Effects of NOD1 in Human Dental Pulp Fibroblast Like Cells

• Published in: The JAPANESE JOURNAL OF CONSERVATIVE DENTISTRY Vol. 60; no. 6; pp. 313 - 319
• Main Authors: IWASA Kazuhiro, KOMASA Reiko, YOSHIKAWA Kazushi, GODA Seiji, YAMAMOTO Kazuyo
• Format: Journal Article
• Language: English; Japanese
• Published: The Japanese Society of Conservative Dentistry 31.12.2017
• ISSN: 0387-2343
• DOI: 10.11471/shikahozon.60.313

[Abstract] Purpose: Caries-related immune response is first recognized by dental pulp fibroblast cells and is tightly regulated to avert pulpitis. Nucleotide-binding oligomerization domain protein (NOD) 1 signaling, which is essential for initiating the innate immune response to bacterial infection, is subject to many regulatory mechanisms. However, little is known about post transcriptional regulation of NOD1 dependent responses in dental pulp fibroblast cells. NOD1 recognizes D-glutamyl-meso-diaminopimelic acid (iE-DAP). RIP2 is associated with NOD1 and play critical roles in the immune system. Matrix metalloproteinases (MMPs) such as MMP-1, 2, 3, and 14 were also shown to be expressed in inflamed dental pulp tissue. MMP-3 can degrade the extracellular matrix (ECM) and activate other MMPs. MMP-3 is considered to be involved in wound healing, inflammation, and tumor initiation. Dental pulp destruction may be regulated, in part, by matrix metalloproteinase-3 (MMP-3), and other MMPs activated by MMP-3 have been shown to regulate the degradation and regeneration of dental pulp tissue. In the present study, we investigated that MMP-3 production in response to iE-DAP and its cell signaling in human pulp fibroblasts (HPFs). Methods: HPFs were incubated in serum-free α-MEM containing iE-DAP at the concentration of 0, 5, 10, 20, 50μg/ml for 24h,, and the MMP-3 production was analyzed by Western blot analysis. Next, HPFs stimulated by iE-DAP (10μg/ml) for 24h were further incubated with or without the RIP inhibitor, 0.5, 1, 5, 10, 15, 20μmol/l Gefitinib to evaluate the expression of MMP-3 and RIP2 by Western blot analysis. HPFs were incubated in serum-free α-MEM containing iE-DAP (10μg/ml) for 24 h with or without the JNK inhibitor, AS601245 or SP600125. The production of MMP-3 and activation of JNK by iE-DAP were evaluated by Western blot analysis of JNK phosphorylation and MMP-3. Results: iE-DAP enhanced the production of MMP-3 in a dose dependent manner in HPFs. RIP2 inhibitor suppressed the production of MMP-3 on iE-DAP stimulated HPFs. We demonstrated that MMP-3 was produced from HPFs in response to iE-DAP in a JNK-dependent manner. Conclusion: These results suggest that iE-DAP/NOD1 induced the production of MMP-3 in HPFs through a signaling cascade involving RIP2-mediated phosphorylation of JNK.