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The effect of Metapanax delavayi leaf extract on testosterone‐induced benign prostatic hyperplasia in rats. J Funct Foods 2020. [DOI: 10.1016/j.jff.2020.103797] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Liang XQ, Liang J, Zhao XF, Wang XY, Deng X. Integrated network analysis of transcriptomic and protein-protein interaction data in taurine-treated hepatic stellate cells. World J Gastroenterol 2019; 25:1067-1079. [PMID: 30862995 PMCID: PMC6406182 DOI: 10.3748/wjg.v25.i9.1067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 01/24/2019] [Accepted: 01/26/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Studies show that the antifibrotic mechanism of taurine may involve its inhibition of the activation and proliferation of hepatic stellate cells (HSCs). Since the molecular mechanism of taurine-mediated antifibrotic activity has not been fully unveiled and is little studied, it is imperative to use “omics” methods to systematically investigate the molecular mechanism by which taurine inhibits liver fibrosis.
AIM To establish a network including transcriptomic and protein-protein interaction data to elucidate the molecular mechanism of taurine-induced HSC apoptosis.
METHODS We used microarrays, bioinformatics, protein-protein interaction (PPI) network, and sub-modules to investigate taurine-induced changes in gene expression in human HSCs (LX-2). Subsequently, all of the differentially expressed genes (DEGs) were subjected to gene ontology function and Kyoto encyclopedia of genes and genomes pathway enrichment analysis. Furthermore, the interactions of DEGs were explored in a human PPI network, and sub-modules of the DEGs interaction network were analyzed using Cytoscape software.
RESULTS A total of 635 DEGs were identified in taurine-treated HSCs when compared with the controls. Of these, 304 genes were statistically significantly up-regulated, and 331 down-regulated. Most of these DEGs were mainly located on the membrane and extracellular region, and are involved in the biological processes of signal transduction, cell proliferation, positive regulation of extracellular regulated protein kinases 1 (ERK1) and ERK2 cascade, extrinsic apoptotic signaling pathway and so on. Fifteen significantly enriched pathways with DEGs were identified, including mitogen-activated protein kinase (MAPK) signaling pathway, peroxisome proliferators-activated receptor signaling pathway, estrogen signaling pathway, Th1 and Th2 cell differentiation, cyclic adenosine monophosphate signaling pathway and so on. By integrating the transcriptomics and human PPI data, nine critical genes, including MMP2, MMP9, MMP21, TIMP3, KLF10, CX3CR1, TGFB1, VEGFB, and EGF, were identified in the PPI network analysis.
CONCLUSION Taurine promotes the apoptosis of HSCs via up-regulating TGFB1 and then activating the p38 MAPK-JNK-Caspase9/8/3 pathway. These findings enhance the understanding of the molecular mechanism of taurine-induced HSC apoptosis and provide references for liver disorder therapy.
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Affiliation(s)
- Xing-Qiu Liang
- Department of Science and Technology, Ruikang Hospital Affiliated to Guangxi University of Chinese Medicine, Nanning 530011, Guangxi Zhuang Autonomous Region, China
| | - Jian Liang
- College of Medical, Guangxi University, Nanning 530004, Guangxi Zhuang Autonomous Region, China
| | - Xiao-Fang Zhao
- Department of Science and Technology, Ruikang Hospital Affiliated to Guangxi University of Chinese Medicine, Nanning 530011, Guangxi Zhuang Autonomous Region, China
| | - Xin-Yuan Wang
- School of Basic Sciences, Guangxi University of Chinese Medicine, Nanning 530200, Guangxi Zhuang Autonomous Region, China
| | - Xin Deng
- School of Basic Sciences, Guangxi University of Chinese Medicine, Nanning 530200, Guangxi Zhuang Autonomous Region, China
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Bruni C, Frech T, Manetti M, Rossi FW, Furst DE, De Paulis A, Rivellese F, Guiducci S, Matucci-Cerinic M, Bellando-Randone S. Vascular Leaking, a Pivotal and Early Pathogenetic Event in Systemic Sclerosis: Should the Door Be Closed? Front Immunol 2018; 9:2045. [PMID: 30245695 PMCID: PMC6137210 DOI: 10.3389/fimmu.2018.02045] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 08/20/2018] [Indexed: 02/06/2023] Open
Abstract
The early phase of systemic sclerosis (SSc) presents edema as one of the main features: this is clinically evident in the digital swelling (puffy fingers) as well as in the edematous skin infiltration of the early active diffuse subset. Other organs could be affected by this same disease process, such as the lung (with the appearance of ground glass opacities) and the heart (with edematous changes on cardiac magnetic resonance imaging). The genesis of tissue edema is tightly linked to pathological changes in the endothelium: various reports demonstrated the effect of transforming growth factor β, vascular endothelial growth factor and hypoxia-reperfusion damage with reactive oxygen species generation in altering vascular permeability and extravasation, in particular in SSc. This condition has an alteration in the glycocalyx thickness, reducing the protection of the vessel wall and causing non-fibrotic interstitial edema, a marker of vascular leak. Moreover, changes in the junctional adhesion molecule family and other adhesion molecules, such as ICAM and VCAM, are associated with an increased myeloid cells' extravasation in the skin and increased myofibroblasts transformation with further vascular leak and cellular migration. This mini-review examines current knowledge on determinants of vascular leak in SSc, shedding light on the role of vascular protection. This could enhance further studies in the light of drug development for early treatment, suggesting that the control of vascular leakage should be considered in the same way that vasodilation and inflammation reduction, as potential therapeutic targets.
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Affiliation(s)
- Cosimo Bruni
- Division of Rheumatology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Tracy Frech
- Division of Rheumatology, Department of Internal Medicine, Salt Lake Veterans Affair Medical Centre, University of Utah, Salt Lake City, UT, United States
| | - Mirko Manetti
- Section of Anatomy and Histology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Francesca Wanda Rossi
- Department of Translational Medical Sciences, Center for Basic and Clinical Immunology Research (CISI), WAO Center of Excellence, University Federico II, Naples, Italy
| | - Daniel E. Furst
- Division of Rheumatology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Rheumatology, University of Washington, Seattle, WA, United States
| | - Amato De Paulis
- Department of Translational Medical Sciences, Center for Basic and Clinical Immunology Research (CISI), WAO Center of Excellence, University Federico II, Naples, Italy
| | - Felice Rivellese
- Department of Translational Medical Sciences, Center for Basic and Clinical Immunology Research (CISI), WAO Center of Excellence, University Federico II, Naples, Italy
| | - Serena Guiducci
- Division of Rheumatology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
- Division of Rheumatology and Scleroderma Unit, Department of Geriatric Medicine, Azienda Ospedaliero Universitaria Careggi, Florence, Italy
| | - Marco Matucci-Cerinic
- Division of Rheumatology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
- Division of Rheumatology and Scleroderma Unit, Department of Geriatric Medicine, Azienda Ospedaliero Universitaria Careggi, Florence, Italy
| | - Silvia Bellando-Randone
- Division of Rheumatology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
- Division of Rheumatology and Scleroderma Unit, Department of Geriatric Medicine, Azienda Ospedaliero Universitaria Careggi, Florence, Italy
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Pazos MC, Sequeira G, Bocchicchio S, May M, Abramovich D, Parborell F, Tesone M, Irusta G. PDGFB as a vascular normalization agent in an ovarian cancer model treated with a gamma-secretase inhibitor. J Cell Physiol 2018; 233:5949-5961. [PMID: 29266203 DOI: 10.1002/jcp.26404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 12/12/2017] [Indexed: 12/21/2022]
Abstract
Ovarian cancer is the fifth leading cause of cancer-related deaths in women. In the past 20 years, the canonical types of drugs used to treat ovarian cancer have not been replaced and the survival rates have not changed. These facts show the clear need to find new therapeutic strategies for this illness. Thus, the aim of the present study was to investigate the effect of a gamma-secretase inhibitor (DAPT) in combination with the Platelet-derived growth factor B (PDGFB) on an ovarian cancer xenograft model. To achieve this goal, we analyzed the effect of the administration of DAPT alone and the co-administration of DAPT and recombinant PDGFB on parameters associated with tumor growth and angiogenesis in an orthotopic experimental model of ovarian cancer. We observed that the dose of DAPT used was ineffective to reduce ovarian tumor growth, but showed anticancer activity when co-administered with recombinant PDGFB. The administration of PDGFB alone normalized tumor vasculature by increasing periendothelial coverage and vascular functionality. Interestingly, this effect exerted by PDGFB was also observed in the presence of DAPT. Our findings suggest that PDGFB is able to improve tumor vascularity and allows the anticancer action of DAPT in the tumor. We propose that this therapeutic strategy could be a new tool for ovarian cancer treatment and deserves further studies.
