Vascular endothelial growth factor upregulates pigment epithelium-derived factor expression via VEGFR-1 in human retinal pigment epithelial cells

Hydroquinone predisposes for retinal pigment epithelial (RPE) cell degeneration in inflammatory conditions

In addition to hypoxia, inflammation is capable of inducing vascular endothelial growth factor (VEGF) expression in human retinal pigment epithelial (RPE) cells. Excessive levels of VEGF promote choroidal neovascularization and thereby contribute to the pathogenesis of wet age-related macular degeneration (AMD). Intravitreal anti-VEGF injections ameliorate pathological vessel neoformation in wet AMD but excessive dampening of VEGF can result in a degeneration of the RPE. In the present study, we induced VEGF production by exposing human ARPE-19 cells to the pro-inflammatory IL-1α and subsequently to hydroquinone, a component of tobacco smoke that is a major environmental risk factor for AMD. Effects were monitored by measuring the levels of VEGF and anti-angiogenic pigment epithelium-derived factor (PEDF) using an enzyme-linked immunosorbent assay (ELISA) technique. In addition, we measured the production of reactive oxygen species (ROS) using the 2′,7′-dichlorofluorescin diacetate (H2DCFDA) probe and studied the effects of two anti-oxidants, ammonium pyrrolidinedithiocarbamate (APDC) and N-acetyl-cysteine (NAC), on VEGF production. Cellular and secreted VEGF as well as secreted PEDF levels were reduced at all tested hydroquinone concentrations (10, 50, or 200 µM); these effects were evident prior to any reduction of cell viability evoked by hydroquinone. Cell viability was carefully explored in our previous study and verified by microscoping in the present study. APDC further reduced the VEGF levels, whereas NAC increased them. The 50 μM concentration of hydroquinone increased ROS production in ARPE-19 cells primed with IL-1α. Hydroquinone disturbs the regulatory balance of VEGF and PEDF in inflammatory conditions. These data support the idea that hydroquinone mediates RPE degeneration by reducing VEGF levels and may predispose to dry AMD since VEGF is as well important for retinal integrity.

The biological relevance of pigment epithelium-derived factor on the path from aging to age-related disease

Pigment epithelium-derived factor (PEDF) is an endogenously produced protein that contributes to cell growth arrest, and reduced levels of PEDF are associated with the progression of cellular senescence and the aging process. However, the mechanisms underlying PEDF regulation of these events are not completely clear. Increased PEDF activity may induce anti-aging processes, suggesting the potential therapeutic value of PEDF as an anti-aging and age-related disease. In this review, we recapitulate the molecular and cellular mechanisms of aging following the characteristics and specific roles of the PEDF in cell cycle arrest and its relevance to cellular senescence and aging pathways. In this context, the discovery and fluctuations of PEDF in age-related diseases are summarised. In light of the importance of PEDF in cellular senescence and aging processes, better comprehension of the mechanism(s) of PEDF in the regulation of cell cycle and the aging process can conceivably facilitate the development of therapeutic strategies for diseases that occur with aging.

Oleic Acid, Cholesterol, and Linoleic Acid as Angiogenesis Initiators

The current study determined the natural angiogenic molecules using an unbiased metabolomics approach. A chick chorioallantoic membrane (CAM) model was used to examine pro- and antiangiogenic molecules, followed by gas chromatography-mass spectrometry (GCMS) analysis. Vessel formation was analyzed quantitatively using the angiogenic index (p < 0.05). At embryonic day one, a white streak or circle area was observed when vessel formation begins. GCMS analysis and database search demonstrated that angiogenesis may initiate when oleic, cholesterol, and linoleic acids increased in the area of angiogenic reactions. The gain of function study was conducted by the injection of cholesterol and oleic acid into a chick embryo to determine the role of each lipid in angiogenesis. We propose that oleic acid, cholesterol, and linoleic acid are natural molecules that set the platform for the initiation stage of angiogenesis before other proteins including the vascular endothelial growth factor, angiopoietin, angiotensin, and erythropoietin join as the angiome in sprout extension and vessel maturation.

Pigment Epithelium-Derived Factor Promotes the Growth and Migration of Human Esophageal Squamous Cell Carcinoma

Pigment epithelium-derived factor (PEDF) is an oncogene found in various types of cancers. However, how PEDF affects the development of human esophageal squamous cell carcinoma (ESCC) is unknown. This study investigates the role of PEDF in ESCC cell proliferation, migration, and cell cycle both in vitro and in vivo. The PEDF expression was examined in patient tumor samples and ESCC cell lines. Short hairpin RNA technology was used to inhibit the PEDF expression in ESCC EC9706 and KYSE150 cells. In vitro cell proliferation and migration assays were performed. The effects of PEDF on tumor growth and progression were examined in vivo in murine subcutaneous xenograft tumor models. It was found that PEDF was overexpressed in esophageal cancer cells and patient tumor tissues compared to normal control samples. PEDF enhanced cell cycle progression and inhibited cell apoptosis. Knock down of PEDF inhibited esophageal cell proliferation and migration in vitro. Moreover, Inhibition of PEDF significantly reduced tumor growth and tumor size in vivo. These results indicate that PEDF induce tumorigenesis in ESCC and can be a potential therapeutic target for cancer treatment.

The role of pigment epithelium-derived factor in protecting against cellular stress

Since its discovery as a neurotrophic factor in retinal pigmented epithelium cells in the late 1980s, there has been an increase in understanding of the role that pigment epithelium-derived factor (PEDF) plays in cellular functions. PEDF plays an important role in mediating cellular protection during exposure to oxidative stress and inflammation by preventing stress-induced angiogenesis and apoptosis. PEDF acts to reduce oxidative stress by promoting mitochondrial stability and by regulating the expression of enzymes involved in ROS accumulation and clearance. PEDF protects against the negative effects of oxidative stress by regulating cell survival pathways and the expression of inflammatory and proangiogenic mediators. PEDF-mediated cellular protection may be of clinical importance in diseases characterised by oxidative stress, chronic inflammation and pathological neovascularization, indicating that targeting PEDF may be a potential focus for therapeutic interventions in chronic diseases. In this review, we provide a historical perspective on the discoveries of PEDF interactions and functions, and discuss recent in vitro, in vivo and clinical findings to provide a current summary of the important protective effects following cellular exposure to stress stimuli and future clinical potential of PEDF.

Effect of basal insulin supplement therapy on diabetic retinopathy in short-duration type 2 diabetes: A one-year randomized parallel-group trial

BACKGROUND

In this study, we compared the effect on diabetic retinopathy (DR) between oral antidiabetic drugs (OADs) alone and in combination with basal insulin-supported OADs therapy (BOT). [Correction added on 11 November 2019, after first online publication: In Abstract under Background section, "DR" has been corrected into "diabetic retinopathy (DR)".] METHODS: Between January 2015 and January 2018, this study enrolled 290 patients (age 18-65 years) with diabetes duration between 0 and 5 years. Patients were randomly assigned to receive OADs or BOT after 14 days intensive insulin treatment. Examinations were performed at the beginning and end of the study.

