Vascular Endothelial Growth Factor Molecules Research Articles

Canonical and noncanonical vascular endothelial growth factor pathways: new developments in biology and signal transduction.

The past 5 years have witnessed a significant expansion in our understanding of vascular endothelial growth factor (VEGF) signaling. In particular, the process of canonical activation of VEGF receptor tyrosine kinases by homodimeric VEGF molecules has now been broadened by the realization that heterodimeric ligands and receptors are also active participants in the signaling process. Although heterodimer receptors were described 2 decades ago, their impact, along with the effect of additional cell surface partners and novel autocrine VEGF signaling pathways, are only now starting to be clarified. Furthermore, ligand-independent signaling (noncanonical) has been identified through galectin and gremlin binding and upon rise of intracellular levels of reactive oxygen species. Activation of the VEGF receptors in the absence of ligand holds immediate implications for therapeutic approaches that exclusively target VEGF. The present review provides a concise summary of the recent developments in both canonical and noncanonical VEGF signaling and places these findings in perspective to their potential clinical and biological ramifications.

Suppression of choroidal neovascularization by Endostar in rats.

Choroidal neovascularization (CNV) is common in various retinal and choroidal diseases, and may result in severe and irreversible loss of vision. Our previous studies suggested that Endostar, a novel recombinant endostatin, is able to inhibit the proliferation and migration of choroid‑retinal endothelial cells. To further evaluate the effect of Endostar on the formation of CNV in vivo, a rat model of laser‑induced CNV was constructed and Endostar or phosphate‑buffered saline treatment was administered intravitreally every other day. Using fluorescein angiography (FA), reduced CNV incidence and leakage grade was observed in the Endostar group. In addition, CNV area and maximal thickness were prominently reduced in the Endostar group measured by choroid flat mounts and sections. Furthermore, vascular endothelial growth factor (VEGF), hypoxia‑inducible factor 1α and chemokine C‑X‑C motif ligand 1 were markedly reduced in the Endostar group as determined by quantitative polymerase chain reaction and downregulation of VEGF was also verified by western blot analysis at the protein level. This study demonstrates that Endostar suppressed CNV in a rat model, which may be largely mediated by the downregulation of VEGF and other angiogenic molecules.

Abstract 2145: Chemopreventive and immune-modulatory effects of the Cucumaria frondosa extract, Frondanol A5 in the APCMin/+ mice intestinal tumorigenesis

Abstract Sea cucumbers have been used widely as a food source and for their health benefits, which include treatment of various chronic inflammatory conditions. We have shown previously that Cucumaria frondosa extract, Frondanol A5 inhibits azoxymethane -induced colonic precursor lesions in F344 rats. Experiments were designed to assess the chemopreventive efficacy of Frondanol A5, for suppression of intestinal tumorigenesis in male and female APCMin/+ mice. Six-week-old APCMin/+ mice were fed the modified AIN-76A diets containing 0, 250 or 500 ppm Frondanol A5 for 14 weeks. To understand molecular mechanisms, we analyzed levels of proliferation, inflammatory and angiogenesis makers; PCNA, inflammatory cytokines, 5-lipoxygenase (5-LOX), Five Lox Activating Protein (FLAP) and vascular endothelial growth factor (VEGF) expressions by IHC, IHF, and/or RT-PCR methods. To determine immuno-modulatory effects of Fondanol A5 on intestinal tumorigenesis, number of macrophages was evaluated in the blood, SI polyps and colon tumors by Giemsa staining, ex-vivo phagocytic assay was performed on the peritoneal macrophages isolated from the control and treated mice. Further, γ-interferon-inducible lysosomal thiolreductase (GILT) mRNA expression was analyzed in the peritoneal macrophages, SI polyps and colonic tumors. Dietary administration of 250 and 500 ppm of Frondanol A5 suppressed small intestinal polyp formation up to 28 % (p<0.02) in males and up to 50 % (p<0.01) in females; and significantly decreased polyp size in both genders. Importantly, 250 and 500 ppm Frondanol A5 diet suppressed colon tumors multiplicities by 65% (p<0.007) and 75% (p<0.0001) as compared to control diet fed male APCMin/+ mice. Similarly, in female APCMin/+ mice, dietary Frondanol A5 at both dose levels suppressed colon tumor multiplicities up to 80% (p<0.0001). Frondanol A5 showed significant colon tumor inhibitory dose-response effects in male APCMin/+ mice. Intestinal tumors of Frondanol A5-fed mice showed significantly reduced expression of PCNA, 5-LOX, its regulator molecule, FLAP and angiogenic marker VEGF. Frondanol A5-fed-mice showed suppression of serum inflammatory cytokines and increased expression of granulocyte-colony stimulating factor (G-CSF) by ELISA. Importantly, mice treated with Frondanol A5 diet showed enhanced phagocytic activity and increase in number of macrophages (Control 24% Vs treated 50%; p<0.01) and caused a significant increase in GILT mRNA expression, in both peritoneal macrophages as well as colonic tumors. These results suggest that Frondanol A5 exhibits significant chemopreventive potential in FAP model of SI and colon tumorigenesis. Frondanol A5 induced antitumor activities in part mediated through modulation of inflammatory molecules and stimulation of macrophage activity. Supported by NIH Grant N01-CN-53300 and R01CA094962. Citation Format: Naveena B. Janakiram, Altaf Mohammed, Misty Brewer, Peter D. Collin, Vernon E. Steele, Chinthalapally V. Rao. Chemopreventive and immune-modulatory effects of the Cucumaria frondosa extract, Frondanol A5 in the APCMin/+ mice intestinal tumorigenesis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2145. doi:10.1158/1538-7445.AM2014-2145

