Vascular endothelial growth factor (VEGF) is a potent stimulator of vascular angiogenesis, permeability, and remodeling that also plays important roles in wound healing and tissue cytoprotection. To begin to define the roles of VEGF in diseases like asthma and COPD, we characterized the effects of lung-targeted transgenic VEGF165 and defined the innate immune pathways that regulate VEGF tissue responses. The former studies demonstrated that VEGF plays an important role in Th2 inflammation because, in addition to stimulating angiogenesis and edema, VEGF induced eosinophilic inflammation, mucus metaplasia, subepithelial fibrosis, myocyte hyperplasia, dendritic cell activation, and airways hyperresponsiveness via IL-13–dependent and -independent mechanisms. VEGF was also produced at sites of aeroallergen-induced Th2 inflammation, and VEGF receptor blockade ameliorated adaptive Th2 inflammation and Th2 cytokine elaboration. The latter studies demonstrated that activation of the RIG-like helicase (RLH) innate immune pathway using viral pathogen–associated molecular patterns such as Poly(I:C) or viruses ameliorated VEGF-induced tissue responses. In accord with these findings, Poly(I:C)-induced RLH activation also abrogated aeroallergen-induced Th2 inflammation. When viewed in combination, these studies suggest that VEGF excess can contribute to the pathogenesis of Th2 inflammatory disorders such as asthma and that abrogation of VEGF signaling via RLH activation can contribute to the pathogenesis of viral disorders such as virus-induced COPD exacerbations. They also suggest that RLH activation may be a useful therapeutic strategy in asthma and related disorders.
asthma; chronic obstructive pulmonary disease; virus; RIG-like helicase; mitochondrial antiviral signaling molecule
Vascular endothelial growth factor (VEGF) is a potent regulator of angiogenesis, and its role in cancer biology has been widely studied. Many cancer therapies target angiogenesis, with a focus being on VEGF-mediated signaling such as antibodies to VEGF. However, it is difficult to predict the effects of VEGF-neutralizing agents. We have developed a whole-body model of VEGF kinetics and transport under pathological conditions (in the presence of breast tumor). The model includes two major VEGF isoforms VEGF121 and VEGF165, receptors VEGFR1, VEGFR2 and co-receptors Neuropilin-1 and Neuropilin-2. We have added receptors on parenchymal cells (muscle fibers and tumor cells), and incorporated experimental data for the cell surface density of receptors on the endothelial cells, myocytes, and tumor cells. The model is applied to investigate the action of VEGF-neutralizing agents (called "anti-VEGF") in the treatment of cancer.
Through a sensitivity study, we examine how model parameters influence the level of free VEGF in the tumor, a measure of the response to VEGF-neutralizing drugs. We investigate the effects of systemic properties such as microvascular permeability and lymphatic flow, and of drug characteristics such as the clearance rate and binding affinity. We predict that increasing microvascular permeability in the tumor above 10-5 cm/s elicits the undesired effect of increasing tumor interstitial VEGF concentration beyond even the baseline level. We also examine the impact of the tumor microenvironment, including receptor expression and internalization, as well as VEGF secretion. We find that following anti-VEGF treatment, the concentration of free VEGF in the tumor can vary between 7 and 233 pM, with a dependence on both the density of VEGF receptors and co-receptors and the rate of neuropilin internalization on tumor cells. Finally, we predict that free VEGF in the tumor is reduced following anti-VEGF treatment when VEGF121 comprises at least 25% of the VEGF secreted by tumor cells.
This study explores the optimal drug characteristics required for an anti-VEGF agent to have a therapeutic effect and the tumor-specific properties that influence the response to therapy. Our model provides a framework for investigating the use of VEGF-neutralizing drugs for personalized medicine treatment strategies.
Neuropilin 1 (NP1) is a part of essential receptor complexes mediating both semaphorin3A (SEMA3A) and vascular endothelial growth factor (VEGF) which is one of important mediators involved in the pathogenesis of asthma. Therefore, it is possible that SEMA3A plays a role in the pathogenesis of asthma through attenuation of VEGF-mediated effects. In the present study, we aimed to evaluate expression levels of SEMA3A and NP1 using induced sputum of asthmatics and a murine model of asthma. Firstly, SEMA3A and NP1 expressions in induced sputum of asthmatics and SEMA3A and NP1 expression on bronchoalveolar lavage (BAL) cells and lung homogenates of asthmatic mice were determined. Then we evaluated the immunolocalization of VEGF receptor 1 (VEGFR1), VEGF receptor 2 (VEGFR2), and NP1 expressions on asthmatic mice lung tissue and their subcellular distributions using fibroblast and BEAS2B cell lines. Sputum SEMA3A and NP1 expressions were significantly higher in asthmatics than controls. Similarly, SEMA3A and NP1 expressions on BAL cells and lung homogenates were significantly elevated in asthmatic mice compared to control mice. Immunohistochemical analysis showed that VEGFR1, VEGFR2, and NP1 expressions were also uniformly increased in asthmatic mice. Our observations suggest that SEMA3A and NP1 may play important roles in the pathogenesis of asthma.
