PEDF is an endogenous inhibitor of VEGF-R2 angiogenesis signaling in endothelial cells.

Pigment epithelium derived factor (PEDF), an endogenous inhibitor of angiogenesis, targets the growth of aberrant blood vessels in many tissues, including the eye. In this study we show that PEDF prevented early mitogenic signals of vascular endothelial growth factor (VEGF-A) in primate retinal endothelial cells, blocking proliferation, migration and tube formation. PEDF inhibited the phosphorylation and activation of five major downstream VEGF-A signaling partners, namely phosphoinositide-3-OH Kinase (PI3K), AKT, FAK, Src (Y416), and PLC-γ. It did so by binding to the extracellular domain of VEGF-R2, blocking VEGF-A-induced tyrosine phosphorylation (Tyr 951 and Tyr 1175), and inhibiting VEGF-R2 receptor kinase activity. PEDF had no effect on the transcription or translation of VEGF-R2 in cultured HUVECs. PEDF also bound to the extracellular domain of VEGF-R1. We conclude that PEDF blocks the growth of new blood vessels, in part, by reducing VEGF-A activation of its key mitogenic receptor, VEGF-R2, and by preventing its downstream signals in endothelial cells.

Reconciling the distinct roles of angiogenic/anti-angiogenic factors in the placenta and maternal circulation of normal and pathological pregnancies.

A branched vascular network is crucial to placental development and is dependent on factors such as vascular endothelial growth factor (VEGF), placental growth factor (PlGF), angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng) to regulate blood vessel growth. Imbalances in these factors can lead to aberrant placental vascular development. Throughout pregnancy, these factors are also released into the maternal circulation to aid in adapting the maternal cardiovascular system to pregnancy. Increased secretion of anti-angiogenic factors can lead to the development of an anti-angiogenic state in the mother and contribute to the development of pregnancy pathologies such as pre-eclampsia and foetal growth restriction (FGR). Thus, what are commonly referred to as 'angiogenic factors' have distinct functions in the maternal and placental circulations making this a misnomer. Indeed, technical issues in this field such as assay methodology and lack of data considering different placental cell types mean that the physiological roles of these factors in the maternal and placental circulations are frequently muddled in the literature. This review aims to (1) unpick the distinct roles of factors that influence placental vascular development and separate these from the roles of the same factors within the maternal circulation in normal pregnancy and (2) critically assess how imbalances may contribute to the distinct pathophysiological mechanisms underlying pregnancy disorders. Together, this critical assessment of the field endeavours to improve our ability to accurately use these factors as predictive/diagnostic biomarkers in the future.

Tumor angiogenesis revisited: Regulators and clinical implications.

Since Judah Folkman hypothesized in 1971 that angiogenesis is required for solid tumor growth, numerous studies have been conducted to unravel the angiogenesis process, analyze its role in primary tumor growth, metastasis and angiogenic diseases, and to develop inhibitors of proangiogenic factors. These studies have led in 2004 to the approval of the first antiangiogenic agent (bevacizumab, a humanized antibody targeting vascular endothelial growth factor) for the treatment of patients with metastatic colorectal cancer. This approval launched great expectations for the use of antiangiogenic therapy for malignant diseases. However, these expectations have not been met and, as knowledge of blood vessel formation accumulates, many of the original paradigms no longer hold. Therefore, the regulators and clinical implications of angiogenesis need to be revisited. In this review, we discuss recently identified angiogenesis mediators and pathways, new concepts that have emerged over the past 10 years, tumor resistance and toxicity associated with the use of currently available antiangiogenic treatment and potentially new targets and/or approaches for malignant and nonmalignant neovascular diseases.

Negative regulators of angiogenesis: important targets for treatment of exudative AMD.

