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1.  Studies of Vascular Endothelial Growth Factor in Asthma and Chronic Obstructive Pulmonary Disease 
Vascular endothelial growth factor (VEGF) is a potent stimulator of vascular angiogenesis, permeability, and remodeling that also plays important roles in wound healing and tissue cytoprotection. To begin to define the roles of VEGF in diseases like asthma and COPD, we characterized the effects of lung-targeted transgenic VEGF165 and defined the innate immune pathways that regulate VEGF tissue responses. The former studies demonstrated that VEGF plays an important role in Th2 inflammation because, in addition to stimulating angiogenesis and edema, VEGF induced eosinophilic inflammation, mucus metaplasia, subepithelial fibrosis, myocyte hyperplasia, dendritic cell activation, and airways hyperresponsiveness via IL-13–dependent and -independent mechanisms. VEGF was also produced at sites of aeroallergen-induced Th2 inflammation, and VEGF receptor blockade ameliorated adaptive Th2 inflammation and Th2 cytokine elaboration. The latter studies demonstrated that activation of the RIG-like helicase (RLH) innate immune pathway using viral pathogen–associated molecular patterns such as Poly(I:C) or viruses ameliorated VEGF-induced tissue responses. In accord with these findings, Poly(I:C)-induced RLH activation also abrogated aeroallergen-induced Th2 inflammation. When viewed in combination, these studies suggest that VEGF excess can contribute to the pathogenesis of Th2 inflammatory disorders such as asthma and that abrogation of VEGF signaling via RLH activation can contribute to the pathogenesis of viral disorders such as virus-induced COPD exacerbations. They also suggest that RLH activation may be a useful therapeutic strategy in asthma and related disorders.
doi:10.1513/pats.201102-018MW
PMCID: PMC3359071  PMID: 22052929
asthma; chronic obstructive pulmonary disease; virus; RIG-like helicase; mitochondrial antiviral signaling molecule
2.  A Novel Tumor-Promoting Function Residing in the 5′ Non-coding Region of vascular endothelial growth factor mRNA 
PLoS Medicine  2008;5(5):e94.
Background
Vascular endothelial growth factor-A (VEGF) is one of the key regulators of tumor development, hence it is considered to be an important therapeutic target for cancer treatment. However, clinical trials have suggested that anti-VEGF monotherapy was less effective than standard chemotherapy. On the basis of the evidence, we hypothesized that vegf mRNA may have unrecognized function(s) in cancer cells.
Methods and Findings
Knockdown of VEGF with vegf-targeting small-interfering (si) RNAs increased susceptibility of human colon cancer cell line (HCT116) to apoptosis caused with 5-fluorouracil, etoposide, or doxorubicin. Recombinant human VEGF165 did not completely inhibit this apoptosis. Conversely, overexpression of VEGF165 increased resistance to anti-cancer drug-induced apoptosis, while an anti-VEGF165-neutralizing antibody did not completely block the resistance. We prepared plasmids encoding full-length vegf mRNA with mutation of signal sequence, vegf mRNAs lacking untranslated regions (UTRs), or mutated 5′UTRs. Using these plasmids, we revealed that the 5′UTR of vegf mRNA possessed anti-apoptotic activity. The 5′UTR-mediated activity was not affected by a protein synthesis inhibitor, cycloheximide. We established HCT116 clones stably expressing either the vegf 5′UTR or the mutated 5′UTR. The clones expressing the 5′UTR, but not the mutated one, showed increased anchorage-independent growth in vitro and formed progressive tumors when implanted in athymic nude mice. Microarray and quantitative real-time PCR analyses indicated that the vegf 5′UTR-expressing tumors had up-regulated anti-apoptotic genes, multidrug-resistant genes, and growth-promoting genes, while pro-apoptotic genes were down-regulated. Notably, expression of signal transducers and activators of transcription 1 (STAT1) was markedly repressed in the 5′UTR-expressing tumors, resulting in down-regulation of a STAT1-responsive cluster of genes (43 genes). As a result, the tumors did not respond to interferon (IFN)α therapy at all. We showed that stable silencing of endogenous vegf mRNA in HCT116 cells enhanced both STAT1 expression and IFNα responses.
Conclusions
These findings suggest that cancer cells have a survival system that is regulated by vegf mRNA and imply that both vegf mRNA and its protein may synergistically promote the malignancy of tumor cells. Therefore, combination of anti-vegf transcript strategies, such as siRNA-based gene silencing, with anti-VEGF antibody treatment may improve anti-cancer therapies that target VEGF.
Shigetada Teshima-Kondo and colleagues find that cancer cells have a survival system that is regulated by vegf mRNA and that vegf mRNA and its protein may synergistically promote the malignancy of tumor cells.
Editors' Summary
Background
Normally, throughout life, cell division (which produces new cells) and cell death are carefully balanced to keep the body in good working order. But sometimes cells acquire changes (mutations) in their genetic material that allow them to divide uncontrollably to form cancers—disorganized masses of cells. When a cancer is small, it uses the body's existing blood supply to get the oxygen and nutrients it needs for its growth and survival. But, when it gets bigger, it has to develop its own blood supply. This process is called angiogenesis. It involves the release by the cancer cells of proteins called growth factors that bind to other proteins (receptors) on the surface of endothelial cells (the cells lining blood vessels). The receptors then send signals into the endothelial cells that tell them to make new blood vessels. One important angiogenic growth factor is “vascular endothelial growth factor” (VEGF). Tumors that make large amounts of VEGF tend to be more abnormal and more aggressive than those that make less VEGF. In addition, high levels of VEGF in the blood are often associated with poor responses to chemotherapy, drug regimens designed to kill cancer cells.
Why Was This Study Done?
Because VEGF is a key regulator of tumor development, several anti-VEGF therapies—drugs that target VEGF and its receptors—have been developed. These therapies strongly suppress the growth of tumor cells in the laboratory and in animals but, when used alone, are no better at increasing the survival times of patients with cancer than standard chemotherapy. Scientists are now looking for an explanation for this disappointing result. Like all proteins, cells make VEGF by “transcribing” its DNA blueprint into an mRNA copy (vegf mRNA), the coding region of which is “translated” into the VEGF protein. Other, “noncoding” regions of vegf mRNA control when and where VEGF is made. Scientists have recently discovered that the noncoding regions of some mRNAs suppress tumor development. In this study, therefore, the researchers investigate whether vegf mRNA has an unrecognized function in tumor cells that could explain the disappointing clinical results of anti-VEGF therapeutics.
What Did the Researchers Do and Find?
The researchers first used a technique called small interfering (si) RNA knockdown to stop VEGF expression in human colon cancer cells growing in dishes. siRNAs are short RNAs that bind to and destroy specific mRNAs in cells, thereby preventing the translation of those mRNAs into proteins. The treatment of human colon cancer cells with vegf-targeting siRNAs made the cells more sensitive to chemotherapy-induced apoptosis (a type of cell death). This sensitivity was only partly reversed by adding VEGF to the cells. By contrast, cancer cells engineered to make more vegf mRNA had increased resistance to chemotherapy-induced apoptosis. Treatment of these cells with an antibody that inhibited VEGF function did not completely block this resistance. Together, these results suggest that both vegf mRNA and VEGF protein have anti-apoptotic effects. The researchers show that the anti-apoptotic activity of vegf mRNA requires a noncoding part of the mRNA called the 5′ UTR, and that whereas human colon cancer cells expressing this 5′ UTR form tumors in mice, cells expressing a mutated 5′ UTR do not. Finally, they report that the expression of several pro-apoptotic genes and of an anti-tumor pathway known as the interferon/STAT1 tumor suppression pathway is down-regulated in tumors that express the vegf 5′ UTR.
What Do These Findings Mean?
These findings suggest that some cancer cells have a survival system that is regulated by vegf mRNA and are the first to show that a 5′UTR of mRNA can promote tumor growth. They indicate that VEGF and its mRNA work together to promote their development and to increase their resistance to chemotherapy drugs. They suggest that combining therapies that prevent the production of vegf mRNA (for example, siRNA-based gene silencing) with therapies that block the function of VEGF might improve survival times for patients whose tumors overexpress VEGF.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050094.
