Bovine Retinal Capillary Endothelial Cells Research Articles

Resveratrol Prevents ROS-Induced Apoptosis in High Glucose-Treated Retinal Capillary Endothelial Cells via the Activation of AMPK/Sirt1/PGC-1α Pathway.

Resveratrol (RSV) is used as a protective therapy against diabetic retinopathy. However, the mechanism(s) underlying this protective effect has not been fully elucidated. Bovine retinal capillary endothelial cells (BRECs), an in vitro model, were used to investigate the mechanism of RSV. Our results showed that high glucose induced significant cellular apoptosis in BRECs, which was accompanied by increased intracellular levels of reactive oxygen species (ROS) and cleaved caspase-3. The glucose-induced apoptosis and ROS elevation were both inhibited by RSV. High glucose was found to decrease the levels of phosphorylated AMP-activated protein kinase (p-AMPK), which was accompanied by increased levels of Sirt1 and PGC-1α. These changes were reversed by RSV. We also demonstrated that AMPK regulates the modulations of Sirt1 and PGC-1α using specific inhibitors of AMPK and Sirt1 and small interfering RNAs of PGC-1α. In summary, the current study demonstrates that RSV is effective against high glucose-induced cellular apoptosis and its action is exerted via the inhibition of ROS/AMPK/Sirt1/PGC-1α pathway.

Deacetylation of MnSOD by PARP-regulated SIRT3 protects retinal capillary endothelial cells from hyperglycemia-induced damage

A key initiator in the development of diabetic retinopathy is considered to be the production of reactive oxygen species (ROS) in the retinal mitochondria, and their scavenging enzyme, manganese superoxide dismutase (MnSOD), is compromised. However, the mechanism by which high glucose regulates MnSOD is unclear. In this study, we found that a high concentration of glucose inhibited the expression of the histone deacetylase SIRT3, which resulted in a reduction in MnSOD activity in bovine retinal capillary endothelial cells and in the retinas of diabetic rats. Conversely, SIRT3 overexpression attenuated hyperglycemic stress through deacetylation and activation of MnSOD. Furthermore, the hyperglycemia-induced downregulation of SIRT3 involved the activation of poly (ADP-ribose) polymerase (PARP). Our study is the first to link the deacetylation of MnSOD by PARP-regulated SIRT3 with the pathogenesis of diabetic retinopathy. Understanding the role of SIRT3 in the pathogenesis of diabetic retinopathy could help elucidate key molecular targets for future pharmacological interventions.

Sirtuin 1–Mediated Cellular Metabolic Memory of High Glucose Via the LKB1/AMPK/ROS Pathway and Therapeutic Effects of Metformin

Cellular metabolic memory occurs in diabetic microvascular and macrovascular complications, but the underlying mechanisms remain unclear. Here, we investigate the role of sirtuin 1 (SIRT1) and metformin in this phenomenon. In bovine retinal capillary endothelial cells (BRECs) and retinas of diabetic rats, the inflammatory gene, nuclear factor-κB (NF-κB), and the proapoptotic gene, Bax, induced by hyperglycemia, remained elevated after returning to normoglycemia. BRECs with small interfering RNA–mediated SIRT1 knockdown had increased sensitivity to hyperglycemia stress, whereas SIRT1 overexpression or activation by metformin inhibited the increase of mitochondrial reactive oxygen species–mediated glyceraldehyde-3-phosphate dehydrogenase by poly (ADP-ribose) polymerase (PARP) activity through the upregulation of liver kinase B1/AMP-activated protein kinase (LKB1/AMPK), ultimately suppressing NF-κB and Bax expression. Furthermore, we showed that hyperglycemia led to PARP activation, which in turn may have downregulated SIRT1. Of importance, this study also demonstrated that metformin suppressed the “memory” of hyperglycemia stress in the diabetic retinas, which may be involved in the SIRT1/LKB1/AMPK pathway. Our data suggest that SIRT1 is a potential therapeutic target for the treatment of the cellular metabolic memory, and the use of metformin specifically for such therapy may be a new avenue of investigation in the diabetes field.

