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G.R. Lee, D. McDonald, A.W. Stitt; Regulation of adhesion molecule expression on retinal capillary endothelium by exposure to high glucose: a role for advanced glycation end–products (AGEs)? . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3203.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Leukostasis may represent an important physiological factor in diabetic retinopathy leading to capillary occlusion and is directly related to up–regulation of ICAM–1. AGEs have been previously shown to modulate this process. However, the role of intracellular AGEs, formed rapidly via increased flux of glucose through glycolytic pathways in retinal endothelial cell pathology is not defined. Using pyridoxamine, a specific inhibitor of advanced glycation, the aim of this study was to determine the effects of intracellularly–derived AGEs on adhesion molecule expression and intracellular superoxide production in retinal microvascular endothelial cells (RMECs). Methods:Bovine RMECs were grown in low (5mM) or high D–glucose (25 mM) for 10 days. Controls were exposed to L–glucose (25mM) as a non–metabolised, osmolality control. RMECs were also treated with pyridoxamine (15 or 150 µM) for 10 days. Expression of the cellular adhesion molecules ICAM–1, VCAM–1 and E–selectin was quantified by flow cytometric analysis. The glucose mediated production of superoxide (O2–) from RMECs was determined spectrophotometrically (A550nm) as the SOD inhibitable reduction of cytochrome C. Results:Compared to low glucose controls, ICAM–1 expression on RMECs was increased by 30% upon exposure to high D–glucose. VCAM–1 and E–selectin expression was not appreciably altered by high D–glucose but was increased by 21% and 50%, respectively by high L–glucose compared to low glucose culture conditions. In the presence of pyridoxamine, VCAM–1 and E–selectin expression was attenuated irrespective of isomer type or concentration of glucose. O2– production was 7–fold and 2–fold greater in the presence of high D– and L–glucose, respectively, than in low glucose cultures. Pyridoxamine attenuated superoxide production by high L–glucose but completely abolished the effects of high D–glucose. Conclusions:Generation of O2– and up–regulation of adhesion molecule expression in RMECs is regulated by exposure to high glucose conditions. The AGE–inhibitor, pyridoxamine can modulate these pathogenic responses, suggesting that rapidly–forming, intracellular AGEs could play an important role in retinal vasodegeneration during diabetes.
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