Receptor Vascular Endothelial Growth Factor Receptor-2 Research Articles

Molecular Docking and Dynamic Simulation of Erythrina fusca Lour Chemical Compounds Targeting VEGFR-2 Receptor for Anti-Liver Cancer Activity

Liver cancer is a serious health concern characterized by abnormal cell growth, but currently, available treatment options are limited, suggesting the need for a new therapeutic method. Therefore, this research aimed to investigate the potential of chemical compounds obtained from the cangkring plant (Erythrina fusca) as anti-liver cancer agents targeting Vascular Endothelial Growth Factor Receptor 2 (VEGFR-2). The investigation was conducted in silico through molecular docking and dynamic method. Molecular docking was performed using AutoDock Tools, followed by visualization with Biovia Discovery Studio. Additionally, molecular dynamics simulation was conducted using GROMACS software and visualized with Grace. A total of 36 chemical compounds from E. fusca were used as ligands for molecular docking. The results showed that Isobavachalcone (ISB) was the most effective test compound with a binding energy of -11.45 kcal/mol, compared to the positive control Sorafenib with a value of - 11.51 kcal/mol. In this context, hydrogen bonding, as well as hydrophobic, electrostatic, and unfavorable molecular interactions were identified. Moreover, molecular dynamics simulation provided RMSD, RMSF, Radius of Gyration (Rg), and hydrogen bond parameters. Analysis of these parameters further confirmed the superior stability of ISB in binding to VEGFR-2, suggesting the potential to suppress angiogenesis by blocking the receptor.

Evaluation of in silico anticancer activity of some striazine derivatives as VEGFR2 inhibitors

The s-triazine derivatives have been shown to have diverse biological activities, especially anticancer activity. Fifty s-triazine derivatives were screened for anticancer activity through inhibition of VEGFR2 (vascular endothelial growth factor receptor-2) by molecular docking method using AutoDock Vina software. Compounds 20 and 40 showed the strongest interactions among all tested compounds with the binding affinity values of -10.8 and -10.5 Kcal/mol, respectively compared to reference drugs Gedatolisib (-9.1 Kcal/mol) and Paclitaxel (-7.8 Kcal/mol) at the active site of VEGFR2. These compounds established one carbon-hydrogen bond at amino acid HIS1026, specifically exhibiting better electrostatic and hydrophobic interactions than the reference drugs Gedatolisib and Paclitaxel. Moreover, compounds 20 and 40 also showed interactions with the VEGFR2 receptor that resemble the reference drug Gedatolisib at amino acids such as ARG1027, ASP1046, and HIS1026. Therefore, these compounds could be a potential lead molecule for anticancer activity.

Albendazole repurposing on VEGFR-2 for possible anticancer application: In-silico analysis.

Drug repurposing is the finding new activity of the existing drug. Recently, Albendazole's well-known antihelmintic has got the attention of an anticancer drug. Plausible evidence of the interaction of Albendazole with one of the types of tyrosine kinase protein receptor, vascular endothelial growth factor receptor-2 (VEGFR-2) is still not well understood. Inhibition of the VEGFR-2 receptor can prevent tumor growth. The current study investigated the interaction of Albendazole with VEGFR-2.It was found that the said interaction exhibited potent binding energy ΔG = -7.12 kcal/mol, inhibitory concentration (Ki) = 6.04 μM, and as positive control comparison with standard drug (42Q1170A) showed ΔG = -12.35 kcal/mol and Ki = 881 μM. The key residue Asp1046 was formed involved hydrogen bonding with Albendazole. The molecular dynamics simulation study revealed the stable trajectory of the VEGFR-2 receptor with Albendazole bound complex having significant high free energy of binding as calculated from Molecular Mechanics Generalized Born and Surface Area study ΔG = -42.07±2.4 kcal/mol. The binding energy is significantly high for greater stability of the complex. Principal component analysis of molecular docking trajectories exhibited ordered motion at higher modes, implying a high degree of VEGFR-2 and Albendazole complex stability as seen with the standard drug 42Q. Therefore, the current work suggests the role of Albendazole as a potent angiogenesis inhibitor as ascertained by its potential interaction with VEGFR-2. The findings of research will aid in the future development of Albendazole in anticancer therapy.

