Dopamine regulates phosphorylation of VEGF receptor 2 by engaging Src-homology-2-domain-containing protein tyrosine phosphatase 2

Dopamine-Functionalized, Red Carbon Quantum Dots for In Vivo Bioimaging, Cancer Therapeutics, and Neuronal Differentiation

One of the crucial requirements of quantum dots for biological applications is their surface modification for very specific and enhanced biological recognition and uptake. Toward this end, we present the green synthesis of bright, red-emitting carbon quantum dots derived from mango leaf extract (mQDs). These mQDs are conjugated electrostatically with dopamine to form mQDs-dopamine (mQDs:DOPA) bioconjugates. Bright-red fluorescence of mQDs was used for bioimaging and uptake in cancerous and noncancerous cell lines, tissues, and in vivo models like zebrafish. mQDs exhibited the highest uptake in brain tissue compared to the heart, kidney, and liver. mQD:DOPA conjugates killed breast cancer cells and increased uptake in epithelial RPE-1 cells and zebrafish. Additionally, mQDs:DOPA promoted neuronal differentiation of SH-SY5Y cells to differentiated neurons. Both mQDs and mQDs:DOPA exhibited the potential for higher collective cell migrations, implicating their future potential as next-generation tools for advanced biological and biomedical applications.

Preparation and characterization of vaginal suppository of semisynthetic derivatives of ergot alkaloids cabergoline

Background

There is evidence that vaginal cabergoline can help to prevent ovarian hyperstimulation syndrome. Therefore, the vaginal suppository may be a good choice because it can be administered directly into the vagina and has no adverse effects on the stomach. In this regard we developed a cabergoline suppository as an alternative to cabergoline tablets. Design-Expert was used to determine the most suitable concentrations of PEG 6000/400, and Tween 80 to obtain a stable suppository. Specific ratios of PEG6000/400 and Tween 80 were entered as factors, and release, melting time, and hardness were evaluated as responses. In addition, the final formulation was evaluated for weight changes, pH, drug content, degradation time, deformation time, in vitro drug release, DSC analysis, infrared spectroscopy, and stability properties.

Results

The suppositories were all smooth and white. They all had a weight that averaged less than 5 %. The formulations showed a pH between 6 and 6.5. The active ingredient content ranged between 79.666 ± 8.54 % and 99.67 ± 6.55 %. Suppository stiffness was between 2.74 ± 0.04 and 4.20 ± 0.03. The decomposition time of the suppositories varied between 11.25 ± 0.15 to 20.19 ± 0.08 min. The deformation time was between 26.11 ± 0.06 to 38.59 ± 0.47 min. Cabergoline content was released over 45 min from formulations of F10 (∼46 %), F2 (∼64 %), F6 (∼69 %), F4 (∼79 %), F1 (∼88 %), and F7 (∼93 %). However, other formulations released more than 95 % within 45 min.

Conclusions

All variables except melting time significantly affected our responses. In vitro studies have indicated that the optimized cabergoline formula could be an excellent alternative to cabergoline oral formulations.

Molecular mechanisms of Thrombospondin-2 modulates tumor vasculogenic mimicry by PI3K/AKT/mTOR signaling pathway

Vasculogenic mimicry (VM) differs from the classical tumor angiogenesis model. VM does not depend on endothelial cells; instead, highly aggressive tumor cells mimic endothelial cells to form a vascular-like channel structure. VM mediated by tumor cells is significantly and positively associated with a poor prognosis and low survival rates in patients with highly aggressive cancer. In the treatment of highly aggressive malignancies, the presence of VM is considered an important reason for the unsatisfactory clinical efficacy of anti-tumor-angiogenesis therapy (e.g., therapy targeting vascular endothelial growth factor A). Many targeted therapeutic drugs based on traditional tumor blood vessels have been used clinically. Although some progress has been made in certain tumors, problems such as drug resistance have restricted the expected therapeutic effects. Thrombospondin 2 (THBS2) is one of the most important genes associated with angiogenesis, and this gene exerts angiogenesis-related functions through the PI3K/AKT signaling pathway. Although the PI3K/AKT/mTOR signaling pathway is closely related to the progression of VM, the mechanism by which the promising biomarker THBS2 participates in and regulates tumor VM by activating the PI3K/AKT/mTOR signaling pathway is unclear. In this review, we analyze the monomer structure and biological activity of THBS2, the structure and potential synthesis mechanisms of VM, and the complex mechanisms between THBS2, the PI3K/AKT/mTOR signaling pathway, and VM.

Dopamine signaling from ganglion cells directs layer-specific angiogenesis in the retina

During central nervous system (CNS) development, a precisely patterned vasculature emerges to support CNS function. How neurons control angiogenesis is not well understood. Here, we show that the neuromodulator dopamine restricts vascular development in the retina via temporally limited production by an unexpected neuron subset. Our genetic and pharmacological experiments demonstrate that elevating dopamine levels inhibits tip-cell sprouting and vessel growth, whereas reducing dopamine production by all retina neurons increases growth. Dopamine production by canonical dopaminergic amacrine interneurons is dispensable for these events. Instead, we found that temporally restricted dopamine production by retinal ganglion cells (RGCs) modulates vascular development. RGCs produce dopamine precisely during angiogenic periods. Genetically limiting dopamine production by ganglion cells, but not amacrines, decreases angiogenesis. Conversely, elevating ganglion-cell-derived dopamine production inhibits early vessel growth. These vasculature outcomes occur downstream of vascular endothelial growth factor receptor (VEGFR) activation and Notch-Jagged1 signaling. Jagged1 is increased and subsequently inhibits Notch signaling when ganglion cell dopamine production is reduced. Our findings demonstrate that dopaminergic neural activity from a small neuron subset functions upstream of VEGFR to serve as developmental timing cue that regulates vessel growth.

Antiangiogenic Effect of Dopamine and Dopaminergic Agonists as an Adjuvant Therapeutic Option in the Treatment of Cancer, Endometriosis, and Osteoarthritis

Dopamine (DA) and dopamine agonists (DA-Ag) have shown antiangiogenic potential through the vascular endothelial growth factor (VEGF) pathway. They inhibit VEGF and VEGF receptor 2 (VEGFR 2) functions through the dopamine receptor D2 (D2R), preventing important angiogenesis-related processes such as proliferation, migration, and vascular permeability. However, few studies have demonstrated the antiangiogenic mechanism and efficacy of DA and DA-Ag in diseases such as cancer, endometriosis, and osteoarthritis (OA). Therefore, the objective of this review was to describe the mechanisms of the antiangiogenic action of the DA-D2R/VEGF-VEGFR 2 system and to compile related findings from experimental studies and clinical trials on cancer, endometriosis, and OA. Advanced searches were performed in PubMed, Web of Science, SciFinder, ProQuest, EBSCO, Scopus, Science Direct, Google Scholar, PubChem, NCBI Bookshelf, DrugBank, livertox, and Clinical Trials. Articles explaining the antiangiogenic effect of DA and DA-Ag in research articles, meta-analyses, books, reviews, databases, and clinical trials were considered. DA and DA-Ag have an antiangiogenic effect that could reinforce the treatment of diseases that do not yet have a fully curative treatment, such as cancer, endometriosis, and OA. In addition, DA and DA-Ag could present advantages over other angiogenic inhibitors, such as monoclonal antibodies.

