Expression of NOD2 is increased in inflamed human dental pulps and lipoteichoic acid-stimulated odontoblast-like cells

Abstract

Human odontoblasts trigger immune response s to oral bacteria that invade dental tissues during the caries process. To date, their ability to regulate the expression of the nucleotide-binding domain leucine-rich repeat containing receptor NOD2 when challenged by Gram-positive bacteria is unknown. In this study, we investigated NOD2 expression in healthy and inflamed human dental pulps challenged by bacteria, and in cultured odontoblast-like cells stimulated with lipoteichoic acid (LTA), a Toll-like receptor (TLR) 2 agonist which is specific for Gram-positive bacteria. We found that NOD2 gene expression was significantly up-regulated in pulps with acute inflammation compared to healthy ones. In vitro, LTA augmented NOD2 gene expression and protein level in odontoblast-like cells. The increase was more pronounced in odontoblast-like cells compared to dental pulp fibroblasts. Blocking experiments in odontoblast-like cells with anti-TLR2 antibody strongly reduced the NOD2 gene expression increase, whereas stimulation with the synthetic TLR2 ligand Pam₂CSK₄ confirmed NOD2 gene up-regulation following TLR2 engagement. These data suggest that NOD2 up-regulation is part of the odontoblast immune response to Gram-positive bacteria and might be important in protecting human dental pulp from the deleterious effects of cariogenic pathogens.

Keywords

dental pulp innate immunity lipoteichoic acid odontoblast pattern recognition molecule

References

Kapetanovic R. , Cavaillon JM Early events in innate immunity in the recognition of microbial pathogens. Expert Opin Biol Ther 2007; 7: 1-12.

Carneiro LAM , Magalhaes JG , Tattoli I. , Philpott DJ , Travassos LH Nod-like proteins in inflammation and disease . J Pathol 2008; 214: 136-148.

Uematsu S. , Akira S. Toll-like receptors (TLRs) and their ligands. Handbook Exp Pharmacol 2008; 183: 1-20.

Wilmanski JM , Petnicki-Ocwwieja T. , Kobayashi KS NLR proteins: integral members of innate immunity and mediators of inflammatory diseases . J Leukoc Biol 2008; 83: 13-30.

Chen G. , Shaw MH , Kim Y-G. , Nunez G. NOD-like receptors: role in innate immunity and inflammatory disease . Annu Rev Pathol Mech Dis 2009; 4: 365-398.

Kufer TA , Sansonetti PJ Sensing of bacteria: NOD a lonely job. Curr Opin Microbiol 2007; 10: 62-69.

Girardin SE , Hugot JP , Sansonetti PJ Lessons from Nod2 studies: towards a link between Crohn’s disease and bacterial sensing. Trends Immunol 2003 ; 24: 652-658.

Fournier B. , Philpott DJ Recognition of Staphylococcus aureus by the innate immune system. Clin Microbiol Rev 2005; 18: 521-540.

Kobayashi KS , Chamaillard M. , Ogura Y. et al. Nod2-dependent regulation of innate and adaptive immunity in the intestinal tract. Science 2005; 307: 731-734.

10.

Tattoli I. , Travassos LH , Carneiro LA , Magalhaes JG , Girardin S. The nodosome: Nod1 and Nod2 control bacterial infections and inflammation . Semin Immunopathol 2007; 29: 289-301.

11.

Franchi L. , Warner N. , Viani K. et al. Function of Nod-like receptors in microbial recognition and host defense. Immunol Rev 2009; 227: 106-128.

12.

Yang S. , Tamai R. , Akashi S. et al. Synergistic effect of muramyldipeptide with lipopolysaccharide or lipoteichoic acid to induce inflammatory cytokines in human monocytic cells in culture. Infect Immun 2001; 69: 2045-2053.

13.

Netea MG , Ferwerda G. , de Jong DJ et al. Nucleotide-binding oligomerization domain-2 modulates specific TLR pathways for the induction of cytokine release. J Immunol 2005; 174: 6518-6523.

14.

Uehara A. , Yang S. , Fujimoto Y. et al. Muramyldipeptide and diaminopimelic acid-containing desmuramylpeptides in combination with chemically synthesized Toll-like receptor agonists synergistically induced production of interleukin-8 in a NOD2-and NOD1-dependent manner, respectively , in human monocytic cells in culture. Cell Microbiol 2005; 7: 53-61.

15.

Moreira LO , El Kasmi KC , Smith AM et al. The TLR2-MyD88- NOD2-RIPK2 signalling axis regulates a balanced pro-inflammatory and IL-10-mediated anti-inflammatory cytokine response to Gram-positive cell walls. Cell Microbiol 2008 ; 10: 2067-2077.

16.

Kobayashi M. , Yoshiki R. , Sakabe J. , Kabashima K. , Nakamura M. , Tokura Y. Expression of Toll-like receptor 2, NOD2 and dectin-1 and simulatory effects of their ligands and histamine in normal human keratinocytes. Br J Dermatol 2009; 160: 297-304.

17.

Durand SH , Flacher V. , Romeas A. et al. Lipoteichoic acid increases TLR and functional chemokine expression while reducing dentin formation in in vitro differentiated human odontoblasts . J Immunol 2006; 176: 2880-2887.

18.

Staquet MJ , Durand SH , Colomb E. et al. Different roles of odontoblasts and fibroblasts in immunity. J Dent Res 2008; 87: 256-261.

19.

Farges JC , Keller JF , Carrouel F. et al. Odontoblasts in the dental pulp immune response. J Exp Zool (Mol Dev Evol) 2009; 312B: 425-436.

20.

Love RM , Jenkinson HF Invasion of dentinal tubules by oral bacteria. Crit Rev Oral Biol Med 2002; 13: 171-183.

21.

Keller JF , Carrouel F. , Colomb E. et al. Toll-like receptor 2 activation by lipoteichoic acid induces differential production of pro-inflammatory cytokines in human odontoblasts, dental pulp fibroblasts and immature dendritic cells. Immunobiology 2009, Feb 26; doi:10.1016/j.imbio.2009.01.009 [Epub ahead of print].

22.

Couble ML , Farges JC , Bleicher F. , Perrat-Mabillon B. , Boudeulle M. , Magloire H. Odontoblast differentiation of human dental pulp cells in explant cultures . Calcif Tissue Int 2000; 66: 129-138.

23.

Legrand-Poels S. , Kustermans G. , Bex F. , Kremmer E. , Kufer TA , Piette J. Modulation of Nod2-dependent NF-kappaB signaling by the actin cytoskeleton. J Cell Sci 2007 ; 120: 1299-1310.

24.

Underhill DM Collaboration between the innate immune receptors dectin-1, TLRs and Nods. Immunol Rev 2007; 219: 75-87.

25.

Horst OV , Tompkins KA , Coats SR , Braham PH , Darveau RP , Dale BA TGF-β1 inhibits TLR-mediated odontoblast responses to oral bacteria . J Dent Res 2009; 88: 333-338.

26.

Lin ZM , Song Z. , Qin W. et al. Expression of nucleotide-binding oligomerization domain 2 in normal human dental pulp cells and dental pulp tissues. J Endod 2009; 35: 838-842.