Tyrosine phosphorylation of VE-cadherin and claudin-5 is associated with TGF-β1-induced permeability of centrally derived vascular endothelium

Breakdown of the inner blood–retinal barrier and the blood–brain barrier is associated with changes in tight and adherens junction-associated proteins that link vascular endothelial cells. This study aimed to test the hypothesis that transforming growth factor (TGF)-β1 increases the paracellular permeability of vascular endothelial monolayers through tyrosine phosphorylation of VE-cadherin and claudin-5. Bovine retinal and human brain capillary endothelial cells were grown as monolayers on coated polycarbonate membranes. Paracellular permeability was studied by measuring the equilibration of 14C-inulin or fluorescence-labelled dextran. Changes in VE-cadherin and claudin-5 expression were studied by immunocytochemistry (ICC) and quantified by cell-based enzyme linked immunosorbent assays (ELISA). Tyrosine phosphorylation of VE-cadherin and claudin-5 was studied by ICC, immunoprecipitation and Western blotting. We found that exposure of endothelial cells to TGF-β1 caused a dose-dependent increase in paracellular permeability as reflected by increases in the equilibration of 14C-inulin. This effect was enhanced by the tyrosine phosphatase inhibitor orthovanadate and attenuated by the tyrosine kinase inhibitor lavendustin A. ICC and cell-based ELISA revealed that TGF-β1 induced both dose- and time-dependent decreases in VE-cadherin and claudin-5 expression. Assessment of cell viability indicated that changes in these junction-associated proteins were not due to endothelial death or injury. ICC revealed that tyrosine phosphorylation of endothelial monolayers was greatly enhanced by TGF-β1 treatment, and immunoprecipitation of cell lysates showed increased tyrosine phosphorylation of VE-cadherin and claudin-5. Our results suggest that tyrosine phosphorylation of VE-cadherin and claudin-5 is involved in the increased paracellular permeability of central nervous system-derived vascular endothelium induced by TGF-β1.

GLUT-1 Expression in Bovine Retinal Capillary Endothelial Cells and Pericytes Exposed to Advanced Glycation End Products

Glucose uptake and glucose transporter GLUT-1 expressions are characteristic of retinal capillary endothelial cells and pericytes in response to high glucose. In this study, the effects of advanced glycation end product (AGE-BSA) exposure on these parameters were tested. Primary cultures of bovine retinal capillary endothelial cells (BRECs) and bovine retinal capillary pericytes (BRPs) were exposed to AGE-BSA (100 μg/mL) for 6 days. Glucose uptake was measured using U (14)C-glucose and the GLUT-1 mRNA expression by RT-PCR. GLUT-1 protein was detected by immunofluorescence and subjected to FACS analysis. The authors observed that there was no significant decrease in the GLUT-1 protein expression, and this was confirmed by glucose uptake by (14)C-labeled glucose in both BRECs and BRPs. Even though there was a slight decrease in the mRNA expression of GLUT-1 in AGE-BSA-treated cells compared with both untreated control and BSA treated, the decrease was not significant. This is the first report to show that there is no difference in glucose uptake in BRECs and BRPs on exposure to AGE-BSA.

Improvement of Retinal Vascular Injury in Diabetic Rats by Statins Is Associated With the Inhibition of Mitochondrial Reactive Oxygen Species Pathway Mediated by Peroxisome Proliferator–Activated Receptor γ Coactivator 1α