Asthma; Neuropilin; Semaphorin-3A (SEMA3A); Vascular Endothelial Growth Factor
There are conflicting data on the effects of vascular endothelial growth factor (VEGF) in vascular remodeling. Furthermore, there are species-specific differences in leukocyte and vascular cell biology and little is known about the role of VEGF in remodeling of human arteries.
We sought to address the role of VEGF blockade on remodeling of human arteries in vivo.
Methods and Results
We used an anti-VEGF antibody, bevacizumab, to study the effect of VEGF blockade on remodeling of human coronary artery transplants in severe combined immunodeficient mice. Bevacizumab ameliorated peripheral blood mononuclear cell (PBMC)-, but not interferon-γ-, induced neointimal formation. This inhibitory effect was associated with a reduction in graft T cell accumulation without affecting T cell activation. VEGF enhanced T cell capture by activated endothelium under flow conditions. The VEGF effect could be recapitulated when a combination of recombinant ICAM-1 and VCAM-1, rather than endothelial cells, was used to capture T cells. A subpopulation of CD3+ T cells expressed VEGF receptor (VEGFR)-1 by immunostaining and FACS analysis. VEGFR-1 mRNA was also detectable in purified CD4+ T cells and Jurkat and HSB-2 T cell lines. Stimulation of HSB-2 and T cells with VEGF triggered downstream ERK phosphorylation, demonstrating the functionality of VEGFR-1 in human T cells.
VEGF contributes to vascular remodeling in human arteries through a direct effect on human T cells that enhances their recruitment to the vessel. These findings raise the possibility of novel therapeutic approaches to vascular remodeling based on inhibition of VEGF signaling.
Vascular endothelial growth factor; Bevacizumab; Vascular remodeling; Transplantation; T lymphocytes
The anti-inflammatory action of silver nanoparticles (NPs) has been reported in a murine model of asthma in a previous study. But more specific mechanisms of silver NPs in an attenuation of allergic airway inflammation have not yet been established. Vascular and mucous changes are believed to contribute largely in pathophysiology in asthma. Among various factors related to vascular changes, vascular endothelial growth factor (VEGF) plays a pivotal role in vascular changes in asthma. Mucin proteins MUC5AC and MUC5B have been implicated as markers of goblet cell metaplasia in lung pathologies. The aim of this study was to investigate the effects of silver NPs on VEGF signaling pathways and mucus hypersecretion. Ovalbumin (OVA)-inhaled female BALBc mice were used to evaluate the role of silver NPs and the related molecular mechanisms in allergic airway disease. In this study, with an OVA-induced murine model of allergic airway disease, it was found that the increased levels of hypoxia-inducible factor (HIF)-1α, VEGF, phosphatidylinositol-3 kinase (PI3K) and phosphorylated-Akt levels, and mucous glycoprotein expression (Muc5ac) in lung tissues were substantially decreased by the administration of silver NPs. In summary, silver NPs substantially suppressed mucus hypersecretion and PI3K/HIF-1α/VEGF signaling pathway in an allergic airway inflammation.
allergic airway disease; hypoxia inducible factor-1α; vascular endothelial growth factor
Vascular endothelial growth factor (VEGF) is well characterized for its role in endothelial cell differentiation and vascular tube formation. Alternate splicing of the VEGF gene in mice results in various VEGF-A isoforms, including VEGF-121 and VEGF-165. VEGF-165 is the most abundant isoform in the kidney and has been implicated in glomerulogenesis. However, its role in the tubular epithelium is not known. We demonstrate that VEGF-165 but not VEGF-121 induces single-cell branching morphogenesis and multicellular tubulogenesis in mouse renal tubular epithelial cells and that these morphogenic effects require activation of the phosphatidylinositol 3-kinase (PI 3-K) and, to a lesser degree, the extracellular signal-regulated kinase and protein kinase C signaling pathways. Further, VEGF-165-stimulated sheet migration is dependent only on PI 3-K signaling. These morphogenic effects of VEGF-165 require activation of both VEGF receptor 2 (VEGFR-2) and neuropilin-1 (Nrp-1), since neutralizing antibodies to either of these receptors or the addition of semaphorin 3A (which blocks VEGF-165 binding to Nrp-1) prevents the morphogenic response and the phosphorylation of VEGFR-2 along with the downstream signaling. We thus conclude that in addition to endothelial vasculogenesis, VEGF can induce renal epithelial cell morphogenesis in a Nrp-1-dependent fashion.
