Regulation of epithelial syndecan-1 expression by inflammatory cytokines

Syndecan-1 is expressed on the basolateral surface of columnar epithelium and contributes to wound repair by facilitating increased growth factor binding. Inflammatory bowel disease (IBD) is associated with reduced syndecan-1 expression in areas of inflamed mucosa that is likely to impair mucosal healing. Reduced syndecan-1 expression in IBD may be related to the presence of increased inflammatory cytokines. To test this hypothesis, monolayers of HT29 and T84 colonic epithelial cells were stimulated with tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta or IL-6. Stimulation of HT29 cells with TNF-alpha and IL-1beta resulted in reversible down-regulation of syndecan-1 at both protein and mRNA levels but little effect was observed with IL-6. Loss of syndecan-1 expression was caused by shedding of the ectodomain as revealed by increased levels of soluble syndecan-1 measured in the conditioned medium of stimulated cells. No increase in cytoplasmic staining accompanied the loss of cell surface syndecan-1 expression. TNF-alpha and IL-1beta are capable of down-regulating syndecan-1 expression and may account in part for the reduced expression of syndecan-1 seen in IBD.