BETA-CRYPTOXANTHIN UPTAKE IN RETINAL PIGMENT EPITHELIAL CELLS

Abstract

The retinal pigment epithelium (RPE) is a monolayer of cells located between choroid and the photoreceptors. RPE has a crucial role in the functioning of retina by providing oxygen and nutrients and by removing the debris and metabolites of photoreceptors. Retina is a tissue with a high metabolic rate and is subject to the aggression of the reactive oxygen species. Beta-cryptoxanthin is a lipophilic pigment widely found in the human diet and is one of the most important provitamin A compounds. In this study we investigated the ability of RPE cultured cells to incorporate β-cryptoxanthin in their free and esterified forms. Their effects on the cell viability and on cell antioxidant defence were also investigated. Carotenoids were delivered to the cell culture using small amounts of tetrahydrofuran added to the fetal calf serum. Two procedures were used for incorporation: adding carotenoids to the cell suspension (a) or to the confluent monolayer (b). The incorporation yield was determined by UV-Vis spectrophotometry after extraction from cell pellet, the cells viability by Trypan Blue (for incorporation experiment) and by MTT assay. The antioxidant effect was determined by intracellular ROS assay (DCF-DA). Human RPE cultured cells can incorporate the free form of β-cryptoxanthin with an incorporation yield of 7.91 % for the first procedure and 7.65 % for the second one. The viability of cells was higher for the second procedure (96.2 %) comparing with the first one (93.7 %). The concentration of β-cryptoxanthin in the cells tends to decrease in time for both procedures, being lower after 48 h and respectively 72 hours. The esterified form of β-cryptoxanthin can not be incorporated by RPE cells and has not strong influence on the cell viability. Administration of free β-cryptoxanthin at 10 μM has a positive effect on the cell viability for control and hydrogen peroxide pre-tretead cells. β-cryptoxanthin has an inhibitory effect on reactive oxygen species generation in the RPE cells when treated with hydrogen peroxide.