Pigment epithelium-derived factor (PEDF) blocks angiotensin II signaling in endothelial cells via suppression of NADPH oxidase: a novel anti-oxidative mechanism of PEDF

Pigment epithelium-derived factor expression and role in follicular development

RESEARCH QUESTION

What is the involvement of pigment epithelium-derived factor (PEDF), expressed in granulosa cells, in folliculogenesis?

DESIGN

mRNA expression of PEDF and other key factors [Cyp19, anti-Müllerian hormone receptor (AMHR) and vascular endothelial growth factor (VEGF)] in mice follicles was examined in order to typify the expression of PEDF in growing follicles and in human primary granulosa cells (hpGC), and to follow the interplay between PEDF and the other main players in folliculogenesis: FSH and AMH.

RESULTS

mRNA expression of PEDF increased through folliculogenesis, although the pattern differed from that of the other examined genes, affecting the follicular angiogenic and oxidative balance. In hpGC, prolonged exposure to FSH stimulated the up-regulation of PEDF mRNA. Furthermore, a negative correlation between AMH and PEDF was observed: AMH stimulation reduced the expression of PEDF mRNA and PEDF stimulation reduced the expression of AMHR mRNA.

CONCLUSIONS

Folliculogenesis, an intricate process that requires close dialogue between the oocyte and its supporting granulosa cells, is mediated by various endocrine and paracrine factors. The current findings suggest that PEDF, expressed in granulosa cells, is a pro-folliculogenesis player that interacts with FSH and AMH in the process of follicular growth. However, the mechanism of this process is yet to be determined.

The Various Roles of PEDF in Cancer

Pigment epithelium-derived factor (PEDF) is a natural immunomodulator, anti-inflammatory, anti-angiogenic, anti-tumour growth and anti-metastasis factor, which can enhance tumour response to PEDF but can also conversely have pro-cancerous effects. Inflammation is a major cause of cancer, and it has been proven that PEDF has anti-inflammatory properties. PEDF's functional activity can be investigated through measuring metastatic and metabolic biomarkers that will be discussed in this review.

Pigment Epithelium-Derived Factor: Inhibition of Phosphorylation of Insulin Receptor (IR)/IR Substrate (IRS), Osteogeneration from Adipocytes, and Increased Levels Due to Doxorubicin Exposure

OBJECTIVES

Pigment epithelium-derived factor (PEDF) has been recently linked to insulin resistance and is capable of differentiating myocytes to bone. We examined in more detail the intricate signalling of the insulin pathway influenced by PEDF in skeletal myocytes. We tested whether this serpin is also capable of generating de novo bone from adipocytes in vitro and in vivo, and how the anticancer drug doxorubicin links with PEDF and cellular metabolism.

METHODS AND KEY FINDINGS

We demonstrate that PEDF can inhibit phosphorylation of insulin receptor (IR) and insulin receptor substrate (IRS) in skeletal myocytes. PEDF constitutively activates p42/44 MAPK/Erk, but paradoxically does not affect mitogenic signalling. PEDF did not perturb either mitochondrial activity or proliferation in cells representing mesenchymal stem cells, cardiomyocytes, and skeletal myocytes and adipocytes. PEDF induced transdifferentiation of adipocytes to osteoblasts, promoting bone formation in cultured adipocytes in vitro and gelfoam fatpad implants in vivo. Bone formation in white adipose tissue (WAT) was better than in brown adipose tissue (BAT). The frontline anticancer drug doxorubicin increased levels of PEDF in a human breast cancer cell line, mirroring the in vivo finding where cardiac muscle tissue was stained increasingly for PEDF as the dose of doxorubicin increased in mice. PEDF also increased levels of reactive oxygen species (ROS) and glutathione (GSH) in the breast cancer cell line.

CONCLUSIONS

PEDF may be used to regenerate bone from adipose tissue in cases of trauma such as fractures or bone cancers. The increased presence of PEDF in doxorubicin-treated tumour cells need further exploration, and could be useful therapeutically in future. The safety of PEDF administration in vivo was further demonstrated in this study.

Pigment epithelium-derived factor negates oxidative stress in mouse oocytes

Molecular changes, caused by various environmental factors, affect the quality and developmental potential of oocytes. Oxidative stress (OS) is a major factor involved in various gynecologic disorders and/or in aging. Recent studies suggest that elevated reactive oxygen species (ROS) hamper oocyte quality and future embryonic development. Pigment epithelium-derived factor (PEDF) is a pleiotropic protein, known for its antiangiogenic, anti-inflammatory, and antioxidative properties. Our previous findings demonstrate the antioxidative role of rPEDF in maintaining granulosa cell viability. In the current study, we examined the ability of PEDF to negate the adverse impact of OS on oocytes. Maturation rate of oocytes exposed to OS was significantly lower than that of control oocytes. The number of mtDNA copies in OS-exposed oocytes was significantly higher than in control oocytes (>3 times), whereas ATP concentration was significantly lower. Oocytes exposed to OS demonstrated impaired chromosome arrangement at the metaphase plate. PEDF significantly improved maturation rate of untreated OS-exposed oocytes. Moreover, mtDNA copy number, ATP concentration, and chromosome arrangement at the metaphase plate in rPEDF-treated OS-exposed oocytes were restored to the level of control oocytes. Our findings demonstrate that OS hampers the ability of oocytes to undergo proper in vitro maturation. The energetic balance of OS-exposed oocyte is characterized by excessive mtDNA replication and reduced ATP concentration; it hampers the ability of oocytes to perform high fidelity chromosome segregation. PEDF alleviates this damage, improves the rate of oocyte maturation, and preserves mtDNA level and ATP content, thus enabling oocytes to form proper metaphase plate and improve oocyte competence.

The effect of methylethylpiridinol addition to the therapy on the level of pigment epithelium-derived factor and oxidative status in patients with diabetic nephropathy: randomized controlled open-label clinical study

Purpose

The diabetic nephropathy is associated with oxidative stress and increases in pigment epithelium-derived factor (PEDF) level in the patient's blood. For the first time, authors investigated the effect of methylethylpiridinol addition to the therapy on oxidative status and pigment epithelium-derived factor concentrations, and examined the relationship between these indicators and clinical markers of pathology development.

Methods

Study design: open label randomized controlled trial study. Authors assessed the effect of methylethylpiridinol addition to the therapy vs basic treatment on antioxidant and NADPH-generating enzymes activity, glutathione's concentration and free radical-induced oxidation's intensity using a spectrophotometric method and iron-induced biochemiluminescence. The pigment epithelium-derived factor concentration in the serum was measured by enzyme-linked immunosorbent assay.

