Abstract
Purpose: :
Our previous studies showed decreased levels of NF-E2-related factor 2 (Nrf2), a major transcription factor responsible for activation of antioxidant genes, in Fuchs Endothelial Corneal Dystrophy (FECD). Sulforaphane (SFN) is a naturally occurring glucosinolate, which has been shown to confer cytoprotection by activating Nrf2. The purpose of this study was to investigate the effect of SFN on Nrf2 activation and apoptosis in FECD.
Methods: :
FECD specimens were removed during transplantation and normal corneas were donated by Tissue Banks International. Specimens of corneal endothelial cells (CEnCs) with Descemet’s membrane were cut in 2 halves and one half was treated with 50 µM SFN for 4 hours at 37°C. In separate specimens, SFN treatment was followed by induction of oxidative stress by incubation with tert-Butyl hydroperoxide (tBHP) (500 µM for 4 hours). CEnC apoptosis was detected by a TUNEL assay using confocal microscopy. Cell counting was performed by Image-J (NIH) software. Protein levels and cellular localization of Nrf2 were assessed by western blot and immunohistochemistry, respectively.
Results: :
CEnC apoptosis in FECD was 31%, decreasing to 14% (n=5, p<0.01) with SFN treatment. SFN decreased CEnC apoptosis by 43% (n=6, p<0.05) in specimens exposed to pro-oxidants. Nrf2 protein level was significantly increased in SFN-treated as compared to non-treated CEnCs (n=4, p=0.03). Exposure of normal CEnCs to tBHP increased nuclear localization of Nrf2, which was further enhanced by SFN. Oxidative stress did not increase nuclear localization of Nrf2 in FECD, but pre-treatment with SFN significantly enhanced nuclear translocation of Nrf2.
Conclusions: :
SFN significantly diminishes CEnC apoptosis and potentially provides a novel pharmacotherapeutic target for treating FECD.
Keywords: apoptosis/cell death • antioxidants • degenerations/dystrophies