This study is discussed further in a PLoS Medicine Perspective by Hughes and Jones
The US National Cancer Institute provides information about all aspects of cancer, including information on angiogenesis, and on bevacizumab, an anti-VEGF therapeutic (in English and Spanish)
CancerQuest, from Emory University, provides information on all aspects of cancer, including angiogenesis (in several languages)
Cancer Research UK also provides basic information about what causes cancers and how they develop, grow, and spread, including information about angiogenesis
Wikipedia has pages on VEGF and on siRNA (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
doi:10.1371/journal.pmed.0050094
PMCID: PMC2386836  PMID: 18494554
3.  RIG-like Helicase Innate Immunity Inhibits Vascular Endothelial Growth Factor Tissue Responses via a Type I IFN–dependent Mechanism 
Rationale: Vascular endothelial growth factor (VEGF) regulates vascular, inflammatory, remodeling, and cell death responses. It plays a critical role in normal pulmonary physiology, and VEGF excess and deficiency have been implicated in the pathogenesis of asthma and chronic obstructive pulmonary disease, respectively. Although viruses are an important cause of chronic obstructive pulmonary disease exacerbations and innate responses play an important role in these exacerbations, the effects of antiviral responses on VEGF homeostasis have not been evaluated.
Objectives: We hypothesized that antiviral innate immunity regulates VEGF tissue responses.
Methods: We compared the effects of transgenic VEGF165 in mice treated with viral pathogen–associated molecular pattern polyinosinic:polycytidylic acid [poly(I:C)], mice treated with live virus, and control mice.
Measurements and Main Results: Transgenic VEGF stimulated angiogenesis, edema, inflammation, and mucin accumulation. Each of these was abrogated by poly(I:C). These inhibitory effects were dose dependent, noted when poly(I:C) was administered before and after transgene activation, and mediated by a Toll-like receptor-3–independent and RIG-like helicase (RLH)– and type I IFN receptor–dependent pathway. VEGF stimulated the expression of VEGF receptor-1 and poly(I:C) inhibited this stimulation. Poly(I:C) also inhibited the ability of VEGF to activate extracellular signal–regulated kinase-1, Akt, focal adhesion kinase, and endothelial nitric oxide synthase, and aeroallergen-induced adaptive helper T-cell type 2 inflammation. Influenza and respiratory syncytial virus also inhibited VEGF-induced angiogenesis.
Conclusions: These studies demonstrate that poly(I:C) and respiratory viruses inhibit VEGF-induced tissue responses and adaptive helper T-cell type 2 inflammation and highlight the importance of a RLH- and type I IFN receptor–dependent pathway(s) in these regulatory events. They define a novel link between VEGF and antiviral and RLH innate immune responses and a novel pathway that regulates pulmonary VEGF activity.
doi:10.1164/rccm.201008-1276OC
PMCID: PMC3114061  PMID: 21278304
RIG-like helicase; mitochondrial antiviral signaling molecule; influenza virus; chronic obstructive pulmonary disease
4.  Protective role of vascular endothelial growth factor in endotoxin-induced acute lung injury in mice 
Respiratory Research  2007;8(1):60.
Background
Vascular endothelial growth factor (VEGF), a substance that stimulates new blood vessel formation, is an important survival factor for endothelial cells. Although overexpressed VEGF in the lung induces pulmonary edema with increased lung vascular permeability, the role of VEGF in the development of acute lung injury remains to be determined.
Methods
To evaluate the role of VEGF in the pathogenesis of acute lung injury, we first evaluated the effects of exogenous VEGF and VEGF blockade using monoclonal antibody on LPS-induced lung injury in mice. Using the lung specimens, we performed TUNEL staining to detect apoptotic cells and immunostaining to evaluate the expression of apoptosis-associated molecules, including caspase-3, Bax, apoptosis inducing factor (AIF), and cytochrome C. As a parameter of endothelial permeability, we measured the albumin transferred across human pulmonary artery endothelial cell (HPAEC) monolayers cultured on porous filters with various concentrations of VEGF. The effect of VEGF on apoptosis HPAECs was also examined by TUNEL staining and active caspase-3 immunoassay.
Results
Exogenous VEGF significantly decreased LPS-induced extravascular albumin leakage and edema formation. Treatment with anti-VEGF antibody significantly enhanced lung edema formation and neutrophil emigration after intratracheal LPS administration, whereas extravascular albumin leakage was not significantly changed by VEGF blockade. In lung pathology, pretreatment with VEGF significantly decreased the numbers of TUNEL positive cells and those with positive immunostaining of the pro-apoptotic molecules examined. VEGF attenuated the increases in the permeability of the HPAEC monolayer and the apoptosis of HPAECs induced by TNF-α and LPS. In addition, VEGF significantly reduced the levels of TNF-α- and LPS-induced active caspase-3 in HPAEC lysates.
Conclusion
These results suggest that VEGF suppresses the apoptosis induced by inflammatory stimuli and functions as a protective factor against acute lung injury.
doi:10.1186/1465-9921-8-60
PMCID: PMC2042500  PMID: 17718922
5.  The early responses of VEGF and its receptors during acute lung injury: implication of VEGF in alveolar epithelial cell survival 
Critical Care  2006;10(5):R130.
Introduction
The function of the vascular endothelial growth factor (VEGF) system in acute lung injury (ALI) is controversial. We hypothesized that the role of VEGF in ALI may depend upon the stages of pathogenesis of ALI.
Methods
To determine the responses of VEGF and its receptors during the early onset of ALI, C57BL6 mice were subjected to intestinal ischemia or sham operation for 30 minutes followed by intestinal ischemia-reperfusion (IIR) for four hours under low tidal volume ventilation with 100% oxygen. The severity of lung injury, expression of VEGF and its receptors were assessed. To further determine the role of VEGF and its type I receptor in lung epithelial cell survival, human lung epithelial A549 cells were treated with small interference RNA (siRNA) to selectively silence related genes.
Results
IIR-induced ALI featured interstitial inflammation, enhancement of pulmonary vascular permeability, increase of total cells and neutrophils in the bronchoalveolar lavage (BAL), and alveolar epithelial cell death. In the BAL, VEGF was significantly increased in both sham and IIR groups, while the VEGF and VEGF receptor (VEGFR)-1 in the lung tissues were significantly reduced in these two groups. The increase of VEGF in the BAL was correlated with the total protein concentration and cell count. Significant negative correlations were observed between the number of VEGF or VEGFR-1 positive cells, and epithelial cells undergoing cell death. When human lung epithelial A549 cells were pre-treated with 50 nM of siRNA either against VEGF or VEGFR-1 for 24 hours, reduced VEGF and VEGFR-1 levels were associated with reduced cell viability.
Conclusion
These results suggest that VEGF may have dual roles in ALI: early release of VEGF may increase pulmonary vascular permeability; reduced expression of VEGF and VEGFR-1 in lung tissue may contribute to the death of alveolar epithelial cells.
doi:10.1186/cc5042
PMCID: PMC1751039  PMID: 16968555
6.  Pharmacokinetics and pharmacodynamics of VEGF-neutralizing antibodies 
BMC Systems Biology  2011;5:193.
Background
Vascular endothelial growth factor (VEGF) is a potent regulator of angiogenesis, and its role in cancer biology has been widely studied. Many cancer therapies target angiogenesis, with a focus being on VEGF-mediated signaling such as antibodies to VEGF. However, it is difficult to predict the effects of VEGF-neutralizing agents. We have developed a whole-body model of VEGF kinetics and transport under pathological conditions (in the presence of breast tumor). The model includes two major VEGF isoforms VEGF121 and VEGF165, receptors VEGFR1, VEGFR2 and co-receptors Neuropilin-1 and Neuropilin-2. We have added receptors on parenchymal cells (muscle fibers and tumor cells), and incorporated experimental data for the cell surface density of receptors on the endothelial cells, myocytes, and tumor cells. The model is applied to investigate the action of VEGF-neutralizing agents (called "anti-VEGF") in the treatment of cancer.
