8-epi-prostaglandin-f2alpha and Diabetic-Retinopathy

The aim of this study is to investigate markers of inflammation and oxidative stress in an early model of diabetic retinopathy, correlate retinal and plasma results and evaluate the influence of treatment by N-acetylcysteine (NAC), a free radical scavenger.. Four groups were studied: control (C), streptozotocin (STZ)-induced diabetic rats (D), STZ rats following 8 weeks of NAC (DT), and control rats following 8 weeks of NAC (CT). Plasma levels of free 15-F2t-isoprostane (15-F-2t-IsoP), superoxide dismutase (SOD) and tumour necrosis factor-alpha (TNF-alpha) were obtained. Primary antibodies against macrophages (ED-1), microglia (Ox-42), pericytes (NG-2), endothelial and perivascular cells (IB-4), haem oxygenase 1 (HO-1) and vascular endothelial growth factor (VEGF) were used.. Expression of NG-2 was robust in C, CT, DT, and mild in D. The intensity of IB-4 was higher in D and DT compared with the C and CT. Ox-42 and ED-1 expression was higher in the D than in the DT, C or CT. Expression of VEGF and HO-1 was non-specific across the four groups. Plasma levels of 15-F-2t-IsoP and TNF-alpha were higher in the D as compared with the C, CT and DT. SOD levels were lower in the D when compared with the C, CT and D.. Macrophage/microglia activation, pericyte loss and endothelial/perivascular cell changes occur early in the pathogenesis of DR. These changes are associated with an increase in plasma markers of oxidative stress and inflammation and are minimized by treatment with NAC. The results suggest that therapies that reduce free radicals will help minimize the early events in diabetic retinopathy in the STZ model.

Topics: Acetylcysteine; Animals; Biomarkers; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Dinoprost; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Fluorescent Antibody Technique, Indirect; Free Radical Scavengers; Immunoenzyme Techniques; Inflammation; Isoprostanes; Macrophages; Male; Microglia; Oxidative Stress; Pericytes; Rats; Rats, Wistar; Retina; Superoxide Dismutase; Tumor Necrosis Factor-alpha

Retinal hemodynamic responses to a F2-isoprostane, 8-epi-PGF2alpha, were quantitated in vivo in non-diabetic and diabetic rats using a video fluorescein angiography system. Vascular diameters and retinal mean circulation time were determined before and after 5 microl intra-vitreous injection of 8-epi-PGF2alpha (10(-5) to 10(-3) M), 10(-4) M 8-epi-PGF2alpha, + 10(-3) M SQ29,548 or 10(-3) M LCB2853 (two inhibitors of TXA2 receptor), 10(4) M 9beta-PGF2alpha, or the carrier in non-diabetic animals. Diabetic rats received either 8-epi-PGF2alpha 10(-4) M, or the carrier. Compared to control animals, diabetic rats presented in the basal state a venous vasodilation (P<0.01), without modification of retinal mean circulation time or blood flow. After intravitreous injection of 8-epi-PGF2alpha, a significant arterial vasoconstriction was observed in control but not in diabetic animals. This vasoconstriction was concomitant with increased retinal mean circulation time in control but not in diabetic rats, inducing an impaired reduction of blood flow. No vasoconstriction was observed after injection of either the carrier, 9beta-PGF2alpha or the isoprostane associated to the inhibitors of TXA2 receptors. This is the first direct observation that the isoprostane 8-iso-PGF2alpha is a potent vasoconstricting agent in the retina. It occurs at the arterial but not venous level, and is likely mediated through a TXA2-like receptor. Differences observed between control and diabetic animals suggest altered adaptative mechanisms toward vasoconstrictor substances (such as isoprostanes) in diabetic rats.

Topics: Angiography; Animals; Blood Flow Velocity; Bridged Bicyclo Compounds, Heterocyclic; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Dinoprost; Dose-Response Relationship, Drug; Fatty Acids, Unsaturated; Hydrazines; Male; Phenylacetates; Prostaglandin H2; Prostaglandins H; Rats; Rats, Wistar; Regional Blood Flow; Retinal Vessels; Sulfonamides; Vasoconstrictor Agents