RESULTS

Fewer patients developed DR in the BOT than OADs group (8 [6.06%] vs 12 [8.3%], respectively), and all cases of DR were non-proliferative. Blood glucose concentrations were higher in the BOT than OADs group at the 3rd month, but lower in the former at the 6th and 12th month. The rate of reaching target HbA1c ≤7% was lower in the BOT than OADs group at the 3rd month (63.6% vs 72.2%, respectively), similar between the two groups at the 6th month (60.6% vs 66.6%, respectively) and higher in the BOT group at the 12th month (75.0% vs 61.1%, respectively). The SD of fasting blood glucose (FBG), coefficient of variation of FBG, SD of blood glucose (SDBG), and mean amplitude of glycemic excursions were lower in the BOT than OADs group. Changes in the levels of three cytokines (interleukin [IL]-1β, IL-6, and IL-17α) were significantly less in the BOT than OADs group.

CONCLUSIONS

Twelve months of BOT decreased the incidence of DR in short-duration type 2 diabetes by reducing glycemia more effectively, stably, and completely than OADs alone.

A Comparison Study of Ranibizumab and Aflibercept in Patients with Naive Diabetic Macular Edema in Presence of Serous Retinal Detachment

Aim of the study: The aim of this study is to compare the efficacy of intravitreal injection of Aflibercept and Ranibizumab in the treatment of naive diabetic macular edema (DME) with serous retinal detachment (SRD). Materials and methods: In this prospective, non-randomized-cohort study, 60 eyes with DME with SRD were divided into 2 groups: group 1 consisted of 30 eyes treated with intravitreal injection of 0.5 mg/0.1 mL Ranibizumab (IVR) and group 2 consisted of 30 eyes treated with intravitreal injection of 2 mg/0.05 mL Aflibercept (IVA). After three sequential injections with 30-40-day interval as a loading dose, all patients were followed up for 12 months. The best-corrected visual acuity (BCVA), central macular thickness (CMT), SRD's height (SRDH) and the number of reinjections of the drugs were compared. Results: The groups were similar in terms of age and sex (p > 0.05). There was no difference between groups in terms of the baseline BCVA, CMT and SRDH (p > 0.05). There was no significant difference between groups with regard to BCVA and CMT values for 12 months (p > 0.05). SRDH decreased significantly in both groups; however, the reduction of SRDH was considerably higher in group 2 for 12 months (p < 0.05). The mean number of reinjection was 4.40 ± 0.85 in group 1 and 3.16 ± 0.75 in group 2 and it was noticeably lower in group 2 (p < 0.001). The number of cases with persistent SRD at the end of the study was 14 (46.6%) in group 1 and 5 (16.6%) in group 2 (p < 0.001). Conclusions: Aflibercept may treat SRD more efficiently in patients with DME compared to Ranibizumab with fewer injections.

Potential role of sirtuin 1 in Müller glial cells in mice choroidal neovascularization

This study investigated the potential role of sirtuin 1 in Müller glial cells in choroidal neovascularization. In the in vitro study, primary Müller glial cells were cultured and treated with resveratrol, a sirtuin 1 activator. Glial fibrillary acidic protein expression and angiogenesis-related gene expression were examined using quantitative polymerase chain reaction and phagocytosis, as a marker of Müller glial cell function; in addition, a latex bead assay was used to analyze cell function. For the in vivo study, choroidal neovascularization was induced in C57BL/6 mice via laser photocoagulation, and resveratrol was administered intravitreally. Eyecup whole mounts were created to measure choroidal neovascularization volumes on day 7. Immunohistochemical analysis with anti-glial fibrillary acidic protein antibody was used to detect Müller glial cell activation in eyes with choroidal neovascularization on day 1, 3, 5, and 7 after laser surgery. Resveratrol significantly promoted glial fibrillary acidic protein, anti-angiogenic factor, pigment epithelium-derived factor, and thrombospondin-1 expression in the cells as well as the phagocytic activities. Treatment of the choroidal neovascularization model with resveratrol resulted in early activation of Müller glial cells near choroidal neovascularization sites. Resveratrol-activated cells but not the controls migrated to the top of choroidal neovascularization sites and into the lesions from day 3. Resveratrol reduced the choroidal neovascularization size relative to controls. In conclusion, sirtuin 1 activation in Müller glial cells suppressed the development of choroidal neovascularization, and therefore, might be a therapeutic option.

Extracellular matrix nitration alters growth factor release and activates bioactive complement in human retinal pigment epithelial cells

Purpose

We have shown previously that non-enzymatic nitration (NEN) of the extracellular matrix (ECM), which serves as a model of Bruch’s membrane (BM) aging, has a profound effect on the behavior of the overlying retinal pigment epithelial (RPE) cells, including altered phagocytic ability, reduced cell adhesion, and inhibition of proliferation. We know that transplanted RPE monolayers will encounter a hostile sub-RPE environment, including age-related alterations in BM that may compromise cell function and survival. Here we use our previous NEN model of BM aging to determine the effects of NEN of the ECM on growth factor release and complement activation in RPE cells.

Methods

Human induced-pluripotent stem cells (iPSCs) were differentiated into RPE cells, and confirmed by immunohistochemistry, confocal microscopy, and polymerase chain reaction. IPSC-derived RPE cells were plated onto RPE-derived ECM under untreated or nitrite-modified conditions. Cells were cultured for 7 days and barrier function measured by transepithelial resistance (TER). Vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), and complement component C3a were measured using enzyme-linked immunosorbent assay (ELISA).

Results

On average nitrite-modified ECM increased VEGF release both apically and basally by 0.15 ± 0.014 ng/mL (p <0.0001) and 0.21 ± 0.022 ng/mL (p <0.0001), respectively, in iPSC-derived RPE cells. Nitrite-modified ECM increased PEDF release in iPSC-derived RPE cells apically by 0.16 ± 0.031 ng/mL (p <0.0001), but not basally (0.27 ± 0.015 vs. 0.32 ± 0.029 ng/mL, (p >0.05)). Nitrite-modified ECM increased production of C3a in iPSC-derived RPE cells by 0.52 ± 0.123 ng/mL (p <0.05).

Conclusion

Nitrite-modified ECM increased VEGF, PEDF release, and C3a production in human iPSC-derived RPE cells. This model demonstrates changes seen in the basement membrane can lead to alterations in the cell biology of the RPE cells that may be related to the development of age-related macular degeneration.

Inhibition of choroidal neovascularization by lentivirus-mediated PEDF gene transfer in rats

AIM

To evaluate the effects of lentivirus-mediated pigment epithelium-derived factor (PEDF) gene transfer performed in treatment of rats with established choroidal neovascularization (CNV), and investigates the mechanism by which PEDF inhibits CNV in rats.