Molecular imaging of expression of vascular endothelial growth factor a (VEGF a) in femoral bone grafts transplanted into living mice.

The biology of cells transplanted with bone grafts is incompletely understood. Focusing on the early angiogenic response postgrafting, we report a mouse femur graft model in which grafts were derived from mice transgenic for a firefly luciferase (FLuc) bioluminescence reporter gene driven by a promoter for the angiogenic signaling molecule vascular endothelial growth factor (VEGF). Upon transplantation into wild-type (wt) mice, in vivo bioluminescence imaging (BLI) permitted longitudinal visualization and measurements of VEGF promoter activity in the transplanted graft cells and demonstrated a lag period of 7 days posttransplantation prior to robust induction of the promoter. To determine cellular mediators of VEGF induction in graft bone, primary graft-derived osteoblastic cells (GDOsts) were characterized. In vitro BLI on GDOsts showed hypoxia-induced VEGF expression and that this induction depended on PI3K signaling and, to a lesser degree, on the MEK pathway. This transcriptional regulation correlated with VEGF protein production and was validated in GDOsts seeded on demineralized bone matrix (DBM), a bone graft substitute material. Together, combined imaging of VEGF expression in living animals and in live cells provided clues about the regulation of VEGF in cells post-bone grafting. These data are particularly significant toward the development of future smart bone graft substitutes.

VEGF Signaling in Cancer Treatment

Induction of angiogenesis represents one of the major hallmarks of cancer. The growth of new vessels is crucial to provide malignant cells with an adequate supply of oxygen and nutrients. It is generally accepted that vascular endothelial growth factor (VEGF) is a major driver of the angiogenic process in physiological and pathological processes in both embryo and adult. VEGF is often found overexpressed in tumors, as well as its receptors VEGFR1 and VEGFR2. Hence, several different strategies have been designed to target VEGF signal transduction. In the last decades, multiple inhibitors have been therapeutically validated in preclinical models and several clinical trials. Neutralizing monoclonal antibodies against VEGF and small molecule tyrosine kinase inhibitors targeting VEGFRs have been shown to block its angiogenic activity, resulting in tumor vascular regression, anti-tumor effects and improvements in patient survival. However, side effects and lack of efficacy in some instances challenge the potential clinical impact of these therapies. This review examines the role of VEGF signaling in cancer and outlines the current status of anti-angiogenic therapies against VEGF pathway.

Assessment of vascular endothelial growth factor in formalin fixed, paraffin embedded colon cancer specimens by means of a well-based reverse phase protein array.