Placental growth factor stabilizes VEGF receptor-2 protein in retinal pigment epithelial cells by downregulating glycogen synthase kinase 3 activity

Placental growth factor (PlGF) belongs to the vascular endothelial growth factor (VEGF) family of proteins that participate in angiogenesis and vasculogenesis. Anti-VEGF therapy has become the standard treatment for ocular angiogenic disorders in ophthalmological practice. However, there is emerging evidence that anti-VEGF treatment may increase the risk of atrophy of the retinal pigment epithelium (RPE), which is important for the homeostasis of retinal tissue. Whereas the cytoprotective role of VEGF family molecules, particularly that of VEGF A (VEGFA) through its receptor VEGF receptor-2 (VEGFR-2), has been recognized, the physiological role of PlGF in the retina is still unknown. In this study, we explored the role of PlGF in the RPE using PlGF-knockdown RPE cells generated by retrovirus-based PlGF-shRNA transduction. We show that VEGFA reduced apoptosis induced by serum starvation in RPE cells, whereas the antiapoptotic effect of VEGFA was abrogated by VEGFR-2 knockdown. Furthermore, PlGF knockdown increased serum starvation–induced cell apoptosis and unexpectedly reduced the protein level of VEGFR-2 in the RPE. The antiapoptotic effect of VEGFA was also diminished in PlGF-knockdown RPE cells. In addition, we found that glycogen synthase kinase 3 activity was involved in proteasomal degradation of VEGFR-2 in RPE cells and inactivated by PlGF via AKT phosphorylation. Overall, the present data demonstrate that PlGF is crucial for RPE cell viability and that PlGF supports VEGFA/VEGFR-2 signaling by stabilizing the VEGFR-2 protein levels through glycogen synthase kinase 3 inactivation.

Semaphorin 3E promote Schwann cell proliferation and migration

Schwann cells (SCs) play a critical role in peripheral nerve (PN) regeneration because of their ability to proliferate, migrate, and provide trophic support for axon regeneration after PN injury. However, the underlying mechanism is still partially understood. Semaphorin3E (Sema3E), a member of the Sema3s family, is a secreted molecular known as a repelling cue in axon guidance and inhibitor of developmental and postischemic angiogenesis. In this study, we examined the expression of Sema3E in sciatic nerves and SCs and explored the effects of Sema3E on SCs proliferation and migration. Immunofluorescence and ELISA analyses illustrated the expression of Sema3E in SCs of Sciatic nerves and the secretion of Sema3E by cultured SCs, respectively. Exogenous Sema3E promoted SC proliferation and migration while knockdown of the endogenous Sema3E by siRNA transfection attenuated proliferation and migration of SCs. Furthermore, blocking the receptor Neuropilin 1 (Nrp1), PlexinD1 and Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) by neutralizing antibody or inhibitor suppressed the promoting effects of Sema3E on SCs. This study indicated that Sema3E promoted SC proliferation and migration and the involvement of receptor PlexinD1, Nrp1, and VEGFR2 in these processes. This study extended our understanding of the mechanism that modulated SC phenotype during nerve injury and provided a potential target for promoting PN regeneration.

In Silico and In Vitro Studies for Benzimidazole Anthelmintics Repurposing as VEGFR-2 Antagonists: Novel Mebendazole-Loaded Mixed Micelles with Enhanced Dissolution and Anticancer Activity.

