title: Pressure induces interleukin-6 expression via the P2Y6 receptor in human dental pulp cells.
abstract: OBJECTIVE
  An increase in intrapulpal pressure occurs during inflammation and restorative procedures; however, the role of the pressure on human dental pulp cell (HDPC) is not yet clarified. In this study, the effect of pressure on interleukin-6 (IL-6) expression of HDPCs was examined.
  
  
  METHODS
  HDPCs were applied with pressure (0.7-1.4 g/cm(2)). The level of IL-6 mRNA and protein release was determined by RT-PCR and ELISA, respectively. The signalling pathways were investigated using inhibitors, antagonists, and small interfering RNA.
  
  
  RESULTS
  The results showed that pressure up-regulated IL-6 mRNA expression and protein release in a time- and dose-dependent manner. The implication of P2Y receptor was exhibited by a significant inhibition of pressure-induced IL-6 expression by suramin, an antagonist for the non-specific purinergic receptor family. Using loss of function experiments, we showed MRS2578 (a specific P2Y6 antagonist), as well as P2Y6 small interfering RNA, abolished pressure-induced IL-6, whilst MRS2179 (a specific P2Y1 antagonist) and NF449 (a P2X1, P2X3, P2Y1, and P2Y2 antagonist) had no effect. Finally, we demonstrated that either the conditioned medium collected from pressurised dental pulp cells or addition of UDP, a selective agonist of P2Y6, up-regulated IL-6 expression in HDPCs.
  
  
  CONCLUSIONS
  These results indicate that pressure could induce IL-6 expression through the P2Y6 receptor in HDPCs, leading to a new insight of the role of pressure on cytokine release during pulpal inflammatory process.
authors.affiliation: Department of Anatomy, Faculty of Dentistry, Chulalongkorn University, Henri-Dunant Road, Pathumwan, Bangkok 10330, Thailand.
authors.forename: Sirichom
authors.initials: S
authors.lastname: Satrawaha
authors.forename: Suchart
authors.initials: S
authors.lastname: Wongkhantee
authors.forename: Prasit
authors.initials: P
authors.lastname: Pavasant
authors.forename: Piyamas
authors.initials: P
authors.lastname: Sumrejkanchanakij
mesh_terms: D000704:Analysis of Variance; D020013:Calcium Signaling; D017077:Culture Media, Conditioned; D003782:Dental Pulp / Q000166:cytology* / Q000378:metabolism*; D003799:Dental Stress Analysis; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis*; D008856:Microscopy, Fluorescence; D011312:Pressure; D011671:Pulpitis / Q000503:physiopathology; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D015854:Up-Regulation
chemical_list: D017077:Culture Media, Conditioned; D015850:Interleukin-6; D018048:Receptors, Purinergic P2; C099845:purinoceptor P2Y6