METHODS

Brown Norway (BN) rats (n=204) were induced by exposure to a laser, and then randomly assigned to 3 groups: no treatment; treatments with intravitreal injection of lentivirus-PEDF-green fluorescent protein (GFP) or lentivirus-control GFP (free fluorescent protein). Following induction and treatment, the CNV tissue was assessed for form, size and vessel leakage by fluorescein fundus angiography (FFA), optical coherence tomography (OCT), histopathology, and examination of choroidal flat mounts. VEGF, Flk-1, and PEDF expression were evaluated by real-time polymerase chain reaction (PCR) and Western blot.

RESULTS

A stable laser-induced rat model of CNV was successfully established, and used to demonstrate lentivirus-mediated PEDG gene transfer by intravitreal injection. Expression of green fluorescence labelled PEDF was observed in the retina up to 28d after injection. An intravitreal injection of lentivirus-PEDF-GFP at 7d led to a significant reduction in the size, thickness and area of CNV showed by FFA, OCT and choroidal flat mounts. PEDF was up-regulated while VEGF and Flk-1 were down-regulated in the lentivirus-PEDF-GFP group. The differences in VEGF and Flk-1 expression in the control and lentivirus-PEDF groups at 7, 14, 21 and 28d after laser induction were all statistically significant.

CONCLUSION

Lentivirus-mediated PEDF gene transfer is effective for use in treatment of laser-induced CNV, and PEDF exerts its therapeutic effects by inhibiting expression of VEGF and Flk-1.

Evaluating VEGFR1 genetic polymorphisms as a predisposition to AMD in a cohort from northern China

OBJECTIVE

The association among genetic variants in VEGFR1 and a predisposition to age-related macular degeneration (AMD) in a northern cohort from China was evaluated.

METHODS

A retrospective case-control correlation study was conducted on 432 cases and 906 gender-and ethnicity-matched controls. Whole DNA was isolated from peripheral blood samples after the individuals underwent detailed eye examinations. Eight single nucleotide polymorphisms (SNPs) in VEGFR1 genes were genotyped for all individuals using a MALDI-TOF technique. The distribution of genotypes was analyzed for Hardy-Weinberg equilibrium and the relationships among the genotype and allele frequencies with AMD were evaluated by age-adjusted logistic regression analysis. The measurement of linkage disequilibrium (LD) was carried out by Haploview 4.2. Bonferroni testing was employed to correct for multiple comparisons.

RESULTS

Among the SNPs genotyped, p values of six SNPs were less than 0.05 between AMD cases and unaffected controls. However, after Bonferroni correction, the genotype and allele distributions of only two SNPs, rs9554322 and rs9582036 differed significantly between the controls and AMD patients. Further, the rs9554322 CC genotype conferred strong susceptibility to AMD (OR = 6.057, 95% CI: 3.099-11.839). Rs9943922 was also found to be significantly associated with AMD in the distributions for the genotype and allele recessive model (p = 0.004). The specific haplotype CA of rs9582036 and rs9554320 was associated with AMD (p = 0.035), but the correlation did not remain after correction.

CONCLUSIONS

The SNPs rs9554322, rs9582036 and rs9943922 were correlated with AMD. Gene variants in VEGFR1 were linked to a pronounced emerging risk for AMD in a population in northern China.

Antiangiogenic and antifibrogenic activity of pigment epithelium-derived factor (PEDF) in bile duct-ligated portal hypertensive rats

OBJECTIVE

Antiangiogenic strategies have been proposed as a promising new approach for the therapy of portal hypertension and chronic liver disease. Pigment epithelium-derived factor (PEDF) is a powerful endogenous angiogenesis inhibitor whose role in portal hypertension remains unknown. Therefore, we aimed at determining the involvement of PEDF in cirrhotic portal hypertension and the therapeutic efficacy of its supplementation.

DESIGN

PEDF expression profiling and its relationship with vascular endothelial growth factor (VEGF), neovascularisation and fibrogenesis was determined in bile duct-ligated (BDL) rats and human cirrhotic livers. The ability of exogenous PEDF overexpression by adenovirus-mediated gene transfer (AdPEDF) to inhibit angiogenesis, fibrogenesis and portal pressure was also evaluated in BDL rats, following prevention and intervention trials.

RESULTS

PEDF was upregulated in cirrhotic human and BDL rat livers. PEDF and VEGF protein expression and localisation in mesentery and liver increased in parallel with portal hypertension progression, being closely linked in time and space with mesenteric neovascularisation and liver fibrogenesis in BDL rats. Furthermore, AdPEDF increased PEDF bioavailability in BDL rats, shifting the net balance in the local abundance of positive (VEGF) and negative (PEDF) angiogenesis drivers in favour of attenuation of portal hypertension-associated pathological neovascularisation. The antiangiogenic effects of AdPEDF targeted only pathological angiogenesis, without affecting normal vasculature, and were observed during early stages of disease. AdPEDF also significantly decreased liver fibrogenesis (through metalloproteinase upregulation), portosystemic collateralisation and portal pressure in BDL rats.

CONCLUSIONS

This study provides compelling experimental evidence indicating that PEDF could be a novel therapeutic agent worthy of assessment in portal hypertension and cirrhosis.

Deletion of placental growth factor prevents diabetic retinopathy and is associated with Akt activation and HIF1α-VEGF pathway inhibition

A new diabetic mouse strain, the Akita.PlGF knockout ((-/-)), was generated to study the role of placental growth factor (PlGF) in the pathogenesis of diabetic retinopathy (DR). PlGF deletion did not affect blood glucose but reduced the body weight of Akita.PlGF(-/-) mice. Diabetes-induced retinal cell death, capillary degeneration, pericyte loss, and blood-retinal barrier breakdown were prevented in these mice. Protein expression of PlGF was upregulated by diabetes, particularly in vascular cells. Diabetes-induced degradation of ZO-1 and VE-cadherin was reversed due to PlGF deficiency; their expression was correlated with that of sonic hedgehog and angiopoietin-1. PlGF deletion in Akita mice resulted in an increased Akt phosphorylation. Diabetes-activated hypoxia-inducible factor (HIF)1α-vascular endothelial growth factor (VEGF) pathway, including expression of HIF1α, VEGF, VEGFR1-3, and the extent of phospho (p)-VEGFR1, p-VEGFR2, and p-endothelial nitric oxide synthase, was inhibited in the retinas of diabetic PlGF(-/-) mice. However, expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, CD11b, and CD18 was not inhibited by PlGF deletion, nor was retinal leukostasis. These results suggest that PlGF is critical for the development of DR, and its genetic deletion protects the retina from diabetic damage. Protective mechanisms are associated with Akt activation and HIF1α-VEGF pathway inhibition, but independent of retinal leukostasis in the retinas of diabetic PlGF(-/-) mice.

