Evaluation of the Neuroprotective Effect Exerted by Epigallocatechin Gallate on Retinal Cell Cultures

Abstract

Purpose: : Epigallocatechin gallate (EGCg) is a polyphenol known to exert antitumour, antimutagenic and antiapoptotic effects. All these actions can be sufficiently explained with the antioxidant properties of the molecule. Moreover it is widely accepted that EGCg may influence many metabolic pathways such as those leading to TIMP and MAPKs inhibition as well as NO modulation. Interestingly, it has been demonstrated that EGCg plays a protective role in Alzheimer’s, Parkinson’s, Huntington’s and neuronal ischemic animal models. It has been reported that, in glaucomatous patients, repetitive insults occurring in the retina as a consequence of elevated IOP cause selective death of ganglion and amacrine cells. The aim of the present study was to test the possible neuroprotective activity of EGCg in neuroretinal cultures.

Methods: : EGCg has been tested at various concentrations (0.001–1 mM) in adult Porcine Retinal Cells (PREC) and Rat Retinal cells (RAREC) subjected to different types of injury. PREC were used to set up an oxidative stress model with H₂O₂ (1 and 5 mM), while RAREC were utilised to mimic an excitotoxicity system in the presence of glutamate agonists (glutamate, NMDA, kainate). The effect of EGCg was evaluated on cell viability by MTT test and on apoptotic DNA fragmentation by TUNEL test.

Results: : Our data obtained in PREC cultures show that 0.5 and 1mM EGCg significantly reduces cell mortality due to the treatment with H₂O₂. Furthermore, 0.1mM EGCg significantly enhances cell viability at the lower concentration of H₂O₂ tested (1mM). A similar effect of 0.1–1mM of EGCg is exhibited on glutamate agonists’ toxicity in RAREC. Moreover treatment with EGCg (0.1–1 mM) in both the two experimental systems, indicates a protective effect against apoptosis DNA fragmentation, as observed by TUNEL analysis.

Conclusions: : These data have demonstrated the protective role of EGCg in neuroretinal cultures after oxidative stress. In addition, preliminary results indicate a protection of EGCg in glutamate toxicity and apoptosis. As epigallocatechin gallate crosses haemato–encephalic barrier, its use may be beneficial in the treatment of those conditions leading to retinal ischemia, such as optic neuropathy.

Keywords: antioxidants • apoptosis/cell death • neuroprotection