Angiogenesis contributes to the pathogenesis of many diseases including exudative age-related macular degeneration (AMD). It is normally kept in check by a tightly balanced production of pro- and anti-angiogenic factors. The up-regulation of the pro-angiogenic factor, vascular endothelial growth factor (VEGF), is intimately linked to the pathogenesis of exudative AMD, and its antagonism has been effectively targeted for treatment. However, very little is known about potential changes in expression of anti-angiogenic factors and the role they play in choroidal vascular homeostasis and neovascularization associated with AMD. Here, we will discuss the important role of thrombospondins and pigment epithelium-derived factor, two major endogenous inhibitors of angiogenesis, in retinal and choroidal vascular homeostasis and their potential alterations during AMD and choroidal neovascularization (CNV). We will review the cell autonomous function of these proteins in retinal and choroidal vascular cells. We will also discuss the potential targeting of these molecules and use of their mimetic peptides for therapeutic development for exudative AMD.

Inhibition of cyclooxygenase-1 and -2 activity in keratinocytes inhibits PGE2 formation and impairs vascular endothelial growth factor release and neovascularisation in skin wounds.

Inhibition of cyclooxygenase (Cox) enzymatic activity by non-steroidal anti-inflammatory drugs (NSAIDs) provides the molecular basis of analgesia following wounding or surgery. This study investigated the role of Cox activity in the regulation of vascular endothelial growth factor (VEGF) expression in keratinocytes and the formation of new blood vessels in acute wounds in mice. To this end, human HaCaT keratinocytes were stimulated with epidermal growth factor (EGF). EGF increased Cox-1 mRNA in the presence of the constitutively expressed Cox-1 protein in keratinocytes. EGF coinduced Cox-2 and VEGF165 mRNA and protein expression and an accumulation of prostaglandin E2 (PGE2 ) in cell culture supernatants. Inhibition of Cox isozyme activity by Cox-1 and -2 siRNA or ibuprofen reduced PGE2 and VEGF165 release from keratinocytes. In a mouse model of excisional wound healing, Cox-2 and VEGF165 expression were colocalized in the granulation tissue of acute wounds. Oral treatment of mice with the Cox-1 and -2 inhibitor diclofenac was associated with reduced levels of VEGF165 protein and an impaired blood vessel formation in acute wound tissue. In summary, our data suggest that a reduction of PGE2 -triggered VEGF165 protein expression in wound keratinocytes is likely to contribute to the observed impairment of wound neovascularisation upon Cox inhibition.

Pigment epithelium-derived factor (PEDF): a novel trophoblast-derived factor limiting feto-placental angiogenesis in late pregnancy.

The rapidly expanding feto-placental vasculature needs tight control by paracrine and endocrine mechanisms. Here, we focused on paracrine influence by trophoblast, the placental epithelium. We aimed to identify differences in regulation of feto-placental angiogenesis in early versus late pregnancy. To this end, the effect of conditioned media (CM) from early and late pregnancy human trophoblast was tested on network formation, migration and proliferation of human feto-placental endothelial cells. Only CM of late pregnancy trophoblast reduced network formation and migration. Screening of trophoblast transcriptome for anti-angiogenic candidates identified pigment epithelium-derived factor (PEDF) with higher expression and protein secretion in late pregnancy trophoblast. Addition of a PEDF-neutralizing antibody restored the anti-angiogenic effect of CM from late pregnancy trophoblast. Notably, human recombinant PEDF reduced network formation only in combination with VEGF. Also in the CAM assay, the combination of PEDF with VEGF reduced branching of vessels below control levels. Analysis of phosphorylation of ERK1/2 and FAK, two key players in VEGF-induced proliferation and migration, revealed that PEDF altered VEGF signaling, while PEDF alone did not affect phosphorylation of ERK1/2 and FAK. These data suggest that the trophoblast-derived anti-angiogenic molecule PEDF is involved in restricting growth and expansion of the feto-placental endothelium predominantly in late pregnancy and targets to modulate the intracellular effect of VEGF.

Antiangiogenic actions of vascular endothelial growth factor-A165b, an inhibitory isoform of vascular endothelial growth factor-A, in human obesity.