Pro- and antiangiogenic markers in patients with pulmonary complications of systemic scleroderma

Systemic sclerosis (SSc) is an autoimmune disorder characterized by skin and internal organs fibrosis and concomitant vascular abnormalities. Although SSc is considered mainly fibrosing disease, underlying vascular pathology plays a fundamental role in its pathogenesis. We have focused on positive and negative serum markers of angiogenesis and fibrosis (pigment epithelium-derived factor [PEDF], vascular endothelial growth factor [VEGF], and soluble VEGF receptor [sVEGFR]), in progressive SSc patients at baseline and after follow-up in relation to cardiopulmonary complications (systemic hypertension [HT], pulmonary arterial hypertension [PAH] and pulmonary fibrosis [PF]). VEGF and PEDF but not sVEGFR were reciprocally regulated in SSc progression. Moreover, VEGF/PEDF ratio significantly increased during follow up suggesting that it might be used as a biomarker of disease progression. No correlation between the studied markers and cardiopulmonary complications was observed. In conclusion, VEGF and PEDF level, and the VEGF/PEDF ratio are significantly changed in the course of SSc progression and these markers can be used to assess SSc activity.

Molecular mechanisms of retinal pigment epithelium damage and development of age-related macular degeneration

Age-related macular degeneration (AMD) is attributed to a complex interaction of genetic and environmental factors. It is characterized by degeneration involving the retinal photoreceptors, retinal pigment epithelium (RPE) and Bruch's membrane, as well as alterations in choroidal capillaries. AMD pathogenesis is strongly associated with chronic oxidative stress and inflammation that ultimately lead to protein damage, aggregation and degeneration of RPE. Specific degenerative findings for AMD are accumulation of intracellular lysosomal lipofuscin and extracellular drusens. In this review, we discuss thoroughly RPE-derived mechanisms in AMD pathology.

Vascular endothelial growth factors in retinal and choroidal neovascular diseases

Angiogenesis, or neovascularization, refers to development of new vessels from pre-existing vasculature. Retinal and choroidal neovascularization leads to oedema, haemorrhages, and fibrosis, causing visual impairment and blindness. In multiple studies, vascular endothelial growth factor (VEGF) has been shown to be the most important factor in ocular angiogenesis. Recently discovered anti-VEGF treatments have revolutionized the therapy of neovascular diseases in the eye. These agents have been shown not just to stop the angiogenic process and maintain visual acuity but also improve vision in a great proportion of patients at least during a 2-year follow-up. However, there are also problems with these agents and their delivery regimens, and new therapeutic strategies are needed. This review summarizes the most important growth factors participating in the angiogenic process in the retina and the choroid, diseases where angiogenesis plays the most devastating part causing visual impairment, as well as current antiangiogenic treatments for these diseases.

Human retinal pigment epithelium cells as functional models for the RPE in vivo

PURPOSE

The two most commonly used in vitro models of the retinal pigment epithelium (RPE) are fetal human RPE (fhRPE) and ARPE-19 cells; however, studies of their barrier properties have produced contradictory results. To compare their utility as RPE models, their morphologic and functional characteristics were analyzed.

METHODS

Monolayers of both cell types were grown on permeable membrane filters. Barrier function and cellular morphology were assessed by transepithelial resistance (TER) measurements and immunohistochemistry. Protein expression was evaluated by immunoblotting and ELISA assays, and retinoid metabolism characterized by HPLC.

RESULTS

Both cultures developed tight junctions. However, only the fhRPE cells were pigmented, uniform in size and shape, expressed high levels of RPE markers, metabolized all-trans retinal, and developed high TER (>400 Ωcm(2)). The net secretion of pigment-epithelium-derived factor (PEDF) was directed apically in both cultures, but fhRPE cells exhibited secretion rates a thousand-fold greater than in ARPE-19 cells. The net secretion of vascular endothelial growth factor (VEGF) was significantly higher in fhRPE cultures and the direction of this secretion was basolateral; while net secretion was apical in ARPE-19 cells. In fresh media, VEGF-E reduced TER in both cultures; however, in conditioned media fhRPE cells did not respond to VEGF-E administration, but retreatment of the conditioned media with anti-PEDF antibodies allowed fhRPE cells to fully respond to VEGF-E.

CONCLUSIONS

Properties of fhRPE cells align with a functionally normal RPE in vivo, while ARPE-19 cells resemble a pathologic or aged RPE. These results suggest a utility for both cell types in understanding distinct, particular aspects of RPE function.

Alterations of retinal pigment epithelium cause AMD-like retinopathy in senescence-accelerated OXYS rats

Pathogenesis of age-related macular degeneration (AMD), the leading cause of blindness in the world, remains poorly understood. This makes it necessary to create animal models for studying AMD pathogenesis and to design new therapeutic approaches. Here we showed that retinopathy in OXYS rats is similar to human AMD according to clinical signs, morphology, and vascular endothelium growth factor (VEGF) and pigment epithelium-derived factor (PEDF) genes expression. Clinical signs of retinopathy OXYS rats manifest by the age 3 months against the background of significantly reduced expression level of VEGF and PEDF genes due to the decline of the amount of retinal pigment epithelium (RPE) cells and alteration of choroidal microcirculation. The disruption in OXYS rats' retina starts at the age of 20 days and appears as reduce the area of RPE cells but does not affect their ultrastructure. Ultrastructural pathological alterations of RPE as well as develop forms of retinopathy are observed in OXYS rats from age 12 months and manifested as excessive accumulation of lipofuscin in RPE regions adjacent to the rod cells, whirling extentions of the basement membrane into the cytoplasm. These data suggest that primary cellular degenerative alterations in the RPE cells secondarily lead to choriocapillaris atrophy and results in complete loss of photoreceptor cells in the OXYS rats' retina by the age of 24 months.

Cigarette smoke-related hydroquinone dysregulates MCP-1, VEGF and PEDF expression in retinal pigment epithelium in vitro and in vivo

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of legal blindness in the elderly population. Debris (termed drusen) below the retinal pigment epithelium (RPE) have been recognized as a risk factor for dry AMD and its progression to wet AMD, which is characterized by choroidal neovascularization (CNV). The underlying mechanism of how drusen might elicit CNV remains undefined. Cigarette smoking, oxidative damage to the RPE and inflammation are postulated to be involved in the pathophysiology of the disease. To better understand the cellular mechanism(s) linking oxidative stress and inflammation to AMD, we examined the expression of pro-inflammatory monocyte chemoattractant protein-1 (MCP-1), pro-angiogenic vascular endothelial growth factor (VEGF) and anti-angiogenic pigment epithelial derived factor (PEDF) in RPE from smoker patients with AMD. We also evaluated the effects of hydroquinone (HQ), a major pro-oxidant in cigarette smoke on MCP-1, VEGF and PEDF expression in cultured ARPE-19 cells and RPE/choroids from C57BL/6 mice.

