binding to neuropilin-2 destabilizes the protein structure but this effect was counteracted by heparin, suggesting that modifications by glycans and zinc in the extracellular matrix may affect functional neuropilin-2 ligand binding and signalling activity.

Gene Targeting to the Uteroplacental Circulation of Pregnant Guinea Pigs

Our study aimed to target adenoviral gene therapy to the uteroplacental circulation of pregnant guinea pigs in order to develop a novel therapy for fetal growth restriction. Four methods of delivery of an adenovirus encoding β-galactosidase (Ad.LacZ) were evaluated: intravascular injection using phosphate-buffered saline (PBS) into (1) uterine artery (UtA) or (2) internal iliac artery or external administration in (3) PBS or (4) pluronic F-127 gel (Sigma Aldrich). Postmortem examination was performed 4 to 7 days after gene transfer. Tissue transduction was assessed by X-gal histochemistry and enzyme-linked immunosorbent assay. External vascular application of the adenovirus vector in combination with pluronic gel had 91.7% success rate in terms of administration (85% maternal survival) and gave the best results for maternal/fetal survival and local transduction efficiency without any spread to maternal or fetal tissues. This study suggests an optimal method of gene delivery to the UtAs of a small rodent for preclinical studies.

Neuropilins 1 and 2 mediate neointimal hyperplasia and re-endothelialization following arterial injury

Aims

Neuropilins 1 and 2 (NRP1 and NRP2) play crucial roles in endothelial cell migration contributing to angiogenesis and vascular development. Both NRPs are also expressed by cultured vascular smooth muscle cells (VSMCs) and are implicated in VSMC migration stimulated by PDGF-BB, but it is unknown whether NRPs are relevant for VSMC function in vivo. We investigated the role of NRPs in the rat carotid balloon injury model, in which endothelial denudation and arterial stretch induce neointimal hyperplasia involving VSMC migration and proliferation.

Methods and results

NRP1 and NRP2 mRNAs and proteins increased significantly following arterial injury, and immunofluorescent staining revealed neointimal NRP expression. Down-regulation of NRP1 and NRP2 using shRNA significantly reduced neointimal hyperplasia following injury. Furthermore, inhibition of NRP1 by adenovirally overexpressing a loss-of-function NRP1 mutant lacking the cytoplasmic domain (ΔC) reduced neointimal hyperplasia, whereas wild-type (WT) NRP1 had no effect. NRP-targeted shRNAs impaired, while overexpression of NRP1 WT and NRP1 ΔC enhanced, arterial re-endothelialization 14 days after injury. Knockdown of either NRP1 or NRP2 inhibited PDGF-BB-induced rat VSMC migration, whereas knockdown of NRP2, but not NRP1, reduced proliferation of cultured rat VSMC and neointimal VSMC in vivo. NRP knockdown also reduced the phosphorylation of PDGFα and PDGFβ receptors in rat VSMC, which mediate VSMC migration and proliferation.

Conclusion

NRP1 and NRP2 play important roles in the regulation of neointimal hyperplasia in vivo by modulating VSMC migration (via NRP1 and NRP2) and proliferation (via NRP2), independently of the role of NRPs in re-endothelialization.

NRP1 Regulates CDC42 Activation to Promote Filopodia Formation in Endothelial Tip Cells

Sprouting blood vessels are led by filopodia-studded endothelial tip cells that respond to angiogenic signals. Mosaic lineage tracing previously revealed that NRP1 is essential for tip cell function, although its mechanistic role in tip cells remains poorly defined. Here, we show that NRP1 is dispensable for genetic tip cell identity. Instead, we find that NRP1 is essential to form the filopodial bursts that distinguish tip cells morphologically from neighboring stalk cells, because it enables the extracellular matrix (ECM)-induced activation of CDC42, a key regulator of filopodia formation. Accordingly, NRP1 knockdown and pharmacological CDC42 inhibition similarly impaired filopodia formation in vitro and in developing zebrafish in vivo. During mouse retinal angiogenesis, CDC42 inhibition impaired tip cell and vascular network formation, causing defects that resembled those due to loss of ECM-induced, but not VEGF-induced, NRP1 signaling. We conclude that NRP1 enables ECM-induced filopodia formation for tip cell function during sprouting angiogenesis.

Local over-expression of VEGF-DΔNΔC in the uterine arteries of pregnant sheep results in long-term changes in uterine artery contractility and angiogenesis

Background

The normal development of the uteroplacental circulation in pregnancy depends on angiogenic and vasodilatory factors such as vascular endothelial growth factor (VEGF). Reduced uterine artery blood flow (UABF) is a common cause of fetal growth restriction; abnormalities in angiogenic factors are implicated. Previously we showed that adenovirus (Ad)-mediated VEGF-A₁₆₅ expression in the pregnant sheep uterine artery (UtA) increased nitric oxide synthase (NOS) expression, altered vascular reactivity and increased UABF. VEGF-D is a VEGF family member that promotes angiogenesis and vasodilatation but, in contrast to VEGF-A, does not increase vascular permeability. Here we examined the effect of Ad.VEGF-D^ΔNΔC vector encoding a fully processed form of VEGF-D, on the uteroplacental circulation.