BackgroundVascular endothelial growth factor (VEGF) is a critical pro-angiogenic factor, found in a number of cancers, and a target of therapy. It is typically assessed by immunohistochemistry (IHC) in clinical research. However, IHC is not a quantitative assay and is rarely reproducible. We compared VEGF levels in colon cancer by IHC and a quantitative immunoassay on proteins isolated from formalin fixed, paraffin embedded tissues.ResultsVEGF expression was studied by means of a well-based reverse phase protein array (RPPA) and immunohistochemistry in 69 colon cancer cases, and compared with various clinicopathologic factors. Protein lysates derived from formalin fixed, paraffin embedded tissue contained measurable immunoreactive VEGF molecules. The VEGF expression level of well differentiated colon cancer was significantly higher than those with moderately and poorly differentiated carcinomas by immunohistochemistry (P = 0.04) and well-based RPPA (P = 0.04). VEGF quantification by well-based RPPA also demonstrated an association with nodal metastasis status (P = 0.05). In addition, the normalized VEGF value by well-based RPPA correlated (r = 0.283, P = 0.018). Furthermore, subgroup analysis by histologic type revealed that adenocarcinoma cases showed significant correlation (r = 0.315, P = 0.031) between well-based RPPA and IHC.ConclusionsThe well-based RPPA method is a high throughput and sensitive approach, is an excellent tool for quantification of marker proteins. Notably, this method may be helpful for more objective evaluation of protein expression in cancer patients.

Preclinical pharmacokinetics and disposition of a novel selective VEGFR inhibitor fruquintinib (HMPL-013) and the prediction of its human pharmacokinetics.

This study evaluated the preclinical pharmacokinetics (PK) and disposition of fruquintinib (HMPL-013), a small molecule vascular endothelial growth factor receptors inhibitor. In vitro and in vivo PK/ADME assays were conducted. Allometry and PK modeling/simulation were conducted to predict human PK parameters and the time course profiles. HMPL-013 has high permeability without efflux. It shows moderate oral bioavailability of 42-53 % and Tmax < 4 h in mouse, rat, dog and monkey, with exposure-dose linearity proved in rats and dogs. No significant food effect is on dog PK. HMPL-013 has moderately high tissue distribution. It majorly distributes in gastrointestinal tract, liver, kidney, adrenal and adipose. The plasma protein binding fraction is 88-95 % in mouse, rat, dog and human, invariable up to 10 µM. The in vivo clearance of HMPL-013 is low, consistent with the in vitro scaling. Three major oxidative metabolites were identified in liver microsomes of mouse, rat, dog, monkey and human. Dog is mostly similar to human regarding in vitro metabolism. Demethylation, hydroxylation and sequential glucuronidation are the major in vivo metabolic reactions. Direct urinary and biliary excretion of HMPL-013 is negligible. Metabolizing to M1 (demethylation), sequentially glucuronidating, followed by biliary excretion, and to a less extent, by urinary excretion, are important elimination pathways for HMPL-013 in rats. HMPL-013 has low risk of drug-drug interaction. It is predicted to have favorable human PK properties and low efficacious dose. HMPL-013 demonstrates good preclinical PK and enables successful human PK and dose projection. It is valuable for further clinical development.

Bangpungtongseong-san, a traditional herbal medicine, attenuates chronic asthmatic effects induced by repeated ovalbumin challenge

Airway remodeling is characterized by airway wall thickening, subepithelial fibrosis, increased smooth muscle mass, angiogenesis and increased mucus secretion, which can lead to chronic and obstinate asthma and can obstruct pulmonary function. In this study, the effects of Bangpungtongseong-san water extract (BPTS) on airway remodeling were examined using a murine model of bronchial asthma induced by ovalbumin (OVA) challenge. We focused on the effects of BPTS on the regulation of chronic asthma. BALB/c mice were randomly assigned to 5 groups, some of which were sensitized and challenged with OVA for 4 weeks. After the final ovalbumin challenge, typical asthma-like morphological changes were observed in the lung tissue with hematoxylin and eosin staining, periodic acid-Schiff, as well as with Masson's trichrome staining. The levels of transforming growth factor-β1 (TGF-β1) and Smad3 were assessed by immunohistochemistry and western blot analysis. The expression levels of vascular endothelial growth factor (VEGF) and adhesion molecules, such as intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were also detected by western blot analysis. Our results revealed that BPTS reduced the OVA-induced increase in the infiltration of leukocytes, mucus hyperplasia and collagen deposition. Compared with the OVA-challenged group, the BPTS group had lower expression levels of adhesion molecules, TGF-β1, Smad3 and VEGF proteins in the lung tissues. The results of the current study suggest that BPTS prevents asthma airway remodeling in chronic asthma by inhibiting the activation of the TGF-β1-Smad3-signaling pathway, as well as the expression of VEGF and adhesion molecules. BPTS may thus be a potential drug for the treatment of patients with changes that occur in the airways due to severe asthma.