OBJECTIVEMitochondrial reactive oxygen species (ROS) plays a key role in diabetic retinopathy (DR) pathogenesis. However, whether simvastatin decreases diabetes-induced mitochondrial ROS production remains uncertain. The aim of this study was to clarify the beneficial effects and mechanism of action of simvastatin against diabetes-induced retinal vascular damage.RESEARCH DESIGN AND METHODSDiabetic rats and control animals were randomly assigned to receive simvastatin or vehicle for 24 weeks, and bovine retinal capillary endothelial cells (BRECs) were incubated with normal or high glucose with or without simvastatin. Vascular endothelial growth factor (VEGF) and peroxisome proliferator–activated receptor γ coactivator 1α (PGC-1α) in the rat retinas or BRECs were examined by Western blotting and real-time RT-PCR, and poly (ADP-ribose) polymerase (PARP), and p38 MAPK were examined by Western blotting. Mitochondrial membrane potential (Δψm) and ROS production were assayed using the potentiometric dye 5,5′,6,6′- Tetrachloro1,1′,3,3′-tetraethyl-benzimidazolylcarbocyanine iodide (JC-1) or CM-H2DCFDA fluorescent probes.RESULTSSimvastatin significantly upregulated PGC-1α (P < 0.01), subsequently decreased Δψm (P < 0.05) and ROS generation (P < 0.01), inhibited PARP activation (P < 0.01), and further reduced VEGF expression (P < 0.01) and p38 MAPK activity (P < 0.01). Those changes were associated with the decrease of retinal vascular permeability, retinal capillary cells apoptosis, and formation of acellular capillaries.CONCLUSIONSSimvastatin decreases diabetes-induced mitochondrial ROS production and exerts protective effects against early retinal vascular damage in diabetic rats in association with the inhibition of mitochondrial ROS/PARP pathway mediated by PGC-1α. The understanding of the mechanisms of action of statins has important implications in the prevention and treatment of mitochondrial oxidative stress-related illness such as DR.

Homocysteinethiolactone and Paraoxonase

OBJECTIVEParaoxonase (PON) exhibits esterase activity (PON-AREase) and lactonase activity (PON-HCTLase), which prevent LDL oxidation and detoxify homocysteine thiolactone (HCTL). The role of HCTL and PON-HCTLase as a risk factor for the microvascular complication in diabetic retinopathy at the level of vitreous has not been investigated.RESEARCH DESIGN AND METHODSUndiluted vitreous from patients with proliferative diabetic retinopathy (PDR) (n = 13) and macular hole (MH) (n = 8) was used to determine PON-HCTLase and PON-AREase activity spectrophotometrically. HCTL levels were detected by liquid chromatography–tandem mass spectrometry. In vitro studies were done in primary cultures of bovine retinal capillary endothelial cells (BRECs) to determine the dose- and time-dependent effect of HCTL and homocysteine (Hcys) on PON-HCTLase activity, as well as to determine mRNA expression of PON by RT-PCR.RESULTSA significant increase in HCTL and PON-HCTLase activity was observed in PDR compared with MH (P = 0.036, P = 0.001), with a significant positive correlation between them (r = 0.77, P = 0.03). The in vitro studies on BRECs showed a dose- and time-dependent increase in the PON-HCTLase activity and mRNA expression of PON2 when exposed to HCTL and Hcys.CONCLUSIONSThis is the first study showing elevated levels of vitreous HCTL and PON-HCTLase activity in PDR. These elevations are probably a protective effect to eliminate HCTL, which mediates endothelial cell dysfunction. Thus, vitreous levels of HCTL and PON activity can be markers of diabetic retinopathy. The bioinformatics analysis reveals that the structure and function of PON that can be modulated by hyperhomocysteinemia in PDR can affect the dual-enzyme activity of PON.