Methods

UtA transit-time flow probes and carotid artery catheters were implanted in mid-gestation pregnant sheep (n = 5) to measure baseline UABF and maternal haemodynamics respectively. 7–14 days later, after injection of Ad.VEGF-D^ΔNΔC vector (5×10¹¹ particles) into one UtA and an Ad vector encoding β-galactosidase (Ad.LacZ) contralaterally, UABF was measured daily until scheduled post-mortem examination at term. UtAs were assessed for vascular reactivity, NOS expression and endothelial cell proliferation; NOS expression was studied in ex vivo transduced UtA endothelial cells (UAECs).

Results

At 4 weeks post-injection, Ad.VEGF-D^ΔNΔC treated UtAs showed significantly lesser vasoconstriction (E_max144.0 v/s 184.2, p = 0.002). There was a tendency to higher UABF in Ad.VEGF-D^ΔNΔC compared to Ad.LacZ transduced UtAs (50.58% v/s 26.94%, p = 0.152). There was no significant effect on maternal haemodynamics. An increased number of proliferating endothelial cells and adventitial blood vessels were observed in immunohistochemistry. Ad.VEGF-D^ΔNΔC expression in cultured UAECs upregulated eNOS and iNOS expression.

Conclusions

Local over-expression of VEGF-D^ΔNΔC in the UtAs of pregnant mid-gestation sheep reduced vasoconstriction, promoted endothelial cell proliferation and showed a trend towards increased UABF. Studies in cultured UAECs indicate that VEGF-D^ΔNΔC may act in part through upregulation of eNOS and iNOS.

Neuropilin 1 (NRP1) hypomorphism combined with defective VEGF-A binding reveals novel roles for NRP1 in developmental and pathological angiogenesis

Neuropilin 1 (NRP1) is a receptor for class 3 semaphorins and vascular endothelial growth factor (VEGF) A and is essential for cardiovascular development. Biochemical evidence supports a model for NRP1 function in which VEGF binding induces complex formation between NRP1 and VEGFR2 to enhance endothelial VEGF signalling. However, the relevance of VEGF binding to NRP1 for angiogenesis in vivo has not yet been examined. We therefore generated knock-in mice expressing Nrp1 with a mutation of tyrosine (Y) 297 in the VEGF binding pocket of the NRP1 b1 domain, as this residue was previously shown to be important for high affinity VEGF binding and NRP1-VEGFR2 complex formation. Unexpectedly, this targeting strategy also severely reduced NRP1 expression and therefore generated a NRP1 hypomorph. Despite the loss of VEGF binding and attenuated NRP1 expression, homozygous Nrp1^Y297A/Y297A mice were born at normal Mendelian ratios, arguing against NRP1 functioning exclusively as a VEGF₁₆₄ receptor in embryonic angiogenesis. By overcoming the mid-gestation lethality of full Nrp1-null mice, homozygous Nrp1^Y297A/Y297A mice revealed essential roles for NRP1 in postnatal angiogenesis and arteriogenesis in the heart and retina, pathological neovascularisation of the retina and angiogenesis-dependent tumour growth.

Neuropilins: role in signalling, angiogenesis and disease

Neuropilins (NRPs) are co-receptors for class 3 semaphorins and for members of the vascular endothelial growth factor (VEGF) family of angiogenic cytokines. Genetic analysis of the role of NRPs in mice shows that NRP1 is essential for embryonic neuronal pathfinding and cardiovascular development, mediated via semaphorins and VEGF, respectively, while NRP2 has a more restricted role in neuronal patterning and lymphangiogenesis. NRPs are thought to mediate functional responses, most importantly cell migration, as a result of complex formation with other receptors, such as plexins in the case of semaphorins and the VEGF receptor, VEGFR2, resulting in enhanced signalling via some intracellular pathways. Recent findings indicate that NRPs may have important biological roles in other physiological and disease-related processes. In particular, NRPs are highly expressed in diverse tumour cell lines and human neoplasms and have been implicated in several biological processes regulating tumour growth in vivo, suggesting that NRP1 may be a future therapeutic target in cancer.

Production of soluble human vascular endothelial growth factor VEGF-A165-heparin binding domain in Escherichia coli

We report a method for production of soluble heparin binding domain (HBD) of human vascular endothelial growth factor VEGF-A₁₆₅. Recombinant VEGF-A₁₆₅-HBD that contains four disulphide bridges was expressed in specialised E. coli SHuffle cells and its activity has been confirmed through interactions with neuropilin and heparin. The ability to produce significant quantities of a soluble active form of VEGF-A₁₆₅-HBD will enable further studies addressing the role of VEGF-A in essential processes such as angiogenesis, vasculogenesis and vascular permeability.