The Role of Retinyl Acetate in Chemoprevention

Retinoids have a role in the process of chemoprevention. They can inhibit promotion through inhibiting cell proliferation, enhancing apoptosis and anti-oxidative properties. In the present study initiative-p-dimethylaminoazobenzene (p-DAB) and promotive- 2, 3, 7, 8-Tetrachlorodibenzo-p-Dioxin (TCDD) was given to the rats subchronically. It was aim to evaluate the effects on the apoptosis and lipid peroxidation of Retinyl Acetate in the liver and to determine the plasma levels of Vascular Endothelial Growth Factor (VEGF) and Matrix Metalloproteinase-2 (MMP-2) different fixation intervals called as 30, 60, 90 and 120. Apoptosis was determined with assays of Cytochrome c release and DNA fragmentation. Preneoplastic changes in the liver tissues were evaluated histopathologically. In p-DAB+TCDD group there were a decrease apoptosis and an increase lipid peroxidation, VEGF levels and preneoplastic changes beginning from day 60. The increase of MMP-2 levels was shown at day 90 and 120. There was an increase in the apoptosis and also decrease in the lipid peroxidation and levels of VEGF in the Retiniyl Acetate treated rats compare to p-DAB+TCDD group at day 60, 90, and 120. Mild preneoplastic changes and decreased MMP-2 were also observed only at day 120. Retinyl acetate may affect the stages of promotion that appeared preneoplastic changes via inducing apoptosis, reducing lipid peroxidation in the liver and decreasing levels of pro-angiogenic molecule VEGF and pro-invasive molecule MMP-2.

Binding of VEGF-A to canine cancer cells with preferential expression of VEGFR1

Aim: Despite encouraging results in syngeneic and xenografts cancer models with various inhibitors of vascular endothelial growth factor (VEGF) or its receptors (VEGFRs), beneficial effects have not been consistently translated to the clinic, underscoring the need to develop strategies that go beyond the inhibition of these targets. The purpose of this study was to generate data to support the hypothesis that VEGF may be used as “bait” to selectively deliver therapeutics to VEGFRexpressing cancer cells. Materials and Methods: VEGFR1 and VEGFR2 expression was characterized using real time quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) in canine hemangiosarcoma (Grace-HSA, Emma-HSA), melanoma (TLM-1), and thyroid adenocarcinoma (CTAC) cell lines. TLM-1 and Grace-HSA were identified as representative cell lines that selectively expressed high levels of VEGFR1. Flow cytometry was performed to examine binding of a single VEGF molecule (biotinylated VEGFA and avidin conjugated to fluorescein isothiocyanate (FITC)) by these chemoresistant cell

Verifiable Hypotheses for Thymosin β4-Dependent and -Independent Angiogenic Induction of Trichinella spiralis-Triggered Nurse Cell Formation

Trichinella spiralis has been reported to induce angiogenesis for nutrient supply and waste disposal by the induction of the angiogenic molecule vascular endothelial cell growth factor (VEGF) during nurse cell formation. However, the action mechanism to induce VEGF in nurse cells by T. spiralis is not known. Hypoxia in nurse cells was suggested as a possible mechanism; however, the presence of hypoxic conditions in infected muscle or nurse cells and whether hypoxia indeed induces the expression of VEGF and subsequent angiogenesis in the infected muscle are both a matter of debate. Our recent studies have shown that thymosin β4, a potent VEGF inducing protein, is expressed in the very early stages of T. spiralis muscle infection suggesting the induction of VEGF in early stage nurse cells. Nevertheless, we now show that hypoxic conditions were not detected in any nurse cell stage but were detected only in the accumulated inflammatory cells. These studies propose that induction of angiogenesis by VEGF in T. spiralis-infected nurse cells was mediated by thymosin β4 and is unrelated to hypoxic conditions.

