Function Of Pigment Epithelium-derived Factor Research Articles

Expression Patterns and Functions of Cardiac Pigment Epithelium-Derived Factor During Cardiac Development

Objective: This study describes the expression profiles and roles of cardiac pigment epithelium-derived factor (PEDF) during cardiac development. Methods: Gene datasets from the Gene Expression Omnibus (GEO) database were used to analyze the correlation between cardiac PEDF expression and heart disease. Western blotting, immunohistochemistry, histological staining and echocardiography were used to assess the expression patterns and functions of PEDF during cardiac development. Results: Analysis of GEO data sets indicated that the expression of cardiac PEDF correlated with the occurrence and development of various heart diseases. Western blotting of various tissues in mice at 30 postnatal days of age indicated higher PEDF expression in the heart and aorta than the liver. Immunohistochemical results demonstrated that the expression of cardiac PEDF significantly decreased after birth, mainly because of a significant decrease in PEDF expression in the cytoplasm. Histological staining and echocardiography indicated that PEDF deficiency had no significant effects on cardiac structure, cardiac function and vascular hemodynamics in 8-week-old mice. Conclusion: Cardiac PEDF shows high expression and dynamic changes during cardiac development, but has no effects on cardiac structure, function and vascular hemodynamics.

PEDF protects human retinal pigment epithelial cells against oxidative stress via upregulation of UCP2 expression.

To investigate the protective function of pigment epithelium-derived factor (PEDF) against oxidative stress (OS) in ARPE-19 cells, ARPE-19 cells were divided into different OS groups and treated with various concentrations of H2O2 (0, 75, 150 and 200 µmol/l) for 24 h. To establish the protective group, 200 ng/ml of PEDF was administered to ARPE-19 cells. Cell Counting Kit-8 assays and cell growth curve experiments were performed to determine levels of cell viability; lactate dehydrogenase and propidium iodide (PI) staining assays were also performed. The expression levels of genes associated with apoptosis as well as uncoupling protein 2 (UCP2) were detected by reverse transcription-quantitative, or semi-quantitative polymerase chain reaction. Furthermore, an OS injury animal model was established in both C57BL/6 and BALB/c mice via injection of 5 µg of PEDF in the vitreous cavity and subsequent injection of 150 µM H2O2 following a 24 h time interval. Hematoxylin and eosin (H&E) staining, as well as UCP2 immunofluorescent labeling were also performed. One-way analysis of variance was used to determine statistically significant differences, followed by multiple comparison analysis using the Newman Keuls method. The results of cell viability assays demonstrated that the numbers of apoptotic cells were increased following treatment with H2O2 in a dose-dependent manner; however, this effect was reversed following treatment with PEDF. The expression levels of caspase 3 and B cell lymphoma (Bcl2) associated X genes associated with apoptosis were inhibited, whereas levels of the anti-apoptotic gene Bcl2 were enhanced following treatment with PEDF in different passages of ARPE-19 cells. Significant differences were demonstrated in the levels of UCP2 gene expression between the PEDF+ H2O2 treated group and cells treated with H2O2 alone. Labeling of the UCP2 detector in the confocal images demonstrated decreased UCP2 protein staining in the retinal pigment epithelium (RPE) cells and RPE layers following H2O2 injury; however, this effect was inhibited following treatment with PEDF. H&E staining was performed to investigate the thickness of the RPE layers, and the results revealed that thicknesses were significantly increased in sections treated with PEDF during OS, due to increased numbers of RPE cells. Furthermore, PEDF was demonstrated to increase UCP2 gene expression in ARPE-19 cells and animal RPE layers under OS, which suggested that PEDF may protect RPE cells and tissues during oxidative injury.

Study of Pigment Epithelium-derived Factor in Pathogenesis of Diabetic Retinopathy.

Diabetic retinopathy (DR), a major microvascular complication of diabetes, has emerged as a leading cause of visual impairment and blindness among adults worldwide. However, aside from pathological damage, the traditional laser and multi-needle operation treatments required for more advanced disease can cause further damage to the visual field and increase the operation risk. Therefore, the development of new therapeutic strategies for the prevention and treatment of DR is essential. Some emerging evidence now indicates that pigment epithelium-derived factor (PEDF), a multifunctional protein, can target multiple pathways to exert neurotropic, neuropro- tective, anti-angiogenic, anti-vasopermeability, anti-inflammation, anti-thrombogenic, and anti-oxidative effects against DR. This review addresses the functions of PEDF in different pathways that could lead to potential therapeutics for the treatment of DR.

