BLUE LIGHT-INDUCED SINGLET OXYGEN GENERATION BY RETINAL LIPOFUSCIN INNONPOLAR MEDIA

Accumulation of lipofuscin (LF) is a prominent feature of aging in the human retinal pigment epithelium (RPE) cells. This age pigment exhibi ts substantial photoreactivity, which may increase the risk of retinal photodamage and contribute to age-related maculopathy, In a previous study, we detected singlet oxygen generation by lipofuscin granules ex cited with blue light. In this paper we investigated the ability of hy drophobic components of lipofuscin to photogenerate singlet oxygen in non-polar environments. Singlet oxygen was detected directly by monito ring its characteristic phosphorescence at ca 1270 nm. The action spec trum of singlet oxygen formation indicated that this process was stron gly wavelength-dependent and its efficiency decreased with increasing wavelength by a factor of ten, comparing 420 nm and 520 nm. The quantu m yield of singlet oxygen increased with increasing concentration of o xygen. Using laser flash photolysis we studied the possible mechanism of singlet oxygen formation. The observed transient, with a broad abso rption spectrum peaking at around 440 nm, was identified as a triplet with lifetime ca 11 mu s. It was quenched by both molecular oxygen and p-carotene with concomitant formation of a p-carotene triplet state. These results indicate the potential role of hydrophobic components of lipofuscin in blue light-induced damage to the RPE. (C) 1998 Elsevier Science Inc.