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The purpose of this study was to investigate the effect of gold nanoparticles on the signaling cascade related to angiogenesis and vascular permeability induced by Vascular Endothelial Growth Factor (VEGF) in Bovine retinal endothelial cells (BRECs). The effect of VEGF and gold nanoparticles on cell viability, migration and tubule formation was assessed. PP2 (Src Tyrosine Kinase inhibitor) was used as the positive control and the inhibitor assay was performed to compare the effect of AuNPs on VEGF induced angiogenesis. The transient transfection assay was performed to study the VEGFR2/Src activity during experimental conditions and was confirmed using western blot analysis. Treatment of BRECs with VEGF significantly increased the cell proliferation, migration and tube formation. Furthermore, gold nanoparticles (500 nM) significantly inhibited the proliferation, migration and tube formation, in the presence of VEGF in BRECs. The gold nanoparticles also inhibited VEGF induced Src phosphorylation through which their mode of action in inhibiting angiogenic pathways is revealed. The fate of the gold nanoparticles within the cells is being analyzed using the TEM images obtained. The potential of AuNPs to inhibit the VEGF165-induced VEGFR-2 phosphorylation is also being confirmed through the receptor assay which elucidates one of the possible mechanism by which AuNPs inhibit VEGF induced angiogenesis. These results indicate that gold nanoparticles can block VEGF activation of important signaling pathways, specifically Src in BRECs and hence modulation of these pathways may contribute to gold nanoparticles ability to block VEGF-induced retinal neovascularization.

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Proliferative vitreo retinopathy (PVR) is one of the ocular complications, marked by the enhanced proliferation of various cells including retinal pigment epithelial cells (RPE). The aim of the present study is to analyze the effect of gold nanoparticles (Au-NP) on vascular endothelial growth factor (VEGF) and interleukin-1 beta (IL-1ß)-induced cell spreading, migration and proliferation in RPE cells. Au-NP (300 nM) significantly blocked the VEGF-and IL-1ß-induced cell spreading, migration and proliferation in bovine RPE cells (BRPEs). To elucidate the signaling mechanism of VEGF- and IL-1ß-induced cell proliferation, BRPEs were treated with PP2, a Src inhibitor. Further, to clarify the possible involvement of the Src pathway on the inhibitory effect of Au-NPs, transient transfection assay was performed using dominant negative (DN) and constitutively active (CA) mutant plasmid of Src kinase. The results showed that VEGF and IL-1ß exert their proliferative effects through the activation of Src kinase whereas CA Src rescued the inhibitory effect of Au-NP in presence or absence of VEGF and IL-1ß in BRPEs. Further, an in vitro kinase assay was performed to identify the status of Src phosphorylation at Y419. We found that VEGF and IL-1ß increased Src phosphorylation in BRPEs and Au-NP blocked the VEGF- and IL-1ß-induced Src phosphorylation at Y419. Taken together, our result suggests that Au-NP could effectively inhibit the VEGF- and IL-1ß-induced proliferation and migration by suppressing the Src kinase pathway in BRPEs and Au-NP might act as an effective therapeutic agent for the treatment of ocular diseases such as proliferative vitreo retinopathy.

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Vascular hyperpermeability associated with retinal vascular leakage is known to occur in patients with diabetes, and contributes to endothelial barrier dysfunction. This study aimed to examine the effect of pigment epithelium-derived factor (PEDF) on advanced glycation end products (AGEs)-induced endothelial cell permeability. Cultured porcine retinal endothelial cell (PREC) was exposed to AGE-modified bovine serum albumin (AGE-BSA) and the endothelial cell permeability was detected by measuring the flux of rhodamine B isothiocyanate (RITC)-dextran across the PREC monolayers. We found that AGE-BSA increased the RITC-dextran flux across a PREC monolayer and PEDF blocked the solute flux induced by AGE-BSA. In order to explore the underlying signaling mechanism of PEDF on the inhibitory effect of AGE-BSA-induced permeability, we demonstrate that PEDF could inhibit the AGE-BSA-induced permeability via phosphatidylinositol 3-kinase (PI3K)/Akt pathway. AGE-BSA also increased the endothelial cell permeability by stimulating the reactive oxygen species (ROS) generation via NADPH oxidase activity and Akt phosphorylation at Ser473. PEDF decreased ROS generation in AGE-BSA-exposed endothelial cells by suppressing the NADPH oxidase activity via down regulating the phosphorylation of p22(PHOx) at Thr147. This led to blockade of AGE-induction of PI3K/Akt activation in permeability. Furthermore, PEDF inhibited the AGE-BSA-induced permeability by increased expression of tight junction protein zona occludens-1(ZO-1), co-incident with an increase in barrier properties of endothelial monolayer. Together, our results indicate that PEDF could possibly act as potent anti-permeability molecule by targeting the PI3K/Akt signaling pathway by suppressing if NADPH oxidase mediated ROS generation and ZO-1 tight junction protein and it offers potential targets to inhibit the ocular related diseases such as diabetic retinopathy.