BACKGROUND: Experimental studies suggest that visceral adiposity and adipose tissue dysfunction play a central role in obesity-related cardiometabolic complications. Impaired angiogenesis in fat has been implicated in the development of adipose tissue hypoxia, capillary rarefaction, inflammation, and metabolic dysregulation, but pathophysiological mechanisms remain unknown. In this study, we examined the role of a novel antiangiogenic isoform of vascular endothelial growth factor-A (VEGF-A), VEGF-A165b, in human obesity. METHODS AND RESULTS: We biopsied paired subcutaneous and visceral adipose tissue in 40 obese subjects (body mass index, 45±8 kg/m(2); age, 45±11 years) during bariatric surgery and characterized depot-specific adipose tissue angiogenic capacity using an established ex vivo assay. Visceral adipose tissue exhibited significantly blunted angiogenic growth compared with subcutaneous fat (P<0.001) that was associated with marked tissue upregulation of VEGF-A165b (P=0.004). The extent of VEGF-A165b expression correlated negatively with angiogenic growth (r=-0.6, P=0.006). Although recombinant VEGF-A165b significantly impaired angiogenesis, targeted inhibition of VEGF-A165b with neutralizing antibody stimulated fat pad neovascularization and restored VEGF receptor activation. Blood levels of VEGF-A165b were significantly higher in obese subjects compared with lean control subjects (P=0.02), and surgical weight loss induced a marked decline in serumVEGF-A165b (P=0.003). CONCLUSIONS: We demonstrate that impaired adipose tissue angiogenesis is associated with overexpression of a novel antiangiogenic factor, VEGF-A165b, that may play a pathogenic role in human adiposopathy. Moreover, systemic upregulation of VEGF-A165b in circulating blood may have wider-ranging implications beyond the adipose milieu. VEGF-A165b may represent a novel area of investigation to gain further understanding of mechanisms that modulate the cardiometabolic consequences of obesity.

Short communication: asymmetric dimethylarginine impairs angiogenic progenitor cell function in patients with coronary artery disease through a microRNA-21-dependent mechanism.

RATIONALE: The endogenous nitric oxide synthase inhibitor asymmetrical dimethylarginine (ADMA) is increased in patients with coronary artery disease and may regulate function of circulating angiogenic progenitor cells (APCs) by small regulatory RNAs. OBJECTIVES: To study the role of microRNAs in ADMA-mediated impairment of APCs. METHODS AND RESULTS: By using microarray analyses, we established microRNA expression profiles of human APCs. We used ADMA to induce APC dysfunction and found 16 deregulated microRNAs. We focused on miR-21, which was 3-fold upregulated by ADMA treatment. Overexpression of miR-21 in human APCs impaired migratory capacity. To identify regulated miR-21 targets, we used proteome analysis, using difference in-gel electrophoresis followed by mass spectrometric analysis of regulated proteins. We found that transfection of miR-21 precursors significantly repressed superoxide dismutase 2 in APCs, which resulted in increased intracellular reactive oxygen species concentration and impaired nitric oxide bioavailability. MiR-21 further repressed sprouty-2, leading to Erk Map kinase-dependent reactive oxygen species formation and APC migratory defects. Small interference RNA-mediated superoxide dismutase 2 or sprouty-2 reduction also increased reactive oxygen species formation and impaired APC migratory capacity. ADMA-mediated reactive oxygen species formation and APC dysfunction was rescued by miR-21 blockade. APCs from patients with coronary artery disease and high ADMA plasma levels displayed >4-fold elevated miR-21 levels, low superoxide dismutase 2 expression, and impaired migratory capacity, which could be normalized by miR-21 antagonism. CONCLUSIONS: We identified a novel miR-21-dependent mechanism of ADMA-mediated APC dysfunction. MiR-21 antagonism therefore emerges as an interesting strategy to improve dysfunctional APCs in patients with coronary artery disease.

Short communication: PPAR gamma mediates a direct antiangiogenic effect of omega 3-PUFAs in proliferative retinopathy.