Results

Patients receiving combination therapy with methylethylpiridinol showed a more substantial increase in activity of glutathione peroxidase (Δ = 0.04 ± 0.11, p = 0.002), glutathione transferase (Δ = 0.12 ± 0.08, p < 0.001) and the concentration of reduced glutathione (Δ = 0.30 ± 0.17, p = 0.039). In addition, there was a significant decrease in PEDF level (Δ = -6.4 ± 5.4, p = 0.004). Correlation analysis showed a negative link between Δ postprandial glucose and Δ NADP-isocitrate dehydrogenase (-0.39, p = 0.033), Δ reduced glutathione and Δ postprandial glucose (-0.372, p = 0.043), Δ glutathione transferase and Δ PEDF (-0.37, p = 0.044).

Conclusions

The methylethylpiridinol addition to the therapy had a more potent stimulating effect on the patients' oxidative status in comparison with standard treatment, and reliably decreased pigment epithelium-derived factor level in patients' serum. The observed differences seem to be associated with the antioxidant activity of methylethylpiridinol which contributing to the mitigation of oxidative stress reducing at diabetes mellitus.

Pigment epithelium-derived factor (PEDF) and PEDF-receptor in the adult mouse brain: Differential spatial/temporal localization pattern

Pigment epithelium-derived factor (PEDF) is a multifunctional protein which was initially described in the retina, although it is also present in other tissues. It functions as an antioxidant agent promoting neuronal survival. Recently, a PEDF receptor has shown an elevated binding affinity for PEDF. There are no relevant data regarding the distribution of both proteins in the brain, therefore the main goal of this work was to investigate the spatiotemporal presence of PEDF and PEDFR in the adult mouse brain, and to determine the PEDF blood level in mouse and human. The localization of both proteins was analyzed by different experimental methods such as immunohistochemistry, western-blotting, and also by enzyme-linked immunosorbent assay. Differential expression was found in some telencephalic structures and positive signals for both proteins were detected in the cerebellum. The magnitude of the PEDFR labeling pattern was higher than PEDF and included some cortical and subventricular areas. Age-dependent changes in intensity of both protein immunoreactions were found in the cortical and hippocampal areas with greater reactivity between 4 and 8 months of age, whilst others, like the subventricular zones, these differences were more evident for PEDFR. Although ubiquitous presence was not found in the brain for these two proteins, their relevant functions must not be underestimated. It has been described that PEDF plays an important role in neuroprotection and data provided in the present work represents the first extensive study to understand the relevance of these two proteins in specific brain areas.

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.

Novel Associations between Related Proteins and Cellular Effects of High-Density Lipoprotein

BACKGROUND AND OBJECTIVES

Recent studies have examined the structure-function relationship of high-density lipoprotein (HDL). This study aimed to identify and rank HDL-associated proteins involved in several biological function of HDL.

METHODS

HDLs isolated from 48 participants were analyzed. Cholesterol efflux capacity, effect of HDL on nitric oxide production, and vascular cell adhesion molecule-1 expression were assessed. The relative abundance of identified proteins in the highest vs. lowest quartile was expressed using the normalized spectral abundance factor ratio.

RESULTS

After adjustment by multiple testing, six proteins, thyroxine-binding globulin, alpha-1B-glycoprotein, plasma serine protease inhibitor, vitronectin, angiotensinogen, and serum amyloid A-4, were more abundant (relative abundance ratio ≥2) in HDLs with the highest cholesterol efflux capacity. In contrast, three proteins, complement C4-A, alpha-2-macroglobulin, and immunoglobulin mu chain C region, were less abundant (relative abundance ratio <0.5). In terms of nitric oxide production and vascular cell adhesion molecule-1 expression, no proteins showed abundance ratios ≥2 or <0.5 after adjustment. Proteins correlated with the functional parameters of HDL belonged to diverse biological categories.

CONCLUSIONS

In summary, this study ranked proteins showing higher or lower abundance in HDLs with high functional capacities and newly identified multiple proteins linked to cholesterol efflux capacity.

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.

NADPH oxidases and oxidase crosstalk in cardiovascular diseases: novel therapeutic targets

Reactive oxygen species (ROS)-dependent production of ROS underlies sustained oxidative stress, which has been implicated in the pathogenesis of cardiovascular diseases such as hypertension, aortic aneurysm, hypercholesterolaemia, atherosclerosis, diabetic vascular complications, cardiac ischaemia-reperfusion injury, myocardial infarction, heart failure and cardiac arrhythmias. Interactions between different oxidases or oxidase systems have been intensively investigated for their roles in inducing sustained oxidative stress. In this Review, we discuss the latest data on the pathobiology of each oxidase component, the complex crosstalk between different oxidase components and the consequences of this crosstalk in mediating cardiovascular disease processes, focusing on the central role of particular NADPH oxidase (NOX) isoforms that are activated in specific cardiovascular diseases. An improved understanding of these mechanisms might facilitate the development of novel therapeutic agents targeting these oxidase systems and their interactions, which could be effective in the prevention and treatment of cardiovascular disorders.

A Draft Map of the Human Ovarian Proteome for Tissue Engineering and Clinical Applications

Fertility preservation research in women today is increasingly taking advantage of bioengineering techniques to develop new biomimetic materials and solutions to safeguard ovarian cell function and microenvironment in vitro, and in vivo,. However, available data on the human ovary are limited and fundamental differences between animal models and humans are hampering researchers in their quest for more extensive knowledge of human ovarian physiology and key reproductive proteins that need to be preserved. We therefore turned to multi-dimensional label-free mass spectrometry to analyze human ovarian cortex, as it is a high-throughput and conclusive technique providing information on the proteomic composition of complex tissues like the ovary. In-depth proteomic profiling through two-dimensional liquid chromatography-mass spectrometry, Western blotting, histological and immunohistochemical analyses, and data mining helped us to confidently identify 1508 proteins. Moreover, our method allowed us to chart the most complete representation so far of the ovarian matrisome, defined as the ensemble of extracellular matrix proteins and associated factors, including more than 80 proteins. In conclusion, this study will provide a better understanding of ovarian proteomics, with a detailed characterization of the ovarian follicle microenvironment, in order to enable bioengineers to create biomimetic scaffolds for transplantation and three-dimensional in vitro, culture. By publishing our proteomic data, we also hope to contribute to accelerating biomedical research into ovarian health and disease in general.