Cancer is a leading cause of death worldwide and its incidence is unfortunately anticipated to rise in the next years. On the other hand, vascular endothelial growth factor receptor 2 (VEGFR-2) is highly expressed in tumor-associated endothelial cells, where it affects tumor-promoting angiogenesis. Therefore, VEGFR-2 is considered one of the most promising therapeutic targets for cancer treatment. Furthermore, some FDA-approved benzimidazole anthelmintics have already shown potential anticancer activities. Therefore, repurposing them against VEGFR-2 can provide a rapid and effective alternative that can be implicated safely for cancer treatment. Hence, 13 benzimidazole anthelmintic drugs were subjected to molecular docking against the VEGFR-2 receptor. Among the tested compounds, fenbendazole (FBZ, 1), mebendazole (MBZ, 2), and albendazole (ABZ, 3) were proposed as potential VEGFR-2 antagonists. Furthermore, molecular dynamics simulations were carried out at 200 ns, giving more information on their thermodynamic and dynamic properties. Besides, the anticancer activity of the aforementioned drugs was tested in vitro against three different cancer cell lines, including liver cancer (HUH7), lung cancer (A549), and breast cancer (MCF7) cell lines. The results depicted potential cytotoxic activity especially against both HUH7 and A549 cell lines. Furthermore, to improve the aqueous solubility of MBZ, it was formulated in the form of mixed micelles (MMs) which showed an enhanced drug release with better promising cytotoxicity results compared to the crude MBZ. Finally, an in vitro quantification for VEGFR-2 concentration in treated HUH7 cells has been conducted based on the enzyme-linked immunosorbent assay. The results disclosed that FBZ, MBZ, and ABZ significantly (p < 0.001) reduced the concentration of VEGFR-2, while the lowest inhibition was achieved in MBZ-loaded MMs, which was even much better than the reference drug sorafenib. Collectively, the investigated benzimidazole anthelmintics could be encountered as lead compounds for further structural modifications and thus better anticancer activity, and that was accomplished through studying their structure–activity relationships.

QSAR analysis of pyrimidine derivatives as VEGFR-2 receptor inhibitors to inhibit cancer using multiple linear regression and artificial neural network.

Background and purpose:In this study, the pharmacological activity of 33 compounds of furopyrimidine and thienopyrimidine as vascular endothelial growth factor receptor 2 (VEGFR-2) inhibitors to inhibit cancer was investigated. The most important angiogenesis inducer is VEGF endothelial growth factor, which exerts its activity by binding to two tyrosine kinase receptors called VEGFR-1 and VEGFR-2. Due to the critical role of VEGF in the pathological angiogenesis of this molecule, it is a valuable therapeutic target for anti-angiogenesis therapies.Experimental approach:After calculating descriptors using SPSS software and stepwise selection method, 5 descriptors were used for modeling in multiple linear regression (MLR) and artificial neural network (ANN). The calibration series and the test series in this study included 26 and 7 combinations, respectively.Findings/Results:The performance evaluation of models was determined by the R2, RMSE, and Q2 statistic parameters. The R2 values of MLR and ANN models were 0.889 and 0.998, respectively. Also, the value of RMSE in the ANN model was lower and its Q2 value was higher than the MLR model.Conclusion and implications:The results were evaluated by different statistical methods and it was concluded that the nonlinear neural network method is powerful to predict the pharmacological activity of similar compounds, and because of the complex and nonlinear relationships, the MLR was not capable of establishing a good model with high predictive power.

Identification of tyrosine kinase inhibitors from PanaxbipinnatifidusandPanax pseudoginseng for RTK-HER2 and VEGFR2 receptors, by in silico approach.

