Localized cysteine sulfenic acid formation by vascular endothelial growth factor: role in endothelial cell migration and angiogenesis

Reactive oxygen species (ROS) are important mediators for VEGF receptor 2 (VEGFR2) signalling involved in angiogenesis. The initial product of Cys oxidation, cysteine sulfenic acid (Cys-OH), is a key intermediate in redox signal transduction; however, its role in VEGF signalling is unknown. We have previously demonstrated IQGAP1 as a VEGFR2 binding scaffold protein involved in ROS-dependent EC migration and post-ischemic angiogenesis. Using a biotin-labelled Cys-OH trapping reagent, we show that VEGF increases protein-Cys-OH formation at the lamellipodial leading edge where it co-localizes with NADPH oxidase and IQGAP1 in migrating ECs, which is prevented by IQGAP1 siRNA or trapping of Cys-OH with dimedone. VEGF increases IQGAP1-Cys-OH formation, which is prevented by N-acetyl cysteine or dimedone, which inhibits VEGF-induced EC migration and capillary network formation. In vivo, hindlimb ischemia in mice increases Cys-OH formation in small vessels and IQGAP1 in ischemic tissues. In summary, VEGF stimulates localized formation of Cys-OH-IQGAP1 at the leading edge, thereby promoting directional EC migration, which may contribute to post-natal angiogenesis in vivo. Thus, targeting Cys-oxidized proteins at specific compartments may be the potential therapeutic strategy for various angiogenesis-dependent diseases.     

Culture of endothelial cells by transfection with plasmid harboring vascular endothelial growth factor

Vascular endothelial cells (ECs) are usually difficult to culture in a large scale because of their complicated requirements for cell growth. As the vascular endothelial growth factor (VEGF) is a key growth factor in the EC culture, we transfected human umbilical vein endothelial cells (HUVEC) using a plasmid containing VEGF gene and let them grow in a culture medium eliminated an important supplement, endothelail cell growth supplement (ECGS). The expression of VEGF by HUVEC tansfected with VEGF gene was not enough to stimulate the growth of HUVEC, only 40% of maximum cell density obtainable in the presence of ECGS., However, when the culture medium was supplied with 2.5 ng/mL of basic fibroblast growth factor (bFGF), a synergistic effect of VEGF and bFGF was observed. In this case, the final cell density was recovered up to about 78% of maxium value.     

Interleukin-6 increases vascular endothelial growth factor and angiogenesis in gastric carcinoma

Interleukin-6 (IL-6) is a proinflammatory cytokine associated with the disease status of gastric carcinoma (GC). Vascular endothelial growth factor (VEGF) is a potent tumor angiogenic factor in GC. In this study, we attempted to clarify whether IL-6 can regulate VEGF and angiogenesis in GC. GC samples from 54 surgical specimens were subjected to immunohistochemical examination of IL-6, VEGF, and tumor microvessels, and results showed that IL-6 was positively correlated with VEGF expression and tumor vasculature. We determined VEGF expression in four GC cell lines by ELISA, revealing that GC cells can produce significant amount of VEGF with increasing dose and duration of IL-6 stimulation. Next, a luciferase reporter gene assay was employed to determine the signaling pathway driving the VEGF promoter by IL-6, which showed that the JAK/STAT pathway is involved in the stimulation of VEGF gene expression. The effects of IL-6 on angiogenesis in vitro and in vivo were evaluated by HUVEC studies and the Matrigel plug assay, respectively. Results showed that IL-6 effectively promoted HUVEC proliferation and tube formation in vitro and Matrigel plug vascularization in vivo, primarily by inducing VEGF in GC. This study provides evidence that the multifunctional cytokine, IL-6, may induce VEGF expression which increases angiogenesis in gastric carcinogenesis.     

Control of vascular endothelial growth factor angiogenic activity by the extracellular matrix

In adult vessels the proliferation rate of differentiated endothelial cells is very low. In response to several environmental stimuli the expression of so-called ‘angiogenic factors’ is upregulated and the messenger RNAs are actively translated in secreted factors which induce the proliferation of endothelial cells; the digestion of their basement membrane then allows their migration and differentiation. Considerable progress has been made during the past years in elucidating the molecular actors of angiogenesis. Vascular endothelial growth factor turned out to represent the major inducer of angiogenesis. Optional splicing of its pre-messenger RNA generates various isoforms which differ not only by their storage in the extracellular matrix but also by their signaling pathways.     

