The aim of this study was to provide support for
epigallocatechin gallate (EGCG), a component of
green tea, to be considered in the context for neuroprotection in
glaucoma, where administration by an oral route is required for adequate penetration into the retina.
Ischemia was delivered to one eye of a number of rats by raising the intraocular pressure. EGCG was present in the
drinking water of half of the animals 3 days before
ischemia and also during the next 5 days of reperfusion. The electroretinograms (ERGs) of both eyes from all rats were recorded before
ischemia and 5 days following
ischemia. Seven days after
ischemia retinas from both eyes of all rats were either analysed for the localisation of various
antigens or extracts prepared for analysis for the level of specific
proteins and mRNAs.
Ischemia/reperfusion to the retina affected a number of parameters. These included the localisation of Thy-1 and
choline acetyltransferase, the a- and b-wave amplitudes of the ERG, the content of certain
retinal and optic nerve
proteins and various mRNAs. Significantly, EGCG statistically blunted many of the effects induced by
ischemia/reperfusion which included the activation of
caspases. These studies demonstrate conclusively that orally administered EGCG attenuates injury to the retina caused by
ischemia/reperfusion where
caspases were activated. Studies were also conducted on a cell line (RGC-5 cells) where it was shown that white light (1000 lx, 48 h)-induced apoptosis is
caspase-independent and can be blunted by EGCG. The present studies support the view for the use of EGCG in the treatment of
glaucoma based on the premise that any potential
neuroprotective agent must be administered orally, have a safe profile and poses a broad spectrum of properties that allows various risk factors (that include
ischemia and light) to be attenuated.