Vascular endothelial growth factor and nitric oxide in rat liver regeneration

In this work we investigated the role of nitric oxide (NO) in the angiogenesis mediated by vascular endothelial growth factor (VEGF) during rat liver regeneration after two-thirds partial hepatectomy. Sham operated (Sh) and partially hepatectomized (PH) male Wistar rats were randomized in three experimental groups: control (treated with vehicle); pre-treated with sodium nitroprusside (SNP: 0.25 mg/kg body weight, i.v. at a rate of 1 ml/h) and pre-treated with the preferential iNOS inhibitor, aminoguanidine (AG, 100 mg/kg body weight, i.p.). Animals were killed at 5, 24 and 72 h after surgery. At 5 h post-surgery, NO production was estimated by EPR (Sh-Control: 37.65+/-10.70; PH-Control: 88.13+/-1.60(); Sh-SNP: 90.35+/-3.11(); PH-SNP: 119.5+/-12.10()(#); Sh-AG: 33.27+/-5.23, PH-AG: 36.80+/-3.40(#)) (p<0.05 vs Sh-Control; (#)p<0.05 vs PH-Control). At 24 h after PH, VEGF levels showed no difference between PH-Control and PH-SNP animals. However, after 72 h, VEGF protein levels in PH-SNP animals were found to be increased (above 300%) with respect to PH-Control. On the other hand, aminoguanidine (AG) pre-treatment blocked the rise of inhibition of NO generation and decreased VEGF expression. Our results demonstrated that NO plays a role in modulating VEGF protein expression after hepatectomy in rats.     

Vascular endothelial growth factor and hepatocyte regeneration in acetaminophen toxicity

VEGF or VEGF-A is a major regulator of angiogenesis and has been recently shown to be important in organ repair. The potential role of VEGF in acetaminophen (APAP)-induced hepatotoxicity and recovery was investigated in B6C3F1 male mice. Mice were treated with APAP (300 mg/kg ip) and killed at various time points that reflect both the acute and recovery stages of toxicity. VEGF-A protein levels were increased 7-fold at 8 h and followed the development of hepatotoxicity. VEGF receptor 1, 2, and 3 (VEGFR1, VEGFR2, and VEGFR3, respectively) expression increased throughout the time course, with maximal expression at 48, 8, and 72 h, respectively. Treatment with the VEGF receptor inhibitor SU5416 (25 mg/kg ip at 3 h) had no effect on toxicity at 6 or 24 h. In further studies, the role of SU5416 on the late stages of toxicity was examined. Treatment of mice with APAP and SU5416 (25 mg/kg ip at 3 h) resulted in decreased expression of PCNA, a marker of cellular proliferation. Expression of platelet endothelial cell adhesion molecule, a measure of small vessel density, and endothelial nitric oxide synthase (NOS), a downstream target of VEGFR2, were increased at 48 and 72 h following toxic doses of APAP, and treatment with SU5416 decreased their expression. These data indicate that endogenous VEGF is critically important to the process of hepatocyte regeneration in APAP-induced hepatotoxicity in the mouse.     

Vascular endothelial growth factor in the lung

Vascular endothelial growth factor (VEGF) is a pluripotent growth and permeability factor that has a broad impact on endothelial cell function. The lung tissue is very rich in this protein; many different lung cells produce VEGF and also respond to VEGF. VEGF is critical for the development of the lung and serves as a maintenance factor during adult life. In addition to the physiological functions of this protein, there is increasing evidence that VEGF also plays a role in several acute and chronic lung diseases, such as acute lung injury, severe pulmonary hypertension, and emphysema. Here we provide a comprehensive overview of the rapidly expanding literature.     

血管内皮生长因子受体--结构与功能

血管内皮生长因子 (VEGF)的生物学效应是通过其特异的膜受体介导实现的。迄今发现VEGF有三种受体 ,受体的结构、功能 ,及VEGF的信号转导途径各不相同 ,也一直是VEGF研究的热点。本文主要综述了这方面的进展。     

Vascular endothelial growth factor and its receptors

Vascular endothelial growth factor (VEGF) is a prime regulator of endothelial cell proliferation, angiogenesis, vasculogenesis and vascular permeability. Its activity is mediated by the high affinity tyrosine kinase receptors, KDR/Flk-1 and Flt-1. In this article, recently discovered structural, molecular and biological properties of VEGF are described. Among the topics discussed are VEGF and VEGF receptor structure and bioactivity, the regulation of VEGF expression, the role of VEGF and its receptors in vascular development, and the involvement of VEGF and its receptors in normal and pathological (ocular and tumor) angiogenesis.     