Breast and stomach cancer is reported as a leading cause for human mortality across the world. The overexpression of receptor tyrosine kinase (RTK) proteins, namely the human epidermal growth factor receptor2 (HER2) and the vascular endothelial growth factor receptor2 (VEGFR2), is reported to be responsible for development and metastasis of breast and stomach cancer. Although several synthetic tyrosine kinase inhibitors (TKIs) as drug candidates targeting RTK-HER2 and VEGFR2 are currently available in the market, these are expensive with the reported side effects. This confers an opportunity for development of alternative novel tyrosine kinase inhibitors (TKIs) for RTK-HER2 and VEGFR2 receptors from the botanical sources. In the present study, we characterized 47 bioactive phytocompounds from the methanol extracts of the rhizomes of Asiatic traditional medicinal herbs-Panax bipinnatifidus and Panax pseudoginseng, of Indian Himalayan landraces using HPLC, GC-MS and high-sensitivity LC-MS tools. We performed molecular docking and molecular dynamics simulation analysis using Schrödinger suite 2020-3 to confirm the TKI phytocompounds showing the best binding affinity towards RTK-HER2 and VEGFR2 receptors. The results of molecular docking studies confirmed that the phytocompound (ligand) luteolin 7-O-glucoside (IHP15) showed the highest binding affinity towards receptor HER2 (PDB ID: 3PP0) with docking score and Glide g score (G-Score) of -13.272, while chlorogenic acid (IHP12) showed the highest binding affinity towards receptor VEGFR2 (PDB ID: 4AGC) with docking score and Glide g score (G-Score) of -10.673. Molecular dynamics (MD) simulation analysis carried out for 100ns has confirmed strong binding interaction between the ligand and receptor complex [luteolin 7-O-glucoside (IHP15) and HER2 (PDB ID: 3PP0)] and is found to be stabilized within 40 to 100ns of MD simulation, whereas ligand-receptor complex [chlorogenic acid (IPH12) and VEGFR2 (PDB ID: 4AGC)] also showed strong binding interaction and is found to be stabilized within 18-30ns but slightly deviated during 100ns of MD simulation. In silico ADME-Tox study using SwissADME revealed that the ligands luteolin 7-O-glucoside (IHP15) and chlorogenic acid (IHP12) have passed majority parameters of the common drug discovery rules. The present study has confirmed luteolin 7-O-glucoside (IHP15) and chlorogenic acid (IHP12) as potential tyrosine kinase inhibitors (TKIs) which were found to inhibit RTKs-HER2 and VEGFR2 receptor proteins, and thus paving the way for development of alternative potential TKIs (drug molecules) for treatment of HER2- and VEGFR2-positive breast and stomach cancer.

Pathological Angiogenesis Requires Syndecan-4 for Efficient VEGFA-Induced VE-Cadherin Internalization.

[Figure: see text].

Limonin inhibits angiogenesis and metastasis of human breast cancer cells by suppressing the VEGFR2/IGFR1-mediated STAT3 signaling pathway.

BackgroundLimonin is one of the major active ingredients of citrus. In the present study, the anti-angiogenic and anti-metastatic effects of limonin were investigated.MethodsThe Molecular docking assay was carried out to assess the binding ability of limonin with VEGFR2 receptor. MTS assay was used to detect the effect of limonin on the proliferation of breast cancer cells (MDA-MB-231, MCF-7). The Wound-healing and Transwell chamber invasion assays were used to detect the inhibition effect of limonin on migration and invasion of HUVECs cells or breast cancer cells. The capillary-like tube formation assay and Matrixgel plug experiment were used to further measure the in vivo anti-angiogenic activity of limonin. Western blot, RNA isolation, microarray data analysis and RT-PCR were used to explore the molecular mechanism of limonin in suppressing breast cancer angiogenesis and metastasis. Left ventricular tumor metastasis model and caudal vein tumor metastasis model of breast cancer were both applied to verify in vivo anti-metastatic effects.ResultsLimonin dose-dependently inhibited the vascular endothelial growth factor (VEGF)-mediated tyrosine phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) by blocking VEGF binding to VEGFR2 and suppressing constitutive STAT3 activation in human umbilical vein endothelial cells. Limonin effectively inhibited VEGF-induced endothelial cell proliferation, migration and tubular-structure formation in vitro and markedly reduced VEGF-triggered neovascularization in mouse matrigel plugs in vivo. Moreover, limonin treatment led to a remarkable suppression of tumor metastasis by decreasing the phosphorylation of insulin growth factor receptor 1-mediated STAT3 and the expression levels of its downstream members MMP-9 and VEGF in breast cancer cells. The data further showed that limonin increased the levels of the negative STAT3 regulator SHP-1 in breast cancer cells.ConclusionsLimonin is a promising anti-angiogenic and anti-metastatic candidate compound that can be further optimized as a therapeutic agent for breast cancer.

Strategies targeting angiogenesis in advanced non-small cell lung cancer.