RATIONALE: Omega3 long-chain polyunsaturated fatty acids (omega3-PUFAs) are powerful modulators of angiogenesis. However, little is known about the mechanisms governing omega3-PUFA-dependent attenuation of angiogenesis. OBJECTIVE: This study aims to identify a major mechanism by which omega3-PUFAs attenuate retinal neovascularization. METHODS AND RESULTS: Administering omega3-PUFAs exclusively during the neovascular stage of the mouse model of oxygen-induced retinopathy induces a direct neovascularization reduction of more than 40% without altering vasoobliteration or the regrowth of normal vessels. Cotreatment with an inhibitor of peroxisome proliferator-activated receptor (PPAR)gamma almost completely abrogates this effect. Inhibition of PPARgamma also reverses the omega3-PUFA-induced reduction of retinal tumor necrosis factor-alpha, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, endothelial selectin, and angiopoietin 2 but not vascular endothelial growth factor. CONCLUSIONS: These results identify a direct, PPARgamma-mediated effect of omega3-PUFAs on retinal neovascularization formation and retinal angiogenic activation that is independent of vascular endothelial growth factor.

U94 of human herpesvirus 6 inhibits in vitro angiogenesis and lymphangiogenesis.

Human herpesvirus 6 (HHV-6) is a lymphotropic virus, but recent observations showed that also vascular endothelial cells (ECs) are susceptible to infection, both in vivo and in vitro. The observation that lymph nodes are a site of viral persistence suggests that lymphatic ECs (LECs) might be even more relevant for HHV-6 biology than vascular ECs. Here, we provide evidence that HHV-6 can infect LECs in vitro and establish a latent infection. Thus HHV-6 infection induces the loss of angiogenic properties both in LECs and in vascular ECs, as shown by the inability to form capillary-like structures and to seal wound scratches. The antiangiogenic effects observed in infected cells are associated to the expression of HHV-6 U94/rep, a latency-associated gene. In fact, transfection of U94/rep or addition of recombinant U94/REP protein to ECs inhibits the formation of in vitro capillary-like structures, reduces migration of ECs, and blocks angiogenesis, rendering rat aortic rings insensitive to VEGF-induced vasculogenetic activity. The ability of U94/rep to block different angiogenetic steps may lead to approaches in the potential control of the proliferation of blood and lymphatic vessels.

Importance of anti-angiogenic factors in the regulation of skeletal muscle angiogenesis.

The microcirculation is essential for delivery of oxygen and nutrients to maintain skeletal muscle health and function. The network of microvessels surrounding skeletal myocytes has a remarkable plasticity that ensures a good match between muscle perfusion capacities and myofiber metabolic needs. Depending on physiologic conditions, this vascular plasticity can either involve growth (e.g., exercise-induced angiogenesis) or regression (e.g., physical deconditioning) of capillaries. This angio-adaptative response is thought to be controlled by a balance between pro- and anti-angiogenic factors and their receptors. While changes in the expression or activity for pro-angiogenic factors have been well studied in response to acute and chronic exercise during the past two decades, little attention thus far has been devoted to endogenous negative regulators that are also likely to be important in regulating capillary growth/regression. Indeed, the importance and contribution of anti-angiogenic factors in controlling skeletal muscle angiogenesis remains poorly understood. Here, we highlight the emerging research related to skeletal muscle expression of several negative angiogenic factors and discuss their potential importance in controlling skeletal muscle angio-adaptation, particularly in physiologic response to physical activity.

HDAC5 is a repressor of angiogenesis and determines the angiogenic gene expression pattern of endothelial cells.

