Regulation of Vascular Endothelial Growth Factor Receptor-2 (Flk-1) Expression in Vascular Endothelial Cells

We have previously reported the existence of a synergistic interaction between vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in the induction of angiogenesisin vitro.Here we demonstrate that bFGF increases VEGF receptor-2 (VEGFR-2/Flk-1) expression: mRNA levels were increased by 4.5- to 8.0-fold and total protein by 2.0- to 3.5-fold, in bovine microvascular endothelial (BME), aortic endothelial (BAE), and transformed fetal aortic (GM7373) endothelial cells. VEGF itself did not affect VEGFR-2 expression, and neither bFGF nor VEGF altered expression of FGF receptor-1. We also show that synergism occurs at the level of proliferation when this is measured in a three-dimensional but not in a conventional two-dimensional assay. Differences in the level of VEGFR-2 expression were also observed when cells were grown on or within collagen gels under different conditions: mRNA levels were lowest under sparse conditions, increased 20- to 26-fold at confluence, and increased even further (57-fold) when cells were cultured in suspension in three-dimensional collagen gels. Finally, a synergistic increase was seen in the level of expression of urokinase and urokinase receptor mRNAs when cells were exposed to bFGF and VEGF for 4 days. These findings demonstrate that the level of VEGFR-2 expression can be modulated by environmental factors including cytokines and the geometry of the culture conditions and provide some insight into the mechanisms of synergism between bFGF and VEGF in the induction of angiogenesisin vitro.     

Transcription Factor HEY1 Improves Brain Vascular Endothelial Cell Function and Alleviates Ischemic Stroke by Upregulating NOTCH3

To investigate the function of hairy/enhancer-of-split related with YRPW motif protein 1 (HEY1) and Notch receptor 3 (NOTCH3) in ischemic stroke. Stroke models were established by middle cerebral artery occlusion (MCAO) and oxygen glucose deprivation (OGD) in rats and rat brain microvascular endothelial cells (BMVECs), respectively. Neurological deficit evaluation and 2,3,5-triphenyltetrazolium chloride staining were used to assess cerebral injury. The expression of HEY1 and NOTCH3 was manipulated using gain and loss of function approaches. Terminal deoxynucleotidyl transferase dUTP nick end labeling and Western blotting analysis of cleaved caspase-3 and B-cell lymphoma-2 (Bcl2) were used to evaluate apoptosis. Enzyme-linked immunosorbent assay was performed to measure the expression levels of interleukin (IL)-1β, IL-6 and IL-18. The proliferation and migration of BMVECs were analyzed by Ki-67 immunofluorescence and scratch assay, respectively. Tube formation assay was conducted to measure the length of capillary-like tubes formed by BMVECs. Co-immunoprecipitation was used to testify the relationship between HEY1 and NOTCH3. HEY1 and NOTCH3 were upregulated in MCAO and OGD models. HEY1 ameliorated ischemic injuries in MCAO rats. Knockdown of HEY1 or NOTCH3 promoted OGD-induced apoptosis and inflammation and inhibited proliferation and migration in BMVECs. NOTCH3 was a binding protein of HEY1. Overexpression of HEY1 offset the disease-promoting effect of NOTCH3 silencing. HEY1 suppresses apoptosis and inflammation and promotes proliferation and migration in BMVECs by upregulating NOTCH3, thereby ameliorating ischemic stroke.

     

Induction of Vascular Endothelial Growth Factor and Matrix Metalloproteinase-9 via CD47 Signaling in Neurovascular Cells

Neurovascular injury comprises a wide spectrum of pathophysiology that underlies the progression of brain injury after cerebral ischemia. Recently, it has been shown that activation of the integrin-associated protein CD47 mediates the development of blood–brain barrier injury and edema after cerebral ischemia. However, the mechanisms that mediate these complex neurovascular effects of CD47 remain to be elucidated. Here, we compare the effects of CD47 signaling in brain endothelial cells, astrocytes, and pericytes. Exposure to 4N1 K, a specific CD47-activating peptide derived from the major CD47 ligand thrombospondin-1, upregulated two major neurovascular mediators, vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9), in brain endothelial cells and astrocytes. No changes were detected in pericytes. These findings may provide a potential mechanism for CD47-induced changes in blood–brain barrier homeostasis, and further suggest that CD47 may be a relevant neurovascular target in stroke.     

