Solubility, uptake and biocompatibility of lutein and zeaxanthin delivered to cultured human retinal pigment epithelial cells in tween40 micelles

Carotenoids lutein and zeaxanthin are proposed to protect ocular tissues from free-radical damage that can cause cataract and age-related macular degeneration (AMD). They accumulate selectively in the lens and macular region of the retina. Changes in the retinal pigment epithelium are characteristic in AMD. Efficient uptake is essential to study the intracellular effects of carotenoids in cell cultures. For in vitro experiments carotenoids are often dissolved in organic solvents like tetrahydrofuran (THF), dimethylsulfoxide (DMSO) and n-hexane, but difficulties have been associated with these application methods. Recently, O'Sullivan et al. (SM O'Sullivan et al., Br J Nutr 91 (2004) 757) developed a method whereby carotenoids could be delivered to cultured cells without the cytotoxic side effects often observed when organic solvents are used. We modified this method and investigated the effects of different carotenoid-formulations (ethanol/Tween40, methanol/tween40 and acetone/Tween40) on the uptake of lutein and zeaxanthin by differentiated ARPE-19 cells, cell viability and the expression of the "stress" gene HO-1, which is easily induced by a range of stimuli including chemical and physical agents. Micelle formulations prepared with ethanol/Tween40 resulted in the lowest LDH release, the highest carotenoid uptake and the lowest stress response (changes in HO-1 mRNA expression).