Diabetic Retina (diabetic + retina)

Distribution by Scientific Domains


Selected Abstracts


Vascular endothelial growth factor and diabetic retinopathy: pathophysiological mechanisms and treatment perspectives

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 6 2003
Ruth B. Caldwell
Abstract Retinal neovascularization and macular edema are central features of diabetic retinopathy, the major cause of blindness in the developed world. Current treatments are limited in their efficacy and are associated with significant adverse effects. Characterization of the molecular and cellular processes involved in vascular growth and permeability has led to the recognition that the angiogenic growth factor and vascular permeability factor vascular endothelial growth factor (VEGF) plays a pivotal role in the retinal microvascular complications of diabetes. Therefore, VEGF represents an exciting target for therapeutic intervention in diabetic retinopathy. This review highlights the current understanding of the mechanisms that regulate VEGF gene expression and mediate its biological effects and how these processes may become altered during diabetes. The cellular and molecular alterations that characterize experimental models of diabetes are considered in relation to the influence of high glucose-mediated oxidative stress on VEGF expression and on the mechanisms of VEGF's actions under hyperglycemic induction. Finally, potential therapeutic strategies for preventing VEGF overexpression or blocking its pathological effects in the diabetic retina are considered. Copyright 2003 John Wiley & Sons, Ltd. [source]


Arteriolar Involvement in the Microvascular Lesions of Diabetic Retinopathy: Implications for Pathogenesis

MICROCIRCULATION, Issue 1 2007
TOM A. GARDINER
ABSTRACT Diabetic retinopathy (DR) is the most widespread complication of diabetes mellitus and a major cause of blindness in the working population of developed countries. The clinicopathology of the diabetic retina has been extensively studied, although the relative contribution of the various biochemical and molecular sequelae of hyperglycemia remains ill defined. Many neural and microvascular abnormalities occur in the retina of short-term diabetic animals but it remains uncertain how closely these acute changes relate to chronic human disease. It is important to determine the relationship between alterations observed within the first weeks or months in short-term animal models, and human disease, where clinically manifest retinopathy occurs only after durations of diabetes measured in years. This review is focused on the retinal microvasculature, although it should be appreciated that pathological changes in this system often occur in parallel with abnormalities in the neural parenchyma that may be derivative or even causal. Nevertheless, it is useful to reevaluate the microvascular lesions that are manifest in the retina during diabetes in humans and long-term animal models, since in addition to providing useful clues to the pathogenic basis of DR as a disease entity, it is in the deterrence of such changes that the efficacy of any novel treatment regimes will be measured. In particular, an emphasis will be placed on the relatively unappreciated role of arteriolar dysfunction in the clinical manifestations and pathology of this disease. [source]


The role of CTGF in the diabetic rat retina and its relationship with VEGF and TGF-,2, elucidated by treatment with CTGFsiRNA

ACTA OPHTHALMOLOGICA, Issue 6 2010
Hongwei Yang
Acta Ophthalmol. 2010: 88: 652,659 Abstract. Purpose:, The critical association of connective tissue growth factor (CTGF) with diabetic retinopathy (DR) remains to be clarified. We detected alterations in the gene and protein expression of CTGF and related cytokines, including vascular endothelial growth factor (VEGF) and transforming growth factor-,2 (TGF-,2), and their response to small interfering RNA (siRNA) targeting the CTGF (CTGFsiRNA) in the retina of diabetic rats. The relationships between CTGF, VEGF and TGF-,2 levels, as well as the degree of apoptosis in the diabetic retina, were also investigated. Methods:, Diabetes was induced in rats by the ,-cell toxin streptozotocin (STZ). Retinas were obtained from control and diabetic rats and similar animals treated with CTGFsiRNA by intravitreal injection. mRNA level and protein expression of CTGF, VEGF and TGF-,2 were measured by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, and located by immunohistochemistry. Retinal apoptosis was detected by TUNEL staining. Results:, The levels of CTGF, VEGF and TGF-,2 and the number of TUNEL-positive nuclei were significantly higher in diabetic retinas than in control retinas (p < 0.01). The level of CTGF rose at 8 weeks, earlier than levels of VEGF and TGF-,2, which rose at 12 weeks after the onset of diabetes. The difference was significant (p < 0.05). siRNA-mediated inhibition of CTGF mRNA inhibited retinal VEGF and TGF-,2 and also resulted in a significant decrease in apoptosis. Significant correlations were found between CTGF and VEGF (p = 0.009), CTGF and TGF-,2 (p = 0.01), and apoptosis and these three cytokines (p < 0.01) in the rat retina early in diabetes. Conclusions:, These results suggest that the diabetes-mediated increase in CTGF upregulates VEGF and TGF-,2 expression and induces apoptosis in the retina. This elevation may be inhibited by treatment with CTGFsiRNA. Connective tissue growth factor may serve as a potential target for the prevention and treatment of DR. [source]


2125: High glucose sensitizes human retinal endothelial cells for IFN-g-mediated apoptosis