PRINCIPAL FINDINGS

MCP-1, VEGF and PEDF expression was examined by real-time PCR, Western blot, and ELISA. Low levels of MCP-1 protein were detected in RPE from AMD smoker patients relative to controls. Both MCP-1 mRNA and protein were downregulated in ARPE-19 cells and RPE/choroids from C57BL/6 mice after 5 days and 3 weeks of exposure to HQ-induced oxidative injury. VEGF protein expression was increased and PEDF protein expression was decreased in RPE from smoker patients with AMD versus controls resulting in increased VEGF/PEDF ratio. Treatment with HQ for 5 days and 3 weeks increased the VEGF/PEDF ratio in vitro and in vivo.

CONCLUSION

We propose that impaired RPE-derived MCP-1-mediated scavenging macrophages recruitment and phagocytosis might lead to incomplete clearance of proinflammatory debris and infiltration of proangiogenic macrophages which along with increased VEGF/PEDF ratio favoring angiogenesis might promote drusen accumulation and progression to CNV in smoker patients with dry AMD.

Pigment epithelium-derived factor and vascular endothelial growth factor in branch retinal vein occlusion with macular edema

BACKGROUND

We investigated whether pigment epithelium-derived factor (PEDF) or vascular endothelial growth factor (VEGF) influence macular edema in patients with branch retinal vein occlusion (BRVO). This investigation aimed to clarify the influence of PEDF in the vitreous fluid on retinal vascular permeability in patients with macular edema secondary to BRVO. The findings were expected to be useful for the treatment of macular edema in BRVO patients.

METHODS

This was a retrospective cross-sectional comparative case series. Thirty-three BRVO patients with macular edema and 24 control patients with nonischemic ocular diseases were enrolled. Retinal ischemia was evaluated by measuring the area of capillary nonperfusion on fluorescein angiography with Scion Image software. Macular edema was examined by optical coherence tomography. Vitreous fluid samples were obtained via pars plana vitrectomy, and the VEGF and PEDF levels were determined by enzyme-linked immunosorbent assay.

RESULTS

The vitreous level of VEGF was significantly higher in BRVO patients than controls (P < 0.001). The vitreous PEDF level was significantly lower in BRVO patients than controls (P = 0.026). In BRVO patients, vitreous levels of PEDF and VEGF showed a significant negative correlation with each other (P < 0.001). Additionally, the vitreous VEGF level had a significant positive correlation (P < 0.001) and the vitreous PEDF level had a significant negative correlation (P < 0.001) with the nonperfused retinal area in BRVO patients. Furthermore, vitreous levels of VEGF and PEDF showed significant positive (P = 0.001) and negative (P = 0.014) correlations, respectively, with macular edema in BRVO patients.

CONCLUSIONS

VEGF and PEDF may inversely influence retinal vascular permeability in patients with ischemic BRVO and macular edema. However, prospective validation will be needed to confirm these observations.

The yin and yang of VEGF and PEDF: multifaceted neurotrophic factors and their potential in the treatment of Parkinson's Disease

Over the last few decades, vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) have emerged as multifaceted players in not only the pathogenesis, but potential treatment, of numerous diseases. They activate diverse intracellular signaling cascades known to have extensive crosstalk, and have been best studied for their effects in cardiology and cancer biology. Recent work with the two factors indicates that the activity of one growth factor is often directly related to the action of the other. Their respective neuroprotective effects, in particular, raise important questions regarding the treatment of neurodegenerative disorders, including Parkinson’s disease.

[Intravitreal ranibizumab for choroidal neovascularization secondary to pathological myopia: 12-month results]

PURPOSE

To evaluate the efficacy and safety of intravitreal ranibizumab (Lucentis) in the first-line treatment of choroidal neovascularization (CNV) secondary to pathological myopia.

METHODS

Consecutive series of patients with primary subfoveal CNV secondary to pathological myopia treated with intravitreal ranibizumab 0.5mg (0.05ml) were included prospectively in this study. Best-corrected visual acuity, fundus examination, fluorescein angiography, optical coherence tomography, and the presence of metamorphopsia were assessed at baseline and then monthly. Indications for retreatment were persistent leakage from CNV shown on FA and/or evidence of CNV activity on OCT.

RESULTS

Eight eyes of seven patients were followed from November 2007 to April 2009. The mean age was 61 years. None of these eyes had been treated previously with photodynamic therapy or direct photocoagulation. The mean spherical equivalent refractive error was -10.75 (range: -7.75 to -15.75). Follow-up was 12 months or more for all patients except one (3 months). The mean number of intravitreal injections administered for each patient was 1.5 (range: 1-4). Six eyes received one ranibizumab injection, one eye received two, and one eye received four. Four eyes demonstrated a gain in visual acuity, three eyes stabilization, and one eye vision loss. No injection complications or drug-related side effects were noted during the follow-up period.

CONCLUSIONS

In this small series of eyes with limited follow-up, intravitreal ranibizumab was a safe and effective treatment for CNV secondary to pathological myopia, resulting in functional and anatomic improvements.

Mediators of ocular angiogenesis

Angiogenesis is the formation of new blood vessels from pre-existing vasculature. Pathologic angiogenesis in the eye can lead to severe visual impairment. In our review, we discuss the roles of both pro-angiogenic and anti-angiogenic molecular players in corneal angiogenesis, proliferative diabetic retinopathy, exudative macular degeneration and retinopathy of prematurity, highlighting novel targets that have emerged over the past decade.

Changes in aqueous vascular endothelial growth factor and pigment epithelium-derived factor after ranibizumab alone or combined with verteporfin for exudative age-related macular degeneration

PURPOSE

To investigate changes in aqueous vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) after ranibizumab (Lucentis; Genentech Inc, South San Francisco, California, USA) monotherapy or combined with photodynamic therapy (PDT).

DESIGN

Prospective, interventional, case-control study.

METHODS

We recruited 34 patients with CNV secondary to AMD and 10 controls. Baseline examinations, including visual acuity (VA), central macular thickness (CMT), fluorescein angiography, and indocyanine angiography, were performed, and the measurements of VA and CMT were repeated 1 month after treatments. Seventeen of 34 patients received a single intravitreal injection of 0.5 mg ranibizumab, and the remaining 17 patients underwent combined PDT on the same day. Aqueous samples were collected at the time of injection and 1 month after treatment and were measured by enzyme-linked immunosorbent assay. Main outcomes measures were the changes in VA and CMT and the changes in VEGF and PEDF levels.

RESULTS

Demographic features, lesion characteristics, and mean changes in VA and CMT were similar between the two groups. Aqueous VEGF and PEDF levels were reduced significantly 1 month after treatment in all patients. The reduction levels of VEGF and PEDF were similar between the two groups. There was a positive correlation between the reduction levels of aqueous VEGF and the reduction levels of aqueous PEDF. The reduction levels of VEGF and PEDF were correlated positively with the decrease in CMT, but were not positively correlated with the improvements in VA.

