title: Lipoteichoic Acid of Enterococcus faecalis Inhibits the Differentiation of Macrophages into Osteoclasts.
abstract: BACKGROUND
  Enterococcus faecalis is associated with persistent endodontic infection and refractory apical periodontitis. Recently, we have shown that heat-killed E. faecalis attenuates osteoclast differentiation. Because lipoteichoic acid (LTA) is a major virulence factor of gram-positive bacteria, we investigated the effect of LTA from E. faecalis (EfLTA) on osteoclast differentiation.
  
  
  METHODS
  EfLTA was purified through organic solvent extraction, hydrophobic interaction column chromatography, and ion exchange column chromatography. Bone marrow cells from C57BL/6 or Toll-like receptor 2-deficient mice were incubated with macrophage colony-stimulating factor (M-CSF) for 5 days to generate macrophages (bone marrow-derived macrophages [BMMs]). The cells were differentiated into osteoclasts with M-CSF and receptor activator of NF-κB ligand (RANKL) in the presence or absence of EfLTA. The degree of osteoclast differentiation was determined by tartrate-resistant acid phosphatase staining. The expression of NFATc1 and c-Fos transcription factors was determined by Western blotting. A phagocytosis assay was performed by measuring the uptake of carboxyfluorescein diacetate succinimidyl ester-stained E. faecalis. An enzyme-linked immunosorbent assay was used to determine the amount of cytokines and chemokines.
  
  
  RESULTS
  When BMMs were treated with EfLTA, osteoclast differentiation was attenuated. EfLTA inhibited the RANKL-induced expression of NFATc1 and c-Fos. EfLTA inhibition of osteoclast differentiation was not observed in TLR2-deficient BMMs. In addition, EfLTA sustained the phagocytic capacity of BMMs even after the differentiation into osteoclasts, whereas it induced the expression of inflammatory cytokines and chemokines.
  
  
  CONCLUSIONS
  EfLTA inhibits the differentiation of macrophages into osteoclasts and thereby maintains the phagocytic and inflammatory capacities of macrophages, potentially contributing to refractory apical periodontitis.
authors.affiliation: Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jihyun
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Ok-Jin
authors.initials: OJ
authors.lastname: Park
authors.affiliation: Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jiseon
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jung Eun
authors.initials: JE
authors.lastname: Baik
authors.affiliation: Department of Agricultural Biotechnology and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea; Institute of Green Bio Science Technology, Seoul National University, Pyeongchang, Republic of Korea.
authors.forename: Cheol-Heui
authors.initials: CH
authors.lastname: Yun
authors.affiliation: Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul, Republic of Korea. Electronic address: shhan-mi@snu.ac.kr.
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Han
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D018925:Chemokines / Q000032:analysis / Q000096:biosynthesis; D016207:Cytokines / Q000032:analysis / Q000096:biosynthesis; D013293:Enterococcus faecalis / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D010587:Phagocytosis; D013682:Teichoic Acids / Q000494:pharmacology*; D014157:Transcription Factors / Q000096:biosynthesis
chemical_list: D018925:Chemokines; D016207:Cytokines; D008070:Lipopolysaccharides; D013682:Teichoic Acids; D014157:Transcription Factors; C009900:lipoteichoic acid
keywords: Chemokine; Enterococcus faecalis; cytokine; lipoteichoic acid; osteoclast differentiation; phagocytosis