Diabetic rats with high levels of endogenous dopamine do not show retinal vascular pathology

Purpose

Limited research exists on the time course of long-term retinal and cerebral deficits in diabetic rodents. Previously, we examined short term (4-8 weeks) deficits in the Goto-Kakizaki (GK) rat model of Type II diabetes. Here, we investigated the long-term (1-8 months) temporal appearance of functional deficits (retinal, cognitive, and motor), retinal vascular pathology, and retinal dopamine levels in the GK rat.

Methods

In GK rats and Wistar controls, retinal neuronal function (electroretinogram), cognitive function (Y-maze), and motor function (rotarod) were measured at 1, 2, 4, 6, and 8 months of age. In addition, we evaluated retinal vascular function (functional hyperemia) and glucose and insulin tolerance. Retinas from rats euthanized at ≥8 months were assessed for vascular pathology. Dopamine and DOPAC levels were measured via HPLC in retinas from rats euthanized at 1, 2, 8, and 12 months.

Results

Goto-Kakizaki rats exhibited significant glucose intolerance beginning at 4 weeks and worsening over time (p < 0.001). GK rats also showed significant delays in flicker and oscillatory potential implicit times (p < 0.05 to p < 0.001) beginning at 1 month. Cognitive deficits were observed beginning at 6 months (p < 0.05), but no motor deficits. GK rats showed no deficits in functional hyperemia and no increase in acellular retinal capillaries. Dopamine levels were twice as high in GK vs. Wistar retinas at 1, 2, 8, and 12 months (p < 0.001).

Conclusion

As shown previously, retinal deficits were detectable prior to cognitive deficits in GK rats. While retinal neuronal function was compromised, retinal vascular pathology was not observed, even at 12+ months. High endogenous levels of dopamine in the GK rat may be acting as an anti-angiogenic and providing protection against vascular pathology.

KIF13B mediates VEGFR2 recycling to modulate vascular permeability

Excessive vascular endothelial growth factor-A (VEGF-A) signaling induces vascular leakage and angiogenesis in diseases. VEGFR2 trafficking to the cell surface, mediated by kinesin-3 family protein KIF13B, is essential to respond to VEGF-A when inducing angiogenesis. However, the precise mechanism of how KIF13B regulates VEGF-induced signaling and its effects on endothelial permeability is largely unknown. Here we show that KIF13B-mediated recycling of internalized VEGFR2 through Rab11-positive recycling vesicle regulates endothelial permeability. Phosphorylated VEGFR2 at the cell-cell junction was internalized and associated with KIF13B in Rab5-positive early endosomes. KIF13B mediated VEGFR2 recycling through Rab11-positive recycling vesicle. Inhibition of the function of KIF13B attenuated phosphorylation of VEGFR2 at Y951, SRC at Y416, and VE-cadherin at Y685, which are necessary for endothelial permeability. Failure of VEGFR2 trafficking to the cell surface induced accumulation and degradation of VEGFR2 in lysosomes. Furthermore, in the animal model of the blinding eye disease wet age-related macular degeneration (AMD), inhibition of KIF13B-mediated VEGFR2 trafficking also mitigated vascular leakage. Thus, the present results identify the fundamental role of VEGFR2 recycling to the cell surface in mediating vascular permeability, which suggests a promising strategy for mitigating vascular leakage associated with inflammatory diseases.

Dopamine ameliorates hyperglycemic memory-induced microvascular dysfunction in diabetic retinopathy

Dopamine is a neurotransmitter that mediates visual function in the retina and diabetic retinopathy (DR) is the most common microvascular complication of diabetes and the leading cause of blindness; however, the role of dopamine in retinal vascular dysfunction in DR remains unclear. Here, we report a mechanism of hyperglycemic memory (HGM)-induced retinal microvascular dysfunction and the protective effect of dopamine against the HGM-induced retinal microvascular leakage and abnormalities. We found that HGM induced persistent oxidative stress, mitochondrial membrane potential collapse and fission, and adherens junction disassembly and subsequent vascular leakage after blood glucose normalization in the mouse retinas. These persistent hyperglycemic stresses were inhibited by dopamine treatment in human retinal endothelial cells and by intravitreal injection of levodopa in the retinas of HGM mice. Moreover, levodopa supplementation ameliorated HGM-induced pericyte degeneration, acellular capillary and pericyte ghost generation, and endothelial apoptosis in the mouse retinas. Our findings suggest that dopamine alleviates HGM-induced retinal microvascular leakage and abnormalities by inhibiting persistent oxidative stress and mitochondrial dysfunction.

The Inhibitory Effect of Selected D2 Dopaminergic Receptor Agonists on VEGF-Dependent Neovascularization in Zebrafish Larvae: Potential New Therapy in Ophthalmic Diseases

Pathological angiogenesis is correlated with many ophthalmic diseases. The most common are exudative age-related macular degeneration and proliferative diabetic retinopathy. The current treatment for these diseases is based on regularly administered anti-VEGF antibodies injections. In the study, we investigated selected D₂ dopaminergic receptor agonists, namely bromocriptine, cabergoline and pergolide, on hypoxia-induced neovascularization. We used the zebrafish laboratory model, specifically three-day post fertilization (dpf) Tg(fli-1: EGFP) zebrafish larvae. To induce abnormal angiogenesis of hyaloid-retinal vessels (HRVs) and intersegmental vessels (ISVs), the larvae were treated with cobalt chloride (II) (CoCl₂) (a hypoxia-inducing agent) from 24 h post fertilization. The inhibitory role of D₂ dopaminergic receptor agonists was investigated using confocal microscopy and qPCR. Additionally, the results were compared to those obtained in the group treated with CoCl₂ followed by bevacizumab, the well-known antiangiogenic agent. Confocal microscopy analyses revealed severe deformation of vessels in the CoCl₂ treated group, while co-incubation with bromocriptine, cabergoline, pergolide and bevacizumab, respectively, significantly inhibited abnormalities of angiogenesis. The qPCR analyses supported the protective role of the chosen dopaminergic agonists by demonstrating their influence on CoCl₂-derived upregulation of vegfaa expression. The present results suggest that the D₂ receptor agonists can be considered as a new direction in research for antiangiogenic therapy.