Class IIa histone deacetylases (HDACs) are signal-responsive regulators of gene expression involved in vascular homeostasis. To investigate the differential role of class IIa HDACs for the regulation of angiogenesis, we used siRNA to specifically suppress the individual HDAC isoenzymes. Silencing of HDAC5 exhibited a unique pro-angiogenic effect evidenced by increased endothelial cell migration, sprouting, and tube formation. Consistently, overexpression of HDAC5 decreased sprout formation, indicating that HDAC5 is a negative regulator of angiogenesis. The antiangiogenic activity of HDAC5 was independent of myocyte enhancer factor-2 binding and its deacetylase activity but required a nuclear localization indicating that HDAC5 might affect the transcriptional regulation of gene expression. To identify putative HDAC5 targets, we performed microarray expression analysis. Silencing of HDAC5 increased the expression of fibroblast growth factor 2 (FGF2) and angiogenic guidance factors, including Slit2. Antagonization of FGF2 or Slit2 reduced sprout induction in response to HDAC5 siRNA. Chromatin immunoprecipitation assays demonstrate that HDAC5 binds to the promoter of FGF2 and Slit2. In summary, HDAC5 represses angiogenic genes, such as FGF2 and Slit2, which causally contribute to capillary-like sprouting of endothelial cells. The derepression of angiogenic genes by HDAC5 inactivation may provide a useful therapeutic target for induction of angiogenesis.

MicroRNAs 15a and 16 regulate tumor proliferation in multiple myeloma.

Detailed genomic studies have shown that cytogenetic abnormalities contribute to multiple myeloma (MM) pathogenesis and disease progression. Nevertheless, little is known about the characteristics of MM at the epigenetic level and specifically how microRNAs regulate MM progression in the context of the bone marrow milieu. Therefore, we performed microRNA expression profiling of bone marrow derived CD138(+) MM cells versus their normal cellular counterparts and validated data by qRT-PCR. We identified a MM-specific microRNA signature characterized by down-expression of microRNA-15a/-16 and overexpression of microRNA-222/-221/-382/-181a/-181b (P < .01). We investigated the functional role of microRNA-15a and -16 and showed that they regulate proliferation and growth of MM cells in vitro and in vivo by inhibiting AKT serine/threonine-protein-kinase (AKT3), ribosomal-protein-S6, MAP-kinases, and NF-kappaB-activator MAP3KIP3. Moreover, miRNA-15a and -16 exerted their anti-MM activity even in the context of the bone marrow milieu in vitro and in vivo. These data indicate that microRNAs play a pivotal role in the biology of MM and represent important targets for novel therapies in MM.

The functions of thrombospondin-1 and-2.

Considerable progress has been made towards understanding the function of thrombospondin-1 and-2. The description of the phenotype of mice with thrombospondin-1 and-2 knocked-out supports in vitro biochemical and cell-biological data and has opened new avenues of research. Recently, our understanding of the roles of thrombospondins in the activation of TGFbeta, inhibition of angiogenesis and the initiation of signal transduction has advanced.

An antiangiogenic neurokinin-B/thromboxane A2 regulatory axis.

Establishment of angiogenic circuits that orchestrate blood vessel development and remodeling requires an exquisite balance between the activities of pro- and antiangiogenic factors. However, the logic that permits complex signal integration by vascular endothelium is poorly understood. We demonstrate that a "neuropeptide," neurokinin-B (NK-B), reversibly inhibits endothelial cell vascular network assembly and opposes angiogenesis in the chicken chorioallantoic membrane. Disruption of endogenous NK-B signaling promoted angiogenesis. Mechanistic analyses defined a multicomponent pathway in which NK-B signaling converges upon cellular processes essential for angiogenesis. NK-B-mediated ablation of Ca2+ oscillations and elevation of 3'-5' [corrected] cyclic adenosine monophosphate (cAMP) reduced cellular proliferation, migration, and vascular endothelial growth factor receptor expression and induced the antiangiogenic protein calreticulin. Whereas NK-B initiated certain responses, other activities required additional stimuli that increase cAMP. Although NK-B is a neurotransmitter/ neuromodulator and NK-B overexpression characterizes the pregnancy-associated disorder preeclampsia, NK-B had not been linked to vascular remodeling. These results establish a conserved mechanism in which NK-B instigates multiple activities that collectively oppose vascular remodeling.

Coregulation of vascular tube stabilization by endothelial cell TIMP-2 and pericyte TIMP-3.