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Affiliation(s)
- Maria C Pazos
- Instituto de Biología y Medicina Experimental (IByME-CONICET), Vuelta de Obligado, Buenos Aires, Argentina
| | - Gonzalo Sequeira
- Instituto de Biología y Medicina Experimental (IByME-CONICET), Vuelta de Obligado, Buenos Aires, Argentina
| | - Sebastian Bocchicchio
- Instituto de Biología y Medicina Experimental (IByME-CONICET), Vuelta de Obligado, Buenos Aires, Argentina
| | - Maria May
- Instituto de Investigaciones Farmacológicas (ININFA-UBA-CONICET), Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Dalhia Abramovich
- Instituto de Biología y Medicina Experimental (IByME-CONICET), Vuelta de Obligado, Buenos Aires, Argentina
| | - Fernanda Parborell
- Instituto de Biología y Medicina Experimental (IByME-CONICET), Vuelta de Obligado, Buenos Aires, Argentina
| | - Marta Tesone
- Instituto de Biología y Medicina Experimental (IByME-CONICET), Vuelta de Obligado, Buenos Aires, Argentina
| | - Griselda Irusta
- Instituto de Biología y Medicina Experimental (IByME-CONICET), Vuelta de Obligado, Buenos Aires, Argentina
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Measurement of Angiogenesis, Arteriolargenesis, and Lymphangiogenesis Phenotypes by Use of Two-Dimensional Mesenteric Angiogenesis Assay. Methods Mol Biol 2017. [PMID: 27172966 DOI: 10.1007/978-1-4939-3628-1_24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Successful therapeutic angiogenesis requires an understanding of how the myriad interactions of growth factors released during angiogenesis combine to form a mature vascular bed. This requires a model in which multiple physiological and cell biological parameters can be identified. The adenoviral-mediated mesenteric angiogenesis assay as described here is ideal for that purpose. The clear, thin, and relatively avascular mesenteric panel can be used to measure increased vessel perfusion by intravital microscopy. In addition, high-powered microvessel analysis is carried out by immunostaining of features essential for the study of angiogenesis or lymphangiogenesis (including endothelium, pericyte, smooth muscle cell area, and proliferation), allowing functional data to be obtained in conjunction with high-power microvessel ultrastructural analysis. Therefore, the mesenteric angiogenesis model offers a robust system to analyze the morphological changes associated with angiogenesis, induced by different agents.
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Guo J, Yan W, Yang Y, Wang Z, Tian F. Monitoring of vascular endothelial growth factor and its soluble receptor levels in early trauma. J Trauma Acute Care Surg 2017; 82:766-770. [PMID: 28099389 DOI: 10.1097/ta.0000000000001373] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND This clinical observation study aimed to investigate the relationship between the serum levels of vascular endothelial growth factor (VEGF) and its soluble receptors with the severity and the occurrence of late acute respiratory distress syndrome (ARDS) in early trauma. METHODS Sixty patients with multiple injuries were divided into three groups according to the Injury Severity Score (ISS) and the serum levels of VEGF, soluble VEGF receptor 1 (sVEGFR1), and sVEGFR2, were measured. Ten healthy people were recruited as controls. The incidence of late ARDS was also monitored, and its relationship to the above measures analyzed. RESULTS VEGF was not associated with ISS (p > 0.05); sVEGFR1 was positively associated with ISS (r = 0.459, p < 0.0001); however, sVEGFR2 was negatively associated with ISS (r = 0.510, p < 0.0001). The serum VEGF levels between the ARDS group and the non-ARDS group showed no significant difference (p > 0.05). sVEGFR1 in the ARDS group was significantly higher than that in the non-ARDS group (p < 0.0001), and sVEGFR2 in the ARDS group was significantly lower than that in the non-ARDS group (p < 0.0001). CONCLUSION In conclusion, the increasing of sVEGFR1 and the decreasing of sVEGFR2 in early trauma might be closely related to the occurrence of late ARDS. LEVEL OF EVIDENCE Prognostic study, level III.
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Affiliation(s)
- Jianying Guo
- From the Department of Critical Care Medicine (J.G., Z.W.), the Third Hospital of Hebei Medical University, Shijiazhuang, China; Department of Intensive Care Unit (W.Y.), the First Hospital of Baoding, Baoding, Hebei, China; Department of Severe Medicine (Y.Y.), Xingtai People's Hospital, Xingtai, Hebei, China; and Department of Respiratory (F.T.), the Third Hospital of Hebei Medical University, Shijiazhuang, China
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Ganta VC, Choi M, Kutateladze A, Annex BH. VEGF165b Modulates Endothelial VEGFR1-STAT3 Signaling Pathway and Angiogenesis in Human and Experimental Peripheral Arterial Disease. Circ Res 2016; 120:282-295. [PMID: 27974423 DOI: 10.1161/circresaha.116.309516] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 11/22/2016] [Accepted: 12/14/2016] [Indexed: 01/25/2023]
Abstract
RATIONALE Atherosclerotic-arterial occlusions decrease tissue perfusion causing ischemia to lower limbs in patients with peripheral arterial disease (PAD). Ischemia in muscle induces an angiogenic response, but the magnitude of this response is frequently inadequate to meet tissue perfusion requirements. Alternate splicing in the exon-8 of vascular endothelial growth factor (VEGF)-A results in production of proangiogenic VEGFxxxa isoforms (VEGF165a, 165 for the 165 amino acid product) and antiangiogenic VEGFxxxb (VEGF165b) isoforms. OBJECTIVE The antiangiogenic VEGFxxxb isoforms are thought to antagonize VEGFxxxa isoforms and decrease activation of VEGF receptor-2 (VEGFR2), hereunto considered the dominant receptor in postnatal angiogenesis in PAD. Our data will show that VEGF165b inhibits VEGFR1 signal transducer and activator of transcription (STAT)-3 signaling to decrease angiogenesis in human and experimental PAD. METHODS AND RESULTS In human PAD versus control muscle biopsies, VEGF165b: (1) is elevated, (2) is bound higher (versus VEGF165a) to VEGFR1 not VEGFR2, and (3) levels correlated with decreased VEGFR1, not VEGFR2, activation. In experimental PAD, delivery of an isoform-specific monoclonal antibody to VEGF165b versus control antibody enhanced perfusion in animal model of severe PAD (Balb/c strain) without activating VEGFR2 signaling but with increased VEGFR1 activation. Receptor pull-down experiments demonstrate that VEGF165b inhibition versus control increased VEGFR1-STAT3 binding and STAT3 activation, independent of Janus-activated kinase-1)/Janus-activated kinase-2. Using VEGFR1+/- mice that could not increase VEGFR1 after ischemia, we confirm that VEGF165b decreases VEGFR1-STAT3 signaling to decrease perfusion. CONCLUSIONS Our results indicate that VEGF165b prevents activation of VEGFR1-STAT3 signaling by VEGF165a and hence inhibits angiogenesis and perfusion recovery in PAD muscle.
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Affiliation(s)
- Vijay Chaitanya Ganta
- From the Cardiovascular Research Center (V.C.G., M.C., B.H.A.), Department of Biology (A.K.), and Department of Cardiovascular Medicine, University of Virginia, Charlottesville (B.H.A.)
| | - Min Choi
- From the Cardiovascular Research Center (V.C.G., M.C., B.H.A.), Department of Biology (A.K.), and Department of Cardiovascular Medicine, University of Virginia, Charlottesville (B.H.A.)
| | - Anna Kutateladze
- From the Cardiovascular Research Center (V.C.G., M.C., B.H.A.), Department of Biology (A.K.), and Department of Cardiovascular Medicine, University of Virginia, Charlottesville (B.H.A.)
| | - Brian H Annex
- From the Cardiovascular Research Center (V.C.G., M.C., B.H.A.), Department of Biology (A.K.), and Department of Cardiovascular Medicine, University of Virginia, Charlottesville (B.H.A.).
