Effects of JNK on the Production of MMP-3 by Interleukin-1beta-stimulated Human Dental Pulp Fibroblast Like Cells

Purpose: Inflammatory cytokines such as Interleukin (IL)-1β are secreted in pulpitis tissue during the caries process. Matrix metalloproteinase-3 (MMP-3) degrades extracellular matrix such as collagen types II , III, IV, IX, X, fibronectin, and laminin. In addition, MMP-3 can also activate other matrix metalloproteinases (MMPs) such as MMP-1, MMP-7, and MMP-9 in connective tissue. MMP-3, which is thought to be involved in wound repair, inflammation, and tumor initiation, is expressed as a result of inflammation in dental pulp. Dental pulp destruction is believed to be regulated, in part, by MMP-3 regulated degradation and regeneration of dental pulp tissue. We therefore focused on the mechanism of MMP-3 production in pulpitis tissue. C-Jun N-terminal kinase (JNK) plays a regulating role in apoptosis, neurodegeneration, cell differentiation and proliferation, inflammatory conditions, and cytokine production. In this study, we tested this hypothesis utilizing human dental pulp fibroblast like cells (HPFs) as a model system to evaluate the production mechanism of MMP-3 through stimulation with IL-1β. Methods: HPFs were incubated in serum-free α-MEM containing IL-1β (0, 10, 20, 50 or 100 ng/ml) for 24 h with or without the JNK inhibitor AS601245. Production of MMP-3 and activation of JNK by IL-1β were evaluated through the phosphorylation of JNK and MMP-3 antibodies using Western blot analysis. Results: In the present study, we demonstrated that MMP-3 was produced from HPFs in response to IL-1β in a JNK-dependent manner. IL-1β induced the production of MMP-3 without affecting the total production of MMP-2. Blocking JNK activation with AS601245 significantly inhibited IL-1β-induced production of MMP-3 without affecting the total production of MMP-2. Conclusion: These results suggest that JNK activated by IL-1β facilitates pulpitis by inducing the production of MMP-3 in HPFs.