Intracellular pigment epithelium-derived factor contributes to triglyceride degradation

Pigment epithelium-derived factor is well known as a secreted glycoprotein with multiple functions, such as anti-angiogenic, neuroprotective and anti-tumor activities. However, its intracellular role remains unknown. The present study was performed to demonstrate the intracellular function of pigment epithelium-derived factor on triglyceride degradation. Hepatic pigment epithelium-derived factor levels increased at the early stage and subsequently decreased after 16 weeks in high-fat-diet-fed mice compared to those in chow-fed mice. Similarly, oleic acid led to long-term downregulation of pigment epithelium-derived factor in HepG2 cells. Endogenous pigment epithelium-derived factor was an intracellular protein with cytoplasmic distribution in hepatocytes by immunostaining. Exogenous FITC-labeled pigment epithelium-derived factor could be absorbed into hepatocytes. Both signal peptide deletion and full-length pigment epithelium-derived factor transfection HeLa cells and hepatocytes promoted triglyceride degradation. Intracellular pigment epithelium-derived factor co-immunoprecipitated with adipose triglyceride lipase and promoted triglyceride degradation in an adipose triglyceride lipase-dependent manner. Additionally, pigment epithelium-derived factor bound to the C-terminal of adipose triglyceride lipase (aa268–504) and adipose triglyceride lipase-G0/G1 switch gene-2 complex simultaneously, which facilitated adipose triglyceride lipase-G0/G1 switch gene-2 translocation onto lipid droplet using bimolecular fluorescence complementation assay. Moreover, knockdown of endogenous pigment epithelium-derived factor in hepatocytes diminished triglyceride degradation. Taken together, these results indicate that hepatic pigment epithelium-derived factor was decreased in obese mice accompanied with hepatic steatosis. Intracellular pigment epithelium-derived factor binds to and facilitates adipose triglyceride lipase translocation onto lipid droplet, which promotes triglyceride degradation. These findings suggest that a decreased level of hepatic pigment epithelium-derived factor may contribute to hepatic steatosis in obesity.

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.

Abstract 1523: Trafficking of intracytoplasmic lipid droplets in pancreatic cancer cells by pigment epithelium-derived factor alters triacylglycerol metabolism and cellular invasion

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is a rapidly progressing disease with high metastatic potential, thus, it requires a robust and renewable source of energy to meet its metabolic demands. High grade PDAC tumors have been shown to lose expression of a potent negative regulator of lipid metabolism, pigment epithelium-derived factor (PEDF). Emerging data support that lipid droplets (LDs) are dynamic organelles in non-adipocytes and they are capable of participating in signaling pathways and as well as providing a source of energy. LDs are composed of a triacylglycerol (TAG) core covered by coat proteins, some of which assist in restricting lipase activity by enzymes such as adipose triglyceride lipase (ATGL). Based on a study of adipose differentiation related protein (ADRP) over expression resulting in lower metalloproteinase (MMP) levels in non-tumor cells, we proposed that ADRP-positive LDs actively participate in cellular invasion. We further postulated that expression of PEDF in PDAC tumors inhibits cellular invasion and reduces lipid energy stores due to an increase in ATGL-mediated TAG catabolism and redistribution of intracytoplasmic LDs. Methods: PANC-1 cells were transfected with the PEDF gene via the pCEP4 vector. PEDF-expressing PANC-1 cells, wild type controls and human pancreatic tumor tissue sections were immunostained for PEDF, ATGL, neutral lipid (Oil-red-O) and the two LD coat proteins, ADRP and tail interacting protein-47 (TIP-47). LD distribution (perinuclear vs. peripheral) was analyzed and matrigel cell invasion assays were performed. To determine the role of LDs in proliferation, TAG synthesis in PANC-1 cells was blocked using a diacylglycerol acyltransferase-1 (DGAT-1) inhibitor. Results: PEDF-expressing PANC-1 cells revealed a 10-fold decrease in cellular invasion and an increase in ATGL expression. Immunostains for LD coat proteins, ADRP and TIP-47, showed a predominantly perinuclear position for LDs in the wild type control cells, whereas, PEDF-expressing cells exhibited more ADRP positive LDs in the peripheral region of the cytoplasm. The LDs located closest to the nucleus had the largest mean diameter. Human PDAC tissue had minimal to no expression of PEDF and exhibited predominantly larger perinuclear LDs with more intense TIP-47 staining as compared to ARDP. Blockade of TAG synthesis with DGAT-1 inhibitor reduced LD size and significantly decreased cellular proliferation. Conclusions: These data suggest that activation of TAG catabolism in PDAC by upregulation of the lipolytic enzyme, ATGL, or blockade of TAG synthesis by a DGAT-1 inhibitor diminishes LD size. Moreover, redistribution of LDs and changes in LD coat protein expression may be one mechanism underlying the anti-invasive function of PEDF in PANC-1 cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1523. doi:1538-7445.AM2012-1523

PEDF - A Noninhibitory Serpin with Neurotrophic Activity

The pigment epithelium-derived factor (PEDF) is a glycoprotein with a molecular weight of 50 kDa belonging to the noninhibitory serpin family. It regulates several physiological processes, such as stimulation of retinoblastoma cell differentiation into neuron cells, and facilitation of the growth and viability of photoreceptor cells and neurons of the central nervous system. Moreover, this factor protects neuronal cells against apoptosis. PEDF is not only a neurotrophic factor, but also a natural angiogenesis inhibitor. This protein, as well as its biologically active fragments, possesses significant neuroprotective, neurotrophic, and antiangiogenic capabilities. The precise molecular mechanisms underpinning the effects of PEDF are still not quite clear. However, this protein generates great interest as a promising drug for the therapy of a wide range of neurodegenerative, ophthalmological, and oncological diseases. This review is a summary of what is known today about the structural features, biochemical properties, and multimodal functions of PEDF.

