BLUE LIGHT-INDUCED REACTIVITY OF RETINAL AGE PIGMENT - IN-VITRO GENERATION OF OXYGEN-REACTIVE SPECIES

Exposure of the eye to intense light, particularly blue light, can cau se irreversible, oxygen-dependent damage to the retina, However, no ke y chromophores that trigger such photooxidative processes have been id entified yet, We have found that illumination of human retinal pigment epithelium (RPE) cells with light induces significant uptake of oxyge n that is both wavelength- and age-dependent, Analysis of photoreactiv ity of RPE cells and their age pigment lipofuscin indicates that the o bserved photoreactivity in RPE cells is primarily due to the presence of lipofuscin, which, under aerobic conditions, generates several oxyg en-reactive species including singlet oxygen, superoxide anion, and hy drogen peroxide, We have also found that lipofuscin-photosensitized ae robic reactions lead to enhanced lipid peroxidation as measured by acc umulation of lipid hydroperoxides and malondialdehyde in illuminated p igment granules, Hydrogen peroxide is only a minor product of aerobic photoexcitation of lipofuscin, We postulate that lipofuscin is a poten tial photosensitizer that may increase the risk of retinal photodamage and contribute to the development of age related maculopathy.