CONCLUSIONS

Ranibizumab therapy for CNV secondary to AMD is associated with reduced levels of aqueous VEGF and PEDF regardless of combined therapy with PDT. The reduction levels of VEGF and PEDF are correlated with anatomic improvements in the macula.

Beta-adrenergic receptor regulation of growth factor protein levels in human choroidal endothelial cells

Remodeling of the choroidal vasculature is a prominent factor in age-related macular degeneration. While many of the growth factors involved in this vascular remodeling are known, their regulation remains much less so. The hypothesis of the present study was that stimulation of human choroidal endothelial cells with the beta-adrenergic receptor agonist isoproterenol would lead to an increase in pigment epithelial derived factor (PEDF) and angiopoietin 1 (Ang1), markers of a stable vasculature. Protein levels of PEDF and Ang1 were significantly increased following stimulation with isoproterenol. However, isoproterenol also significantly increased protein levels of vascular endothelial cell growth factor, which is active during vasculature remodeling. These data suggest that beta-adrenergic receptor agonists are likely upstream of a number of growth factors implicated in ocular disease and have multiple effects on choroidal endothelial cells. Modulation of this signaling in the choroid may offer a new avenue for therapeutics.

Intravitreal ranibizumab (Lucentis) for the treatment of myopic choroidal neovascularization

BACKGROUND

Macular choroidal neovascularization (CNV) is one of the most vision-threatening complications of myopia, which can lead to severe vision loss. The purpose of this study was to evaluate the safety and efficacy of intravitreal ranibizumab in the treatment of myopic CNV.

METHODS

We conducted a prospective, consecutive, interventional study of patients with subfoveal or juxtafoveal CNV secondary to pathologic myopia (PM) treated with intravitreal injection of ranibizumab in the Jules Gonin University Eye Hospital from June 2006 to February 2008. Best-corrected visual acuity (BCVA), optical coherence tomography (OCT), and fluorescein angiography (FA) were performed at baseline and monthly for all patients. Indications for retreatment were loss in BCVA associated either with persistent leakage from CNV shown on FA, and/or evidence of CNV activity on OCT.

RESULTS

The study included 14 eyes of 14 patients. The mean spherical equivalent refractive error was -12.5 (range, -8.0 D to -16.0 D). Mean time of follow-up was 8.4 months (range from 3 to 16 months, SD: 3). The mean number of intravitreal injections administered for each patient was 2.36 (SD 1.5). The mean initial visual acuity (VA) was 0.19 decimal equivalent (log-MAR: 0.71, SD: 0.3). A statistically significant improvement to a mean VA of 0.48 decimal equivalent (log-MAR:0.32, SD: 0.25) was demonstrated at the final follow-up. VA improved by a mean of 3.86 (SD 2.74) lines. Nine patients (64%) demonstrated a gain of 3 or more lines. Mean central macular thickness (CMT) measured with OCT was 304 microm (SD: 39) at the baseline, and was reduced significantly at the final follow-up to 153 microm (SD: 23). Average CMT reduction was 170 microm (SD: 57). No injection complications or drug-related side effects were noted during the follow-up period.

CONCLUSIONS

In this small series of eyes with limited follow-up, intravitreal ranibizumab was a safe and effective treatment for CNV secondary to PM, resulting in functional and anatomic improvements.

Expression of vasohibin, an antiangiogenic factor, in human choroidal neovascular membranes

PURPOSE

To determine whether vasohibin, an antiangiogenic factor produced by vascular endothelial cells, is expressed in the choroidal neovascular (CNV) membranes obtained from human eyes with age-related macular degeneration (AMD) or polypoidal choroidal vasculopathy (PCV).

DESIGN

Retrospective, interventional case series.

METHODS

The medical charts of 21 eyes of 21 patients with AMD or PCV who underwent surgical removal of the CNV membrane were reviewed. The removed tissues were immunostained for von Willebrand Factor (vWF), vascular endothelial growth factor (VEGF), and vasohibin. The levels of the messenger ribonucleic acid of VEGF, VEGFR2, and vasohibin were determined by real-time reverse-transcriptase polymerase chain reaction (RT-PCR) from the CNV membranes excised from nine AMD and nine PCV patients.

RESULTS

The patients were divided into three groups; four patients were placed in the most active group (Group H), 13 in the less active group (Group E), and four in the nonactive group (Group S). Immunohistochemistry showed that vasohibin, vWF, and VEGF were expressed in the vascular endothelial cells in the CNV membranes and in the polypoidal vessels. RT-PCR showed that there was a strong correlation between the level of expression of VEGFR2 and vasohibin (P = .0002). Eyes with a lower vasohibin-to-VEGF ratio tended to have larger subretinal hemorrhages or vitreous hemorrhages, whereas eyes with higher vasohibin-to-VEGF ratio had subretinal fibrosislike lesions. Statistical analysis of the vasohibin-to-VEGF ratio among the three groups was significant (P = .0209).

CONCLUSIONS

Vasohibin is expressed in human CNV membranes. Our results indicate that the vasohibin-to-VEGF ratio may be related with the activity of the CNV.

The role of vascular endothelial growth factor and other endogenous interplayers in age-related macular degeneration

Age-related macular degeneration (AMD) is a multifaceted disease characterized by early subclinical changes at the choroidea-retinal pigment epithelium interface. Both the causal and formal pathogenesis of the disease is still puzzling. Similarly, the reason for progression into two distinct late forms which are "geographic atrophy" and "choroidal neovascularization" remains enigmatic. Late changes are usually responsible for the dramatic loss in central function that has a devastating effect on quality of life. In industrialized countries the disease is a major cause for visual disability among persons over 60 years of age. Due to demographic right-shift and increased life expectancy, AMD is not only a medical problem but will have a pronounced socio-economic effect. Neovascular AMD with the development of choroidal neovascularization in the macular area accounts for 80% of the severe loss of visual acuity due to AMD. In the last decades, treatment modes were merely based on the destruction or surgical removal of the neovascular complex. In the present, however, the philosophical approach to treat the disease is changing to a pathology modifying manner. Intelligent targeting of the involved relevant factors and pathways should stop disease progression, reduce complications and improve vision. The first step into this new era has been accomplished with the introduction of antiangiogenic agents. The new agents act either directly on vascular endothelial growth factor (VEGF) or indirectly on its functional cascade. VEGF makes a fundamental contribution to neovascular processes but it also acts in physiological pathways. The main purpose of this review is to summarize its physiological role especially within the eye, the role in the development of AMD and to understand and foresee both the benefits and potential side-effects of the anti-VEGF-based therapy.

Anti-angiogenic effects of ribonucleic acid interference targeting vascular endothelial growth factor and hypoxia-inducible factor-1alpha

PURPOSE

To compare the in vitro anti-angiogenic effects of inhibiting vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1-alpha (HIF-1alpha) using ribonucleic acid (RNA) interference (RNAi).

DESIGN

Laboratory investigation.

