HBD3 Suppresses Dendritic Cell MAPK Pathways to P. gingivalis rHagB

Unrestrained inflammatory responses can lead to inappropriate activation of the innate and acquired immune systems resulting in a variety of chronic diseases such as periodontitis. The MAPK pathways are important in controlling the type and magnitude of the inflammatory response to Porphyromonas gingivalis. Previously we found that human Β-defensin HBD3 can attenuate pro-inflammatory cytokine responses to recombinant hemagglutinin B (rHagB) from P. gingivalis. In this study we hypothesize that this occurs by inhibiting extracellular signal related kinase (ERK 1/2), c-Jun N-terminal kinase (JNK 1/2), or p38 pathways. Objectives: Determine if HBD3 attenuates P. gingivalis rHagB-induced MAPK responses in human myeloid dendritic cells. Methods: Human myeloid dendritic cells were exposed to rHagB or HBD3 + rHagB mixtures. After 30 minutes, cells were lysed and changes in MAPK pathways were measured using a commercial multiplexed fluorescent bead-based immunoassay (Millipore, Billerica, MA) in the Luminex 100 IS Instrument (Luminex, Austin, TX). Results: rHagB activated ERK, p38, and JNK signaling pathways in human myeloid dendritic cell lysates within 10-30 minutes. HBD3 did not activate any of these pathways above the response seen with PBS alone. After 30 minutes, HBD3 + rHagB mixtures induced significantly lower (P < 0.05) levels of ERK 1/2 and to a lesser extent JNK 1/2, but not p38 in human myeloid dendritic cells. Conclusions: p38 activates DNA transcriptional factor CREB; p38 and JNK activate the transcriptional complex containing activator protein-1 (AP-1); and ERK, JNK, and p38 activate the transcriptional factor ELK1. IL-6, IL-10, GM-CSF, and TNF-alpha are downstream products of these factors and partial inhibition of ERK 1/2 and JNK 1/2 could explain the selective HBD3-mediated decrease in the production of these pro-inflammatory cytokines by human myeloid dendritic cells exposed to rHagB. Supported by NIH/NIDCR T32 DE014678 and R01 DE014390.