Quinagolide Treatment Reduces Invasive and Angiogenic Properties of Endometrial Mesenchymal Stromal Cells

Endometrial mesenchymal stromal cells (E-MSCs) extensively contribute to the establishment and progression of endometrial ectopic lesions through formation of the stromal vascular tissue, and support to its growth and vascularization. As E-MSCs lack oestrogen receptors, endometriosis eradication cannot be achieved by hormone-based pharmacological approaches. Quinagolide is a non-ergot-derived dopamine receptor 2 agonist reported to display therapeutic effects in in vivo models of endometriosis. In the present study, we isolated E-MSCs from eutopic endometrial tissue and from ovarian and peritoneal endometriotic lesions, and we tested the effect of quinagolide on their proliferation and matrix invasion ability. Moreover, the effect of quinagolide on E-MSC endothelial differentiation was assessed in an endothelial co-culture model of angiogenesis. E-MSC lines expressed dopamine receptor 2, with higher expression in ectopic than eutopic ones. Quinagolide inhibited the invasive properties of E-MSCs, but not their proliferation, and limited their endothelial differentiation. The abrogation of the observed effects by spiperone, a dopamine receptor antagonist, confirmed specific dopamine receptor activation. At variance, no involvement of VEGFR2 inhibition was observed. Moreover, dopamine receptor 2 activation led to downregulation of AKT and its phosphorylation. Of interest, several effects were more prominent on ectopic E-MSCs with respect to eutopic lines. Together with the reported effects on endometrial and endothelial cells, the observed inhibition of E-MSCs may increase the rationale for quinagolide in endometriosis treatment.

Spiperone Stimulates Regeneration in Pulmonary Endothelium Damaged by Cigarette Smoke and Lipopolysaccharide

Background

Endothelial dysfunction and destruction of the pulmonary microcirculation are important pathogenic factors in chronic obstructive pulmonary disease (COPD). In COPD, bronchial obstruction is associated with endothelial dysfunction. Thus, new pharmacological treatment options aimed at restoring the pulmonary endothelium represent a clinical need in COPD therapy. Notch1 has been shown to protect cells against apoptosis, inflammation, and oxidative stress caused by cigarette smoke extract (CSE). Therefore, drug which effect on Notch1 may be a potential therapeutic target for COPD in the future.

Methods

In this study, we assessed the potential of spiperone to mediate regeneration of pulmonary endothelium in model of pulmonary emphysema induced by a CSE and lipopolysaccharide (LPS) in female C57BL/6 mice.

Results

Spiperone increased the number of capillaries as well as the expression of the CD31 in the alveolar tissue compared to the controls. Moreover, application of spiperone prevented alveolar wall destruction (DI), and reduced the area of emphysema. Lastly, we demonstrated that spiperone positively influenced mobilization and migration of endothelial progenitor cells (EPC, CD45⁻CD34⁺CD31⁺), CD309⁺-endothelial cells, and angiogenesis precursors (CD45⁻CD117⁺CD309⁺) into the lung. Spiperone administration significantly reduced the number Notch1 positive CD309⁺-endothelial cells and Notch1+ EPCs.

Conclusion

Overall, our results suggest that spiperone mediates endothelial regeneration in an animal model of COPD. Thus, it could represent a novel therapeutic approach for treatment of emphysema associated with COPD.

Endothelial deletion of SHP2 suppresses tumor angiogenesis and promotes vascular normalization

SHP2 mediates the activities of multiple receptor tyrosine kinase signaling and its function in endothelial processes has been explored extensively. However, genetic studies on the role of SHP2 in tumor angiogenesis have not been conducted. Here, we show that SHP2 is activated in tumor endothelia. Shp2 deletion and pharmacological inhibition reduce tumor growth and microvascular density in multiple mouse tumor models. Shp2 deletion also leads to tumor vascular normalization, indicated by increased pericyte coverage and vessel perfusion. SHP2 inefficiency impairs endothelial cell proliferation, migration, and tubulogenesis through downregulating the expression of proangiogenic SRY-Box transcription factor 7 (SOX7), whose re-expression restores endothelial function in SHP2-knockdown cells and tumor growth, angiogenesis, and vascular abnormalization in Shp2-deleted mice. SHP2 stabilizes apoptosis signal-regulating kinase 1 (ASK1), which regulates SOX7 expression mediated by c-Jun. Our studies suggest SHP2 in tumor associated endothelial cells is a promising anti-angiogenic target for cancer therapy.

Growth Factor Deregulation and Emerging Role of Phosphatases in Diabetic Peripheral Artery Disease

Peripheral artery disease is caused by atherosclerosis of lower extremity arteries leading to the loss of blood perfusion and subsequent critical ischemia. The presence of diabetes mellitus is an important risk factor that greatly increases the incidence, the progression and the severity of the disease. In addition to accelerated disease progression, diabetic patients are also more susceptible to develop serious impairment of their walking abilities through an increased risk of lower limb amputation. Hyperglycemia is known to alter the physiological development of collateral arteries in response to ischemia. Deregulation in the production of several critical pro-angiogenic factors has been reported in diabetes along with vascular cell unresponsiveness in initiating angiogenic processes. Among the multiple molecular mechanisms involved in the angiogenic response, protein tyrosine phosphatases are potent regulators by dephosphorylating pro-angiogenic tyrosine kinase receptors. However, evidence has indicated that diabetes-induced deregulation of phosphatases contributes to the progression of several micro and macrovascular complications. This review provides an overview of growth factor alterations in the context of diabetes and peripheral artery disease, as well as a description of the role of phosphatases in the regulation of angiogenic pathways followed by an analysis of the effects of hyperglycemia on the modulation of protein tyrosine phosphatase expression and activity. Knowledge of the role of phosphatases in diabetic peripheral artery disease will help the development of future therapeutics to locally regulate phosphatases and improve angiogenesis.

Inside-outside Ag nanoparticles-loaded polylactic acid electrospun fiber for long-term antibacterial and bone regeneration

Bone infections caused by bacteria during bone graft implantations can impair the ability of bone tissue repair, which is currently a clinical problem. In this study, the electrospinning technique was used to prepare a polylactic acid (PLLA)/silver (Ag) composite fiber, in which the silver nanoparticles (Ag-NPs) were uniformly distributed on the inner surface of PLLA fibers; dopamine (DA) was self-polymerized on the composite fiber surface to construct the adhesive polydopamine (PDA) film and chitosan (CS) was used to regulate Ag⁺ in situ through pulse electrochemical deposition for the construction of a stable Ag-NPs coating (CS/Ag), achieving the steady and slow release of Ag-NPs, therefore accomplishing the construction of a "inside-outside" Ag-NPs-loaded PLLA/Ag@PDA@CS/Ag composite fiber with dual functions of long-lasting antibacterial effect as well as bone regeneration promotion ability. The study results showed that the composite fiber has an excellent antibacterial effect against E. coli and S. aureus, and good osteoinductive and angiogenic properties. In summary, under the dual regulations of the strong adhesion of PDA and CS chelation, the "inside-outside" Ag-NPs-loaded composite fiber was endowed with good physiological stability, long-term antibacterial effect and bone infection inhibition ability, making it a promising bone implant material.