Tumor angiogenesis is a frequent event in the development and progression of non-small cell lung cancer (NSCLC) and has been identified as a promising therapeutic target. The vascular endothelial growth factor (VEGF) family and other angiogenic factors, including fibroblast growth factor and platelet-derived growth factor, promote the growth of newly formed vessels from preexisting vessels and change the tumor microenvironment. To date, two antiangiogenic monoclonal antibodies, bevacizumab and ramucirumab, which target VEGF-A and its receptor VEGF receptor-2, respectively, have been approved for the treatment of locally advanced or metastatic NSCLC when added to first-line standard chemotherapy. Numerous oral multitargeting angiogenic small molecule tyrosine kinase inhibitors (TKIs) have been widely evaluated in advanced NSCLC, but only nintedanib in combination with platinum-based doublet chemotherapy has demonstrated a survival benefit in the second-line setting. Additionally, small-molecule TKIs remain the standard of care for patients with mutated EGFR, ALK or ROS1. Moreover, immune checkpoint inhibitors that target the programmed cell death protein 1 (PD-1) and programmed cell death protein ligand 1 (PD-L1) are changing the current strategy in the treatment of advanced NSCLC without driver gene mutations. The potential synergistic activity of antiangiogenic agents and TKIs or immunotherapy is an interesting topic of research. This review will summarize the novel antiangiogenic agents, antiangiogenic monotherapy, as well as potential combination therapeutic strategies for the clinical management of advanced NSCLC.

Synthesis of a Mini‐Reporter Construct to Test Gene Transfer of RNA Therapeutics.

Glioblastoma multiforme (GBM), a grade IV tumor of the central nervous system, is the most common malignant primary brain tumor in adults, with a median survival of only 14 months. This poor survival rate is due to a lack of efficacy in current therapies, including chemotherapy and radiation, which are limited by the blood‐brain barrier. GBM survival depends on tumor cells to generate new vasculature, which is essential for the exchange of wastes and nutrients. Endothelial cells connect with each other and form the walls of new blood vessels, bridging the gap between the growing tumor mass and the established vasculature of the circulatory system. The membrane receptor that activates this growth is vascular endothelial growth factor receptor 2 (VEGFR2). In our lab, we are developing a novel therapy to alter the VEGFR2 receptor so that it cannot form a bridge with its cognate ligand, vascular endothelial growth factor. Alteration in VEGFR2 so that it cannot form this bridge, blocks its activation and inhibits the development of new blood vessels. We have designed therapies to deliver the genetic sequences of anti‐sense RNA therapy molecules to alter the splicing pattern and expression of the VEGFR2 transcript, creating a soluble VEGFR2 decoy. We have designed and cloned a mini‐reporter‐system that contains the regulatory elements of VEGFR2 splicing. This system measures the efficacy of RNA anti‐sense therapeutics to alter the splicing of the VEGFR2 transcript. The visual marker, eukaryotic green fluorescent protein is used to mimic the natural splicing product, whereas the red fluorescent protein, mCherry detects changes in the the efficacy of our RNA anti‐sense therapy. We use a GBM tissue culture model to measure mini‐reporter and therapy expression. In this manner, the mini‐reporter construct provides a quick and visually measurable test to optimize RNA anti‐sense therapies directed against VEGFR2.Support or Funding InformationBristol‐Myers Squibb

Hypertonic saline alleviates experimentally induced cerebral oedema through suppression of vascular endothelial growth factor and its receptor VEGFR2 expression in astrocytes.

