Pigment epithelium-derived factor (PEDF) prevents diabetes- or advanced glycation end products (AGE)-elicited retinal leukostasis

Encapsulated cell technology: Delivering cytokines to treat posterior ocular diseases

Encapsulated cell technology (ECT) is a targeted delivery method that uses the genetically engineered cells in semipermeable polymer capsules to deliver cytokines. Thus far, ECT has been extensively utilized in pharmacologic research, and shows enormous potentials in the treatment of posterior segment diseases. Due to the biological barriers within the eyeball, it is difficult to attain effective therapeutic concentration in the posterior segment through topical administration of drug molecules. Encouragingly, therapeutic cytokines provided by ECT can cross these biological barriers and achieve sustained release at the desired location. The encapsulation system uses permeable materials that allow growth factors and cytokines to diffuse efficiently into retinal tissue. Moreover, the ECT based treatment can be terminated timely when we need to retrieve the implant, which makes the therapy reversible and provides a safer alternative for intraocular gene therapy. Meanwhile, we also place special emphasis on optimizing encapsulation materials and enhancing preservation techniques to achieve the stable release of growth factors and cytokines in the eyeball. This technology holds great promise for the treatment of patients with dry AMD, RP, glaucoma and MacTel. These findings would enrich our understandings of ECT and promote its future applications in treatment of degenerative retinopathy. This review comprises articles evaluating the exactness of artificial intelligence-based formulas published from 2000 to March 2024. The papers were identified by a literature search of various databases (PubMed/MEDLINE, Google Scholar, Cochrane Library and Web of Science).

12-HETE activates Müller glial cells: The potential role of GPR31 and miR-29

Diabetic retinopathy (DR) is a neurovascular complication of diabetes, driven by an intricate network of cellular and molecular mechanisms. This study sought to explore the mechanisms by investigating the role of 12-hydroxyeicosatetraenoic acid (12-HETE), its receptor GPR31, and microRNA (miR-29) in the context of DR, specifically focusing on their impact on Müller glial cells. We found that 12-HETE activates Müller cells (MCs), elevates glutamate production, and induces inflammatory and oxidative responses, all of which are instrumental in DR progression. The expression of GPR31, the receptor for 12-HETE, was prominently found in the retina, especially in MCs and retinal ganglion cells, and was upregulated in diabetes. Interestingly, miR29 showed potential as a protective agent, mitigating the harmful effects of 12-HETE by attenuating inflammation and oxidative stress, and restoring the expression of pigment epithelium-derived factor (PEDF). Our results underline the central role of 12-HETE in DR progression through activation of a neurovascular toxic pathway in MCs and illuminate the protective capabilities of miR-29, highlighting both as promising therapeutic targets for the management of DR.

Glycation-induced age-related illnesses, antiglycation and drug delivery strategies

OBJECTIVES

Ageing is a major cause of multiple age-related diseases. Several mechanisms have been reported to contribute to these abnormalities including glycation, oxidative stress, the polyol pathway and osmotic stress. Glycation, unlike glycosylation, is an irregular biochemical reaction to the formation of active advanced glycation end-products (AGEs), which are considered to be one of the causes of these chronic diseases. This study provides a recent and comprehensive review on the possible causes, mechanisms, types, analytical techniques, diseases and treatments of the toxic glycation end products.

KEY FINDINGS

Several mechanisms have been found to play a role in generating hyperglycaemia-induced oxidative stress including an increase in the levels of reactive oxygen species (ROS), increase in the levels of AGEs, binding of AGEs and their receptors (RAGE) and the polyol pathway and thus have been investigated as promising novel targets.

SUMMARY

This review focuses on the key mechanisms attributed to cumulative increases of glycation and pathological RAGE expression as a significant cause of multiple age-related diseases, and reporting on different aspects of antiglycation therapy as a novel approach to managing/treating age-related diseases. Additionally, historical, current and possible future antiglycation approaches will be presented focussing on novel drug delivery methods.

Advanced Glycation End Products Are Associated with Diabetes Status and Physical Functions in Patients with Cardiovascular Disease

Advanced glycated end products (AGEs) accumulate systemically and cause diabetes complications. However, whether noninvasive measurable AGEs are associated with diabetes status and physical functions remains unclear. One hundred and ten patients with cardiovascular disease (CVD) who underwent outpatient cardiac rehabilitation were included. AGEs scores, using AGEs sensors, were evaluated concomitantly with a physical evaluation, including testing the isometric knee extension strength (IKES) and 6 min walking distance (6MWD). Thirty-three (30%) patients had a history of diabetes mellitus (DM). The AGEs score was not different in the presence of DM history (0.52 ± 0.09 vs. 0.51 ± 0.09, p = 0.768) and was not correlated with blood glucose (r = 0.001, p = 0.995). The AGEs score was positively correlated with hemoglobin A1c (HbA1c, r = 0.288, p = 0.004) and negatively correlated with physical functions (IKES, r = −0.243, p = 0.011; 6MWD, r = −0.298, p = 0.002). The multivariate analysis demonstrated that 6MWD was independently associated with a high AGEs score (>0.52). The AGEs score was associated with HbA1c, IKES, and 6MWD in patients with CVD. The AGEs score might be a useful indicator for evaluating not only glycemic control but also physical functions.

Patrolling Monocytes Are Recruited and Activated by Diabetes to Protect Retinal Microvessels

In diabetes there is a long latency between the onset of hyperglycemia and the appearance of structural microangiopathy. Because Ly6C^low patrolling monocytes (PMo) behave as housekeepers of the vasculature, we tested whether PMo protect microvessels against diabetes. We found that in wild-type mice, diabetes reduced PMo in the general circulation but increased by fourfold the absolute number of PMo adherent to retinal vessels (leukostasis). Conversely, in diabetic NR4A1^-/- mice, a model of absence of PMo, there was no increase in leukostasis, and at 6 months of diabetes, the number of retinal acellular capillaries almost doubled compared with diabetic wild-type mice. Circulating PMo showed gene expression changes indicative of enhanced migratory, vasculoprotective, and housekeeping activities, as well as profound suppression of genes related to inflammation and apoptosis. Promigratory CXCR4 was no longer upregulated at longer duration when retinal acellular capillaries begin to increase. Thus, after a short diabetes duration, PMo are the cells preferentially recruited to the retinal vessels and protect vessels from diabetic damage. These observations support the need for reinterpretation of the functional meaning of leukostasis in diabetes and document within the natural history of diabetic retinopathy processes of protection and repair that can provide novel paradigms for prevention.

