title: Up-regulation of nucleotide-binding oligomerization domain 1 in inflamed human dental pulp.
abstract: BACKGROUND
  The innate immune response is activated by recognition of microbial components through specific pattern recognition receptors including nucleotide-binding oligomerization domain (NOD)-like receptors. However, the regulation of NOD-1 in inflamed human dental pulp remains poorly understood. This study aimed to evaluate the expression of NOD-1 in healthy and inflamed human dental pulps. In addition, the secretion of chemokines induced by NOD-1 and the related signaling pathways were studied.
  
  
  METHODS
  Samples of human dental pulp tissues were obtained from freshly extracted wisdom teeth. The protein localization of NOD-1 in the pulp tissues was detected by immunohistochemistry. In addition, human dental pulp fibroblasts were stimulated with NOD-1 agonist γ-D-glutamylmeso-diaminopimelic acid. Production of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) was determined by an enzyme-linked immunosorbent assay. The involvement of mitogen-activated protein kinase (MAPK) signaling pathways was examined by Western blot analysis, and the association of MAPK signaling with chemokine production was determined.
  
  
  RESULTS
  The results demonstrated the expression of NOD-1 in normal dental pulp, and up-regulated NOD-1 expression was observed in inflamed dental pulp. On stimulation with NOD-1 agonist, production of IL-8 and MCP-1 was induced in a dose-dependent manner. Moreover, phosphorylation of p38 MAPK and Jun N-terminal kinase (JNK) was enhanced by stimulation of NOD-1. With the treatment of p38 MAPK and JNK inhibitors, the NOD-1-induced IL-8 production was suppressed.
  
  
  CONCLUSIONS
  In response to microbial invasion, the expression of NOD-1 can be regulated in a ligand-inducible manner. NOD-1 might participate in pulp inflammation through chemokine production via MAPK signaling pathways.
authors.affiliation: Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ya-Yun
authors.initials: YY
authors.lastname: Lee
authors.forename: Chi-Hang
authors.initials: CH
authors.lastname: Chan
authors.forename: Shan-Ling
authors.initials: SL
authors.lastname: Hung
authors.forename: Yi-Chen
authors.initials: YC
authors.lastname: Chen
authors.forename: Yuan-Ho
authors.initials: YH
authors.lastname: Lee
authors.forename: Shue-Fen
authors.initials: SF
authors.lastname: Yang
mesh_terms: D000704:Analysis of Variance; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000096:biosynthesis / Q000235:genetics; D003782:Dental Pulp / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D005347:Fibroblasts / Q000276:immunology / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D053474:Nod1 Signaling Adaptor Protein / Q000819:agonists / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation; D011671:Pulpitis / Q000276:immunology* / Q000378:metabolism*; D018709:Statistics, Nonparametric; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D018932:Chemokine CCL2; D016209:Interleukin-8; C119067:NOD1 protein, human; D053474:Nod1 Signaling Adaptor Protein; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases