The Novel NF-κB Inhibitor, MTI-II Peptide Anti-Inflammatory Drug, Suppresses Inflammatory Responses in Odontoblast-Like Cells

Regulation of inflammation is important for pulp wound healing, including protective responses by odontoblast-like cells. However, methods for directly regulating pulp inflammation have not yet been described. The inflammatory response is mediated by a transcription factor, nuclear factor-κB (NF-κB), which activates inflammatory cytokines including tumor necrosis factor (TNF)-α. Macromolecular translocation inhibitor II (MTI-II) was previously demonstrated as an enhancer of the transcriptional activity of glucocorticoid-bound glucocorticoid receptor. Recently, a MTI-II peptide anti-inflammatory drug (MPAID) was bioengineered from the structure of MTI-II as an inhibitor of NF-κB transactivation. Here, we examined the effects of MTI-II and MPAID on the inflammatory responses of odontoblast-like cells. TNF-α inhibited alkaline phosphatase (ALP) activity, a marker of odontoblast/osteogenic differentiation, and induced NF-κB transcriptional activity in KN-3 cells, which are odontoblast-like cells derived from dental papilla cells of rat incisors, without affecting their viability. Exogenous expression of MTI-II suppressed the NF-κB transcriptional activity induced by TNF-α or overexpression of p65 (a main subunit of NF-κB) in the cells, whereas it failed to inhibit degradation of IκBα and nuclear translocation of p65 after TNF-α treatment, suggesting that MTI-II inhibits NF-κB transcriptional activity by modulating the duration of DNA binding by p65. MPAID also inhibited TNF-α-induced NF-κB transcriptional activity, the mRNA expression of IL-6 and IL-8, and IL-6 production. Furthermore, pretreatment of the cells with MPAID restored the inhibitory effect of TNF-α on ALP activity. These results suggest that MPAID may be able to regulate the inflammatory response and maintain a protective response of dental pulp. J. Cell. Biochem. 117: 2552–2558, 2016.