Therapeutic Potential of Pigment Epithelium-derived Factor in Cancer

Pigment epithelium-derived factor (PEDF) is one of the serine protease inhibitors with multifunctional properties, which is produced by various types of organs and tissues. There is an accumulating body of evidence that PEDF plays an important role in the maintenance of tissue homeostasis. Indeed, PEDF not only works as an endogenous inhibitor of angiogenesis, but also suppresses oxidative stress, inflammatory and thrombotic reactions in cell culture systems, animal models, and humans. Furthermore, we, along with others, have found that PEDF inhibits proliferation of, and induces apoptotic cell death in, numerous kinds of tumors. In addition, circulating as well as tumor expression levels of PEDF have been inversely associated with tumor growth and metastasis. These observations suggest that supplementation of PEDF proteins and/or enhancement of endogenous PEDF expression could be a novel therapeutic strategy for the treatment of cancer. Therefore, in this paper, we review the effects of PEDF on diverse types of cancer, and discuss its therapeutic perspectives.

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.

PEDF increases GLUT4-mediated glucose uptake in rat ischemic myocardium via PI3K/AKT pathway in a PEDFR-dependent manner

BACKGROUND

Targeted increase in glucose uptake of ischemic myocardium is a potential therapeutic strategy for myocardial ischemia. PEDF presents a profound moderating effect on glucose metabolism of cells, but its role is still controversial. Here, we try to demonstrate the direct effect of PEDF on glucose uptake in ischemic myocyte and to elucidate its underlying mechanism.

METHODS AND RESULTS

Lentivirus vectors carrying PEDF gene were delivered into the myocardium to locally overexpress PEDF in a myocardial ischemia/reperfusion rat model. PET imaging showed that PEDF local overexpression increased [¹⁸F]-FDG uptake of ischemic myocardium. In vitro, PEDF directly increased the glucose uptake in hypoxic cardiomyocytes. The expression of glucose transporter 4 (GLUT4) on plasma membrane of hypoxic cardiomyocytes was significantly upregulated by PEDF, but its total amount was not changed. The increased glucose uptake and cardioprotective effects induced by PEDF were blocked by the GLUT4 inhibitor indinavir. PEDF-mediated GLUT4 translocation and glucose uptake increase in hypoxic cardiomyocytes were prevented by phosphatidyl-inositol-3 kinase (PI3K) inhibitor or AKT inhibitor. The PEDF-mediated glucose uptake was also diminished when PEDF receptor (PEDFR) was downregulated or potent phospholipase A2 enzymatic activity was inhibited.

CONCLUSIONS

PEDF can increase glucose uptake in ischemic myocardium through a PEDFR-dependent mechanism, involving PI3K/AKT signaling and GLUT4 translocation.

Reactive Oxygen Species-Mediated Damage of Retinal Neurons: Drug Development Targets for Therapies of Chronic Neurodegeneration of the Retina

The significance of oxidative stress in the development of chronic neurodegenerative diseases of the retina has become increasingly apparent in recent years. Reactive oxygen species (ROS) are free radicals produced at low levels as a result of normal cellular metabolism that are ultimately metabolized and detoxified by endogenous and exogenous mechanisms. In the presence of oxidative cellular stress, ROS are produced in excess, resulting in cellular injury and death and ultimately leading to tissue and organ dysfunction. Recent studies have investigated the role of excess ROS in the pathogenesis and development of chronic neurodegenerative diseases of the retina including glaucoma, diabetic retinopathy, and age-related macular degeneration. Findings from these studies are promising insofar as they provide clear rationales for innovative treatment and prevention strategies of these prevalent and disabling diseases where currently therapeutic options are limited. Here, we briefly outline recent developments that have contributed to our understanding of the role of ROS in the pathogenesis of chronic neurodegenerative diseases of the retina. We then examine and analyze the peer-reviewed evidence in support of ROS as targets for therapy development in the area of chronic neurodegeneration of the retina.

PEDF expression affects retinal endothelial cell proangiogenic properties through alterations in cell adhesive mechanisms

Pigment epithelium-derived factor (PEDF) is an endogenous inhibitor of angiogenesis. Although various ocular cell types including retinal endothelial cells (EC) produce PEDF, we know very little about cell autonomous effects of PEDF in these cell types. Here we determined how PEDF expression affects retinal EC proangiogenic properties. Retinal EC were prepared from wild-type (PEDF+/+) and PEDF-deficient (PEDF-/-) mice. The identity of EC was confirmed by staining for specific markers including vascular endothelial cadherin, CD31, and B4-lectin. Retinal EC also expressed VEGF receptor 1 and endoglin, as well as ICAM-1, ICAM-2, and VCAM-1. PEDF-/- retinal EC were more proliferative, less apoptotic when challenged with H2O2, less migratory, and less adherent compared with PEDF+/+ EC. These changes could be associated, at least in part, with increased levels of tenascin-C, fibronectin, thrombospondin-1 and collagen IV, and lower amounts of osteopontin. PEDF-/- EC also exhibited alterations in expression of a number of integrins including α2, αv, β1, β8, and αvβ3, and cell-cell adhesion molecules including CD31, zonula occluden-1, and occludin. These observations correlated with attenuation of capillary morphogenesis and increased levels of oxidative stress in PEDF-/- EC. PEDF-/- EC also produced lower levels of VEGF compared with PEDF+/+ cells. Thus, PEDF deficiency has a significant impact on retinal EC adhesion and migration, perhaps through altered production of extracellular matrix and junctional proteins in response to increased oxidative stress affecting their proangiogenic activity.

Sulforaphane reduces advanced glycation end products (AGEs)-induced inflammation in endothelial cells and rat aorta

BACKGROUND AND AIMS

Advanced glycation end products (AGEs)-receptor RAGE interaction evokes oxidative stress and inflammatory reactions, thereby being involved in endothelial cell (EC) damage in diabetes. Sulforaphane is generated from glucoraphanin, a naturally occurring isothiocyanate found in widely consumed cruciferous vegetables, by myrosinase. Sulforaphane has been reported to protect against oxidative stress-mediated cell and tissue injury. However, effects of sulforaphane on AGEs-induced vascular damage remain unclear.

METHODS AND RESULTS

In this study, we investigated whether and how sulforaphane could inhibit inflammation in AGEs-exposed human umbilical vein ECs (HUVECs) and AGEs-injected rat aorta. Sulforaphane treatment for 4 or 24 h dose-dependently inhibited the AGEs-induced increase in RAGE, monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecular-1 (VCAM-1) gene expression in HUVECs. AGEs significantly stimulated MCP-1 production by, and THP-1 cell adhesion to, HUVECs, both of which were prevented by 1.6 μM sulforaphane. Sulforaphane significantly suppressed oxidative stress generation and NADPH oxidase activation evoked by AGEs in HUVECs. Furthermore, aortic RAGE, ICAM-1 and VCAM-1 expression in AGEs-injected rats were increased, which were suppressed by simultaneous infusion of sulforaphane.

