Fucoidan directly regulates the chemotaxis of canine peripheral blood polymorphonuclear cells by activating F-actin polymerization.

Fucoidan was recently shown to enhance innate immune functions. The objective of this study was to examine the direct stimulatory effect of fucoidan on the chemotactic activity of canine peripheral blood polymorphonuclear cells (PMNs). The chemotactic activity of PMNs was evaluated in a modified Boyden chamber assay and total cellular filamentous (F)-actin levels were measured using a flow cytometer. The chemotactic response of PMNs was increased by exposure to recombinant canine (rc) interleukin (IL)-8. In vitro treatment with fucoidan increased the chemotactic activity of PMNs in response to rcIL-8 compared with that of untreated PMNs, and also stimulated total cellular F-actin polymerization. The increased chemotactic activity of fucoidan-treated PMNs was suppressed by cytochalasin D, an inhibitor of F-actin polymerization. These results suggest that fucoidan directly regulates PMN chemotaxis, and that this effect is associated with an increase in actin polymerization.