METHODS

VEGF or HIF-1alpha was antagonized in human retinal pigment epithelial (RPE) cells using RNAi, and then cells were cultured under hypoxia. Angiogenic proteins secreted into the media were measured using enzyme-linked immunosorbent assay. Media from hypoxic RPE cells was used to grow human umbilical vein endothelial cells (HUVECs). Capillary tube formation by HUVECs was quantified and compared to assess the effectiveness of angiogenesis.

RESULTS

RNAi targeting VEGF caused a significant decrease in VEGF in addition to several other clinically important angiogenic factors, including angiogenin, interleukin-6 (IL-6), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and tumor growth factor beta(1) (TGF-beta(1)). Although HIF-1alpha RNAi reduced the production of VEGF, angiogenin, and TGF-beta(1), we observed an increase in the levels of several other angiogenic factors like IL-6, IL-8, and MCP-1. RNAi of VEGF and HIF-1alpha was effective in inhibiting angiogenesis, although the effect was more pronounced for VEGF RNAi.

CONCLUSIONS

RNAi of VEGF and HIF-1alpha may have therapeutic potential in ischemic retinal diseases like diabetic retinopathy. Targeting VEGF seems to have the advantage of decreasing the production of several clinically important angiogenic factors, thereby effectively inhibiting angiogenesis. Antagonism of HIF-1alpha may lead to the overactivation of alternate transcription factors and their respective gene products, leading to less effective inhibition of angiogenesis.

VEGF modulation of retinal pigment epithelium resistance

Fluid accumulation into the subretinal space and the development of macular edema is a common condition in age-related macular degeneration, diabetic retinopathy, and following ocular surgery, or injury. Vascular endothelial growth factor (VEGF) and other cytokines have been implicated in the disruption of retinal pigment epithelium (RPE) barrier function and a reduction in the regulated removal of subretinal fluid; however, the cellular and molecular events linking these agents to the disruption of barrier function have not been established. In the current study, cultures of ARPE-19 and primary porcine retinal pigment epithelium (RPE) cells were utilized to investigate the effects of the VEGF-induced modifications to the barrier properties of the RPE. The barrier function was determined by transepithelial resistance (TER) measurements and morphology of the RPE monolayers. In both ARPE-19 and primary porcine RPE cells the administration of VEGF produced a significant drop in TER, and this response was only observed following apical administration. Maximum reduction in TER was reached 5h post VEGF administration. These responses were concentration-dependent with an EC(50) of 502pg/mL in ARPE-19 cells and 251pg/mL in primary porcine cells. In both ARPE-19 and primary RPE cells, the response to VEGF was blocked by pretreatment with the relatively selective VEGF-R2 antagonists, SU5416 or ZM323881, or the protein tyrosine kinase inhibitor, genistein. Administration of the relatively selective VEGF-R2 agonist, VEGF-E, also reduced TER in a concentration-dependent manner (EC(50) of 474pg/mL), while VEGF-R1 agonist, placental growth factor (PlGF), did not significantly alter the TER. Immunolocalization studies demonstrated that confluent monolayers exhibited continuous cell-to-cell ZO-1 protein contacts and apical localization of the VEGF-R2 receptors. These data provide evidence that the VEGF-induced breakdown of RPE barrier function is mediated by the activation of apically-oriented VEGF-R2 receptors. Thus, VEGF-mediated increases in RPE permeability are initiated by a rise in intraocular levels of VEGF.

Geldanamycin, a HSP90 inhibitor, attenuates the hypoxia-induced vascular endothelial growth factor expression in retinal pigment epithelium cells in vitro

Hypoxia is the most common factor contributing to the pathogenesis of choroidal neovascularization, which is the major cause for blindness and occurs in proliferative diabetic retinopathy and age-related macular degeneration. The purpose of this study is to investigate the role of retinal pigment epithelial (RPE) cells in the regulation of subretinal neovascularization under hypoxia and the possible function of a heat shock protein 90 (HSP90) inhibitor, geldanamycin (GA), in the regulation of VEGF expression. An in vitro hypoxic experimental model was used to mimic the ischemic microenvironment of RPE cells. The cell growth was measured by proliferation assay and the morphological observation was documented by microscope. The gene expression of VEGF, hsp70, hsp90alpha and hsp90beta were measured using semi-quantitative RT-PCR. The VEGF release from RPE cells were detected by ELISA. No alteration in growth rate and cell morphology under 1% O(2) condition for 24h was noticed. The proangiogenic growth factor VEGF, but not bFGF, released from hypoxia-treated cells were significantly higher than those of normoxic controls. A similar tendency of VEGF(165) isoform gene expression, detected by RT-PCR, was noticed in hypoxia-treated cells. Heat shock pretreatment elevated hsp70 and VEGF(165) gene expression and augmented the hypoxia-induced VEGF gene expression and protein release. Pretreatment with GA can significantly suppress the hypoxia-induced VEGF gene expression in and peptide release from RPE cells. These in vitro findings suggest that HSP90 inhibitors could be considered as novel anti-angiogenesis agents for diseases with intraocular neovascularization.

Flt-1, but not Flk-1 mediates hyperpermeability through activation of the PI3-K/Akt pathway

Vascular endothelial growth factor (VEGF), a potent mediator of endothelial proliferation and migration, has an important role also in brain edema formation during hypoxia and ischemia. VEGF binds to the tyrosine kinase receptors Flt-1 and Flk-1. Yet, their relative importance for hypoxia-induced hyperpermeability is not well understood. We used an in vitro blood-brain barrier (BBB) model consisting of porcine brain microvascular endothelial cells (BMEC) to determine the role of Flt-1 in VEGF-induced endothelial cell (EC) barrier dysfunction. Soluble Flt-1 abolished hypoxia/VEGF-induced hyperpermeability. Furthermore, selective antisense oligonucleotides to Flt-1, but not to Flk-1, inhibited hypoxia-induced permeability changes. Consistent with these data, addition of the receptor-specific homolog placenta-derived growth factor, which binds Flt-1 but not Flk-1, increased endothelial permeability to the same extent as VEGF, whereas adding VEGF-E, a viral VEGF molecule from the orf virus family activating Flk-1 and neuropilin-1, but not Flt-1, did not show any effect. Using the carcinoma submandibular gland cell line (CSG), only expressing Flt-1, it was demonstrated that activation of Flt-1 is sufficient to induce hyperpermeability by hypoxia and VEGF. Hyperpermeability, induced by hypoxia/VEGF, depends on activation of phosphatidylinositol 3-kinase/Akt (PI3-K/Akt), nitric oxide synthase (NOS) and protein kinase G (PKG). The activation of the PI3-K/Akt pathway by hypoxia was confirmed using an in vivo mice hypoxia model. These results demonstrate that hypoxia/VEGF-induced hyperpermeability can be mediated by activation of Flt-1 independently on the presence of Flk-1 and indicate a central role for activation of the PI3-K/Akt pathway, followed by induction of NOS and PKG activity.