CONCLUSION

The present study demonstrated for the first time that sulforaphane could inhibit inflammation in AGEs-exposed HUVECs and AGEs-infused rat aorta partly by suppressing RAGE expression through its anti-oxidative properties. Inhibition of the AGEs-RAGE axis by sulforaphane might be a novel therapeutic target for vascular injury in diabetes.

Advanced Glycation End Products: A Molecular Target for Vascular Complications in Diabetes

A nonenzymatic reaction between reducing sugars and amino groups of proteins, lipids and nucleic acids contributes to the aging of macromolecules and subsequently alters their structural integrity and function. This process has been known to progress at an accelerated rate under hyperglycemic and/or oxidative stress conditions. Over a course of days to weeks, early glycation products undergo further reactions such as rearrangements and dehydration to become irreversibly cross-linked, fluorescent and senescent macroprotein derivatives termed advanced glycation end products (AGEs). There is a growing body of evidence indicating that interaction of AGEs with their receptor (RAGE) elicits oxidative stress generation and as a result evokes proliferative, inflammatory, thrombotic and fibrotic reactions in a variety of cells. This evidence supports AGEs' involvement in diabetes- and aging-associated disorders such as diabetic vascular complications, cancer, Alzheimer's disease and osteoporosis. Therefore, inhibition of AGE formation could be a novel molecular target for organ protection in diabetes. This report summarizes the pathophysiological role of AGEs in vascular complications in diabetes and discusses the potential clinical utility of measurement of serum levels of AGEs for evaluating organ damage in diabetes.

DNA Aptamer Raised against Advanced Glycation End Products Prevents Abnormalities in Electroretinograms of Experimental Diabetic Retinopathy

PURPOSE

Abnormalities in electroretinograms (ERG), such as reduced amplitudes and delayed implicit times of a- and b-wave and oscillatory potentials (OPs), are one of the earliest features of diabetic retinopathy prior to obvious vascular changes in diabetic retinas. We have previously shown that serum levels of advanced glycation end products (AGEs) are correlated with a delayed latency of OPs in type 2 diabetic rats. However, the pathological role of AGEs in ERG abnormalities remains unclear. We examined here whether high-affinity DNA aptamer directed against AGEs (AGE-aptamer) prevents ERG abnormalities in experimental type 1 diabetic retinopathy.

METHODS

Streptozotocin-induced diabetic rats or control rats received continuous intraperitoneal infusion of either AGE-aptamer or control aptamer via an osmotic mini pump for 16 weeks. Anthropometric, metabolic, and hemodynamic variables were measured, and an ERG was performed.

RESULTS

Although AGE-aptamer did not affect body weight, fasting and random blood glucose, HbA1c, blood pressure, or lipid parameters, it completely prevented the increase in serum AGE levels as well as the reduction of a- and b-wave and OP amplitudes in diabetic rats.

CONCLUSION

The present study demonstrated for the first time that AGE-aptamer prevents abnormalities in ERG in experimental diabetic retinopathy probably by blocking the harmful effects of AGEs.

Dipeptidyl peptidase-4 deficiency protects against experimental diabetic nephropathy partly by blocking the advanced glycation end products-receptor axis

Advanced glycation end products (AGEs) and their receptor (RAGE) have a role in diabetic nephropathy. We have recently found that linagliptin, an inhibitor of dipeptidyl peptidase-4 (DPP-4), could inhibit renal damage in type 1 diabetic rats by suppressing the AGE-RAGE axis. However, it remains unclear whether DPP-4 deficiency could also have beneficial effects on experimental diabetic nephropathy. To address the issue, we rendered wild-type F344/NSlc and DPP-4-deficient F344/DuCrl/Crlj rats diabetic by injection of streptozotocin, and then investigated whether DPP-4 deficiency could block the activation of AGE-RAGE axis in the diabetic kidneys and resultantly ameliorate renal injury in streptozotocin-induced diabetic rats. Compared with control rats at 9 and 11 weeks old, body weight and heart rates were significantly lower, while fasting blood glucose was higher in wild-type and DPP-4-deficient diabetic rats at the same age. There was no significant difference of body weight, fasting blood glucose and lipid parameters between the two diabetic rat strains. AGEs, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nitrotyrosine levels in the kidney, renal gene expression of RAGE and intercellular adhesion molecule-1, glomerular area, urinary excretion of 8-OHdG and albumin, and the ratio of renal to body weight were increased in wild-type diabetic rats at 9 and/or 11 weeks old compared with age-matched control rats, all of which except for urinary 8-OHdG levels at 11 weeks old were significantly suppressed in DPP-4-deficient diabetic rats. Our present study suggests that DPP-4 deficiency could exert beneficial actions on type 1 diabetic nephropathy partly by blocking the AGE-RAGE axis. DPP-4 might be a novel therapeutic target for preventing diabetic nephropathy.

Novel approaches for treating diabetic retinopathy based on recent pathogenic evidence

Diabetic retinopathy remains as a leading cause of blindness in developed countries. Current treatments target late stages of DR when vision has already been significantly affected. A better understanding of the pathogenesis of DR would permit the development of more efficient preventional/interventional strategies against early stages of DR. In this article a critical review of the state of the art of this issue is provided along with a discussion of problems which have yet to be overcome. Neuroprotection as a new approach for the treatment of the early stages of DR has been particularly emphasized. The development and progression of DR is not homogeneous and, apart from blood glucose levels and blood pressure, it depends on genetic factors which remain to be elucidated. In addition, the role of the pathogenic pathways is not the same in all patients. All these factors should be taken into account in the near future when an individualized oriented treatment for DR could become feasible. The new techniques in retinal imaging acquisition, the identification of useful circulating biomarkers and the individualized analysis of biological samples could facilitate the development of early and personalized therapy in the setting of DR. Finally, it should be noted that only a coordinated action among ophthalmologists, diabetologists, basic researchers, experts in pharmaco-economics and health care providers addressed to the design of rational strategies targeting prevention and the early stages of DR will be effective in reducing the burden and improving the clinical outcome of this devastating complication of diabetes.

