gms | German Medical Science

Objectives: Lipopolysaccharide (LPS) can cause a persistent state of inflammation interfering with osseointegration of orthopaedic devices even after the eradication of the initial germ. LPS activates the migration of monocytes from the peripheral blood into the adjacent tissue as well as their differentiation to osteoclasts. In this context the endothelial lining of blood vessels forms a critical barrier regulating the inflammatory process and represents a target for therapeutical intervention. Recent studies suggest that fucoidans, sulfated and fucose rich polysaccharides from brown seaweed exhibit anti-inflammatory properties. However, the biological effects of fucoidans are depending on their purity and their chemical properties, such as molecular weight and sulfation degree. In this study we investigated the impact of purified fucoidans on endothelial cells during LPS induced inflammation.

Methods: Fucoidan was extracted enzymatically from Fucus evanescens and fractionated using ion exchange chromatography. The bioactivity of the purest fraction, FE_F3, with the highest sulfate and fucose content was compared to commercially available crude fucoidan from Fucus vesiculosus. Outgrowth endothelial cells (OEC) derived from peripheral blood were treated with 10 or 100 ug/ml fucoidan for 5 days. On day 6 cells were treated with 100 ng/ml LPS while fucoidan treatment was continued for 48 hours to assess the impact of fucoidans on endothelial cells in monoculture. Further, a co-culture-system of OEC and monocytes was applied to study the endothelial and inflammatory cell interaction. 24 hours after LPS treatment of OEC, monocytes isolated from the blood were added and co-culture was continued for 48 hours. Cells were fixed for immunocytochemistry and cell lysates and supernatants were collected for qPCR and ELISA. Experiments were performed for 3 different donors and statistical significance was determined with the one-way-ANOVA.

Results and Conclusion: Both extracts reduced the inflammatory response in the mono- and co-culture systems. This was associated with a decrease of IL-6 and ICAM-1 on gene and protein level and a reduced expression of TLR-4, CXCR4 and NF-kB. Immunocytochemistry and qPCR analysis demonstrated that treatment with fucoidan decreased the expression of selectins. The adhesion of monocytes to the endothelial monolayer was impaired after fucoidan treatment which was proven by a reduced expression of the monocyte surface markers CD11b and CD68. Our data indicate that fucoidans reduce the inflammatory response of endothelial cells in case of LPS induced bacterial infections. Purified FE_F3 showed a higher biological activity than crude fucoidan and required a ten times lower concentration to significantly reduce the inflammatory mediators.