Nitrite-Induced Photo-Oxidation of Thiol and Its Implications in Smog Toxicity to the Eye: Prevention by Ascorbate

Abstract

ABSTRACT

Studies have been conducted on nitrite-induced oxidation of corneal thiols and reduced glutathione (GSH). Oxidation of GSH in the presence of nitrite (NaNO₂) was minimal in the dark. Exposure of GSH to UV (365 nm) in the presence of nitrite substantially accelerated this oxidation; only <10% of the original GSH remained at the end of 20 minutes. A similar Thiol depletion was observed in the case of corneal epithelial extracts irradiated with UV in the presence of the nitrite. Nitrite is therefore considered to be a potent phototoxicant with possible pathophysiological implications to the external eye tissues. Ascorbate was found to be effective in preventing thiol oxidation, suggesting the possibility of preventing nitrogen oxide-based smog irritation to the eye by this physiologically compatible antioxidant.