Serum levels of pigment epithelium-derived factor (PEDF) are inversely associated with circulating levels of dipeptidyl peptidase-4 (DPP-4) in humans

BACKGROUND

We have previously found that advanced glycation end products (AGEs) stimulate the proteolytic cleavage of dipeptidyl peptidase-4 (DPP-4) from plasma membranes, and circulating AGE levels are independently correlated with serum DPP-4 values. Since pigment epithelium-derived factor (PEDF), one of the adipocytokines, inhibits the AGEs-induced insulin resistance and vascular damage, it is conceivable that besides AGEs, PEDF might also regulate soluble DPP-4 levels. In this study, we addressed the issue.

STUDY DESIGN AND METHODS

The study involved 188 subjects (123 males and 65 females; mean age of 61.1±9.2) who visited our hospital for a risk-screening test or treatment for cardiovascular disease. They underwent complete history and physical examinations, and determination of blood chemistry and anthropometric variables, including visceral and subcutaneous fat areas. Serum levels of DPP-4 and PEDF levels were examined by enzyme-linked immunosorbent assay.

RESULTS

Median (interquartile range) serum levels of DPP-4 and PEDF were 466.6 (400.2-545.1) ng/mL and 14.0 (10.6-17.0) μg/mL, respectively. Multiple stepwise regression analysis revealed that female (p<0.001), aspartate aminotransferase (p<0.001), glycated hemoglobin (p<0.001) and PEDF (inversely, p=0.020) were independently associated with DPP-4 levels (R(2)=0.267).

CONCLUSION

We found here for the first time that serum PEDF levels were one of the independent correlates of circulating DPP-4 levels in humans. Since DPP-4 could impair insulin action and evoke vascular damage, our present study suggests that insulin-sensitizing and atheroprotective properties of PEDF might be ascribed partly to its inhibitory actions on DPP-4.

Pigment epithelium-derived factor inhibits retinal microvascular dysfunction induced by 12/15-lipoxygenase-derived eicosanoids

We recently demonstrated that 12/15-lipoxygenase (LOX) derived metabolites, hydroxyeicosatetraenoic acids (HETEs), contribute to diabetic retinopathy (DR) via NADPH oxidase (NOX) and disruption of the balance in retinal levels of the vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF). Here, we test whether PEDF ameliorates retinal vascular injury induced by HETEs and the underlying mechanisms. Furthermore, we pursue the causal relationship between LOX-NOX system and regulation of PEDF expression during DR. For these purposes, we used an experimental eye model in which normal mice were injected intravitreally with 12-HETE with/without PEDF. Thereafter, fluorescein angiography (FA) was used to evaluate the vascular leakage, followed by optical coherence tomography (OCT) to assess the presence of angiogenesis. FA and OCT reported an increased vascular leakage and pre-retinal neovascularization, respectively, in response to 12-HETE that were not observed in the PEDF-treated group. Moreover, PEDF significantly attenuated the increased levels of vascular cell and intercellular adhesion molecules, VCAM-1 and ICAM-1, elicited by 12-HETE injection. Accordingly, the direct relationship between HETEs and PEDF has been explored through in-vitro studies using Müller cells (rMCs) and human retinal endothelial cells (HRECs). The results showed that 12- and 15-HETEs triggered the secretion of TNF-α and IL-6, as well as activation of NFκB in rMCs and significantly increased permeability and reduced zonula occludens protein-1 (ZO-1) immunoreactivity in HRECs. All these effects were prevented in PEDF-treated cells. Furthermore, interest in PEDF regulation during DR has been expanded to include NOX system. Retinal PEDF was significantly restored in diabetic mice treated with NOX inhibitor, apocynin, or lacking NOX2 up to 80% of the control level. Collectively, our findings suggest that interfering with LOX-NOX signaling opens up a new direction for treating DR by restoring endogenous PEDF that carries out multilevel vascular protective functions.

Increased serum pigment epithelium-derived factor in women with gestational diabetes is associated with type 2 diabetes

Background. Pigment epithelium-derived factor (PEDF) is demonstrated to be elevated in diabetes patients. However, no reports have emerged in pregnant women with gestational diabetes mellitus (GDM). This study was undertaken to investigate serum PEDF levels in GDM women and to evaluate PEDF as a biomarker to predict diabetes postpartum. Methods. Serum PEDF concentration and clinical characteristics were detected in the pregnant women with GDM (n = 120) and without GDM (control group, n = 120). Results. PEDF levels were elevated in subjects with GDM versus controls. Univariate correlations showed that serum PEDF levels were positively correlated with fasting glucose and fasting insulin levels, respectively, and negatively correlated with adiponectin. Receiver operating characteristic (ROC) analysis demonstrated that the AUC of serum PEDF for diabetes mellitus in women postpartum was 0.893. Conclusion. Serum PEDF was elevated in pregnant women with GDM, which is probably an early detection marker for predicting development of GDM to diabetes mellitus.

Mechanisms of PEDF-mediated protection against reactive oxygen species damage in diabetic retinopathy and neuropathy

Pigment epithelium-derived factor (PEDF) is a pluripotent glycoprotein belonging to the serpin family. PEDF can stimulate several physiological processes such as angiogenesis, cell proliferation, and survival. Oxidative stress plays an important role in the occurrence of diabetic retinopathy (DR), which is the major cause of blindness in young diabetic adults. PEDF plays a protective role in DR and there is accumulating evidence of the neuroprotective effect of PEDF. In this paper, we review the role of PEDF and the mechanisms involved in its antioxidative, anti-inflammatory, and neuroprotective properties.

Molecular mechanisms of diabetic retinopathy, general preventive strategies, and novel therapeutic targets

The growing number of people with diabetes worldwide suggests that diabetic retinopathy (DR) and diabetic macular edema (DME) will continue to be sight threatening factors. The pathogenesis of diabetic retinopathy is a widespread cause of visual impairment in the world and a range of hyperglycemia-linked pathways have been implicated in the initiation and progression of this condition. Despite understanding the polyol pathway flux, activation of protein kinase C (KPC) isoforms, increased hexosamine pathway flux, and increased advanced glycation end-product (AGE) formation, pathogenic mechanisms underlying diabetes induced vision loss are not fully understood. The purpose of this paper is to review molecular mechanisms that regulate cell survival and apoptosis of retinal cells and discuss new and exciting therapeutic targets with comparison to the old and inefficient preventive strategies. This review highlights the recent advancements in understanding hyperglycemia-induced biochemical and molecular alterations, systemic metabolic factors, and aberrant activation of signaling cascades that ultimately lead to activation of a number of transcription factors causing functional and structural damage to retinal cells. It also reviews the established interventions and emerging molecular targets to avert diabetic retinopathy and its associated risk factors.

