In a recent study published in the journal Frontiers, researchers evaluated the role of lutein nanodiscs against ultraviolet (UV) light-induced damage to retinal cells.
Study: Lutein nanodiscs protect human retinal pigment epithelial cells from UV light-induced damage. Image credit: Monet_3k/Shutterstock
Age-related macular degeneration (AMD) accounts for 8.7% of blindness worldwide. Studies have attributed this adverse impact to increased life expectancy, genetics, tobacco smoke, chronic inflammation, and oxidative stress. The most common form of AMD is the dry or non-exudative type caused by degeneration of the retinal pigment epithelial (RPE) cells, leading to the death of secondary photoreceptor cells and consequent loss of vision. There is an urgent need to develop therapies to restore vision in AMD patients.
About the study
In the present study, researchers demonstrated the efficacy of lutein nanodisc (ND) as a novel lutein delivery system against AMD-related UV light-induced damage.
The team evaluated the relative ability of the components of various ND formulations to affect the solubility of lutein in phosphate-buffered saline (PBS) using solubilization efficiency experiments. Specific ND components were incorporated with lutein, followed by removal of insoluble material to estimate lutein content. Furthermore, the impact of incorporating ND on the spectral aspects of lutein was evaluated by analyzing the UV/Vis absorbance spectra. In addition, the particle size of ND lutein was characterized by fast protein liquid chromatography (FPLC) gel filtration chromatography.
In addition, the efficiency of ND lutein as a delivery vehicle was estimated by incubating retinal pigment epithelial cells (ARPE-19) with media alone and only with media containing ND lutein and assaying for lutein.
results
The study showed that lutein showed complete solubility in solution mixtures containing PBS. The solubilization efficiency observed in solutions containing lutein together with recombinant human apolipoprotein (apoA-I) was 19%, while that of lutein with egg yolk phosphatidylcholine (EYPC) was 37%, while that the same in solutions containing lutein, apoA-I and EYPC was almost 90%. Therefore, only water-soluble ND lutein was developed when the formulation mixture consists of a bilayer with apolipoprotein and phospholipid scaffold protein.
UV/Vis absorbance spectra showed that in ethanol, lutein showed characteristic absorbance maxima when γ = 424, α = 445, and β = 472 nm. On the other hand, negligible absorbance was detected for this wavelength range in the ND control. The spectra corresponding to ND lutein resulted in a similar pattern to that observed for lutein in ethanol. In contrast to the values observed for lutein in an organic solvent, its characteristic absorbance maxima were red-shifted. The team noted that the red shift associated with the absorbance maxima of ND lutein with PBS, compared to free lutein with ethanol, was due to a variation in environmental conditions.
Chromatograms corresponding to ND lutein resulted in a major peak at 28 nm that eluted from 8.2 to 10.2 mL with a minor absorbance peak that eluted from 12.2 to 14.2 mL. The main peak detected had 99% lutein, while more than 99% of the phospholipid was detected in the main absorbance peak. This elution pattern suggested that the minor absorbance peak corresponded to apoA-I that was not incorporated into the ND, and the major peak was associated with the ND lutein. Comparison of this major peak with protein standards revealed a particle size between 200 kDa and 300 kDa. FPLC showed a homogeneous population of NDs in the ND formulation mixture.
Furthermore, incubation of ARPE-19 with control and lutein containing ND media showed that the latter had 35% ± 13.4% more lutein per mg of cell protein than the former. In addition, cell viability measurements found that cells incubated with control media had a marked decrease in cell viability. In contrast, cells incubated with ND lutein had a lutein concentration-dependent elevation of cell viability. Furthermore, incubation of ARPE-19 cells without EYPC rHDL (reconstituted high-density lipoprotein) with 2 hours of exposure to UV irradiation resulted in an approximately 50% reduction in cell viability. On the other hand, UV irradiation of ARPE1-9 cells after ND lutein incubation showed cell viability comparable to that observed in the absence of UV light.
Overall, the results of the study showed that the incorporation of lutein into the nanodiscs significantly improved the solubility of lutein. In addition, delivery of lutein via ND lutein to retinal pigment epithelial cells resulted in increased lutein content in the cells.