Yumiko Yoshida

Pigment epithelium-derived factor inhibits advanced glycation end product-induced retinal vascular hyperpermeability by blocking reactive oxygen species-mediated vascular endothelial growth factor expression

Pigment epithelium-derived factor (PEDF) is the most potent inhibitor of angiogenesis, suggesting that loss of PEDF contributes to proliferative diabetic retinopathy. However, the role of PEDF against retinal vascular hyperpermeability remains to be elucidated. We investigated here whether and how PEDF could inhibit the advanced glycation end product (AGE) signaling to vascular hyperpermeability. Intravenous administration of AGEs to normal rats not only increased retinal vascular permeability by stimulating vascular endothelial growth factor (VEGF) expression but also decreased retinal PEDF levels. Simultaneous treatments with PEDF inhibited the AGE-elicited VEGF-mediated permeability by down-regulating mRNA levels of p22phox and gp91phox, membrane components of NADPH oxidase, and subsequently decreasing retinal levels of an oxidative stress marker, 8-hydroxydeoxyguanosine. PEDF also inhibited the AGE-induced vascular hyperpermeability evaluated by transendothelial electrical resistance by suppressing VEGF expression. Furthermore, PEDF decreased reactive oxygen species (ROS) generation in AGE-exposed endothelial cells by suppressing NADPH oxidase activity via down-regulation of mRNA levels of p22PHOX and gp91PHOX. This led to blockade of the AGE-elicited Ras activation and NF-κB-dependent VEGF gene induction in endothelial cells. These results indicate that the central mechanism for PEDF inhibition of the AGE signaling to vascular permeability is by suppression of NADPH oxidase-mediated ROS generation and subsequent VEGF expression. Substitution of PEDF may offer a promising strategy for halting the development of diabetic retinopathy.

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

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.

Pigment epithelium-derived factor (PEDF) inhibits proximal tubular cell injury in early diabetic nephropathy by suppressing advanced glycation end products (AGEs)-receptor (RAGE) axis

Pigment epithelium-derived factor (PEDF) is a multifunctional glycoprotein with anti-angiogenic and anti-inflammatory properties, and it could block the development and progression of experimental diabetic retinopathy. However, a role for PEDF in early experimental diabetic nephropathy is not fully understood. Advanced glycation end products (AGEs) and their receptor (RAGE) axis stimulates oxidative stress generation and subsequently evokes inflammatory and fibrogenic reactions in renal tubular cells, thereby playing a role in diabetic nephropathy. Therefore, this study investigated whether PEDF could prevent AGE-elicited tubular cell injury in early diabetic nephropathy. Human proximal tubular cells were incubated with or without AGE-bovine serum albumin in the presence or absence of PEDF. Streptozotocin-induced diabetic rats were treated with or without intravenous injection of PEDF for 4 weeks. Gene expression was analyzed by quantitative real-time reverse transcription-polymerase chain reactions. Reactive oxygen species (ROS) was measured with dihydroethidium staining. PEDF or antibodies raised against RAGE inhibited the AGE-induced RAGE gene expression and subsequently reduced ROS generation, monocyte chemoattractant protein-1 (MCP-1) and transforming growth factor-β (TGF-β), fibronectin and type IV collagen mRNA levels in proximal tubular cells. RAGE gene expression, ROS generation and MCP-1 and TGF-β mRNA levels were significantly increased in diabetic kidney, which were suppressed by administration of PEDF. Our present data suggest that PEDF could play a protective role against tubular injury in diabetic nephropathy by attenuating the deleterious effects of AGEs via down-regulation of RAGE expression. Administration of PEDF may offer a promising strategy for halting the development of diabetic nephropathy.

Pigment-epithelium-derived factor suppresses expression of receptor for advanced glycation end products in the eye of diabetic rats.

The interaction of advanced glycation end products (AGEs) and their receptor (RAGE) elicits inflammatory and proliferative responses in retinal vascular wall cells, thereby being involved in the pathogenesis of diabetic retinopathy. Recently, pigment-epithelium-derived factor (PEDF) has also been shown to play a role in diabetic retinopathy. However, the effects of PEDF on RAGE gene expression remain to be elucidated. Therefore, we investigated here whether PEDF could prevent diabetes- or AGE-induced RAGE gene expression and the way that it might achieve this effect. Administration of PEDF or pyridoxal phosphate, an AGE inhibitor, suppressed RAGE gene expression in the eye of streptozotocin-induced diabetic rats. Further, intravenous injection of AGEs to normal rats increased RAGE gene expression, which was also blocked by PEDF. In vitro, PEDF or an antioxidant N-acetylcysteine blocked the AGE-induced RAGE gene induction in microvascular endothelial cells. In addition, PEDF completely inhibited superoxide generation and NF-ĸB activation in AGE-exposed endothelial cells. These results demonstrated that PEDF could inhibit diabetes- or AGE-induced RAGE gene expression by blocking the superoxide-mediated NF-ĸB activation. Our present study suggests that pharmacological upregulation or substitution of PEDF may play a protective role against diabetic retinopathy by attenuating the deleterious effect of AGEs.