Vascular Endothelial Growth Factor Receptor-2 Activates ADP-ribosylation Factor 1 to Promote Endothelial Nitric-oxide Synthase Activation and Nitric Oxide Release from Endothelial Cells

Vascular endothelial growth factor (VEGF) induces angiogenesis and regulates endothelial function via production and release of nitric oxide (NO), an important signaling molecule. The molecular basis leading to NO production involves phosphatidylinositiol-3 kinase (PI3K), Akt, and endothelial nitric-oxide synthase (eNOS) activation. In this study, we have examined whether small GTP-binding proteins of the ADP-ribosylation factor (ARF) family act as molecular switches to regulate signaling cascades activated by VEGF in endothelial cells. Our results show that this growth factor can promote the rapid and transient activation of ARF1. In endothelial cells, this GTPase is present on dynamic plasma membrane ruffles. Inhibition of ARF1 expression, using RNA interference, markedly impaired VEGF-dependent eNOS phosphorylation and NO production by preventing the activation of the PI3K/Akt signaling axis. Furthermore, our data indicate that phosphorylation of Tyr⁸⁰¹, on VEGF receptor 2, is essential for activating Src- and ARF1-dependent signaling events leading to NO release from endothelial cells. Lastly, this mediator is known to regulate a broad variety of endothelial cell functions. Depletion of ARF1 markedly inhibits VEGF-dependent increase of vascular permeability as well as capillary tubule formation, a process important for angiogenesis. Taken together, our data indicate that ARF1 is a novel modulator of VEGF-stimulated NO release and signaling in endothelial cells.     

Vascular Endothelial Growth Factor Receptor-1 Activation Promotes Migration and Invasion of Breast Cancer Cells through Epithelial-Mesenchymal Transition

Vascular endothelial growth factor receptor-1 (VEGFR-1 or Flt-1), a tyrosine kinase receptor, is highly expressed in breast cancer tissues, but near absent in normal breast tissue. While VEGFR-1 expression is associated with poor prognosis of women with breast cancer, it is not clear whether it is involved in the aggressiveness of breast cancer. Thus, the present study examined whether VEGFR-1 activation is associated with the invasiveness of breast cancer. We reported that VEGFR-1 was detected in 60.6% of invasive breast carcinoma tissue sections. In addition, VEGFR-1 expression positively correlated with lymph node-positive tumor status, low expression level of membranous E-cadherin, and high expression levels of N-cadherin and Snail. We found that PlGF-mediated VEGFR-1 activation promoted migration and invasion in MCF-7 (luminal) cells and led to morphologic and molecular changes of epithelial-mesenchymal transition (EMT). This was blocked by the down-regulation of VEGFR-1. Conversely, down-regulation of VEGFR-1 in MDA-MB-231 (post-EMT) cells resulted in morphologic and molecular changes similar to mesenchymal-epithelial transition (MET), and exogenous PlGF could not reverse these changes. Moreover, VEGFR-1 activation led to an increase in nuclear translocation of Snail. Finally, MDA-MB-231 cells expressing shRNA against VEGFR-1 significantly decreased the tumor growth and metastasis capacity in a xenograft model. Histological examination of VEGFR-1/shRNA-expressing tumor xenografts showed up-regulation of E-cadherin and down-regulation of N-cadherin and Snail. These findings suggest that VEGFR-1 may promote breast cancer progression and metastasis, and therapies that target VEGFR-1 may be beneficial in the treatment of breast cancer patients.     

血管内皮生长因子受体信号转导通路与肿瘤血管生成

血管内皮生长因子是促进血管生成的重要调节因子.它能促进内皮细胞增殖、迁移,阻止内皮细胞凋亡、管腔网状结构退化,增加血管渗透性.所有这些作用都是通过血管内皮生长因子受体信号转导通路实现的.它们在肿瘤血管生成、肿瘤生长中起着重要的作用.以血管内皮生长因子受体信号转导通路为靶点是开发肿瘤血管生成抑制剂的理想策略.     