质膜上的活性氧制造者--NOX家族

NADPH氧化酶特异存在于吞噬细胞质膜,能生成用于清除病原微生物的活性氧（reactive oxygen species,ROS）。NOX是NADPH氧化酶催化亚基gp91^phox的同源物,存在于多种非吞噬细胞。目前发现的NOX有NOX1、NOX3、NOX4及NOX5,虽然它们有一定的组织特异性,但与NADPH氧化酶一样均有催化生成ROS的能力。与吞噬细胞中NADPH氧化酶所制造的ROS不同,NOX所产生的ROS并不主要起细胞防御功能,而是作为第二信使,参与细胞增殖、分化、凋亡的调节。此外,NOX对血管生成及骨吸收也有一定的影响,同时还可作为氧感受器调节促红细胞生成素（EPO）的产生。     

Angiogenesis is stimulated by a tumor-derived endothelial cell growth factor

A growth factor mitogenic for BALB/C 3T3 cells and capillary endothelial cells was isolated from a rat chondrosarcoma and purified to homogeneity. Purification was accomplished by a combination of BioRex 70 cation exchange chromatography and heparin affinity chromatography. The pure chondrosarcoma-derived growth factor (ChDGF) had a molecular weight of about 18,000. The angiogenesis activity of pure ChDGF was tested by measuring its ability to vascularize the chorioallantoic membrane (CAM) and yolk sac membrane of the developing chick. The ability of ChDGF to induce the growth of limbal vessels in the rat cornea was also measured. To quantitate the angiogenesis response, a unit system based on the growth factor activity of ChDGF for 3T3 cells was adopted. ChDGF was found to have a specific activity of about 5 units/ng when applied to 3T3 cells. About 300-600 units of ChDGF in the two types of developing chick membrane and 30-5 units of ChDGF in the rat cornea were found to stimulate noninflammatory angiogenesis.     

Vascular endothelial growth factor and substrate mechanics regulate in vitro tubulogenesis of endothelial progenitor cells

Endothelial progenitor cells (EPCs) in the circulatory system have been suggested to maintain vascular homeostasis and contribute to adult vascular regeneration and repair. These processes require that EPCs break down the extracellular matrix (ECM), migrate, differentiate and undergo tube morphogenesis. Evidently, the ECM plays a critical role by providing biochemical and biophysical cues that regulate cellular behaviour. Using a chemically and mechanically tunable hydrogel to study tube morphogenesis in vitro, we show that vascular endothelial growth factor (VEGF) and substrate mechanics co‐regulate tubulogenesis of EPCs. High levels of VEGF are required to initiate tube morphogenesis and activate matrix metalloproteinases (MMPs), which enable EPC migration. Under these conditions, the elasticity of the substrate affects the progression of tube morphogenesis. With decreases in substrate stiffness, we observe decreased MMP expression while increased cellular elongation, with intracellular vacuole extension and coalescence to open lumen compartments. RNAi studies demonstrate that membrane type 1‐MMP (MT1‐MMP) is required to enable the movement of EPCs on the matrix and that EPCs sense matrix stiffness through signalling cascades leading to the activation of the RhoGTPase Cdc42. Collectively, these results suggest that coupled responses for VEGF stimulation and modulation of substrate stiffness are required to regulate tube morphogenesis of EPCs.     

OSAHS患者腭咽组织中COX-2、VEGF的表达及其与新生血管生成的关系

目的：探讨阻塞性睡眠呼吸暂停低通气综合症（OSAHS）患者腭咽组织中环氧化酶-2（COX-2）、血管内皮生长因子（VEGF）的表达及其与新生血管生成的关系及意义。方法：经多导睡眠监测仪（PSG）确诊的40例OSAHS患者（其中轻度组7例,中度12例,重度21例）及6例无鼾症患者的软腭组织,采用HE染色光镜观察腭咽部组织的病理组织学改变,免疫组化技术检测COX-2,VEGF及微血管密度（MVD）的表达情况。结果：COX-2、VEGF主要表达于OSAHS患者软腭组织的黏膜鳞状上皮和导管腺上皮,中、重度OSAHS组与对照组比较,COX-2,VEGF,MVD表达均有显著差异（P〈0.01）,OSAHS组明显高于对照组,轻度组与对照组差别无统计学意义（P〉0.05）;COX-2、VEGF均与MVD的表达呈正相关（P〈0.01）,COX-2与VEGF的表达呈正相关（P〈0.01）,COX-2,VEGF,MVD均与睡眠呼吸暂停低通气指数（AHI）呈正相关（P〈0.01）,与夜间最低氧饱和度呈负相关（P〈0.01）。结论：OSAHS患者腭咽部存在新生血管增生,与缺氧程度有关,COX-2及VEGF在其发生发展过程中可能起到重要作用。     

Vascular endothelial growth factor (VEGF) stimulates monocyte migration through endothelial monolayers via increased integrin expression