Results
Through a sensitivity study, we examine how model parameters influence the level of free VEGF in the tumor, a measure of the response to VEGF-neutralizing drugs. We investigate the effects of systemic properties such as microvascular permeability and lymphatic flow, and of drug characteristics such as the clearance rate and binding affinity. We predict that increasing microvascular permeability in the tumor above 10-5 cm/s elicits the undesired effect of increasing tumor interstitial VEGF concentration beyond even the baseline level. We also examine the impact of the tumor microenvironment, including receptor expression and internalization, as well as VEGF secretion. We find that following anti-VEGF treatment, the concentration of free VEGF in the tumor can vary between 7 and 233 pM, with a dependence on both the density of VEGF receptors and co-receptors and the rate of neuropilin internalization on tumor cells. Finally, we predict that free VEGF in the tumor is reduced following anti-VEGF treatment when VEGF121 comprises at least 25% of the VEGF secreted by tumor cells.
Conclusions
This study explores the optimal drug characteristics required for an anti-VEGF agent to have a therapeutic effect and the tumor-specific properties that influence the response to therapy. Our model provides a framework for investigating the use of VEGF-neutralizing drugs for personalized medicine treatment strategies.
doi:10.1186/1752-0509-5-193
PMCID: PMC3229549  PMID: 22104283
7.  Regulation of alternative VEGF-A mRNA splicing is a therapeutic target for analgesia☆ 
Neurobiology of Disease  2014;71:245-259.
Vascular endothelial growth factor-A (VEGF-A) is best known as a key regulator of the formation of new blood vessels. Neutralization of VEGF-A with anti-VEGF therapy e.g. bevacizumab, can be painful, and this is hypothesized to result from a loss of VEGF-A-mediated neuroprotection. The multiple vegf-a gene products consist of two alternatively spliced families, typified by VEGF-A165a and VEGF-A165b (both contain 165 amino acids), both of which are neuroprotective. Under pathological conditions, such as in inflammation and cancer, the pro-angiogenic VEGF-A165a is upregulated and predominates over the VEGF-A165b isoform.
We show here that in rats and mice VEGF-A165a and VEGF-A165b have opposing effects on pain, and that blocking the proximal splicing event – leading to the preferential expression of VEGF-A165b over VEGF165a – prevents pain in vivo. VEGF-A165a sensitizes peripheral nociceptive neurons through actions on VEGFR2 and a TRPV1-dependent mechanism, thus enhancing nociceptive signaling. VEGF-A165b blocks the effect of VEGF-A165a.
After nerve injury, the endogenous balance of VEGF-A isoforms switches to greater expression of VEGF-Axxxa compared to VEGF-Axxxb, through an SRPK1-dependent pre-mRNA splicing mechanism. Pharmacological inhibition of SRPK1 after traumatic nerve injury selectively reduced VEGF-Axxxa expression and reversed associated neuropathic pain. Exogenous VEGF-A165b also ameliorated neuropathic pain.
We conclude that the relative levels of alternatively spliced VEGF-A isoforms are critical for pain modulation under both normal conditions and in sensory neuropathy. Altering VEGF-Axxxa/VEGF-Axxxb balance by targeting alternative RNA splicing may be a new analgesic strategy.
Graphical abstract
Highlights
•The different vegf-a splice variants, VEGF-A165a and VEGF-A165b have pro- and anti-nociceptive actions respectively.•Pro-nociceptive actions of VEGF-A165a are dependent on TRPV1.•Alternative pre-mRNA splicing underpins peripheral sensitization by VEGF-A isoforms in normal and neuropathic animals.
doi:10.1016/j.nbd.2014.08.012
PMCID: PMC4194316  PMID: 25151644
VEGF-A, vascular endothelial growth factor-A; SRPK1, serine arginine protein kinase 1; SRSF1, serine arginine splice factor 1; VEGFR2, vascular endothelial growth factor receptor 2; IB4, isolectin B4; TRPV1, transient receptor potential vanilloid 1; CV, conduction velocity; PSNI, partial saphenous nerve ligation injury; DRG, dorsal root ganglia; Vascular endothelial growth factor A; Alternative mRNA splicing; Neuropathy; Nociceptors
8.  507 The Protective Effects of Exogenous IGFBP-3 on Allergic Airway Inflammation through Blockade of vegf Production 
Background
Bronchial asthma is a chronic airway inflammatory disease that is usually accompanied by increased vascular leakage, resulting in plasma exudation. Vascular endothelial growth factor (VEGF) plays as a pro-inflammatory mediator as well as a vascular permeability factor in bronchial asthma. Insulin-like growth factor (IGF)-I is also involved in the inflammatory process associated with bronchial asthma and it has been demonstrated to stimulate VEGF expression. The IGF binding proteins (IGFBPs) are a complex family of proteins which bind IGFs with high affinity. IGFBPs, especially IGFBP-3, display distinctive properties and can interfere with various biological processes. However, there are little data on the effect and the molecular basis of IGFBP-3 on allergen-induced bronchial inflammation and airway hyper-responsiveness.
Methods
This study was aimed to investigate the related signaling regarding the action of IGFBP-3 on bronchial inflammation and airway hyper-responsiveness in allergic airway disease of mice.
Results
In this study with an ovalbumin (OVA)-induced murine model of allergic airway disease, the increases of HIF-1a/HIF-2a activity and VEGF protein levels in lungs after OVA inhalation were blocked substantially by the administration of IGFBP-3. We also showed that the increased numbers of inflammatory cells of the airways, airway hyper-responsiveness, and increased levels of IL-4, IL-5, IL-13, and vascular permeability in lungs after OVA inhalation were significantly reduced by the administration of IGFBP-3.
Conclusions
These results indicate that IGFBP-3 may attenuate antigen-induced airway inflammation and hyper-responsiveness through the modulation of vascular leakage and VEGF expression mediated by HIF-1a/HIF-2a in allergic airway disease of mice.
doi:10.1097/01.WOX.0000411622.48431.fe
PMCID: PMC3512757
9.  Müller Cell-Derived VEGF Is Essential for Diabetes-Induced Retinal Inflammation and Vascular Leakage 
Diabetes  2010;59(9):2297-2305.
OBJECTIVE
Vascular endothelial growth factor (VEGF-A or VEGF) is a major pathogenic factor and therapeutic target for diabetic retinopathy (DR). Since VEGF has been proposed as a survival factor for retinal neurons, defining the cellular origin of pathogenic VEGF is necessary for the effectiveness and safety of long-term anti-VEGF therapies for DR. To determine the significance of Müller cell-derived VEGF in DR, we disrupted VEGF in Müller cells with an inducible Cre/lox system and examined diabetes-induced retinal inflammation and vascular leakage in these conditional VEGF knockout (KO) mice.
RESEARCH DESIGN AND METHODS
Leukostasis was determined by counting the number of fluorescently labeled leukocytes inside retinal vasculature. Expression of biomarkers for retinal inflammation was assessed by immunoblotting of TNF-α, ICAM-1, and NF-κB. Vascular leakage was measured by immunoblotting of retinal albumin and fluorescent microscopic analysis of extravascular albumin. Diabetes-induced vascular alterations were examined by immunoblotting and immunohistochemistry for tight junctions, and by trypsin digestion assays for acellular capillaries. Retinal integrity was analyzed with morphologic and morphometric analyses.
RESULTS
Diabetic conditional VEGF KO mice exhibited significantly reduced leukostasis, expression of inflammatory biomarkers, depletion of tight junction proteins, numbers of acellular capillaries, and vascular leakage compared to diabetic control mice.
CONCLUSIONS
Müller cell-derived VEGF plays an essential and causative role in retinal inflammation, vascular lesions, and vascular leakage in DR. Therefore, Müller cells are a primary cellular target for proinflammatory signals that mediates retinal inflammation and vascular leakage in DR.
doi:10.2337/db09-1420
PMCID: PMC2927953  PMID: 20530741
10.  Vascular endothelial growth factor C promotes breast cancer progression via a novel antioxidant mechanism that involves regulation of superoxide dismutase 3 
Introduction
Triple-negative breast cancers, particularly the claudin-low subtype, are highly aggressive and exhibit increased tumor-initiating cell (TIC) characteristics. In this study, we demonstrate that vascular endothelial growth factor C (VEGF-C) is highly expressed in the claudin-low breast cancer subtype and also that it mediates tumor progression, not only through its role in lymphangiogenesis but also through regulating TIC characteristics and the response to reactive oxygen species (ROS).