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Erythropoietin (EPO) plays a critical role in the vascular system and exhibits angiogenic activity in endothelial cells (ECs) such as stimulation of cell proliferation, migration and tube formation in vitro. EPO is the major regulator of cell proliferation and differentiation of erythroid precursors and there by preventing the apoptosis. Pigment epithelial derived factor (PEDF) is a potent anti-angiogenic factor whose effects are partially mediated through the induction of EC apoptosis. The mechanism of EPO and PEDF in retinal neovascularization has not been well documented yet. The effect of EPO and PEDF on cell proliferation was determined by MTT assay. In vitro wound-scratch assay was performed to study the migration of ECs and in vitro tube formation was assessed by the on-gel assay system using gelatin. Inhibitor assay was carried out using LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor. Further, PI3K/Akt activity was assessed by transient transfection assay using constitutively active (CA) and dominant negative (DN) Akt mutants. Dextran permeability assay was performed to determine the vascular permeability. We report that EPO stimulates EC proliferation, migration, tube formation and permeability whereas PEDF inhibits the EPO-induced ECs proliferation and permeability. Over expression of DN Akt blocked EPO stimulation of proliferation and permeability, while over expression of CA Akt rescues the inhibitory effect of PEDF on proliferation and permeability. These results demonstrate that PEDF may inhibit the EPO-induced proliferation and permeability via PI3K/Akt-dependent pathway.

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In this report, we demonstrate a method for the isolation of pure homogeneous endothelial cell population from goat's eye without using multi-step procedure and sophisticated instrument facilities. Microvascular endothelial cell from goat's retina were isolated using enzymatic method and cultured in Iscove's Modified Dulbecco's Medium supplemented with 10% fetal bovine serum. Five to 7 d after plating, a monolayer of endothelial cells was formed. These cells were identified as endothelial cells by morphology and confirmed by positive immunocytochemistry for vWF, CD31, VE-cadherin, CD146, VCAM-1, and ICAM-1, a specific marker for endothelial cells. We have compared both the mechanical and non-mechanical enzymatic methods in isolating pure endothelial cells. Cells plated on 4% gelatin-coated dishes resulted in tubular morphology, a characteristic of endothelial cells. This method is simpler and cost-effective when compared with other previously reported methods. These endothelial cells will be more helpful to identify the role of various factors in angiogenic-related disease such as diabetic retinopathy.

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The increased permeability of the blood-retinal barrier is known to occur in patients with diabetes, and this defect contributes to retinal edema. This study aimed to determine the effects of silver nanoparticles (Ag-NPs) on advanced glycation end-products (AGEs)-induced endothelial cell permeability. Cultured porcine retinal endothelial cells (PRECs) were exposed to AGE-modified bovine serum albumin (AGE-BSA) and the endothelial cell permeability was detected by measuring the flux of RITC-dextran across the PREC monolayers. We found that AGE-BSA increased the dextran flux across a PREC monolayer and Ag-NPs blocked the solute flux induced by AGE-BSA. In order to understand the underlying signaling mechanism of Ag-NPs on the inhibitory effect of AGE-BSA-induced permeability, we demonstrated that Ag-NPs could inhibit the AGE-BSA-induced permeability via Src kinase pathway. AGE-BSA also increased the PREC permeability by stimulating the expression of intracellular adhesion molecule-1 (ICAM-1) and decreased the expression of occludin and ZO-1. Further, Ag-NPs inhibited the AGE-BSA-induced permeability by increased expression of tight junction proteins occludin and ZO-1, co-incident with an increase in barrier properties of endothelial monolayer. Together, our results indicate that Ag-NPs could possibly act as potent anti-permeability molecule by targeting the Src signaling pathway and tight junction proteins and it offers potential targets to inhibit the ocular related diseases.