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Park-Windhol C, D'Amore PA. Disorders of Vascular Permeability. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2016; 11:251-81. [PMID: 26907525 DOI: 10.1146/annurev-pathol-012615-044506] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The endothelial barrier maintains vascular and tissue homeostasis and modulates many physiological processes, such as angiogenesis. Vascular barrier integrity can be disrupted by a variety of soluble permeability factors, and changes in barrier function can exacerbate tissue damage during disease progression. Understanding endothelial barrier function is critical for vascular homeostasis. Many of the signaling pathways promoting vascular permeability can also be triggered during disease, resulting in prolonged or uncontrolled vascular leak. It is believed that recovery of the normal vasculature requires diminishing this hyperpermeable state. Although the molecular mechanisms governing vascular leak have been studied over the last few decades, recent advances have identified new therapeutic targets that have begun to show preclinical and clinical promise. These approaches have been successfully applied to an increasing number of disease conditions. New perspectives regarding how vascular leak impacts the progression of various diseases are highlighted in this review.
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Affiliation(s)
- Cindy Park-Windhol
- Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, Massachusetts 02114; , .,Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02115
| | - Patricia A D'Amore
- Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, Massachusetts 02114; , .,Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02115.,Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115
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The effects of inflammatory cytokines on lymphatic endothelial barrier function. Angiogenesis 2013; 17:395-406. [PMID: 24141404 DOI: 10.1007/s10456-013-9393-2] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 09/23/2013] [Indexed: 12/22/2022]
Abstract
Proper lymphatic function is necessary for the transport of fluids, macromolecules, antigens and immune cells out of the interstitium. The lymphatic endothelium plays important roles in the modulation of lymphatic contractile activity and lymph transport, but it's role as a barrier between the lymph and interstitial compartments is less well understood. Alterations in lymphatic function have long been associated with edema and inflammation although the integrity of the lymphatic endothelial barrier during inflammation is not well-defined. In this paper we evaluated the integrity of the lymphatic barrier in response to inflammatory stimuli commonly associated with increased blood endothelial permeability. We utilized in vitro assays of lymphatic endothelial cell (LEC) monolayer barrier function after treatment with different inflammatory cytokines and signaling molecules including TNF-α, IL-6, IL-1β, IFN-γ and LPS. Moderate increases in an index of monolayer barrier dysfunction were noted with all treatments (20-60 % increase) except IFN-γ which caused a greater than 2.5-fold increase. Cytokine-induced barrier dysfunction was blocked or reduced by the addition of LNAME, except for IL-1β and LPS treatments, suggesting a regulatory role for nitric oxide. The decreased LEC barrier was associated with modulation of both intercellular adhesion and intracellular cytoskeletal activation. Cytokine treatments reduced the expression of VE-cadherin and increased scavenging of β-catenin in the LECs and this was partially reversed by LNAME. Likewise the phosphorylation of myosin light chain 20 at the regulatory serine 19 site, which accompanied the elevated monolayer barrier dysfunction in response to cytokine treatment, was also blunted by LNAME application. This suggests that the lymphatic barrier is regulated during inflammation and that certain inflammatory signals may induce large increases in permeability.
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A Recombinant Inhibitory Isoform of Vascular Endothelial Growth Factor164/165 Aggravates Ischemic Brain Damage in a Mouse Model of Focal Cerebral Ischemia. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 183:1010-24. [DOI: 10.1016/j.ajpath.2013.06.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 06/03/2013] [Accepted: 06/05/2013] [Indexed: 02/07/2023]
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Li Y, Wang W, Wang JP, Pan L, Zhang Y, Yu HT, Jiang W, Wang PZ, Bai XF. Elevated vascular endothelial growth factor levels induce hyperpermeability of endothelial cells in hantavirus infection. J Int Med Res 2013. [PMID: 23206462 DOI: 10.1177/030006051204000519] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
OBJECTIVE To investigate the role of vascular endothelial growth factor (VEGF) in haemorrhagic fever with renal syndrome (HFRS). METHODS VEGF, soluble VEGF receptor (sVEGFR)-2, angiopoietin (Ang)-1, tumour necrosis factor (TNF)-α and interferon (IFN)-γ levels were measured in serum samples from 68 patients with HFRS. Cultured human umbilical vein endothelial cells (HUEVCs) were infected by Hantaan virus (HTNV) and/or stimulated with recombinant VEGF; dextran permeability of the cells was determined. Claudin-1 and vascular endothelial (VE)-cadherin levels were determined by real-time reverse transcription-polymerase chain reaction and Western blot analyses. RESULTS Serum VEGF, TNF-α and IFN-γ levels were significantly elevated, whereas sVEGFR2 and Ang-1 levels were reduced, during the acute phase of HFRS. In vitro cell permeability was unaffected by HTNV infection or VEGF stimulation alone, but the combination of HTNV infection and VEGF treatment significantly increased the permeability of endothelial cell monolayers in a time-dependent manner. Claudin-1 and VE-cadherin were downregulated at both the mRNA and protein level by combined HTNV infection and VEGF stimulation. CONCLUSIONS Elevated VEGF induced by HTNV infection may play an important role in the vascular hyperpermeability that is characteristic of HFRS.
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Affiliation(s)
- Y Li
- Centre for Infectious Diseases, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
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Beazley-Long N, Hua J, Jehle T, Hulse RP, Dersch R, Lehrling C, Bevan H, Qiu Y, Lagrèze WA, Wynick D, Churchill AJ, Kehoe P, Harper SJ, Bates DO, Donaldson LF. VEGF-A165b is an endogenous neuroprotective splice isoform of vascular endothelial growth factor A in vivo and in vitro. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 183:918-29. [PMID: 23838428 DOI: 10.1016/j.ajpath.2013.05.031] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 05/19/2013] [Accepted: 05/31/2013] [Indexed: 01/13/2023]
Abstract
Vascular endothelial growth factor (VEGF) A is generated as two isoform families by alternative RNA splicing, represented by VEGF-A165a and VEGF-A165b. These isoforms have opposing actions on vascular permeability, angiogenesis, and vasodilatation. The proangiogenic VEGF-A165a isoform is neuroprotective in hippocampal, dorsal root ganglia, and retinal neurons, but its propermeability, vasodilatatory, and angiogenic properties limit its therapeutic usefulness. In contrast, a neuroprotective effect of endogenous VEGF-A165b on neurons would be advantageous for neurodegenerative pathologies. Endogenous expression of human and rat VEGF-A165b was detected in hippocampal and cortical neurons. VEGF-A165b formed a significant proportion of total VEGF-A in rat brain. Recombinant human VEGF-A165b exerted neuroprotective effects in response to multiple insults, including glutamatergic excitotoxicity in hippocampal neurons, chemotherapy-induced cytotoxicity of dorsal root ganglion neurons, and retinal ganglion cells (RGCs) in rat retinal ischemia-reperfusion injury in vivo. Neuroprotection was dependent on VEGFR2 and MEK1/2 activation but not on p38 or phosphatidylinositol 3-kinase activation. Recombinant human VEGF-A165b is a neuroprotective agent that effectively protects both peripheral and central neurons in vivo and in vitro through VEGFR2, MEK1/2, and inhibition of caspase-3 induction. VEGF-A165b may be therapeutically useful for pathologies that involve neuronal damage, including hippocampal neurodegeneration, glaucoma diabetic retinopathy, and peripheral neuropathy. The endogenous nature of VEGF-A165b expression suggests that non-isoform-specific inhibition of VEGF-A (for antiangiogenic reasons) may be damaging to retinal and sensory neurons.
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Affiliation(s)
- Nicholas Beazley-Long
- Microvascular Research Laboratories, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
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Abstract
Anti-angiogenic vascular endothelial growth factor A (VEGF) 165b and pro-angiogenic VEGF 165 are generated from the same transcript, and their relative amounts are dependent on alternative splicing. The role of VEGF 165b has not been investigated in as much detail as VEGF 165, although it appears to be highly expressed in non-angiogenic tissues and, in contrast with VEGF 165, is downregulated in tumors and other pathologies associated with abnormal neovascularization such as diabetic retinopathy or Denys Drash syndrome. VEGF 165b inhibits VEGFR2 signaling by inducing differential phosphorylation, and it can be used to block angiogenesis in in vivo models of tumorigenesis and angiogenesis-related eye disease. Recent reports have identified three serine/arginine-rich proteins, SRSF1, SRSF2 and SRSF6, and studied their role in regulating terminal splice-site selection. Since the balance of VEGF isoforms is lost in cancer and angiogenesis-related conditions, control of VEGF splicing could also be used as a basis for therapy in these diseases.