Methods
VEGF C expression was examined in breast cancer subtypes, and a VEGF C expression signature was derived. VEGF C expression and/or its associated signature was correlated with TIC and chemoresistance signatures. In vitro and in vivo assays were performed to determine whether VEGF-C expression alters TIC characteristics and the response of breast cancer cells to chemotherapy and oxidative stress. Array analysis was used to identify a downstream effector of VEGF-C, superoxide dismutase 3 (Sod3), which was tested for its involvement in VEGF-C-mediated resistance to oxidative stress and enhancement of in vivo metastasis. The VEGF-C-associated receptor neuropilin 2 (Nrp2) was knocked down to determine whether it is required for the observed effects of VEGF-C. Expression of VEGF C and Sod3 was assessed in human breast cancers.
Results
VEGF C is highly expressed in claudin-low breast cancers, and VEGF C and the VEGF C signature are associated with TIC-related gene signatures. VEGF-C-knockdown in mammary carcinoma cells decreases TIC properties in vitro and in vivo, sensitizing cells to oxidative stress and chemotherapy. We identified Sod3 as a target of VEGF-C in breast cancer cells by demonstrating that it is required for VEGF-C-mediated cell survival in response to oxidative stress and for VEGF-C-mediated metastasis. We demonstrate that Nrp2 is the VEGF-C-associated receptor that mediates alterations in Sod3 expression and the response of tumor cells to oxidative stress. We show that VEGF C and Sod3 are positively associated in human breast cancer.
Conclusions
We describe a novel mechanism by which VEGF-C contributes to metastasis via its ability to enhance TIC-associated characteristics, particularly the response to ROS. We identified Sod3 as a critical mediator of VEGF-C-induced metastasis, and we provide evidence that the VEGF-C–Sod3 axis plays a role in human breast cancers.
Electronic supplementary material
The online version of this article (doi:10.1186/s13058-014-0462-2) contains supplementary material, which is available to authorized users.
doi:10.1186/s13058-014-0462-2
PMCID: PMC4303136  PMID: 25358638
11.  Lung vascular endothelial growth factor expression induces local myeloid dendritic cell activation 
Clinical immunology (Orlando, Fla.)  2009;132(3):371-384.
We previously demonstrated that vascular endothelial growth factor (VEGF) expression in the murine lung increases local CD11c+ MHCII+ DC number and activation. In this study, employing a multicolor flow cytometry, we report increases in both myeloid (mDC) and plasmacytoid (pDC) DC in the lungs of VEGF transgenic (tg) compared to WT mice. Lung pDC from VEGF tg mice exhibited higher levels of activation with increased expression of MHCII and costimulatory molecules. As VEGF tg mice display an asthma-like phenotype and lung mDC play a critical role in asthmatic setting, studies were undertaken to further characterize murine lung mDC. Evaluations of sorted mDC from VEGF tg lungs demonstrated a selective upregulation of cathepsin K, MMP-8, -9, -12, and -14, and chemokine receptors as compared to those obtained from WT control mice. They also had increased VEGFR2 but downregulated VEGFR1 expression. Analysis of chemokine and regulatory cytokine expression in these cells showed an upregulation of macrophage chemotactic protein-3 (MCP-3), thymus-expressed chemokine (TECK), secondary lymphoid organ chemokine (SLC), macrophage-derived chemokine (MDC), IL-1β, IL-6, IL-12 and IL-13. The antigen (Ag) OVA-FITC uptake by lung DC and the migration of Ag-loaded DC to local lymph nodes were significantly increased in VEGF tg mice compared to WT mice. Thus, VEGF may predispose the lung to inflammation and/or repair by activating local DC. It regulates lung mDC expression of innate immunity effector molecules. The data presented here demonstrate how lung VEGF expression functionally affects local mDC for the transition from the innate response to a Th2-type inflammatory response.
doi:10.1016/j.clim.2009.05.016
PMCID: PMC2780370  PMID: 19553159
Rodent; lung; inflammation; dendritic cells; cell activation
12.  Silver nanoparticles modify VEGF signaling pathway and mucus hypersecretion in allergic airway inflammation 
The anti-inflammatory action of silver nanoparticles (NPs) has been reported in a murine model of asthma in a previous study. But more specific mechanisms of silver NPs in an attenuation of allergic airway inflammation have not yet been established. Vascular and mucous changes are believed to contribute largely in pathophysiology in asthma. Among various factors related to vascular changes, vascular endothelial growth factor (VEGF) plays a pivotal role in vascular changes in asthma. Mucin proteins MUC5AC and MUC5B have been implicated as markers of goblet cell metaplasia in lung pathologies. The aim of this study was to investigate the effects of silver NPs on VEGF signaling pathways and mucus hypersecretion. Ovalbumin (OVA)-inhaled female BALBc mice were used to evaluate the role of silver NPs and the related molecular mechanisms in allergic airway disease. In this study, with an OVA-induced murine model of allergic airway disease, it was found that the increased levels of hypoxia-inducible factor (HIF)-1α, VEGF, phosphatidylinositol-3 kinase (PI3K) and phosphorylated-Akt levels, and mucous glycoprotein expression (Muc5ac) in lung tissues were substantially decreased by the administration of silver NPs. In summary, silver NPs substantially suppressed mucus hypersecretion and PI3K/HIF-1α/VEGF signaling pathway in an allergic airway inflammation.
doi:10.2147/IJN.S27159
PMCID: PMC3310409  PMID: 22457593
allergic airway disease; hypoxia inducible factor-1α; vascular endothelial growth factor
13.  Granzyme B Releases Vascular Endothelial Growth Factor from Extracellular Matrix and Induces Vascular Permeability 
The formation of unstable, leaky neovessels underlies the pathogenesis of many chronic inflammatory diseases. Granzyme B (GZMB) is an immune-derived serine protease that accumulates in the extracellular matrix (ECM) during chronic inflammation and is capable of cleaving fibronectin (FN). Vascular endothelial growth factor (VEGF) is a potent vascular permeabilizing agent that is sequestered in the ECM through its interaction with FN. As GZMB levels are elevated in chronic inflammatory diseases that are associated with increased vascular permeability, the role of GZMB in the regulation of VEGF bioavailability and vascular permeability were assessed.
Methods and Results
GZMB was added to either VEGF-bound to FN or VEGF-bound to endothelial cell (EC)-derived ECM. Supernatants containing released VEGF were assessed to determine VEGF activity by treating EC and evaluating VEGF receptor-2 (VEGFR2) phosphorylation. GZMB released VEGF from both FN and from EC-derived matrix, while GZMB inhibition prevented FN cleavage and VEGF release. GZMB-mediated VEGF release resulted in significant phosphorylation of VEGFR2. The role of GZMB-mediated VEGF release in altering vascular permeability was also assessed in vivo using a Miles/Evan’s Blue permeability assay. GZMB induced a significant VEGF-dependent increase in vascular permeability in vivo that was reduced in the presence of an anti-VEGF neutralizing antibody. Inflammatory-mediated vascular leakage was also assessed in GZMB-KO mice using a delayed-type hypersensitivity model. GZMB-KO mice exhibited reduced microvascular leakage compared to C57\B6 controls.
Conclusions
GZMB increases vascular permeability in part through the proteolytic release of ECM-sequestered VEGF leading to VEGFR2 activation and increased vascular permeability in vivo. These findings present a novel role for GZMB as a modulator of vascular response during chronic inflammation.
doi:10.1038/labinvest.2014.62
PMCID: PMC4074428  PMID: 24791744 CAMSID: cams4292
Fibronectin; Granzyme B; Inflammation; VEGF; Vascular permeability
14.  The effects of budesonide on angiogenesis in a murine asthma model 
Introduction
The aim of this study is to determine the effects and mechanisms of budesonide on angiogenesis in a murine asthma model.
Material and methods
Murine asthma models were established and mice were divided into three groups: the model group (OVA-sensitized and challenged mice), the BUD group (budesonide-treated mice) and the PBS group (normal control mice). Mice in the BUD group were administered with inhaled budesonide (100 µg/kg) daily. The effects on airway inflammation, angiogenesis, expression of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) were examined.
