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J. M. Lopes De Faria, K. C. Silva, M. A. B. Morales, J. B. Lopes de Faria; Green Tea (Camellia Sinensis) Attenuates Oxidative Stress And The Activation Of Nitric Oxide Synthase Isoforms In The Retina Of Diabetic Spontaneously Hypertensive Rats.. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3728.
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Purpose/Aim of the study: The role of oxidative stress is pivotal in the pathogenesis of diabetic retinopathy (DR). Green tea (GT), or its major polyphenolic compound, has been shown to have potent antioxidant activity. In this study, we investigated the possible effects of GT on the early markers of diabetic retinopathy (DR) through oxidative/nitrosative mains.
Materials and Methods: :
Diabetes was experimentally induced in spontaneously hypertensive rats (SHR) with twelve-week-old by streptozotocin. Control rats received only vehicle (citrate buffer). The diabetic SHR (DM-SHR) groups were assigned to receive or not receive, oral GT (13.3 g/L) in drinking water.
After 12 weeks, the retinal glial reaction, demonstrated by a local increase in glial fibrillary acidic protein (GFAP) levels were increased in DM-SHR group compared with control rats (p=0.0003). Retinal oxidative stress analyzed by immunohistochemistry for 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nitrotyrosine (NT) levels, were greater in diabetic than in nondiabetic rats (p<0.0001 for 8-OHdG and p=0.04 for NT). The phosphorylated isoforms of neuronal (nNOS) and endothelial nitric oxide synthase (eNOS) were also increased in retina of diabetic SHR rats compared with control (p<0.05 for nNOS and p=0.02 for eNOS). The treatment with GT reestablished all of the above-mentioned parameters.
GT reestablished the redox state and reduced the activation of nitric oxide synthase isoforms, preventing the early diabetic retinal change. The possible mechanisms by which GT ameliorates the redox status are under investigation.
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