There is significant evidence that Th2 (T helper 2)-mediated inflammation supports the pathogenesis of both human and experimental animal models of pulmonary hypertension (PH). A key immune regulator is vascular endothelial growth factor (VEGF), which is produced by Th2 inflammation and can itself contribute to Th2 pulmonary responses. In this study, we interrogated the role of VEGF signaling in a murine model of schistosomiasis-induced PH with a phenotype of significant intrapulmonary Th2 inflammation, vascular remodeling, and elevated right ventricular pressures. We found that VEGF receptor blockade partially suppressed the levels of the Th2 inflammatory cytokines interleukin (IL)-4 and IL-13 in both the lung and the liver after Schistosoma mansoni exposure and suppressed pulmonary vascular remodeling. These findings suggest that VEGF positively contributes to schistosomiasis-induced vascular inflammation and remodeling, and they also provide evidence for a VEGF-dependent signaling pathway necessary for pulmonary vascular remodeling and inflammation in this model.
pulmonary hypertension; inflammation; VEGF; schistosomiasis
In recent years, there has been increased interest in the vascular component of airway remodelling in chronic bronchial inflammation, such as asthma and COPD, and in its role in the progression of disease. In particular, the bronchial mucosa in asthmatics is more vascularised, showing a higher number and dimension of vessels and vascular area. Recently, insight has been obtained regarding the pivotal role of vascular endothelial growth factor (VEGF) in promoting vascular remodelling and angiogenesis. Many studies, conducted on biopsies, induced sputum or BAL, have shown the involvement of VEGF and its receptors in the vascular remodelling processes. Presumably, the vascular component of airway remodelling is a complex multi-step phenomenon involving several mediators. Among the common asthma and COPD medications, only inhaled corticosteroids have demonstrated a real ability to reverse all aspects of vascular remodelling. The aim of this review was to analyze the morphological aspects of the vascular component of airway remodelling and the possible mechanisms involved in asthma and COPD. We also focused on the functional and therapeutic implications of the bronchial microvascular changes in asthma and COPD.
Type 2 diabetes (T2D) results from insulin resistance and inadequate insulin secretion. Insulin resistance initially causes compensatory islet hyperplasia that progresses to islet disorganization and altered vascularization, inflammation, and, finally, decreased functional β-cell mass and hyperglycemia. The precise mechanism(s) underlying β-cell failure remain to be elucidated. In this study, we show that in insulin-resistant high-fat diet-fed mice, the enhanced islet vascularization and inflammation was parallel to an increased expression of vascular endothelial growth factor A (VEGF). To elucidate the role of VEGF in these processes, we have genetically engineered β-cells to overexpress VEGF (in transgenic mice or after adeno-associated viral vector-mediated gene transfer). We found that sustained increases in β-cell VEGF levels led to disorganized, hypervascularized, and fibrotic islets, progressive macrophage infiltration, and proinflammatory cytokine production, including tumor necrosis factor-α and interleukin-1β. This resulted in impaired insulin secretion, decreased β-cell mass, and hyperglycemia with age. These results indicate that sustained VEGF upregulation may participate in the initiation of a process leading to β-cell failure and further suggest that compensatory islet hyperplasia and hypervascularization may contribute to progressive inflammation and β-cell mass loss during T2D.
The alternative splice form of VEGF, VEGF-A165b, inhibits choroidal neovascularization at very low doses in mice, indicating that it may be an effective therapy for age-related macular degeneration, comparable with or better than existing anti-VEGF therapy.
Vascular endothelial growth factor (VEGF-A) is the principal stimulator of angiogenesis in wet age-related macular degeneration (AMD). However, VEGF-A is generated by alternate splicing into two families, the proangiogenic VEGF-Axxx family and the antiangiogenic VEGF-Axxxb family. It is the proangiogenic family that is responsible for the blood vessel growth seen in AMD.
To determine the role of antiangiogenic isoforms of VEGF-A as inhibitors of choroidal neovascularization, the authors used a model of laser-induced choroidal neovascularization in the mouse eye and investigated VEGF-A165b effects on endothelial cells and VEGFRs in vitro.
