Protective Effect of Hyaluronic Acid on the Corneal Endothelial Function Against Free-Radical Damage

PURPOSE: To investigate the protective effects of hyaluronic acid with glutathione and ascorbic acid on corneal endothelial function against free-radical damage. METHODS: bovine corneal endothelial(BCEN) cells were treated with a flux of chemically generated superoxide anion produced by the combination of 1 mM hypoxanthine and 0.06 U/ml xanthine oxidase(HX-XO) for 10 minutes, and rabbit corneas were mounted in the dual-chamber specular microscope and perfused with bicarbonate Ringer(BR) solution for one hour and their endothelial surface was exposed to HX-XO for five minutes, and then perfused with glutathione, hyaluronic acid, or ascorbic acid in BR solution for three hours. BCEN cells was observed using MTT assay and rabbit corneal thickness was measured every 15 minutes and corneal swelling rates were calculated by linear regression analysis. Also, corneal endothelial permeability was measured using carboxyfluorescein and fluorometer. RESULTS: MTT assay showed less cytotoxicity in the cells treated with glutathione, hyaluronic acid, or ascorbic acid compared to HX-XO alone. Glutathione, hyaluronic acid, or ascorbic acid reduced the rabbit corneal swelling caused by HX-XO. Corneal endothelial permeability(Pac) increased in corneas perfused with HX-XO(7.88 x 10 cm/min) while those with BR had Pac of 4.54 x 10 cm/min. Following treatment with glutathione, hyaluronic acid, or ascorbic acid, Pac decreased to 4.96, 6.81, and 5.25 respectively(p<0.05). CONCLUSIONS: In conclusion, these data suggest that hyaluronic acid scavenges HX-XO-generated oxyradicals as well as glutathione and less likely ascorbic acid.

The Effect of Taurine on Corneal Endothelial Damage by Free-radicals

PURPOSE: To investigate the protective effect of taurine on the corneal endothelial damage by oxidative stress. METHODS: Rabbit corneas were mounted in the dual-chambered specular microscope and perfused with bicarbonate-Ringer solution(BR) for 1 hour, and endothelial surface was treated with hypoxanthine-xanthine oxidase(HX-XO) for 5 minutes, and perfused with BR for 3 hours in control group, while perfused with 0.5, 1.0, 2.0 mM taurine in BR in test group. Corneal thickness was measured every 15 minutes and corneal swelling rates were calculated by linear regression analysis. Also, corneal permeability was measured using carboxyfluorescein and fluorometer. Using bovine corneal endothelial cells, MTT assay was done. RESULTS: On MTT assay, cytotoxicity of HX-XO group was 47.69% while those treated with 0.5, 1.0, 2.0 mM taurine were 36.22%, 29.73%, 24.90%, respectively(P<0.05). 0.5, 1.0 and 2.0 mM taurine group (12.88, 10.75 and 8.95 um/hr, respectively) reduced the HX-XO-induced corneal swelling rate(20.08 um/hr)(P<0.05). Corneal endothelial permeability(Pac) showed 7.96 x 10(-4) cm/min in corneas perfused with HX-HO. Also, each taurine solutions markedly reduced Pac(7.00+/-0.29 x 10(-4), 6.51+/-0.25 x 10(-4) and 5.37+/-1.41 x 10(-4) cm/min, respectively)(P<0.05). CONCLUSIONS: The results of this study showed that taurine may prevent hydrogen peroxide-induced corneal endothelial damage.