NOD2 Contributes to Porphyromonas gingivalis–induced Bone Resorption

Abstract

The NOD-like receptors are cytoplasmic proteins that sense microbial by-products released by invasive bacteria. Although NOD1 and NOD2 are functionally expressed in cells from oral tissues and play a role triggering immune responses, the role of NOD2 receptor in the bone resorption and in the modulation of osteoclastogenesis is still unclear. We show that in an experimental model of periodontitis with Porphyromonas gingivalis W83, NOD2-/- mice showed lower bone resorption when compared to wild type. Quantitative polymerase chain reaction analysis revealed that wild-type infected mice showed an elevated RANKL/OPG ratio when compared to NOD2-/- infected mice. Moreover, the expression of 2 osteoclast activity markers—cathepsin K and matrix metalloproteinase 9—was significantly lower in gingival tissue from NOD2-/- infected mice compared to WT infected ones. The in vitro study reported an increase in the expression of the NOD2 receptor 24 hr after stimulation of hematopoietic bone marrow cells with M-CSF and RANKL. We also evaluated the effect of direct activation of NOD2 receptor on osteoclastogenesis, by the activation of this receptor in preosteoclasts culture, with different concentrations of muramyl dipeptide. The results show no difference in the number of TRAP-positive cells. Although it did not alter the osteoclasts differentiation, the activation of NOD2 receptor led to a significant increase of cathepsin K expression. We confirm that this enzyme was active, since the osteoclasts resorption capacity was enhanced by muramyl dipeptide stimulation, evaluated in osteoassay plate. These results show that the lack of NOD2 receptor impairs the bone resorption, suggesting that NOD2 receptor could contribute to the progression of bone resorption in experimental model of periodontitis. The stimulation of NOD2 by its agonist, muramyl dipeptide, did not affect osteoclastogenesis, but it does favor the bone resorption capacity identified by increased osteoclast activity.

E‐selectin expression induced by Porphyromonas gingivalis in human endothelial cells via nucleotide‐binding oligomerization domain‐like receptors and Toll‐like receptors

“…It has been reported that NOD1 and NOD2 mediate sensing of periodontal pathogens, including P. gingivalis , in human embryonic kidney cells (Okugawa et al ., ) and human periodontal ligament fibroblasts (Liu et al ., ). NOD2 has also been reported to play a role in alveolar bone resorption induced by P. gingivalis (Prates et al ., ). In endothelial cells, NOD1 has been linked to monitor various pathogenic bacteria, like Chlamydophila pneumoniae (Opitz et al ., ), and Listeria monocytogenes (Opitz et al ., ).…”

“…It has been reported that NOD1 and NOD2 mediate sensing of periodontal pathogens, including P. gingivalis, in human embryonic kidney cells (Okugawa et al, 2010) and human periodontal ligament fibroblasts (Liu et al, 2014). NOD2 has also been reported to play a role in alveolar bone resorption induced by P. gingivalis (Prates et al, 2014). In endothelial cells, NOD1 has been linked to monitor A B C D Figure 5 Nuclear factor-jB (NF-jB) and P38 mitogen-activated protein kinase (MAPK) signaling pathways play a role in human umbilical vein endothelial cell activation following Porphyromonas gingivalis invasion.…”

Inflammatory osteolysis: a conspiracy against bone

“…Alveolar bone loss elicited by Porphyromonas gingivalis shares many features of lysis attending OM. Cytokine release (166) as well as induction of RANKL downstream of TLR2 and NOD2 are the prominent pathways leading to osteoclast activation in periodontitis (167,168). IL-17 is also markedly increased in periodontitis and appears to be an important factor in both inflammation and osteolysis of the periodontal tissue (169).…”

TLR4, NOD1 and NOD2 mediate immune recognition of putative newly identified periodontal pathogens

“…Previous studies have reported that P. gingivalis (Burns et al ., ; Jain et al ., ) and T. forsythia (Myneni et al ., ) are recognized by TLR2, Campylobacter rectus is recognized mainly by TLR4 (Arce et al ., ), and many PRRs (including TLR2, TLR4, and NOD1) were suggested to mediate cytokine expression upon Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans stimulation (Park et al ., ). Recent studies indicate that NOD2 and TLR9 are also involved in P. gingivalis infection (Prates et al ., ; Kim et al ., ). Overall, these studies suggest that PRRs play important roles in the host response against periodontal pathogens and emphasize the importance of further characterizing the immune response to other newly identified pathogens involved in periodontitis.…”