VEGF-A165b inhibited VEGF-A165–mediated endothelial cell migration with a dose effect similar to that of ranibizumab and bevacizumab and 200-fold more potent than that of pegaptanib. VEGF-A165b bound both VEGFR1 and VEGFR2 with affinity similar to that of VEGF-A165. After laser injury, mice were injected either intraocularly or subcutaneously with recombinant human VEGF-A165b. Intraocular injection of rhVEGF-A165b gave a pronounced dose-dependent inhibition of fluorescein leakage, with an IC50 of 16 pg/eye, neovascularization (IC50, 0.8 pg/eye), and lesion as assessed by histologic staining (IC50, 8 pg/eye). Subcutaneous administration of 100 μg twice a week also inhibited fluorescein leakage and neovascularization and reduced lesion size.
These results show that VEGF-A165b is a potent antiangiogenic agent in a mouse model of age-related macular degeneration and suggest that increasing the ratio of antiangiogenic-to-proangiogenic isoforms may be therapeutically effective in this condition.
In cerebral malaria, the binding of parasitized erythrocytes to the cerebral endothelium and the consequent angiogenic dysregulation play a key role in pathogenesis. Because vascular endothelial growth factor (VEGF) is widely regarded as a potent stimulator of angiogenesis, edema, inflammation, and vascular remodeling, the plasma levels of VEGF and the soluble form of the VEGF receptor (sVEGFR)-1 and -2 in uncomplicated malaria patients and healthy adults were measured by enzyme-linked immunosorbent assay (ELISA) to examine their roles in malaria. The results showed that VEGF and sVEGFR-2 levels were significantly elevated in malaria patients compared with healthy adults. Moreover, it was confirmed that malarial parasite antigens induced VEGF secretion from the human mast cell lines HMC-1 or KU812 cell. This is the first report to suggest that the interaction of VEGF and sVEGFR-2 is involved in the host immune response to malarial infection and that malarial parasites induce VEGF secretion from human mast cells.
Skeletal muscle overload induces the expression of angiogenic factors such as vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP)-2, leading to new capillary growth. We found that the overload-induced increase in angiogenesis, as well as increases in VEGF, MMP-2 and MT1-MMP transcripts were abrogated in muscle VEGF KO mice, highlighting the critical role of myocyte-derived VEGF in controlling this process. The upstream mediators that contribute to overload-induced expression of VEGF have yet to be ascertained. We found that muscle overload increased angiotensinogen expression, a precursor of angiotensin (Ang) II, and that Ang II signaling played an important role in basal VEGF production in C2C12 cells. Furthermore, matrix-bound VEGF released from myoblasts induced the activation of endothelial cells, as evidenced by elevated endothelial cell phospho-p38 levels. We also found that exogenous Ang II elevates VEGF expression, as well as MMP-2 transcript levels in C2C12 myotubes. Interestingly, these responses also were observed in skeletal muscle endothelial cells in response to Ang II treatment, indicating that these cells also can respond directly to the stimulus. The involvement of Ang II in muscle overload-induced angiogenesis was assessed. We found that blockade of AT1R-dependent Ang II signaling using losartan did not attenuate capillary growth. Surprisingly, increased levels of VEGF protein were detected in overloaded muscle from losartan-treated rats. Similarly, we observed elevated VEGF production in cultured endothelial cells treated with losartan alone or in combination with Ang II. These studies conclusively establish the requirement for muscle derived VEGF in overload-induced angiogenesis and highlight a role for Ang II in basal VEGF production in skeletal muscle. However, while Ang II signaling is activated following overload and plays a role in muscle VEGF production, inhibition of this pathway is not sufficient to halt overload-induced angiogenesis, indicating that AT1-independent signals maintain VEGF production in losartan-treated muscle.
High-permeability pulmonary edema causing acute respiratory distress syndrome is associated with high mortality. Using a model of intratracheal adenovirus (Ad)-mediated overexpression of human vascular endothelial growth factor (VEGF)-A165 in mouse lung to induce alveolar permeability and consequent pulmonary edema, we hypothesized that systemic administration of a second adenoviral vector expressing an anti-VEGF antibody (AdαVEGFAb) would protect the lung from pulmonary edema. Pulmonary edema was induced in mice by intratracheal administration of AdVEGFA165. To evaluate anti-VEGF antibody therapy, the mice were treated intravenously with AdαVEGFAb, an adenoviral vector encoding the light and heavy chains of an anti-human VEGF antibody with the bevacizumab (Avastin) antigen-binding site. Lung VEGF-A165 and phosphorylated VEGF receptor (VEGFR)-2 levels, histology, lung wet-to-dry weight ratios, and bronchoalveolar lavage fluid (BALF) levels of total protein were assessed. Administration of AdαVEGFAb to mice decreased AdVEGFA165-induced levels of human VEGF-A165 and phosphorylated VEGFR-2 in the lung. Histological analysis of AdαVEGFAb-treated mice demonstrated a reduction of edema fluid in the lung tissue that correlated with a reduction of lung wet-to-dry ratios and BALF total protein levels. Importantly, administration of AdαVEGFAb 48 hr after induction of pulmonary edema with AdVEGFA165 was effective in suppressing pulmonary edema. Administration of an adenoviral vector encoding an anti-VEGF antibody that is the equivalent of bevacizumab effectively suppresses VEGF-A165-induced high-permeability pulmonary edema, suggesting that anti-VEGF antibody therapy may represent a novel therapy for high-permeability pulmonary edema.