The Pathophysiological Role of PEDF in Bone Diseases

First discovered in 1991 as a factor secreted by retinal pigment epithelial cells, the potency of pigment epithelium derived factor (PEDF) as an anti-angiogenic has led to examination of its role in active bone growth, repair and remodelling. In the musculoskeletal system, PEDF expression occurs particularly at sites of active bone formation. Expression has been noted in osteoblasts and to a lesser degree osteoclasts, the major classes of bone cells. In fact, PEDF is capable of inducing differentiation of precursor cells into mature osteoblasts. Expression and localisation are closely linked with that of vascular endothelial growth factor (VEGF). Studies at the epiphyseal plate have revealed that PEDF expression plays a key role in endochondral ossification, and beyond this may account for the epiphyseal plate's innate ability to resist neoplastic cell invasion. Collagen-1, the major protein in bone, is avidly bound by PEDF, implicating an important role played by this protein on PEDF function, possibly through MMP-2 and -9 activity. Surprisingly, the role of PEDF has not been evaluated more widely in bone disorders, so the challenge ahead lies in a more diverse evaluation of PEDF in various osteologic pathologies including osteoarthritis and fracture healing.

Changes in pigment epithelium-derived factor expression following kainic acid induced cerebellar lesion in rat

Pigment epithelium-derived factor (PEDF) is a potent and broad-acting neurotrophic factor that protects various types of cultured neurons against glutamate excitotoxicity and induced apoptosis. The expression pattern and functions of PEDF in the central nervous system (CNS) remain largely undetermined. In this study, we analyzed the spatial and temporal expression of PEDF in normal and kainic acid (KA)-induced lesioned rat cerebellum using immunoblotting, immunohistochemistry and fluorescent in situ hybridization techniques. In normal rat cerebellum, PEDF protein and mRNA were mostly confined and co-localized with calbindin-positive cells in the Purkinje cell layer of the cerebellum, but not with glial fibrillary acidic protein (GFAP)-, 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase)-, and isolectin B4-positive cells. Injection of KA into the right cellebellum caused severe loss of calbindin-positive Purkinje neurons, and an increased number of GFAP-positive astrocytes and isolectin B4-positive microglia was observed on the ipsilateral side of the lesioned cerebellum. Although the PEDF level on the ipsilateral side of the cerebellum was dramatically decreased 2 days after KA treatment, significantly elevation of PEDF levels was observed at 7 days. In agreement with these results, PEDF protein and PEDF mRNA expression were co-localized with GFAP-positive reactive astrocytes in the ipsilateral side 7 days after KA treatment. Although the mechanism by which PEDF is induced in reactive astrocytes remains unclear, the increase in PEDF expression in injured brain may form part of a compensation mechanism against neuronal degeneration.

Decreased Expression of Pigment Epithelium-Derived Factor Is Involved in the Pathogenesis of Diabetic Nephropathy

Pigment epithelium-derived factor (PEDF) is a potent angiogenic inhibitor. Previous studies have shown that decreased ocular levels of PEDF are associated with diabetic retinopathy. However, the implication of PEDF expression in diabetic nephropathy has not been revealed. In the present study, we demonstrated for the first time that the expression of PEDF was decreased at both the mRNA and protein levels in the kidney of diabetic rats, whereas transforming growth factor-beta (TGF-beta) and fibronectin levels were increased in the same diabetic kidneys. As shown by immunohistochemistry, the decrease of PEDF expression occurs primarily in the glomeruli. In vitro studies showed that high concentrations of glucose significantly decreased PEDF secretion in primary human glomerular mesangial cells (HMCs), suggesting that hyperglycemia is a direct cause of the PEDF decrease in the kidney. Toward the function of PEDF, we showed that PEDF blocked the high-glucose-induced overexpression of TGF-beta, a major pathogenic factor in diabetic nephropathy, and fibronectin in primary HMCs, suggesting that PEDF may function as an endogenous inhibitor of TGF-beta expression and fibronectin production in glomeruli. Therefore, decreased expression of PEDF in diabetic kidneys may contribute to extracellular matrix overproduction and the development of diabetic nephropathy.

PEDF: a multifaceted neurotrophic factor.

Pigment epithelium-derived factor (PEDF) is a potent and broadly acting neurotrophic factor that protects neurons in many regions of the central nervous system against insults such as glutamate excitotoxicity and oxidative damage. Since the crystal structure of PEDF was solved, its biological actions have begun to be mapped to specific structural domains. Here we discuss the structure and function of PEDF and the biochemical pathways it activates, and suggest ways in which this molecule might become a valuable therapeutic agent.