Therapeutic angiogenesis for cardiovascular disease: biological context, challenges, prospects

Since the discovery of vascular endothelial growth factor (VEGF), therapeutic angiogenesis has attracted interest as an alternative treatment for ischaemic heart and peripheral disease. In parallel, the view has also gained ground that angiogenesis has an important role in the pathogenesis of atherosclerotic disease and its clinical sequelae. These conflicting perspectives have both been based on a large quantity of preclinical data obtained from mainly small rodent models of disease. However, in recent years further research and the results of clinical trials of pro-angiogenic and anti-angiogenic treatments have provided new insights into the impact of VEGF and other angiogenesis-based approaches on human health and disease. This review discusses therapeutic angiogenesis in the light of recent scientific advances and clinical evidence, and considers the future challenges and prospects for therapeutic angiogenesis.

Small molecule inhibitors of the neuropilin-1 vascular endothelial growth factor A (VEGF-A) interaction

We report the molecular design and synthesis of EG00229, 2, the first small molecule ligand for the VEGF-A receptor neuropilin 1 (NRP1) and the structural characterization of NRP1-ligand complexes by NMR spectroscopy and X-ray crystallography. Mutagenesis studies localized VEGF-A binding in the NRP1 b1 domain and a peptide fragment of VEGF-A was shown to bind at the same site by NMR, providing the basis for small molecule design. Compound 2 demonstrated inhibition of VEGF-A binding to NRP1 and attenuated VEGFR2 phosphorylation in endothelial cells. Inhibition of migration of endothelial cells was also observed. The viability of A549 lung carcinoma cells was reduced by 2, and it increased the potency of the cytotoxic agents paclitaxel and 5-fluorouracil when given in combination. These studies provide the basis for design of specific small molecule inhibitors of ligand binding to NRP1.

Hostility and physiological responses to laboratory stress in acute coronary syndrome patients

OBJECTIVE

Evidence suggests that emotional stress can trigger acute coronary syndromes in patients with advanced coronary artery disease (CAD), although the mechanisms involved remain unclear. Hostility is associated with heightened reactivity to stress in healthy individuals, and with an elevated risk of adverse cardiac events in CAD patients. This study set out to test whether hostile individuals with advanced CAD were also more stress responsive.

METHODS

Thirty-four men (aged 55.9+/-9.3 years) who had recently survived an acute coronary syndrome took part in laboratory testing. Trait hostility was assessed by the Cook Medley Hostility Scale, and cardiovascular activity, salivary cortisol, and plasma concentrations of interleukin-6 were assessed at baseline, during performance of two mental tasks, and during a 2-h recovery.

RESULTS

Participants with higher hostility scores had heightened systolic and diastolic blood pressure (BP) reactivity to tasks (both P<.05), as well as a more sustained increase in systolic BP at 2 h post-task (P=.024), independent of age, BMI, smoking status, medication, and baseline BP. Hostility was also associated with elevated plasma interleukin-6 (IL-6) levels at 75 min (P=.023) and 2 h (P=.016) poststress and was negatively correlated with salivary cortisol at 75 min (P=.034).

CONCLUSION

Hostile individuals with advanced cardiovascular disease may be particularly susceptible to stress-induced increases in sympathetic activity and inflammation. These mechanisms may contribute to an elevated risk of emotionally triggered cardiac events in such patients.

A phosphoinositide 3-kinase/phospholipase Cgamma1 pathway regulates fibroblast growth factor-induced capillary tube formation

BACKGROUND

The fibroblast growth factors (FGFs) are key regulators of embryonic development, tissue homeostasis and tumour angiogenesis. Binding of FGFs to their receptor(s) results in activation of several intracellular signalling cascades including phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC)gamma1. Here we investigated the basic FGF (FGF-2)-mediated activation of these enzymes in human umbilical vein endothelial cells (HUVECs) and defined their role in FGF-2-dependent cellular functions.

METHODOLOGY/PRINCIPAL FINDINGS

We show that FGF-2 activates PLCgamma1 in HUVECs measured by analysis of total inositol phosphates production upon metabolic labelling of cells and intracellular calcium increase. We further demonstrate that FGF-2 activates PI3K, assessed by analysing accumulation of its lipid product phosphatidylinositol-3,4,5-P(3) using TLC and confocal microscopy analysis. PI3K activity is required for FGF-2-induced PLCgamma1 activation and the PI3K/PLCgamma1 pathway is involved in FGF-2-dependent cell migration, determined using Transwell assay, and in FGF-2-induced capillary tube formation (tubulogenesis assays in vitro). Finally we show that PI3K-dependent PLCgamma1 activation regulates FGF-2-mediated phosphorylation of Akt at its residue Ser473, determined by Western blotting analysis. This occurs through protein kinase C (PKC)alpha activation since dowregulation of PKCalpha expression using specific siRNA or blockade of its activity using chemical inhibition affects the FGF-2-dependent Ser473 Akt phosphorylation. Furthermore inhibition of PKCalpha blocks FGF-2-dependent cell migration.