血管内皮生长因子与一氧化氮

血管内皮生长因子（ＶＥＧＦ）是内皮细胞特异性促有丝分裂原,具有促进内皮细胞增生、迁移及增加血管通透性的作用,其强大的促进新血管形成的作用使其在梗塞性血管病的基因治疗中发挥巨大作用。但其作用机制仍不清楚。研究表明ＶＥＧＦ与一氧化氮９ＮＯ）间存在密切关系,ＮＯ是ＶＥＧＦ发挥许多重要生理作用过程中必不可少的因素。探讨ＶＥＧＦ与ＮＯ的关系有助于进一步阐明ＶＥＧＦ的作用机制。     

Vascular endothelial growth factor can signal through platelet-derived growth factor receptors

Vascular endothelial growth factor (VEGF-A) is a crucial stimulator of vascular cell migration and proliferation. Using bone marrow-derived human adult mesenchymal stem cells (MSCs) that did not express VEGF receptors, we provide evidence that VEGF-A can stimulate platelet-derived growth factor receptors (PDGFRs), thereby regulating MSC migration and proliferation. VEGF-A binds to both PDGFRalpha and PDGFRbeta and induces tyrosine phosphorylation that, when inhibited, results in attenuation of VEGF-A-induced MSC migration and proliferation. This mechanism was also shown to mediate human dermal fibroblast (HDF) migration. VEGF-A/PDGFR signaling has the potential to regulate vascular cell recruitment and proliferation during tissue regeneration and disease.     

Vascular endothelial growth factor and placenta growth factor in intrauterine growth-restricted fetuses and neonates

The angiogenic factors vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) are respectively up- and downregulated by hypoxia. We aimed to study circulating levels of the above factors in intrauterine growth restriction (IUGR) and to correlate their levels with the customized centiles of the infants. The study included 25 IUGR and 25 appropriate for gestational age (AGA) full-term, singleton infants and their mothers. Maternal (MS), fetal (UC), and neonatal day 1 (N1) and 4 (N4) blood was examined. MS and N1 PlGF, as well as UC VEGF levels correlated with the customized centiles of the infants (r= 0.39, P=.007, r=0.34, P=.01, and r= -0.41, P=.004, resp). Furthermore, UC, N1, and N4 VEGF levels were higher in girls (r=0.36, P=.01, r=0.33, P=.02, and r=0.41, P=.005 resp). In conclusion, positive and negative correlations of examined factors with the customized centiles of the infant could rely on placental function and intrauterine oxygen concentrations-both being usually lower in IUGR cases-while higher VEGF levels in girls should possibly be attributed to the stimulating action of estrogens.     

Vascular endothelial growth factor, vascular endothelial growth factor receptor-3 and cyclooxygenase-2 expression in psoriasis

OBJECTIVE: To investigate expression patterns and relationship of vascular endothelial growth factor (VEGF), vascular endothelial receptor-3 (VEGF-R3) (FLT-4) and cyclooxygenase-2 (COX-2) in psoriasis. STUDY DESIGN: Forty-three patients were included in this study. The clinical severity of psoriasis was assessed using the psoriasis area and severity index (PASI). Punch biopsy samples both from psoriatic and nonlesional skin were taken and VEGF, VEGF-R3 and COX-2 expressions determined. RESULTS: VEGF, VEGF-R3 and COX-2 expressions were detected in 90.9%, 78.0% and 86.4% of psoriatic and 84.1%, 71.8%, and 84.1% of nonlesional skin, respectively. Epidermal VEGF, VEGF-R3 and COX-2 expressions were detected in 56.8%, 77.8% and 34.1 of psoriatic and 75%, 78.1% and 65.9% of nonlesional skin, respectively. In dermis, VEGF, VEGF-R3 and COX-2 expression was observed in 88.6%, 77.5% and 84.1% of psoriatic and 81.8%, 64.1% and 77.3% of nonlesional skin, respectively. Among the PASI subgroups no statistically significant differences were detected for VEGF, VEGF-R3 and COX-2 expression. CONCLUSION: Our study demonstrated that VEGF, VEGF-R3 and COX-2 expression in psoriatic and nonlesional skin is significantly high in epidermis and dermis. Although there was significant concordance between VEGF and VEGF-R3 expressions in psoriatic lesions, there seems to be no concordance between the others.     

