Role of NOD2 and RIP2 in host-microbe interactions with Gram-negative bacteria: insights from the periodontal disease model

• Published in: Innate immunity (London, England) Vol. 22; no. 8; p. 598
• Main Authors: Souza, Joao Ac, Medeiros, Marcell C, Rocha, Fernanda Rg, de Aquino, Sabrina G, Ávila-Campos, Mario J, Spolidorio, Luis C, Zamboni, Dario S, Graves, Dana T, Rossa, Junior, Carlos
• Format: Journal Article
• Language: English
• Published: United States 01-11-2016
• Subjects: Animals; Bone Resorption - immunology; Cell Differentiation; Cells, Cultured; Gene Expression Regulation; Gram-Negative Bacterial Infections - immunology; Inflammation Mediators - metabolism; Macrophages - microbiology; Macrophages - physiology; Mice; Mice, Inbred C57BL; Mice, Knockout; Nod2 Signaling Adaptor Protein - genetics; Nod2 Signaling Adaptor Protein - metabolism; Osteogenesis - immunology; Periodontitis - immunology; RANK Ligand - metabolism; Receptor-Interacting Protein Serine-Threonine Kinases - genetics; Receptor-Interacting Protein Serine-Threonine Kinases - metabolism; Bone resorption; macrophages; innate immunity; inflammation; NOD2 signaling adaptor protein
• ISSN: 1753-4267
• DOI: 10.1177/1753425916666652

NOD2 is a member of the NLR family of proteins that participate in the activation of the innate immune response. RIP2 is a downstream kinase activated by both NOD1 and NOD2. There is scarcity of information regarding the relevance of NOD2 in periodontitis, a chronic inflammatory condition characterized by inflammatory bone resorption. We used NOD2-KO and RIP2-KO mice in a model of microbial-induced periodontitis. Heat-killed Aggregatibacter actinomycetemcomitans was injected in the gingival tissues three times/wk for 4 wk. Bone resorption was assessed by μCT analysis; osteoclasts were identified by immunohistochemical staining for TRAP and inflammation was assessed using a severity score system in H/E-stained sections. In vitro studies using primary macrophages assessed the response macrophages using qPCR-based array and multi-ligand ELISA. Bone resorption and osteoclastogenesis were significantly reduced in NOD2-KO mice. Severity of inflammation was not affected. qPCR-focused arrays and multi-ligand ELISA showed that expression of pro-inflammatory mediators was reduced in NOD2- and RIP2-deficient cells. RANKL-induced osteoclastogenesis was impaired in NOD2- and RIP2-deficient macrophages. We conclude that NOD2 is important for osteoclast differentiation and inflammatory bone resorption in vivo and also for the macrophage response to Gram-negative bacteria.