Beyond toll-like receptors: Porphyromonas gingivalis induces IL-6, IL-8, and VCAM-1 expression through NOD-mediated NF-κB and ERK signaling pathways in periodontal fibroblasts.

To investigate whether oligomerization domains (NODs) are involved in Porphyromonas gingivalis-induced interleukin (IL)-6, IL-8, and vascular cell adhesion molecule (VCAM)-1 expression beyond Toll-like receptors (TLRs), we investigated the role of NOD1/2 in P. gingivalis-induced IL-6, IL-8, and VCAM-1 expression in human gingival fibroblasts (hGFs) and periodontal ligament cells (hPDLCs). The mechanism was explored by activation and silence of NODs, electrophoretic mobility shift assay (EMSA), and pathway blockade assays. Results showed that P. gingivalis could induce NOD1, NOD2, IL-6, IL-8, and VCAM-1 expression in hGFs and hPDLs at mRNA and protein levels. Activation of NOD1/2 by agonists could clearly upregulate the expression of these genes, while silence of NOD1/2 could remarkably attenuate them. EMSA and blockade of NF-κB and extracellular-signal-regulated kinase (ERK)1/2 pathway assays also verified that the two pathways were involved in NOD1/2-mediated IL-6, IL-8, and VCAM-1 expression. In conclusion, our findings demonstrated that P. gingivalis induced IL-6, IL-8, and VCAM-1 expression in hGFs and hPDLCs through NOD1/2-mediated NF-κB and ERK1/2 signaling pathways beyond TLRs.