티모신베타4에의한 선모충(Trichinella spiralis) 감염의 혈관신생 유도 기작

선모충(Trichinella spiralis)은 감염 후 nurse cell 형성과정에서 영양분 공급 및 배설을 위해 혈관신생인자인 vascular endothelial cell growth factor (VEGF)를 유도하여 혈관신생을 촉진한다. 하지만 이러한 과정 중 선모충이 어떻게 VEGF의 발현을 유도하는지에 대해서는 아직 밝혀지지 않았다. Nurse cell 형성 과정에서 저산소현상이 발생되고 이러한 저산소 현상이 VEGF의 발현을 유도할 것이라는 제안이 있지만 실제 nurse cell 형성 과정에 저산호 현상이 일어나는지도 조사되지 않았으며 저산소 현상이 실제 VEGF를 통한 혈관신생을 유도하는지도 규명되지 않았다. 최근 연구결과에 의하면 VEGF의 발현을 유도하는 티모신베타4 단백질이 초기의 선모충 감염 nurse cell에서 강력하게 유도되는 것이 관찰되었다. 게다가 저산소 현상이 nurse cell 형성 과정에서 관찰되지 않았고 면역세포들이 응집되어 있는 파괴되는 nurse cell에서만 관찰되는 것이 밝혀졌다. 이러한 결과는 티모신베타4가 저산소 현상과 무관하게 선모충 감염 nurse cell에서의 VEGF 유도 및 혈관신생을 유도할 가능성을 제시해 준다. Trichinella spiralis (T. spiralis) has been reported to induce angiogenesis and a supply of nutrients and to act as a reliable waste disposal system by induction of the expression of the angiogenic molecule vascular endothelial cell growth factor (VEGF) during nurse cell formation. However, the mechanism underlying the induction of VEGF in nurse cells by T. spiralis has not yet been defined. Some research has pointed to the possibility of hypoxia in nurse cells, but whether hypoxia occurs in infected muscle or nurse cells has not been studied. It is also a matter of debate whether hypoxia induces the expression of VEGF and subsequent angiogenesis in infected muscle. Recent studies showed that thymosin <TEX>${\beta}4$</TEX>, a potent VEGF-inducing protein, was expressed at a very early stage of muscle infection by T. spiralis, suggesting that VEGF is induced at an early stage in nurse cells. Furthermore, hypoxia was not detected in any nurse cell stage but was detected in inflammatory cells. The findings suggest that induction of angiogenesis by VEGF in T. spiralis-infected nurse cells is mediated by thymosin <TEX>${\beta}4$</TEX> and unrelated to hypoxia.

THU0020 Angiogenesis in Rheumatoid Arthritis: VEGF Expression in Synovial Fluid

BackgroundThe expansion of synovial epithelium in Rheumatoid Arthritis (RA), and the subsequent pannus invasion of underlying cartilage and bone, needs an increase in the vascular supply to the synovium. Angiogenesis...

Functionalization of electrospun poly(ε-caprolactone) scaffold with heparin and vascular endothelial growth factors for potential application as vascular grafts

In this study, a heparin-conjugated poly(ε-caprolactone) electrospun fiber was constructed to develop a functional scaffold for controlled release of vascular endothelial growth factors. The immobilization of vascular endothelial growth factor was achieved through affinity binding between heparin and vascular endothelial growth factor molecules. The sustained release of vascular endothelial growth factor from the scaffold was followed for up to 15 days. The endothelial cell adhesion and proliferation assay demonstrated that immobilized vascular endothelial growth factor maintained its activity. The blood compatibility of the scaffold was evaluated by activated partial thromboplastin time, platelet adhesion test, and arteriovenous shunt, and the functionalized scaffold showed improved anticoagulation properties. The biocompatibility was evaluated by subcutaneous implantation. Results showed that this vascular endothelial growth factor–releasing scaffold stimulated neovascularization with minimum immunological rejection compared to the unmodified poly(ε-caprolactone) scaffold. The present study demonstrated a new strategy of building bioactive scaffolds for the development of small-diameter vascular graft.

VEGF165b overexpression restores normal glomerular water permeability in VEGF164-overexpressing adult mice

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.

The Structural Basis for the Function of Two Anti-VEGF Receptor 2 Antibodies

The anti-VEGF receptor 2 antibody IMC-1121B is a promising antiangiogenic drug being tested for treatment of breast and gastric cancer. We have determined the structure of the 1121B Fab fragment in complex with domain 3 of VEGFR2, as well as the structure of a different neutralizing anti-VEGFR2 antibody, 6.64, also in complex with VEGFR2 domain 3. The two Fab fragments bind at opposite ends of VEGFR2 domain 3; 1121B directly blocks VEGF binding, whereas 6.64 may prevent receptor dimerization by perturbing the domain 3:domain 4 interface. Mutagenesis reveals that residues essential for VEGF, 1121B, and 6.64 binding are nonoverlapping among the three contact patches.