G Protein-Coupled Estrogen Receptor Protects From Angiotensin II-Induced Increases in Pulse Pressure and Oxidative Stress

Our previous work showed that the G protein-coupled estrogen receptor (GPER) is protective in the vasculature and kidneys during angiotensin (Ang) II-dependent hypertension by inhibiting oxidative stress. The goal of the current study was to assess the impact of GPER deletion on sex differences in Ang II-induced hypertension and oxidative stress. Male and female wildtype and GPER knockout mice were implanted with radiotelemetry probes for measurement of baseline blood pressure before infusion of Ang II (700 ng/kg/min) for 2 weeks. Mean arterial pressure was increased to the same extent in all groups, but female wildtype mice were protected from Ang II-induced increases in pulse pressure, aortic wall thickness, and Nox4 mRNA. In vitro studies using vascular smooth muscle cells found that pre-treatment with the GPER agonist G-1 inhibited Ang II-induced ROS and NADP/NADPH. Ang II increased while G-1 decreased Nox4 mRNA and protein. The effects of Ang II were blocked by losartan and Nox4 siRNA, while the effects of G-1 were inhibited by adenylyl cyclase inhibition and mimicked by phosphodiesterase inhibition. We conclude that during conditions of elevated Ang II, GPER via the cAMP pathway suppresses Nox4 transcription to limit ROS production and prevent arterial stiffening. Taken together with our previous work, this study provides insight into how acute estrogen signaling via GPER provides cardiovascular protection during Ang II hypertension and potentially other diseases characterized by increased oxidative stress.

Loss of pigment epithelium-derived factor leads to ovarian oxidative damage accompanied by diminished ovarian reserve in mice

AIMS

This study aims to investigate the pathophysiological role and mechanism of pigment epithelium-derived factor (PEDF) deletion in ovarian damage.

METHODS

Female PEDF-knockout mice and their wild-type littermates were used in this study. Relevant tests were performed at 8-10 weeks or 32 weeks of age.

KEY FINDINGS

Compared to the wild-type mice, the PEDF-knockout mice showed diminished ovarian reserve (DOR), worse ovum quality after injection to induce controlled ovarian stimulation, increased serum follicle stimulating hormone (FSH) level and an follicle stimulating hormone/luteinizing hormone (FSH/LH) ratio. Moreover, severe ovarian oxidative damage was found in ovaries of PEDF-knockout mice that mainly manifested as an accumulation of reactive oxygen species (ROS), NF‑E2-related factor 2 (Nrf2) pathway activation, significantly upregulated expression of ROS-generating genes. Correspondingly, the PEDF-knockout mice exhibited lipid metabolism disorder and insulin resistance, which mainly manifested as obesity, abdominal fat accumulation, adipocyte enlargement, severe ectopic fat deposition, dyslipidemia, changes in adipokine levels, hyperglycemia, hyperinsulinemia, impaired glucose tolerance, impaired insulin tolerance and significantly declined protein kinase B (Akt) phosphorylation levels.

SIGNIFICANCE

Loss of PEDF leads to ovarian oxidative damage accompanied by DOR in mice, this is related to PEDF deficiency induced severe insulin resistance and lipid metabolism disorder. Therefore, PEDF may be a potential target for the treatment of diseases related to ovarian oxidative damage.

The effects of pigment epithelium-derived factor on atherosclerosis: putative mechanisms of the process

Cardiovascular disease (CVD) is a leading cause of death worldwide. Atherosclerosis is believed to be the major cause of CVD, characterized by atherosclerotic lesion formation and plaque disruption. Although remarkable advances in understanding the mechanisms of atherosclerosis have been made, the application of these theories is still limited in the prevention and treatment of atherosclerosis. Therefore, novel and effective strategies to treat high-risk patients with atherosclerosis require further development. Pigment epithelium-derived factor (PEDF), a glycoprotein with anti-inflammatory, anti-oxidant, anti-angiogenic, anti-thrombotic and anti-tumorigenic properties, is of considerable interest in the prevention of atherosclerosis. Accumulating research has suggested that PEDF exerts beneficial effects on atherosclerotic lesions and CVD patients. Our group, along with colleagues, has demonstrated that PEDF may be associated with acute coronary syndrome (ACS), and that the polymorphisms of rs8075977 of PEDF are correlated with coronary artery disease (CAD). Moreover, we have explored the anti-atherosclerosis mechanisms of PEDF, showing that oxidized-low density lipoprotein (ox-LDL) reduced PEDF concentrations through the upregulation of reactive oxygen species (ROS), and that D-4F can protect endothelial cells against ox-LDL-induced injury by preventing the downregulation of PEDF. Additionally, PEDF might alleviate endothelial injury by inhibiting the Wnt/β-catenin pathway. These data suggest that PEDF may be a novel therapeutic target for the treatment of atherosclerosis. In this review, we will summarize the role of PEDF in the development of atherosclerosis, focusing on endothelial dysfunction, inflammation, oxidative stress, angiogenesis and cell proliferation. We will also discuss its promising therapeutic implications for atherosclerosis.

Pigment epithelium derived factor (PEDF) expression in the male tract of Wistar rats

Pigment epithelium derived factor (PEDF) expression has been described in many organs as showing neurotrophic, anti-angiogenic, anti-apoptotic, anti-inflammatory, anti-oxidant and pro-cell survival properties. However, references to its activity in the male reproductive system are scarce. We aimed to characterize the expression of PEDF in the male reproductive tract of Wistar rats by using RT-PCR, western blot and immunostaining and also evaluate the effect of flutamide in PEDF expression. We found that PEDF is expressed in the epididymis, prostate and seminal vesicles in Wistar rats, but notably not in the testes. Under the effect of flutamide PEDF expression decreased, recovering by suppressing the antiandrogen. The epididymis is an essential organ in sperm maturation-storages. The role of PEDF in this physiological process has not been fully elucidated yet, but considering that in other systems PEDF has anti-apoptotic, anti-oxidants and pro-cell survival properties, its expression along the epididymis could play a role in the protection of spermatozoa while they are stored.

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.

Recovery of Corneal Sensitivity and Increase in Nerve Density and Wound Healing in Diabetic Mice After PEDF Plus DHA Treatment

Diabetic keratopathy decreases corneal sensation and tear secretion and delays wound healing after injury. In the current study, we tested the effect of treatment with pigment epithelium-derived factor (PEDF) in combination with docosahexaenoic acid (DHA) on corneal nerve regeneration in a mouse model of diabetes with or without corneal injury. The study was performed in streptozotocin-induced diabetic mice (C57BL/6). Ten weeks after streptozotocin injection, diabetic mice showed significant decreases of corneal sensitivity, tear production, and epithelial subbasal nerve density when compared with age-matched normal mice. After diabetic mice were wounded in the right eye and treated in both eyes with PEDF+DHA for 2 weeks, there was a significant increase in corneal epithelial nerve regeneration and substance P-positive nerve density in both wounded and unwounded eyes compared with vehicle-treated corneas. There also was elevated corneal sensitivity and tear production in the treated corneas compared with vehicle. In addition, PEDF+DHA accelerated corneal wound healing, selectively recruited type 2 macrophages, and prevented neutrophil infiltration in diabetic wounded corneas. These results suggest that topical treatment with PEDF+DHA promotes corneal nerve regeneration and wound healing in diabetic mice and could potentially be exploited as a therapeutic option for the treatment of diabetic keratopathy.