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Affiliation(s)
- Maria Peiris-Pagès
- Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY, USA
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el Filali M, Ly LV, Luyten GP, Versluis M, Grossniklaus HE, van der Velden PA, Jager MJ. Bevacizumab and intraocular tumors: an intriguing paradox. Mol Vis 2012; 18:2454-67. [PMID: 23077404 PMCID: PMC3472924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 10/03/2012] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Bevacizumab, a humanized monoclonal antibody to vascular endothelial growth factor-A (VEGF-A), was originally developed as an anti-tumor treatment. In ocular oncology, it is being used to treat macular edema due to radiation retinopathy, but it may also be useful for the treatment of primary uveal melanoma (UM) or its metastases. We determined the effect of bevacizumab on the growth of B16F10 cells inside the eye and on B16F10 and UM cells cultured in vitro. METHODS B16F10 melanoma cells were placed into the anterior chamber of the eye of C57Bl/6 mice and tumor growth was monitored after injection of different doses of bevacizumab or mock injection. In addition, the effect of bevacizumab on in vitro growth of B16F10 and human UM cells and on the expression of VEGF-A, GLUT-1, and HIF-1α was evaluated. RESULTS Following intraocular injection of bevacizumab into murine B16 tumor-containing eyes, an acceleration of tumor growth was observed, with the occurrence of anterior chamber hemorrhages. Bevacizumab did not affect proliferation of B16F10 cells in vitro, while it inhibited UM cell proliferation. Expression analysis demonstrated that addition of bevacizumab under hypoxic conditions induced VEGF-A, GLUT-1 and HIF-1α in B16F10 cells as well as in UM cell lines and two of four primary UM tumor cultures. CONCLUSIONS In contrast with expectations, intraocular injection of bevacizumab stimulated B16F10 melanoma growth in murine eyes. In vitro exposure of B16 and human UM cells to bevacizumab led to paradoxical VEGF-A upregulation. The use of VEGF inhibitors for treatment of macular edema (due to radiation retinopathy) after irradiation of UM should be considered carefully, because of the possible adverse effects on residual UM cells.
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Affiliation(s)
| | - Long V. Ly
- Department of Ophthalmology, LUMC, Leiden, the Netherlands
| | | | | | - Hans E. Grossniklaus
- Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA,Department of Pathology, Emory University School of Medicine, Atlanta, GA
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Oltean S, Neal CR, Mavrou A, Patel P, Ahad T, Alsop C, Lee T, Sison K, Qiu Y, Harper SJ, Bates DO, Salmon AHJ. VEGF165b overexpression restores normal glomerular water permeability in VEGF164-overexpressing adult mice. Am J Physiol Renal Physiol 2012; 303:F1026-36. [PMID: 22811490 DOI: 10.1152/ajprenal.00410.2011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Vascular endothelial growth factor (VEGF)-A, a family of differentially spliced proteins produced by glomerular podocytes, maintains glomerular filtration barrier function. The expression of VEGF molecules is altered in human nephropathy. We aimed to determine the roles of the angiogenic VEGF(164) isoform, and the antiangiogenic VEGF(165)b isoform in mature, adult glomeruli in vivo using conditional, inducible transgenic overexpression systems in mice. Podocyte-specific VEGF(164) overexpression (up to 100 days) was induced by oral administration of doxycycline to adult podocin-rtTA/TetO-VEGF(164) double transgenic mice. The consequences of simultaneous overexpression of VEGF(164) and VEGF(165)b were assessed in triple-transgenic podocin-rtTA/TetO-VEGF(164)/nephrin-VEGF(165)b mice. Persistent VEGF(164) overexpression did not cause proteinuria but did increase glomerular ultrafiltration coefficient between days 3 and 7. Despite persistently increased VEGF(164) levels, glomerular ultrafiltration coefficient normalized by day 14 and remained normal up to 100 days. Decreased subpodocyte space (SPS) coverage of the glomerular capillary wall accompanied increased glomerular hydraulic conductivity in VEGF(164)-overexpressing mice. The changes in glomerular ultrafiltration coefficient and SPS coverage induced by 7 days of overexpression of VEGF(164) were not present in triple transgenic VEGF(164) and VEGF(165)b overexpressing mice. These results indicate that 1) the adult mouse glomerulus is relatively resistant to induced VEGF(164) overexpression. VEGF(164) overexpression altered glomerular permeability but did not cause proteinuria in these mature, adult animals; 2) the SPS is a dynamic VEGF-responsive modulator of glomerular function; and 3) the balance of VEGF isoforms plays a critical role in the regulation of glomerular permeability. VEGF(165)b is capable of preventing VEGF(164)-induced changes in glomerular permeability and ultrastructure in vivo.
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Affiliation(s)
- Sebastian Oltean
- Microvascular Research Laboratories, School of Physiology and Pharmacology, Univ. of Bristol, Preclinical Veterinary School, Southwell St., Bristol, United Kingdom. BS2 8EJ
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16
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Abstract
PET (pre-eclamptic toxaemia), characterized by pregnancy-related hypertension and proteinuria, due to widespread endothelial dysfunction, is a primary cause of maternal morbidity. Altered circulating factors, particularly the VEGF (vascular endothelial growth factor) family of proteins and their receptors, are thought to be key contributors to this disease. Plasma from patients with PET induces numerous cellular and physiological changes in endothelial cells, indicating the presence of a circulating imbalance of the normal plasma constituents. These have been narrowed down to macromolecules of the VEGF family of proteins and receptors. It has been shown that responses of endothelial cells in intact vessels to plasma from patients with pre-eclampsia is VEGF-dependent. It has recently been shown that this may be specific to the VEGF₁₆₅b isoform, and blocked by addition of recombinant human PlGF (placental growth factor). Taken together with results that show that sVEGFR1 (soluble VEGF receptor 1) levels are insufficient to bind VEGF-A in human plasma from patients with pre-eclampsia, and that other circulating macromolecules bind, but do not inactivate, VEGF-A, this suggests that novel hypotheses involving altered bioavailability of VEGF isoforms resulting from reduced or bound PlGF, or increased sVEGFR1 increasing biological activity of circulating plasma, could be tested. This suggests that knowing how to alter the balance of VEGF family members could prevent endothelial activation, and potentially some symptoms, of pre-eclampsia.
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Iyer S, Acharya KR. Tying the knot: the cystine signature and molecular-recognition processes of the vascular endothelial growth factor family of angiogenic cytokines. FEBS J 2011; 278:4304-22. [PMID: 21917115 PMCID: PMC3328748 DOI: 10.1111/j.1742-4658.2011.08350.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The cystine-knot motif, made up of three intertwined disulfide bridges, is a unique feature of several toxins, cyclotides and growth factors, and occurs in a variety of species, including fungi, insects, molluscs and mammals. Growth factor molecules containing the cystine-knot motif serve as ligands for a diverse range of receptors and play an important role in extracellular signalling. This superfamily of polypeptides comprises several homodimeric and heterodimeric molecules that are central characters in both health and disease. Amongst these molecules are a group of proteins that belong to the vascular endothelial growth factor (VEGF) subfamily. The members of this family are known angiogenic factors that regulate processes leading to blood vessel formation in physiological and pathological conditions. The focus of the present review is on the structural characteristics of proteins that belong to the VEGF family and on signal-transduction pathways that become initiated via the VEGF receptors.