Antiangiogenic effects and transcriptional regulation of pigment epithelium-derived factor in diabetic retinopathy

The effects of the antiangiogenic cytokine PEDF on key steps in retinal angiogenesis, specifically endothelial cell proliferation and vascular tubule formation, and the regulation of PEDF expression in retinal capillary endothelial cells were evaluated. HUVECs were co-cultured with fibroblasts to construct a model of angiogenesis using the Angiokit assay, and image analysis software was used to measure the effects of PEDF and VEGF on vascular tubule formation. Quantitative real-time PCR analysis was used to determine the expression of PEDF in microvascular endothelial cells exposed to glucose 20mM, insulin 100nM and VEGF 10ng/ml. PEDF inhibited endothelial cell proliferation and significantly decreased the number of tubules (629+93AU vs 311+31, p=0.001), number of branching points (145+19AU vs 46+5, p=0.03) and total tubule length (4848+748AU vs 11,172+2353, p=0.001). In bovine retinal capillary endothelial cells (BRCECs), PEDF mRNA and protein expression was suppressed by insulin (22%) in a rapamycin-sensitive manner; wortmannin had no effect. PEDF mRNA expression was also significantly reduced in the presence of high glucose (23%) and VEGF (25%). In conclusion, PEDF inhibits key steps in the angiogenic response of BRCECs, including endothelial cell proliferation and vascular tubule formation. Gene expression of PEDF is negatively regulated by glucose, insulin (via an mTOR-dependent pathway) and VEGF.

PRMT-1 and DDAHs-induced ADMA upregulation is involved in ROS- and RAS-mediated diabetic retinopathy

Asymmetric dimethylarginine (ADMA), an endogenous competitive inhibitor of nitric oxide synthase, is generated in presence of type 1 protein arginine N-methyltransferase (PRMT-1) and is metabolized by dimethylarginine dimethylaminohydrolases (DDAHs). Reportedly ADMA is associated with endothelial dysfunction. The aim of this study is to investigate whether PRMT-1- and DDAHs-induced ADMA increase in diabetic rat retina and high glucose-treated bovine retinal capillary endothelial cells (BRCECs) is involved in reactive oxygen species (ROS)- and renin–angiotensin system (RAS)-mediated diabetic retinopathy. Rats were divided into four groups: sham-injected group, streptozotocin (STZ)-induced diabetic model group, STZ-induced diabetic model plus 12-week ACEI benazepril treatment group, and STZ-induced diabetic model plus 12-week ARB telmisartan treatment group. BRCECs were exposed to 5 mM glucose, 30 mM glucose, and 30 mM glucose plus benazepril, telmisartan, diphenyliodonium (NADPH oxidase inhibitor, DPI), or N-Acetyl- l-cysteine (antioxidant and free radical scavenger, NAC) until passage four. We found that the concentrations of ADMA were significantly elevated in the plasma of diabetic rat models, and were significantly reduced by benazepril or telmisartan. DDAHs expression was decreased and PRMT-1 expression was increased in diabetic rat retina, which was reversed by benazepril. Telmisartan decreased PRMT-1 expression and increased DDAH II expression, but had no effect on DDAH I expression. In vitro, BRCECs exposed to high glucose had elevated ROS production, decreased cGMP, increased PRMT-1 expression, and decreased DDAH activity and DDAH II expression. Coincubating BRCECs with benazepril, telmisartan, DPI or NAC reversed the effects of high glucose. It can be concluded that PRMT-I and DDAHs-induced upregulation of ADMA levels might be involved in ROS- and RAS-mediated diabetic retinopathy.

Inhibition of Pathologic Retinal Neovascularization by a Small Peptide Derived from Human Apolipoprotein(a)

