LUTEIN AND ZEAXANTHIN UPTAKE IN CULTURED RETINAL PIGMENTED EPITHELIAL CELLS
Abstract
The retinal pigment epithelium (RPE) has the essential role of providing oxygen and nutrients to the photoreceptors but also to removes their debris and metabolites. The RPE is subject to continuously and high level of oxidative stress. RPE use endogenous enzymatic and non-enzymatic antioxidants as a mechanism of reactive oxygen species (ROS) detoxification. RPE is also particularly rich in non-enzymatic antioxidants such are tocopherols, ascorbic acid, lutein and zeaxanthin. In this study we investigated the ability of RPE cultured cells to incorporate lutein and zeaxanthin, in free and esterified forms, the carotenoid effect on cell culture viability and on cell antioxidant defense. Carotenoids were delivered to the cell culture using small amounts of tetrahydrofuran added to the fetal calf serum. The incorporation yield was determined by UV-Vis spectrophotometry, the cells viability by MTT assay and the antioxidant effect by intracellular ROS assay (DCF-DA). Human RPE cultured cells can incorporate the major dietary carotenoids, lutein and zeaxanthin. The highest incorporation yield was found for zeaxanthin, with 8.1 % of incorporation yield, while lutein incorporation yield was 7.12 %. Esterified xanthophylls can not be incorporated into RPE cells. Lutein and zeaxanthin administrated to RPE cells does not significantly influence the cell viability. They showed a small positive effect on the cell viability in a concentration of 10 μM in the culture media. Lutein and zeaxanthin have an inhibitory effect on reactive oxygen species generation in the RPE cells
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