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Affiliation(s)
- Shalini Iyer
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, UK
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Bills VL, Salmon AH, Harper SJ, Overton TG, Neal CR, Jeffery B, Soothill PW, Bates DO. Impaired vascular permeability regulation caused by the VEGF165b splice variant in pre-eclampsia. BJOG 2011; 118:1253-61. [DOI: 10.1111/j.1471-0528.2011.02925.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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20
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Cromer W, Jennings MH, Odaka Y, Mathis JM, Alexander JS. Murine rVEGF164b, an inhibitory VEGF reduces VEGF-A-dependent endothelial proliferation and barrier dysfunction. Microcirculation 2011; 17:536-47. [PMID: 21040119 DOI: 10.1111/j.1549-8719.2010.00047.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To investigate the effects of the murine inhibitory vascular endothelial growth factor (VEGF, rVEGF164b), we generated an adenoviral vector encoding rVEGF164b, and examined its effects on endothelial barrier, growth, and structure. METHOD Mouse vascular endothelial cells (MVEC) proliferation was determined by an MTT assay. Barrier of MVEC monolayers was measured by trans-endothelial electrical resistance (TEER). Reorganization of actin and zonula occludens-1 (ZO-1) were determined by fluorescent microscopy. RESULTS Mouse venous endothelial cells treated with murine VEGF-A (VEGF-A) (50 ng/mL) increased proliferation (60.7 ± 0.1%) within 24 hours (p < 0.05) and rVEGF164b inhibited VEGF-A-induced proliferation. TEER was significantly decreased by VEGF-A (81.7 ± 6.2% of control). Treatment with rVEGF164b at 50 ng/mL transiently reduced MVEC barrier (p < 0.05) at 30 minutes post-treatment (87.9 ± 1.7% of control TEER), and returned to control levels by 40 minutes post-treatment. Treatment with rVEGF164b prevented barrier changes by subsequent exposure to VEGF-A. Treatment of MVECS with VEGF-A reorganized F-actin and ZO-1, which was attenuated by rVEGF164b. CONCLUSIONS VEGF-A may dysregulate endothelial barrier through junctional cytoskeleton processes, which can be attenuated by rVEGF164b. The VEGF-A stimulated MVEC proliferation, barrier dysregulation, and cytoskeletal rearrangement. However, rVEGF164b blocks these effects, therefore it may be useful for regulation studies of VEGF-A/VEGF-R signaling in many different models.
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Affiliation(s)
- Walter Cromer
- Gene Therapy Program, Department of Cellular Biology and Anatomy, LSU Health Sciences Center, Shreveport, Louisiana 71130-3932, USA
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21
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Catena R, Larzabal L, Larrayoz M, Molina E, Hermida J, Agorreta J, Montes R, Pio R, Montuenga LM, Calvo A. VEGF₁₂₁b and VEGF₁₆₅b are weakly angiogenic isoforms of VEGF-A. Mol Cancer 2010; 9:320. [PMID: 21194429 PMCID: PMC3022671 DOI: 10.1186/1476-4598-9-320] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 12/31/2010] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Different isoforms of VEGF-A (mainly VEGF₁₂₁, VEGF₁₆₅ and VEGF189) have been shown to display particular angiogenic properties in the generation of a functional tumor vasculature. Recently, a novel class of VEGF-A isoforms, designated as VEGF(xxx)b, generated through alternative splicing, have been described. Previous studies have suggested that these isoforms may inhibit angiogenesis. In the present work we have produced recombinant VEGF₁₂₁/₁₆₅b proteins in the yeast Pichia pastoris and constructed vectors to overexpress these isoforms and assess their angiogenic potential. RESULTS Recombinant VEGF₁₂₁/₁₆₅b proteins generated either in yeasts or mammalian cells activated VEGFR2 and its downstream effector ERK1/2, although to a lesser extent than VEGF₁₆₅. Furthermore, treatment of endothelial cells with VEGF₁₂₁/₁₆₅b increased cell proliferation compared to untreated cells, although such stimulation was lower than that induced by VEGF₁₆₅. Moreover, in vivo angiogenesis assays confirmed angiogenesis stimulation by VEGF₁₂₁/₁₆₅b isoforms. A549 and PC-3 cells overexpressing VEGF₁₂₁b or VEGF₁₆₅b (or carrying the PCDNA3.1 empty vector, as control) and xenotransplanted into nude mice showed increased tumor volume and angiogenesis compared to controls. To assess whether the VEGF(xxx)b isoforms are differentially expressed in tumors compared to healthy tissues, immunohistochemical analysis was conducted on a breast cancer tissue microarray. A significant increase (p < 0.05) in both VEGF(xxx)b and total VEGF-A protein expression in infiltrating ductal carcinomas compared to normal breasts was observed. A positive significant correlation (r = 0.404, p = 0.033) between VEGF(xxx)b and total VEGF-A was found. CONCLUSIONS Our results demonstrate that VEGF₁₂₁/₁₆₅b are not anti-angiogenic, but weakly angiogenic isoforms of VEGF-A. In addition, VEGF(xxx)b isoforms are up-regulated in breast cancer in comparison with non malignant breast tissues. These results are to be taken into account when considering a possible use of VEGF₁₂₁/₁₆₅b-based therapies in patients.
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Affiliation(s)
- Raúl Catena
- Laboratory of Novel Therapeutic Targets, Division of Oncology, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain
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22
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Investigation of antiangiogenic tumor therapy potential of microencapsulated HEK293 VEGF165b producing cells. J Biomed Biotechnol 2010; 2010:645610. [PMID: 20976076 PMCID: PMC2957143 DOI: 10.1155/2010/645610] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Accepted: 08/25/2010] [Indexed: 02/07/2023] Open
Abstract
To investigate the antiangiogenic potential of encapsulated VEGF₁₆₅b producing HEK293 cells, Human Embryonic Kidney 293 (HEK293) cells were stably transfected to produce VEGF₁₆₅b. Then they were encapsulated in alginate-polylysine-alginate (APA) microcapsules. VEGF₁₆₅b productivity and viability of encapsulated cells were analyzed and compared with the non-encapsulated cells. Results showed that encapsulated cells proliferated and remained viable within the microcapsules throughout the 28-day period of the experiment. The quantity of VEGF₁₆₅b increased from 6.5 ± 1.2 μg/ml at day 13 to 13 ± 0.96 μg/ml at day 16. Then it gradually dropped to 5 ± 1.2 μg/ml for the last 3 days period as measured at day 28. Production of VEGF₁₆₅b from encapsulated and non-encapsulated cells was similar. The effect of VEGF₁₆₅b harvested from encapsulated cells on Human Umbilical Vein Endothelial cells (HUVECs) proliferation were also examined.The same inhibitory effects on HUVECs proliferation was seen when the cells were incubated with a mixture of VEGF₁₆₅b and a 2-fold VEGF₁₆₅b or with VEGF₁₆₅b and 2-fold excess VEGF₁₆₅b released from encapsulated cells. Subcutaneous injection of microencapsulated VEGF₁₆₅b producing cells in tumor site of nude mice resulted in the reduction of the number of vessels around the tumors.
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23
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Qiu Y, Ferguson J, Oltean S, Neal CR, Kaura A, Bevan H, Wood E, Sage LM, Lanati S, Nowak DG, Salmon AHJ, Bates D, Harper SJ. Overexpression of VEGF165b in podocytes reduces glomerular permeability. J Am Soc Nephrol 2010; 21:1498-509. [PMID: 20688932 DOI: 10.1681/asn.2009060617] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The observation that therapeutic agents targeting vascular endothelial growth factor-A (VEGF-A) associate with renal toxicity suggests that VEGF plays a role in the maintenance of the glomerular filtration barrier. Alternative mRNA splicing produces the VEGF(xxx)b family, which consists of antiangiogenic peptides that reduce permeability and inhibit tumor growth; the contribution of these peptides to normal glomerular function is unknown. Here, we established and characterized heterozygous and homozygous transgenic mice that overexpress VEGF(165)b specifically in podocytes. We confirmed excess production of glomerular VEGF(165)b by reverse transcriptase-PCR, immunohistochemistry, and ELISA in both heterozygous and homozygous animals. Macroscopically, the mice seemed normal up to 18 months of age, unlike the phenotype of transgenic podocyte-specific VEGF(164)-overexpressing mice. Animals overexpressing VEGF(165)b, however, had a significantly reduced normalized glomerular ultrafiltration fraction with accompanying changes in ultrastructure of the glomerular filtration barrier on the vascular side of the glomerular basement membrane. These data highlight the contrasting properties of VEGF splice variants and their impact on glomerular function and phenotype.