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Increased vascular permeability associated with retinal vascular leakage is known to occur in patients with diabetes, and contributes to endothelial barrier dysfunction. The purpose of this study was to examine the effect of pigment epithelium-derived factor (PEDF) on signaling cascade in porcine retinal endothelial cells (PREC) related to permeability and angiogenesis induced by vascular endothelial growth factor (VEGF)-and interleukin-1beta (IL-1beta). PREC were exposed to VEGF, IL-1beta and PEDF at different concentrations, and in vitro permeability was assessed by solute flux assay using 70-kDa RITC-dextran. Angiogenic assays such as proliferation, migration and tube formation were determined by MTT, wound-scratch method and on-gel assay system respectively. To explore the signaling pathways behind VEGF-and IL-1beta-induced PREC permeability, an inhibitor assay was carried out using PP2, a Src kinase inhibitor. Further, Src activity was assessed by transient transfection assay using constitutively active (CA) and dominant negative (DN) Src mutants. We report that VEGF-and IL-1beta-stimulates permeability, in a dose and time-dependent manner and PEDF inhibits the VEGF-and IL-1beta-induced PREC permeability. In addition, PEDF inhibits the VEGF-and IL-1beta-induced endothelial cell proliferation, migration and tube formation. In addition, overexpression of DN Src blocked both VEGF-and IL-1beta-stimulation of permeability, proliferation and migration, while overexpression of CA Src overpowers the inhibitory action of PEDF on permeability, proliferation and migration. These results demonstrate that PEDF may inhibit the VEGF-and IL-1beta-induced permeability and angiogenesis via Src-dependent pathway.

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Oxidative stress is associated with the development of retinopathy in diabetes; dietary supplementations of multi-antioxidants have no beneficial effects clinically. An antioxidant which could specifically target pathogenesis of diabetic retinopathy is the need of the hour. Pigment epithelium-derived factor is a potent, endogenously produced, multifunctional factor (neurotrophic, anti-angiogenic, anti-inflammatory etc.,) in the eye which recently was also shown to possess anti-oxidative action. However, its anti-oxidative effect against high glucose-induced oxidative stress in retinal endothelial cells has not been investigated. Here, we examined its anti-oxidative effect on cell morphology, survival, reactive oxygen species generation, lipid peroxidation, antioxidant status and caspase-3 activation under high glucose conditions in bovine retinal endothelial cells (BRECs). Cells grown at 33 mM glucose in the presence of PEDF at concentrations 10-50 nM did not exhibit shrinkage. Pigment epithelium-derived factor inhibited the high glucose-induced rise in reactive oxygen species generation and lipid peroxidation. In these cells, reduced glutathione levels and mitochondrial and superoxide dismutase activities increased markedly while reactive oxygen species generation decreased significantly in presence of PEDF as compared with cells grown in the absence of PEDF under high glucose conditions (10-20 nM, *p < 0.01&**p < 0.001; 30-50 nM, ***p < 0.0001). Our results suggest that pigment epithelium-derived factor has an anti-oxidant effect in bovine retinal endothelial cells at a high glucose level. The action of pigment epithelium-derived factor not only varies with the cell type but also depends on its concentration and environmental conditions. Therefore, further studies are required to determine if pigment epithelium-derived factor might constitute a preventive and/or a curative treatment for retinal neovascularization.

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The aim of this study is to determine the effects of silver nanoparticles (Ag-NP) on vascular endothelial growth factor (VEGF)-and interleukin-1 beta (IL-1beta)-induced vascular permeability, and to detect the underlying signaling mechanisms involved in endothelial cells. Porcine retinal endothelial cells (PRECs) were exposed to VEGF, IL-1beta and Ag-NP at different combinations and endothelial cell permeability was analyzed by measuring the flux of RITC-dextran across the PRECs monolayer. We found that VEGF and IL-1beta increase flux of dextran across a PRECs monolayer, and Ag-NP block solute flux induced by both VEGF and IL-1beta. To explore the signalling pathway involved VEGF- and IL-1beta-induced endothelial alteration, PRECs were treated with Src inhibitor PP2 prior to VEGF and IL-1beta treatment, and the effects were recorded. Further, to clarify the possible involvement of the Src pathways in endothelial cell permeability, plasmid encoding dominant negative(DN) and constitutively active(CA) form of Src kinases were transfected into PRECs, 24 h prior to VEGF and IL-1beta exposure and the effects were recorded. Overexpression of DN Src blocked both VEGF-and IL-1beta-induced permeability, while overexpression of CA Src rescues the inhibitory action of Ag-NP in the presence or absence of VEGF and IL-1beta. Further, an in vitro kinase assay was performed to identify the presence of the Src phosphorylation at Y419. We report that VEGF and IL-1beta-stimulate endothelial permeability via Src dependent pathway by increasing the Src phosphorylation and Ag-NP block the VEGF-and IL-1beta-induced Src phosphorylation at Y419. These results demonstrate that Ag-NP may inhibit the VEGF-and IL-1beta-induced permeability through inactivation of Src kinase pathway and this pathway may represent a potential therapeutic target to inhibit the ocular diseases such as diabetic retinopathy.