BackgroundCerebral oedema is closely related to the permeability of blood–brain barrier, vascular endothelial growth factor (VEGF) and its receptor vascular endothelial growth factor receptor 2 (VEGFR2) all of which are important blood–brain barrier (BBB) permeability regulatory factors. Zonula occludens 1 (ZO-1) and claudin-5 are also the key components of BBB. Hypertonic saline is widely used to alleviate cerebral oedema. This study aimed to explore the possible mechanisms underlying hypertonic saline that ameliorates cerebral oedema effectively.MethodsMiddle cerebral artery occlusion (MCAO) model in Sprague-Dawley (SD) rats and of oxygen–glucose deprivation model in primary astrocytes were used in this study. The brain water content (BWC) was used to assess the effect of 10 % HS on cerebral oedema. The assessment of Evans blue (EB) extravasation was performed to evaluate the protective effect of 10 % HS on blood–brain barrier. The quantification of VEGF, VEGFR2, ZO-1 and claudin-5 was used to illustrate the mechanism of 10 % HS ameliorating cerebral oedema.ResultsBWC was analysed by wet-to-dry ratios in the ischemic hemisphere of SD rats; it was significantly decreased after 10 % HS treatment (P < 0.05). We also investigated the blood–brain barrier protective effect by 10 % HS which reduced EB extravasation effectively in the peri-ischemic brain tissue. In parallel to the above notably at 24 h following MCAO, mRNA and protein expression of VEGF and VEGFR2 in the peri-ischemic brain tissue was down-regulated after 10 % HS treatment (P < 0.05). Along with this, in vitro studies showed increased VEGF and VEGFR2 mRNA and protein expression in primary astrocytes under hypoxic condition (P < 0.05), but it was suppressed after HS treatment (P < 0.05). In addition, HS inhibited the down-regulation of ZO-1, claudin-5 effectively.ConclusionsThe results suggest that 10 % HS could alleviate cerebral oedema possibly through reducing the ischemia induced BBB permeability as a consequence of inhibiting VEGF–VEGFR2-mediated down-regulation of ZO-1, claudin-5.

Direct binding of hepatocyte growth factor and vascular endothelial growth factor to CD44v6

CD44v6, a member of the CD44 family of transmembrane glycoproteins is a co-receptor for two receptor tyrosine kinases (RTKs), Met and VEGFR-2 (vascular endothelial growth factor receptor 2). CD44v6 is not only required for the activation of these RTKs but also for signalling. In order to understand the role of CD44v6in Met and VEGFR-2 activation and signalling we tested whether CD44v6 binds to their ligands, HGF (hepatocyte growth factor) and VEGF (vascular endothelial growth factor), respectively. FACS analysis and cellular ELISA showed binding of HGF and VEGF only to cells expressing CD44v6. Direct binding of CD44v6 to HGF and VEGF was demonstrated in pull-down assays and the binding affinities were determined using MicroScale Thermophoresis, fluorescence correlation spectroscopy and fluorescence anisotropy. The binding affinity of CD44v6 to HGF is in the micromolar range in contrast with the high-affinity binding measured in the case of VEGF and CD44v6, which is in the nanomolar range. These data reveal a heparan sulfate-independent direct binding of CD44v6 to the ligands of Met and VEGFR-2 and suggest different roles of CD44v6 for these RTKs.

Ephrin B2 and EphB4 selectively mark arterial and venous vessels in cerebral arteriovenous malformation

Ephrin type B receptor 4 (EphB4, Eph receptor) selectively binds ephrin B2 (Eph ligand). EphB4/ephrin B2 is involved in embryonic vessel development, vascular remodelling and pathological vessel formation in adults (including tumour angiogenesis). Binding of vascular endothelial growth factor (VEGF)-A to the endothelial-specific receptor VEGF receptor-2 is the main extracellular signal triggering angiogenic response. Little is known about the role of EphB4/ephrin B2 during angiogenesis and arteriovenous plasticity in cerebral arteriovenous malformation (cAVM). This study investigated EphB4 and ephrin B2 expression in cAVM. Haemorrhagic (H-AVM) and nonhaemorrhagic (NH-AVM) specimens of AVM nidus, obtained after microsurgical cAVM resection, and normal superficial temporal artery (STA) specimens, were analysed retrospectively. VEGF-A, EphB4 and ephrin B2 expression were studied by immunohistochemistry and immunoblotting. In cAVM (10 H-AVM; 10 NH-AVM), VEGF-A was immunocytochemically localized to endothelial cells; strong endothelial cell staining was found for EphB4 in veins and ephrin B2 in arteries. Normal STA (n = 10) did not express EphB4 or ephrin B2. EphB4 and ephrin B2 expression was greater in H-AVM than in NH-AVM. Endothelial cells are more active in H-AVM than NH-AVM. EphB4 and ephrin B2 play important roles in neovascularization and arteriovenous differentiation/plasticity. These data provide new insights into the aetiology of cAVM and lay a foundation for further study. The notch pathway induced by VEGF-A may be a key signalling pathway in this process.