Monocytes play an important role in collateral vessel formation (arteriogenesis) by attaching to activated endothelium and by invading the walls of innate collateral vessels where they produce growth factors. Previous studies have demonstrated that this process can be promoted by several chemokines and growth factors. In this study we examined the interaction between monocytes and endothelium under stimulation of the angiogenic agent vascular endothelial growth factor (VEGF). We report here the novel finding that VEGF stimulates the expression of the alphaL-, alphaM- and beta2-integrin monomers. In functional assays and by using neutralizing antibodies it was shown that VEGF stimulates adhesion of monocytes to human umbilical vein endothelial cells (HUVEC), and increased transmigration through endothelial monolayers is dependent on interaction of monocyte beta2-integrins with its endothelial counter ligand ICAM-1. Based on these in vitro data we hypothesize that the positive effect of VEGF on arteriogenesis may involve monocyte activation.     

Stimulation of human vascular endothelial cell growth by a platelet-derived growth factor and thrombin

Repair of a vascular wound is mediated by migration and subsequent replication of the endothelial cells that form the inner lining of blood vessels. We have measured the growth response of human umbilical vein endothelial cells (HuE) to two polypeptides that are transiently produced in high concentrations at the site of a wound; the platelet-derived growth factor (PDGF) and the protease thrombin. When 10⁴ HuE cells are seeded as a dense island (2-mm diameter) in the center of a 16-mm tissue culture well in medium containing 20% human serum derived from platelet-poor plasma (PDS), no increase in cell number or colony size is observed. With the addition of 0.5 ng/ml partially purified PDGF, colony size increases and the number of cells after 8 days is 4.8 × 10⁴. When human thrombin (1 μg/ml) is added along with the PDGF, the cell number rises to 9.2 × 10⁴. Thrombin alone stimulates no increase in cell number. Although partially purified PDGF stimulates endothelial cells maintained in PDS as well as those maintained in whole blood serum (WBS), pure PDGF is active only when assayed in medium that contains WBS and is supplemented with thrombin. These results suggest the existence of a second class of platelet-derived factors that enable HuE cells to respond to the mitogenic activity of the purified platelet mitogen and thrombin.     

细胞生长因子对冠状动脉内皮细胞增殖与迁移的影响

目的 :观察肝细胞生长因子 (HGF)和血管内皮细胞生长因子 (VEGF)对体外培养牛冠状动脉内皮细胞(BCAEC)增殖、迁移的影响。方法 :分离和培养BCAEC ,设对照组、VEGF组、HGF组。采用四甲基偶氮唑蓝法(MTT)观察细胞增殖 ;倒置显微镜观察培养的血管内皮细胞的迁移。结果 :对照组、VEGF组、HGF组的OD值分别为 0 .2 2± 0 .0 1、0 .40± 0 .1 4、0 .44± 0 .1 5 ;VEGF组、HGF组BCAEC的增殖率分别为 81 .8%± 1 6 .9%、1 0 0 %±2 1 .1 % ;对照组BCAEC迁移不明显 ,而VEGF组和HGF组BCAEC迁移明显。结论 :VEGF、HGF能促进BCAEC增殖、迁移 ,HGF作用强度不亚于VEGF。     

Mammalian sprouty-1 and -2 are membrane-anchored phosphoprotein inhibitors of growth factor signaling in endothelial cells

Growth factor-induced signaling by receptor tyrosine kinases (RTKs) plays a central role in embryonic development and in pathogenesis and, hence, is tightly controlled by several regulatory proteins. Recently, Sprouty, an inhibitor of Drosophila development-associated RTK signaling, has been discovered. Subsequently, four mammalian Sprouty homologues (Spry-1-4) have been identified. Here, we report the functional characterization of two of them, Spry-1 and -2, in endothelial cells. Overexpressed Spry-1 and -2 inhibit fibroblast growth factor- and vascular endothelial growth factor-induced proliferation and differentiation by repressing pathways leading to p42/44 mitogen-activating protein (MAP) kinase activation. In contrast, although epidermal growth factor-induced proliferation of endothelial cells was also inhibited by Spry-1 and -2, activation of p42/44 MAP kinase was not affected. Biochemical and immunofluorescence analysis of endogenous and overexpressed Spry-1 and -2 reveal that both Spry-1 and -2 are anchored to membranes by palmitoylation and associate with caveolin-1 in perinuclear and vesicular structures. They are phosphorylated on serine residues and, upon growth factor stimulation, a subset is recruited to the leading edge of the plasma membrane. The data indicate that mammalian Spry-1 and -2 are membrane-anchored proteins that negatively regulate angiogenesis-associated RTK signaling, possibly in a RTK-specific fashion.     