Pigment epithelial-derived factor in human fetal membranes

OBJECTIVE

Our main objective was to document, pigment epithelial-derived factor (PEDF), a secreted serine protease inhibitor with anti-angiogenic, anti-inflammatory, and anti-oxidant properties, expression in human fetal membranes from preterm prelabor rupture of the membranes (pPROM) and in in vitro cultures stimulated with cigarette smoke extract (CSE) or lipopolysaccharides (LPS), two major risk factors for pPROM (behavioral and bacterial, respectively).

METHOD

We documented PEDF mRNA expression in clinical samples of fetal membranes from patients with pPROM using quantitative RT-PCR. Also, mRNA and protein levels were documented in fetal membranes (from normal term cesarean sections [not in labor]) in an organ explant system stimulated with CSE or lipopolysaccharide (LPS). Immunohistochemistry (IHC) was used to localize PEDF in fetal membranes.

RESULTS

We report no changes in PEDF mRNA expression in pPROM compared to term births (p = .59) or after treatment with CSE or LPS. However, by adding sulforaphane the PEDF mRNA expression increased significantly p < .000032. PEDF was localized to both amnion and chorion layers, but no difference was seen in staining intensities after CSE or LPS treatment compared to control.

CONCLUSIONS

PEDF, a product of fetal membrane cells, is unaltered in pPROM or after exposure to risk factors of pPROM. The antioxidant stimulating substance sulforaphane contribute to an increase in PEDF mRNA in fetal membranes.

Pigment epithelium-derived factor alleviates endothelial injury by inhibiting Wnt/β-catenin pathway

Background

Oxidized low-density lipoprotein (ox-LDL) can induce endothelial injury and plays a vital role in the procession and development of atherosclerosis. Little is known regarding whether Wnt/β-catenin pathway is involved in ox-LDL-induced endothelial injury or whether it further promotes atherosclerosis via increased oxidative stress. This study aimed to investigate the role of Wnt/β-catenin pathway in ox-LDL-induced vascular endothelial injury and determine whether pigment epithelium-derived factor (PEDF) could alleviate ox-LDL-induced endothelial injury by inhibiting Wnt/β-catenin pathway.

Methods

Injury of human umbilical vein endothelial cells (HUVECs) was evaluated with an MTT assay, by monitoring lactate dehydrogenase (LDH) release and determining the apoptotic ratio. The expression of β-catenin (non-phosphorylated-β-catenin), disheveled-1 (Dvl-1) and Cyclin D1 was analyzed with western blotting and quantitative real-time PCR. Oxidative stress status was assessed by measuring the levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD) and nitric oxide (NO).

Results

Exposure of HUVECs to ox-LDL led to a decrease in cell viability and an increase in LDH release and apoptosis with concomitant enhancement of oxidative stress, as assessed by increased ROS and MDA generation, as well as decreased SOD activity and NO levels. Similar to lithium chloride (LiCl, a Wnt/β-catenin pathway activator), ox-LDL up-regulated the expression of β-catenin, Dvl-1 and Cyclin D1, markers of Wnt/β-catenin pathway activation. However, ox-LDL-induced activation of Wnt/β-catenin pathway, as well as ox-LDL-induced cell injury and oxidative stress, were synergistically promoted by LiCl and mitigated by Dickkopf 1 (DKK-1), an inhibitor of Wnt/β-catenin pathway. Additionally, ox-LDL-induced HUVEC injury and apoptosis, oxidative stress and activation of Wnt/β-catenin pathway were suppressed by PEDF, while they were further strengthened by a small interfering RNA of PEDF.

Conclusion

Wnt/β-catenin pathway may mediate ox-LDL-induced endothelial injury via oxidative stress, and PEDF ameliorates endothelial injury by suppressing Wnt/β-catenin pathway and subsequently reducing oxidative stress.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0407-8) contains supplementary material, which is available to authorized users.

Change of concept about the regulation of angiotensin II-induced monocyte chemoattractant protein-1 production in human endothelial cells

AIMS

Some intriguing clinical observations about the anti-inflammatory effects of angiotensin type 1 (AT1) receptor blockers and angiotensin converting enzyme inhibitors in cardiovascular patients brought us to study the signalling pathways which lead to angiotensin II (ANG)-induced monocyte chemoattractant protein-1 (MCP-1) production in human endothelial cells.

METHODS

MCP-1 production in human umbilical vein endothelial cells (HUVECs) under treatments with ANG, AT1 and angiotensin type 2 (AT2) receptor blockers and pravastatin was measured by ELISA. The expression of AT1 and AT2 receptors and NADPH oxidase catalytic subunits (NOX 1-5) was analysed at mRNA and protein levels. Nuclear factor-kappa B (NF-κB) activation was studied by p65 subunit translocation to the cellular nucleus. Cell viability was tested by the MTT method. Nox4 subcellular distribution was analysed by subcellular protein fractionation and by immunoprecipitation followed by matrix-assisted laser desorption/ionization mass spectrometry analysis.

RESULTS

ANG-induced MCP-1 production was mediated by AT2 receptor, but not AT1 receptor in HUVECs in culture, which in turn activated NF-κB, promoting p65 subunit translocation to the nucleus. Reactive oxygen species produced by NADPH oxidase participated in this activation, mainly by the Nox4 subunit, ubiquitously expressed in all the compartments of HUVECs. Pravastatin inhibited ANG-induced MCP-1 production.

CONCLUSIONS

Our results support that ANG-induced MCP-1 production in HUVECs is mediated by AT2 instead AT1 receptor activation, which in turn activates NF-κB involving reactive oxygen species produced by the NADPH oxidase complex. Statins can also block ANG-induced MCP-1 production, probably by their inhibitory effects on NADPH oxidase activity.

PEDF and its roles in physiological and pathological conditions: implication in diabetic and hypoxia-induced angiogenic diseases

Pigment epithelium-derived factor (PEDF) is a broadly expressed multifunctional member of the serine proteinase inhibitor (serpin) family. This widely studied protein plays critical roles in many physiological and pathophysiological processes, including neuroprotection, angiogenesis, fibrogenesis and inflammation. The present review summarizes the temporal and spatial distribution patterns of PEDF in a variety of developing and adult organs, and discusses its functions in maintaining physiological homoeostasis. The major focus of the present review is to discuss the implication of PEDF in diabetic and hypoxia-induced angiogenesis, and the pathways mediating PEDF's effects under these conditions. Furthermore, the regulatory mechanisms of PEDF expression, function and degradation are also reviewed. Finally, the therapeutic potential of PEDF as an anti-angiogenic drug is briefly summarized.

