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N. N. Osborne, G.-Y. Li, R. Safa, K. D. Kang, B. Zhang, R. Fawcett, B. L. A. Costa; Epigallocatechin Gallate (ECGC) Administrated via Drinking Water Attenuates Light and Ischemic Insults to the Rat Retina. Invest. Ophthalmol. Vis. Sci. 2008;49(13):6109.
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To deduce whether EGCG, a component of green tea, can affect light or ischemia/reperfusion (IR) injuries to the rat retina when present in drinking water.
Ischemia was delivered to one eye of adult albino rats by elevation of intraocular pressure (120 mmHg) for 50 minutes. A light insult (2200 lux) was given to other rats for 24 hours. EGCG (0.4%) was present in some drinking water three days before and 3-5 days after an insult. Electroretinograms were recorded before and 4-5 days after an insult. Rats were killed 1-2 days later and retinas processed for immunohistochemistry and/or DNA breakdown (TUNEL). Retinal mRNA and protein levels of defined antigens were determined by RT-PCR and western blotting. Moreover, optic nerve neurofilament-light (NF-L) and tubulin content were determined for rats given IR.
IR or light insults caused a drastic reduction of the a- and b-wave amplitudes of electroretinograms and blunted significantly (n = 6-10, p< 0.01) by EGCG treatment. Photoreceptors were particularly affected (TUNEL positive cells in the outer nuclear layer and a reduction in photoreceptor specific protein, Ret-P1 and the mRNA rhodopsin) by a light insult accompanied by an up-regulation of GFAP. EGCG significantly attenuated (n= 8-16, p < 0.05) the light-induced changes to retinal proteins and mRNAs. Unlike a light insult, IR caused a clear alteration of certain inner retinal antigens that were attenuated by EGCG. Moreover, in vehicle-treated rats, IR caused a decrease in protein/mRNA levels of antigens associated with ganglion cells (Thy-1, NF-L, melanopsin) that were significantly (n = 8, p<0.05) counteracted by EGCG. In addition, IR caused a reduction in optic nerve NF-L and tubulin proteins that were significantly (n = 10, p<0.05) less reduced in EGCG treated animals.
EGCG has a broad spectrum of neuroprotective properties which includes it being a powerful antioxidant. EGCG is well tolerated and crosses cell barriers easily. The present studies show that it reaches significant concentrations in the retina when given orally to attenuate insults of IR or light to the rat retina.
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