Blockade of Dopamine D2 Receptors as a Novel Approach to Stimulation of Notch1+ Endothelial Progenitor Cells and Angiogenesis in C57BL/6 Mice with Pulmonary Emphysema Induced by Proteases and Deficiency of α1-Antitrypsin

We studied the effects of spiperone, a selective blocker of dopamine D2 receptors, on the model of pulmonary emphysema provoked by administration of elastase and D-galactosamine hydrochloride to female C57BL/6 mice and characterized by activation of proteases in the lungs and systemic deficiency of its inhibitor α1-antitrypsin. In this model, spiperone prevented the development of inflammatory reaction and reduced the area of emphysematous expanded alveolar tissue. The expression of angiogenic marker CD31 in the lungs increased under these conditions. Regeneration of the damaged microvascular bed under the action of spiperone resulted from recruiting of Notch1⁺ endothelial progenitor cells (CD45^-CD31⁺CD34⁺) into the lungs and blockade of the inhibitory effect of dopamine on phosphorylation of VEGF-2 receptors in endothelial cells of different maturity. In addition, spiperone produced a protective effect on hepatocytes and restored the production and secretion of α1-antitrypsin by these cells.

Bioactive polymeric scaffolds for osteogenic repair and bone regenerative medicine

The loss of bone tissue is a striking challenge in orthopedic surgery. Tissue engineering using various advanced biofunctional materials is considered a promising approach for the regeneration and substitution of impaired bone tissues. Recently, polymeric supportive scaffolds and biomaterials have been used to rationally promote the generation of new bone tissues. To restore the bone tissue in this context, biofunctional polymeric materials with significant mechanical robustness together with embedded materials can act as a supportive matrix for cellular proliferation, adhesion, and osteogenic differentiation. The osteogenic regeneration to replace defective tissues demands greater calcium deposits, high alkaline phosphatase activity, and profound upregulation of osteocalcin as a late osteogenic marker. Ideally, the bioactive polymeric scaffolds (BPSs) utilized for bone tissue engineering should impose no detrimental impacts and function as a carrier for the controlled delivery and release of the loaded molecules necessary for the bone tissue regeneration. In this review, we provide comprehensive insights into different synthetic and natural polymers used for the regeneration of bone tissue and discuss various technologies applied for the engineering of BPSs and their physicomechanical properties and biological effects.

An opsin 5-dopamine pathway mediates light-dependent vascular development in the eye

During mouse postnatal eye development, the embryonic hyaloid vascular network regresses from the vitreous as an adaption for high-acuity vision. This process occurs with precisely controlled timing. Here, we show that opsin 5 (OPN5; also known as neuropsin)-dependent retinal light responses regulate vascular development in the postnatal eye. In Opn5-null mice, hyaloid vessels regress precociously. We demonstrate that 380-nm light stimulation via OPN5 and VGAT (the vesicular GABA/glycine transporter) in retinal ganglion cells enhances the activity of inner retinal DAT (also known as SLC6A3; a dopamine reuptake transporter) and thus suppresses vitreal dopamine. In turn, dopamine acts directly on hyaloid vascular endothelial cells to suppress the activity of vascular endothelial growth factor receptor 2 (VEGFR2) and promote hyaloid vessel regression. With OPN5 loss of function, the vitreous dopamine level is elevated and results in premature hyaloid regression. These investigations identify violet light as a developmental timing cue that, via an OPN5-dopamine pathway, regulates optic axis clearance in preparation for visual function.

Surface Modification of Calcium Silicate via Mussel-Inspired Polydopamine and Effective Adsorption of Extracellular Matrix to Promote Osteogenesis Differentiation for Bone Tissue Engineering

Calcium silicate-based cement has garnered huge interest in recent years, due to its versatility and potential in mass fabrication of a variety of bioceramics. For this study, the main objective was to fabricate functionalized calcium silicate (CS) powder integrated with a simple bio-inspired surface modification using polydopamine (PDA), to regulate cellular behaviors such as cellular adhesion, and subsequently cell differentiation and proliferation. For this study, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques were used to analyze the chemical compositions and observe the surface characteristics of our PDA coated CS cements. Such modifications were found to enhance Wharton Jelly's mesenchymal stem cells (WJMSC) in various ways. Firstly, PDA-coated CS cements were found to significantly enhance cell adhesion with higher expressions of cell adhesion markers, such as focal adhesion kinase and integrins. This was further supported by morphology analysis of the cells. This enhanced cell adhesion, in turn, led to significantly higher secretion of extracellular matrix (ECM) proteins, such as collagen I and fibronectin, which directly promoted cell attachments and proliferation. In our osteogenesis assays, it was found that secretion and expression of osteogenesis related genes and proteins were significantly higher and were dependent on the PDA content. Therefore, these results demonstrated that such simple bio-inspired modification techniques of synthetic degradable CS cements can be applied as a future modification, to modify and convert inert surfaces of synthetic bone grafts to enhance and modulate the cell behaviors of WJMSCs. This in turn can be used as a potential alternative for further bioengineering research.

Counterbalance: modulation of VEGF/VEGFR activities by TNFSF15

Vascular hyperpermeability occurs in angiogenesis and several pathobiological conditions, producing elevated interstitial fluid pressure and lymphangiogenesis. How these closely related events are modulated is a fundamentally important question regarding the maintenance of vascular homeostasis and treatment of disease conditions such as cancer, stroke, and myocardial infarction. Signals mediated by vascular endothelial growth factor receptors, noticeably VEGFR-1, −2, and −3, are centrally involved in the promotion of both blood vessel and lymphatic vessel growth. These signaling pathways are counterbalanced or, in the case of VEGFR3, augmented by signals induced by tumor necrosis factor superfamily-15 (TNFSF15). TNFSF15 can simultaneously downregulate membrane-bound VEGFR1 and upregulate soluble VEGFR1, thus changing VEGF/VEGFR1 signals from pro-angiogenic to anti-angiogenic. In addition, TNFSF15 inhibits VEGF-induced VEGFR2 phosphorylation, thereby curbing VEGFR2-mediated enhancement of vascular permeability. Third, and perhaps more interestingly, TNFSF15 is capable of stimulating VEGFR3 gene expression in lymphatic endothelial cells, thus augmenting VEGF-C/D-VEGFR3-facilitated lymphangiogenesis. We discuss the intertwining relationship between the actions of TNFSF15 and VEGF in this review.

