title: Effects of Enterococcus faecalis lipoteichoic acid on receptor activator of nuclear factor-κB ligand and osteoprotegerin expression in periodontal ligament fibroblasts.
abstract: OBJECTIVE
  To investigate the influence of Enterococcus faecalis lipoteichoic acid (LTA) on the key bone resorption-regulating proteins, receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) in human periodontal ligament fibroblasts (PDL cells).
  
  
  METHODS
  Periodontal ligament cells were subjected to various concentrations of LTA. Cell viability was then determined by methyl thiazolyl tetrazolium (MTT) assay, whilst the expression levels of RANKL and OPG were investigated by enzyme-linked immunosorbent assay (ELISA) and Western blotting. The effect of the inhibitors [IL-1 receptor-associated kinase (IRAK)-1/4, p38 mitogen-activated protein kinase (MAPK) (SB203580)] on LTA-stimulated RANKL/OPG activation was examined. Cell viability and RANKL/OPG ratio in PDL cells were also analysed by MTT assay and Western blotting. Data were analysed using one-way anova or t-test at a significance level of P = 0.05.
  
  
  RESULTS
  Cell viability was reduced significantly in the LTA group in a dose-dependent fashion (P < 0.05). In addition, LTA was found to upregulate the protein expression of RANKL, OPG and their relative ratio in PDL cells (P < 0.05). The optimal concentration of LTA used in PDL cells was determined to be 10 μg mL(-1) . Following IRAK1/4 and p38MAPK inhibition, LTA-stimulated increases of RANKL/OPG ratio were significantly reduced (P < 0.05).
  
  
  CONCLUSIONS
  Enterococcus faecalis LTA could upregulate the expression of RANKL and OPG at different rates, suggesting a potential role for LTA in the bone resorption process of refractory apical periodontitis through the regulation of RANKL and OPG. In addition, IRAK1/4 and p38MAPK signalling involving RANKL/OPG may contribute to inflammatory responses from PDL cells.
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.
authors.forename: L
authors.initials: L
authors.lastname: Zhao
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: L
authors.initials: L
authors.lastname: Cheng
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: J
authors.initials: J
authors.lastname: Du
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.forename: Z
authors.initials: Z
authors.lastname: Peng
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D013293:Enterococcus faecalis / Q000737:chemistry*; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology*; D006801:Humans; D008070:Lipopolysaccharides / Q000502:physiology*; D053244:Osteoprotegerin / Q000235:genetics / Q000378:metabolism*; D010513:Periodontal Ligament / Q000166:cytology / Q000378:metabolism*; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D013682:Teichoic Acids
chemical_list: D008070:Lipopolysaccharides; D053244:Osteoprotegerin; D053245:RANK Ligand; C505688:TNFSF11 protein, human; D013682:Teichoic Acids; C009900:lipoteichoic acid
keywords: IL-1 receptor-associated kinase; lipoteichoic acid; osteoprotegerin; p38 mitogen-activated protein kinase; periodontal ligament cells; receptor activator of nuclear factor-κB ligand