The Ron receptor promotes prostate tumor growth in the TRAMP mouse model

The Ron receptor tyrosine kinase is overexpressed in many cancers, including prostate cancer. In order to examine the significance of Ron in prostate cancer in vivo, we utilized a genetically engineered mouse model, referred to as TRAMP mice, that is predisposed to develop prostate tumors. In this model, we demonstrate that prostate tumors from 30-week-old TRAMP mice have increased Ron expression compared to age-matched wild-type prostates. Based on the upregulation of Ron in human prostate cancers and in this murine model of prostate tumorigenesis, we hypothesized that this receptor plays a functional role in the development of prostate tumors. To test this hypothesis, we crossed TRAMP mice with mice that are deficient in Ron signaling (TK−/−). Interestingly, TK−/− TRAMP+ mice show a significant decrease in prostate tumor mass relative to TRAMP mice containing functional Ron. Moreover, TK−/− TRAMP+ prostate tumors exhibited decreased tumor vascularization relative to TK+/+ TRAMP+ prostate tumors, which correlated with reduced levels of the angiogenic molecules VEGF and CXCL2. While Ron loss did not alter tumor cell proliferation, a significant decrease in cell survival was observed. Similarly, murine prostate cancer cell lines containing a Ron deficiency exhibited decreased levels of active NF-kappaB suggesting that Ron may be important in regulating prostate cell survival at least partly through this pathway. In total, our data show for the first time that Ron promotes prostate tumor growth, prostate tumor angiogenesis, and prostate cancer cell survival in vivo.

Trichinella spiralis infection induces angiogenic factor thymosin β4 expression

Trichinella spiralis (T. spiralis) has been reported to up-regulate the expression of the angiogenic molecule vascular endothelial cell growth factor (VEGF) during nurse cell formation. In order to analyze the induction of angiogenesis by T. spiralis, the expression patterns of angiogenesis-related proteins were investigated by immunohistochemical analysis. VEGF expression was induced in the infected muscles at an early stage of infection (10 days after infection) and diminished after 3 weeks. Thymosin β4, a major factor which induces VEGF, showed increased expression in muscle fibers 10 days after infection, and the expression remained high in the nurse cells for 6 weeks, when the formation of the nurse cell complex was completed. The hypoxia inducible factor (HIF)-1α showed a diffuse expression pattern around the infected muscle fibers and was strongly expressed in inflammatory cells but was not related to the hypoxic condition caused by nurse cell formation. Localization of the hypoxic regions by the hypoxia marker, pimonidazole showed T. spiralis infection does not induce a hypoxic condition in nurse cells. These results suggest that the expression of VEGF and thymosin β4 induce angiogensis and the expression of thymosin β4 remained elevated to potentially regulate nurse cell formation and maintenance.

How does interferon‐α insult the vasculature? Let me count the ways

How does interferon‐α insult the vasculature? Let me count the ways

Opposing roles for HIF-1α and HIF-2α in the regulation of angiogenesis by mononuclear phagocytes

AbstractMacrophages contribute to tumor growth through the secretion of the proangiogenic molecule vascular endothelial growth factor (VEGF). We previously observed that monocytes treated with the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) produce a soluble form of the VEGF receptor-1 (sVEGFR-1), which neutralizes VEGF biologic activity. The VEGF and VEGFR-1 promoters both contain a hypoxia regulatory element, which binds the hypoxia-inducible factor (HIF) transcription factors under hypoxic conditions. Based on this observation, we examined VEGF and sVEGFR-1 production from monocytes cultured at various O2 concentrations. The amount of sVEGFR-1 production observed from GM-CSF-treated monocytes increased with decreasing levels of O2. This sVEGFR-1 was biologically active and sequestered VEGF. To evaluate the role of the HIFs in sVEGFR-1 production, we used macrophages with a genetic deletion of HIF-1α. HIF-1α−/− macrophages cultured with GM-CSF at hypoxia secreted diminished amounts of VEGF compared with HIF-1α+/+ macrophages, whereas sVEGFR-1 secretion was unaffected. In contrast, siRNA-mediated knockdown of HIF-2α inhibited the production of sVEGFR-1 in response to GM-CSF and low O2, whereas VEGF production was unaffected. These studies suggest that hypoxia, generally thought to promote angiogenesis, can induce antiangiogenic behavior from macrophages within a GM-CSF–rich environment. Furthermore, these results suggest specific and independent roles for HIF-1α and HIF-2α in hypoxic macrophages.