High-fat diet causes endothelial dysfunction in the mouse ophthalmic artery.

Obesity is a significant health concern that leads to impaired vascular function and subsequent abnormalities in various organs. The impact of obesity on ocular blood vessels, however, remains largely unclear. In this study, we examined the hypothesis that obesity induced by high-fat diet produces vascular endothelial dysfunction in the ophthalmic artery. Mice were subjected to a high-fat diet for 20 weeks, while age-matched controls were maintained on a standard diet. Reactivity of isolated ophthalmic artery segments was assessed in vitro. Reactive oxygen species (ROS) were quantified in cryosections by dihydroethidium (DHE) staining. Redox gene expression was determined in ophthalmic artery explants by real-time PCR. Furthermore, the expression of nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2), the receptor for advanced glycation end products (RAGE), and of the lectin-like oxidized low-density-lipoprotein receptor-1 (LOX-1) was determined in cryosections using immunofluorescence microscopy. Ophthalmic artery segments from mice on a high-fat diet exhibited impaired vasodilation responses to the endothelium-dependent vasodilator acetylcholine, while endothelium-independent responses to nitroprusside remained preserved. DHE staining intensity in the vascular wall was notably stronger in mice on a high-fat diet. Messenger RNA expression for NOX2 was elevated in the ophthalmic artery of mice subjected to high fat diet. Likewise, immunostainings revealed increased expression of NOX2 and of RAGE, but not of LOX-1. These findings suggest that a high-fat diet triggers endothelial dysfunction by inducing oxidative stress in the ophthalmic artery via involvement of RAGE and NOX2.

Sulodexide Prevents Hyperglycemia-Induced Endothelial Dysfunction and Oxidative Stress in Porcine Retinal Arterioles.

Diabetes mellitus may cause severe damage to retinal blood vessels. The central aim of this study was to test the hypothesis that sulodexide, a mixture of glycosaminoglycans, has a protective effect against hyperglycemia-induced endothelial dysfunction in the retina. Functional studies were performed in isolated porcine retinal arterioles. Vessels were cannulated and incubated with highly concentrated glucose solution (HG, 25 mM D-glucose) +/- sulodexide (50/5/0.5 µg/mL) or normally concentrated glucose solution (NG, 5.5 mM D-glucose) +/- sulodexide for two hours. Endothelium-dependent and endothelium-independent vasodilatation were measured by videomicroscopy. Reactive oxygen species (ROS) were quantified by dihydroethidium (DHE) fluorescence. Using high-pressure liquid chromatography (HPLC), the intrinsic antioxidant properties of sulodexide were investigated. Quantitative PCR was used to determine mRNA expression of regulatory, inflammatory, and redox genes in retinal arterioles, some of which were subsequently quantified at the protein level by immunofluorescence microscopy. Incubation of retinal arterioles with HG caused significant impairment of endothelium-dependent vasodilation, whereas endothelium-independent responses were not affected. In the HG group, ROS formation was markedly increased in the vascular wall. Strikingly, sulodexide had a protective effect against hyperglycemia-induced ROS formation in the vascular wall and had a concentration-dependent protective effect against endothelial dysfunction. Although sulodexide itself had only negligible antioxidant properties, it prevented hyperglycemia-induced overexpression of the pro-oxidant redox enzymes, NOX4 and NOX5. The data of the present study provide evidence that sulodexide has a protective effect against hyperglycemia-induced oxidative stress and endothelial dysfunction in porcine retinal arterioles, possibly by modulation of redox enzyme expression.