title: Porphyromonas endodontalis lipopolysaccharides induce RANKL by mouse osteoblast in a way different from that of Escherichia coli lipopolysaccharide.
abstract: BACKGROUND
  Porphyromonas endodontalis lipopolysaccharide (LPS) has been shown to have a high positive rate in infected root canals and symptomatic apical periodontitis. It may play an integral role as a potent stimulator of inflammatory cytokines involved in apical lesions. The receptor activator of nuclear factor-κB ligand (RANKL) has been proven to be the key regulator of bone remodeling. This study investigated P. endodontalis LPS-induced RANKL production and LPS signaling in mouse osteoblasts.
  
  
  METHODS
  LPS-induced RANKL production in mouse osteoblast MC3T3-E1 cells was measured by Western blot and real-time polymerase chain reaction, and the Toll-like receptors (TLRs) were determined by the blocking test using anti-TLRs antibodies. In addition, specific inhibitors were used to analyze the intracellular signaling pathways. Escherichia coli LPS was used as the control.
  
  
  RESULTS
  Both of the anti-TLR2 and anti-TLR4 antibodies significantly (P < .05) inhibited the expression of RANKL from osteoblasts stimulated with P. endodontalis LPS; only anti-TLR2 antibody had a significant (P < .05) inhibitory effect on E. coli LPS signaling. SP600125 (c-Jun N-terminal kinase [JNK] inhibitor) prevented the up-regulation of RANKL expression in P. endodontalis LPS-infected osteoblasts (P < .05). The inhibitory effect of wortmannin (phosphatidylinositol 3-kinase inhibitor) and PD98059 (mitogen-activated protein kinase [MAPK]/extracellular signal-regulated kinase [ERK] kinase-1/2 [MEK 1/2] inhibitor) were observed in E. coli LPS-treated mouse osteoblasts (P < .05).
  
  
  CONCLUSIONS
  Results from this study showed that P. endodontalis LPS has the ability to promote the expression of RANKL in mouse osteoblasts, and this induction was mainly through the TLR2/4-JNK signaling pathway, a situation quite different from that of typical bacterial endotoxin (E. coli LPS).
authors.affiliation: State Key Laboratory of Oral Disease, West China School and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Tang
authors.forename: Feifei
authors.initials: F
authors.lastname: Sun
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Li
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhou
authors.forename: Shihai
authors.initials: S
authors.lastname: Yin
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
mesh_terms: D016475:3T3 Cells / Q000187:drug effects; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000502:physiology*; D005419:Flavonoids / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D008070:Lipopolysaccharides / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects*; D053244:Osteoprotegerin / Q000032:analysis; D000081082:Phosphoinositide-3 Kinase Inhibitors; D045202:Porphyromonas endodontalis / Q000502:physiology*; D053245:RANK Ligand / Q000187:drug effects*; D060888:Real-Time Polymerase Chain Reaction; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D000873:Anthracenes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008070:Lipopolysaccharides; D053244:Osteoprotegerin; D000081082:Phosphoinositide-3 Kinase Inhibitors; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C432165:pyrazolanthrone; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000077191:Wortmannin