Upstream regulators and downstream effectors of NADPH oxidases as novel therapeutic targets for diabetic kidney disease

Oxidative stress has been linked to the pathogenesis of diabetic nephropathy, the complication of diabetes in the kidney. NADPH oxidases of the Nox family, and in particular the homologue Nox4, are a major source of reactive oxygen species in the diabetic kidney and are critical mediators of redox signaling in glomerular and tubulointerstitial cells exposed to the diabetic milieu. Here, we present an overview of the current knowledge related to the understanding of the role of Nox enzymes in the processes that control mesangial cell, podocyte and tubulointerstitial cell injury induced by hyperglycemia and other predominant factors enhanced in the diabetic milieu, including the renin-angiotensin system and transforming growth factor-β. The nature of the upstream modulators of Nox enzymes as well as the downstream targets of the Nox NADPH oxidases implicated in the propagation of the redox processes that alter renal biology in diabetes will be highlighted.

D-4F, an apolipoprotein A-I mimetic peptide, protects human umbilical vein endothelial cells from oxidized low-density lipoprotein-induced injury by preventing the downregulation of pigment epithelium-derived factor expression

AIM

To investigate the protective effects of D-4F, an apolipoprotein A-I mimetic peptide, on oxidized low-density lipoprotein (ox-LDL)-induced injury of vascular endothelial cells and the potential role of pigment epithelium-derived factor (PEDF).

METHODS

Cytotoxicity was assessed by the apoptotic rate, 3-(4,5-dimethylthiazol-2-y-l)-2,5-diphenyl-2H-tetrazolium bromide assay, and lactate dehydrogenase release. PEDF levels were analyzed with Western blot and quantitative real-time polymerase chain reaction. Redox status was measured by the levels of the reactive oxygen species, malondialdehyde, superoxide dismutase, and nitric oxide.

RESULTS

Ox-LDL reduced cell viability and induced apoptosis and LDH release from human umbilical vein endothelial cells, but the cytotoxic effects of ox-LDL were significantly inhibited by pretreatment with D-4F. Additionally, D-4F could scavenge intracellular reactive oxygen species, suppress the production of lipid peroxides, and improve endogenous antioxidant activity. Ox-LDL decreased PEDF expression in human umbilical vein endothelial cells in a concentration-dependent manner, and this decrease was markedly attenuated by D-4F. However, silencing PEDF by short interfering RNA blocked the inhibitory effects of D-4F on ox-LDL-induced oxidative stress and cellular injury.

CONCLUSIONS

D-4F effectively protects vascular endothelial cells against ox-LDL-induced injury by preventing the downregulation of PEDF expression.

The angiotensin-converting enzyme 2/angiotensin (1-7)/Mas axis protects against lung fibroblast migration and lung fibrosis by inhibiting the NOX4-derived ROS-mediated RhoA/Rho kinase pathway

Reactive oxygen species (ROS) generated by NADPH oxidase-4 (NOX4) have been shown to initiate lung fibrosis. The migration of lung fibroblasts to the injured area is a crucial early step in lung fibrosis. The angiotensin-converting enzyme 2 (ACE2)/angiotensin (1-7) [Ang(1-7)]/Mas axis, which counteracts the ACE/angiotensin II (AngII)/angiotensin II type 1 receptor (AT1R) axis, has been shown to attenuate pulmonary fibrosis. Nevertheless, the exact molecular mechanism remains unclear.

AIMS

To investigate the different effects of the two axes of the renin-angiotensin system (RAS) on lung fibroblast migration and extracellular matrix accumulation by regulating the NOX4-derived ROS-mediated RhoA/Rho kinase (Rock) pathway.

RESULTS

In vitro, AngII significantly increased the NOX4 level and ROS production in lung fibroblasts, which stimulated cell migration and α-collagen I synthesis through the RhoA/Rock pathway. These effects were attenuated by N-acetylcysteine (NAC), diphenylene iodonium, and NOX4 RNA interference. Moreover, Ang(1-7) and lentivirus-mediated ACE2 (lentiACE2) suppressed AngII-induced migration and α-collagen I synthesis by inhibiting the NOX4-derived ROS-mediated RhoA/Rock pathway. However, Ang(1-7) alone exerted analogous effects on AngII. In vivo, constant infusion with Ang(1-7) or intratracheal instillation with lenti-ACE2 shifted the RAS balance toward the ACE2/Ang(1-7)/Mas axis, alleviated bleomycin-induced lung fibrosis, and inhibited the RhoA/Rock pathway by reducing NOX4-derived ROS.

INNOVATION

This study suggests that the ACE2/Ang(1-7)/Mas axis may be targeted by novel pharmacological antioxidant strategies to treat lung fibrosis induced by AngII-mediated ROS.

CONCLUSION

The ACE2/Ang(1-7)/Mas axis protects against lung fibroblast migration and lung fibrosis by inhibiting the NOX4-derived ROS-mediated RhoA/Rock pathway.

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.

Role of pigment epithelium-derived factor in the reproductive system

The physiological function of the female reproductive organs is hormonally controlled. In each cycle, the reproductive organs undergo tissue modifications that are accompanied by formation and destruction of blood vessels. Proper angiogenesis requires an accurate balance between stimulatory and inhibitory signals, provided by pro- and anti-angiogenic factors. As with many other tissues, vascular endothelial growth factor (VEGF) appears to be one of the major pro-angiogenic factors in the female reproductive organs. Pigment epithelium-derived factor (PEDF) is a non-inhibitory member of the serine protease inhibitors (serpin) superfamily, possessing potent physiologic anti-angiogenic activity that negates VEGF activity. The role of PEDF in decreasing abnormal neovascularization by exerting its anti-angiogenic effect that inhibits pro-angiogenic factors, including VEGF, has been investigated mainly in the eye and in cancer. This review summarizes the function of PEDF in the reproductive system, showing its hormonal regulation and its anti-angiogenic activity. Furthermore, some pathologies of the female reproductive organs, including endometriosis, ovarian hyperstimulation syndrome, polycystic ovary syndrome, and others, are associated with a faulty angiogenic process. This review illuminates the role of PEDF in their pathogenesis and treatment. Collectively, we can conclude that although PEDF seems to play an essential role in the physiology and pathophysiology of the reproductive system, its full role and mechanism of action still need to be elucidated.