The ability of tumor necrosis factor superfamily-15 (TNFSF15) protein to balance the actions of vascular endothelial growth factors (VEGFs) highlights new therapeutic strategies for the treatment of diseases that disrupt the circulatory system. Gui-Li Yang at the Tianjin Neurological Institute and Lu-Yuan Li at Nankai University describe the mechanisms through which TNFSF15 inhibits blood vessel growth mediated by VEGF receptor-1 (VEGFR1) and counterbalances the increase in vascular permeability mediated by VEGFR2. Interestingly, TNFSF15 enhances the effects of VEGFR3 on the formation of lymphatic vessels by promoting VEGFR3 gene expression in lymphatic endothelial cells. Further research will determine whether TNFSF15′s unique capacity to regulate the properties of both blood and lymph vessels can be harnessed to improve the treatment of conditions such as cancer, stroke, myocardial infarction and lymphoedema.

TNFSF15 inhibits VEGF-stimulated vascular hyperpermeability by inducing VEGFR2 dephosphorylation

Vascular hyperpermeability is critical in ischemic diseases, including stroke and myocardial infarction, as well as in inflammation and cancer. It is well known that the VEGF-VEGFR2 signaling pathways are pivotal in promoting vascular permeability; however, counterbalancing mechanisms that restrict vascular permeability to maintain the integrity of blood vessels are not yet fully understood. We report that TNF superfamily member 15 (TNFSF15), a cytokine largely produced by vascular endothelial cells and a specific inhibitor of the proliferation of these same cells, can inhibit VEGF-induced vascular permeability in vitro and in vivo, and that death receptor 3 (DR3), a cell surface receptor of TNFSF15, mediates TNFSF15-induced dephosphorylation of VEGFR2. Src homology region 2 domain-containing phosphatase-1 (SHP-1) becomes associated with DR3 upon TNFSF15 interaction with the latter. In addition, a protein complex consisting of VEGFR2, DR3, and SHP-1 is formed in response to the effects of TNFSF15 and VEGF on endothelial cells. It is plausible that this protein complex provides a structural basis for the molecular mechanism in which TNFSF15 induces the inhibition of VEGF-stimulated vascular hyperpermeability.-Yang, G.-L., Zhao, Z., Qin, T.-T., Wang, D., Chen, L., Xiang, R., Xi, Z., Jiang, R., Zhang, Z.-S., Zhang, J., Li. L.-Y. TNFSF15 inhibits VEGF-stimulated vascular hyperpermeability by inducing VEGFR2 dephosphorylation.

Modulation of VEGF receptor 2 signaling by protein phosphatases

Phosphorylation of serines, threonines, and tyrosines is a central event in signal transduction cascades in eukaryotic cells. The phosphorylation state of any particular protein reflects a balance of activity between kinases and phosphatases. Kinase biology has been exhaustively studied and is reasonably well understood, however, much less is known about phosphatases. A large body of evidence now shows that protein phosphatases do not behave as indiscriminate signal terminators, but can function both as negative or positive regulators of specific signaling pathways. Genetic models have also shown that different protein phosphatases play precise biological roles in health and disease. Finally, genome sequencing has unveiled the existence of many protein phosphatases and associated regulatory subunits comparable in number to kinases. A wide variety of roles for protein phosphatase roles have been recently described in the context of cancer, diabetes, hereditary disorders and other diseases. In particular, there have been several recent advances in our understanding of phosphatases involved in regulation of vascular endothelial growth factor receptor 2 (VEGFR2) signaling. The receptor is the principal signaling molecule mediating a wide spectrum of VEGF signal and, thus, is of paramount significance in a wide variety of diseases ranging from cancer to cardiovascular to ophthalmic. This review focuses on the current knowledge about protein phosphatases' regulation of VEGFR2 signaling and how these enzymes can modulate its biological effects.

Relationship between Oxidative Stress, Circadian Rhythms, and AMD

This work reviews concepts regarding oxidative stress and the mechanisms by which endogenous and exogenous factors produce reactive oxygen species (ROS). It also surveys the relationships between oxidative stress, circadian rhythms, and retinal damage in humans, particularly those related to light and photodamage. In the first section, the production of ROS by different cell organelles and biomolecules and the antioxidant mechanisms that antagonize this damage are reviewed. The second section includes a brief review of circadian clocks and their relationship with the cellular redox state. In the third part of this work, the relationship between retinal damage and ROS is described. The last part of this work focuses on retinal degenerative pathology, age-related macular degeneration, and the relationships between this pathology, ROS, and light. Finally, the possible interactions between the retinal pigment epithelium (RPE), circadian rhythms, and this pathology are discussed.

Role of Dopamine and D2 Dopamine Receptor in the Pathogenesis of Inflammatory Bowel Disease

BACKGROUND

VEGF-induced vascular permeability and blood vessels remodeling are key features of inflammatory bowel disease (IBD) pathogenesis. Dopamine through D2 receptor (D2R) inhibits VEGF/VPF-mediated vascular permeability and angiogenesis in tumor models. In this study, we tested the hypothesis that pathogenesis of IBD is characterized by the disturbance of dopaminergic system and D2R activity.

METHODS

IL-10 knockout (KO) mice and rats with iodoacetamide-induced ulcerative colitis (UC) were treated intragastrically with D2R agonists quinpirole (1 mg/100 g) or cabergoline (1 or 5 µg/100 g). Macroscopic, histologic, and clinical features of IBD, colonic vascular permeability, and angiogenesis were examined.

RESULTS

Although colonic D2R protein increased, levels of tyrosine hydroxylase and dopamine transporter DAT decreased in both models of IBD. Treatment with quinpirole decreased the size of colonic lesions in rats with iodoacetamide-induced UC (p < 0.01) and reduced colon wet weight in IL-10 KO mice (p < 0.05). Quinpirole decreased colonic vascular permeability (p < 0.001) via downregulation of c-Src and Akt phosphorylation. Cabergoline (5 µg/100 g) reduced vascular permeability but did not affect angiogenesis and improved signs of iodoacetamide-induced UC in rats (p < 0.05).

CONCLUSIONS

Treatment with D2R agonists decreased the severity of UC in two animal models, in part, by attenuation of enhanced vascular permeability and prevention of excessive vascular leakage. Hence, the impairment dopaminergic system seems to be a feature of IBD pathogenesis.

Dopamine agonist inhibits vascular endothelial growth factor protein production and secretion in granulosa cells

BACKGROUND

Dopamine receptor 2 agonists (D2-ags) inhibit vascular endothelial growth factor (VEGF) secretion in luteinized granulosa cells (LGCs) both in vitro and in vivo. However, the mechanism of D2 regulation of the VEGF/VEGF Receptor 2 (VEGFR-2) pathway remains to be elucidated. We sought to determine the effects of D2 signaling on VEGF transcription and translation in LGCs, with the expectation of identifying potential D2-ag-based therapies for ovarian hyperstimulation syndrome (OHSS).