To evaluate the effect of KV11, a novel 11-mer peptide from human apolipoprotein(a), against retinal neovascularization and to study its penetration and the possible toxicity to the retina. Wound-healing, a modified Boyden chamber, and MTS assays were used to evaluate the effect of KV11 on the migration and proliferation of bovine retinal capillary endothelial cells (BRCECs) induced by vascular endothelial growth factor (VEGF) in vitro. The antiangiogenic effect of KV11 was also studied with a mouse model of oxygen-induced retinopathy. Then, FITC-labeled KV11 was injected into the vitreous of normal rabbits, the retinal penetration was determined by confocal laser-scanning microscope, and further confirmed by UPLC/MS analysis of KV11 in tissue extracts. Electrophysiological tests and histologic examinations were used to study the possible toxicity of KV11 against rabbit neuroretina after intravitreal administration. KV11 inhibited VEGF-induced BRCEC migration but not proliferation and reduced the pathologic neovascularization in a mouse model, without affecting normal retinal vasculature. FITC-labeled KV11 appeared in the retina within 30 minutes after injection and diffused to all layers 3 hours later. The transfer of KV11 from the vitreous to the retina was confirmed by UPLC/MS data. Electrophysiologic tests and histologic examinations revealed no evident functional or morphologic abnormalities in rabbit neuroretina after KV11 injection. It is concluded that the novel peptide KV11 is an effective inhibitor of retinal pathologic angiogenesis with a sufficient retinal penetration and a favorable safety profile and may provide a promising alternative for ocular antiangiogenic therapy.

Systemic administration of HMG-CoA reductase inhibitor protects the blood–retinal barrier and ameliorates retinal inflammation in type 2 diabetes

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) are frequently used lipid-lowering drugs in type 2 diabetes. Recent emerging evidence suggests that statins protect cardiovascular function via lipid-independent mechanisms. However, the potential role of statins in diabetic retinopathy in type 2 diabetes is largely unclear. In the present study we have investigated the effect of lovastatin on blood–retinal barrier and inflammatory status in the retina of db/db mice and in cultured retinal cells. Male C57BL/KsJ db/db mice were randomly chosen to receive gastric gavage of lovastatin (10 mg/kg/day) or vehicle control for 6 weeks. Retinal vascular permeability, the tight junction and inflammation were determined. The results showed that db/db mice at the age of 19 weeks exhibited significantly increased retinal vascular leakage and decreased tight junction protein level in the retina. Moreover, the expression of pro-inflammatory factors, e.g. ICAM-1 and TNF-α, was drastically up-regulated in diabetic retina. Lovastatin treatment normalized all of these changes. In cultured bovine retinal capillary endothelial cells (RCECs) and human ARPE-19 cells, lovastatin attenuated the decrease of tight junction protein (occludin) and adherens junction protein (VE-cadherin) expression-induced by TNF-α, a major pro-inflammatory cytokine in diabetic retinopathy. Lovastatin also attenuated TNF-α expression in RCEC. Towards the mechanism, we showed that lovastatin ameliorated ICAM-1 expression-induced by hypoxia and TNF-α in both RCECs and ARPE-19 cells, in part through inhibition of NF-κB activation. Taken together, these findings indicate that lovastatin protects blood–retinal barrier in diabetic retinopathy, which is likely via its anti-inflammatory effects.

Protective Effect of Perindopril on Diabetic Retinopathy Is Associated With Decreased Vascular Endothelial Growth Factor–to–Pigment Epithelium–Derived Factor Ratio

OBJECTIVEThis study aimed to verify whether the decreased vascular endothelial growth factor (VEGF)–to–pigment epithelium–derived factor (PEDF) ratio can serve as an indicator for the protective effect of angiotensin-converting enzyme inhibitors (ACEIs) on diabetic retinopathy (DR) and to investigate the role of mitochondrial reactive oxygen species (ROS) in the downregulated VEGF-to-PEDF ratio.RESEARCH DESIGN AND METHODSDiabetic rats and control animals were randomly assigned to receive perindopril or vehicle for 24 weeks, and bovine retinal capillary endothelial cells (BRECs) were incubated with normal or high glucose with or without perindopril. VEGF, PEDF, PPARγ, and uncoupling protein-2 (UCP-2) in the rat retinas or BREC extracts were examined by Western blotting and real-time RT-PCR. The levels of VEGF and PEDF in cell culture media were examined by ELISA. Mitochondrial membrane potential (Δψm) and ROS production were assayed using JC-1 or CM-H2DCFDA.RESULTSThe VEGF-to-PEDF ratio was increased in the retina of diabetic rats; perindopril lowered the increased VEGF-to-PEDF ratio in diabetic rats and ameliorated the retinal damage. In BRECs, perindopril lowered the hyperglycemia-induced elevation of VEGF-to-PEDF ratio by reducing mitochondrial ROS. We found the decreased ROS production was a result of perindopril-induced upregulation of PPARγ and UCP-2 expression and the subsequent decrease of Δψm.CONCLUSIONSIt is concluded that the protective effect of ACEI on DR is associated with a decreased VEGF-to-PEDF ratio, which involves the mitochondria-ROS pathway through PPARγ-mediated changes of UCP-2. This study paves a way for future application of ACEI in treatment of DR.