Advanced glycation end products potentiate citrated plasma-evoked oxidative and inflammatory reactions in endothelial cells by up-regulating protease-activated receptor-1 expression

Advanced glycation end products (AGEs) and receptor RAGE interaction contribute to endothelial cell damage in diabetes. Several thrombogenic abnormalities are also involved in diabetic vascular complications. However, the pathological role of thrombin and protease-activated receptor-1 (PAR-1) system in AGE-induced endothelial cell (EC) damage remains unclear. In this study, we investigated the effects of rivaroxaban, an inhibitor of factor Xa on 3% citrated human plasma-evoked reactive oxygen species (ROS) generation and RAGE, monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule-1 (ICAM-1) gene expression in AGE-exposed ECs. We further examined whether FR171113, an inhibitor of PAR-1 blocked the plasma-induced EC damage and if AGEs increased PAR-1 expression in ECs. Human citrated plasma stimulated ROS generation and RAGE, MCP-1 and ICAM-1 expression in ECs, all of which were potentiated by the treatment with AGEs. Rivaroxaban or FR171113 significantly inhibited these derangements in plasma- or plasma plus AGE-exposed ECs. Moreover, AGEs significantly increased the PAR-1 levels in ECs. The present study suggests that citrated plasma could induce oxidative and inflammatory reactions in ECs via the activation of thrombin-PAR-1 system and that AGEs could potentiate the plasma-evoked EC damages via up-regulation of PAR-1. Blockade of the crosstalk between AGE-RAGE axis and coagulation system by rivaroxaban might be a novel therapeutic target for thromboembolic disorders in diabetes.

The association study of plasma levels of pigment epithelium-derived factor with acute coronary syndrome in the chinese han population

OBJECTS

To investigate the relationship between plasma levels of pigment epithelium-derived factor (PEDF) and acute coronary syndrome (ACS) in the Chinese Han population.

METHODS

Plasma PEDF levels were measured in 200 consecutive ACS patients and 160 age- and sex-matched healthy control subjects. Logistic regression analysis was performed to determine whether PEDF was an independently protective factor against ACS. All ACS patients were followed up for 6 months and the short-term major adverse cardiovascular events (MACE) were obtained: cardiac death and recurrent angina.

RESULTS

The ACS patients showed notably lower plasma PEDF levels relative to the control group (7.31 ± 2.21 vs. 8.44 ± 2.13 μg/ml, respectively, p = 0.001). Logistic regression analysis revealed that PEDF had a significant protective effect against ACS (OR = 0.76, 95% CI 0.623-0.935, p = 0.01). After 6 months of follow-up, we found that the mean PEDF concentration of the patients with short-term MACE was lower than the patients without (6.05 ± 2.18 vs. 7.52 ± 2.07 µg/ml, p = 0.031). The Kaplan-Meier survival curves suggested that patients with plasma PEDF levels <7.00 µg/ml showed a lower survival trend than those in the higher group, but the difference was not significant (p = 0.477).

CONCLUSIONS

Our study indicates that plasma PEDF levels are significantly lower in ACS patients than in controls, and lower PEDF levels are further associated with adverse cardiac outcomes after ACS.

Pigment epithelium-derived factor (PEDF) binds to caveolin-1 and inhibits the pro-inflammatory effects of caveolin-1 in endothelial cells

Pigment epithelium-derived factor (PEDF) exerts atheroprotective effects both in cell culture and animal models through its anti-oxidative and anti-inflammatory properties. Caveolin-1 (Cav), a major protein component of caveolae in endothelial cells (ECs), plays a role in the progression of atherosclerosis. However, effects of PEDF on Cav-exposed ECs remain unknown. In this study, we examined whether and how PEDF could inhibit the Cav-induced inflammatory and thrombogenic reactions in human umbilical vein ECs (HUVECs). Surface plasmon resonance revealed that PEDF bound to Cav at the dissociation constant of 7.36×10(-7) M. Further, one of the major Cav-interacting proteins in human serum was identified as PEDF by peptide mass fingerprinting analysis using BIAcore 1000 combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Exogenously added Cav was taken up into the membrane fraction of HUVECs and dose-dependently increased monocyte chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule-1 (VCAM-1) and plasminogen activator inhibitor-1 (PAI-1) mRNA levels, all of which were blocked by the simultaneous treatment with 10nM PEDF. Small interfering RNAs directed against Cav decreased endogenous Cav levels and suppressed gene expression of MCP-1, VCAM-1 and PAI-1 in HUVECs. This study indicates that PEDF binds to Cav and could block the inflammatory and thrombogenic reactions in Cav-exposed HUVECs. Our present study suggests that atheroprotective effects of PEDF might be partly ascribed to its Cav-interacting properties.

Nox4 and diabetic nephropathy: with a friend like this, who needs enemies?

Oxidative stress has been linked to the pathogenesis of diabetic nephropathy, a complication of diabetes in the kidney. NADPH oxidases of the Nox family are a major source of reactive oxygen species in the diabetic kidney and are critical mediators of redox signaling in glomerular and tubulointerstitial cells exposed to the diabetic milieu. Here, we present an overview of the current understanding of the roles of Nox catalytic and regulatory subunits in the processes that control mesangial cell, podocyte, and tubulointerstitial cell injury induced by hyperglycemia and other predominant factors enhanced in the diabetic milieu, including the renin-angiotensin system and transforming growth factor-β. The role of the Nox isoform Nox4 in the redox processes that alter renal biology in diabetes is highlighted.

Nox as a target for diabetic complications

Oxidative stress has been linked to the pathogenesis of the major complications of diabetes in the kidney, the heart, the eye or the vasculature. NADPH oxidases of the Nox family are a major source of ROS (reactive oxygen species) and are critical mediators of redox signalling in cells from different organs afflicted by the diabetic milieu. In the present review, we provide an overview of the current knowledge related to the understanding of the role of Nox in the processes that control cell injury induced by hyperglycaemia and other predominant factors enhanced in diabetes, including the renin–angiotensin system, TGF-β (transforming growth factor-β) and AGEs (advanced glycation end-products). These observations support a critical role for Nox homologues in diabetic complications and indicate that NADPH oxidases are an important therapeutic target. Therefore the design and development of small-molecule inhibitors that selectively block Nox oxidases appears to be a reasonable approach to prevent or retard the complications of diabetes in target organs. The bioefficacy of these agents in experimental animal models is also discussed in the present review.

The many facets of PEDF in drug discovery and disease: a diamond in the rough or split personality disorder?

INTRODUCTION

Pigment epithelium-derived factor (PEDF) was discovered as a neurotrophic factor secreted by retinal pigment epithelial cells. A decade later, it re-emerged as a powerful angiogenesis inhibitor guarding ocular function. Since then, significant advances were made identifying PEDF's mechanisms, targets and biomedical applications.

AREAS COVERED

The authors review several methodologies that have generated significant new information about the potential of PEDF as a drug. Furthermore, the authors review and discuss mechanistic and structure-function analyses combined with the functional mapping of active fragments, which have yielded several short bioactive PEDF peptides. Additionally, the authors present functional studies in knockout animals and human correlates that have provided important information about conditions amenable to PEDF-based therapies.

