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Open Access Highly Accessed Research article

Caries induced cytokine network in the odontoblast layer of human teeth

Orapin V Horst123*, Jeremy A Horst124, Ram Samudrala24 and Beverly A Dale2

Author Affiliations

1 Department of Orofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Street, San Francisco, CA, 94143, Box 0422, USA

2 Department of Oral Biology, School of Dentistry, University of Washington, 1959 NE Pacific Street, Seattle, WA, 98195, Box 357132, USA

3 Department of Endodontics, School of Dentistry, University of Washington, 1959 NE Pacific Street, Seattle, WA, 98195, Box 357448, USA

4 Department of Microbiology, School of Medicine, University of Washington, 1959 NE Pacific Street, Seattle, WA, 98195, Box 357242, USA

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BMC Immunology 2011, 12:9  doi:10.1186/1471-2172-12-9

Published: 24 January 2011

Abstract

Background

Immunologic responses of the tooth to caries begin with odontoblasts recognizing carious bacteria. Inflammatory propagation eventually leads to tooth pulp necrosis and danger to health. The present study aims to determine cytokine gene expression profiles generated within human teeth in response to dental caries in vivo and to build a mechanistic model of these responses and the downstream signaling network.

Results

We demonstrate profound differential up-regulation of inflammatory genes in the odontoblast layer (ODL) in human teeth with caries in vivo, while the pulp remains largely unchanged. Interleukins, chemokines, and all tested receptors thereof were differentially up-regulated in ODL of carious teeth, well over one hundred-fold for 35 of 84 genes. By interrogating reconstructed protein interaction networks corresponding to the differentially up-regulated genes, we develop the hypothesis that pro-inflammatory cytokines highly expressed in ODL of carious teeth, IL-1β, IL-1α, and TNF-α, carry the converged inflammatory signal. We show that IL1β amplifies antimicrobial peptide production in odontoblasts in vitro 100-fold more than lipopolysaccharide, in a manner matching subsequent in vivo measurements.

Conclusions

Our data suggest that ODL amplifies bacterial signals dramatically by self-feedback cytokine-chemokine signal-receptor cycling, and signal convergence through IL1R1 and possibly others, to increase defensive capacity including antimicrobial peptide production to protect the tooth and contain the battle against carious bacteria within the dentin.