Interaction of High-Molecular Weight Fucoidan from Laminaria hyperborea with Natural Functions of the Retinal Pigment Epithelium

Fucoidans are polysaccharides and constituents of cell walls of brown algae such as Laminaria hyperborea (LH). They exhibit promising effects regarding age-related macular degeneration (AMD). However, the safety of this compound needs to be assured. The focus of this study lies on influences of an LH fucoidan on the retinal pigment epithelium (RPE). The high-molecular weight LH fucoidan Fuc1 was applied to primary porcine RPE cells, and a tetrazolium (MTT) cell viability assay was conducted. Further tests included a scratch assay to measure wound healing, Western blotting to measure expression of retinal pigment epithelium-specific 65 kDa protein (RPE65), as well as immunofluorescence to measure uptake of opsonized fluorescence beads into RPE cells. Lipopolysaccharide was used to proinflammatorily activate the RPE, and interleukin 6 (IL-6) and interleukin 8 (IL-8) secretion was measured. RPE/choroid cultures were used to assess vascular endothelial growth factor (VEGF) secretion. Real-time polymerase chain reaction (real-time PCR) was performed to detect the gene expression of 91 different genes in a specific porcine RPE gene array. Fuc1 slightly reduced wound healing, but did not influence cell viability, phagocytosis or RPE65 expression. Fuc1 lowered IL-6, IL-8 and VEGF secretion. Furthermore, Fuc1 did not change tested RPE genes. In conclusion, Fuc1 does not impair RPE cellular functions and shows antiangiogenic and anti-inflammatory activities, which indicates its safety and strengthens its suitability concerning ocular diseases.