Neuropeptides, trophic factors, and other substances providing morphofunctional and metabolic protection in experimental models of diabetic retinopathy

Vision is the most important sensory modality for many species, including humans. Damage to the retina results in vision loss or even blindness. One of the most serious complications of diabetes, a disease that has seen a worldwide increase in prevalence, is diabetic retinopathy. This condition stems from consequences of pathological metabolism and develops in 75% of patients with type 1 and 50% with type 2 diabetes. The development of novel protective drugs is essential. In this review we provide a description of the disease and conclude that type 1 diabetes and type 2 diabetes lead to the same retinopathy. We evaluate existing experimental models and recent developments in finding effective compounds against this disorder. In our opinion, the best models are the long-term streptozotocin-induced diabetes and Otsuka Long-Evans Tokushima Fatty and spontaneously diabetic Torii rats, while the most promising substances are topically administered somatostatin and pigment epithelium-derived factor analogs, antivasculogenic substances, and systemic antioxidants. Future drug development should focus on these.

Potential therapeutic effects of pigment epithelium-derived factor for treatment of diabetic retinopathy

Diabetic retinopathy (DR), a major micro-vascular complication of diabetes, has emerged as a leading cause of visual impairment and blindness among working adults in the worldwide. The pathobiology of DR involves multiple molecular pathways and is characterized chronic neurovascular degeneration. Current approaches to prevent or to treat DR are still far from satisfactory. Therefore, it is important to develop new therapeutic strategies for the prevention and treatment to DR. Pigment epithelium-derived factor (PEDF), a 50-kDa secreted glycoprotein, has been described as a multi-functional protein. Some emerging evidences indicate that PEDF are able to target multiple pathways exerting neurotropic, neuroprotective, anti-angiogenic, antivasopermeability, anti-inflammation, anti-thrombogenic and anti-oxidative effects in DR. In this review, we addressed the functions of PEDF in different pathways, which could lead to potential therapeutics on the treatment to DR.

Beneficial Effects of Vildagliptin on Retinal Injury in Obese Type 2 Diabetic Rats

<b><i>Background/Aims:</i></b> Vildagliptin is an oral inhibitor of dipeptidyl peptidase-4, an enzyme mainly responsible for inactivating incretins, and one of the widely used drugs for the treatment of type 2 diabetes. However, effects of vildagliptin on retinal injury in diabetes remain unclear. We examined here whether oral administration of vildagliptin inhibited gene expression of inflammatory and thrombogenic parameters in Otsuka Long-Evans Tokushima Fatty rats (OLETF rats), an animal model of obese type 2 diabetes. <b><i>Methods:</i></b> OLETF rats at 22 weeks of age were given vehicle or 3 mg/kg of vildagliptin for another 10 weeks. Gene expression was analyzed in quantitative real-time reverse transcription-polymerase chain reaction. <b><i>Results:</i></b> Vildagliptin significantly inhibited the increase in body weight and decreased average fasting blood glucose in the OLETF rats. Compared with 22-week-old OLETF rats, gene expression levels of vascular endothelial growth factor, intercellular adhesion molecule-1, plasminogen activator inhibitor-1 and pigment epithelium-derived factor were significantly increased in the retinas of OLETF rats at 32 weeks of age, all of which were inhibited by treatment with vildagliptin. <b><i>Conclusions:</i></b> The present study demonstrated for the first time that vildagliptin inhibited inflammatory and thrombogenic reactions in the retinas of obese type 2 diabetic rats. Vildagliptin may play a protective role against diabetic retinopathy.

Vitreous inflammatory factors and serous macular detachment in branch retinal vein occlusion

PURPOSE

To investigate whether vascular endothelial growth factor, soluble intercellular adhesion molecule-1 (sICAM-1), and pigment epithelium-derived factor are associated with serous retinal detachment (SRD) secondary to branch retinal vein occlusion.

METHODS

The subjects were 44 branch retinal vein occlusion patients with macular edema and 16 controls. Patients were divided into 2 groups by optical coherence tomography findings, that is, 18 patients with SRD and 26 with cystoid macular edema. The area of capillary nonperfusion was measured with fluorescein angiography and Scion Image software. Vitreous fluid samples obtained during pars plana vitrectomy were examined by enzyme-linked immunosorbent assay.

RESULTS

The incidence of major branch retinal vein occlusion was significantly higher in SRD patients (17/18, 94%) than in cystoid macular edema patients (15/26, 58%, P = 0.007), while the nonperfused retinal area was significantly larger in SRD patients (P = 0.006). Vitreous fluid levels of vascular endothelial growth factor and soluble intercellular adhesion molecule-1 (sICAM-1) showed a significant increase across the 3 groups (control group, cystoid macular edema group, and SRD group) (P trend < 0.001 and P trend < 0.001, respectively), while the pigment epithelium-derived factor level showed a significant decrease across the 3 groups (P trend < 0.001).

CONCLUSION

An excessive increase of vascular permeability secondary to upregulation of vascular endothelial growth factor and soluble intercellular adhesion molecule-1 (sICAM-1) along with downregulation of pigment epithelium-derived factor may contribute to the development of SRD in BRVO patients.

Role of advanced glycation end products (AGEs) and oxidative stress in vascular complications in diabetes

BACKGROUND

A non-enzymatic reaction between reducing sugars and amino groups of proteins, lipids and nucleic acids contributes to the aging of macromolecules, whose process has been known to progress at an accelerated rate under hyperglycemic and/or oxidative stress conditions. Over a course of days to weeks, early glycation products undergo further reactions such as rearrangements and dehydration to become irreversibly cross-linked, fluorescent protein derivatives termed advanced glycation end products (AGEs).

SCOPE OF REVIEW

In this paper, we review the role of AGE-oxidative stress axis and its therapeutic interventions in vascular complications in diabetes.

MAJOR CONCLUSIONS

AGEs elicit oxidative stress generation and subsequently cause inflammatory and thrombogenic reactions in various types of cells via interaction with a receptor for AGEs (RAGE), thereby being involved in vascular complications in diabetes. In addition, mitochondrial superoxide generation has been shown to play an important role in the formation and accumulation of AGEs under diabetic conditions. Further, we have recently found that a pathophysiological crosstalk between AGE-RAGE axis and renin-angiotensin system (RAS) could contribute to the progression of vascular damage in diabetes.

GENERAL SIGNIFICANCE

These observations suggest that inhibition of AGE-RAGE-oxidative stress axis or blockade of its interaction with RAS is a novel therapeutic strategy for preventing vascular complications in diabetes.