The endothelial cell (EC)-derived tissue inhibitor of metalloproteinase-2 (TIMP-2) and pericyte-derived TIMP-3 are shown to coregulate human capillary tube stabilization following EC-pericyte interactions through a combined ability to block EC tube morphogenesis and regression in three-dimensional collagen matrices. EC-pericyte interactions strongly induce TIMP-3 expression by pericytes, whereas ECs produce TIMP-2 in EC-pericyte cocultures. Using small interfering RNA technology, the suppression of EC TIMP-2 and pericyte TIMP-3 expression leads to capillary tube regression in these cocultures in a matrix metalloproteinase-1 (MMP-1)-, MMP-10-, and ADAM-15 (a disintegrin and metalloproteinase-15)-dependent manner. Furthermore, we show that EC tube morphogenesis (lumen formation and invasion) is primarily controlled by the TIMP-2 and -3 target membrane type (MT) 1 MMP. Additional targets of these inhibitors include MT2-MMP and ADAM-15, which also regulate EC invasion. Mutagenesis experiments reveal that TIMP-3 requires its proteinase inhibitory function to induce tube stabilization. Overall, these data reveal a novel role for both TIMP-2 and -3 in the pericyte-induced stabilization of newly formed vascular networks that are predisposed to undergo regression and reveal specific molecular targets of the inhibitors regulating these events.

The antiangiogenic activity of rPAI-1(23) inhibits vasa vasorum and growth of atherosclerotic plaque.

Plaque vascularity has been implicated in its growth and stability. However, there is a paucity of information regarding the origin of plaque vasculature and the role of vasa vasorum in plaque growth. To inhibit growth of vasa vasorum in atherogenic mice and assess its effect on plaque growth, we used a truncated plasminogen activator inhibitor (PAI)-1 protein, rPAI-1(23), that has significant antiangiogenic activity. Female LDLR(-/-)ApoB-48-deficient mice fed Paigen's diet without cholate for 20 weeks received rPAI-1(23) treatment (n=21) for the last 6 weeks. Plaque size and vasa vasorum density were compared to 2 controls: mice fed Paigen's diet and treated with saline for the last 6 weeks (n=16) and mice fed Paigen's diet until the onset of treatment (n=14). The rPAI-1(23) treatment significantly reduced plaque area and plaque cholesterol in the descending aorta and plaque area in the innominate artery. Measurements of reconstructed confocal microscopy images of vasa vasorum demonstrate that rPAI-1(23) treatment decreased vasa vasorum area and length, which was supported by microCT images. Confocal images provide evidence for vascularized plaque in the saline-treated group but not in rPAI-1(23)-treated mice. The increased vessel density in saline-treated mice is attributable, in part, to upregulated fibroblast growth factor-2 expression, which is inhibited by rPAI-1(23). In conclusion, rPAI-1(23) inhibits growth of vasa vasorum, as well as vessels within the adjacent plaque and vessel wall, through inhibition of fibroblast growth factor-2, leading to reduced plaque growth in atherogenic female LDLR(-/-)ApoB-48-deficient mice.

Balance of pro- versus anti-angiogenic splice isoforms of vascular endothelial growth factor as a regulator of neuroblastoma growth.

Neuroblastoma (NB) is the second most common extracranial tumour of childhood. Angiogenesis plays a crucial role in the growth and development of NB and vascular endothelial growth factor (VEGF), one of the most potent stimuli of angiogenesis, has been studied extensively in vitro. VEGF(165) has been shown to be the predominant angiogenic isoform expressed in NB cell lines and tumours. In this study, we investigated the anti-angiogenic isoform of VEGF-A, generated from distal splice site selection in the terminal exon of VEGF (VEGF(165)b) and shown to be down-regulated in epithelial malignancies. The expression of both the pro- (VEGF(xxx)) and the anti-angiogenic (VEGF(xxx)b) isoforms was compared in a range of NB and ganglioneuroma (GN) tumours. Whereas VEGF(xxx)b and VEGF(xxx) were both expressed in GN, specific up-regulation of the VEGF(xxx) isoforms was seen in NB at RNA and protein levels. Highly tumourigenic NB cell lines also showed up-regulation of the angiogenic isoforms relative to VEGF(xxx)b compared to less tumourigenic cell lines, and the isoforms were differentially secreted. These results indicate that VEGF(165) is up-regulated in NB and that there is a difference in the balance of isoform expression from anti-angiogenic VEGF(165)b to angiogenic VEGF(165). Treatment with recombinant human VEGF(165)b significantly reduced the growth rate of established xenografts of SK-N-BE(2)-C cells (4.24 +/- 1.01 fold increase in volume) compared with those treated with saline (9.76 +/- 3.58, p < 0.01). Microvascular density (MVD) was significantly decreased in rhVEGF(165)b-treated tumours (19.4 +/- 1.9 vessels/mm(3)) in contrast to the saline-treated tumours (45.5 +/- 8.6 vessels/mm(3)). VEGF(165)b had no significant effect on the proliferative or apoptotic activity, viability or cytotoxicity of SK-N-BE(2)-C cells after 48 h. In conclusion, VEGF(165)b is an effective inhibitor of NB growth. These findings provide the rationale for further investigation of VEGF(165)b in NB and other paediatric malignancies.