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Affiliation(s)
- Yan Qiu
- Microvascular Research Laboratories, Department Physiology and Pharmacology, Bristol Heart Institute, Preclinical Veterinary School, Southwell Street, Bristol, BS2 8EJ, UK
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24
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Abstract
Vascular endothelial growth factors (VEGFs) are key regulators of permeability. The principal evidence behind how they increase vascular permeability in vivo and in vitro and the consequences of that increase are addressed here. Detailed analysis of the published literature has shown that in vivo and in vitro VEGF-mediated permeability differs in its time course, but has common involvement of many specific signalling pathways, in particular VEGF receptor-2 activation, calcium influx through transient receptor potential channels, activation of phospholipase C gamma and downstream activation of nitric oxide synthase. Pathways downstream of endothelial nitric oxide synthase appear to involve the guanylyl cyclase-mediated activation of the Rho–Rac pathway and subsequent involvement of junctional signalling proteins such as vascular endothelial cadherin and the tight junctional proteins zona occludens and occludin linked to the actin cytoskeleton. The signalling appears to be co-ordinated through spatial organization of the cascade into a signalplex, and arguments for why this may be important are considered. Many proteins have been identified to be involved in the regulation of vascular permeability by VEGF, but still the mechanisms through which these are thought to interact to control permeability are dependent on the experimental system, and a synthesis of existing data reveals that in intact vessels the co-ordination of the pathways is still not understood.
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Affiliation(s)
- David O Bates
- Microvascular Research Laboratories, Department of Physiology and Pharmacology, School of Veterinary Sciences, Bristol Heart Institute, University of Bristol, Southwell Street, Bristol, UK.
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25
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Hypoxia inducible factor-1α (HIF-1α) and some HIF-1 target genes are elevated in experimental glaucoma. J Mol Neurosci 2010; 42:183-91. [PMID: 20237864 DOI: 10.1007/s12031-010-9343-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2009] [Accepted: 02/17/2010] [Indexed: 10/19/2022]
Abstract
Low levels of hypoxia have been suggested to be a mechanism of retinal damage in glaucoma. To test the hypothesis that the activation of the hypoxia-responsive transcription factor hypoxia inducible factor-1alpha (HIF-1alpha) is involved in the pathophysiology of glaucoma, we used a rat model of glaucoma to study (1) HIF-1alpha retinal protein levels by immunoblot analysis, (2) cellular localization of HIF-1alpha in the retina by immunohistochemistry, and (3) expression of retinal HIF-1 gene targets by quantitative real-time polymerase chain reaction. Glaucoma was unilaterally induced in rats by injecting hypertonic saline in episcleral veins. We find that HIF-1alpha protein was increased in the retina following elevation of intraocular pressure, specifically in Müller glia and astrocytes but not in activated microglia. Eight established HIF-1 target genes were measured in experimental glaucoma. Retinal Epo, Flt-1, Hsp-27, Pai-1, and Vegfa mRNA levels were increased and Et-1, Igf2, and Tgfbeta3 levels were decreased in the glaucomatous retinas. Thus, the increase in HIF-1alpha levels in Müller glia and astrocytes is accompanied by a marked up regulation of some, but not all, HIF-1 transcriptional targets. These data support the hypothesis that HIF-1alpha becomes transcriptionally active in astrocytes and Müller cells but not microglia or neurons in glaucoma, arguing against a global hypoxia stimulus to the retina.
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26
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Qiu Y, Hoareau-Aveilla C, Oltean S, Harper SJ, Bates DO. The anti-angiogenic isoforms of VEGF in health and disease. Biochem Soc Trans 2009; 37:1207-13. [PMID: 19909248 PMCID: PMC2882696 DOI: 10.1042/bst0371207] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Anti-angiogenic VEGF (vascular endothelial growth factor) isoforms, generated from differential splicing of exon 8, are widely expressed in normal human tissues but down-regulated in cancers and other pathologies associated with abnormal angiogenesis (cancer, diabetic retinopathy, retinal vein occlusion, the Denys-Drash syndrome and pre-eclampsia). Administration of recombinant VEGF(165)b inhibits ocular angiogenesis in mouse models of retinopathy and age-related macular degeneration, and colorectal carcinoma and metastatic melanoma. Splicing factors and their regulatory molecules alter splice site selection, such that cells can switch from the anti-angiogenic VEGF(xxx)b isoforms to the pro-angiogenic VEGF(xxx) isoforms, including SRp55 (serine/arginine protein 55), ASF/SF2 (alternative splicing factor/splicing factor 2) and SRPK (serine arginine domain protein kinase), and inhibitors of these molecules can inhibit angiogenesis in the eye, and splice site selection in cancer cells, opening up the possibility of using splicing factor inhibitors as novel anti-angiogenic therapeutics. Endogenous anti-angiogenic VEGF(xxx)b isoforms are cytoprotective for endothelial, epithelial and neuronal cells in vitro and in vivo, suggesting both an improved safety profile and an explanation for unpredicted anti-VEGF side effects. In summary, C-terminal distal splicing is a key component of VEGF biology, overlooked by the vast majority of publications in the field, and these findings require a radical revision of our understanding of VEGF biology in normal human physiology.
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Affiliation(s)
- Yan Qiu
- Microvascular Research Laboratories, Bristol Heart Institute, Department of Physiology and Pharmacology, School of Veterinary Sciences, University of Bristol, Southwell Street, Bristol BS2 8EJ, U.K
| | - Coralie Hoareau-Aveilla
- Microvascular Research Laboratories, Bristol Heart Institute, Department of Physiology and Pharmacology, School of Veterinary Sciences, University of Bristol, Southwell Street, Bristol BS2 8EJ, U.K
| | - Sebastian Oltean
- Microvascular Research Laboratories, Bristol Heart Institute, Department of Physiology and Pharmacology, School of Veterinary Sciences, University of Bristol, Southwell Street, Bristol BS2 8EJ, U.K
| | - Steven J. Harper
- Microvascular Research Laboratories, Bristol Heart Institute, Department of Physiology and Pharmacology, School of Veterinary Sciences, University of Bristol, Southwell Street, Bristol BS2 8EJ, U.K
| | - David O. Bates
- Microvascular Research Laboratories, Bristol Heart Institute, Department of Physiology and Pharmacology, School of Veterinary Sciences, University of Bristol, Southwell Street, Bristol BS2 8EJ, U.K
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Structure-function analysis of VEGF receptor activation and the role of coreceptors in angiogenic signaling. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1804:567-80. [PMID: 19761875 DOI: 10.1016/j.bbapap.2009.09.002] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 08/22/2009] [Accepted: 09/04/2009] [Indexed: 12/11/2022]
Abstract
Vascular endothelial growth factors (VEGFs) constitute a family of six polypeptides, VEGF-A, -B, -C, -D, -E and PlGF, that regulate blood and lymphatic vessel development. VEGFs specifically bind to three type V receptor tyrosine kinases (RTKs), VEGFR-1, -2 and -3, and to coreceptors such as neuropilins and heparan sulfate proteoglycans (HSPG). VEGFRs are activated upon ligand-induced dimerization mediated by the extracellular domain (ECD). A study using receptor constructs carrying artificial dimerization-promoting transmembrane domains (TMDs) showed that receptor dimerization is necessary, but not sufficient, for receptor activation and demonstrates that distinct orientation of receptor monomers is required to instigate transmembrane signaling. Angiogenic signaling by VEGF receptors also depends on cooperation with specific coreceptors such as neuropilins and HSPG. A number of VEGF isoforms differ in binding to coreceptors, and ligand-specific signal output is apparently the result of the specific coreceptor complex assembled by a particular VEGF isoform. Here we discuss the structural features of VEGF family ligands and their receptors in relation to their distinct signal output and angiogenic potential.
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28
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Rennel ES, Harper SJ, Bates DO. Therapeutic potential of manipulating VEGF splice isoforms in oncology. Future Oncol 2009; 5:703-12. [PMID: 19519209 DOI: 10.2217/fon.09.33] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Anti-angiogenic therapies currently revolve around targeting vascular endothelial growth factor-A (VEGF-A) or its receptors. These therapies are effective to some degree, but have low response rates and poor side-effect profiles. Part of these problems is likely to be due to their lack of specificity between pro- and anti-angiogenic isoforms, and their nonspecific effects on proactive, pleiotropic survival and maintenance roles of VEGF-A in endothelial and other cell types. An alternative approach, and one which has recently been shown to be effective in animal models of neovascularization in the eye, is to target the mechanisms by which the cell generates pro-angiogenic splice forms of VEGF-A, its receptors and, co-incidentally, by targeting the upstream processes, other oncogenes that have antagonistic splice isoforms. The concept here is to target the splicing mechanisms that control splice site choice in the VEGF-A mRNA. Recent evidence on the pharmacological possibilities of such splice factors is described.