Role of plasma membrane caveolae/lipid rafts in VEGF-induced redox signaling in human leukemia cells.

Caveolae/lipid rafts are membrane-rich cholesterol domains endowed with several functions in signal transduction and caveolin-1 (Cav-1) has been reported to be implicated in regulating multiple cancer-associated processes, ranging from tumor growth to multidrug resistance and angiogenesis. Vascular endothelial growth factor receptor-2 (VEGFR-2) and Cav-1 are frequently colocalized, suggesting an important role played by this interaction on cancer cell survival and proliferation. Thus, our attention was directed to a leukemia cell line (B1647) that constitutively produces VEGF and expresses the tyrosine-kinase receptor VEGFR-2. We investigated the presence of VEGFR-2 in caveolae/lipid rafts, focusing on the correlation between reactive oxygen species (ROS) production and glucose transport modulation induced by VEGF, peculiar features of tumor proliferation. In order to better understand the involvement of VEGF/VEGFR-2 in the redox signal transduction, we evaluated the effect of different compounds able to inhibit VEGF interaction with its receptor by different mechanisms, corroborating the obtained results by immunoprecipitation and fluorescence techniques. Results here reported showed that, in B1647 leukemia cells, VEGFR-2 is present in caveolae through association with Cav-1, demonstrating that caveolae/lipid rafts act as platforms for negative modulation of VEGF redox signal transduction cascades leading to glucose uptake and cell proliferation, suggesting therefore novel potential targets.

Synthesis and Evaluation of Vascular Endothelial Growth Factor Receptor-2 Inhibitory Activity of 6,7-Dimethoxycinnoline Derivatives

A series of 6, 7-Dimethoxycinnoline derivatives were prepared as vascular endothelial growth factor receptor 2 (VEGFR-2) inhibitors and their activity to inhibit VEGFR-2 and epidermal growth factor receptor (EGFR) were evaluated. The structure-activity studies on compounds screening led to the discovery of a novel series of potent and selective VEGFR-2 inhibitors. Compound 6-(6,7-dimethoxycinnolin -4-yloxy)-N-(4-chlorophenyl)naphthalene-1-carboxamide 7a showed potent VEGFR-2 inhibitory activity and good selectivity against EGFR.

Static, but not cyclic tensional forces on the heart increase anti-angiogenic sFlt-1 expression in endothelial cells and inhibit VEGFR-2 activation

Purpose: The left ventricle (LV) is subject to increased mechanical forces in a variety of diseases that cause chronic increased systolic or diastolic pressures. These are often associated with endothelial dysfunction and/or reduced numbers of capillaries. Further mechanical forces are known to modulate endothelial gene expression. Therefore, we hypothesized, that increase in static tensional forces on capillary endothelial cells of the LV result in up-regulation of soluble VEGF receptor 1 (sFlt-1) and thus leading to an imbalance of proand anti-angiogenic stimuli in the heart. Methods: A rabbit Langendorff heart with retrograde constant pressure perfusion was used as model. As perfusate oxygenated Dulbecco’s modified Eagle’s medium was used to keep the heart viable as long as possible without deterioration of its function or sings of ischemia. For the tensional force 5g per g of heart weight was applied to the apex of the beating LV either as static load or every 30 seconds (cyclic). For a set of experiments cardiac contractions were completely arrested using butanedione monoxime (BDM). Quantitative RT-PCR, immunoblots and co-immunoprecipitation was used to quantify mRNA and proteins of sFlt-1, vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR-2). Immunohistochemistry was performed for colocalized of proteins. Results: Increased static tensional force on the LV leads to significant increase in mRNA (3,8 fold, p < 0.05) and protein expression of sFlt-1 (1,4 fold, p < 0.05), which can be detected as early as after 30min and remains increased for the duration of the experiments (up to 6h). Cyclic tensional forces, however, do not affect sFlt-1 mRNA or protein levels. VEGF levels are unaffected by both static and cycle forces on the beating heart. Complete cardiac arrest without affecting the endothelium by BDM, an ATPase inhibitor of skeletal myosin 2, does not affect sFlt-1 or VEGF expression. Increased sFlt-1 due to increased static force on the LV binds more VEGF, shown by co-immunoprecipitation of sFlt-1 and VEGF, and reduced VEGFR-2 phosphorylation. Endothelial cells of the heart were colocalized by immunohistochemistry as source of sFlt-1 release. Conclusions: Static, but not cyclic tensional forces on the LV result in increased release of anti-angiogenic sFlt-1 from capillary endothelial cells. While expression levels of VEGF remain unchanged, sFlt-1 binds VEGF and reduces activation of the signalling Receptor VEGFR-2. Thus, chronic increased forces in the LV contribute to the anti-angiogenic setting and reduced capillary density as seen in many heart diseases.