Fractalkine, a CX3C Chemokine, as a Mediator of Ocular Angiogenesis

Fractalkine (FKN) is a chemoattractant and adhesion molecule for leukocytes. Angiogenic effect of FKN also has been reported. This study was an investigation of FKN-mediated angiogenesis in vitro and in vivo to determine its role in ocular angiogenic disorders. FKN effects on cultured human umbilical vein endothelial cells (HUVECs) and bovine retinal capillary endothelial cells (BRECs) were evaluated with chemotaxis assay and a synthetic matrix capillary tube formation assay in vitro. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis were used to detect mRNA and protein expression of FKN and its receptor, CX3CR1, in HUVECs and BRECs. A rabbit corneal neovascularization assay and an oxygen-induced retinopathy (OIR) model of mice were used to test the angiogenic property of FKN in vivo. FKN levels of vitreous samples from patients with proliferative diabetic retinopathy were measured by enzyme-linked immunosorbent assay (ELISA). Immunodepletion of FKN in PDR vitreous samples by anti-FKN polyclonal antibody was observed in endothelial cell chemotaxis assays. FKN significantly induced migration of HUVECs and BRECs. FKN induced formation of endothelial cell capillary tubes on synthetic matrix. Expression of FKN and CX3CR1 was detected in HUVECs and BRECs by RT-PCR and Western blot analysis. FKN significantly induced more blood vessel growth than did the control in the rabbit corneal pocket neovascularization assay. Intravitreal injection of anti-mouse FKN antibody decreased retinal angiogenesis in the OIR model. The vitreous level of FKN was elevated in patients with PDR compared with control subjects. Immunodepletion of soluble FKN from PDR vitreous samples caused 36.6% less migration of BRECs. FKN is an angiogenic mediator in vitro and in vivo. The vitreous level of FKN was elevated in patients with PDR. FKN may play an important role in ocular angiogenic disorders such as PDR.

Contextual role for angiopoietins and TGFβ1 in blood vessel stabilization

We used a 3D in-vitro model of angiogenesis to investigate the effects of different growth factors on vessel formation and stabilization in vitro. Vascular endothelial growth factor (VEGF) was the only factor that induced the formation, elongation and sprouting of capillary-like structures (CLS) by bovine retinal capillary endothelial cells (BREC), an effect that was dose-dependent and saturable. Basic fibroblast growth factor 2 (FGF2) enhanced capillary formation in the presence of VEGF, leading to a more complex network of CLS and a higher rate of BrdU incorporation than VEGF alone, indicating that whereas VEGF acts as a morphogen, FGF2 is primarily a mitogen. Addition of transforming growth factor beta1 (TGFbeta1) to the 3D assay along with VEGF and FGF2, reduced tube formation in a dose-dependent manner. When added at the time of cell plating TGFbeta1 completely suppressed formation of VEGF/FGF2-stimulated CLS. Angiopoietin 1 (Ang1) prevented regression of the TGFbeta1-induced CLS, an effect that was blocked by angiopoietin 2 (Ang2), but required the continuous presence of VEGF.