FINDINGS

LGCs from egg donors were cultured with chorionic gonadotropin (hCG) in the presence of Actinomycin-D (ActD) or Brefeldin-A (BFA) to evaluate the effects of a D2-ag, cabergoline (Cb2), on VEGF secretion. The contribution of the conventional Gi/Go, Gz and AKT/β-Arrestin pathways in the VEGF regulation was assessed by adding pertussis toxin (PTX), phorbol 12-myristate 13-acetate (PMA), or wortmannin (WT). While Cb2 inhibited VEGF secretion by interfering with VEGF peptide translation and secretion, inhibition of conventional D2 transduction pathways did not reverse Cb2-mediated inhibition of VEGF secretion.

CONCLUSIONS

The effects of D2-ag on VEGF translation and secretion are mediated by D2 signaling pathways that have yet to be described. We found that D2-ag inhibits VEGF secretion at the post-transcriptional level, suggesting that D2-ag treatment should be combined with therapies that inhibit VEGF transcription, such as the employment of LH or GnRH for triggering ovulation, to improve the efficacy of OHSS prevention.

Osteogenesis of human adipose-derived stem cells on poly(dopamine)-coated electrospun poly(lactic acid) fiber mats

Electrospinning is a versatile technique to generate large quantities of micro- or nano-fibers from a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized electrospun nano-fibers and use a mussel-inspired surface coating to regulate adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared poly(lactic acid) (PLA) fibers coated with polydopamine (PDA). The morphology, chemical composition, and surface properties of PDA/PLA were characterized by SEM and XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. Increased focal adhesion kinase (FAK) and collagen I levels and enhanced cell attachment and cell cycle progression were observed upon an increase in PDA content. In addition, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on a pure PLA mat. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenesis differentiation. Our results demonstrate that the bio-inspired coating synthetic degradable PLA polymer can be used as a simple technique to render the surfaces of synthetic biodegradable fibers, thus enabling them to direct the specific responses of hADSCs.

Poly(Dopamine)-Assisted Immobilization of Xu Duan on 3D Printed Poly(Lactic Acid) Scaffolds to Up-Regulate Osteogenic and Angiogenic Markers of Bone Marrow Stem Cells

Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu Duan (XD) immobilization to regulate cell adhesion, proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBMSCs). We prepared PLA scaffolds and coated with polydopamine (PDA). The chemical composition and surface properties of PLA/PDA/XD were characterized by XPS. PLA/PDA/XD controlled hBMSCs' responses in several ways. Firstly, adhesion and proliferation of hBMSCs cultured on PLA/PDA/XD were significantly enhanced relative to those on PLA. In addition, the focal adhesion kinase (FAK) expression of cells was increased and promoted cell attachment depended on the XD content. In osteogenesis assay, the osteogenesis markers of hBMSCs cultured on PLA/PDA/XD were significantly higher than seen in those cultured on a pure PLA/PDA scaffolds. Moreover, hBMSCs cultured on PLA/PDA/XD showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hBMSCs.

Poly(dopamine) coating of 3D printed poly(lactic acid) scaffolds for bone tissue engineering

3D printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating to regulate cell adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared PLA 3D scaffolds coated with polydopamine (PDA). The chemical composition and surface properties of PDA/PLA were characterized by XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation, and cell cycle of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. In addition, the collagen I secreted from cells was increased and promoted cell attachment and cell cycle progression were depended on the PDA content. In osteogenesis assay, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on pure PLA scaffolds. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hADSCs.

Identification of novel vascular projections with cellular trafficking abilities on the microvasculature of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a nearly lethal neoplasm. It is a remarkably stroma-rich, vascular-poor and hypo-perfused tumour, which prevents efficient drug delivery. Paradoxically, the neoplastic cells have robust glucose uptake, suggesting that the microvasculature has adopted an alternative method for nutrient uptake and cellular trafficking. Using adapted thick tumour section immunostaining and three-dimensional (3D) construction imaging in human tissue samples, we identified an undiscovered feature of the mature microvasculature in advanced PDAC tumours; long, hair-like projections on the basal surface of microvessels that we refer to as 'basal microvilli'. Functionally, these basal microvilli have an actin-rich cytoskeleton and endocytic and exocytic properties, and contain glucose transporter-1 (GLUT-1)-positive vesicles. Clinically, as demonstrated by PET-CT, the tumour microvasculature with the longest and most abundant basal microvilli correlated with high glucose uptake of the PDAC tumour itself. In addition, these basal microvilli were found in regions of the tumour with low GLUT-1 expression, suggesting that their presence could be dependent upon the glucose concentration in the tumour milieu. Similar microvasculature features were also observed in a K-Ras-driven model of murine PDAC. Altogether, these basal microvilli mark a novel pathological feature of PDAC microvasculature. Because basal microvilli are pathological features with endo- and exocytic properties, they may provide a non-conventional method for cellular trafficking in PDAC tumours.

Dopamine receptor 2 activation inhibits ovarian vascular endothelial growth factor secretion in an ovarian hyperstimulation syndrome (OHSS) animal model: implications for treatment of OHSS with dopamine receptor 2 agonists

OBJECTIVE

To explore whether a dopamine receptor 2 agonist (D2-ag) can prevent ovarian hyperstimulation syndrome (OHSS) in a rat model by decreasing ovarian vascular endothelial growth factor (VEGF) production.

DESIGN

Experimental study in an OHSS animal model.

SETTING

University-affiliated infertility center.

PATIENT(S)

Immature Wistar rats.

INTERVENTION(S)

Immature rats were stimulated with gonadotropins to mimic OHSS and treated with a D2-ag and/or D2-antagonists (D2-ant). Vascular permeability (VP) was measured at the endpoint, and ovaries were collected to assess the effects of these drugs on VEGF production.

MAIN OUTCOME MEASURE(S)

VP was estimated by measuring the peritoneal extravasation of a previously injected dye. Ovarian VEGF mRNA expression and VEGF protein levels were assessed by quantitative real-time PCR and Western blots, respectively.

RESULT(S)

The D2-ag exerted a reduction in VP that was associated with a drastic decrease in VEGF protein production in OHSS rat ovaries. The effects of this D2-ag on VP and VEGF protein levels were partially reversed by concomitant administration of a D2-ant. Ovarian VEGF mRNA expression levels were unaffected by these drugs in OHSS rats.

CONCLUSION(S)

D2-ags prevent increased VP in OHSS rats by decreasing ovarian VEGF production, very likely through a D2-mediated post-transcriptional mechanism. Given the dose-dependent inhibitory effect of D2-ags on ovarian VEGF production reported herein, we infer that current OHSS therapies used in humans may be improved by increasing the intraovarian concentration of D2-ags in these patients.