CONCLUSION/SIGNIFICANCE

These data elucidate the role of PLCgamma1 in FGF-2 signalling in HUVECs demonstrating its key role in FGF-2-dependent tubulogenesis. Furthermore these data unveil a novel role for PLCgamma1 as a mediator of PI3K-dependent Akt activation and as a novel key regulator of different Akt-dependent processes.

The ADMA/DDAH pathway regulates VEGF-mediated angiogenesis

OBJECTIVE

Asymmetrical dimethylarginine (ADMA) is a nitric oxide synthase (NOS) inhibitor and cardiovascular risk factor associated with angiogenic disorders. Enzymes metabolising ADMA, dimethylarginine dimethylaminohydrolases (DDAH) promote angiogenesis, but the mechanisms are not clear. We hypothesized that ADMA/DDAH modifies endothelial responses to vascular endothelial growth factor (VEGF) by affecting activity of Rho GTPases, regulators of actin polymerization, and focal adhesion dynamics.

METHODS AND RESULTS

The effects of ADMA on VEGF-induced endothelial cell motility, focal adhesion turnover, and angiogenesis were studied in human umbilical vein endothelial cells (HUVECs) and DDAH I heterozygous knockout mice. ADMA inhibited VEGF-induced chemotaxis in vitro and angiogenesis in vitro and in vivo in an NO-dependent way. ADMA effects were prevented by overexpression of DDAH but were not associated with decreased proliferation, increased apoptosis, or changes in VEGFR-2 activity or expression. ADMA inhibited endothelial cell polarization, protrusion formation, and decreased focal adhesion dynamics, resulting from Rac1 inhibition after decrease in phosphorylation of vasodilator stimulated phosphoprotein (VASP). Constitutively active Rac1, and to a lesser extent dominant negative RhoA, abrogated ADMA effects in vitro and in vivo.

CONCLUSIONS

The ADMA/DDAH pathway regulates VEGF-induced angiogenesis in an NO- and Rac1-dependent manner.

Endothelial cell confluence regulates Weibel-Palade body formation

Secretory granules called Weibel-Palade bodies (WPBs) containing Von Willebrand factor (VWF) are characteristic of the mammalian endothelium. We hypothesized that vascular-specific antigens such as VWF are linked to endothelial identity and proliferation in vitro. To test this idea, the cellular accumulation of VWF in WPBs was monitored as a function of cell proliferation, confluence and passage number in human umbilical vein endothelial cells (HUVECs). We found that as passage number increased the percentage of cells containing VWF in WPBs was reduced significantly, whilst the protein was still detected within the secretory pathway at all times. However, the endothelial-specific marker protein, PECAM-1, is present on all cells even when WPBs are absent, indicating partial maintenance of endothelial identity. Biochemical studies show that a significant pool of immature pro-VWF can be detected in sub-confluent HUVECs; however, a larger pool of mature, processed VWF is detected in confluent cells. Newly synthesized VWF must thus be differentially sorted and packaged along the secretory pathway in semi-confluent versus confluent endothelial cells. Our studies thus show that WPB formation is linked to the formation of a confluent endothelial monolayer.

Local delivery of VEGF adenovirus to the uterine artery increases vasorelaxation and uterine blood flow in the pregnant sheep

Impaired materno-placental perfusion causes two important obstetric complications, fetal growth restriction and preeclampsia. This study investigated whether adenoviral vector-mediated overexpression of vascular endothelial growth factor (VEGF) in the uterine arteries (UtAs) increases uterine artery blood flow (UBF). First-generation adenovirus vectors (5 x 10(11) particles) containing the VEGF gene (Ad.VEGF-A or -D) or the beta-galactosidase reporter gene (Ad.lacZ) were injected into the UtAs of pregnant sheep (n=6) at 88-102 days of gestation (term=145 days). UBF was measured using Doppler sonography before, and 4-7 days after injection. Mean UBF increased significantly from 233+/-156 (s.d.) ml min(-1) to 753+/-415 ml min(-1) following Ad.VEGF-A injection (P=0.005, n=5); Ad.lacZ infection had no significant effect. Organ bath experiments on uterine arterial sections 4-7 days after injection showed that, compared with Ad.lacZ vessels, Ad.VEGF-A-transduced vessels had a reduced contractile response to phenylephrine (E max 148+/-10.9 vs E max 228.2+/-27.5, P<0.05) but increased relaxation with bradykinin (pD2 (-log EC50) values 9.11+/-0.01 vs 8.65+/-0.11, P<0.05). Injection of Ad.VEGF-A into the UtAs increases UBF by enhancing vasodilatation. This may provide the basis for therapy in pregnancies complicated by uteroplacental insufficiency.