Vascular endothelial growth factor and vascular endothelial growth factor receptor-2 expression in the chick embryo area vasculosa

Vascular endothelial growth factor is an angiogenic factor in vivo and in vitro that plays a crucial role in the control of blood vessel development and in pathological angiogenesis. The vascularized extraembryonic membranes of the chick embryo include the area vasculosa and the chorioallantoic membrane. In this study, we investigated the expression of vascular endothelial growth factor and of its receptor-2, specifically expressed by the endothelial cells, in the chick area vasculosa at days 6, 10 and 14 of incubation. Our results indicate that, in all the three developmental stages examined, vascular endothelial growth factor is clearly expressed in the endodermal cells immediately adjacent to the mesodermal endothelial cells which, in turn, expressed vascular endothelial growth factor receptor-2. These observations suggest that during the development of the vascular system, endodermal cells, expressing vascular endothelial growth factor, initiate angiogenesis by stimulating directly mesodermal cells, which express vascular endothelial growth factor receptor-2. Moreover, our data demonstrate that vascular endothelial growth factor receptor-2 expression is also maintained by endothelial cells in the later stages of development, until day 14 of incubation. In accord with other literature data, this suggests that vascular endothelial growth factor is required not only for proliferation, but also for the survival of endothelial cells.     

Vascular endothelial growth factor receptors in osteoclast differentiation and function

Osteoclasts are derived from haematopoietic stem cell precursors of the monocyte/macrophage cell lineage, through interaction with factors that are believed to include M-CSF and RANKL. VEGF is a proangiogenic cytokine that has been shown to promote osteoclast differentiation and survival. In this study, we assessed the role of VEGF and its receptors in osteoclastogenesis, in vitro, by culturing osteoclast precursors in the presence of VEGF, VEGF receptor-specific ligands, and blocking antibodies to VEGF receptors. Activation of VEGFR1 in the presence of RANKL induces osteoclast differentiation. Stimulating the receptors individually induced increased resorption by osteoclasts compared to controls but not to the level observed when stimulating both receptors simultaneously. We have shown that VEGF induces osteoclast differentiation through its action on VEGFR1. The way in which VEGF mediates its effect on mature osteoclast activity, however, may be through its interaction with both receptor subtypes.     

Vascular endothelial growth factor receptor-2 in breast cancer

Investigations over the last decade have established the essential role of growth factors and their receptors during angiogenesis and carcinogenesis. The vascular endothelial growth factor receptor (VEGFR) family in mammals contains three members, VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1) and VEGFR-3 (Flt-4), which are transmembrane tyrosine kinase receptors that regulate the formation of blood and lymphatic vessels. In the early 1990s, the above VEGFR was structurally characterized by cDNA cloning. Among these three receptors, VEGFR-2 is generally recognized to have a principal role in mediating VEGF-induced responses. VEGFR-2 is considered as the earliest marker for endothelial cell development. Importantly, VEGFR-2 directly regulates tumor angiogenesis. Therefore, several inhibitors of VEGFR-2 have been developed and many of them are now in clinical trials. In addition to targeting endothelial cells, the VEGF/VEGFR-2 system works as an essential autocrine/paracrine process for cancer cell proliferation and survival. Recent studies mark the continuous and increased interest in this related, but distinct, function of VEGF/VEGFR-2 in cancer cells: the autocrine/paracrine loop. Several mechanisms regulate VEGFR-2 levels and modulate its role in tumor angiogenesis and physiologic functions, i.e.: cellular localization/trafficking, regulation of cis-elements of promoter, epigenetic regulation and signaling from Notch, cytokines/growth factors and estrogen, etc. In this review, we will focus on updated information regarding VEGFR-2 research with respect to the molecular mechanisms of VEGFR-2 regulation in human breast cancer. Investigations in the activation, function, and regulation of VEGFR-2 in breast cancer will allow the development of new pharmacological strategies aimed at directly targeting cancer cell proliferation and survival.     