Rationale: Vascular endothelial growth factor (VEGF) regulates vascular, inflammatory, remodeling, and cell death responses. It plays a critical role in normal pulmonary physiology, and VEGF excess and deficiency have been implicated in the pathogenesis of asthma and chronic obstructive pulmonary disease, respectively. Although viruses are an important cause of chronic obstructive pulmonary disease exacerbations and innate responses play an important role in these exacerbations, the effects of antiviral responses on VEGF homeostasis have not been evaluated.
Objectives: We hypothesized that antiviral innate immunity regulates VEGF tissue responses.
Methods: We compared the effects of transgenic VEGF165 in mice treated with viral pathogen–associated molecular pattern polyinosinic:polycytidylic acid [poly(I:C)], mice treated with live virus, and control mice.
Measurements and Main Results: Transgenic VEGF stimulated angiogenesis, edema, inflammation, and mucin accumulation. Each of these was abrogated by poly(I:C). These inhibitory effects were dose dependent, noted when poly(I:C) was administered before and after transgene activation, and mediated by a Toll-like receptor-3–independent and RIG-like helicase (RLH)– and type I IFN receptor–dependent pathway. VEGF stimulated the expression of VEGF receptor-1 and poly(I:C) inhibited this stimulation. Poly(I:C) also inhibited the ability of VEGF to activate extracellular signal–regulated kinase-1, Akt, focal adhesion kinase, and endothelial nitric oxide synthase, and aeroallergen-induced adaptive helper T-cell type 2 inflammation. Influenza and respiratory syncytial virus also inhibited VEGF-induced angiogenesis.
Conclusions: These studies demonstrate that poly(I:C) and respiratory viruses inhibit VEGF-induced tissue responses and adaptive helper T-cell type 2 inflammation and highlight the importance of a RLH- and type I IFN receptor–dependent pathway(s) in these regulatory events. They define a novel link between VEGF and antiviral and RLH innate immune responses and a novel pathway that regulates pulmonary VEGF activity.
RIG-like helicase; mitochondrial antiviral signaling molecule; influenza virus; chronic obstructive pulmonary disease
Vascular Endothelial Growth Factor (VEGF), a key angiogenic molecule, is aberrantly expressed in several diseases including asthma where it contributes to bronchial vascular remodelling and chronic inflammation. Asthmatic human airway smooth muscle (HASM) cells hypersecrete VEGF but the mechanism is unclear. Here we defined the mechanism in HASM cells from non-asthmatic (NA) and asthmatic (A) patients. We found that asthmatic cells lacked a repression complex at the VEGF promoter which was present in non-asthmatic cells. Recruitment of G9A, trimethylation of histone H3 at lysine 9 (H3K9me3) and a resultant decrease in RNA polymerase II (RNA pol II) at the VEGF promoter was critical to repression of VEGF secretion in non-asthmatic cells. At the asthmatic promoter H3K9me3 was absent due to failed recruitment of G9a; RNA pol II binding, in association with TAF1, was increased, H3K4me3 was present and Sp1 binding was exaggerated and sustained. In contrast DNA methylation and histone acetylation were similar in A and NA cells. This is the first study to show that airway cells in asthma have altered epigenetic regulation of remodelling gene(s). Histone methylation at genes such as VEGF may be an important new therapeutic target.