Stress-induced cytokine responses and central adiposity in young women

BACKGROUND

Evidence suggests that people who are more responsive to psychological stress are at an increased risk of developing obesity. However, the biological mechanisms underlying this phenomenon are poorly understood. The cytokines leptin, interleukin-1 receptor antagonist (IL-1Ra) and interleukin-6 (IL-6) play a key role in fat metabolism and abnormal circulating levels of these proteins have been reported in obese people and in individuals subject to stress.

OBJECTIVE

This study investigated whether cytokine responses to acute mental stress are associated with adiposity in healthy young women.

DESIGN AND SUBJECTS

A laboratory study of 67 women, aged 18-25 years, recruited from University College London.

MEASUREMENTS

Height, weight and waist circumference were measured and body fat mass was estimated by bioelectrical impedance body composition analysis. Laboratory mental stress testing was carried out and blood pressure and heart rate were recorded at baseline, during two moderately challenging tasks (Stroop and speech) and during recovery 40-45 min post-stress. Blood samples taken at baseline, immediately post-stress and 45 min post-stress, were used for assessment of circulating cytokines. Saliva samples taken throughout the session were assessed for cortisol.

RESULTS

Women who had larger cytokine responses to stress were more abdominally obese than women with smaller cytokine stress responses. Specifically, there was a positive correlation between waist circumference and stress-induced increases in plasma levels of leptin (r=0.35, P<0.05) and IL-1Ra responses (r=0.29, P<0.05). There was also a significant positive correlation between prolonged diastolic blood pressure responses to stress and measures of total and abdominal obesity (r=0.28-0.33, P<0.05).

CONCLUSION

Increased cytokine production could be a mechanism linking stress and abdominal obesity.

The zinc-finger transcription factor, early growth response 3, mediates VEGF-induced angiogenesis

Early growth response 3 (Egr3) is a member of a zinc-finger transcription factor subfamily, which we previously found to be strongly upregulated by vascular endothelial growth factor (VEGF)-A in an oligonucleotide microarray screen of endothelial cells. Here, we show that Egr3 is the predominant Egr family member upregulated by VEGF in endothelial cells at 45 min, and that VEGF induced a rapid increase in Egr-dependent transcriptional activation mediated via its major signalling receptor, VEGFR2/KDR, and the protein kinase C (PKC) pathway. VEGF-induced Egr3 gene expression was also mediated in part via a PKC-dependent activation of protein kinase D. Inhibition of Egr3 gene expression by RNA interference was effective in inhibiting basal and VEGF-induced Egr3 gene expression, and it also inhibited VEGF-mediated endothelial cell proliferation, migration and tubulogenesis. These findings indicate that Egr3 has an essential downstream role in VEGF-mediated endothelial functions leading to angiogenesis and may have particular relevance for adult angiogenic processes involved in vascular repair and neovascular disease.

Vascular endothelial growth factor synergistically enhances induction of E-selectin by tumor necrosis factor-alpha

OBJECTIVE

The regulation of endothelial cell adhesion molecules (CAMs) by vascular endothelial growth factor (VEGF) was investigated in cell cultures and in a rabbit model of atherogenic neointima formation.

METHODS AND RESULTS

VEGF regulation of vascular CAM-1 (vascular cell adhesion molecule), intercellular CAM-1 (intercellular adhesion molecule), and E-selectin were investigated in human umbilical vein endothelial cells using quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and flow cytometry, and in the rabbit collar model of atherogenic macrophage accumulation by immunostaining. VEGF alone caused no significant induction of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, or E-selectin compared with tumor necrosis factor-alpha. In both hypercholesterolemic and normal rabbits, adenoviral VEGF-A165 expression caused no increase in endothelial vascular cell adhesion molecule-1 or E-selectin. In contrast, pretreatment of human umbilical vein endothelial cells with VEGF significantly increased E-selectin expression induced by tumor necrosis factor-alpha, compared with tumor necrosis factor-alpha alone, whereas vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 were unaffected. VEGF similarly enhanced IL-1beta-induced E-selectin upregulation. VEGF also synergistically increased tumor necrosis factor-alpha-induced E-selectin mRNA and shedding of soluble E-selectin. Synergistic upregulation of E-selectin expression by VEGF was mediated via VEGF receptor-2 and calcineurin signaling.