Positive association of pigment epithelium-derived factor with total antioxidant capacity in the vitreous fluid of patients with proliferative diabetic retinopathy

Background: Pigment epithelium-derived factor (PEDF), a glycoprotein with potent neuronal differentiating activity, was recently found to inhibit advanced glycation end product (AGE)-induced retinal hyperpermeability and angiogenesis through its antioxidative properties, suggesting that it may exert beneficial effects on diabetic retinopathy by acting as an endogenous antioxidant. However, the inter-relationship between PEDF and total antioxidant capacity in the eye remains to be elucidated. Aims: To determine vitreous PEDF and total antioxidant levels in patients with proliferative diabetic retinopathy (PDR), and to investigate the relationship between them. Methods: Vitreous levels of PEDF and total antioxidant capacity were measured by an ELISA in 39 eyes of 36 patients with diabetes and PDR and in 29 eyes of 29 controls without diabetes. Results: Vitreous levels of total antioxidant capacity were significantly lower in patients with diabetes and PDR than in controls (mean (SD) 0.16 (0.05) vs 0.24 (0.09) mmol/l, respectively, p<0.001). PEDF levels correlated positively with total antioxidant status in the vitreous of patients with PDR (r = 0.37, p<0.05) and in controls (r = 0.41, p<0.05). Further, vitreous levels of PEDF in patients with PDR without vitreous haemorrhage (VH(−)) were significantly (p<0.05) decreased, compared with those in the controls or in patients with PDR with vitreous haemorrhage (VH(+); PDR VH(−), 4.5 (1.1) μg/ml; control, 7.4 (4.1) μg/ml; PDR VH(+) 8.5 (3.6) μg/ml). Conclusion: This study demonstrates that PEDF levels are associated with total antioxidant capacity of vitreous fluid in humans, and suggests that PEDF may act as an endogenous antioxidant in the eye and could play a protective role against PDR.

Positive correlation of pigment epithelium-derived factor and total antioxidant capacity in aqueous humour of patients with uveitis and proliferative diabetic retinopathy

Background/aims: There are several animal studies to suggest that pigment epithelium-derived factor (PEDF) may exert beneficial effects on diabetic retinopathy and uveitis by acting as an endogenous antioxidant. However, the interrelationship between PEDF and total antioxidant capacity in the human eye remains to be elucidated. In this study, PEDF and total antioxidant levels were determined in the aqueous humour of patients with proliferative diabetic retinopathy (PDR) and uveitis, and the relationship between these two markers was investigated. Methods: Aqueous humour levels of PEDF and total antioxidant capacity were determined by an ELISA system in 34 uveitis and 9 PDR samples. Results: Aqueous humour levels of PEDF and total antioxidant capacity were significantly lower in patients with PDR than those with uveitis (1.8±0.2 &mgr;g/ml vs 6.4±0.8 &mgr;g/ml and 0.17±0.03 mmol/l vs 0.85±0.05 mmol/l, respectively, p<0.01). A positive correlation between PEDF and total antioxidant capacity was found in patients with PDR and uveitis (r = 0.33, p<0.05). Conclusion: This study demonstrated that PEDF levels were associated with total antioxidant capacity in aqueous humour levels in humans. These observations suggest that substitution of PEDF may be a therapeutic target for oxidative stress-involved eye diseases, especially PDR.

Administration of pigment epithelium-derived factor (PEDF) inhibits cold injury-induced brain edema in mice