Dopamine D2 receptor agonists inhibit lung cancer progression by reducing angiogenesis and tumor infiltrating myeloid derived suppressor cells

We sought to determine whether Dopamine D2 Receptor (D2R) agonists inhibit lung tumor progression and identify subpopulations of lung cancer patients that benefit most from D2R agonist therapy. We demonstrate D2R agonists abrogate lung tumor progression in syngeneic (LLC1) and human xenograft (A549) orthotopic murine models through inhibition of tumor angiogenesis and reduction of tumor infiltrating myeloid derived suppressor cells. Pathological examination of human lung cancer tissue revealed a positive correlation between endothelial D2R expression and tumor stage. Lung cancer patients with a smoking history exhibited greater levels of D2R in lung endothelium. Our results suggest D2R agonists may represent a promising individualized therapy for lung cancer patients with high levels of endothelial D2R expression and a smoking history.

Dopamine receptor 2 activation inhibits ovarian vascular endothelial growth factor secretion in vitro: implications for treatment of ovarian hyperstimulation syndrome with dopamine receptor 2 agonists

OBJECTIVE

To ascertain whether vascular endothelial growth factor (VEGF) secretion by luteinized granulosa cells (GCs) is modulated by the dopaminergic system in a dose-dependent fashion and how this is related to the differential efficacy of dopamine receptor 2 (D2)-agonists (D2-ag) in preventing ovarian hyperstimulation syndrome (OHSS).

DESIGN

The relationship between the dopaminergic system and VEGF secretion in luteinized GCs was evaluated. Archived human ovaries were immunostained to characterize D2 expression.

SETTING

University affiliated infertility center.

PATIENT(S)

Premenopausal women and egg donors.

INTERVENTION(S)

Luteinized GCs were cultured with the D2-ag cabergoline. Human ovarian sections were immunostained for D2.

MAIN OUTCOME MEASURE(S)

The VEGF was measured by ELISA and D2 expression was evaluated by In-Cell ELISA. The D2 expression throughout the luteal phase was characterized by immunohistochemistry.

RESULT(S)

The VEGF secretion was decreased by the D2-ag in a dose-dependent fashion. The efficiency of this process was correlated with the amount of D2 expressed by luteinized GCs. A decrease in D2 expression in ovarian sections was observed during the late luteal phase.

CONCLUSION(S)

The efficacy of D2-ags in preventing OHSS might rely on their capacity to inhibit VEGF secretion by luteinized GCs. Because this capacity is dose-dependent, increasing the intraovarian concentration of D2-ags should be explored as a means of increasing the efficacy of these drugs in preventing OHSS.

Thrombospondin-1 modulates VEGF signaling via CD36 by recruiting SHP-1 to VEGFR2 complex in microvascular endothelial cells

Thrombospondin-1 (TSP-1) inhibits growth factor signaling at the receptor level in microvascular endothelial cells (MVEC), and CD36 has been suggested to be involved in this inhibition, but the mechanisms are not known. We hypothesized that CD36-TSP-1 interaction recruits Src homology 2 domain-containing protein tyrosine phosphatase (SHP)-1 to the vascular endothelial growth factor receptor 2 (VEGFR2) signaling complex and attenuates vascular endothelial growth factor (VEGF) signaling. Western blots of anti-CD36 and anti-VEGFR2 immunoprecipitates from VEGF-treated MVEC showed that exposure of the cells to a recombinant protein containing the CD36 binding domain of thrombospondin-1 (known as the TSR domain) induced association of SHP-1 with the VEGFR2/CD36 signaling complex and thereby suppressed VEGFR2 phosphorylation. SHP-1 phosphatase activity was increased in immunoprecipitated VEGFR2 complexes from TSR-treated cells. Silencing CD36 expression in MVEC by small interfering RNA (siRNA) or genetic deletion of cd36 in mice showed that TSR-induced SHP-1/VEGFR2 complex formation required CD36 in vitro and in vivo. Silencing SHP-1 expression in MVEC by siRNA abrogated TSR-mediated inhibition of VEGFR2 phosphorylation as well as TSR-mediated inhibition of VEGF-induced endothelial cell migration and tube formation. These studies reveal a SHP-1-mediated antiangiogenic pathway induced by CD36-TSP-1 interaction that inhibits VEGFR2 signaling and they provide a novel target to modulate angiogenesis therapeutically.

Endothelial cell-specific chemotaxis receptor (ECSCR) enhances vascular endothelial growth factor (VEGF) receptor-2/kinase insert domain receptor (KDR) activation and promotes proteolysis of internalized KDR

The endothelial cell-specific chemotaxis receptor (ECSCR) is a cell-surface protein selectively expressed by endothelial cells (ECs), with roles in EC migration, apoptosis and proliferation. Our previous study (Verma, A., Bhattacharya, R., Remadevi, I., Li, K., Pramanik, K., Samant, G. V., Horswill, M., Chun, C. Z., Zhao, B., Wang, E., Miao, R. Q., Mukhopadhyay, D., Ramchandran, R., and Wilkinson, G. A. (2010) Blood 115, 4614-4622) showed that loss of ECSCR in primary ECs reduced tyrosine phosphorylation of vascular endothelial growth factor (VEGF) receptor 2/kinase insert domain receptor (KDR) but not VEGF receptor 1/FLT1. Here, we show that ECSCR biochemically associates with KDR but not FLT1 and that the predicted ECSCR cytoplasmic and transmembrane regions can each confer association with KDR. Stimulation with VEGF165 rapidly and transiently increases ECSCR-KDR complex formation, a process blocked by the KDR tyrosine kinase inhibitor compound SU5416 or inhibitors of endosomal acidification. Triple labeling experiments show VEGF-stimulated KDR(+)/ECSCR(+) intracellular co-localization. Silencing of ECSCR disrupts VEGF-induced KDR activation and AKT and ERK phosphorylation and impairs VEGF-stimulated KDR degradation. In zebrafish, ecscr interacts with kdrl during intersomitic vessel sprouting. Human placenta and infantile hemangioma samples highly express ECSCR protein, suggesting a role for ECSCR-KDR interaction in these tissues.

KIDs rule: regulatory phosphorylation of RTKs

Receptor tyrosine kinases (RTKs) are mediators of multiple cell signaling networks linked to cell growth and differentiation. In general, they exhibit similar overall structure with a ligand-binding extracellular domain and a conserved intracellular tyrosine kinase domain. In many RTKs, the kinase domain is interrupted by a sequence known as the kinase insert domain (KID). In addition to phosphorylation sites within the kinase domain, regulatory phosphorylation also occurs within the KID of several RTKs important in human health and disease. Phosphorylation of specific Tyr or Ser residues within the KID of some RTKs triggers distinct cellular signaling outcomes. Here, we review the functionality of KIDs throughout all RTK families, and provide justification for further study of this often-overlooked domain.

