Glutathione and ocular photobiology

Glutathione is present in both the reduced and oxidized form in the cornea, aqueous humor, ocular lens and retina. In these tissues it serves a variety of functions including maintaining normal tissue hydration (in the cornea) detoxifying peroxides and electrophilic compounds via enzymatic pathways and acting as a free radical scavenger to protect against photoinduced damage. In the ocular lens, glutathione levels decrease with aging and cataract formation. Recent evidence which may account in part for this phenomenon suggests that glutathione is altered when subjected to UV radiation in the presence of H2O2. Analyses employing fluorescence, phosphorescence, UV absorption and proton mode NMR spectroscopy demonstrate that UV exposure does alter both the reduced and oxidized forms of glutathione, producing the same final products. Moreover, while H2O2 speeds up the process, it is not essential to the reaction.