Effects of D- and L-Glucose and Mannitol on Retinal Capillary Cells: Inhibition by Nanomolar Aminoguanidine

Hyperglycemia may contribute directly to pericyte loss and capillary leakage in early diabetic retinopathy. To elucidate relative contributions of glycation, glycoxidation, sugar autoxidation, osmotic stress and metabolic effects in glucose-mediated capillary damage, we tested the effects of D-glucose, L-glucose, mannitol and the potentially protective effects of aminoguanidine on cultured bovine retinal capillary pericytes and endothelial cells. Media (containing 5 mM D-glucose) were supplemented to increase the concentration of each sugar by 5, 10, or 20 mM. Subconfluent pericytes and endothelial cells were exposed to the supplemented media in the presence or absence of aminoguanidine (1 nM-100 µM) for three days. Cell counts, viability and protein were determined. For both cell types, all three sugars produced concentration-dependent decreases in cell counts and protein content (p

Effect of benfotiamine on bovine retinal capillary endothelial cells cultured in high concentration of glucose

目的 研究苯磷硫胺对体外高糖环境中培养的牛视网膜毛细血管内皮细胞的生长及细胞凋亡的影响.方法 采用MTT法观察不同浓度的苯磷硫胺对高糖培养的牛视网膜毛细血管内皮细胞增生的影响,采用流式细胞分析技术观察选定浓度的苯磷硫胺对高糖环境中培养的牛视网膜毛细血管内皮细胞的凋亡的影响.结果 MTT法显示,一定浓度的苯磷硫胺可以降低高糖对牛视网膜毛细血管内皮细胞生长的抑制作用,且呈浓度相关性.在浓度为75 μmol/L时OD值差异有统计学意义(P＜0.01).流式细胞分析技术显示,75 μmol/L的苯磷硫胺可明显减少牛视网膜毛细血管内皮细胞的凋亡.结论 一定浓度的苯磷硫胺对体外高糖环境中培养的牛视网膜毛细血管内皮细胞具有明显的保护作用,其机制可能在于苯磷硫胺能减少细胞凋亡。

Expression modification of uncoupling proteins and MnSOD in retinal endothelial cells and pericytes induced by high glucose: The role of reactive oxygen species in diabetic retinopathy

Uncoupling proteins (UCPs) are mitochondrial transporters present in the inner membrane of mitochondria. They belong to the family of anion mitochondrial carriers. UCPs could act as proton carriers activated by metabolites and create a shunt between complexes of the respiratory chain and ATP synthase. The increased leakiness of the mitochondrial inner membrane to protons may be to minimize superoxide production by limiting the maximum Δ μ H+. The purpose of this study was to detect UCP expression in retinal capillary cells and their modification in high levels of glucose. The role of reactive oxygen species (ROS) of mitochondria and UCPs in pathogenesis of diabetic retinopathy was investigated. Bovine retinal capillary endothelial cells and pericytes were cultured with selective culture media, respectively. Passage cells were cultured in three different glucose concentrations (5, 23, 30 mM) until passage four. ROS changes in mitochondria of these cells in different glucose concentrations were detected with scanning laser confocal microscopy (SLCM). The mitochondria membrane potential (Δ ψ), cell death rate and apoptosis rate were measured with flowing cytometry. UCP expression in retinal capillary cells was detected by immunocytochemistry. Expression and modification of MnSOD and uncoupling proteins (UCPs) in different concentrations of glucose were detected by means of semi-quantitative RT–PCR. ROS in mitochondria of both endothelial cells and pericytes increased as the glucose concentration of media increased. Δ ψ and cell death rate of endothelial cells increased also. ROS was correlated to Δ ψ and cell death rate positively in endothelial cells. No difference in Δ ψ and cell death rate among different glucose levels was found in pericytes. Apoptosis rate of endothelial cells and pericytes in high glucose levels was higher than that in lower glucose levels. UCP1 and UCP2 were expressed in cultured retinal capillary cells whereas UCP3 was not. At high levels of glucose, expression of UCP1, UCP2 and MnSOD increased to accommodate ROS production compensatively. The compensative mechanism disappeared when glucose concentration was too high (30 mM). The results of this study showed that increasing mitochondrial ROS could be induced by high glucose concentration. Those proteins related to antioxidation mechanism, such as MnSOD and UCPs, could exert compensative action to a certain extent. This compensative action was insufficient when the glucose concentration was too high.

