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Ula V. Jurkunas, Maya Bitar, Yuming Chen, Behrooz Azizi; Decline in DJ-1 in Fuchs Endothelial Corneal Dystrophy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6469.
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Oxidative stress is a contributor to Fuchs corneal endothelial dystrophy (FECD) pathogenesis. We detected decreased expression of antioxidant enzymes known to be regulated by nuclear factor erythroid 2-related factor 2 (Nrf2) in FECD. The purpose of this study was to determine the role of Nrf2 transcription factor and its regulators in corneal endothelial cell (CEC) susceptibility to oxidative stress seen in FECD.
Human corneal endothelial cell-Descemet’s membrane (HCEC-DM) complexes were dissected from the stroma of normal and FECD specimens. CECs were treated with tBHP (0, 500, 1000 µM) for 4 h at room temperature. Real-time PCR and western blotting were used to detect levels of Nrf1, Nrf2, Keap1, and DJ-1. Cellular apoptosis and oxidative DNA damage were assessed by TUNEL assay and immunocytochemical analysis using anti-8OHdG antibody, respectively.
Significant decrease in Nrf2 protein levels (n=12, p=0.03) with no change in Nrf2 mRNA expression was detected in FECD samples as compared to normal controls. Similarly, levels of Nrf1 and Keap 1 (a protein that targets Nrf2 for proteosomal degradation) mRNA levels were unchanged. Two-fold decrease in DJ-1 (a protein that stabilizes Nrf2 protein by impairing proteosomal degradation) level (p=0.04) was accompanied by significant decrease in DJ-1 mRNA expression (n=12, p=0.02) in FECD as compared to normal CECs. Pro-oxidant treatments increased apoptotic rate and oxidative DNA damage in FECD CEC; in response to tBHP exposure, DJ-1 production was 6-fold higher (p=0.003) in normal CEC as compared to FECD CEC while Keap1 protein synthesis increased by 4-fold in FECD as compared to normal CECs (p=0.03).
Decreased Nrf2 protein stability in FECD could be related to decrease in expression of its stabilizer, DJ-1 protein. Elevated Keap 1 levels in FECD potentially signify heightened Nrf2 proteosomal degradation. Susceptibility of FECD-affected corneal endothelium to oxidative stress is likely related to diminished Nrf2-regulated antioxidant defense.
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