KRIT1 Protein Depletion Modifies Endothelial Cell Behavior via Increased Vascular Endothelial Growth Factor (VEGF) Signaling

Disruption of endothelial cell-cell contact is a key event in many cardiovascular diseases and a characteristic of pathologically activated vascular endothelium. The CCM (cerebral cavernous malformation) family of proteins (KRIT1 (Krev-interaction trapped 1), PDCD10, and CCM2) are critical regulators of endothelial cell-cell contact and vascular homeostasis. Here we show novel regulation of vascular endothelial growth factor (VEGF) signaling in KRIT1-depleted endothelial cells. Loss of KRIT1 and PDCD10, but not CCM2, increases nuclear β-catenin signaling and up-regulates VEGF-A protein expression. In KRIT1-depleted cells, increased VEGF-A levels led to increased VEGF receptor 2 (VEGFR2) activation and subsequent alteration of cytoskeletal organization, migration, and barrier function and to in vivo endothelial permeability in KRIT1-deficient animals. VEGFR2 activation also increases β-catenin phosphorylation but is only partially responsible for KRIT1 depletion-dependent disruption of cell-cell contacts. Thus, VEGF signaling contributes to modifying endothelial function in KRIT1-deficient cells and microvessel permeability in Krit1^+/− mice; however, VEGF signaling is likely not the only contributor to disrupted endothelial cell-cell contacts in the absence of KRIT1.     

In-silico screening and in-vitro validation of Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) inhibitors

VEGFR-2 tyrosine kinase receptor draws attention of the scientific fraternity in drug discovery for its important role in cancer, cardiopulmonary, cardiovascular diseases etc. Hence there is a need for novel VEGFR-2 inhibitors screening and testing for their biological activities. The 3D-structure was collected from PDB and stability was checked by using WHATIF and PROCHECK programs and subjected for virtual screening on Zinc database. We used virtual screening method to screen new VEGFR-2 blocker molecules based on their binding energies and then docked with active site on the receptor with the help of AUTODOCK software. Based on the results obtained top three molecules (VRB1-3) were selected and tested in Cardiomyocytes H9c2 cells for cell viability under hypoxic condition. The invitro studies showed VRB2 as the best molecule among the selected three molecules as well as with a standard commercial drug Sunitinib.     

血管内皮生长因子基因治疗大鼠脑缺血的实验研究

为探讨血管内皮生长因子(VEGF)基因治疗大鼠脑缺血的可行性,构建了pcD2/hVEGF121真核表达质粒,建立持续性大脑中动脉堵塞(MCAO)的局灶性脑梗塞模型,大鼠脑皮质直接注射法转移pcD2/hVEGF121真核表达质粒。应用逆转录聚合酶链反应(RT-PCR)、VEGF免疫组织化学法、脑血管计数及梗塞面积测定等方法检测转移pcD2/hVEGF121真核表达质粒后大鼠脑中VEGF基因表达及生物学效应。结果发现,与转移空载质粒的对照组相比,转移VEGF基因后7d的大鼠脑组织中有VEGFmRNA高表达,VEGF免疫组化染色可见VEGF蛋白表达水平增高,脑血管数增多,梗塞体积缩小。因此,直接注射法转移VEGF基因能够在缺血脑组织中表达,表达产物能够发挥生物学效应,进而起到保护脑组织作用。     

超声微泡介导VEGF基因转染治疗缺血性疾病研究进展

："治疗性血管新生" 是利用外源性血管生长因子或基因促进缺血部位新生血管形成,达到改善缺血部位血液供应而起到治 疗的目的,该方法为缺血性疾病的治疗提供了新的思路。目前研究的多种与血管生成相关的因子中,血管内皮生长因子（Vascular Endothelial Growth Factor,VEGF）是公认的最具特异性且作用最强的促进血管生长因子。但由于外源性血管生长因子重组蛋白在 体内半衰期短,试验中难以长时间持续给药起到刺激新血管生成及成熟的作用。研究表明通过超声破坏微泡技术可使基因转染 的靶细胞持续表达该基因。因此,应用超声靶向微泡破坏技术使VEGF 基因在缺血部位持续表达,可起到治疗性血管新生的作 用。本文将就超声微泡介导VEGF基因转染治疗缺血性疾病研究进展进行综述。     

Vascular Permeability Factor/Vascular Endothelial Growth Factor Inhibits Anchorage-Disruption-Induced Apoptosis in Microvessel Endothelial Cells by Inducing Scaffold Formation