Angiogenesis and lymphangiogenesis mediated by vascular endothelial growth factors (VEGFs) are main features of chronic inflammation and tumors. Secreted phospholipases A2 (sPLA2s) are overexpressed in inflammatory lung diseases and cancer and they activate inflammatory cells by enzymatic and receptor-mediated mechanisms. We investigated the effect of sPLA2s on the production of VEGFs from human macrophages purified from the lung tissue of patients undergoing thoracic surgery. Primary macrophages express VEGF-A, VEGF-B, VEGF-C, and VEGF-D at both mRNA and protein level. Two human sPLA2s (group IIA and group X) induced the expression and release of VEGF-A and VEGF-C from macrophages. Enzymatically-inactive sPLA2s were as effective as the active enzymes in inducing VEGF production. Me-Indoxam and RO092906A, two compounds that block receptor-mediated effects of sPLA2s, inhibited group X-induced release of VEGF-A. Inhibition of the MAPK p38 by SB203580 also reduced sPLA2-induced release of VEGF-A. Supernatants of group X-activated macrophages induced an angiogenic response in chorioallantoic membranes that was inhibited by Me-Indoxam. Stimulation of macrophages with group X sPLA2 in the presence of adenosine analogs induced a synergistic increase of VEGF-A release and inhibited TNF-α production through a cooperation between A2A and A3 receptors. These results demonstrate that sPLA2s induce production of VEGF-A and VEGF-C in human macrophages by a receptor-mediated mechanism independent from sPLA2 catalytic activity. Thus, sPLA2s may play an important role in inflammatory and/or neoplastic angiogenesis and lymphangiogenesis.
Tyrosine kinase receptors for angiogenic factors vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) are expressed not only by endothelial cells but also by subsets of hematopoietic stem cells (HSCs). To further define their role in the regulation of postnatal hematopoiesis and vasculogenesis, VEGF and Ang-1 plasma levels were elevated by injecting recombinant protein or adenoviral vectors expressing soluble VEGF165, matrix-bound VEGF189, or Ang-1 into mice. VEGF165, but not VEGF189, induced a rapid mobilization of HSCs and VEGF receptor (VEGFR)2+ circulating endothelial precursor cells (CEPs). In contrast, Ang-1 induced delayed mobilization of CEPs and HSCs. Combined sustained elevation of Ang-1 and VEGF165 was associated with an induction of hematopoiesis and increased marrow cellularity followed by proliferation of capillaries and expansion of sinusoidal space. Concomitant to this vascular remodeling, there was a transient depletion of hematopoietic activity in the marrow, which was compensated by an increase in mobilization and recruitment of HSCs and CEPs to the spleen resulting in splenomegaly. Neutralizing monoclonal antibody to VEGFR2 completely inhibited VEGF165, but not Ang-1–induced mobilization and splenomegaly. These data suggest that temporal and regional activation of VEGF/VEGFR2 and Ang-1/Tie-2 signaling pathways are critical for mobilization and recruitment of HSCs and CEPs and may play a role in the physiology of postnatal angiogenesis and hematopoiesis.
vascular endothelial growth factor; angiopoietin-1; angiogenesis; hematopoiesis; tyrosine kinase receptors
Vascular endothelial growth factor (VEGF) is supposed to contribute to the pathogenesis of allergic airway disease. VEGF expression is regulated by a variety of stimuli such as nitric oxide, growth factors, and hypoxia-inducible factor-1 alpha (HIF-1α). Recently, inhibition of the mammalian target of rapamycin (mTOR) has been shown to alleviate cardinal asthmatic features, including airway hyperresponsiveness, eosinophilic inflammation, and increased vascular permeability in asthma models. Based on these observations, we have investigated whether mTOR is associated with HIF-1α-mediated VEGF expression in allergic asthma. In studies with the mTOR inhibitor rapamycin, we have elucidated the stimulatory role of a mTOR-HIF-1α-VEGF axis in allergic response. Next, the mechanisms by which mTOR is activated to modulate this response have been evaluated. mTOR is known to be regulated by phosphoinositide 3-kinase (PI3K)/Akt or protein kinase C-delta (PKC δ) in various cell types. Consistent with these, our results have revealed that suppression of PKC δ by rottlerin leads to the inhibition of PI3K/Akt activity and the subsequent blockade of a mTOR-HIF-1α-VEGF module, thereby attenuating typical asthmatic attack in a murine model. Thus, the present data indicate that PKC δ is necessary for the modulation of the PI3K/Akt/mTOR signaling cascade, resulting in a tight regulation of HIF-1α activity and VEGF expression. In conclusion, PKC δ may represent a valuable target for innovative therapeutic treatment of allergic airway disease.
The endogenous role of the VEGF family member vascular endothelial growth factor-B (VEGF-B) in pathological angiogenesis remains unclear.
Methods and Results
We studied the role of VEGF-B in various models of pathological angiogenesis using mice lacking VEGF-B (VEGF-B−/−) or overexpressing VEGF-B167. After occlusion of the left coronary artery, VEGF-B deficiency impaired vessel growth in the ischemic myocardium whereas, in wild-type mice, VEGF-B167 overexpression enhanced revascularization of the infarct and ischemic border zone. By contrast, VEGF-B deficiency did not affect vessel growth in the wounded skin, hypoxic lung, ischemic retina, or ischemic limb. Moreover, VEGF-B167 overexpression failed to enhance vascular growth in the skin or ischemic limb.
