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Roles of Catalase and the Glutathione Redox Cycle in the Regulation of Anterior-Chamber Hydrogen Peroxide

Roles of Catalase and the Glutathione Redox Cycle in the Regulation of Anterior-Chamber Hydrogen... The effects of inhibition of both glutathione synthesis and of glutathione reductase and catalase activities have been determined in the regulation of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) in the anterior chamber of pigmented rabbits. Glutathione reductase inhibition using intravitreal 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) did not significantly alter either total glutathione or the percent oxidized glutathione fraction in the iris-ciliary body. Intravitreal buthionine sulfoximine (BSO) significantly reduced the total glutathione content of iris-ciliary body and corneal endothelium, while not altering the oxidized fraction. BCNU increased the oxidized fraction of glutathione in the aqueous humor from 22 to 63% without significantly altering total glutathione levels. BSO, however, reduced total glutathione by 70% in the aqueous humor, and the oxidized fraction doubled. Decreases in the reduced glutathione concentration caused by BSO correlate with increases in the normally stable ratio of H<sub>2</sub>O<sub>2</sub> to ascorbate concentrations in the aqueous humor, strongly suggesting that glutathione metabolism is correlated with H<sub>2</sub>O<sub>2</sub> regulation at endogenous levels of this oxidant. Both BSO and 3-aminotriazole (3AT) separately increased the half-time for the loss of exogenously added H<sub>2</sub>0<sub>2</sub> from the anterior chamber. BSO increased the half-time by 77% after 10 μl of 10 mMH<sub>2</sub>O<sub>2</sub> was injected intracamerally, while suppression of catalase activity with 3AT increased it by only 40%. With intracameral injections of 10 μl of either 25 or 50 mM H<sub>2</sub>O<sub>2</sub>, however, 3AT had a greater effect than BSO. The half-time values after 3AT pretreat-ment were 61 and 135% greater than control values at the concentrations of 25 and 50 mM H<sub>2</sub>O<sub>2</sub>, respectively; those after BSO pretreatment were at 14 and 78%. From these data we conclude that the glutathione redox system protects the anterior segment tissues from hydrogen peroxide at low concentrations of this oxidant, while catalase assumes a greater role at higher concentrations of hydrogen peroxide. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ophthalmic Research Karger

Roles of Catalase and the Glutathione Redox Cycle in the Regulation of Anterior-Chamber Hydrogen Peroxide

Costarides, A.P.; Riley, M.V.; Green, K.
Ophthalmic Research , Volume 23 (5): 11 – Jan 1, 2009
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Publisher
Karger
Copyright
© 1991 S. Karger AG, Basel
ISSN
0030-3747
eISSN
1423-0259
DOI
10.1159/000267124
Publisher site
See Article on Publisher Site

Abstract

The effects of inhibition of both glutathione synthesis and of glutathione reductase and catalase activities have been determined in the regulation of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) in the anterior chamber of pigmented rabbits. Glutathione reductase inhibition using intravitreal 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) did not significantly alter either total glutathione or the percent oxidized glutathione fraction in the iris-ciliary body. Intravitreal buthionine sulfoximine (BSO) significantly reduced the total glutathione content of iris-ciliary body and corneal endothelium, while not altering the oxidized fraction. BCNU increased the oxidized fraction of glutathione in the aqueous humor from 22 to 63% without significantly altering total glutathione levels. BSO, however, reduced total glutathione by 70% in the aqueous humor, and the oxidized fraction doubled. Decreases in the reduced glutathione concentration caused by BSO correlate with increases in the normally stable ratio of H<sub>2</sub>O<sub>2</sub> to ascorbate concentrations in the aqueous humor, strongly suggesting that glutathione metabolism is correlated with H<sub>2</sub>O<sub>2</sub> regulation at endogenous levels of this oxidant. Both BSO and 3-aminotriazole (3AT) separately increased the half-time for the loss of exogenously added H<sub>2</sub>0<sub>2</sub> from the anterior chamber. BSO increased the half-time by 77% after 10 μl of 10 mMH<sub>2</sub>O<sub>2</sub> was injected intracamerally, while suppression of catalase activity with 3AT increased it by only 40%. With intracameral injections of 10 μl of either 25 or 50 mM H<sub>2</sub>O<sub>2</sub>, however, 3AT had a greater effect than BSO. The half-time values after 3AT pretreat-ment were 61 and 135% greater than control values at the concentrations of 25 and 50 mM H<sub>2</sub>O<sub>2</sub>, respectively; those after BSO pretreatment were at 14 and 78%. From these data we conclude that the glutathione redox system protects the anterior segment tissues from hydrogen peroxide at low concentrations of this oxidant, while catalase assumes a greater role at higher concentrations of hydrogen peroxide.

Journal

Ophthalmic Research – Karger

Published: Jan 1, 2009

Keywords: Aqueous humor; Catalase; Glutathione; Hydrogen peroxide

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