ABSTRACT
INTRODUCTION: 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.
Subject(s)
Interleukin-8/biosynthesis , Nod1 Signaling Adaptor Protein/biosynthesis , Pulpitis/immunology , Pulpitis/metabolism , Analysis of Variance , Cells, Cultured , Chemokine CCL2/biosynthesis , Chemokine CCL2/genetics , Dental Pulp/cytology , Dental Pulp/immunology , Dental Pulp/metabolism , Fibroblasts/immunology , Fibroblasts/metabolism , Gene Expression Regulation , Humans , Interleukin-8/genetics , JNK Mitogen-Activated Protein Kinases/metabolism , MAP Kinase Signaling System , Nod1 Signaling Adaptor Protein/agonists , Nod1 Signaling Adaptor Protein/genetics , Phosphorylation , Statistics, Nonparametric , Up-Regulation , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
Because eugenol is a major component of root canal sealers and retrograde filling materials, its effects on periapical bone healing are therefore of concern. In this study, the effects of eugenol on the activation of nuclear factor kappa B (NF-kappaB) and the expression of cyclooxygenase-2 (COX-2) in human osteoblasts were investigated. The results showed that eugenol activated the nuclear translocation of NF-kappaB. In addition, COX-2 protein expression in osteoblasts was induced by eugenol in a dose-dependent manner. Furthermore, the eugenol-modulated COX-2 expression was inhibited by an NF-kappaB inhibitor, N-acetylcysteine. Taken together, eugenol might induce COX-2 expression through the activation of NF-kappaB in human osteoblasts. These results suggest that eugenol might be involved in periapical healing by impairing the functions of osteoblasts.
Subject(s)
Cyclooxygenase 2/drug effects , Eugenol/pharmacology , NF-kappa B/drug effects , Osteoblasts/drug effects , Root Canal Filling Materials/pharmacology , Acetylcysteine/pharmacology , Blotting, Western , Cell Line , Cell Nucleus/drug effects , Cell Shape/drug effects , Cell Survival/drug effects , Cyclooxygenase 2 Inhibitors/pharmacology , Cytoplasm/drug effects , Dose-Response Relationship, Drug , Eugenol/administration & dosage , Fluorescent Antibody Technique, Direct , Free Radical Scavengers/pharmacology , Humans , Microscopy, Confocal , NF-kappa B/antagonists & inhibitors , Osteoblasts/enzymologyABSTRACT
Eugenol is commonly used as an analgesic agent during acute pulpitis and is a major component of root canal sealers. Despite the frequent applications of eugenol in the practice of dentistry, little is known about the role of eugenol under the status of inflammation. This study was aimed to investigate the influence of eugenol on human macrophages (U937) under the stimulation of lipopolysaccharide (LPS). Eugenol was shown to block the release of the bone resorbing mediators, including interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and prostaglandin E2 from LPS-stimulated macrophages. In contrast, eugenol alone did not alter the expression levels of these proinflammatory mediators in macrophages. Consistent with downregulation of bone-resorbing mediators, eugenol suppressed the messenger RNA expression of LPS-induced IL-1beta, TNF-alpha, and cyclooxygenase-2 in macrophages. The results suggest a potential anti-inflammatory effect of eugenol in the acute inflamed pulps and apical periodontitis.