VEGF-B appears to have a relatively restricted angiogenic activity in the ischemic heart. These insights might offer novel therapeutic opportunities.
VEGF-B; angiogenesis; arteriogenesis; collateral growth; cardiac ischemia; limb ischemia
Angiogenesis and vascular regression are critical for the female ovulatory cycle.
They enable progression and regression of follicular development, and corpora
lutea formation and regression. Angiogenesis in the ovary occurs under the
control of the vascular endothelial growth factor-A (VEGFA) family of proteins,
which are generated as both pro-(VEGF165) and
anti(VEGF165b)-angiogenic isoforms by alternative splicing. To
determine the role of the VEGF165b isoforms in the ovulatory cycle,
we measured VEGF165b expression in marmoset ovaries by
immunohistochemistry and ELISA, and used transgenic mice over-expressing
VEGF165b in the ovary. VEGF165b was expressed in the
marmoset ovaries in granulosa cells and theca, and the balance of
VEGF165b:VEGF165 was regulated during luteogenesis.
Mice over-expressing VEGF165b in the ovary were less fertile than
wild-type littermates, had reduced secondary and tertiary follicles after
mating, increased atretic follicles, fewer corpora lutea and generated fewer
embryos in the oviduct after mating, and these were more likely not to retain
the corona radiata. These results indicate that the balance of VEGFA isoforms
controls follicle progression and luteogenesis, and that control of isoform
expression may regulate fertility in mammals, including in primates.
Epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), the AA and BB isoforms of platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) are involved in the pathogenesis of airway inflammation in asthma. In the present study, the associations between asthmatic phenotypes and the expression levels of these mediators in induced sputum and serum were investigated. A total of 62 asthmatic patients were divided into eosinophilic or neutrophilic phenotypes by cytological classification of the induced sputum. In addition, patients were classified according to lung function (FEV1/FVC >70% or FEV1/FVC <70%) and asthma severity (mild, moderate or severe). The concentrations of EGF, bFGF, PDGF-AA, PDGF-BB and VEGF in the serum and induced sputum were measured using sandwich enzyme immunoassays. VEGF levels in the serum and induced sputum were higher in patients with an eosinophilic phenotype compared with those with a neutrophilic phenotype. In addition, VEGF expression was higher in patients with an FEV1/FVC value of <70% as compared with patients with an FEV1/FVC value of >70%. Furthermore, the levels of VEGF were higher in patients with severe asthma compared with the patients with mild and moderate asthma. There were no statistically significant differences observed with regard to EGF, bFGF, PDGF-AA and PDGF-BB levels among the various phenotypes. Therefore, the observations of the present study indicated that increased VEGF expression in the serum and induced sputum of patients may be associated with eosinophilic airway inflammation, severe airflow limitation and the severity of asthma.
asthma; phenotype; epidermal growth factor; basic fibroblast growth factor; platelet-derived growth factor; vascular endothelial growth factor
Vascular endothelial growth factor (VEGF), a substance that stimulates new blood vessel formation, is an important survival factor for endothelial cells. Although overexpressed VEGF in the lung induces pulmonary edema with increased lung vascular permeability, the role of VEGF in the development of acute lung injury remains to be determined.
To evaluate the role of VEGF in the pathogenesis of acute lung injury, we first evaluated the effects of exogenous VEGF and VEGF blockade using monoclonal antibody on LPS-induced lung injury in mice. Using the lung specimens, we performed TUNEL staining to detect apoptotic cells and immunostaining to evaluate the expression of apoptosis-associated molecules, including caspase-3, Bax, apoptosis inducing factor (AIF), and cytochrome C. As a parameter of endothelial permeability, we measured the albumin transferred across human pulmonary artery endothelial cell (HPAEC) monolayers cultured on porous filters with various concentrations of VEGF. The effect of VEGF on apoptosis HPAECs was also examined by TUNEL staining and active caspase-3 immunoassay.
Exogenous VEGF significantly decreased LPS-induced extravascular albumin leakage and edema formation. Treatment with anti-VEGF antibody significantly enhanced lung edema formation and neutrophil emigration after intratracheal LPS administration, whereas extravascular albumin leakage was not significantly changed by VEGF blockade. In lung pathology, pretreatment with VEGF significantly decreased the numbers of TUNEL positive cells and those with positive immunostaining of the pro-apoptotic molecules examined. VEGF attenuated the increases in the permeability of the HPAEC monolayer and the apoptosis of HPAECs induced by TNF-α and LPS. In addition, VEGF significantly reduced the levels of TNF-α- and LPS-induced active caspase-3 in HPAEC lysates.