Visual prognosis and vitreous molecules after vitrectomy for macular edema with branch retinal vein occlusion

This study investigated whether vascular endothelial growth factor (VEGF), soluble intercellular adhesion molecule-1 (sICAM-1), and pigment epithelium-derived factor (PEDF) influence the visual prognosis of patients with macular edema and branch retinal vein occlusion (BRVO). In 47 consecutive patients (47 eyes) undergoing vitrectomy, retinal thickness was examined by optical coherence tomography. Best-corrected visual acuity and the vitreous fluid levels of VEGF, sICAM-1, and PEDF were also determined. Patients were followed for at least 6 months after surgery. Vitreous fluid levels of VEGF and sICAM-1 were significantly lower in the patients with more marked improvement of visual acuity after vitrectomy, while PEDF was significantly higher. VEGF and sICAM-1 levels were significantly higher in patients with greater postoperative improvement of macular edema, while PEDF was significantly lower. In BRVO patients, vitreous fluid levels of VEGF, sICAM-1, and PEDF may influence both the response of macular edema to vitrectomy and the visual prognosis.

Advanced glycation end products, oxidative stress and diabetic nephropathy

About 246 million people worldwide had diabetes in 2007. The global figure of people with diabetes is projected to increase to 370 million in 2030. As the prevalence of diabetes has risen to epidemic proportions worldwide, diabetic nephropathy has become one of the most challenging health problems. Therapeutic options such as strict blood glucose and blood pressure controls are effective for preventing diabetic nephropathy, but are far from satisfactory, and the number of diabetic patients on end-stage renal disease is still increasing. Therefore, a novel therapeutic strategy that could halt the progression of diabetic nephropathy should be developed. There is accumulating evidence that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate under diabetes, play a role in diabetic nephropathy via oxidative stress generation. In this paper, we review the pathophysiological role of AGEs and their receptor (RAGE)-oxidative stress system in diabetic nephropathy.

Involvement of TAGE-RAGE System in the Pathogenesis of Diabetic Retinopathy

Diabetic complications are a leading cause of acquired blindness, end-stage renal failure, and accelerated atherosclerosis, which are associated with the disabilities and high mortality rates seen in diabetic patients. Continuous hyperglycemia is involved in the pathogenesis of diabetic micro- and macrovascular complications via various metabolic pathways, and numerous hyperglycemia-induced metabolic and hemodynamic conditions exist, including increased generation of various types of advanced glycation end-products (AGEs). Recently, we demonstrated that glyceraldehyde-derived AGEs, the predominant structure of toxic AGEs (TAGE), play an important role in the pathogenesis of angiopathy in diabetic patients. Moreover, recent evidence suggests that the interaction of TAGE with the receptor for AGEs (RAGE) elicits oxidative stress generation in numerous types of cells, all of which may contribute to the pathological changes observed in diabetic complications. In this paper, we discuss the pathophysiological role of the TAGE-RAGE system in the development and progression of diabetic retinopathy.

Blocking the Wnt pathway, a unifying mechanism for an angiogenic inhibitor in the serine proteinase inhibitor family

The Wnt pathway regulates multiple biological and pathological processes including angiogenesis and inflammation. Here we identified a unique inhibitor of the Wnt pathway, SERPINA3K, a serine proteinase inhibitor with anti-inflammatory and angiogenic activities. SERPINA3K blocked the Wnt pathway activation induced by a Wnt ligand and by diabetes. Coprecipitation and ligand binding assay showed that SERPINA3K binds to low-density lipoprotein receptor-like protein 6 (LRP6) with a K(d) of 10 nM, in the range of its physiological concentration in the retina. Under the same conditions, SERPINA3K did not bind to the frizzled (Fz) receptor or low-density lipoprotein receptor. Further, SERPINA3K bound to LRP6 at the extracellular domain and blocked its dimerization with the Fz receptor induced by a Wnt ligand. The antagonizing activity of SERPINA3K to LRP6 was further confirmed by Xenopus axis duplication assay. These results suggest that SERPINA3K is a high-affinity, endogenous antagonist of LRP6. The blockade of Wnt signaling may represent a unifying mechanism for the anti-inflammatory and anti-angiogenic effects of SERPINA3K.

Advanced glycation end products, oxidative stress and diabetic nephropathy

About 246 million people worldwide have diabetes in 2007. The global figure of people with diabetes is projected to increase to 370 million in 2030. As the prevalence of diabetes has risen to epidemic proportions worldwide, diabetic nephropathy has become one of the most challenging health problems. Therapeutic options such as strict blood glucose and blood pressure controls are effective for preventing diabetic nephropathy, but are far from satisfactory, and the number of diabetic patients on end-stage renal disease is still increasing. Therefore, a novel therapeutic strategy that could halt the progression of diabetic nephropathy should be developed. There is accumulating evidence that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate under diabetes, play a role in diabetic nephropathy via oxidative stress generation. In this paper, we review the pathophysiological role of AGEs and their receptor (RAGE)-oxidative stress system in diabetic nephropathy.

Pigment epithelium-derived factor suppresses adipogenesis via inhibition of the MAPK/ERK pathway in 3T3-L1 preadipocytes

We previously reported that circulating levels of pigment epithelium-derived factor (PEDF), a newly identified adipokine, are increased in patients with type 2 diabetes, correlating with body mass index. However, the role of PEDF in adipogenesis remains elusive. In the present study, we have investigated the effects and mechanisms of PEDF on adipocyte differentiation in 3T3-L1 preadipocytes. Differentiation of 3T3-L1 preadipocytes was induced in the presence or absence of human recombinant PEDF protein. The effects of PEDF on adipogenic gene expression, mitotic clonal expansion (MCE), and MAPK activation were investigated. Physiological concentrations of human PEDF protein inhibited adipocyte differentiation, evidenced by decreased lipid accumulation, downregulation of adipocyte markers, and inhibition of master adipogenic transcription factors such as C/EBP-alpha and PPARgamma. The antiadipogenic effects of PEDF were observed only when PEDF was added to the cells on day 0, but not on day 3 during differentiation, suggesting that PEDF targets some early adipogenic events. Similarly, overexpression of PEDF by adenovirus attenuated adipocyte differentiation. Further studies revealed that PEDF, or U-0126, a specific MAPK/ERK inhibitor, sequentially inhibited the early activation of ERK and MCE. Moreover, PEDF attenuated expression and the phosphorylation of C/EBP-beta at Thr(188), an essential step for transcriptional activation of C/EBP-beta. In addition, PEDF expression was decreased significantly in the first 24 h during adipocyte differentiation, suggesting that downregulation of PEDF may be essential for the initiation of MCE and adipogenesis. We conclude that PEDF inhibits adipogenesis in 3T3-L1 preadipocytes partially because of inhibition of the MAPK/ERK signaling pathway and MCE.

