title: Effect of Enterococcus faecalis lipoteichoic acid on apoptosis in human osteoblast-like cells.
abstract: BACKGROUND
  Enterococcus faecalis is commonly detected in persistent apical periodontitis characterized by unimproved periradicular bone resorption. The aim of the present study was to examine the effect of lipoteichoic acid (LTA), a major virulence factor of E. faecalis, on apoptosis of osteoblasts.
  
  
  METHODS
  Human osteoblast-like MG63 cells were treated with LTA from E. faecalis at a series of concentrations for 48 hours. The proliferation of the MG63 cells was assessed by 3-(4,5-dimethyl-thiazol-2-yl)-2,5- diphenyl-tetrazolium bromide assay. To examine the apoptosis, the LTA-treated cells were analyzed by flow cytometry by using annexin V-fluorescein isothiocyanate and propidium iodide double staining. Hoechst 33258 staining was performed to observe the morphologic changes of the cells. To investigate the apoptosis at the molecular level, the protein levels of Bcl-2 and Bax were determined by Western blot. Meanwhile, the caspase-3 activity was detected with caspase colorimetric protease assay.
  
  
  RESULTS
  The proliferation of MG63 cells was inhibited by E. faecalis LTA in a dose-dependent manner. Flow cytometry assay indicated that LTA had a stimulating effect on MG63 cell apoptosis. Typical morphologies of apoptotic cells were observed under fluorescence microscope. Furthermore, the cell apoptosis was confirmed by (1) the down-regulation of the antiapoptotic protein (Bcl-2), (2) the up-regulation of the proapoptotic protein (Bax), and (3) the elevated caspase-3 activity.
  
  
  CONCLUSIONS
  LTA of E. faecalis could inhibit the proliferation and induce apoptosis of human osteoblast-like MG63 cells.
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School and Hospital of Stomatology and Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, China.
authors.forename: Yaguang
authors.initials: Y
authors.lastname: Tian
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Zhang
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Zhi
authors.initials: Z
authors.lastname: Song
authors.forename: Runfu
authors.initials: R
authors.lastname: Wang
authors.forename: Shuheng
authors.initials: S
authors.lastname: Huang
authors.forename: Zhengmei
authors.initials: Z
authors.lastname: Lin
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000187:drug effects; D018929:Cell Culture Techniques; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D013293:Enterococcus faecalis / Q000502:physiology*; D005456:Fluorescent Dyes; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D010006:Osteoblasts / Q000187:drug effects*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects; D013682:Teichoic Acids / Q000494:pharmacology*; D037521:Virulence Factors / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000187:drug effects
chemical_list: C494826:BAX protein, human; D005456:Fluorescent Dyes; D008070:Lipopolysaccharides; D019253:Proto-Oncogene Proteins c-bcl-2; D013682:Teichoic Acids; D037521:Virulence Factors; D051028:bcl-2-Associated X Protein; C009900:lipoteichoic acid; C505407:CASP3 protein, human; D053148:Caspase 3