Orally administered epigallocatechin gallate attenuates light-induced photoreceptor damage

Brain Res Bull. 2008 Jul 1;76(4):412-23. doi: 10.1016/j.brainresbull.2008.01.022. Epub 2008 Feb 21.

Abstract

EGCG, a major component of green tea, has a number of properties which includes it being a powerful antioxidant. The purpose of this investigation was to deduce whether inclusion of EGCG in the drinking water of albino rats attenuates the effect of a light insult (2200lx, for 24h) to the retina. TUNEL-positive cells were detected in the outer nuclear layer of the retina, indicating the efficacy of the light insult in inducing photoreceptor degeneration. Moreover, Ret-P1 and the mRNA for rhodopsin located at photoreceptors were also significantly reduced as well as the amplitude of both the a- and b-waves of the electroretinogram was also reduced showing that photoreceptors in particular are affected by light. An increase in protein/mRNA of GFAP located primarily to Müller cells caused by light shows that other retinal components are also influenced by the light insult. However, antigens associated with bipolar (alpha-PKC), ganglion (Thy-1) and amacrine (GABA) cells, in contrast, appeared unaffected. The light insult also caused a change in the content of various proteins (caspase-3, caspase-8, PARP, Bad, and Bcl-2) involved in apoptosis. A number of the changes to the retina caused by a light insult were significantly attenuated when EGCG was in the drinking water. The reduction of the a- and b-waves and photoreceptor specific mRNAs/protein caused by light were significantly less. In addition, EGCG attenuated the changes caused by light to certain apoptotic proteins (especially at after 2 days) but did not appear to significantly influence the light-induced up-regulation of GFAP protein/mRNA. It is concluded that orally administered EGCG blunts the detrimental effect of light to the retina of albino rats where the photoreceptors are primarily affected.

MeSH terms

  • Administration, Oral
  • Animals
  • Antioxidants / pharmacology*
  • Antioxidants / therapeutic use
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Apoptosis / radiation effects
  • Apoptosis Regulatory Proteins / drug effects
  • Apoptosis Regulatory Proteins / metabolism
  • Apoptosis Regulatory Proteins / radiation effects
  • Catechin / analogs & derivatives*
  • Catechin / pharmacology
  • Catechin / therapeutic use
  • Glial Fibrillary Acidic Protein / genetics
  • Glial Fibrillary Acidic Protein / metabolism
  • Light / adverse effects
  • Membrane Potentials / drug effects
  • Membrane Potentials / radiation effects
  • Neuroglia / drug effects
  • Neuroglia / metabolism
  • Neuroglia / radiation effects
  • Oxidative Stress / drug effects
  • Oxidative Stress / physiology
  • Oxidative Stress / radiation effects
  • Photoreceptor Cells / drug effects*
  • Photoreceptor Cells / physiology
  • Photoreceptor Cells / radiation effects
  • RNA, Messenger / drug effects
  • RNA, Messenger / metabolism
  • RNA, Messenger / radiation effects
  • Rats
  • Rats, Wistar
  • Retina / drug effects*
  • Retina / physiopathology
  • Retina / radiation effects
  • Retinal Degeneration / drug therapy*
  • Retinal Degeneration / etiology
  • Retinal Degeneration / physiopathology
  • Rhodopsin / genetics

Substances

  • Antioxidants
  • Apoptosis Regulatory Proteins
  • Glial Fibrillary Acidic Protein
  • RNA, Messenger
  • Catechin
  • Rhodopsin
  • epigallocatechin gallate