Survival and proliferation of endothelial cells requires both growth factors and an appropriate extracellular matrix to which cells can attach. In the absence of either, endothelial cells rapidly undergo apoptosis. Thus, when human microvascular endothelial cells (HDMEC) are plated on a hydrophobic surface such as untreated polystyrene, they rapidly undergo apoptosis and die. The present study demonstrates that vascular permeability factor/vascular endothelial growth factor (VPF/VEGF), an endothelial cell-selective cytokine, inhibits apoptosis of HDMEC cultured on untreated polystyrene and induces these cells to adhere, spread, and proliferate. VPF/VEGF-induced HDMEC adhesion was time-dependent, requiredde novoprotein synthesis, and was inhibited by a soluble RGD peptide but not by an inhibitor of collagen synthesis. Under the conditions of these experiments, VPF/VEGF downregulated expression of collagen IV and fibronectin but did not change collagen I mRNA levels. VPF/VEGF-induced HDMEC adhesion was inhibited by antibodies to αvβ5 and vitronectin but not by antibodies to αvβ3. Other endothelial growth factors and cytokines such as bFGF, HGF, and TGFβ did not reproduce the VPF/VEGF effect. We suggest that VPF/VEGF induces endothelial cells to deposit a scaffolding (likely involving vitronectin) that allows them to attach to and proliferate on an otherwise nonsupportive surface (hydrophobic polystyrene) and in this manner serves as both a survival factor and a growth factor.     

血管内皮细胞生长因子及其相关蛋白的结构与功能

血管内皮细胞生长因子（ＶＥＧＦ）是在胚胎发生和创伤愈合过程中启动血管形成的一个高度特异的有丝分裂原,也是一种有效的血管通透性诱导因子,ＶＥＧＦ是胱氨酸结生长因子超家族的一员,它与其受体的结构细节和工能特征为设计分子拮抗剂提供了重要依据。其结构特征和生物学特性使之在缺血组织重组侧支循环,肿瘤预后,肿瘤转移乃至实施基因治疗等领域成为重要的研究对象。     

Neutrophil Elastase-Generated Fragment of Vascular Endothelial Growth Factor-A Stimulates Macrophage and Endothelial Progenitor Cell Migration

Elastase released from neutrophils as part of the innate immune system has been implicated in chronic diseases such as emphysema and cardiovascular disease. We have previously shown that neutrophil elastase targets vascular endothelial growth factor-A (VEGF) for partial degradation to generate a fragment of VEGF (VEGFf) that has distinct activities. Namely, VEGFf binds to VEGF receptor 1 but not to VEGF receptor 2 and shows altered signaling compared to intact VEGF. In the present study we investigated the chemotactic function of VEGF and VEGFf released from cells by neutrophil elastase. We found that endothelial cells migrated in response to intact VEGF but not VEGFf whereas RAW 264.7 macrophages/monocytes and embryonic endothelial progenitor cells were stimulated to migrate by either VEGF or VEGFf. To investigate the role of elastase-mediated release of VEGF from cells/extracellular matrices, a co-culture system was established. High or low VEGF producing cells were co-cultured with macrophages, endothelial or endothelial progenitor cells and treated with neutrophil elastase. Elastase treatment stimulated macrophage and endothelial progenitor cell migration with the response being greater with the high VEGF expressing cells. However, elastase treatment led to decreased endothelial cell migration due to VEGF cleavage to VEGF fragment. These findings suggest that the tissue response to NE-mediated injury might involve the generation of diffusible VEGF fragments that stimulate inflammatory cell recruitment.     

Induction of Fibroblast Growth Factor Receptor-1 mRNA and Protein by Platelet-Derived Growth Factor BB

Expression levels of growth factor receptors are subject to complex regulation, which is of consequence for their signaling capacity in physiological and pathological processes. We examined the regulation of expression levels of fibroblast growth factor receptor 1 (FGFR-1) in human fibroblasts treated with a panel of growth regulatory factors. Only platelet-derived growth factor BB (PDGF-BB) treatment had a significant effect and induced FGFR-1 mRNA levels fourfold, with a peak around 8 h of stimulation. The increase in mRNA levels was followed by an increased synthesis of FGFR-1 protein, which responded to basic FGF (bFGF) stimulation with induction of kinase activity and biological signaling. Thus, murine brain endothelial cells displayed an augmented induction of plasminogen activator activity in response to bFGF, following treatment with PDGF-BB. These data suggest that PDGF-BB could support FGFR-1-mediated biological responses in processes such as angiogenesis.     