Results
Administration of budesonide ameliorated allergic airway inflammation (2.90 ±0.18 vs. 4.80 ±0.20, p < 0.01) and significantly reduced the percentage vascularity (0.78 ±0.14 vs. 2.83 ±0.90, p < 0.01) compared with those in the asthmatic model mice. It also reduced the expression of HIF-1α (immunohistochemistry results: 71.70 ±1.40 vs. 89.60 ±0.79, p < 0.001; western blotting results: 0.88 ±0.41 vs. 0.97 ±0.47, p < 0.05), as well as that of VEGF (immunohistochemistry results: 26.30 ±1.03 vs. 93.30 ±1.54, p < 0.001; western blotting results: 1.12 ±0.22 vs. 2.08 ±0.30, p < 0.01). Percentage vascularity had positive correlation with both HIF-1α (r = 0.785, p < 0.01) and VEGF (r = 0.693, p < 0.01) expression. Furthermore, there is positive relationship between HIF-1α and VEGF expression (r = 0.641, p < 0.05).
Conclusions
The results demonstrate that budesonide has an important inhibitory effect on angiogenesis in asthma. Inhaled administration of budesonide achieved anti-angiogenic activity through inhibition of HIF-1α and VEGF expression. The results support a potential anti-remodeling role for budesonide in the treatment of human asthma.
doi:10.5114/aoms.2013.33194
PMCID: PMC3648823  PMID: 23671450
angiogenesis; budesonide; asthma; hypoxia inducible factor-1α; vascular endothelial growth factor
15.  Vascular endothelial growth factor-B gene transfer exacerbates retinal and choroidal neovascularization and vasopermeability without promoting inflammation 
Molecular Vision  2011;17:492-507.
Purpose
The role of vascular endothelial growth factor (VEGF)-B in the eye is poorly understood. The present study was conducted to evaluate the effect of overexpression of VEGF-B via adeno-associated virus (AAV) gene transfer on ocular angiogenesis, inflammation, and the blood-retinal barrier (BRB).
Methods
Three recombinant AAV vectors were prepared, expressing the 167 (AAV-VEGF-B167) or 186 amino acid isoform (AAV-VEGF-B186) of VEGF-B or the green fluorescent protein (GFP) reporter gene (AAV-GFP). Approximately 1×109 viral genome copies of AAV-VEGF-B167, AAV-VEGF-B186, or AAV-GFP were intraocularly injected. The efficacy of the gene transfer was assessed by directly observing GFP, by immunohistochemistry, or by real-time PCR. A leukostasis assay using fluorescein isothiocyanate-conjugated Concanavalin A was used to evaluate inflammation. The BRB was assessed using a quantitative assay with 3H-mannitol as a tracer. Retinal neovascularization (NV) was assessed at postnatal day 17 in oxygen-induced ischemic retinopathy after intravitreal injection of AAV-VEGF-B in left eyes and AAV-GFP in right eyes at postnatal day 7. Two weeks after injection of AAV vectors, choroidal NV was generated by laser photocoagulation and assessed 2 weeks later.
Results
GFP expression was clearly demonstrated, primarily in the retinal pigment epithelium (RPE) and outer retina, 1–6 weeks after delivery. mRNA expression levels of VEGF-B167 and VEGF-B186 were 5.8 and 12 fold higher in the AAV-VEGF-B167- and AAV-VEGF-B186-treated groups, respectively. There was no evidence of an inflammatory response or vessel abnormality following injection of the vectors in normal mice; however, VEGF-B increased retinal and choroidal neovascularization. AAV-VEGF-B186, but not AAV-VEGF-B167, enhanced retinal vascular permeability.
Conclusions
VEGF-B overexpression promoted pathological retinal and choroidal NV and BRB breakdown without causing inflammation, which is associated with the progression of diabetic retinopathy and age-related macular degeneration, showing that these complications are not dependent on inflammation. VEGF-B targeting could benefit antiangiogenic therapy.
PMCID: PMC3042363  PMID: 21364963
16.  Production of Vascular Endothelial Growth Factors from Human Lung Macrophages Induced by Group IIA and Group X Secreted Phospholipases A2 
Angiogenesis and lymphangiogenesis mediated by vascular endothelial growth factors (VEGFs) are main features of chronic inflammation and tumors. Secreted phospholipases A2 (sPLA2s) are overexpressed in inflammatory lung diseases and cancer and they activate inflammatory cells by enzymatic and receptor-mediated mechanisms. We investigated the effect of sPLA2s on the production of VEGFs from human macrophages purified from the lung tissue of patients undergoing thoracic surgery. Primary macrophages express VEGF-A, VEGF-B, VEGF-C, and VEGF-D at both mRNA and protein level. Two human sPLA2s (group IIA and group X) induced the expression and release of VEGF-A and VEGF-C from macrophages. Enzymatically-inactive sPLA2s were as effective as the active enzymes in inducing VEGF production. Me-Indoxam and RO092906A, two compounds that block receptor-mediated effects of sPLA2s, inhibited group X-induced release of VEGF-A. Inhibition of the MAPK p38 by SB203580 also reduced sPLA2-induced release of VEGF-A. Supernatants of group X-activated macrophages induced an angiogenic response in chorioallantoic membranes that was inhibited by Me-Indoxam. Stimulation of macrophages with group X sPLA2 in the presence of adenosine analogs induced a synergistic increase of VEGF-A release and inhibited TNF-α production through a cooperation between A2A and A3 receptors. These results demonstrate that sPLA2s induce production of VEGF-A and VEGF-C in human macrophages by a receptor-mediated mechanism independent from sPLA2 catalytic activity. Thus, sPLA2s may play an important role in inflammatory and/or neoplastic angiogenesis and lymphangiogenesis.
doi:10.4049/jimmunol.0902501
PMCID: PMC3073479  PMID: 20357262
17.  Enhanced expression of genes involved in coagulation and fibrinolysis in murine arthritis 
Arthritis Research  2000;2(6):504-512.
We have analyzed the pattern of procoagulant and fibrinolytic gene expression in affected joints during the course of arthritis in two murine models. In both models, we found an increased expression of tissue factor, tissue factor pathway inhibitor, urokinase plasminogen activator, and plasminogen activator inhibitor 1, as well as thrombin receptor. The observed pattern of gene expression tended to favor procoagulant activity, and this pattern was confirmed by functional assays. These alterations would account for persistence of fibrin within the inflamed joint, as is seen in rheumatoid arthritis.
Introduction:
Accumulation of fibrin in the joints remains one of the most striking histopathological features of rheumatoid arthritis (RA). Recently, we have provided evidence of the deleterious role of synovial fibrin deposition in arthritic joints in antigen-induced arthritis (AIA), a well-established murine model of RA.
A local imbalance between fibrin formation and fibrin dissolution may result in fibrin deposition in the joints.
On the one hand, fibrin formation is mainly initiated by tissue factor (TF), a transmembrane protein serving as a receptor for factor VII. Under normal conditions, TF expression and activity are tightly regulated. Constitutive TF expression is restricted to perivascular and epithelial cells, and the catalytic activity of the TF/VIIa complex can be inhibited by tissue factor pathway inhibitor (TFPI). Pathological conditions can perturb the cell-type-restricted pattern of TF expression. In particular, recent reports have shown that transcriptional activation of TF can be mediated by molecular mechanisms involving induction of the early growth response gene 1 (EGR1) or of the protease-activated receptor (PAR1) or vascular endothelial growth factor (VEGF) genes.
On the other hand, fibrin degradation is mediated primarily by plasmin, which is the active form of the zymogen plasminogen. Conversion of plasminogen to plasmin is under the control of serine protease plasminogen activators, such as the urokinase plasminogen activator (uPA), and their inhibitors, such as the plasminogen activator inhibitor (PAI-1).
Aims:
We hypothesized that the deposition of fibrin in the joints may result from an imbalance in the local expression of key genes involved in coagulation and fibrinolytic pathways. To test this hypothesis, we investigated mRNA levels in arthritic versus nonarthritic joint tissues from two murine models of RA: AIA and collagen-induced arthritis (CIA). Genes that are directly implicated in coagulation (TF, TFPI) and fibrinolysis (UPA, PAI1), and other genes that may influence the expression of TF (EGR1, PAR1, VEGF), were investigated using a novel multiprobe RNase protection assay (RPA). Furthermore, we evaluated coagulation activity in arthritic and nonarthritic mice.
