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Reena Gupta, Amy E. Ross, Joseph B Ciolino, Shivakumar Vasanth, Ula V Jurkunas; Ascorbic acid and hydrogen peroxide levels in the aqueous humor in Fuchs Endothelial Corneal Dystrophy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1446. doi: https://doi.org/.
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Fuchs endothelial corneal dystrophy (FECD) is a progressive late-onset disorder of the corneal endothelium. Previously we have shown diminished antioxidant capacity that led to endothelial cell apoptosis in FECD ex vivo specimens. The goal of this study is to determine aqueous humor composition by analyzing the oxidant-antioxidant response in the anterior chamber (AC) of FECD patients.
The study was approved by the Institutional Review Board of Massachusetts Eye and Ear, Boston, MA. Written informed consent was acquired from FECD and cataract patients prior to surgery. Aqueous humor was obtained from patients who underwent phacoemulsification and did not exhibit endothelial degeneration (n=2) and FECD cases that underwent endothelial keratoplasty (n=2). Samples were immediately stored on dry ice and hydrogen peroxide concentrations was measured with 10ml of each sample in triplicates with Amplex Red assay. 10ml of aqueous humor samples were diluted with 90ml of 50mM perchloric acid and high performance liquid chromatography (HPLC) was used to determine the concentration of ascorbic acid at 278nm. Similarly, ascorbate was measured by HPLC prepared by mixing 9ml aqueous humor, 1ml of 10% DL-homocysteine, and 90ml of 50mM perchloric acid. Dehydroascorbate levels were calculated by subtracting ascobate from total ascorbic acid.
Preliminary data shows a 3-fold increase of hydrogen peroxide in the aqueous humor of FECD cases compared to control samples. Similarly, ascorbic acid and dehydroascorbate concentrations were both elevated by 1.8-fold in FECD compared to control samples. The ratio of ascorbic acid (ASA):dehydroascorbate (DHA) was consistent between all aqueous humor samples (6:1 in control and 5.8:1 in FECD).
Ascorbic acid, dehydroascorbate, and hydrogen peroxide were elevated in aqueous humor of FECD patients suggesting a possibly aberrant uptake of dehydroascorbate by corneal endothelium. Dehydroascorbate is the intracellular reductant that is necessary for quenching of intracellular reactive oxygen species; the elevation of which in the AC might lead to abnormally high ascorbate levels and generation of hydrogen peroxide, creating a pro-oxidant environment in the anterior chamber.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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