Reduction of Inducible Nitric Oxide Synthase via Angiotensin Receptor Blocker Prevents the Oxidative Retinal Damage in Diabetic Hypertensive Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Purpose: To investigate if nitric oxide (NO) system contributes to the beneficial effect of angiotensin II type 1 receptor (AT 1) blocker losartan in the retina of diabetic spontaneously hypertensive rats (SHR). Methods: Diabetic SHR were randomized to receive oral treatment with losartan (DM-SHRLos). After 20 days, the rats were euthanized and the retinas collected. Results: Diabetic SHR rats exhibited a significant increase in glial fibrillary acidic protein (GFAP) and decrease in occludin, markers of early diabetic retinopathy (DR). The oxidative status, evaluated by NO end-products (NO(x)(-)) levels along with the antioxidative system superoxide dismutase, revealed an accentuated imbalance in favor to oxidants in DM-SHR leading to a higher tyrosine nitration and DNA damage. The inducible NO synthase (iNOS) was also elevated in DM-SHR rats. The treatment with losartan ameliorated all of the above alterations. Conclusions: Oral treatment with losartan reduces iNOS expression and reestablishes the redox status, thus ameliorating the early markers of DR in a model of diabetes and hypertension.356519528Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP [05/58189-5, 08/54068-7

Exogenous SOD Mimetic Tempol Ameliorates the Early Retinal Changes Reestablishing the Redox Status in Diabetic Hypertensive Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PURPOSE. The purpose of this study was to investigate the efficacy of tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl), a superoxide dismutase mimetic, in preventing early retinal molecular changes in a model that combines hypertension and diabetes. METHODS. Four-week-old spontaneously hypertensive rats (SHR) were rendered diabetic by streptozotocin. Diabetic SHR rats (DM-SHR) were randomized to receive or not receive tempol treatment. After 20 days of induction of diabetes, the rats were euthanatized, and their retinas were collected. RESULTS. The early molecular markers of diabetic retinopathy (DR), glial fibrillary acidic protein, and fibronectin were evaluated by Western blot assays and showed an increase in DM-SHR compared with the SHR group. The oxidative balance, evaluated by superoxide production and nitric oxide end product levels estimated by a nitric oxide analyzer, and the counterpart antioxidative defense revealed an accentuated imbalance in DM-SHR compared with the SHR group. As a result, the product peroxynitrite, which was detected by immunohistochemistry for nitrotyrosine, was higher in the DM-SHR group. The retinal poly-ADP-ribose (PAR)-modified proteins, which reflect the activation of PAR polymerase (PARP), and the inducible nitric oxide synthase (iNOS) expressions were found to have increased in this group. Treatment with tempol reestablished the oxidative parameters and decreased the PAR-modified proteins, thus preventing extracellular matrix accumulation and glial reaction. CONCLUSIONS. The administration of tempol prevented oxidative damage, decreased iNOS levels, and ameliorated the activation of PARP in the retinas of diabetic hypertensive rats. Consequently, the early molecular markers of DR, such as glial reaction (glial fibrillary acidic protein [GFAP]) and extracellular matrix accumulation (fibronectin), were prevented in tempol-treated rats. (Invest Ophthalmol Vis Sci. 2010; 51:4327-4336) DOI:10.1167/iovs.09-4690O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.51843274336Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordination for the Improvement of Higher Education PersonnelFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [05/58189-5, 08/54068-7

Spironolactone improves nephropathy by enhancing glucose-6-phosphate dehydrogenase activity and reducing oxidative stress in diabetic hypertensive rat

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Spironolactone (SPR), a mineralocorticoid receptor blocker, diminishes hyperglycemia-induced reduction in glucose-6-phosphate dehydrogenase (G6PD) activity, improving oxidative stress damage. This study investigated whether SPR ameliorates nephropathy by increasing G6PD activity and reducing oxidative stress in spontaneously hypertensive diabetic rats (SHRs). The streptozotocin-induced diabetic rats received or not SPR 50 mg/kg per day, for eight weeks. A human mesangial cell line was cultured in normal or high glucose conditions, with or without SPR, for 24 h. Plasma glucose levels and systolic blood pressure were unaltered by diabetes or by SPR treatment. Albuminuria, fibronectin expression, 8-OHdG urinary levels, lipid peroxidation and p47phox expression were higher in the diabetic rats compared with the control and were reduced by SPR. The antioxidant GSH/GSSG ratio was reduced in the diabetic rats and the treatment reestablished it. Diabetes-induced SGK1 up-regulation was inhibited by SPR. Reactive oxygen species (ROS) and superoxide production induced by NADPH oxidase were increased by hyperglycemia and high glucose, in vivo and in vitro, respectively, and were reduced with SPR. Hyperglycemia and high glucose decreased G6PD activity, which was restored with SPR. These results suggest that SPR ameliorates nephropathy in diabetic SHRs by restoring G6PD activity and diminishes oxidative stress without affecting glycaemia and blood pressure.1315666Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [08/57560-0, 08/52575-9

Hypertension increases retinal inflammation in experimental diabetes: A possible mechanism for aggravation of diabetic retinopathy by hypertension