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Affiliation(s)
- Emma S Rennel
- Microvascular Research Laboratories, Department of Physiology and Pharmacology, School of Veterinary Sciences, University of Bristol, Bristol, UK.
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Failure to up-regulate VEGF165b in maternal plasma is a first trimester predictive marker for pre-eclampsia. Clin Sci (Lond) 2009; 116:265-72. [PMID: 18826376 PMCID: PMC2635543 DOI: 10.1042/cs20080270] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Pre-eclampsia is a pregnancy-related condition characterized by hypertension,
proteinuria and endothelial dysfunction. VEGF165b, formed by
alternative splicing of VEGF (vascular endothelial growth factor) pre-mRNA,
inhibits VEGF165-mediated vasodilation and angiogenesis, but has not
been quantified in pregnancy. ELISAs were used to measure
means±S.E.M. plasma VEGF165b, sEng (soluble endoglin) and
sFlt-1 (soluble fms-like tyrosine kinase-1). At 12 weeks of
gestation, the plasma VEGF165b concentration was significantly
up-regulated in plasma from women who maintained normal blood pressure
throughout their pregnancy (normotensive group,
4.90±1.6 ng/ml; P<0.01, as
determined using a Mann-Whitney U test) compared with
non-pregnant women (0.40±0.22 ng/ml). In contrast, in
patients who later developed pre-eclampsia, VEGF165b levels were
lower than in the normotensive group (0.467±0.209 ng/ml),
but were no greater than non-pregnant women. At term, plasma VEGF165b
concentrations were greater than normal in both pre-eclamptic
(3.75±2.24 ng/ml) and normotensive
(10.58 ng/ml±3.74 ng/ml;
P>0.1 compared with pre-eclampsia) pregnancies.
Patients with a lower than median plasma VEGF165b at
12 weeks had elevated sFlt-1 and sEng pre-delivery. Concentrations of
sFlt-1 (1.20±0.07 and 1.27±0.18 ng/ml) and sEng
(4.4±0.18 and 4.1±0.5 ng/ml) were similar at
12 weeks of gestation in the normotensive and pre-eclamptic groups
respectively. Plasma VEGF165b levels were elevated in pregnancy, but
this increase is delayed in women that subsequently develop pre-eclampsia. In
conclusion, low VEGF165b may therefore be a clinically useful first
trimester plasma marker for increased risk of pre-eclampsia.
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Benest AV, Bates DO. Measurement of angiogenic phenotype by use of two-dimensional mesenteric angiogenesis assay. Methods Mol Biol 2009; 467:251-70. [PMID: 19301676 DOI: 10.1007/978-1-59745-241-0_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Successful therapeutic angiogenesis requires an understanding of how the milieu of growth factors available combine to form a mature vascular bed. This requires a model in which multiple physiological and cell biological parameters can be identified. The adenoviral-mediated mesenteric angiogenesis assay as described here is ideal for that purpose. Adenoviruses expressing growth factors (vascular endothelial growth factor [VEGF] and angiopoietin 1 [Ang-1]) were injected into the mesenteric fat pad of adult male Wistar rats. The clear, thin, and relatively avascular mesenteric panel was used to measure increased vessel perfusion by intravital microscopy. In addition, high-powered microvessel analysis was carried out by immunostaining of features essential for the study of angiogenesis (endothelium, pericyte, smooth muscle cell area, and proliferation), allowing functional data to be obtained in conjunction with high-power microvessel ultrastructural analysis. A combination of individual growth factors resulted in a distinct vascular phenotype from either factor alone, with all treatments increasing the functional vessel area. VEGF produced shorter, narrow, highly branched, and sprouting vessels with normal pericyte coverage. Ang-1 induced broader, longer neovessels with no apparent increase in branching or sprouting. However, Ang-1-induced blood vessels displayed a significantly higher pericyte ensheathment. Combined treatment resulted in higher perfusion, larger and less-branched vessels, with normal pericyte coverage, suggesting them to be more mature. This model can be used to show that Ang-1 and VEGF use different physiological mechanisms to enhance vascularisation of relatively avascular tissue.
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Affiliation(s)
- Andrew V Benest
- Division of Vascular Oncology and Metastasis, DKFZ, Heidelberg, Germany
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31
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Bevan HS, van den Akker NMS, Qiu Y, Polman JAE, Foster RR, Yem J, Nishikawa A, Satchell SC, Harper SJ, Gittenberger-de Groot AC, Bates DO. The alternatively spliced anti-angiogenic family of VEGF isoforms VEGFxxxb in human kidney development. Nephron Clin Pract 2008; 110:p57-67. [PMID: 19039247 PMCID: PMC2635558 DOI: 10.1159/000177614] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Accepted: 09/01/2008] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND/AIM Vascular endothelial growth factor (VEGF), required for renal development, is generated by alternative splicing of 8 exons to produce two families, pro-angiogenic VEGF(xxx), formed by proximal splicing in exon 8 (exon 8a), and anti-angiogenic VEGF(xxx)b, generated by distal splicing in exon 8 (exon 8b). VEGF(165)b, the first described exon 8b-containing isoform, antagonises VEGF(165) and is anti-angiogenic in vivo. METHODS Using VEGF(xxx)b-specific antibodies, we investigated its expression quantitatively and qualitatively in developing kidney, and measured the effect of VEGF(165)b on renal endothelial and epithelial cells. RESULTS VEGF(xxx)b formed 45% of total VEGF protein in adult renal cortex, and VEGF(165)b does not increase glomerular endothelial cell permeability, it inhibits migration, and is cytoprotective for podocytes. During renal development, VEGF(xxx)b was expressed in the condensed vesicles of the metanephros, epithelial cells of the comma-shaped bodies, invading endothelial cells and epithelial cells of the S-shaped body, and in the immature podocytes. Expression reduced as the glomerulus matured. CONCLUSION These results show that the anti-angiogenic VEGF(xxx)b isoforms are highly expressed in adult and developing renal cortex, and suggest that the VEGF(xxx)b family plays a role in glomerular maturation and podocyte protection by regulating the pro-angiogenic pro-permeability properties of VEGF(xxx) isoforms.
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Affiliation(s)
- Heather S Bevan
- Microvascular Research Laboratories, Department of Physiology, University of Bristol, Bristol, UK
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Freitas-Andrade M, Carmeliet P, Stanimirovic DB, Moreno M. VEGFR-2-mediated increased proliferation and survival in response to oxygen and glucose deprivation in PlGF knockout astrocytes. J Neurochem 2008; 107:756-67. [DOI: 10.1111/j.1471-4159.2008.05660.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Abstract
The physiology of microvessels limits the growth and development of tumours. Tumours gain nutrients and excrete waste through growth-associated microvessels. New anticancer therapies target this microvasculature by inhibiting vascular endothelial growth factor A (VEGF-A) splice isoforms that promote microvessel growth. However, certain VEGF-A splice isoforms in normal tissues inhibit growth of microvessels. Thus, it is the VEGF-A isoform balance, which is controlled by mRNA splicing, that orchestrates angiogenesis. Here, we highlight the functional differences between the pro-angiogenic and the anti-angiogenic VEGF-A isoform families and the potential to harness the synthetic capacity of cancer cells to produce factors that inhibit, rather than aid, cancer growth.
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Affiliation(s)
- Steven J Harper
- Microvascular Research Laboratories, Department of Physiology & Pharmacology, Bristol Heart Institute, School of Veterinary Science, University of Bristol, Southwell Street, Bristol BS2 8EJ, UK.
