title: Sphingosine-1-phosphate mediates AKT/ERK maintenance of dental pulp homoeostasis.
abstract: OBJECTIVE
  To investigate the cell status of dental pulp cells (DPCs) in a sphingosine-1-phosphate (S1P)-induced microinflammation environment and the possible mechanisms of cell homoeostasis maintenance by S1P.
  
  
  METHODS
  Sphingosine-1-phosphate receptor (S1PR) expression was examined in DPCs within a local S1P-induced microinflammation model established using 1 μmol L(-1) S1P. U0126 [extracellular signal-regulated kinase (ERK) inhibitor], LY294002 (AKT inhibitor) and Y27632 (ROCK inhibitor) were used to inhibit corresponding signalling pathways of DPCs. CCK8 and cell cycle analysis tested cell proliferation. Immunofluorescence staining JC-1 detected changes of mitochondrial membrane potential (ΔΨm). Tests for apoptosis and the apoptosis-related proteins Bax and Bcl-2 were assessed by flow cytometry and western blot analysis, respectively. Expressions of ERK and AKT were evaluated by western blot analysis. The results were analysed using the Student's t-test and the significance level set at P < 0.05.
  
  
  RESULTS
  Expressions of S1PR1, S1PR2 and S1PR3 in DPCs differed amongst individuals. DPCs maintained self-homoeostasis in response to S1P-induced microinflammation via S1PRs. During this repair process, ERK, AKT and ROCK had a short-term complementary interaction at 60 min, but then AKT and ERK gradually played decisive roles after 24 h in proliferation enhancement and apoptosis inhibition, respectively (P > 0.05).
  
  
  CONCLUSIONS
  The AKT-ERK balance may determine whether DPC homoeostasis in S1P-induced microinflammation is maintained by synergistic regulation of cell growth and apoptosis.
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: H Y
authors.initials: HY
authors.lastname: Pan
authors.forename: H
authors.initials: H
authors.lastname: Yang
authors.forename: M Y
authors.initials: MY
authors.lastname: Shao
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: P
authors.initials: P
authors.lastname: Zhang
authors.forename: R
authors.initials: R
authors.lastname: Cheng
authors.forename: T
authors.initials: T
authors.lastname: Hu
mesh_terms: D000293:Adolescent; D000328:Adult; D000577:Amides / Q000494:pharmacology*; D017209:Apoptosis; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology*; D018929:Cell Culture Techniques; D049109:Cell Proliferation; D002867:Chromones / Q000494:pharmacology*; D003782:Dental Pulp / Q000166:cytology* / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008246:Lysophospholipids / Q000502:physiology*; D053078:Membrane Potential, Mitochondrial; D008964:Molar, Third; D009025:Morpholines / Q000494:pharmacology*; D009570:Nitriles / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000502:physiology
chemical_list: D000577:Amides; D002070:Butadienes; D002867:Chromones; D008246:Lysophospholipids; D009025:Morpholines; D009570:Nitriles; D011725:Pyridines; C113580:U 0126; C108830:Y 27632; C060506:sphingosine 1-phosphate; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D013110:Sphingosine
keywords: ERK/AKT; ROCK; S1P; apoptosis; microinflammation; proliferation