title: MD-2 controls bacterial lipopolysaccharide hyporesponsiveness in human intestinal epithelial cells.
abstract: Intestinal epithelial cells (IEC) have adapted to the presence of commensal bacteria through a state of tolerance that involves a limited response to lipopolysaccharide (LPS). Low or absent expression of two LPS receptor molecules, the myeloid differentiation (MD)-2 receptor, and toll-like receptor (TLR)4 was suggested to underlie LPS tolerance in IEC. In the present study we performed transfections of TLR4 and MD-2 alone or combined in different IEC lines derived from intestinal cancer (Caco-2, HT-29, and SW837). We found that LPS responsiveness increased more than 100-fold when IEC were transfected with MD-2 alone, but not TLR4. The release of interleukin (IL)-8, but also the expression of cyclooxygenase (Cox-)2 and the related secretion of prostaglandin (PG)E2 were coordinately stimulated by LPS in IEC transfected with MD-2 alone. Supernatants collected from MD-2-transfected IEC supported LPS activation of naïve HT-29, providing additional support to the concept that MD-2 alone endows IEC with LPS responsiveness. LPS responsiveness detected at concentrations as low as 110 pg/ml, and maximal values obtained by 10 ng/ml were clearly beyond those evoked by classical stimuli as IL-1beta. In polarized cells, apical LPS stimulation was markedly more efficient than basolateral. Our data contradict previous opinion that both TLR4 and MD-2 limit IEC response to LPS, and emphasize the prominent role of MD-2 in intestinal immune responses to Gram-negative bacteria.
authors.affiliation: INSERM U538, Centre Hospitalo-Universitaire Saint Antoine, Paris, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Lenoir
authors.forename: Catherine
authors.initials: C
authors.lastname: Sapin
authors.forename: Alexis H
authors.initials: AH
authors.lastname: Broquet
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Jouniaux
authors.forename: Sabine
authors.initials: S
authors.lastname: Bardin
authors.forename: Isabelle
authors.initials: I
authors.lastname: Gasnereau
authors.forename: Ginette
authors.initials: G
authors.lastname: Thomas
authors.forename: Philippe
authors.initials: P
authors.lastname: Seksik
authors.forename: Germain
authors.initials: G
authors.lastname: Trugnan
authors.forename: Joëlle
authors.initials: J
authors.lastname: Masliah
authors.forename: Maria
authors.initials: M
authors.lastname: Bachelet
mesh_terms: D000873:Anthracenes / Q000494:pharmacology; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000096:biosynthesis; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005434:Flow Cytometry; D015870:Gene Expression; D019073:HT29 Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D016209:Interleukin-8 / Q000378:metabolism; D007422:Intestines / Q000473:pathology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051218:Lymphocyte Antigen 96 / Q000235:genetics / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000502:physiology; D014162:Transfection
chemical_list: D000873:Anthracenes; D004791:Enzyme Inhibitors; D007093:Imidazoles; D016209:Interleukin-8; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D016328:NF-kappa B; D011725:Pyridines; D012333:RNA, Messenger; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C432165:pyrazolanthrone; D051546:Cyclooxygenase 2; D020928:Mitogen-Activated Protein Kinases; D015232:Dinoprostone; C093642:SB 203580