title: Differential regulation of immune responses by odontoblasts.
abstract: Odontoblasts (OBs) are cells lining the inner surface of the tooth. Their potential role in host defenses within the tooth is suggested by their production of antimicrobial beta-defensins, but their role needs confirmation. The present study sought to define the roles of human OBs in microbial recognition and innate host responses. Toll-like receptor 2 (TLR2) and TLR4, as well as CCR6, were immunolocalized in human OBs and their dentinal processes in situ. To examine OB function we used organotypic tooth crown cultures to maintain human OBs within their dentin scaffold. Cells in the OB layer of cultured and non-cultured crown preparations expressed mRNA for several markers of innate immunity including chemokine CCL20, chemokine receptor CCR6, TLR2, TLR4 and the OB marker dentin sialophosphoprotein (DSPP). Expression of human beta-defensin 1 (hBD1), hBD2, hBD3, interleukin-8 (IL-8), and CCL20 increased with time in culture. Tooth crown odontoblast (TcOB) cultures were stimulated with agonist that was specific for TLR2 (Pam3CSK4) or TLR4 [Escherichia coli lipopolysaccharide (LPS)]. Nuclear factor-kappaB assays confirmed the TLR2 activity of Pam3CSK4 and the TLR4 activity of LPS. LPS up-regulated IL-1beta, tumor necrosis factor-alpha (TNF-alpha), CCL20, hBD2, IL-8, TLR2 and TLR4; however, Pam3CSK4 down-regulated these mRNAs. IL-1beta, TNF-alpha, CCL20 were also up-regulated from six-fold to 30-fold in TcOB preparations from decayed teeth. Our results show for the first time that OBs express microbial pattern recognition receptors in situ, thus allowing differential responses to gram-positive and gram-negative bacteria, and suggest that pro-inflammatory cytokines and innate immune responses in decayed teeth may result from TLR4 signaling.
authors.affiliation: Department of Oral Biology, University of Washington, Seattle, WA 98195, USA.
authors.forename: O
authors.initials: O
authors.lastname: Veerayutthwilai
authors.forename: M R
authors.initials: MR
authors.lastname: Byers
authors.forename: T-T T
authors.initials: TT
authors.lastname: Pham
authors.forename: R P
authors.initials: RP
authors.lastname: Darveau
authors.forename: B A
authors.initials: BA
authors.lastname: Dale
mesh_terms: D000938:Antigen-Presenting Cells / Q000276:immunology; D054418:Chemokine CCL20; D019742:Chemokines, CC / Q000032:analysis; D003731:Dental Caries / Q000276:immunology; D003804:Dentin / Q000166:cytology / Q000276:immunology; D016326:Extracellular Matrix Proteins / Q000032:analysis; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D053583:Interleukin-1beta / Q000032:analysis; D016209:Interleukin-8 / Q000032:analysis; D055666:Lipopeptides; D008070:Lipopolysaccharides / Q000494:pharmacology; D019402:Macrophage Inflammatory Proteins / Q000032:analysis; D009804:Odontoblasts / Q000276:immunology*; D009924:Organ Culture Techniques; D010455:Peptides / Q000494:pharmacology; D010750:Phosphoproteins / Q000032:analysis; D054399:Receptors, CCR6; D019707:Receptors, Chemokine / Q000032:analysis; D012795:Sialoglycoproteins / Q000032:analysis; D051195:Toll-Like Receptor 2 / Q000032:analysis / Q000037:antagonists & inhibitors; D051197:Toll-Like Receptor 4 / Q000032:analysis / Q000037:antagonists & inhibitors; D019228:Tooth Crown; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis; D023083:beta-Defensins / Q000032:analysis; D000099311:Dentin Sialophosphoprotein
chemical_list: D054418:Chemokine CCL20; D019742:Chemokines, CC; D016326:Extracellular Matrix Proteins; D053583:Interleukin-1beta; D016209:Interleukin-8; D055666:Lipopeptides; D008070:Lipopolysaccharides; D019402:Macrophage Inflammatory Proteins; D010455:Peptides; D010750:Phosphoproteins; D054399:Receptors, CCR6; D019707:Receptors, Chemokine; D012795:Sialoglycoproteins; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D023083:beta-Defensins; D000099311:Dentin Sialophosphoprotein; C108355:CCL20 protein, human; C106311:CCR6 protein, human; C406407:DEFB1 protein, human; C422950:DEFB103A protein, human; C106641:DEFB4A protein, human; C508075:Pam(3)CSK(4) peptide