Brain edema is the most life-threatening complication that occurs as a result of a number of insults to the brain. However, its therapeutic options are insufficiently effective. We have recently found that administration of pigment epithelium-derived factor (PEDF) inhibits retinal hyperpermeability in rats by counteracting biological effects of vascular endothelial growth factor (VEGF). In this study, we investigated whether PEDF could inhibit cold injury-induced brain edema in mice. Cold injury was induced by applying a pre-cooled metal probe on the parietal skull. VEGF and its receptor Flk-1 gene and/or protein expressions were up-regulated in the cold-injured brain. Cold injury induced brain edema, which was reduced by intraperitoneal injection of VEGF antibodies (Abs) or apocynin, an inhibitor of NADPH oxidase. PEDF mRNA and protein levels were up-regulated in response to cold injury. PEDF dose-dependently inhibited the brain edema, whose effect was neutralized by simultaneous treatments with anti-PEDF Abs. Although VEGF and Flk-1 gene and/or protein expressions were not suppressed by PEDF, PEDF or anti-VEGF Abs inhibited the cold injury-induced NADPH oxidase activity in the brain. Further, PEDF treatment inhibited activation of Rac-1, an essential component of NADPH oxidase in the cold-injured brain, while it did not affect mRNA levels of gp91phox, p22phox, or Rac-1. These results demonstrate that PEDF could inhibit the cold injury-induced brain edema by blocking the VEGF signaling to hyperpermeability through the suppression of NADPH oxidase via inhibition of Rac-1 activation. Our present study suggests that PEDF may be a novel therapeutic agent for the treatment of brain edema.

Positive correlation between vitreous levels of advanced glycation end products and vascular endothelial growth factor in patients with diabetic retinopathy sufficiently treated with photocoagulation.

We investigated whether vitreous levels of advanced glycation end products (AGEs) were positively correlated with vascular endothelial growth factor (VEGF) in patients with diabetic retinopathy patients sufficiently treated with retinal photocoagulation. Vitreous AGE and VEGF levels were significantly higher in patients with diabetes than in controls. Positive correlation between AGE and VEGF was found in patients with diabetic retinopathy sufficiently treated with retinal photocoagulation (r = 0.44, p<0.05), but not in those who were insufficiently treated (r = 0.26, p = 0.18). The present observations suggest that AGE may induce VEGF expression in an ischaemia-independent mechanism. AGE could be one of the important determinants of VEGF in diabetic retinopathy without obvious ischaemic regions. Vascular endothelial growth factor (VEGF) elicits retinal vascular hyperpermeability, thrombosis and angiogenesis, having a central role in the pathogenesis of diabetic retinopathy.1 Furthermore, vitreous VEGF levels are increased in proliferative diabetic retinopathy, whereas the levels are decreased after treatment with …

Positive correlation between pigment epithelium-derived factor and monocyte chemoattractant protein-1 levels in the aqueous humour of patients with uveitis

Aim: To evaluate whether aqueous humour levels of pigment epithelium-derived factor (PEDF) are associated with monocyte chemoattractant protein-1 (MCP-1) in patients with uveitis. Methods: Aqueous humour levels of MCP-1 and PEDF were determined by ELISA in 34 uveitis samples and 9 cataract control samples. Results: Aqueous humour MCP-1 and PEDF levels were significantly higher in patients with infectious or non-infectious uveitis than in controls (mean (SD) 32.3 (10.7) ng/ml vs 4.48 (1.10) ng/ml vs 0.47 (0.10) ng/ml, and 8.40 (1.30) μg/ml vs 5.01 (0.92) μg/ml vs 1.32 (0.22) μg/ml, respectively, p<0.001). A positive correlation between PEDF and MCP-1 was found in patients with uveitis (r = 0.39, p<0.01). Conclusion: The results demonstrated that aqueous humour levels of PEDF were positively associated with MCP-1 in patients with uveitis. The present observations suggest that aqueous humour levels of PEDF may be a marker of inflammation in uveitis.

Aqueous humor levels of asymmetric dimethylarginine (ADMA) are positively associated with monocyte chemoattractant protein-1 (MCP-1) in patients with uveitis

Background/aims: The aim of the study was to evaluate whether aqueous humor levels of asymmetric dimethylarginine (ADMA) are associated with monocyte chemoattractant protein-1 (MCP-1). Methods: Aqueous humor levels of ADMA and MCP-1 were measured by high-performance liquid chromatography (HPLC) and ELISA, respectively, in 31 uveitis samples and nine cataract control samples. Results: Aqueous humor ADMA and MCP-1 levels were significantly higher in infectious or non-infectious uveitis patients than in controls (0.67±0.04 nmol/ml vs 0.55±0.03 nmol/ml vs 0.43±0. 04 nmol/ml (p<0.01) and 29.0±11.3 ng/ml vs 4.5±1.2 ng/ml vs 0.47±0.1 ng/ml (p<0.01), respectively). A positive correlation between ADMA and MCP-1 levels in aqueous humor was found in control and uveitis patients (r = 0.33, p<0.05). Conclusion: The results demonstrated that aqueous humor levels of ADMA were positively associated with MCP-1 in humans. Our present observations suggest that aqueous humor levels of ADMA may be a novel biomarker of inflammation in uveitis.