title: Thermal stimulation of TRPV1 up-regulates TNFα expression in human periodontal ligament cells.
abstract: OBJECTIVE
  We previously demonstrated that the activation of transient receptor potential vanilloid 1 (TRPV1), a nociceptive ion channel receptor, by capsaicin led to the up-regulation of the osteoprotegerin (OPG)/receptor activator of nuclear factor kappa B ligand (RANKL) ratio in human periodontal ligament (HPDL) cells. Since TRPV1 is recognised as one of the thermo-sensitive cation channels, this study investigated the response of TRPV1 to thermal stimulation in HPDL cells.
  
  
  METHODS
  HPDL cells were incubated at 45°C for thermal stimulation. The mRNA expression of OPG, RANKL, tumour necrosis factor α (TNFα), and interleukin-1 β (IL-1β) was determined by using RT-PCR. OPG secretion and RANKL protein expression were analysed by ELISA and Western blot analysis, respectively. The mechanisms of heat-induced TNFα expression were studied using several TRPV1 inhibitors.
  
  
  RESULTS
  In contrast to capsaicin, thermal stimulation had no effect on OPG or RANKL expression. Interestingly, the mRNA expression of TNFα, but not IL-1β, was increased by heat. Using TRPV1 antagonists, we confirmed that TNFα up-regulation was mediated by TRPV1. Phospholipase C (PLC) was previously shown to be involved in capsaicin-induced OPG expression. However, we found that protein kinase C, not PLC, was required for heat-induced TNFα expression. Additionally, the use of cytochalasin D, an inhibitor of actin polymerisation, revealed that cytoskeleton rearrangement might be an important mechanism for cellular sensing of thermal stimuli.
  
  
  CONCLUSIONS
  Our results indicate that TRPV1 plays a multi-functional role in HPDL cells depending on the stimuli. In response to heat, TRPV1 activation leads to the induction of TNFα expression.
authors: Department of Pharmacology, Faculty of Dentistry, Chulalongkorn University, Bangkok 10330, Thailand. pl_sireerat@yahoo.com
authors: Sireerat
authors: S
authors: Sooampon
authors: Waranyoo
authors: W
authors: Phoolcharoen
authors: Prasit
authors: P
authors: Pavasant
mesh_terms: D000704:Analysis of Variance; D002470:Cell Survival; D002478:Cells, Cultured; D015638:Cytochalasin D / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006358:Hot Temperature; D006801:Humans; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism*; D010513:Periodontal Ligament / Q000166:cytology*; D011493:Protein Kinase C / Q000378:metabolism; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics; D015854:Up-Regulation
chemical_list: D053583:Interleukin-1beta; D053245:RANK Ligand; D012333:RNA, Messenger; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D014409:Tumor Necrosis Factor-alpha; D015638:Cytochalasin D; D011493:Protein Kinase C