Inflammation is pivotal to the pathogenesis of diabetic retinopathy (DR). Hypertension is the main secondary risk factor associated with DR. The mechanisms by which hypertension increases the risk for DR are poorly understood. The aim of the current study was to investigate the contribution of genetic hypertension to early retinal inflammation in experimental diabetes. Diabetes was induced in 4-week-old (developing hypertension) and 12-week-old (fully hypertensive) spontaneously hypertensive rats (SHR) and age-matched control normotensive Wistar Kyoto (WKY) rats by administration of streptozotocin (50 mg/kg, i.v); after 20 days the rats were sacrificed and the retinas were collected. ED1 positive cells, ICAM-1 and VEGF levels were significantly higher in diabetic SHR in both prehypertensive and hypertensive ages (p < 0.005). NF-kappa B p65 levels were higher in prehypertensive SHR and in hypertensive diabetic SHR (p < 0.05). Induction of diabetes in normotensive WKY rats did not show any alteration in retinal expression of inflammatory parameters. Therefore, we conclude that the developing hypertension and also the fully developed hypertension lead to earlier development of inflammation in diabetic retina. Aggravation of the inflammatory process may be involved in the mechanism by which essential hypertension exacerbates retinopathy in the presence of diabetes.32653354

Diabetic macular edema: Risk factors and concomitants

Purpose: To investigate the systemic and ocular factors associated with diffuse macular edema in patients with diabetic retinopathy (DR) and compare with patients with focal or no macular edema. Methods: From 160 consecutive patients with DR, we obtained medical and ocular histories, blood pressure and, visual acuity, Macular edema was determined by biomicroscopy and stereoscopic fundus photography. Fluorescein angiography was used in the characterization of its leakage, and the vitreoretinal relationship was performed by preset lens biomicroscopy. Results: Among adult-onset diabetes mellitus (DM) patients, 55% had diffuse, 23.5% had focal and 21.5% had no macular edema (p=0.01), The risk of developing diffuse macular edema was 3.2 times greater in patients with high blood pressure (HBP) (95% confidence interval (CI), 1.5 to 6.9), Patients,vith cardiovascular disease (CVD) had a higher prevalence of diffuse (58.0%) than focal (26.0%) or no maculopathy (16.0%) (p=0.01), The odds for development of diffuse macular edema was 3.4 times greater in patients,vith vitreomacular adhesion (95% CI, 1.15 to 13.30) than in those with complete posterior vitreoretinal attachment or vitreoretinal separation. The odds for development of diffuse macular edema were 6.2 (95% CI, 1.83 to 21.04) and 7.7 times greater (95% CI, 3.12 to 19.12) in patients with PPDR and PDR, respectively, in comparison with those,vith NPDR, Conclusions: In this study adult-onset DM, HBP, CVD, vitreomacular adhesion and advanced retinopathy were associated with increased risk of development of diffuse diabetic macular edema.77217017

Objective measurement of contrast sensitivity function using contrast sweep visual evoked responses

Aim/background-The contrast sensitivity function (CSF) measurement provides information that is not accessible by standard visual acuity determinations. The contrast sweep pattern reversal visual evoked responses (CSVER) technique was used to objectively measure the CSF in clinical practice. Methods-The contrast thresholds were measured at five spatial frequencies in 10 normal subjects. The CSVER were recorded with sinusoidally modulated vertical gratings at 10 contrast levels (96, 64, 48, 32, 16, 8, 4, 2, 1, and 0.5%) presented in five spatial frequencies (0.5, 1.0, 2.0, 4.0, and 8.0 cycles per degree). Each of 10 contrast levels was displayed for 2 seconds at the desired spatial frequency. The CSVER amplitudes at the second harmonic were calculated by discrete Fourier transform. The results were compared with those obtained using a psychophysical method. Results-An inverted U-shaped CSF which peaked at 2.0 cycles per degree with a contrast sensitivity of 34.5 (contrast, 2.9%) was observed. The CSF assessed electrophysiologically was 0.62 to 0.79 log units lower than the sensitivity measured using the psychophysical method. However, the overall shapes were highly correlated. Conclusion-One can objectively measure CSF with CSVER and this may be useful in patients in whom the psychophysical method is Limited.82216817

Green Tea Is Neuroprotective in Diabetic Retinopathy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PURPOSE. Green tea (GT), widely studied for its beneficial properties in protecting against brain ischemia, is a rich source of polyphenols, particularly (-)-epigallocatechin gallate (EGCG). The results presented here demonstrate the beneficial effects of GT in diabetic retinas and in retinal cells under diabetic conditions. METHODS. Diabetes was induced in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats. Treatment animals received GT orally for 12 weeks. A vehicle was administered orally to the control animals. The protective effects of GT were also evaluated in Muller and in ARPE-19 cells. RESULTS. In diabetic rats, there was an increase in the expression of glial fibrillary acidic protein (GFAP), oxidative retinal markers, and glutamine synthetase levels. In addition, there was a decrease in occludin and glutamate transporter and receptor. Diabetic SHR also demonstrated blood-retinal barrier breakdown and impaired electroretinography results. Muller cells exposed to high-glucose medium produced higher levels of reactive oxygen species (ROS) and glutamine synthetase but reduced levels of glutathione, glutamate transporter, and glutamate receptor. Similarly, ARPE-19 cells exhibited increased ROS production accompanied by decreased expression of claudin-1 and glutamate transporter. Treatment with GT fully restored all the above-mentioned alterations in diabetic animals as well as in retinal cells. CONCLUSIONS. GT protected the retina against glutamate toxicity via an antioxidant mechanism. These findings reveal a novel mechanism by which GT protects the retina against neurodegeneration in disorders such as diabetic retinopathy. (Invest Ophthalmol Vis Sci. 2013;54:1325-1336) DOI:10.1167/iovs.12-10647O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.54213251336Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2008/57560-0, 2010/11514-7