Solution structure of a phage-derived peptide antagonist in complex with vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is a potent endothelial cell-specific mediator of angiogenesis and vasculogenesis. VEGF is involved pathologically in cancer, proliferative retinopathy and rheumatoid arthritis, and as such represents an important therapeutic target. Three classes of disulfide-constrained peptides that antagonize binding of the VEGF dimer to its receptors, KDR and Flt-1, were identified previously using phage display methods. NMR studies of a representative peptide from the most potent class of these peptide antagonists, v107 (GGNECDAIRMWEWECFERL), were undertaken to characterize its interactions with VEGF. v107 has no defined structure free in solution, but binding to VEGF induces folding of the peptide. The solution structure of the VEGF receptor-binding domain-v107 complex was determined using 3940 (1970 per VEGF monomer) internuclear distance and 476 (238 per VEGF monomer) dihedral angle restraints derived from NMR data obtained using samples containing either (13)C/(15)N-labeled protein plus excess unlabeled peptide or (13)C/(15)N-labeled peptide plus excess unlabeled protein. Residual dipolar coupling restraints supplemented the structure determination of the complex and were found to increase significantly both the global precision of VEGF in the complex and the agreement with available crystal structures of VEGF. The calculated ensemble of structures is of high precision and is in excellent agreement with the experimental restraints. v107 has a turn-helix conformation with hydrophobic residues partitioned to one face of the peptide and polar or charged residues at the other face. Contacts between two v107 peptides and the VEGF dimer are mediated by primarily hydrophobic side-chain interactions. The v107-binding site on VEGF overlaps partially with the binding site of KDR and is similar to that for domain 2 of Flt-1. The structure of the VEGF-v107 complex provides new insight into how binding to VEGF can be achieved that may be useful for the design of small molecule antagonists.     

Up-regulation of vascular endothelial growth factor in response to glucose deprivation

Vascular endothelial growth factor (VEGF), also known as a vascular permeability factor (VPF), is an endothelial specific mitogen and is a potent inducer of angiogenesis. Recently it has been reported that hypoxia induces VEGF mRNA expression in various cells. Since both oxygen and glucose are required for efficient production of energy, we examined the effect of glucose deprivation on VEGF mRNA expression and VEGF protein production in U-937 (a human monocytic cell line) cells. Both the mRNA expression and secretion of VEGF increased after exposure to low glucose. Addition of L-glucose, the L-stereoisomer of D-glucose, did not prevent the up-regulation of VEGF expression. The conditioned medium from glucose-deprived cells, followed by supplementation with glucose, did not up-regulate VEGF mRNA expression in U-937 cells. The low glucose-induced VEGF mRNA expression returned to the control level after supplementation with D-glucose. Furthermore, oligomycin, a mitochondrial ATP synthase inhibitor, increased VEGF protein production. The results suggest that the up-regulation of VEGF mRNA in U-937 cells in response to glucose deprivation is not mediated by autocrine factors from the cells nor is the osmotic change of the medium mediated by the deficiency of glucose metabolism in the cells. Our results also suggest that the intracellular ATP depletion due to glucose deprivation may be one of the causes for increased VEGF mRNA expression. We speculate that local hypoglycemia may act as an essential trigger for angiogenesis through the VEGF gene expression.     

p38丝裂原素激活的蛋白激酶在调节低氧诱导人内皮细胞分泌血管内皮生长因子过程中的作用

血管内皮细胞中血管内皮生长因子(vascular endothelial growthfactor,VEGF)的合成增加在促进血管新生的过程中起着非常重要的作用.然而低氧诱导VEGF分泌的细胞内信号转导机制还不是很清楚.人脐静脉内皮细胞系(ECV304)在低氧或常氧的状态下培养12～24 h后分别用实时定量PCR和Western blot的方法来检测VEGF mRNA的表达及ERK1/2和p38激酶的磷酸化水平.分泌到培养液中的VEGF蛋白用酶联免疫吸附(ELISA)的方法来检测.业已报道,ERK的抑制剂PD98059能够抑制低氧诱导的VEGF基因的表达,根据这个报道,我们发现在低氧情况下,ECV304细胞的ERK1/2磷酸化水平增高以及VEGF的合成增加等这些变化也能被PD98059所抑制.本次实验的新发现是p38激酶的激活在低氧诱导VEGF合成增加中的作用.p38激酶的抑制剂SB202190能抑制低氧诱导的VEGF合成增加.这些数据首次直接证实了p38激酶在低氧诱导人内皮细胞分泌VEGF增加过程中的作用.