Methods:
Mice with AIA or CIA were sacrificed at different time points: 2, 4, and 16 h and 3, 7, and 14 d after intra-articular antigen injection for AIA; 42 d after the first immunization for CIA. Total RNA was prepared from arthritic and nonarthritic knees for AIA, or arthritic and nonarthritic hind paws for CIA. Messenger RNA (mRNA) levels of the genes described above were determined by RPA and normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels. Coagulation assays were performed on joint tissue extracts and concentrations of thrombin-antithrombin III (TAT) complex were measured in plasma.
Results:
In AIA, all the genes studied except VEGF were upmodulated as early as 2 h. PAR1, TFPI, EGR1, and UPA expression decreased to control levels by 16 h, whereas the expression of TF and PAI1 remained elevated. At later times, only TF, PAI1, and UPA showed sustained overexpression. In CIA, gene expression was assayed at only one time point (42 d after immunization) and all genes showed higher mRNA levels in the affected paws than in control paws. In AIA mice, procoagulant activity and TF activity were significantly increased in arthritic joints, and in CIA mice, plasma TAT levels were significantly enhanced.
Discussion:
Fibrin deposition in synovia is prominent in both RA and experimental arthritis, suggesting that this protein may play a role in the pathogenesis of chronic inflammation. In this study, we have tried to shed some light on the molecular mechanisms leading to extravascular fibrin deposition, using two well-established mouse models of RA: AIA and CIA. The kinetics of gene expression was first analyzed in mice with AIA, because this model allows for an accurate, temporally controlled sampling of synovial inflammation. We then extended our observations by analyzing one time point in CIA, 42 d after immunization, when chronic inflammation is present. We found that in both models, coagulation and fibrinolysis in arthritic joints were significantly increased, and that the most significant increases were in TF and PAI-1.
Although the molecular mechanism or mechanisms responsible for the transcriptional changes observed are not completely understood, the increases in TF, PAI-1, and uPA are probably due to the production of proinflammatory cytokines such as IL-1 and TGF-α. These cytokines, whose presence in the inflamed synovium is well documented, are known to induce these genes through the activation of nuclear factor κB (NF-κB), a transcription factor. TF induction is also under the control of a proximal enhancer containing a binding site for the inducible transcription factor EGR1. Indeed, the early rise of EGR1 expression in AIA is consistent with its classification as immediate-early gene and may be responsible for the induction of early expression of TF. Early TF stimulation in AIA can also be accounted for by the transient overexpression of PAR1. Contrary to what has been shown in RA, VEGF expression remained essentially unchanged throughout the progression of AIA, probably reflecting a peculiarity of this murine model.
The alteration of the patterns of gene expression was accompanied by increased functional coagulation activity, which was more marked in AIA than in CIA.
Conclusion:
Prominent fibrin deposition in two different animal models of RA – AIA and CIA – can be attributed to modulations in key regulatory genes for coagulation and fibrinolysis.
PMCID: PMC17822  PMID: 11056680
arthritis; coagulation; fibrinolysis; mice; RNase protection
18.  The role of AMP-activated protein kinase in the functional effects of vascular endothelial growth factor-A and -B in human aortic endothelial cells 
Vascular Cell  2011;3:9.
Background
Vascular endothelial growth factors (VEGFs) are key regulators of endothelial cell function and angiogenesis. We and others have previously demonstrated that VEGF-A stimulates AMP-activated protein kinase (AMPK) in cultured endothelial cells. Furthermore, AMPK has been reported to regulate VEGF-mediated angiogenesis. The role of AMPK in the function of VEGF-B remains undetermined, as does the role of AMPK in VEGF-stimulated endothelial cell proliferation, a critical process in angiogenesis.
Methods
Human aortic endothelial cells (HAECs) were incubated with VEGF-A and VEGF-B prior to examination of HAEC AMPK activity, proliferation, migration, fatty acid oxidation and fatty acid transport. The role of AMPK in the functional effects of VEGF-A and/or VEGF-B was assessed after downregulation of AMPK activity with chemical inhibitors or infection with adenoviruses expressing a dominant negative mutant AMPK.
Results
Incubation of HAECs with VEGF-B rapidly stimulated AMPK activity in a manner sensitive to an inhibitor of Ca2+/calmodulin-dependent kinase kinase (CaMKK), without increasing phosphorylation of endothelial NO synthase (eNOS) phosphorylation at Ser1177. Downregulation of AMPK abrogated HAEC proliferation in response to VEGF-A or VEGF-B. However, activation of AMPK by agents other than VEGF inhibited proliferation. Downregulation of AMPK abrogated VEGF-A-stimulated HAEC migration, whereas infection with adenoviruses expressing constitutively active mutant AMPK stimulated chemokinesis. Neither VEGF-A nor VEGF-B had any significant effect on HAEC fatty acid oxidation, yet prolonged incubation with VEGF-A stimulated fatty acid uptake in an AMPK-dependent manner. Inhibition of eNOS abrogated VEGF-mediated proliferation and migration, but was without effect on VEGF-stimulated fatty acid transport, ERK or Akt phosphorylation.
Conclusions
These data suggest that VEGF-B stimulates AMPK by a CaMKK-dependent mechanism and stimulation of AMPK activity is required for proliferation in response to either VEGF-A or VEGF-B and migration in response to VEGF-A. AMPK activation alone was not sufficient, however, to stimulate proliferation in the absence of VEGF. VEGF-stimulated NO synthesis is required for the stimulation of proliferation by VEGF-A or VEGF-B, yet this may be independent of eNOS Ser1177 phosphorylation.
doi:10.1186/2045-824X-3-9
PMCID: PMC3094250  PMID: 21507243
19.  VEGF blockade inhibits lymphocyte recruitment and ameliorates immune-mediated vascular remodeling 
Circulation research  2010;107(3):408-417.
Rationale
There are conflicting data on the effects of vascular endothelial growth factor (VEGF) in vascular remodeling. Furthermore, there are species-specific differences in leukocyte and vascular cell biology and little is known about the role of VEGF in remodeling of human arteries.
Objective
We sought to address the role of VEGF blockade on remodeling of human arteries in vivo.
Methods and Results
We used an anti-VEGF antibody, bevacizumab, to study the effect of VEGF blockade on remodeling of human coronary artery transplants in severe combined immunodeficient mice. Bevacizumab ameliorated peripheral blood mononuclear cell (PBMC)-, but not interferon-γ-, induced neointimal formation. This inhibitory effect was associated with a reduction in graft T cell accumulation without affecting T cell activation. VEGF enhanced T cell capture by activated endothelium under flow conditions. The VEGF effect could be recapitulated when a combination of recombinant ICAM-1 and VCAM-1, rather than endothelial cells, was used to capture T cells. A subpopulation of CD3+ T cells expressed VEGF receptor (VEGFR)-1 by immunostaining and FACS analysis. VEGFR-1 mRNA was also detectable in purified CD4+ T cells and Jurkat and HSB-2 T cell lines. Stimulation of HSB-2 and T cells with VEGF triggered downstream ERK phosphorylation, demonstrating the functionality of VEGFR-1 in human T cells.
Conclusions
VEGF contributes to vascular remodeling in human arteries through a direct effect on human T cells that enhances their recruitment to the vessel. These findings raise the possibility of novel therapeutic approaches to vascular remodeling based on inhibition of VEGF signaling.
doi:10.1161/CIRCRESAHA.109.210963
PMCID: PMC2929975  PMID: 20538685
Vascular endothelial growth factor; Bevacizumab; Vascular remodeling; Transplantation; T lymphocytes
20.  Angiotensin II Evokes Angiogenic Signals within Skeletal Muscle through Co-ordinated Effects on Skeletal Myocytes and Endothelial Cells 
PLoS ONE  2014;9(1):e85537.
