title: Extracellular Signal-regulated Kinase Mitogen-activated Protein Kinase and Phosphatidylinositol 3-Kinase/Akt Signaling Are Required for Lipopolysaccharide-mediated Mineralization in Murine Odontoblast-like Cells.
abstract: BACKGROUND
  Odontoblasts play an important role in post-developmental control of mineralization in response to external stimuli in the tooth. The present study investigated whether lipopolysaccharide (LPS), a major bacterial cell wall component, influenced mineralization in a murine odontoblast-like cell (OLC) line and the related intracellular signaling pathways involved.
  
  
  METHODS
  Alizarin red S staining was used to assess mineralized nodule formation in OLCs in response to LPS. The effects of LPS on gene expression of odontoblastic markers were investigated by using quantitative real-time reverse-transcriptase polymerase chain reaction. The potential involvement of toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), or phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways in the mineralized nodule formation, and mRNA expression of several odontoblastic markers of OLCs induced by LPS was assessed by using alizarin red S staining and quantitative real-time reverse-transcriptase polymerase chain reaction. Moreover, LPS stimulation resulted in phosphorylation of protein that was determined by Western blot analysis.
  
  
  RESULTS
  OLCs showed reduced mineralized nodule formation and several odontoblastic markers expression in response to LPS exposure. Furthermore, inhibition of TLR4, extracellular signal-regulated kinase (ERK), and PI3K/Akt signaling noticeably antagonized LPS-mediated mineralization in OLCs. However, p38 MAPK, c-Jun N-terminal kinase, and NF-κB signaling inhibitors did not affect LPS-mediated mineralization in OLCs. Notably, LPS treatment resulted in a time-dependent phosphorylation of ERK and PI3K/Akt in OLCs, which was abrogated by their specific inhibitors.
  
  
  CONCLUSIONS
  LPS decreased mineralization in OLCs via TLR4, ERK MAPK, and PI3K/Akt signaling pathways, but not p38, c-Jun N-terminal kinase, or NF-κB signaling.
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an, PR China.
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an, PR China.
authors.forename: Fengle
authors.initials: F
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an, PR China.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an, PR China.
authors.forename: Zeyuan
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Department of Stomatology, Lishilu Outpatient Department, Chinese PLA Second Artillery Corps, Beijing, PR China.
authors.forename: Baogang
authors.initials: B
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an, PR China.
authors.forename: Xinyao
authors.initials: X
authors.lastname: He
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an, PR China; Department of Stomatology, NingXia People's Hospital, NingXia, Yinchuan, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an, PR China. Electronic address: hewenxi@fmmu.edu.cn.
authors.forename: Wenxi
authors.initials: W
authors.lastname: He
authors.affiliation: Oral Biology, School of Dentistry, University of Birmingham, Birmingham, West Midlands, United Kingdom.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Cooper
mesh_terms: D000818:Animals; D002460:Cell Line; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D009804:Odontoblasts / Q000187:drug effects* / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D051197:Toll-Like Receptor 4; D058539:Phosphatidylinositol 3-Kinase; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: Lipopolysaccharide; NF-κB; TLR4; mitogen-activated protein kinase; odontoblasts