Vascular endothelial growth factor: biology and therapeutic applications

While the development of anti-angiogenic therapy, as it pertains to cancer treatment, may still be in its infancy relative to well-established modalities such as chemotherapy, radiation, and surgery, major strides made in the past several decades have allowed translation of basic science discoveries in this field into clinical reality. The discovery of key molecular modulators of angiogenesis, notably vascular endothelial growth factor (VEGF), has catalyzed the development of numerous neutralizing therapeutic agents. The validity of VEGF inhibition as a therapeutic strategy has been well supported in randomized clinical trials, as well as U.S. Food and Drug Administration approval of the VEGF antagonists bevacizumab, sunitinib malate, sorafenib, pegaptinib and ranibizumab. Accordingly, this review will (1) briefly review the basic molecular biology of VEGF and (2) summarize recent progress in targeting the VEGF molecular pathway as therapy for angiogenic diseases such as cancer and age-related macular degeneration.     

Vascular endothelial growth factor increases the intracellular magnesium

Vascular endothelial growth factor (VEGF) is one of the key players in the process of angiogenesis. However, its underlying mechanism remains unclear. Mg2+ is the most abundant intracellular divalent cation in the body and plays critical roles in many cell functions. We investigated the effect of VEGF on intracellular Mg2+ in human umbilical vein endothelial cells (HUVECs). VEGF-A165 increased the intracellular Mg2+ concentration ([Mg2+]i) in a dose-dependent manner, with or without extracellular Mg2+, and the increase of [Mg2+]i was blocked by pretreatment with SU1498, tyrosine kinase inhibitors (tyrphostin A-23 and genistein), phosphatidylinositol 3-kinase (PI3K) inhibitors (wortmannin and LY294002) or phospholipase Cgamma (PLCgamma) inhibitor (U73122). In contrast, mitogen-activated protein kinase inhibitors (SB202190 and PD98059) had no effect on the VEGF-induced [Mg2+]i increase. These results suggest that VEGF-A165 increases the [Mg2+]i from the intracellular Mg2+ stores through the tyrosine kinase/PI3K/PLCgamma-dependent signaling pathways.     

Vascular endothelial growth factor enhances atherosclerotic plaque progression

Vascular endothelial growth factor (VEGF) can promote angiogenesis but may also exert certain effects to alter the rate of atherosclerotic plaque development. To evaluate this potential impact on plaque progression, we treated cholesterol-fed mice doubly deficient in apolipoprotein E/apolipoprotein B100 with low doses of VEGF (2 microg/kg) or albumin. VEGF significantly increased macrophage levels in bone marrow and peripheral blood and increased plaque area 5-, 14- and 4-fold compared with controls at weeks 1, 2 and 3, respectively. Plaque macrophage and endothelial cell content also increased disproportionately over controls. In order to confirm that the VEGF-mediated plaque progression was not species-specific, the experiment was repeated in cholesterol-fed rabbits at the three-week timepoint, which showed comparable increases in plaque progression.     

Vascular endothelial growth factor inhibition: Conflicting roles in tumor growth

Angiogenesis, the physiological process of sprouting of new blood vessels from pre-existing ones, is a key biological feature of almost all cancers. Among the multitude of factors driving tumor angiogenesis, vascular endothelial growth factor (VEGF) is the most potent, exerting myriad effects on vascular pruning and sprouting, permeability, network formation, proliferation, and cell death. Despite the initial unimpressive clinical performance of anti-VEGF antibody (bevacizumab) as cancer monotherapy, clear improvements in clinical outcomes following combination bevacizumab and chemotherapy regimens and multi-targeted VEGF receptor tyrosine kinase inhibitors (sorafenib and sunitinib) in select tumor types have established VEGF-targeted agents as an effective means of controlling cancer growth. Prolongation of overall survival and cure with these agents, however, remains elusive. Moreover, recent data has revealed key differences in the therapeutic and biological tumor response to antibody versus receptor kinase VEGF inhibitors and suggested, at least pre-clinically, that VEGF blockade in certain circumstances may actually promote more aggressive tumor growth. Given the diverse mechanisms and potentially opposing roles of VEGF neutralization in cancer biology, identification of novel biomarkers predictive of in vivo angiogenic responses may hold the key to optimizing therapeutic outcomes of anti-VEGF therapy in future cancer patients.     