Obestatin-mediated proliferation of human retinal pigment epithelial cells: regulatory mechanisms

In this work, we have evaluated the effect of the new discovered peptide obestatin on cell proliferation in primary cultures of human retinal epithelial cells (hRPE cells). The results showed that this peptide induced, in a dose-dependent manner, cell proliferation by MEK/ERK 1/2 phosphorylation. A sequential analysis of the obestatin transmembrane signaling pathway showed that the ERK 1/2 activity is partially blocked after preincubation of the cells with pertussis toxin (PTX), as well as by wortmannin (an inhibitor of PI3K), claphostin C (an inhibitor of PKC), and PP2 (which inhibits the non receptor tyrosine kinase Src). Upon administration of obestatin, the intracellular levels of phospho-PKCepsilon-, theta-, and micro-isoenzymes rise with different time courses, from which PKCepsilon might be responsible for ERK 1/2 response. Based on the experimental data, a signaling pathway involving the consecutive activation of Gi, PI3K, novel PKC (probably PKCepsilon), and Src for ERK 1/2 activation is proposed. These results incorporate a new mitogenic factor to the group of factors that regulate proliferation of hRPE cells.

Placental growth factor-1 and epithelial haemato-retinal barrier breakdown: potential implication in the pathogenesis of diabetic retinopathy

AIMS/HYPOTHESIS

Disruption of the retinal pigment epithelial (RPE) barrier contributes to sub-retinal fluid and retinal oedema as observed in diabetic retinopathy. High placental growth factor (PLGF) vitreous levels have been found in diabetic patients. This work aimed to elucidate the influence of PLGF-1 on a human RPE cell line (ARPE-19) barrier in vitro and on normal rat eyes in vivo.

METHODS

ARPE-19 permeability was measured using transepithelial resistance and inulin flux under stimulation of PLGF-1, vascular endothelial growth factor (VEGF)-E and VEGF 165. Using RT-PCR, we evaluated the effect of hypoxic conditions or insulin on transepithelial resistance and on PLGF-1 and VEGF receptors. The involvement of mitogen-activated protein kinase (MEK, also known as MAPK)/extracellular signal-regulated kinase (ERK, also known as EPHB2) signalling pathways under PLGF-1 stimulation was evaluated by western blot analysis and specific inhibitors. The effect of PLGF-1 on the external haemato-retinal barrier was evaluated after intravitreous injection of PLGF-1 in the rat eye; evaluation was by semi-thin analysis and zonula occludens-1 immunolocalisation on flat-mounted RPE.

RESULTS

In vitro, PLGF-1 induced a reversible decrease of transepithelial resistance and enhanced tritiated inulin flux. These effects were specifically abolished by an antisense oligonucleotide directed at VEGF receptor 1. Exposure of ARPE-19 cells to hypoxic conditions or to insulin induced an upregulation of PLGF-1 expression along with increased transcellular permeability. The PLGF-1-induced RPE cell permeability involved the MEK signalling pathway. Injection of PLGF-1 in the rat eye vitreous induced an opening of the RPE tight junctions with subsequent sub-retinal fluid accumulation, retinal oedema and cytoplasm translocation of junction proteins.

CONCLUSIONS/INTERPRETATION

Our results indicate that PLGF-1 may be a potential regulation target for the control of diabetic retinal and macular oedema.

Promising new treatments for neovascular age-related macular degeneration

Angiogenesis, the growth of new blood vessels from existing blood vessels, is responsible for vision loss in a variety of ophthalmic diseases. In neovascular age-related macular degeneration (AMD), the leading cause for legal blindness in many industrialised countries, abnormal blood vessels grow in the macula and cause blindness. There are a number of factors important in the angiogenic cascade but VEGF-A has been implicated in recent years as the major factor responsible for neovascular and exudative diseases of the eye. Numerous antiangiogenic drugs are in development but anti-VEGF drugs have shown great promise in treating neovascular AMD and other ocular diseases, and many of these drugs have been adopted from oncology where antiangiogenic therapy is gaining wide acceptance. For the first time in neovascular AMD, anti-VEGF drugs have brought the hope of vision improvement to a significant proportion of patients. This review provides an overview on angiogenic mechanisms, potential antiangiogenic treatment strategies and different antiangiogenic drugs with special focus on neovascular AMD.

Cervical sympathectomy regulates expression of key angiogenic factors in the rat choroid

Age-related macular degeneration is the leading cause of blindness in people over the age of 55. In addition to an increased risk of vision loss due to macular degeneration, aging results in a substantial loss of sympathetic nerve activity. We have previously shown that loss of sympathetic nerve activity to the eye causes significant remodeling of the choroidal vasculature. The hypothesis of the present study was that the choroidal remodeling noted after sympathectomy was due to alterations in key angiogenic growth factors. To test this hypothesis, female Sprague-Dawley rats underwent superior cervical ganglionectomy, which eliminates all sympathetic innervation to the eye. Six weeks after surgery, eyes were removed, and the choroidal tissue was processed for real-time PCR to measure gene expression and western blot analysis to assess protein expression. Gene and protein expression were significantly increased for vascular endothelial growth factor (VEGF) and pigment epithelial-derived growth factor (PEDF) in the sympathectomized eye, as compared to the contralateral eye (P < 0.05). Protein expression was increased 4-fold for angiopoietin1, with no change in steady-state gene expression. For both p53 and placental growth factor, steady-state mRNA levels were significantly decreased, while protein expression was significantly increased. Protein expression for Flt-1 was decreased significantly, with reduced gene expression. These results suggest that the vascular remodeling noted in the choroidal blood vessels after sympathectomy is a complex process involving numerous growth factor families. Therefore, modulation of sympathetic nerve activity may be a suitable mechanism to prevent the vascular growth associated with macular degeneration.

Angiogenesis in interstitial lung diseases: a pathogenetic hallmark or a bystander?

The past ten years parallels have been drawn between the biology of cancer and pulmonary fibrosis. The unremitting recruitment and maintenance of the altered fibroblast phenotype with generation and proliferation of immortal myofibroblasts is reminiscent with the transformation of cancer cells. A hallmark of tumorigenesis is the production of new blood vessels to facilitate tumor growth and mediate organ-specific metastases. On the other hand several chronic fibroproliferative disorders including fibrotic lung diseases are associated with aberrant angiogenesis. Angiogenesis, the process of new blood vessel formation is under strict regulation determined by a dual, yet opposing balance of angiogenic and angiostatic factors that promote or inhibit neovascularization, respectively. While numerous studies have examined so far the interplay between aberrant vascular and matrix remodeling the relative role of angiogenesis in the initiation and/or progression of the fibrotic cascade still remains elusive and controversial. The current article reviews data concerning the pathogenetic role of angiogenesis in the most prevalent and studied members of ILD disease-group such as IIPs and sarcoidosis, presents some of the future perspectives and formulates questions for potential further research.