EXPERT OPINION

Through its four known receptors, PEDF causes a wide range of cellular events vitally important for the organism, which include survival and differentiation, migration and invasion, lipid metabolism and stem cell maintenance. These processes are deregulated in multiple pathological conditions, including cancer, metabolic and cardiovascular disease. PEDF has been successfully used in countless preclinical models of these conditions and human correlates suggest a wide utility of PEDF-based drugs. The most significant clinical application of PEDF, to date, is its potential therapeutic use for age-related macular degeneration. Moreover, PEDF-based gene therapy has advanced to early stage clinical trials. PEDF active fragments have been mapped and used to design short peptide mimetics conferring distinct functions of PEDF, which may address specific clinical problems and become prototype drugs.

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.

Angiotensin II stimulates superoxide production in the thick ascending limb by activating NOX4

Angiotensin II (ANG II) stimulates production of superoxide (O(2)(-)) by NADPH oxidase (NOX) in medullary thick ascending limbs (TALs). There are three isoforms of the catalytic subunit (NOX1, 2, and 4) known to be expressed in the kidney. We hypothesized that NOX2 mediates ANG II-induced O(2)(-) production by TALs. To test this, we measured NOX1, 2, and 4 mRNA and protein by RT-PCR and Western blot in TAL suspensions from rats and found three catalytic subunits expressed in the TAL. We measured O(2)(-) production using a lucigenin-based assay. To assess the contribution of NOX2, we measured ANG II-induced O(2)(-) production in wild-type and NOX2 knockout mice (KO). ANG II increased O(2)(-) production by 346 relative light units (RLU)/mg protein in the wild-type mice (n = 9; P < 0.0007 vs. control). In the knockout mice, ANG II increased O(2)(-) production by 290 RLU/mg protein (n = 9; P < 0.007 vs. control). This suggests that NOX2 does not contribute to ANG II-induced O(2)(-) production (P < 0.6 WT vs. KO). To test whether NOX4 mediates the effect of ANG II, we selectively decreased NOX4 expression in rats using an adenovirus that expresses NOX4 short hairpin (sh)RNA. Six to seven days after in vivo transduction of the kidney outer medulla, NOX4 mRNA was reduced by 77%, while NOX1 and NOX2 mRNA was unaffected. In control TALs, ANG II stimulated O(2)(-) production by 96%. In TALs transduced with NOX4 shRNA, ANG II-stimulated O(2)(-) production was not significantly different from the baseline. We concluded that NOX4 is the main catalytic isoform of NADPH oxidase that contributes to ANG II-stimulated O(2)(-) production by TALs.

Glucagon-like peptide-1 inhibits angiotensin II-induced mesangial cell damage via protein kinase A

There is a growing body of evidence that renin-angiotensin system plays a role in diabetic nephropathy. Recently, we have found that glucagon-like peptide-1 (GLP-1), one of the incretins, a gut hormone secreted from L cells in the intestine in response to food intake, inhibits advanced glycation end product-induced monocyte chemoattractant protein-1 gene expression in mesangial cells thorugh the interaction with the receptor of GLP-1. However, effects of GLP-1 on angiotensin II-exposed mesangial cells are unknown. This study investigated whether and how GLP-1 blocked the angiotensin II-induced mesangial cell damage in vitro. GLP-1 completely blocked the angiotensin II-induced superoxide generation, NF-κB activation, up-regulation of mRNA levels of intercellular adhesion molecule-1 and plasminogen activator inhibitor-1 in mesangial cells, all of which were prevented by the treatments with H-89, an inhibitor of protein kinase A. The present results demonstrated for the first time that GLP-1 blocked the angiotensin II-induced mesangial cell injury by inhibiting superoxide-mediated NF-κB activation via protein kinase C pathway. Our present study suggests that strategies to enhance the biological actions of GLP-1 may be a promising strategy for the treatment of diabetic nephropathy.

Role of pigment epithelium-derived factor in stem/progenitor cell-associated neovascularization

Pigment epithelium-derived factor (PEDF) was first identified in retinal pigment epithelium cells. It is an endogenously produced protein that is widely expressed throughout the human body such as in the eyes, liver, heart, and adipose tissue; it exhibits multiple and varied biological activities. PEDF is a multifunctional protein with antiangiogenic, antitumorigenic, antioxidant, anti-inflammatory, antithrombotic, neurotrophic, and neuroprotective properties. More recently, PEDF has been shown to be the most potent inhibitor of stem/progenitor cell-associated neovascularization. Neovascularization is a complex process regulated by a large, interacting network of molecules from stem/progenitor cells. PEDF is also involved in the pathogenesis of angiogenic eye disease, tumor growth, and cardiovascular disease. Novel antiangiogenic agents with tolerable side effects are desired for the treatment of patients with various diseases. Here, we review the value of PEDF as an important endogenous antiangiogenic molecule; we focus on the recently identified role of PEDF as a possible new target molecule to influence stem/progenitor cell-related neovascularization.

PEDF in diabetic retinopathy: a protective effect of oxidative stress

Diabetic retinopathy (DR) is a major cause of blindness in working age adults, and oxidative stress plays a vital role in the pathogenesis of DR. Pigment-epithelium-derived factor (PEDF), a multifunctional protein, has shown to inhibit the development of DR by accumulating evidence. This paper highlights the current understanding of probable mechanism about how PEDF blocks the deterioration of DR through its antioxidative properties and application prospects of PEDF as a novel therapeutic target in DR. Gene therapy of PEDF is becoming more and more acceptable and will widely be applied to the actual treatment in the near future.

Oxidases and peroxidases in cardiovascular and lung disease: new concepts in reactive oxygen species signaling

Reactive oxygen species (ROS) are involved in numerous physiological and pathophysiological responses. Increasing evidence implicates ROS as signaling molecules involved in the propagation of cellular pathways. The NADPH oxidase (Nox) family of enzymes is a major source of ROS in the cell and has been related to the progression of many diseases and even environmental toxicity. The complexity of this family's effects on cellular processes stems from the fact that there are seven members, each with unique tissue distribution, cellular localization, and expression. Nox proteins also differ in activation mechanisms and the major ROS detected as their product. To add to this complexity, mounting evidence suggests that other cellular oxidases or their products may be involved in Nox regulation. The overall redox and metabolic status of the cell, specifically the mitochondria, also has implications on ROS signaling. Signaling of such molecules as electrophilic fatty acids has an impact on many redox-sensitive pathologies and thus, as anti-inflammatory molecules, contributes to the complexity of ROS regulation. This review is based on the proceedings of a recent international Oxidase Signaling Symposium at the University of Pittsburgh's Vascular Medicine Institute and Department of Pharmacology and Chemical Biology and encompasses further interaction and discussion among the presenters.

