Neuroprotective effect of epigallocatechin-3-gallate on retinal ganglion cells in optic nerve crush rat model

Abstract

Objective To investigate the neuroprotective effect of epigallocatechin-gallate (EGCG),the major catechin found in green tea, in an optic nerve crush (ONC) rat model. Methods Seventy-two Wistar rats were divided randomly into four groups: normal control, sham-operation+ EGCG, ONC+vehicle, and ONC+ EGCG groups. Animals were treated intraperitoneally and orally with either vehicle (normal saline) or EGCG (25 mg/kg, injected daily for up to five days, and orally 2 mg/kg daily afterwards). Two days after the first injection, an ONC injury using a micro optic nerve clipper was performed at approximately 2 mm from the optic nerve head for 60 seconds. Fluorogold was injected into bilateral superior colliculi five days before sacrifice and fluorescent gold labeled retinal ganglion cells (RGC)were counted under fluorescence microscopy on days seven, 14 and 28 after optic nerve crush. Meanwhile,the expression of neurofilament triplet L (NF-L) was measured by immunohistochemistry and Western blotting. Results In the ONC + vehicle group, a progressive loss of RGC was observed;however,compared with the ONC+vehicle group, RGC density was significantly higher on day seven (t=3. 216, P=0. 009), day 14 (t=2. 609, P=0. 026) and day 28 (t=2. 792, P=0. 019) , and a significant increase of theNF-L protein expression has been observed on days seven, 14 and 28 after optic nerve crush in the ONC+EGCG group. Conclusions EGCG has a protective effect to the bodies and axons of the RGC after optic nerve crush. Key words: Optic nerve injuries; Callic acid /therapeutic use; Retinal ganglion cells; Animal experimentation