Endothelial Progenitor Cells Promote Directional Three-Dimensional Endothelial Network Formation by Secreting Vascular Endothelial Growth Factor

Endothelial progenitor cell (EPC) transplantation induces the formation of new blood-vessel networks to supply nutrients and oxygen, and is feasible for the treatment of ischemia and cardiovascular diseases. However, the role of EPCs as a source of proangiogenic cytokines and consequent generators of an extracellular growth factor microenvironment in three-dimensional (3D) microvessel formation is not fully understood. We focused on the contribution of EPCs as a source of proangiogenic cytokines on 3D microvessel formation using an in vitro 3D network model. To create a 3D network model, EPCs isolated from rat bone marrow were sandwiched with double layers of collagen gel. Endothelial cells (ECs) were then cultured on top of the upper collagen gel layer. Quantitative analyses of EC network formation revealed that the length, number, and depth of the EC networks were significantly enhanced in a 3D model with ECs and EPCs compared to an EC monoculture. In addition, conditioned medium (CM) from the 3D model with ECs and EPCs promoted network formation compared to CM from an EC monoculture. We also confirmed that EPCs secreted vascular endothelial growth factor (VEGF). However, networks cultured with the CM were shallow and did not penetrate the collagen gel in great depth. Therefore, we conclude that EPCs contribute to 3D network formation at least through indirect incorporation by generating a local VEGF gradient. These results suggest that the location of EPCs is important for controlling directional 3D network formation in the field of tissue engineering.     

Circulating Endothelial Progenitor Cells and the Risk of Vascular Events after Ischemic Stroke

Background and Purpose

We evaluated the hypothesis that the number of circulating EPC could be associated with the risk of stroke recurrence (SR) or vascular events (VE) after an ischemic stroke.

Methods

We studied prospectively consecutive patients with cerebral infarction within the first 48 hours after the onset. We recorded demographic factors, vascular risk factors, previous Rankin scale (RS) score, and etiology. We analyzed EPC counts by flow cytometry in blood collected at day 7 and defined EPC as CD34+/CD133+/KDR+ cells. Mean follow-up was 29.3 ± 16 months. We evaluated SR as well as VE. Patients were classified as to the presence or absence of EPC in the circulation (either EPC+ or EPC-). Bivariate analyses, Kaplan-Meier survival curves and Cox regression models were used.

Results

We included 121 patients (mean age 70.1±12.6 years; 65% were men). The percentage of EPC+ patients was 47.1%. SR occurred in 12 (9.9%) and VE in 18 (14.9%) patients. SR was associated significantly with a worse prior RS score, previous stroke and etiology, but not with EPC count. VE were associated significantly with EPC-, worse prior RS score, previous stroke, high age, peripheral artery disease and etiology. Cox regression model showed that EPC- (HR 7.07, p=0.003), age (HR 1.08, p=0.004) and a worse prior RS score (HR 5.8, p=0.004) were associated significantly with an increased risk of VE.

Conclusions

The absence of circulating EPC is not associated with the risk of stroke recurrence, but is associated with an increased risk of future vascular events.     

Upregulation of Vascular Endothelial Growth Factor Receptor-3 in the Spinal Cord of Lewis Rats with Experimental Autoimmune Encephalomyelitis

We investigated the spatiotemporal expression of vascular endothelial growth factor receptor–3 (VEGFR-3) in the spinal cord of Lewis rats with experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. VEGFR-3 mRNA and protein were constitutively expressed in gray matter neurons and in a few white matter astrocytes. Induction of VEGFR-3 occurred predominantly in perivascular infiltrated macrophages in the spinal cord white matter during the inductive phase of EAE. VEGFR-3 expression was also induced in activated microglial cells in the gray and white matter, mainly in the peak phase. In addition, reactive astrocytes in the white matter, but not in the gray matter, expressed VEGFR-3 as disease severity increased. These data suggest that VEGFR-3 is involved in the recruitment of monocytic macrophages and in glial reactions during EAE.     

新生儿窒息与血管内皮生长因子和胰岛素样生长因子-1的关系

目的:探讨血管内皮生长因子(VEGF)及胰岛素样生长因子-1(IGF-1)在窒息新生儿脐血水平变化的临床意义.方法:采用双抗体夹心酶联免疫吸附法(ELISA)及放射免疫分析法(RIA)测定正常新生儿(67例,对照组)和窒息新生儿(50例,窒息组)脐血血管内皮生长因子(VEGF)及胰岛素样生长因子-1(IGF-1)的水平.结果:新生儿窒息时脐血VEGF比正常脐血对照组显著升高(t=-9.944,p<0.01),IGF-1比正常脐血对照组显著下降(t=-15.943,p<0.01).结论:窒息新生儿VEGF水平的上升与IGF-1水平的下降,提示两者均可能参与新生儿窒息的病理生理过程,同时检测新生儿脐血VEGF与IGF-1可望成为反映新生儿窒息程度的一个敏感和特异的指标.