The vitamin K-dependent anticoagulant factor, protein S, inhibits multiple VEGF-A-induced angiogenesis events in a Mer- and SHP2-dependent manner

Protein S is a vitamin K-dependent glycoprotein, which, besides its anticoagulant function, acts as an agonist for the tyrosine kinase receptors Tyro3, Axl, and Mer. The endothelium expresses Tyro3, Axl, and Mer and produces protein S. The interaction of protein S with endothelial cells and particularly its effects on angiogenesis have not yet been analyzed. Here we show that human protein S, at circulating concentrations, inhibited vascular endothelial growth factor (VEGF) receptor 2-dependent vascularization of Matrigel plugs in vivo and the capacity of endothelial cells to form capillary-like networks in vitro as well as VEGF-A-induced endothelial migration and proliferation. Furthermore, protein S inhibited VEGF-A-induced endothelial VEGFR2 phosphorylation and activation of mitogen-activated kinase-Erk1/2 and Akt. Protein S activated the tyrosine phosphatase SHP2, and the SHP2 inhibitor NSC 87877 reversed the observed inhibition of VEGF-A-induced endothelial proliferation. Using siRNA directed against Tyro3, Axl, and Mer, we demonstrate that protein S-mediated SHP2 activation and inhibition of VEGF-A-stimulated proliferation were mediated by Mer. Our report provides the first evidence for the existence of a protein S/Mer/SHP2 axis, which inhibits VEGFR2 signaling, regulates endothelial function, and points to a role for protein S as an endogenous angiogenesis inhibitor.

β₂-glycoprotein I inhibits VEGF-induced endothelial cell growth and migration via suppressing phosphorylation of VEGFR2, ERK1/2, and Akt

β(2)-glycoprotein I (β(2)-GPI) is a plasma glycoprotein with diverse functions, but the impact and molecular effects of β(2)-GPI on vascular biology are as yet unclear. Based on the limited information available on the contribution of β(2)-GPI to endothelial cells, we investigated the effect of β(2)-GPI on cell growth and migration in human aortic endothelial cells (HAECs). The regulation of β(2)-GPI as part of intracellular signaling in HAECs was also examined. Vascular endothelial growth factor (VEGF) is a pro-angiogenic factor that may regulate endothelial functions. We found that β(2)-GPI dose-dependently inhibited VEGF-induced endothelial cell growth using the 3-(4,5-dimethylthiazol-2-yl)-2,5-dipenyl tetrazolium bromide assay and cell counts. Using wound healing and Boyden chamber assays, β(2)-GPI remarkably reduced VEGF-increased cell migration at the physiological concentration. Furthermore, β(2)-GPI suppressed VEGF-induced phosphorylation of VEGF receptor 2 (VEGFR2), extracellular signal-regulated kinase 1/2 (ERK1/2), and Akt. These results suggest that β(2)-GPI plays an essential role in the down-regulation of VEGF-induced endothelial responses and may be a useful component for anti-angiogenic therapy.

Dopamine inhibits pulmonary edema through the VEGF-VEGFR2 axis in a murine model of acute lung injury

The neurotransmitter dopamine and its dopamine receptor D2 (D2DR) agonists are known to inhibit vascular permeability factor/vascular endothelial growth factor (VEGF)-mediated angiogenesis and vascular permeability. Lung injury is a clinical syndrome associated with increased microvascular permeability. However, the effects of dopamine on pulmonary edema, a phenomenon critical to the pathophysiology of both acute and chronic lung injuries, have yet to be established. Therefore, we sought to determine the potential therapeutic effects of dopamine in a murine model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Compared with sham-treated controls, pretreatment with dopamine (50 mg/kg body wt) ameliorated LPS-mediated edema formation and lowered myeloperoxidase activity, a measure of neutrophil infiltration. Moreover, dopamine significantly increased survival rates of LPS-treated mice, from 0-75%. Mechanistically, we found that dopamine acts through the VEGF-VEGFR2 axis to reduce pulmonary edema, as dopamine pretreatment in LPS-treated mice resulted in decreased serum VEGF, VEGFR2 phosphorylation, and endothelial nitric oxide synthase phosphorylation. We used D2DR knockout mice to confirm that dopamine acts through D2DR to block vascular permeability in our lung injury model. As expected, a D2DR agonist failed to reduce pulmonary edema in D2DR(-/-) mice. Taken together, our results suggest that dopamine acts through D2DR to inhibit pulmonary edema-associated vascular permeability, which is mediated through VEGF-VEGFR2 signaling and conveys protective effects in an ALI model.

Von Hippel-Lindau gene product directs cytokinesis: a new tumor suppressor function

One of the mechanisms of tumorigenesis is that the failure of cell division results in genetically unstable, multinucleated cells. Here we show that pVHL, a tumor suppressor protein that has been implicated in the pathogenesis of renal cell carcinoma (RCC), plays an important role in regulation of cytokinesis. We found that pVHL-deficient RCC 786-O cells were multinucleated and polyploid. Reintroduction of wild-type pVHL into these cells rescued the diploid cell population, whereas the mutant pVHL-K171G failed to do so. We demonstrate that lysine 171 of pVHL is important for the final step of cytokinesis: the midbody abscission. The pVHL-K171G caused failure to localize the ESCRT-1 interacting protein Alix and the v-SNARE complex component Endobrevin to the midbody in 786-O cells, leading to defective cytokinesis. Moreover, SUMOylation of pVHL at lysine 171 might modulate its function as a cytokinesis regulator. pVHL tumor suppressor function was also disrupted by the K171G mutation, as evidenced by the xenograft tumor formation when 786-O clones expressing pVHL-K171G were injected into mice. Most RCC cell lines show a polyploid chromosome complement and consistent heterogeneity in chromosome number. Thus, this study offers a way to explain the chromosome instability in RCC and reveals a new direction for the tumor suppressor function of pVHL, which is independent of its E3 ubiquitin ligase activity.

Vascular permeability to plasma, plasma proteins, and cells: an update

PURPOSE OF REVIEW

The blood vasculature supplies tissues with nutrients, clears waste products, and carries and directs leukocytes to inflammatory sites. To accomplish these functions, microvessels regulate the extravasation of small molecules, plasma proteins and inflammatory cells. The mechanisms responsible for these events have been the subject of intense investigation and, often, dispute.

RECENT FINDINGS

Recent progress has contributed to a better understanding of the mechanisms by which microvessels of different types and in different vascular beds regulate the passage of small and large molecules and cells. Roles are shown for the glycocalyx, caveolae, perictyes, sphingosine-1-phosphate, and newly discovered signaling pathways.

SUMMARY

Vascular permeability is important for maintaining homeostasis and is greatly increased in acute and chronic inflammation, wound healing, and growing tumors. New work has contributed importantly to the mechanisms responsible for regulating permeability.