Inhibitory effect of Cladosiphon fucoidan on the adhesion of Helicobacter pylori to human gastric cells.

We studied the inhibitory effect of Cladosiphon fucoidan on the attachment of Helicobacter pylori (H. pylori), a gastroduodenal pathogen, to human gastric cell lines. The bacterial binding in these cell lines was inhibited more by Cladosiphon fucoidan (IC50 = 16-30 mg/mL), than by the fucoidan from Fucus (IC50 > 30 mg/mL). Dextran sulfate, another sulfated polysaccharide, did not inhibit the binding at all. Pre-incubating the bacterial suspension with fucoidans reinforced the inhibitory ability of these components, and reduced the IC50 value of Cladosiphon fucoidan to approximately 1 mg/mL. However, the binding was not inhibited by pre-treatment of gastric cells with these components. It was also shown that this fucoidan blocks both Leb- and sulfatide-mediated attachment of H. pylori to gastric cells. Furthermore, fucoidan-binding proteins were found on the H. pylori cell surface by Western blot analysis. Thus, the inhibitory effect exerted by Cladosiphon fucoidan on binding between H. pylori and gastric cells might result from the coating with this component of the bacterial surface.