CONCLUSIONS

VEGF alone does not activate endothelium to induce CAM expression; instead, VEGF "primes" endothelial cells, sensitizing them to cytokines leading to heightened selective pro-inflammatory responses, including upregulation of E-selectin.

Neuroprotective role of vascular endothelial growth factor: signalling mechanisms, biological function, and therapeutic potential

Vascular endothelial growth factor (VEGF or VEGF-A) and its receptors play essential roles in the formation of blood vessels during embryogenesis and in disease. Most biological effects of VEGF are mediated via two receptor tyrosine kinases, VEGFR1 and VEGFR2, but specific VEGF isoforms also bind neuropilins (NP) 1 and 2, non-tyrosine kinase receptors originally identified as receptors for semaphorins, polypeptides with essential roles in neuronal patterning. There is abundant evidence that VEGF-A has neurotrophic and neuroprotective effects on neuronal and glial cells in culture and in vivo, and can stimulate the proliferation and survival of neural stem cells. VEGFR2 and NP1 are the major VEGF receptors expressed on neuronal cells and, while the mechanisms mediating neuroprotective effects of VEGF are not fully understood, VEGF stimulates several signalling events in neuronal cell types, including activation of phospholipase C-gamma, Akt and ERK. Findings in diverse models of nerve damage and disease suggest that VEGF has therapeutic potential as a neuroprotective factor. VEGF is a key mediator of the angiogenic response to cerebral and peripheral ischaemia, and promotes nerve repair following traumatic spinal injury. Recent work has revealed a role for reduced VEGF expression in the pathogenesis of amyotrophic lateral sclerosis, a rare neurodegenerative disease caused by selective loss of motor neurons. In many instances, the neuroprotective effects of VEGF appear to result from a combination of the indirect consequences of increased angiogenesis, and the direct stimulation of neuronal function. However, more work is required to determine the specific functional role of direct neuronal effects of VEGF.

Psychological stress activates interleukin-1beta gene expression in human mononuclear cells

The pathophysiological mechanisms underlying the association between psychological stress and cardiovascular disease are unclear. Interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) are inflammatory cytokines playing a pivotal role in atherosclerosis. IL-1beta activates IL-6, and both cytokines are produced by peripheral blood mononuclear cells. One mechanism through which stress could promote atherosclerosis is by regulating mononuclear cell cytokine gene expression. We studied cardiovascular and cytokine responses in 32 healthy men participating in two 5-min mental tasks and in 10 controls. Blood pressure and heart rate, assessed using a Portapres-2, increased significantly following tasks in all participants. Plasma IL-6 levels, determined by ELISA, also increased following tasks, with maximum levels detected 2h post-stress. Quantitative RT-PCR analysis showed that mononuclear cell IL-1beta gene expression rose significantly at 30 min post-stress and remained elevated at 75 and 120 min. Increases in IL-1beta gene expression correlated positively with plasma IL-6 responses, cardiovascular responses, subjective stress ratings, and anxiety symptoms. No changes were detected in controls. Stress-induced activation of mononuclear IL-1beta is a novel mechanism potentially linking stress and heart disease. This mechanism could also play a role in other inflammatory diseases exacerbated by stress.

The vascular endothelial growth factor (VEGF) family: angiogenic factors in health and disease

Vascular endothelial growth factors (VEGFs) are a family of secreted polypeptides with a highly conserved receptor-binding cystine-knot structure similar to that of the platelet-derived growth factors. VEGF-A, the founding member of the family, is highly conserved between animals as evolutionarily distant as fish and mammals. In vertebrates, VEGFs act through a family of cognate receptor kinases in endothelial cells to stimulate blood-vessel formation. VEGF-A has important roles in mammalian vascular development and in diseases involving abnormal growth of blood vessels; other VEGFs are also involved in the development of lymphatic vessels and disease-related angiogenesis. Invertebrate homologs of VEGFs and VEGF receptors have been identified in fly, nematode and jellyfish, where they function in developmental cell migration and neurogenesis. The existence of VEGF-like molecules and their receptors in simple invertebrates without a vascular system indicates that this family of growth factors emerged at a very early stage in the evolution of multicellular organisms to mediate primordial developmental functions.

Angiogenesis-dependent and independent phases of intimal hyperplasia

BACKGROUND

Neointimal vascular smooth muscle cell (VSMC) proliferation is a primary cause of occlusive vascular disease, including atherosclerosis, restenosis after percutaneous interventions, and bypass graft stenosis. Angiogenesis is implicated in the progression of early atheromatous lesions in animal models, but its role in neointimal VSMC proliferation is undefined. Because percutaneous coronary interventions result in induction of periadventitial angiogenesis, we analyzed the role of this process in neointima formation.