Skeletal muscle overload induces the expression of angiogenic factors such as vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP)-2, leading to new capillary growth. We found that the overload-induced increase in angiogenesis, as well as increases in VEGF, MMP-2 and MT1-MMP transcripts were abrogated in muscle VEGF KO mice, highlighting the critical role of myocyte-derived VEGF in controlling this process. The upstream mediators that contribute to overload-induced expression of VEGF have yet to be ascertained. We found that muscle overload increased angiotensinogen expression, a precursor of angiotensin (Ang) II, and that Ang II signaling played an important role in basal VEGF production in C2C12 cells. Furthermore, matrix-bound VEGF released from myoblasts induced the activation of endothelial cells, as evidenced by elevated endothelial cell phospho-p38 levels. We also found that exogenous Ang II elevates VEGF expression, as well as MMP-2 transcript levels in C2C12 myotubes. Interestingly, these responses also were observed in skeletal muscle endothelial cells in response to Ang II treatment, indicating that these cells also can respond directly to the stimulus. The involvement of Ang II in muscle overload-induced angiogenesis was assessed. We found that blockade of AT1R-dependent Ang II signaling using losartan did not attenuate capillary growth. Surprisingly, increased levels of VEGF protein were detected in overloaded muscle from losartan-treated rats. Similarly, we observed elevated VEGF production in cultured endothelial cells treated with losartan alone or in combination with Ang II. These studies conclusively establish the requirement for muscle derived VEGF in overload-induced angiogenesis and highlight a role for Ang II in basal VEGF production in skeletal muscle. However, while Ang II signaling is activated following overload and plays a role in muscle VEGF production, inhibition of this pathway is not sufficient to halt overload-induced angiogenesis, indicating that AT1-independent signals maintain VEGF production in losartan-treated muscle.
doi:10.1371/journal.pone.0085537
PMCID: PMC3887063  PMID: 24416421
21.  Paxillin Is Involved in the Differential Regulation of Endothelial Barrier by HGF and VEGF 
Circulating levels of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) are increased during acute lung injury; however, combined effects of HGF and VEGF on pulmonary endothelial cell (EC) permeability remain to be elucidated. We have previously shown differential remodeling of focal adhesions (FA) caused by barrier-protective and barrier-disruptive mechanical and chemical stimuli. This study examined a role of FA protein paxillin in the pulmonary EC barrier responses induced by HGF and VEGF. VEGF increased, but HGF decreased, pulmonary EC permeability. These effects were accompanied by differential patterns of site-specific phosphorylation of focal adhesion kinase (FAK) and paxillin and FA redistribution. HGF antagonized random FA formation caused by VEGF challenge and promoted FA accumulation at the cell periphery. HGF attenuated VEGF-induced paxillin redistribution, FA remodeling, and endothelial permeability. SiRNA-based paxillin knockdown attenuated VEGF-induced EC permeability, myosin light chain phosphorylation, and stress fiber and paracellular gap formation. Paxillin knockdown also decreased HGF-induced EC barrier enhancement and suppressed activation of Rac and its effector PAK1. Expression of paxillin-S273 deficient on PAK1 phosphorylation site prevented HGF-induced cytoskeletal remodeling. These data show a dual role of paxillin in the HGF- and VEGF-mediated endothelial barrier regulation and suggest essential paxillin role in the modulation of Rac-Rho crosstalk. Our results also support a model of pulmonary EC barrier recovery during resolution of ALI via switch from VEGF to HGF signaling.
doi:10.1165/rcmb.2008-0099OC
PMCID: PMC2606951  PMID: 18664639
paxillin; small GTPase; pulmonary endothelium; permeability; growth factors
22.  Computational Model of Vascular Endothelial Growth Factor Spatial Distribution in Muscle and Pro-Angiogenic Cell Therapy 
PLoS Computational Biology  2006;2(9):e127.
Members of the vascular endothelial growth factor (VEGF) family of proteins are critical regulators of angiogenesis. VEGF concentration gradients are important for activation and chemotactic guidance of capillary sprouting, but measurement of these gradients in vivo is not currently possible. We have constructed a biophysically and molecularly detailed computational model to study microenvironmental transport of two isoforms of VEGF in rat extensor digitorum longus skeletal muscle under in vivo conditions. Using parameters based on experimental measurements, the model includes: VEGF secretion from muscle fibers; binding to the extracellular matrix; binding to and activation of endothelial cell surface VEGF receptors; and internalization. For 2-D cross sections of tissue, we analyzed predicted VEGF distributions, gradients, and receptor binding. Significant VEGF gradients (up to 12% change in VEGF concentration over 10 μm) were predicted in resting skeletal muscle with uniform VEGF secretion, due to non-uniform capillary distribution. These relative VEGF gradients were not sensitive to extracellular matrix composition, or to the overall VEGF expression level, but were dependent on VEGF receptor density and affinity, and internalization rate parameters. VEGF upregulation in a subset of fibers increased VEGF gradients, simulating transplantation of pro-angiogenic myoblasts, a possible therapy for ischemic diseases. The number and relative position of overexpressing fibers determined the VEGF gradients and distribution of VEGF receptor activation. With total VEGF expression level in the tissue unchanged, concentrating overexpression into a small number of adjacent fibers can increase the number of capillaries activated. The VEGF concentration gradients predicted for resting muscle (average 3% VEGF/10 μm) is sufficient for cellular sensing; the tip cell of a vessel sprout is approximately 50 μm long. The VEGF gradients also result in heterogeneity in the activation of blood vessel VEGF receptors. This first model of VEGF tissue transport and heterogeneity provides a platform for the design and evaluation of therapeutic approaches.
Synopsis
It is not currently possible to experimentally quantify the gradients of protein concentration in the extracellular space in vivo. However, the concentration gradients of vascular endothelial growth factor (VEGF) are essential for both initiation and directed guidance of new blood vessels. The authors develop a computational model of VEGF transport in tissue in vivo (skeletal muscle, though the method is applicable to other tissues and other proteins) with realistic geometry and including biophysical interactions of VEGF, its receptors, and the extracellular matrix. Using this model, the authors predict for the first time the distribution of VEGF concentration and VEGF receptor activation throughout the tissue. VEGF concentration gradients are significant, up to 12% change in VEGF concentration over 10 μm in resting muscle. Transplanting VEGF-overexpressing myocytes (for therapeutic induction of blood vessel growth) increases the gradients significantly. Endothelial cells in sprouting vessels are approximately 50 μm long, and therefore the predicted gradients across the cell are high and sufficient for chemotactic guidance of the new vessels. The VEGF concentration gradients also result in significant heterogeneity in the activation of VEGF receptors on blood vessels throughout the tissue, a possible reason for the sporadic nature of sprout initiation.
doi:10.1371/journal.pcbi.0020127
PMCID: PMC1570371  PMID: 17002494
23.  Vascular Endothelial Growth Factor Is a Key Mediator in the Development of T Cell Priming and Its Polarization to Type 1 and Type 17 T Helper Cells in the Airways 
Chronic inflammatory airway diseases including asthma are characterized by immune dysfunction to inhaled allergens. Our previous studies demonstrated that T cell priming to inhaled allergens requires LPS, which is ubiquitously present in household dust allergens. In this study, we evaluated the role of vascular endothelial growth factor (VEGF) in the development of T cell priming and its polarization to Th1 or Th17 cells when exposed to LPS-contaminated allergens. An asthma mouse model was induced by airway sensitization with LPS-contaminated allergens and then challenged with allergens alone. Therapeutic intervention was performed during allergen sensitization. The present study showed that lung inflammation induced by sensitization with LPS-contaminated allergens was decreased in mice with homozygous disruption of the IL-17 gene; in addition, allergen-specific Th17 immune response was abolished in IL-6 knockout mice. Meanwhile, in vivo production of VEGF was up-regulated by airway exposure of LPS. In addition, airway sensitization of allergen plus recombinant VEGF induced both type 1 and type 17 Th cell (Th1 and Th17) responses. Th1 and Th17 responses induced by airway sensitization with LPS-contaminated allergens were blocked by treatment with a pan-VEGF receptor (VEGFR; VEGFR-1 plus VEGFR-2) inhibitor during sensitization. These effects were accompanied by inhibition of the production of Th1 and Th17 polarizing cytokines, IL-12p70 and IL-6, respectively. These findings indicate that VEGF produced by LPS plays a key role in activation of naive T cells and subsequent polarization to Th1 and Th17 cells.
doi:10.4049/jimmunol.0901566
PMCID: PMC3385973  PMID: 19786548
24.  Vascular Endothelial Growth Factor Mediates Intracrine Survival in Human Breast Carcinoma Cells through Internally Expressed VEGFR1/FLT1 
PLoS Medicine  2007;4(6):e186.