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VEGF 165 b, an antiangiogenic VEGF-A isoform, binds and inhibits bevacizumab treatment in experimental colorectal carcinoma: balance of pro- and antiangiogenic VEGF-A isoforms has implications for therapy. Br J Cancer 2008; 98:1366-79. [PMID: 18349829 PMCID: PMC2361696 DOI: 10.1038/sj.bjc.6604308] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Bevacizumab, an anti-vascular endothelial growth factor (VEGF-A) antibody, is used in metastatic colorectal carcinoma (CRC) treatment, but responses are unpredictable. Vascular endothelial growth factor is alternatively spliced to form proangiogenic VEGF165 and antiangiogenic VEGF165b. Using isoform-specific enzyme-linked immunosorbent assay and quantitative polymerase chain reaction, we found that over 90% of the VEGF in normal colonic tissue was VEGFxxxb, but there was a variable upregulation of VEGFxxx and downregulation of VEGFxxxb in paired human CRC samples. Furthermore, cultured colonic adenoma cells expressed predominantly VEGFxxxb, whereas colonic carcinoma cells expressed predominantly VEGFxxx. However, adenoma cells exposed to hypoxia switched their expression from predominantly VEGFxxxb to predominantly VEGFxxx. VEGF165b overexpression in LS174t colon cancer cells inhibited colon carcinoma growth in mouse xenograft models. Western blotting and surface plasmon resonance showed that VEGF165b bound to bevacizumab with similar affinity as VEGF165. However, although bevacizumab effectively inhibited the rapid growth of colon carcinomas expressing VEGF165, it did not affect the slower growth of tumours from colonic carcinoma cells expressing VEGF165b. Both bevacizumab and anti-VEGF165b-specific antibodies were cytotoxic to colonic epithelial cells, but less so to colonic carcinoma cells. These results show that the balance of antiangiogenic to proangiogenic isoforms switches to a variable extent in CRC, regulates tumour growth rates and affects the sensitivity of tumours to bevacizumab by competitive binding. Together with the identification of an autocrine cytoprotective role for VEGF165b in colonic epithelial cells, these results indicate that bevacizumab treatment of human CRC may depend upon this balance of VEGF isoforms.
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Curry FRE. Permeability measurements in an individually perfused capillary: the 'squid axon' of the microcirculation (1974). Exp Physiol 2008; 93:444-6. [PMID: 18344261 DOI: 10.1113/expphysiol.2007.040097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Fitz-Roy E Curry
- Department of Physiology and Membrane Biology, School of Medicine, One Shields Avenue, University of California-Davis, Davis, CA 95616, USA.
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Qiu Y, Bevan H, Weeraperuma S, Wratting D, Murphy D, Neal CR, Bates DO, Harper SJ. Mammary alveolar development during lactation is inhibited by the endogenous antiangiogenic growth factor isoform, VEGF165b. FASEB J 2007; 22:1104-12. [PMID: 18032632 DOI: 10.1096/fj.07-9718com] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Extensive tissue remodeling occurs in breast tissue during pregnancy, resulting in growth and development of the mammary gland associated with extensive vascular remodeling, which is thought to be dependent on vascular endothelial growth factor (VEGF). We show here that the endogenous antiangiogenic splice isoform of VEGF, VEGF(165)b, is normally expressed in nonlactating human and mouse breast, and is down-regulated in WT mice during lactation. To demonstrate the physiological role of VEGF(165)b in mammary tissue, we generated transgenic (TG) mice expressing VEGF(165)b, under the control of the mouse mammary tumor virus (MMTV) enhancer/promoter. These mice increase expression of VEGF(165)b in mammary tissue during mammary development. The offspring of TG mothers, but not TG fathers, die shortly after birth. The female TG mice have fewer blood vessels, less blood in the mammary tissue, and impaired alveolar coverage of the fat pad, and do not produce sufficient milk for nourishment of their pups. These findings demonstrate that endogenous overexpression of VEGF(165)b in the mammary gland inhibits physiological angiogenesis and that the regulation of the balance of VEGF isoforms is a requirement for mammary alveolar development and milk production. This study provides the first evidence for the role of endogenous antiangiogenic VEGF isoforms in normal physiology--their down-regulation is required for effective milk production.
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Affiliation(s)
- Yan Qiu
- Microvascular Research Laboratories, School of Veterinary Sciences, University of Bristol, Bristol, UK
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Ablonczy Z, Crosson CE. VEGF modulation of retinal pigment epithelium resistance. Exp Eye Res 2007; 85:762-71. [PMID: 17915218 PMCID: PMC2199266 DOI: 10.1016/j.exer.2007.08.010] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 08/14/2007] [Accepted: 08/15/2007] [Indexed: 01/13/2023]
Abstract
Fluid accumulation into the subretinal space and the development of macular edema is a common condition in age-related macular degeneration, diabetic retinopathy, and following ocular surgery, or injury. Vascular endothelial growth factor (VEGF) and other cytokines have been implicated in the disruption of retinal pigment epithelium (RPE) barrier function and a reduction in the regulated removal of subretinal fluid; however, the cellular and molecular events linking these agents to the disruption of barrier function have not been established. In the current study, cultures of ARPE-19 and primary porcine retinal pigment epithelium (RPE) cells were utilized to investigate the effects of the VEGF-induced modifications to the barrier properties of the RPE. The barrier function was determined by transepithelial resistance (TER) measurements and morphology of the RPE monolayers. In both ARPE-19 and primary porcine RPE cells the administration of VEGF produced a significant drop in TER, and this response was only observed following apical administration. Maximum reduction in TER was reached 5h post VEGF administration. These responses were concentration-dependent with an EC(50) of 502pg/mL in ARPE-19 cells and 251pg/mL in primary porcine cells. In both ARPE-19 and primary RPE cells, the response to VEGF was blocked by pretreatment with the relatively selective VEGF-R2 antagonists, SU5416 or ZM323881, or the protein tyrosine kinase inhibitor, genistein. Administration of the relatively selective VEGF-R2 agonist, VEGF-E, also reduced TER in a concentration-dependent manner (EC(50) of 474pg/mL), while VEGF-R1 agonist, placental growth factor (PlGF), did not significantly alter the TER. Immunolocalization studies demonstrated that confluent monolayers exhibited continuous cell-to-cell ZO-1 protein contacts and apical localization of the VEGF-R2 receptors. These data provide evidence that the VEGF-induced breakdown of RPE barrier function is mediated by the activation of apically-oriented VEGF-R2 receptors. Thus, VEGF-mediated increases in RPE permeability are initiated by a rise in intraocular levels of VEGF.
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Affiliation(s)
- Zsolt Ablonczy
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, USA.
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Pritchard-Jones RO, Dunn DBA, Qiu Y, Varey AHR, Orlando A, Rigby H, Harper SJ, Bates DO. Expression of VEGF(xxx)b, the inhibitory isoforms of VEGF, in malignant melanoma. Br J Cancer 2007; 97:223-30. [PMID: 17595666 PMCID: PMC2360298 DOI: 10.1038/sj.bjc.6603839] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Malignant melanoma is the most lethal of the skin cancers and the UK incidence is rising faster than that of any other cancer. Angiogenesis – the growth of new vessels from preexisting vasculature – is an absolute requirement for tumour survival and progression beyond a few hundred microns in diameter. We previously described a class of anti-angiogenic isoforms of VEGF, VEGFxxxb, that inhibit tumour growth in animal models, and are downregulated in some cancers, but have not been investigated in melanoma. To determine whether VEGFxxxb expression was altered in melanoma, PCR and immunohistochemistry of archived human tumour samples were used. In normal epidermis and in a proportion of melanoma samples, VEGFxxxb staining was seen. Some melanomas had much weaker staining. Subsequent examination revealed that expression was significantly reduced in primary melanoma samples (both horizontal and vertical growth phases) from patients who subsequently developed tumour metastasis compared with those who did not (analysis of variance (ANOVA) P<0.001 metastatic vs nonmetastatic), irrespective of tumour thickness, while the surrounding epidermis showed no difference in expression. Staining for total VEGF expression showed staining in metastatic and nonmetastatic melanomas, and normal epidermis. An absence of VEGFxxxb expression appears to predict metastatic spread in patients with primary melanoma. These results suggest that there is a switch in splicing as part of the metastatic process, from anti-angiogenic to pro-angiogenic VEGF isoforms. This may form part of a wider metastatic splicing phenotype.
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Affiliation(s)
- R O Pritchard-Jones
- Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Bristol, UK
| | - D B A Dunn
- Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Bristol, UK
| | - Y Qiu
- Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Bristol, UK
| | - A H R Varey
- Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Bristol, UK
| | - A Orlando
- Department of Plastic Surgery, Frenchay Hospital, Bristol, UK
| | - H Rigby
- Department of Pathology, Frenchay Hospital, Bristol, UK
| | - S J Harper
- Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Bristol, UK
| | - D O Bates
- Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Bristol, UK
- Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, University of Bristol, Southwell Street, Bristol BS2 8EJ, UK. E-mail:
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