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Pigment epithelium-derived factor (PEDF) is a well-known protease inhibitor for angiogenesis in the eye, suggesting that loss of PEDF in eye is implicated in the pathogenesis of proliferative diabetic retinopathy. Since the role of PEDF in diabetic retinopathy is unclear, the effect of PEDF on different types of cells constituting the blood vessel has to be checked. Here, we have investigated the effects of PEDF under hyperglycemic conditions in retinal pericytes, isolated from goat's eye and used to analyze the signaling pathway involved. High glucose increased the apoptotic cell death and intracellular reactive oxygen species generation, which was blocked on the addition of PEDF. PEDF was found to inhibit the apoptotic cell death and protect the cells via activating the PI3K/Akt pathway, which was analyzed with dominant negative Akt and constitutively active Akt-transfected cells. These results demonstrate that PEDF protects pericytes against the high glucose-induced apoptosis and dysfunction.

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AIMS: The purpose of this study was to investigate the effect of pigment epithelium-derived factor (PEDF) on the signaling cascade in porcine retinal endothelial cells (PRECs) related to angiogenesis induced by advanced glycation end-products (AGEs). MAIN METHODS: Endothelial cells were isolated from porcine retina by the enzymatic method. Immunocytochemistry was performed to confirm the identity of PRECs. The effect of AGEs and PEDF on cell viability was determined by the MTT assay. An in vitro wound-scratch assay was performed to study the migration of ECs, and in vitro tube formation was assessed by the on-gel assay system using an extracellular matrix. Inhibitor assays were carried out using LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, and Akt inhibitor VIII. PI3K/Akt activity was assessed by transient transfection and western blot analysis. Induction of apoptosis by PEDF was determined by caspase-3 colorimetric assay and DNA fragmentation analysis. KEY FINDINGS: Treatment of PRECs with AGE-bovine serum albumin (AGE-BSA) significantly increased the cell proliferation, migration and tube formation compared to non-glycated BSA. AGE-BSA mediates cell survival via the PI3K/Akt/FKHR-dependent pathway as evidenced by transient transfection and western blot analyses. Furthermore, PEDF significantly inhibited the proliferation, migration and tube formation, both in the presence and absence of AGE-BSA in PRECs. PEDF inactivated the AGE-BSA-induced PI3K/Akt/FKHR activity and induced apoptosis via caspase-3. SIGNIFICANCE: The results reveal that PEDF inhibits AGE-BSA-induced PI3K/Akt/FKHR signaling in PRECs. Thus, PEDF has potent anti-angiogenic effects against AGE-induced angiogenesis and is suggested to be a promising molecule for the treatment of diabetic retinopathy.

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Angiogenesis is an important phenomenon involved in normal growth and wound healing processes. An imbalance of the growth factors involved in this process, however, causes the acceleration of several diseases including malignant, ocular, and inflammatory diseases. Inhibiting angiogenesis through interfering in its pathway is a promising methodology to hinder the progression of these diseases. The function and mechanism of silver nanoparticles (Ag-NPs) in angiogenesis have not been elucidated to date. PEDF is suggested to be a potent anti-angiogenic agent. In this study, we postulated that Ag-NPs might have the ability to inhibit angiogenesis, the pivotal step in tumor growth, invasiveness, and metastasis. We have demonstrated that Ag-NPs could also inhibit vascular endothelial growth factor (VEGF) induced cell proliferation, migration, and capillary-like tube formation of bovine retinal endothelial cells like PEDF. In addition, Ag-NPs effectively inhibited the formation of new blood microvessels induced by VEGF in the mouse Matrigel plug assay. To understand the underlying mechanism of Ag-NPs on the inhibitory effect of angiogenesis, we showed that Ag-NPs could inhibit the activation of PI3K/Akt. Together, our results indicate that Ag-NPs can act as an anti-angiogenic molecule by targeting the activation of PI3K/Akt signaling pathways.

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