title: Lipopolysaccharide enhances decorin expression through the Toll-like receptor 4, myeloid differentiating factor 88, nuclear factor-kappa B, and mitogen-activated protein kinase pathways in odontoblast cells.
abstract: BACKGROUND
  Lipopolysaccharide (LPS) has been shown to regulate the function of odontoblasts. However, the molecular mechanisms of the effect of LPS on odontoblasts are poorly understood. Decorin (DCN), one of the major matrix proteoglycans, is known to affect the mineralization of teeth. In this study, we investigated whether LPS can regulate the expression of DCN in odontoblasts and determined the intracellular signaling pathways triggered by LPS.
  
  
  METHODS
  The DCN messenger RNA and protein expression changes in mouse odontoblast-lineage cells (OLCs) were detected by real-time polymerase chain reaction (PCR) analysis and enzyme-linked immunosorbent assay (ELISA). Whether TLR4, myeloid differentiating factor 88 (MyD88), nuclear factor-kappa B (NF-κB), or mitogen-activated protein kinase (MAPK) pathways were involved in the LPS-induced DCN expression was determined by examined real-time PCR, ELISA, and luciferase activity assay. The activation of extracellular signal-regulated kinase (ERK), p38, and JNK in OLCs was measured by Western blot analysis.
  
  
  RESULTS
  We found that the mouse OLCs expressed DCN. DCN messenger RNA was rapidly induced by LPS in a time- and dose-dependent manner. Pretreatment with a MyD88 inhibitory peptide, a TLR4 antibody, or a specific inhibitor for NF-κB or I Kappa B alpha (IκBα) significantly inhibited LPS-induced DCN expression. Moreover, the LPS-mediated increase in κB-luciferase activity in OLCs was suppressed by the overexpression of dominant negative mutants of TLR4, MyD88, and IκBα but not by a dominant negative mutant of TLR2. In addition, LPS stimulation activated the ERK, p38, and JNK MAPK pathways. The pretreatment of OLCs with specific inhibitors of the ERK, p38, and JNK MAPK pathways markedly offset the LPS-induced up-regulation of DCN expression.
  
  
  CONCLUSIONS
  Our results show that LPS stimulation can up-regulate the gene expression of DCN via the TLR4, MyD88, NF-κB, and MAPK pathways in odontoblast cells.
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, The Fourth Military Medical University, Xian, China. hewenxi@fmmu.edu.cn
authors.forename: Wenxi
authors.initials: W
authors.lastname: He
authors.forename: Tiejun
authors.initials: T
authors.lastname: Qu
authors.forename: Qing
authors.initials: Q
authors.lastname: Yu
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Wang
authors.forename: Hanguo
authors.initials: H
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Smith
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D058575:Decorin / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000032:analysis; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008156:Luciferases; D049408:Luminescent Agents; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000032:analysis; D053594:Myeloid Differentiation Factor 88 / Q000037:antagonists & inhibitors / Q000187:drug effects*; D052002:NF-kappa B p50 Subunit / Q000037:antagonists & inhibitors / Q000187:drug effects*; D009570:Nitriles / Q000494:pharmacology; D009804:Odontoblasts / Q000187:drug effects*; D011725:Pyridines / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D013997:Time Factors; D051195:Toll-Like Receptor 2 / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000187:drug effects*; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000032:analysis
chemical_list: D000873:Anthracenes; D002070:Butadienes; C546879:Dcn protein, mouse; D058575:Decorin; D004791:Enzyme Inhibitors; D007093:Imidazoles; D008070:Lipopolysaccharides; D049408:Luminescent Agents; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D052002:NF-kappa B p50 Subunit; D009570:Nitriles; D011725:Pyridines; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C113580:U 0126; C073701:Nfkb1 protein, mouse; C432165:pyrazolanthrone; D008156:Luciferases; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580