Protective role of pigment epithelium-derived factor (PEDF) in early phase of experimental diabetic retinopathy

BACKGROUND

Pigment epithelium-derived factor (PEDF) is the most potent inhibitor of angiogenesis in the mammalian eye, thus suggesting that PEDF may protect against proliferative diabetic retinopathy. However, a role for PEDF in early diabetic retinopathy remains to be elucidated. We investigated here whether and how PEDF could prevent the development of diabetic retinopathy.

METHODS

Streptozotocin-induced diabetic rats were treated with or without intravenous injection of PEDF for 4 weeks. Early neuronal derangements were evaluated by electroretinogram (ERG) and immunofluorescent staining of glial fibrillary acidic protein (GFAP). Expression of PEDF and 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative stress, was localized by immunofluorescence. Vascular endothelial growth factor (VEGF) and p22phox expression were evaluated with western blots. Breakdown of blood retinal barrier (BRB) was quantified with fluorescein isothiocynate (FITC)-conjugated dextran. NADPH oxidase activity was measured with lucigenin luminescence.

RESULTS

Retinal PEDF levels were reduced, and amplitudes of a- and b-wave in the ERG were decreased in diabetic rats, which were in parallel with GFAP overexpression in the Müller cells. Further, retinal 8-OHdG, p22phox and VEGF levels and NADPH oxidase activity were increased, and BRB was broken in diabetic rats. Administration of PEDF ameliorated all of the characteristic changes in early diabetic retinopathy.

CONCLUSIONS

Results suggest that PEDF could prevent neuronal derangements and vascular hyperpermeability in early diabetic retinopathy via inhibition of NADPH oxidase-driven oxidative stress generation. Substitution of PEDF may offer a promising strategy for halting the development of diabetic retinopathy.

Positive association of circulating levels of advanced glycation end products (AGEs) with pigment epithelium-derived factor (PEDF) in a general population

We have recently found that serum levels of pigment epithelium-derived factor (PEDF), a glycoprotein with anti-oxidative and anti-inflammatory properties, are elevated in proportion to the accumulation of the number of the components of the metabolic syndrome. Since formation and accumulation of advanced glycation end products (AGEs) progress under the metabolic syndrome and that PEDF could inhibit the AGE-elicited tissue damage, it is conceivable that PEDF levels may be increased as a counter-system against AGEs in patients with the metabolic syndrome. However, correlation between circulating levels of AGEs and PEDF in humans remains to be elucidated. In this study, we investigated the relationship between serum AGE and PEDF levels in a general population and examined the effects of AGEs on PEDF gene expression in vitro. One hundred ninety-six Japanese subjects in a general population underwent a complete history and physical examination, determination of blood chemistries, including serum levels of AGEs and PEDF. In multiple regression analyses, creatinine, body mass index, triglycerides, AGEs and insulin were independently correlated with serum PEDF levels. AGEs dose-dependently increased PEDF gene expression in cultured adipocytes and liver cells. Our present study demonstrated first that circulating AGEs were one of the independent correlates of serum levels of PEDF. Adipose tissue and liver may be target organs for the AGE-induced PEDF overexpression in humans. Serum PEDF levels may be elevated in response to circulating AGEs as a counter-system against the AGE-elicited tissue damage.

Pigment epithelium-derived factor (PEDF) prevents platelet activation and aggregation in diabetic rats by blocking deleterious effects of advanced glycation end products (AGEs)

BACKGROUND

Alteration of platelet function contributes to microthrombus formation and may play an important role in the pathogenesis of diabetic vascular complications. In addition, there is a growing body of evidence that oxidative stress generation is involved in platelet activation and aggregation in vivo. Since we have recently found that pigment epithelium-derived factor (PEDF) inhibits thrombus formation in rats through its anti-oxidative properties, we investigated here whether PEDF prevented platelet activation and aggregation in diabetic or advanced glycation end products (AGEs)-injected rats.

METHODS AND RESULTS

Experimental diabetes was induced by injecting streptozotocin to Sprague-Dawley rats. Diabetic or non-diabetic Sprague-Dawley rats were injected intravenously with or without 1 mg AGEs-bovine serum albumin or non-glycated bovine serum albumin in the presence or absence of 10 microg PEDF everyday. Administration of PEDF or pyridoxal phosphate, an inhibitor of AGEs formation, inhibited platelet P-selectin expression and aggregation by suppressing NADPH oxidase-driven superoxide generation, and subsequently ameliorated a shortened tail vein bleeding time in diabetic rats. Further, intravenous administration of AGEs to normal rats mimicked the effects of diabetes on platelet activation and bleeding time, which were also blocked by simultaneous administration of PEDF.

CONCLUSIONS

These results demonstrated for the first time that PEDF inhibited platelet activation and aggregation in diabetic rats through its anti-oxidative properties. Our present study suggests that PEDF may play a protective role against diabetic vascular complications by attenuating the deleterious effects of AGEs on platelets.

Pigment epithelium-derived factor (PEDF) inhibits diabetes- or advanced glycation end product (AGE)-induced platelet CD40 ligand overexpression in rats

The formation and accumulation of advanced glycation end products (AGEs) have been known to progress under hyperglycemic conditions, thereby being involved in accelerated atherosclerosis in diabetes. We have recently found that pigment epithelium-derived factor (PEDF), a glycoprotein with potent neuronal cell differentiating activity, could play a protective role against cardiovascular disease (CVD) by attenuating the deleterious effects of AGEs. Although there is a growing body of evidence that inhibition of platelet CD40 ligand (CD40L) expression may be a novel therapeutic target for preventing CVD, effects of PEDF on platelet CD40L expression remain to be elucidated. In this study, we examined the effects of PEDF administration on platelet CD40L expression in diabetic or AGE-injected non-diabetic rats. Further, in order to elucidate the clinical relevance of PEDF administration, we studied whether intraplatelet PEDF levels were decreased in diabetic rats. Platelet CD40L expression levels were increased by about 2-folds in diabetic rats, which were partly blocked by the treatment with PEDF. Further, AGE injection to non-diabetic rats was found to increase platelet CD40L expression levels by about 1.3-folds, whose effects were completely prevented by the treatment with PEDF. Intraplatelet PEDF levels in diabetic rats were significantly decreased, compared with control rats. Our present study suggests that PEDF could inhibit platelet CD40L overexpression in diabetes by blocking the effects of AGEs on platelets. Pharmacological up-regulation or substitution of PEDF may offer a novel promising strategy for preventing CVD in diabetes.