Vascular endothelial growth factor upregulates follistatin in human umbilical vein endothelial cells

Vascular endothelial growth factor (VEGF), plays a key role in angiogenesis. Many endogenous factors can affect angiogenesis in endothelial cells. VEGF is known to be a strong migration, sprouting, survival, and proliferation factor for endothelial cells during angiogenesis in endothelial cells. Searching for novel genes, involved in VEGF signaling during angiogenesis, we carried out differential display polymerase chain reaction on RNA from VEGF-stimulated human umbilical vein endothelial cells (HUVECs). In this study, follistatin (FS) differentially expressed in VEGF-treated HUVECs, compared with controls. Addition of VEGF (10 ng/mL) produced an approximately 11.8-fold increase of FS mRNA. FS or VEGF produced approximately 1.8- or 2.9-fold increases, respectively, in matrix metalloproteinase-2 (MMP-2) secretion for 12 h, compared to the addition of a control buffer. We suggest that VEGF may affect the angiogenic effect of HUVECs, through a combination of the direct effects of VEGF itself, and the indirect effects mediated via induction of FSin vitro.     

Evolutionary analysis of human vascular endothelial growth factor, angiopoietin, and tyrosine endothelial kinase involved in angiogenesis and immunity

Human vascular endothelial growth factor (VEGF), angiopoietin (ANG) and tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (TIE)-2 consist of a grouping of proteins that are involved in vascular homeostasis, vascular integrity and angiogenesis. There are nine proteins in the immediate VEGF family: VEGFA, VEGFB, VEGFC, VEGFD, VEGF-3, placental growth factor (PGF), VEGF receptor (VEGFR)-1, VEGFR-2, and VEGFR-1-related. They can be stimulated by cytokines to become involved in immune responses. By using in silico tools, we were able to identify several possible analogues or homologues of VEGF, ANG and TIE-2 in invertebrates. This is the first report to show that these proteins may be conserved through evolution. These proteins may have a role in vascular maintenance and immunity. In addition, since VEGF, ANG and TIE-2 have a role in mammalian immunity that is significantly influenced by cytokines, such as IL-1, this may indicate an interaction of the vascular system and the immune system over evolutionary time.     

Expression and role of vascular endothelial growth factor in liver regeneration after partial hepatectomy in rats.

Vascular endothelial growth factor (VEGF) plays a major role in angiogenesis, which is essential for both healing of injured tissue and proliferation of carcinoma cells. In this study we elucidated the expression and role of VEGF in rat liver regeneration after partial hepatectomy. VEGF expression was mainly detected in periportal hepatocytes and reached a maximal level 48-72 hr after partial hepatectomy by both immunohistochemistry and in situ hybridization. Similarly, immunohistochemistry for Ki-67 showed that the proliferative activity of sinusoidal endothelial cells was highest in the periportal area and reached a maximal level 72 hr after partial hepatectomy. Moreover, neutralization of VEGF significantly inhibited proliferative activity of hepatocytes (p<0. 0001), as well as sinusoidal endothelial cells (p<0.001), at 48 and 96 hr after partial hepatectomy. Conversely, injection of VEGF significantly promoted proliferative activity of hepatocytes (p<0. 0001) as well as sinusoidal endothelial cells (p<0.0005) at 48 hr after partial hepatectomy. These results suggest that VEGF promotes proliferation of hepatocytes through reconstruction of liver sinusoids by proliferation of sinusoidal endothelial cells. Furthermore, these data point to a new therapeutic strategy, the use of VEGF and other hepatocyte growth factors in fulminant or severe acute hepatitis.