Lipoxin A4: anti-inflammatory and anti-angiogenic impact on endothelial cells.

Lipoxins (LX) are a class of eicosanoid that possesses a wide spectrum of antiinflammatory and proresolution bioactions. Here we have investigated the impact of the endogenously produced eicosanoid LXA(4) on endothelial cell inflammatory, proliferative, and antigenic responses. Using HUVECs we demonstrate that LXA(4) inhibits vascular endothelial growth factor (VEGF)-stimulated inflammatory responses including IL-6, TNF-alpha, IFN-gamma and IL-8 secretion, as well as endothelial ICAM-1 expression. Interestingly, LXA(4) up-regulated IL-10 production from HUVECs. Consistent with these antiinflammatory and proresolution responses to LXA(4), we demonstrate that LXA(4) inhibited leukotriene D(4) and VEGF-stimulated proliferation and angiogenesis as determined by tube formation of HUVECs. We have explored the underlying molecular mechanisms and demonstrate that LXA(4) pretreatment is associated with the decrease of VEGF-stimulated VEGF receptor 2 (KDR/FLK-1) phosphorylation and downstream signaling events including activation of phospholipase C-gamma, ERK1/2, and Akt.

Expression of soluble vascular endothelial growth factor receptor-1 in human monocyte-derived mature dendritic cells contributes to their antiangiogenic property.

The soluble form of vascular endothelial growth factor receptor-1 (sVEGFR-1) is produced from endothelial cells by alternative splicing of VEGFR-1 mRNA, and can inhibit angiogenesis by blocking the biological effects of VEGF. In this study, we show the expression of a large amount of sVEGFR-1 in human monocyte-derived mature dendritic cells (mDCs). As compared with monocytes and immature DCs, mDCs generated by TNF-alpha or soluble CD40L with IFN-gamma, but not LPS or other stimuli, preferentially produce sVEGFR-1. We also detected the mRNA of sVEGFR-1 generated by alternative splicing of VEGFR-1 mRNA in mDCs induced by TNF-alpha. The production of sVEGFR-1 showed a distinct contrast to those of VEGF in each DC matured with various stimuli. The supernatant of DCs matured with TNF-alpha or soluble CD40L with IFN-gamma showed inhibition of the tube formation of HUVECs, which was neutralized by anti-VEGFR-1 Ab, indicating that sVEGFR-1 secreted from mDCs was biologically active. Interestingly, the supernatant of mDCs generated with LPS increased HUVEC capillary-like formation in vitro. The ratio of sVEGFR-1 to VEGF clearly reflected the net angiogenic property of mDCs. Administration of mDCs induced by TNF-alpha into the s.c. tumor of PC-14 cells implanted in SCID mice demonstrated the inhibition of tumor growth via reduction of the number of CD31-positive vessels, indicating their in vivo antiangiogenic potential. These results suggest that sVEGFR-1 produced by mDCs contribute to their antiangiogenic property, and the ratio of sVEGFR-1 to VEGF might be a useful tool for evaluating their ability to regulate angiogenesis mediated by VEGF.