Inhibition of selectin function and leukocyte rolling protects against dextran sodium sulfate-induced murine colitis

The selectin family of adhesion molecules (P-, E- and L-selectin) plays an important role in inflammatory reactions by mediating interactions between leukocytes and activated endothelial cells. However, a recent study using gene-targeted mice has suggested that adhesion molecules (P- and E-selectin and ICAM-1) may not be relevant targets in intestinal inflammation. The objective of the present study was to re-evaluate the potential role of selectins in experimental colitis in wild-type mice using the polysaccharide fucoidan, which inhibits the function of P- and L-selectin.

For this purpose, Balb/c mice were exposed to 5% dextran sodium sulfate (DSS) in the drinking water for 5 days with and without daily administration of fucoidan (25 mg/kg, i.v.). In separate experiments, the effect of fucoidan on leukocyte-endothelium interactions was examined by use of intravital microscopy.

It was found that pretreatment with fucoidan (25 mg/kg/day) reduced mucosal damage and crypt destruction in the colon of DSS-treated mice. Moreover, this fucoidan treatment markedly reduced the colonic MPO activity in mice exposed to DSS. In vivo microscopy revealed that the dose of fucoidan used in the present study abolished TNF-alpha-induced venular leukocyte rolling and extravascular recruitment.

These results suggest that selectins mediate leukocyte infiltration and tissue damage in experimental colitis. Moreover, our data support the concept that functional interference with adhesion molecules of the selectin family may have a beneficial effect in the treatment of inflammatory bowel disease.