title: Synergistic effect of tumor necrosis factor-alpha and interferon-gamma on enterocyte shedding of syndecan-1 and associated decreases in internalization of Listeria monocytogenes and Staphylococcus aureus.
abstract: Syndecan-1 is a heparan sulfate proteoglycan expressed on epithelia, and its ectodomain can be shed into the extracellular milieu, affecting a variety of cellular functions. Using two bacteria known to react with heparan sulfate, Listeria monocytogenes and Staphylococcus aureus, experiments were designed to clarify the effect of syndecan-1 shedding on bacterial internalization by human HT-29 enterocytes. Mature enterocytes were incubated with tumor necrosis factor (TNF)-alpha and/or interferon (IFN)-gamma for 16h prior to addition of bacteria. These cytokines acted synergistically to decrease syndecan-1 expression, assessed by visual observations of syndecan-1 expression on enterocytes using immunohistochemistry and a monoclonal antibody to the syndecan-1 core protein, by quantifying this fluorescent intensity, and by quantifying the concentration of shed syndecan-1 using an enzyme-linked immunoabsorbent assay. Neither IFN-gamma nor TNF-alpha alone had a noticeable effect on L. monocytogenes internalization, but a mixture of both cytokines resulted in decreased (P<0.01) internalization. Enterocyte preincubation with TNF-alpha alone, and with both cytokines, was associated with decreased S. aureus internalization, at P<0.05 and P<0.01, respectively. Thus, TNF-alpha and IFN-gamma acted synergistically to shed syndecan-1 ectodomains from HT-29 enterocytes, and shedding was associated with decreased internalization of two pathogenic bacteria, suggesting that syndecan-1 shedding may modulate the pathogenesis of specific microbes.
authors.affiliation: Department of Genetics, Cell biology and Development, University of Minnesota, Minneapolis, MN 55455-0374, USA.
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Henry-Stanley
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.forename: Stanley L
authors.initials: SL
authors.lastname: Erlandsen
authors.forename: Carol L
authors.initials: CL
authors.lastname: Wells
mesh_terms: D020895:Enterocytes / Q000187:drug effects* / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000187:drug effects*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D011509:Proteoglycans / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000187:drug effects*; D053668:Syndecan-1; D053667:Syndecans; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D008562:Membrane Glycoproteins; D011509:Proteoglycans; C508241:SDC1 protein, human; D053668:Syndecan-1; D053667:Syndecans; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma