title: The synergistic effect of peptidoglycan and lipopolysaccaride on osteoclast formation.
abstract: OBJECTIVE
  The purpose of this study was to investigate the mechanisms leading to periapical tissue destruction by the Gram-positive bacterial cell component, peptidoglycan (PGN) and Gram-negative bacterial cell component lipopolysaccaride (LPS).
  
  
  METHODS
  Osteoclast precursor RAW 264.7 cells were cultured with 50 ng/ml receptor activator of NF-kappaB ligand (RANKL) for 72 hours. RANKL was then removed and the cells were treated with various concentrations of PGN in the presence or absence of various concentration of LPS for an additional 48 hours. RT-PCR analysis was performed to examine the presence of receptors on osteoclasts known to be involved in mediating cellular activation in response to PGN (TLR2) and LPS (TLR 4).
  
  
  RESULTS
  PGN dose dependently and reproducibly stimulated TRAP-positive multinucleated osteoclast-like (OCL) cell formation. PGN and LPS had synergistic effects on the induction of OCL cell formation. Both unstimulated and RANKL-stimulated RAW 264.7 cells expressed TLR2 and TLR4 mRNA.
  
  
  CONCLUSIONS
  The results underscore the importance of considering both Gram-positive and Gram-negative bacteria when interpreting findings associated with primary and secondary periapical lesions.
authors.affiliation: Department of Endodontics, College of Dentistry, University of Florida, Gainesville 32610-0436, USA. jjiang@dental.ufl.edu
authors.forename: Jin
authors.initials: J
authors.lastname: Jiang
authors.forename: Jian
authors.initials: J
authors.lastname: Zuo
authors.forename: I Rita
authors.initials: IR
authors.lastname: Hurst
authors.forename: L Shannon
authors.initials: LS
authors.lastname: Holliday
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004926:Escherichia coli; D007527:Isoenzymes / Q000032:analysis; D008024:Ligands; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000032:analysis / Q000494:pharmacology; D051379:Mice; D016328:NF-kappa B / Q000494:pharmacology; D010010:Osteoclasts / Q000187:drug effects*; D010457:Peptidoglycan / Q000008:administration & dosage / Q000494:pharmacology*; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011956:Receptors, Cell Surface / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013211:Staphylococcus aureus; D000071681:Tartrate-Resistant Acid Phosphatase; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
chemical_list: D015415:Biomarkers; D002352:Carrier Proteins; D007527:Isoenzymes; D008024:Ligands; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D010457:Peptidoglycan; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011956:Receptors, Cell Surface; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase