Modulation of platelet aggregation-related eicosanoid production by dietary F-fucoidan from brown algaLaminaria japonicain human subjects

Abstract

Laminaria japonicais traditionally eaten in Japan as a beneficial food for thrombosis. The alga contains two specific ingredients, a xanthophyll fucoxanthin (FX) and a polysaccharide, F-fucoidan (FD). The aim of the present study was to investigate whether FX or FD exhibited anti-thrombotic effects. For this purpose, three types of capsules, containing 1 mg FX, 400 mg fucoidan, and both, were prepared from the alga and administered to volunteers for 5 weeks. The dose of FD or FD+FX significantly shortened lysis time (LT) of the thrombus measured by a global thrombosis test in the blood, but FX did not. Examining the mechanism, dietary FD increased H₂O₂and the secretion of prostacyclin (PGI₂), a potent inhibitor of platelet aggregation, in the blood, although FD was under the detection limit in the blood, determining with its monoclonal antibody. Furthermore, in mouse experiments, dietary FD was totally excreted into the faeces and was not incorporated into the blood. We then employed a co-culture system of a Caco-2 cell monolayer with fresh human blood. The addition of FD to Caco-2 cells stimulated the expression of NADPH oxidase 1 (NOX1) and dual oxidase 2 (DUOX2) mRNA and secreted H₂O₂onto the blood side accompanied by a significant increase in serum PGI₂production. These effects were invalidated by the combined addition of FD with its monoclonal antibody. The results suggested that dietary FD stimulated the expression of H₂O₂-producing enzymes in intestinal epithelial cells and released H₂O₂into the blood, which played a signalling role to increase PGI₂production and then shortened LT for thrombi.