Effect of Müller cell co-culture on in vitro permeability of bovine retinal vascular endothelium in normoxic and hypoxic conditions

Müller cell dysfunction may contribute to the early pathological changes associated with conditions such as diabetes, that cause breakdown of the blood–retinal barrier. In this study we used an in vitro model of the blood–retinal barrier to investigate Müller cell effects on retinal vascular endothelial cell monolayer permeability under normoxic (20% oxygen) and hypoxic (1% oxygen) conditions. Second passage bovine retinal capillary endothelial cells were co-cultured with retinal Müller cells on opposite sides of a 0.4 μm pore size polycarbonate Transwell filter or in medium that was continually conditioned by Müller cells. Permeability changes were observed for up to 24 h of hypoxia by measurement of [ 3H]-inulin and [ 14C]-albumin flux across the endothelial cell monolayer. Endothelial cell barrier function was enhanced by co-culturing with Müller cells under normoxic conditions. Under hypoxic conditions however, the barrier was significantly impaired after 12 h of co-culture with Müller cells. These results shed more light on the trophic effect of Müller cells on the blood–retinal barrier, suggesting a critical role in the maintenance and regulation of the barrier in health and during disease.

Suppression of corneal neovascularization by PEDF release from human amniotic membranes.

Human amniotic membrane (HAM) transplantation is commonly used in corneal surface reconstruction and is known to inhibit neovascularization of this tissue. The purpose of the present study is to reveal the molecular basis underlying antiangiogenic activity of HAM. The effects of HAM protein on proliferation of vascular endothelial cells and corneal epithelial cells were determined by quantifying viable cells using the MTT assay. The presence of pigment epithelium-derived factor (PEDF) in HAM was demonstrated at the protein level by Western blot analysis and immunohistochemistry using a monoclonal antibody specific to human PEDF. The PEDF concentration was measured by a specific ELISA. The expression of PEDF in HAM was confirmed at the RNA level by RT-PCR and DNA sequencing. Soluble proteins from HAM inhibited proliferation of human umbilical vein endothelial cells and bovine retinal capillary endothelial cells (BRCECs) while promoting proliferation of bovine cornea epithelial cells. Moreover, the HAM-induced inhibition of BRCECs was neutralized by a specific anti-PEDF antibody. PEDF protein was identified with an abundance of 103.84 +/- 33.21 ng/mg of soluble proteins, which is comparable to that in the retina, a PEDF-rich tissue. PEDF expression was predominantly localized in the basement membrane of HAM. RT-PCR using specific PEDF primers amplified a single product from HAM RNA. The PCR product has a sequence identical with that of human PEDF. HAM specifically inhibits endothelial cell growth and thus suppresses neovascularization in the cornea. PEDF in HAM has a major role in eliciting this antiangiogenic activity.

Transendothelial electrical resistance of bovine retinal capillary endothelial cells is influenced by cell growth patterns: an ultrastructural study.

The purpose of this study was to describe the ultrastructural features of an in vitro capillary endothelial cell model of blood-retinal barrier permeability and to relate morphological features with transendothelial electrical resistance. The electrical resistance of endothelial cell monocultures on small and large pore size polycarbonate Transwell filters was measured and compared with cocultures of endothelial cells and Müller cells. There was a wide variation in electrical resistance measurements with many preparations not achieving a functional barrier. The ultrastructural features associated with barrier function in vitro were studied by comparing cultures that exhibited a 'tight' or 'leaky' barrier when measured immediately prior to processing for electron microscopy. Preparations with low transendothelial electrical resistance were associated with irregular cell growth when studied morphologically. It was concluded that parallel light and electron microscopic studies are important for validation of in vitro models of vascular endothelial permeability.