METHODS AND RESULTS

Local injury to the arterial wall in 2 different animal models induced periadventitial angiogenesis and neointima formation. Application of angiogenesis stimulators vascular endothelial growth factor (VEGF-A165) or a proline/arginine-rich peptide (PR39) to the adventitia of the injured artery induced a marked increase in neointimal thickening beyond that seen with injury alone in both in vivo models. Inhibition of either VEGF (with soluble VEGF receptor 1 [sFlt1]) or fibroblast growth factor (FGF) (with a dominant=negative form of FGF receptor 1 [FGF-R1DN]), respectively, signaling reduced adventitial thickening induced by VEGF and PR39 to the level seen with mechanical arterial injury alone. However, neither inhibitor was effective in preventing neointimal thickening after mechanical injury when administered in the absence of angiogenic growth factor.

CONCLUSIONS

Our findings indicate that adventitial angiogenesis stimulates intimal thickening but does not initiate it.

VEGF signalling: integration and multi-tasking in endothelial cell biology

The central role of VEGF (vascular endothelial growth factor A) in angiogenesis is dependent upon its ability to co-ordinately regulate multiple endothelial functions. The multifunctionality of VEGF at the cellular level results from its ability to initiate a diverse, complex and integrated network of signalling pathways via its major receptor, kinase-insert-domain-containing receptor (KDR). Activation of phospholipase C-gamma, protein kinase C, Ca(2+), ERK (extracellular-signal-regulated protein kinase), Akt, Src, focal adhesion kinase and calcineurin pathways has been implicated in mediating multiple VEGF functions, including survival, proliferation, migration, vascular permeability, tubulogenesis, NO and prostanoid synthesis, and gene expression. NO and prostanoids in turn play paracrine and autocrine roles in linking post-receptor signalling to biological functions. Integration between biologically important signalling cascades occurs at several points. Akt and ERK, for example, are key junction points linking together signal transduction involved in survival and NO generation, and proliferation and prostanoid biosynthesis. Together, the multiplicity, functional versatility and integration of VEGF signalling provide a useful framework for understanding the mechanisms underlying the endothelial biological response to this key factor.

Vascular endothelial growth factor (VEGF)-D and VEGF-A differentially regulate KDR-mediated signaling and biological function in vascular endothelial cells

Vascular endothelial growth factor (VEGF)-D binds to VEGF receptors (VEGFR) VEGFR2/KDR and VEGFR3/Flt4, but the signaling mechanisms mediating its biological activities in endothelial cells are poorly understood. Here we investigated the mechanism of action of VEGF-D, and we compared the signaling pathways and biological responses induced by VEGF-D and VEGF-A in endothelial cells. VEGF-D induced KDR and phospholipase C-gamma tyrosine phosphorylation more slowly and less effectively than VEGF-A at early times but had a more sustained effect and was as effective as VEGF-A after 60 min. VEGF-D activated extracellular signal-regulated protein kinases 1 and 2 with similar efficacy but slower kinetics compared with VEGF-A, and this effect was blocked by inhibitors of protein kinase C and mitogen-activated protein kinase kinase. In contrast to VEGF-A, VEGF-D weakly stimulated prostacyclin production and gene expression, had little effect on cell proliferation, and stimulated a smaller and more transient increase in intracellular [Ca(2+)]. VEGF-D induced strong but more transient phosphatidylinositol 3-kinase (PI3K)-mediated Akt activation and increased PI3K-dependent endothelial nitric-oxide synthase phosphorylation and cell survival more weakly. VEGF-D stimulated chemotaxis via a PI3K/Akt- and endothelial nitric-oxide synthase-dependent pathway, enhanced protein kinase C- and PI3K-dependent endothelial tubulogenesis, and stimulated angiogenesis in a mouse sponge implant model less effectively than VEGF-A. VEGF-D-induced signaling and biological effects were blocked by the KDR inhibitor SU5614. The finding that differential KDR activation by VEGF-A and VEGF-D has distinct consequences for endothelial signaling and function has important implications for understanding how multiple ligands for the same VEGF receptors can generate ligand-specific biological responses.

Vascular Endothelial Growth Factor Gene Transfer Inhibits Neointimal Macrophage Accumulation in Hypercholesterolemic Rabbits

OBJECTIVE

This study aims to determine the effects of periadventitial vascular endothelial growth factor (VEGF) gene transfer on neointima formation and macrophage accumulation induced by collar placement around the carotid artery in hypercholesterolemic rabbits.

METHODS AND RESULTS

Collar placement around the carotid artery in cholesterol-fed rabbits induced intimal thickening with increased neointimal macrophage content. Liposome-mediated VEGF gene transfer, confirmed by transgene-specific RT-PCR, caused a marked inhibition of both intimal thickening and macrophage accumulation compared with a lacZ control gene. VEGF gene transfer was not accompanied by a significant increase in adventitial neovascularization. Collaring of carotid arteries in hypercholesterolemic rabbits also upregulated endothelial VCAM-1 expression. Inhibition of neointimal macrophage infiltration in VEGF-transduced, collared arteries was associated with decreased endothelial VCAM-1.

