Pivotal role of NOD2 in inflammatory processes affecting atherosclerosis and periodontal bone loss.

The purpose of this study was to elucidate the role of nucleotide binding oligomerization domain-containing protein 2 (NOD2) signaling in atherosclerosis and periodontal bone loss using an Apolipoprotein E(-/-) (ApoE(-/-)) mouse model based on the proposed role of NOD2 in inflammation. NOD2(-/-)ApoE(-/-) and ApoE(-/-) mice fed a standard chow diet were given an oral gavage of Porphyromonas gingivalis for 15 wk. NOD2(-/-)ApoE(-/-) mice exhibited significant increases in inflammatory cytokines, alveolar bone loss, cholesterol, and atherosclerotic lesions in the aorta and the heart compared with ApoE(-/-) mice. In contrast, ApoE(-/-) mice injected i.p. with Muramyl DiPeptide (MDP) to stimulate NOD2 and given an oral gavage of P. gingivalis displayed a reduction of serum inflammatory cytokines, alveolar bone loss, cholesterol, and atherosclerotic lesions in the aorta and aortic sinus compared with ApoE(-/-) mice orally challenged but injected with saline. A reduction in body weight gain was observed in ApoE(-/-) mice fed a high-fat diet (HFD) and injected with MDP compared with ApoE(-/-) mice fed a high-fat diet but injected with saline. MDP treatment of bone marrow-derived macrophages incubated with P. gingivalis increased mRNA expressions of NOD2, Toll-like receptor 2, myeloid differentiation primary response gene 88, and receptor-interacting protein-2 but reduced the expressions of inhibitor of NF-κB kinase-ß, NF-κB, c-Jun N-terminal kinase 3, and TNF-α protein levels compared with saline control, highlighting pathways involved in MDP antiinflammatory effects. MDP activation of NOD2 should be considered in the treatment of inflammatory processes affecting atherosclerosis, periodontal bone loss ,and possibly, diet-induced weight gain.

Receptor activator of nuclear factor kappa B ligand antagonists inhibit tissue inflammation and bone loss in experimental periodontitis.

AIM: The purpose of this study was to assess the role of anti-bone resorptive agents and an anti-inflammatory compound in murine Porphyromonas gingivalis (P. gingivalis)-induced periodontitis. MATERIAL AND METHODS: Six randomly assigned groups were administered vehicle (saline, control) (n = 6), P. gingivalis infection only (untreated) (n = 6), human-Fc (n = 4), Kavain (n = 6), OPG-Fc (n = 6) and Receptor activator of nuclear factor-kappa B (RANK)-Fc (n = 6) intraperitoneally at day 0, 3 and 7. Animals were euthanized on day 10 and subjected to comprehensive histomorphometric analysis. To capture the progress of inflammation, serum samples were collected at days 0, 3, 7 and 10 for levels of pro-inflammatory cytokines. RESULTS: Compared with control group, OPG-Fc, RANK-Fc and Kavain treatment showed significant bone loss reduction with OPG-Fc performing better than RANK-Fc or Kavain. Epithelial down-growth showed significant reduction in treatment groups with OPG-Fc performing better than RANK-Fc or Kavain. Finally, Kavain, OPG-Fc and RANK-Fc-treated mice displayed reduced inflammatory cell counts and cytokine expression particularly at day 7 postinfection. CONCLUSIONS: RANKL antagonists and Kavain effectively reduced alveolar bone loss in P. gingivalis-induced periodontitis in our mice model. Compared with RANK-Fc, Kavain-treated animals showed milder improvement of bone and connective tissue inflammation. Therapeutic implications in the prevention of periodontal bone loss are discussed.