title: Lipopolysaccharide-binding protein is vectorially secreted and transported by cultured intestinal epithelial cells and is present in the intestinal mucus of mice.
abstract: Lipopolysaccharide-binding protein (LBP) is an important modulator of the host's response to endotoxin. In a previous study, we found evidence for the synthesis of LBP by intestinal epithelial cells. In this study, we explored the polarity of LBP secretion by these cells. Polarized monolayers of Caco-2 cells were used as intestinal mucosa model. Cells were stimulated apically or basally with cytokines, and LBP secretion was analyzed. Furthermore, the presence of LBP in intestinal mucus of healthy and endotoxemic mice was studied using a mucus-sampling technique. The constitutive unipolar LBP secretion from the apical cell surface was markedly enhanced when cells were exposed to cytokines at their apical surface. However, bioactive LBP was secreted from both cell surfaces after basolateral stimulation of cells. Cytokines also influenced the secretion of the acute phase proteins serum amyloid A, apoA-I, and apoB from both surfaces of Caco-2 cells. Furthermore, transport of exogenous LBP from the basolateral to the apical cell surface was demonstrated. In line with these in vitro data, the presence of LBP in intestinal mucus was strongly enhanced in mice after a challenge with endotoxin. The results indicate that LBP is present at the mucosal surface of the intestine, a phenomenon for which secretion and transport of LBP by intestinal epithelial cells may be responsible.
authors.affiliation: Department of General Surgery, Maastricht University, Maastricht, The Netherlands.
authors.forename: A C
authors.initials: AC
authors.lastname: Vreugdenhil
authors.forename: A M
authors.initials: AM
authors.lastname: Snoek
authors.forename: J W
authors.initials: JW
authors.lastname: Greve
authors.forename: W A
authors.initials: WA
authors.lastname: Buurman
mesh_terms: D000209:Acute-Phase Proteins; D000818:Animals; D016632:Apolipoprotein A-I / Q000235:genetics / Q000378:metabolism; D001053:Apolipoproteins / Q000235:genetics / Q000378:metabolism; D001055:Apolipoproteins B / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics / Q000276:immunology; D018938:Caco-2 Cells / Q000276:immunology / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D016764:Cell Polarity / Q000235:genetics / Q000276:immunology; D019446:Endotoxemia / Q000276:immunology / Q000378:metabolism; D004731:Endotoxins / Q000494:pharmacology; D005822:Genetic Vectors / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D007419:Intestinal Secretions / Q000276:immunology / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism*; D008562:Membrane Glycoproteins; D051379:Mice; D009093:Mucus / Q000276:immunology / Q000378:metabolism*; D000685:Serum Amyloid A Protein / Q000235:genetics / Q000378:metabolism; D000099231:Lipopolysaccharide-Binding Protein
chemical_list: D000209:Acute-Phase Proteins; D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D001055:Apolipoproteins B; D002352:Carrier Proteins; D004731:Endotoxins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D000685:Serum Amyloid A Protein; D000099231:Lipopolysaccharide-Binding Protein