CONCLUSIONS

VEGF gene transfer inhibits collar-induced intimal thickening, macrophage accumulation, and VCAM-1 expression in cholesterol-fed rabbits. These findings support the concept that low-level VEGF expression can exert arterioprotective effects in the presence of high blood cholesterol.

Anti-chemorepulsive effects of vascular endothelial growth factor and placental growth factor-2 in dorsal root ganglion neurons are mediated via neuropilin-1 and cyclooxygenase-derived prostanoid production

Vascular endothelial growth factor (VEGF) displays neurotrophic and neuroprotective activities, but the mechanisms underlying these effects have not been defined. Neuropilin-1 (NP-1) is a receptor for VEGF165 and placental growth factor-2 (PlGF-2), but the role of NP-1 in VEGF-dependent neurotrophic actions is unclear. Dorsal root ganglion (DRG) neurons expressed high levels of NP-1 mRNA and protein, much lower levels of KDR, and no detectable Flt-1. VEGF165 and PlGF-2 promoted DRG growth cone formation with an effect similar to that of nerve growth factor, whereas the Flt-1-specific ligand, PlGF-1, and the KDR/Flt-4 ligand, VEGF-D, had no effect. The chemorepellent NP-1 ligand, semaphorin 3A, antagonized the response to VEGF and PlGF-2. The specific KDR inhibitor, SU5614, did not affect the anti-chemorepellent effects of VEGF and PlGF-2, whereas a novel, specific antagonist of VEGF binding to NP-1, called EG3287, prevented inhibition of growth cone collapse. VEGF stimulated prostacyclin and prostaglandin E2 production in DRG cultures that was blocked by inhibitors of cyclooxygenases; the anti-chemorepellent activities of VEGF and PlGF-2 were abrogated by cyclooxygenase inhibitors, and a variety of prostacyclin analogues and prostaglandins strikingly inhibited growth cone collapse. These findings support a specific role for NP-1 in mediating neurotrophic actions of VEGF family members and also identify a novel role for prostanoids in the inhibition of neuronal chemorepulsion.

Placental growth factor induces FosB and c-Fos gene expression via Flt-1 receptors

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family that binds specifically to Flt-1. The biological roles of PlGF and Flt-1 have not yet been defined and the signalling mechanisms mediating cellular actions of PlGF remain poorly understood. In human umbilical vein endothelial cells, VEGF and PlGF induced expression of both full-length FosB mRNA and an alternatively spliced variant, DeltaFosB, with similar efficacy and kinetics. In contrast, PlGF induced c-Fos expression less strongly than VEGF, and whereas VEGF strongly upregulated tissue factor mRNA, PlGF had a negligible effect. PlGF induced c-Fos expression in porcine aortic endothelial cells specifically expressing Flt-1, and FosB expression in the monocytic RAW 264.7 cell line expressing endogenous Flt-1. These findings show for the first time that VEGF and PlGF induce mRNA expression of the transcription factors FosB and c-Fos, and suggest that these factors may play a role in the biological responses mediated by PlGF and Flt-1.

Vascular endothelial growth factor-regulated gene expression in endothelial cells: KDR-mediated induction of Egr3 and the related nuclear receptors Nur77, Nurr1, and Nor1

OBJECTIVE

The program of gene expression regulated by vascular endothelial growth factor (VEGF) remains poorly understood. The aim of this study was to identify VEGF-regulated genes in human umbilical vein endothelial cells.

METHODS AND RESULTS

VEGF-regulated gene expression was analyzed by screening Affymetrix oligonucleotide arrays and quantitative, real-time, reverse transcription-polymerase chain reaction. The most strongly induced genes were the NR4A nuclear receptor family members Nur77, Nurr1, and Nor1 and the zinc-finger transcription factor Egr3. VEGF also induced rapid expression of Down syndrome candidate region 1, cyclooxygenase-2, tissue factor, stanniocalcin-1, the serine/threonine kinase Cot, and eps15 homology domain-containing protein. VEGF-induced NR4A family and Egr3 expression was blocked by a KDR inhibitor, and placental growth factor and basic fibroblast growth factor weakly increased expression of these genes. Induction of NR4A genes was mediated via intracellular Ca2+, protein kinase C- and calcineurin-dependent pathways. VEGF increased protein expression of Nurr1 and Nur77 and decreased Nur77 phosphorylation at the negative regulatory site serine 351.

CONCLUSIONS

VEGF induces expression of NR4A nuclear receptors and Egr3 via KDR and KDR-mediated signaling mechanisms. The genes identified here are novel candidates as key early mediators of VEGF-induced endothelial functions.