These results suggest that VEGF suppresses the apoptosis induced by inflammatory stimuli and functions as a protective factor against acute lung injury.
Vascular endothelial growth factor (VEGF) is known to have a pivotal role in lung development and in a variety of pathologic conditions in the adult lung. Our earlier studies have shown that NO is a critical mediator of VEGF-induced vascular and extravascular effects in the adult murine lung. As significant differences have been reported in the cytokine responses in the adult versus the neonatal lung, we hypothesized that there may be significant differences in VEGF-induced alterations in the developing as opposed to the mature lung. Furthermore, nitric oxide (NO) mediation of these VEGF-induced effects may be developmentally regulated. Using a novel externally regulatable lung-targeted transgenic murine model, we found that VEGF-induced pulmonary hemorrhage was mediated by NO-dependent mechanisms in adults and newborns. VEGF enhanced surfactant production in adults as well as increased surfactant and lung development in newborns, via an NO-independent mechanism. While the enhanced survival in hyperoxia in the adult was partly NO-dependent, there was enhanced hyperoxia-induced lung injury in the newborn. In addition, human amniotic fluid VEGF levels correlated positively with surfactant phospholipids. Tracheal aspirate VEGF levels had an initial spike, followed by a decline, and then a subsequent rise, in human neonates with an outcome of bronchopulmonary dysplasia or death. Our data show that VEGF can have injurious as well as potentially beneficial developmental effects, of which some are NO dependent, others NO independent. This opens up the possibility of selective manipulation of any VEGF-based intervention using NO inhibitors for maximal potential clinical benefit.
vascular endothelial growth factor; nitric oxide; lung; surfactant
VEGF dampens the expression of microRNA-1, which drives inflammation in part via increasing the expression of Mpl.
Asthma, the prototypic Th2-mediated inflammatory disorder of the lung, is an emergent disease worldwide. Vascular endothelial growth factor (VEGF) is a critical regulator of pulmonary Th2 inflammation, but the underlying mechanism and the roles of microRNAs (miRNAs) in this process have not been defined. Here we show that lung-specific overexpression of VEGF decreases miR-1 expression in the lung, most prominently in the endothelium, and a similar down-regulation occurs in lung endothelium in Th2 inflammation models. Intranasal delivery of miR-1 inhibited inflammatory responses to ovalbumin, house dust mite, and IL-13 overexpression. Blocking VEGF inhibited Th2-mediated lung inflammation, and this was restored by antagonizing miR-1. Using mRNA arrays, Argonaute pull-down assays, luciferase expression assays, and mutational analysis, we identified Mpl as a direct target of miR-1 and showed that VEGF controls the expression of endothelial Mpl during Th2 inflammation via the regulation of miR-1. In vivo knockdown of Mpl inhibited Th2 inflammation and indirectly inhibited the expression of P-selectin in lung endothelium. These experiments define a novel VEGF–miR-1–Mpl–P-selectin effector pathway in lung Th2 inflammation and herald the utility of miR-1 and Mpl as potential therapeutic targets for asthma.
Vascular endothelial growth factor (VEGF-A or VEGF) is a major pathogenic factor and therapeutic target for diabetic retinopathy (DR). Since VEGF has been proposed as a survival factor for retinal neurons, defining the cellular origin of pathogenic VEGF is necessary for the effectiveness and safety of long-term anti-VEGF therapies for DR. To determine the significance of Müller cell-derived VEGF in DR, we disrupted VEGF in Müller cells with an inducible Cre/lox system and examined diabetes-induced retinal inflammation and vascular leakage in these conditional VEGF knockout (KO) mice.
RESEARCH DESIGN AND METHODS
Leukostasis was determined by counting the number of fluorescently labeled leukocytes inside retinal vasculature. Expression of biomarkers for retinal inflammation was assessed by immunoblotting of TNF-α, ICAM-1, and NF-κB. Vascular leakage was measured by immunoblotting of retinal albumin and fluorescent microscopic analysis of extravascular albumin. Diabetes-induced vascular alterations were examined by immunoblotting and immunohistochemistry for tight junctions, and by trypsin digestion assays for acellular capillaries. Retinal integrity was analyzed with morphologic and morphometric analyses.
Diabetic conditional VEGF KO mice exhibited significantly reduced leukostasis, expression of inflammatory biomarkers, depletion of tight junction proteins, numbers of acellular capillaries, and vascular leakage compared to diabetic control mice.
Müller cell-derived VEGF plays an essential and causative role in retinal inflammation, vascular lesions, and vascular leakage in DR. Therefore, Müller cells are a primary cellular target for proinflammatory signals that mediates retinal inflammation and vascular leakage in DR.