Expression of VEGF, its receptors, and HIF-1α in Dupuytren’s disease

Background and purpose — Dupuytren’s disease (DD) is a benign fibroproliferative process that affects the palmar fascia. The pathology of DD shows similarities with wound healing and tumor growth; hypoxia and angiogenesis play important roles in both. We investigated the role of angiogenic proteins in DD.Patients and methods — The expression of vascular endothelial growth factor (VEGF), its receptors vascular endothelial growth factor receptor 1 (VEGFR1) and vascular endothelial growth factor receptor 2 (VEGFR2), hypoxia-inducible factor alfa (HIF-1α), and alfa-smooth muscle actin (α-SMA) were analyzed immunohistochemically in fragments of excised Dupuytren’s tissue from 32 patients. We compared these values to values for expression in a control group.Results — 15 of 32 samples could be attributed to the involutional phase (α-SMA positive), whereas 17 samples were considered to be cords at the residual phase (α-SMA negative). In the involutional phase, the HIF-1α and VEGFR2 expression was statistically significantly higher than in the residual phase and in the controls.Interpretation — Both the VEGFR2 receptor and HIF-1α were expressed in α-SMA positive myofibroblast-rich nodules with characteristics of DD in the active involutional phase. Thus, hypoxia and (subsequently) angiogenesis may have a role in the pathophysiology of DD.

The enzymatic activity of the VEGFR2 receptor for the biosynthesis of dinucleoside polyphosphates

The group of dinucleoside polyphosphates encompasses a large number of molecules consisting of two nucleosides which are connected by a phosphate chain of variable length. While the receptors activated by dinucleoside polyphosphates as well as their degradation have been studied in detail, its biosynthesis has not been elucidated so far. Since endothelial cells released the dinucleoside polyphosphate uridine adenosine tetraphosphate (Up4A), we tested cytosolic proteins of human endothelial cells obtained from dermal vessels elicited for enzymatic activity. When incubated with ADP and UDP, these cells showed increasing concentrations of Up4A. The underlying enzyme was isolated by chromatography and the mass spectrometric analysis revealed that the enzymatic activity was caused by the vascular endothelial growth factor receptor 2 (VEGFR2). Since VEGFR2 but neither VEGFR1 nor VEGFR3 were capable to synthesise dinucleoside polyphosphates, Tyr-1175 of VEGFR2 is most likely essential for the enzymatic activity of interest. Further, VEGFR2-containing cells like HepG2, THP-1 and RAW264.7 were capable of synthesising dinucleoside polyphosphates. VEGFR2-transfected HEK 293T/17 but not native HEK 293T/17 cells synthesised dinucleoside polyphosphates in vivo too. The simultaneous biosynthesis of dinucleoside polyphosphates could amplify the response to VEGF, since dinucleoside polyphosphates induce cellular growth via P2Y purinergic receptors. Thus the biosynthesis of dinucleoside polyphosphates by VEGFR2 may enhance the proliferative response to VEGF. Given that VEGFR2 is primarily expressed in endothelial cells, the biosynthesis of dinucleoside polyphosphates is mainly located in the vascular system. Since the vasculature is also the main site of action of dinucleoside polyphosphates, activating vascular purinoceptors, blood vessels appear as an autocrine system with respect to dinucleoside polyphosphates. We conclude that VEGFR2 receptor is capable of synthesising dinucleoside polyphosphates. These mediators may modulate the effects of VEGFR2 due to their proliferative effects.