Effects of Sulfated Fucans from Laminaria hyperborea Regarding VEGF Secretion, Cell Viability, and Oxidative Stress and Correlation with Molecular Weight

Abstract

Background: Sulfated fucans show interesting effects in the treatment of ocular diseases (e.g., age-related macular degeneration), depending on their chemical structure. Here, we compared three purified sulfated fucans from Laminaria hyperborea (LH) regarding cell viability, oxidative stress protection, and vascular endothelial growth factor (VEGF) secretion in ocular cells. Methods: High-molecular-weight sulfated fucan (Mw = 1548.6 kDa, Fuc1) was extracted with warm water and purified through ultrafiltration. Lower-molecular-weight samples (Mw = 499 kDa, Fuc2; 26.9 kDa, Fuc3) were obtained by mild acid hydrolysis of ultrapurified sulfated fucan and analyzed (SEC-MALS (Size-exclusion chromatography-Multi-Angle Light Scattering), ICP-MS, and GC). Concentrations between 1 and 100 µg/mL were tested. Cell viability was measured after 24 h (uveal melanoma cell line (OMM-1), retinal pigment epithelium (RPE) cell line ARPE-19, primary RPE cells) via MTT/MTS (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide/3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Oxidative stress protection was determined after 24 h (OMM-1, ARPE-19). VEGF secretion was analyzed via ELISA after three days (ARPE-19, RPE). Results: Fuc2 and Fuc3 were antiproliferative for OMM-1, but not for ARPE. Fuc1 protected OMM-1. VEGF secretion was lowered with all fucans except Fuc3 in ARPE-19 and RPE. The results suggest a correlation between molecular weight and biological activity, with efficiency increasing with size. Conclusion: The LH sulfated fucan Fuc1 showed promising results regarding VEGF inhibition and protection, encouraging further medical research.

Effects of a Newly Developed Enzyme-Assisted Extraction Method on the Biological Activities of Fucoidans in Ocular Cells

“…Some of the FE fucoidans also had a slight additional toxic effect at 50 and 100 µg/mL, while 10 µg/mL FE_SAT2ad, FE_SiAT2ad and FE_SiAT3ad had a minimal protective effect. FE fucoidan at 10 µg/mL seems to be the best concentration concerning oxidative stress protection, but the effects are small and not relevant, corresponding to the fact that ARPE-19 are rather resistant against oxidative stress on their own and are hardly affected by fucoidan extracts [17,19]. SL_F2 and SL_F3 at concentrations of 50 µg/mL slightly decreased cell viability significantly down to 47% ± 3, p < 0.05 and 49% ± 2%, p < 0.05, respectively compared to 54% ± 3% stress control, but this not likely to be biological relevant.…”

“…This study is the continuation of fucoidan research within the EU FucoSan project in regards to finding a possible treatment for AMD [16][17][18][19]. One main goal of this international project is to characterize different fucoidans to choose the best fucoidan for a potential medical application.…”

“…We could show that fucoidans from SL and LH (extracted with hot water extraction followed by CaCl 2 precipitation and ultrafiltration or dialysis) showed the most promising effects of the species tested so far. In addition, high-molecular weight correlates with beneficial activities relevant for AMD [17,19]. Another study, testing fucoidan of FE, gave first indication that purity is an important factor for the relevant biological activities [18].…”

“…We showed already promising effects of different fucoidans on ocular cells. In brief, fucoidans from past studies were extracted with hot water, followed by precipitation with CaCl 2 and ultrafiltration or dialysis [16][17][18][19]. Fucus vesiculosus fucoidan from Sigma-Aldrich can reduce angiogenesis and VEGF of RPE [13].…”

“…evanescens (FE) were protective against oxidative stress in the uveal melanoma cell line OMM-1 and could inhibit ARPE-19 VEGF production [19] exactly like a other Saccharina latissima fucoidan, which was protective in ARPE-19 and lowered VEGF of primary RPE [19]. Different sized fucoidans from Laminaria hyperborea showed that the large, non-degraded fucoidan is most suitable for oxidative stress protection and VEGF inhibition [17]. Moreover, the tested fucoidans are not antiproliferative for ocular cells in general [16], which is necessary for use in medical treatments.…”