ACTA OPHTHALMOLOGICA, Issue 2010
R NAGARAJ
Purpose The biochemical mechanisms by which inflammatory cytokines cause damage in the diabetic retina are poorly understood. Indoelamine 2, 3-dioxygenase (IDO) is an inducible by IFN-, enzyme and is the first enzyme of the kynurenine pathway, which produces cytotoxic kynurenines. In this study we have investigated the role of IDO in apoptosis of human retinal capillary endothelial cells (HREC) under hyperglycemic conditions. Methods HREC were cultured in medium containing high glucose (25 mM) or low glucose (7.5 mM) and incubated with 1-100 U/ml of IFN-,. IDO activity was measured by an HPLC assay. Expression of IFN-, receptor 1, and activation of the JAK-STAT signaling pathway along with activation of PKC-, was assessed by Western blotting. HREC apoptosis was measured by Hoechst staining. The role of IDO in HREC apoptosis was evaluated in the presence specific chemical inhibitors of the kynurenine pathway. Results IFN-, dose-dependently activated JAK-STAT signaling and PKC-,, and upregulated IDO. The IDO-mediated tryptophan oxidation led to formation of kynurenines, which was followed by chemical modification of proteins by kynurenines in HREC. These changes were accompanied by production of reactive oxygen species (ROS) and depletion of protein-free thiols. IFN-, inhibited cell cycle at low concentrations and caused caspase-3-mediated apoptosis and at higher concentrations, and those effects were amplified in the presence of high glucose in HREC. We found that IFN-, mediated cytotoxicity in HREC was primarily due to ROS generated by 3-hydroxykynurenine. Conclusion Our results suggest that high glucose sensitizes HREC to deleterious effects IFN-, and provide a novel mechanistic pathway for retinal capillary endothelial cell death in diabetes. [source]


New insights into the pathogenic role of advanced glycation in diabetic retinopathy

ACTA OPHTHALMOLOGICA, Issue 2008
AW STITT
Purpose Retinopathy is the most common microvascular complication of diabetes. The clinicopathology of microvascular lesions and neuroglial dysfunction in the diabetic retina have been extensively studied, although the relative contribution of various biochemical sequelae of hyperglycaemia remains ill-defined. The formation and accumulation of advanced glycation endproducts (AGEs) is an important pathogenic pathway in the progression of diabetic retinopathy although some of the cellular and molecular pathologies initiated by these adducts in retinal cells remain unknown. Methods This presentation will cover several aspects of AGE-linked retinal pathology and demonstrate opportunities for therapeutic intervention. The studies outlined will cover a wide range of molecular cell biology approaches using appropriate in vitro and in vivo model systems. Results It will be demonstrated that AGEs form in vivo in the diabetic retina through the reaction of alpha-oxaloaldehydes leading to significant modifications of retinal proteins. Evidence will be presented to demonstrate that these AGEs act as significant effectors of retinal vascular and neuroglial cell dysfunction, leading to pro-inflammatory responses, growth factor imbalance and, ultimately, neurovascular lesions such as blood retinal barrier dysfunction and microvascular degeneration. The protective role of novel AGE-inhibitors will also be shown. Conclusion Evidence now points towards a pathogenic role for advanced glycation in the initiation and progression of diabetic retinopathy and this review lecture will outline the current state of knowledge of AGE-related pathology in the retina at a cellular and molecular level. [source]


The role of CTGF in the diabetic rat retina and its relationship with VEGF and TGF-,2, elucidated by treatment with CTGFsiRNA

ACTA OPHTHALMOLOGICA, Issue 6 2010
Hongwei Yang
Acta Ophthalmol. 2010: 88: 652,659 Abstract. Purpose:, The critical association of connective tissue growth factor (CTGF) with diabetic retinopathy (DR) remains to be clarified. We detected alterations in the gene and protein expression of CTGF and related cytokines, including vascular endothelial growth factor (VEGF) and transforming growth factor-,2 (TGF-,2), and their response to small interfering RNA (siRNA) targeting the CTGF (CTGFsiRNA) in the retina of diabetic rats. The relationships between CTGF, VEGF and TGF-,2 levels, as well as the degree of apoptosis in the diabetic retina, were also investigated. Methods:, Diabetes was induced in rats by the ,-cell toxin streptozotocin (STZ). Retinas were obtained from control and diabetic rats and similar animals treated with CTGFsiRNA by intravitreal injection. mRNA level and protein expression of CTGF, VEGF and TGF-,2 were measured by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, and located by immunohistochemistry. Retinal apoptosis was detected by TUNEL staining. Results:, The levels of CTGF, VEGF and TGF-,2 and the number of TUNEL-positive nuclei were significantly higher in diabetic retinas than in control retinas (p < 0.01). The level of CTGF rose at 8 weeks, earlier than levels of VEGF and TGF-,2, which rose at 12 weeks after the onset of diabetes. The difference was significant (p < 0.05). siRNA-mediated inhibition of CTGF mRNA inhibited retinal VEGF and TGF-,2 and also resulted in a significant decrease in apoptosis. Significant correlations were found between CTGF and VEGF (p = 0.009), CTGF and TGF-,2 (p = 0.01), and apoptosis and these three cytokines (p < 0.01) in the rat retina early in diabetes. Conclusions:, These results suggest that the diabetes-mediated increase in CTGF upregulates VEGF and TGF-,2 expression and induces apoptosis in the retina. This elevation may be inhibited by treatment with CTGFsiRNA. Connective tissue growth factor may serve as a potential target for the prevention and treatment of DR. [source]