Phosphomannopentaose sulfate (PI-88) inhibits retinal leukostasis in diabetic rat

Retinal leukostasis, mediated by intracellular adhesion molecule-1 (ICAM-1) and vascular endothelial growth factor (VEGF), has been implicated in the pathogenesis of early diabetic retinopathy. Phosphomannopentaose sulfate (PI-88) is a highly sulfonated oligosaccharide which inhibits heparanase activity and competes with heparan sulfate binding to growth factors. In this study, we evaluated whether PI-88 could inhibit retinal leukostasis in strepotzotocin(STZ)-induced diabetic rat and elucidated the possible mechanisms. Diabetes was induced in Sprague-Dawley rats by intraperitoneal injection (i.p.) of STZ. Three months after induction, diabetic rats were administered PI-88 (25 mg/kg body weight) or vehicle solution daily via i.p. for 14 consecutive days. Leukostasis was analyzed on retinal flatmounts by concanavalin A and CD45 immunofluorescence staining. Retinal function was analyzed by electroretinography (ERG). ICAM-1 and VEGF levels in retinas were studied by Western blot and enzyme-linked immunosorbent assay (ELISA) respectively. The systemic administration of PI-88, but not vehicle, significantly decreased the number of adherent leukocytes in retinas by 52.24% (P<0.001) and led to significant preservation (about 50%, P<0.001) of scotopic ERG a- and b-wave amplitudes in treated diabetic rats as compared to those of diabetic control rats. These changes were associated with downregulation of ICAM-1 (45%, P<0.001) and VEGF (26.83+/-2.01 versus 40.8+/-3.24 pg/mg, P<0.01) in retinas of PI-88 treated diabetic rats as compared to those of diabetic control rats. PI-88 significantly inhibited retinal leukostasis and reversed retinal dysfunction by a mechanism that may include decreased ICAM-1 and VEGF expression in diabetic rats. Our data suggests that PI-88 is a promising agent for the treatment of diabetic retinopathy.

Serum levels of pigment epithelium-derived factor (PEDF) are positively associated with visceral adiposity in Japanese patients with type 2 diabetes

BACKGROUND

Pigment epithelium-derived factor (PEDF) inhibits endothelial cell injury. Further, serum levels of PEDF are elevated in the metabolic syndrome. These observations suggest that PEDF may be elevated as a counter-system against vascular cell damage in the metabolic syndrome. However, little is known about the regulation of PEDF in patients with diabetes. In order to clarify the determinants of serum PEDF, here, we examined the relationship between the 1-year changes in PEDF levels and those in anthropometric and metabolic variables in type 2 diabetic patients.

METHODS

Eighty-six consecutive outpatients with type 2 diabetes underwent a complete history and physical examination, determination of blood chemistries, and serum levels of PEDF at baseline and 1 year after. PEDF gene expression in cultured subcutaneous or omental adipocytes were analysed by quantitative real-time reverse transcription-polymerase chain reactions.

RESULTS

Multiple regression analyses revealed that waist circumference, triglycerides, creatinine, and TNF-alpha were independently associated with PEDF. Further, the percent changes in serum levels of PEDF during 1-year observational periods were positively correlated with those of BMI. In addition, PEDF mRNA levels in cultured adipocytes were increased in parallel to the BMI values of subjects from whom adipocytes were derived, especially in omental adipocytes.

CONCLUSION

These results demonstrated that serum levels of PEDF were positively associated with metabolic components and TNF-alpha in Japanese patients with type 2 diabetes. Our present study suggests that PEDF may be generated from adipose tissues and play some role in visceral obesity in type 2 diabetic patients.

Pigment epithelium-derived factor mitigates inflammation and oxidative stress in retinal pericytes exposed to oxidized low-density lipoprotein

Oxidized and/or glycated low-density lipoprotein (LDL) may mediate capillary injury in diabetic retinopathy. The mechanisms may involve pro-inflammatory and pro-oxidant effects on retinal capillary pericytes. In this study, these effects, and the protective effects of pigment epithelium-derived factor (PEDF), were defined in a primary human pericyte model. Human retinal pericytes were exposed to 100 microg/ml native LDL (N-LDL) or heavily oxidized glycated LDL (HOG-LDL) with or without PEDF at 10-160 nM for 24 h. To assess pro-inflammatory effects, monocyte chemoattractant protein-1 (MCP-1) secretion was measured by ELISA, and nuclear factor-kappaB (NF-kappaB) activation was detected by immunocytochemistry. Oxidative stress was determined by measuring intracellular reactive oxygen species (ROS), peroxynitrite (ONOO(-)) formation, inducible nitric oxide synthase (iNOS) expression, and nitric oxide (NO) production. The results showed that MCP-1 was significantly increased by HOG-LDL, and the effect was attenuated by PEDF in a dose-dependent manner. PEDF also attenuated the HOG-LDL-induced NF-kappaB activation, suggesting that the inhibitory effect of PEDF on MCP-1 was at least partially through the blockade of NF-kappaB activation. Further studies demonstrated that HOG-LDL, but not N-LDL, significantly increased ONOO(-) formation, NO production, and iNOS expression. These changes were also alleviated by PEDF. Moreover, PEDF significantly ameliorated HOG-LDL-induced ROS generation through up-regulation of superoxide dismutase 1 expression. Taken together, these results demonstrate pro-inflammatory and pro-oxidant effects of HOG-LDL on retinal pericytes, which were effectively ameliorated by PEDF. Suppressing MCP-1 production and thus inhibiting macrophage recruitment may represent a new mechanism for the salutary effect of PEDF in diabetic retinopathy and warrants more studies in future.

Aqueous humour levels of asymmetric dimethylarginine (ADMA) are correlated with pigment epithelium-derived factor (PEDF) in patients with uveitis

The association between the aqueous humour levels of asymmetric dimethylarginine (ADMA) and pigment epithelium-derived factor (PEDF) was evaluated. Aqueous humour levels of ADMA and PEDF were measured by high-performance liquid chromatography and enzyme-linked immunosorbent assay, respectively, in 31 uveitis samples and nine cataract control samples. Aqueous humour ADMA and PEDF levels were significantly higher in infectious and non-infectious uveitis patients than in controls (0.67+/-0.04 nmol/ml and 0.55+/-0.03 nmol/ml versus 0.43+/-0.04 nmol/ml for ADMA; 8.22+/-1.45 microg/ml and 5.22+/-0.95 microg/ml versus 1.32+/-0.22 microg/ml for PEDF). A significant positive correlation between ADMA and PEDF levels in aqueous humour was found in control and uveitis patients. These results demonstrated that the aqueous humour level of ADMA is correlated with PEDF in humans and suggest that both ADMA and PEDF in aqueous humour may be elevated in response to inflammation in uveitis.