Background
While vascular endothelial growth factor (VEGF) expression in breast tumors has been correlated with a poor outcome in the pathogenesis of breast cancer, the expression, localization, and function of VEGF receptors VEGFR1 (also known as FLT1) and VEGFR2 (also known as KDR or FLK1), as well as neuropilin 1 (NRP1), in breast cancer are controversial.
Methods and Findings
We investigated the expression and function of VEGF and VEGF receptors in breast cancer cells. We observed that VEGFR1 expression was abundant, VEGFR2 expression was low, and NRP1 expression was variable. MDA-MB-231 and MCF-7 breast cancer cells, transfected with antisense VEGF cDNA or with siVEGF (VEGF-targeted small interfering RNA), showed a significant reduction in VEGF expression and increased apoptosis as compared to the control cells. Additionally, specifically targeted knockdown of VEGFR1 expression by siRNA (siVEGFR1) significantly decreased the survival of breast cancer cells through down-regulation of protein kinase B (AKT) phosphorylation, while targeted knockdown of VEGFR2 or NRP1 expression had no effect on the survival of these cancer cells. Since a VEGFR1-specific ligand, placenta growth factor (PGF), did not, as expected, inhibit the breast cancer cell apoptosis induced by siVEGF, and since VEGFR1 antibody also had no effects on the survival of these cells, we examined VEGFR1 localization. VEGFR1 was predominantly expressed internally in MDA-MB-231 and MCF-7 breast cancer cells. Specifically, VEGFR1 was found to be colocalized with lamin A/C and was expressed mainly in the nuclear envelope in breast cancer cell lines and primary breast cancer tumors. Breast cancer cells treated with siVEGFR1 showed significantly decreased VEGFR1 expression levels and a lack of VEGFR1 expression in the nuclear envelope.
Conclusions
This study provides, to our knowledge for the first time, evidence of a unique survival system in breast cancer cells by which VEGF can act as an internal autocrine (intracrine) survival factor through its binding to VEGFR1. These results may lead to an improved strategy for tumor therapy based on the inhibition of angiogenesis.
Shalom Avraham and colleagues' study provides evidence of a survival system in breast cancer cells by which VEGF acts as an internal autocrine survival factor through its binding to VEGFR1.
Editors' Summary
Background.
One woman in eight will develop breast cancer during her lifetime. Most of these women live for many years after their diagnosis and many are cured of their cancer. However, sometimes the cancer grows inexorably and spreads (metastasizes) around the body despite the efforts of oncologists. Characteristics of the tumor known as prognostic factors can indicate whether this spreading is likely to happen. Large tumors that have metastasized have a poorer prognosis than small tumors that are confined to the breast. The expression of specific proteins within the tumor also provides prognostic information. One protein whose expression is associated with a poor prognosis is vascular endothelial growth factor (VEGF). VEGF stimulates angiogenesis—the growth of new blood vessels. Small tumors get the nutrients needed for their growth from existing blood vessels but large tumors need to organize their own blood supply. They do this, in part, by secreting VEGF. This compound binds to proteins (receptors) on the surface of endothelial cells (the cells lining blood vessels), which then send a signal into the cell instructing it to make new blood vessels. Angiogenesis inhibitors, including molecules that block the activity of VEGF receptors, are being developed for the treatment of cancer.
Why Was This Study Done?
Some breast cancer cell lines (cells isolated from breast cancers and grown in the laboratory) make VEGF and VEGF receptors (VEGFR1, VEGFR2, and neuropilin 1 [NRP1]). But, although some studies have reported an association between VEGFR1 expression in breast tumors and a poor prognosis, other studies have found no expression of VEGFR1 in breast tumors. Consequently, the role of VEGF receptors in breast cancer is unclear. In this study, the researchers analyzed the expression and function of VEGF and its receptors in breast cancer cells to investigate whether and how VEGF helps these cells to survive.
What Did the Researchers Do and Find?
The researchers first examined the expression of VEGF receptors in several human breast cancer cell lines. All of them expressed VEGFR1, some expressed NRP1, but VEGFR2 expression was universally low. They then investigated the function of VEGF and its receptors in two human breast cancer cell lines (MDA-MB-231 and MCF-7). In both cell lines, blocking the expression of VEGF or of VEGFR1 (but not of the other two receptors) reduced cell survival by stimulating a specific process of cell death called apoptosis. Unexpectedly, adding VEGF to the cultures did not reverse the effect of blocking VEGF expression, a result that suggests that VEGF and VEGFR1 do not affect breast cancer cell survival by acting at the cell surface. Accordingly, when the researchers examined where VEGFR1 occurs in the cell, they found it on the membranes around the nucleus of the breast cancer cell lines and not on the cell surface; several primary breast tumors and normal breast tissue had the same localization pattern. Finally, the researchers showed that inhibitors of VEGF action that act at the cell surface did not affect the survival of the breast cancer cell lines.
What Do These Findings Mean?
These findings suggest that VEGF helps breast cancer cells to survive in a unique way: by binding to VEGFR1 inside the cell. In other words, whereas VEGF normally acts as a paracrine growth factor (it is released by one cell and affects another cell), in breast cancer cells it might act as an internal autocrine (intracrine) survival factor, a factor that affects the cells in which it is produced. These findings need confirming in more cell lines and in primary breast cancers but could have important implications for the treatment of breast cancer. Inhibitors of VEGF and VEGFR1 that act inside the cell (small molecule drugs) might block breast cancer growth more effectively than inhibitors that act at the cell surface (for example, proteins that bind to the receptor), because internally acting inhibitors might both kill the tumor directly and have antiangiogenic effects, whereas externally acting inhibitors could only have the second effect.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040186.
US National Cancer Institute information for patients and professionals on breast cancer (in English and Spanish) and on angiogenesis (in English and Spanish)
MedlinePlus Encyclopedia information for patients on breast cancer (in English and Spanish)
CancerQuest, information from Emory University on cancer biology and on angiogenesis and angiogenesis inhibitors (in several languages)
Wikipedia pages on VEGF (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
doi:10.1371/journal.pmed.0040186
PMCID: PMC1885450  PMID: 17550303
25.  Developmental Regulation of NO-Mediated VEGF-Induced Effects in the Lung 
Vascular endothelial growth factor (VEGF) is known to have a pivotal role in lung development and in a variety of pathologic conditions in the adult lung. Our earlier studies have shown that NO is a critical mediator of VEGF-induced vascular and extravascular effects in the adult murine lung. As significant differences have been reported in the cytokine responses in the adult versus the neonatal lung, we hypothesized that there may be significant differences in VEGF-induced alterations in the developing as opposed to the mature lung. Furthermore, nitric oxide (NO) mediation of these VEGF-induced effects may be developmentally regulated. Using a novel externally regulatable lung-targeted transgenic murine model, we found that VEGF-induced pulmonary hemorrhage was mediated by NO-dependent mechanisms in adults and newborns. VEGF enhanced surfactant production in adults as well as increased surfactant and lung development in newborns, via an NO-independent mechanism. While the enhanced survival in hyperoxia in the adult was partly NO-dependent, there was enhanced hyperoxia-induced lung injury in the newborn. In addition, human amniotic fluid VEGF levels correlated positively with surfactant phospholipids. Tracheal aspirate VEGF levels had an initial spike, followed by a decline, and then a subsequent rise, in human neonates with an outcome of bronchopulmonary dysplasia or death. Our data show that VEGF can have injurious as well as potentially beneficial developmental effects, of which some are NO dependent, others NO independent. This opens up the possibility of selective manipulation of any VEGF-based intervention using NO inhibitors for maximal potential clinical benefit.
doi:10.1165/rcmb.2007-0024OC
PMCID: PMC2551703  PMID: 18441284
vascular endothelial growth factor; nitric oxide; lung; surfactant

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