Administration of pigment epithelium-derived factor inhibits left ventricular remodeling and improves cardiac function in rats with acute myocardial infarction

Oxidative stress and inflammation are involved in cardiac remodeling after acute myocardial infarction (AMI). We have found that pigment epithelium-derived factor (PEDF) inhibits vascular inflammation through its anti-oxidative properties. However, effects of PEDF on cardiac remodeling after AMI remain unknown. We investigated whether PEDF could inhibit left ventricular remodeling and improve cardiac function in rats with AMI. AMI was induced in 8-week-old Sprague-Dawley rats by ligation of the left ascending coronary artery. Rats were treated intravenously with vehicle or 10 μg PEDF/100 g b.wt. every day for up to 2 weeks after AMI. Each rat was followed until 16 weeks of age. PEDF levels in infarcted areas and serum were significantly decreased at 1 week after AMI and remained low during the observational periods. PEDF administration inhibited apoptotic cell death and oxidative stress generation around the infarcted areas at 2 and 8 weeks after AMI. Further, PEDF injection suppressed cardiac fibrosis by reducing transforming growth factor-β and type III collagen expression, improved left ventricular ejection fraction, ameliorated diastolic dysfunction, and inhibited the increase in left ventricular mass index at 8 weeks after AMI. The present study demonstrated that PEDF could inhibit tissue remodeling and improve cardiac function in AMI rats. Substitution of PEDF may be a novel therapeutic strategy for cardiac remodeling after AMI.

Identification of a novel inhibitor of the canonical Wnt pathway

Wnt signaling is known to regulate multiple processes including angiogenesis, inflammation, and fibrosis. Here, we identified a novel inhibitor of the Wnt pathway, pigment epithelium-derived factor (PEDF), a multifunctional serine proteinase inhibitor. Both overexpression of PEDF in transgenic mice and administration of PEDF protein attenuated Wnt signaling induced by retinal ischemia. Furthermore, PEDF knockdown by small interfering RNA (siRNA) and PEDF knockout in PEDF(-/-) mice induced activation of Wnt signaling. PEDF bound to LRP6, a Wnt coreceptor, with high affinity (K(d) [dissociation constant] of 3.7 nM) and blocked the Wnt signaling induced by Wnt ligand. The physical interaction of PEDF with LRP6 was confirmed by a coprecipitation assay, which showed that PEDF bound to LRP6 at the E1E2 domain. In addition, binding of PEDF to LRP6 blocked Wnt ligand-induced LRP6-Frizzled receptor dimerization, an essential step in Wnt signaling. These results suggest that PEDF is an endogenous antagonist of LRP6, and blocking Wnt signaling may represent a novel mechanism for its protective effects against diabetic retinopathy.

Significance of pigment epithelium-derived factor levels with angiotensin II type 1 receptor blockers in patients with successful coronary stent implantation

Pigment epithelium-derived factor (PEDF) and pentosidine have received growing attention as sensitive biomarkers of the progression of atherosclerosis. The present study was performed to evaluate the utility of these biomarkers for assessing the effects of angiotensin II type 1 receptor blockers (ARBs). Sixty-three patients with coronary artery disease (CAD) following successful stent implantation were divided into an ARB group (n = 50), who initially received valsartan or olmesartan immediately following stent implantation, and a non-ARB group (n = 13) according to their blood pressure (BP) at baseline. Measurement of BP and blood sampling was performed prior to (at baseline) and 6-8 months following stent implantation (at follow-up). There were no significant differences in the baseline characteristics between the groups. Although there were no differences in the percentage of diameter re-stenosis between the groups, the BP level in the ARB group at follow-up showed a significant reduction and reached the target BP. The levels of plasma PEDF were significantly increased at follow-up in the ARB group, but not in the non-ARB group, while there were no differences in the levels of pentosidine between the groups. Changes in BP (ΔBP = BP at follow-up minus BP at baseline) were not associated with ΔPEDF. In conclusion, PEDF may be a useful biomarker for assessing the effects of ARBs independent of a reduction in BP.

Myofibroblast differentiation during fibrosis: role of NAD(P)H oxidases

Progression of fibrosis involves interstitial hypercellularity, matrix accumulation, and atrophy of epithelial structures, resulting in loss of normal function and ultimately organ failure. There is common agreement that the fibroblast/myofibroblast is the cell type most responsible for interstitial matrix accumulation and consequent structural deformations associated with fibrosis. During wound healing and progressive fibrotic events, fibroblasts transform into myofibroblasts acquiring smooth muscle features, most notably the expression of alpha-smooth muscle actin and synthesis of mesenchymal cell-related matrix proteins. In renal disease, glomerular mesangial cells also acquire a myofibroblast phenotype and synthesize the same matrix proteins. The origin of interstitial myofibroblasts during fibrosis is a matter of debate, where the cells are proposed to derive from resident fibroblasts, pericytes, perivascular adventitial, epithelial, and/or endothelial sources. Regardless of the origin of the cells, transforming growth factor-beta1 (TGF-β1) is the principal growth factor responsible for myofibroblast differentiation to a profibrotic phenotype and exerts its effects via Smad signaling pathways involving mitogen-activated protein kinase and Akt/protein kinase B. Additionally, reactive oxygen species (ROS) have important roles in progression of fibrosis. ROS are derived from a variety of enzyme sources, of which the nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase family has been identified as a major source of superoxide and hydrogen peroxide generation in the cardiovasculature and kidney during health and disease. Recent evidence indicates that the NAD(P)H oxidase homolog Nox4 is most accountable for ROS-induced fibroblast and mesangial cell activation, where it has an essential role in TGF-β1 signaling of fibroblast activation and differentiation into a profibrotic myofibroblast phenotype and matrix production. Information on the role of ROS in mesangial cell and fibroblast signaling is incomplete, and further research on myofibroblast differentiation during fibrosis is warranted.

Novel Nox homologues in the vasculature: focusing on Nox4 and Nox5

The Noxes (NADPH oxidases) are a family of ROS (reactive oxygen species)-generating enzymes. Of the seven family members, four have been identified as important sources of ROS in the vasculature: Nox1, Nox2, Nox4 and Nox5. Although Nox isoforms can be influenced by the same stimulus and co-localize in cellular compartments, their tissue distribution, subcellular regulation, requirement for cofactors and NADPH oxidase subunits and ability to generate specific ROS differ, which may help to understand the multiplicity of biological functions of these oxidases. Nox4 and Nox5 are the newest isoforms identified in the vasculature. Nox4 is the major isoform expressed in renal cells and appear to produce primarily H2O2. The Nox5 isoform produces ROS in response to increased levels of intracellular Ca2+ and does not require the other NADPH oxidase subunits for its activation. The present review focuses on these unique Noxes, Nox4 and Nox5, and provides novel concepts related to the regulation and interaction in the vasculature, and discusses new potential roles for these isoforms in vascular biology.