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Infection and Immunity, March 2009, p. 1044-1052, Vol. 77, No. 3
0019-9567/09/$08.00+0     doi:10.1128/IAI.00449-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Toll-Like Receptor 2 and NALP2 Mediate Induction of Human Beta-Defensins by Fusobacterium nucleatum in Gingival Epithelial Cells{triangledown}

Suk Ji,1,{dagger} Ji Eun Shin,1,{dagger} Young Sook Kim,1 Ju-Eun Oh,2 Byung-Moo Min,2 and Youngnim Choi1*

Department of Oromaxillofacial Infection and Immunity,1 Department of Oral Biochemistry and Craniomaxillofacial Reconstructive Science, BK21 CLS, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea2

Received 11 April 2008/ Returned for modification 23 May 2008/ Accepted 12 December 2008

We previously reported that infection by Fusobacterium nucleatum strongly induced the expression of both human beta-defensin 2 (HBD-2) and HBD-3 by gingival epithelial cells. The aim of this study was to characterize the pattern recognition receptors (PRRs) and regulatory mechanisms involved in the induction of HBD-2 and -3 expression by F. nucleatum in gingival epithelial cells. Immortalized human gingival epithelial HOK-16B cells were infected with live or heat-killed F. nucleatum, and the expression of HBDs and interleukin-8 (IL-8) was examined by real-time reverse transcription-PCR and enzyme-linked immunosorbent assay, respectively. Live, but not heat-killed, F. nucleatum invaded HOK-16B cells, as seen by confocal microscopy and flow cytometry. Live F. nucleatum induced both HBD-2 and -3 efficiently, whereas heat-killed bacteria induced only HBD-3 at a reduced level. Knockdown of NACHT-LRR- and pyrin domain-containing protein 2 (NALP2), the most abundant intracellular PRR in HOK-16B cells, by RNA interference (RNAi) significantly reduced the induction of HBD-3 but not HBD-2 and IL-8. In addition, knockdown of Toll-like receptor 2 (TLR2) by RNAi reduced the upregulation of HBD-2 and -3 but not IL-8. Heat-killed F. nucleatum was hindered in its ability to activate TLR2 and JNK signaling pathways. Theses data show that TLR2 and NALP2 mediate the induction of HBDs by F. nucleatum in gingival epithelial cells, but thresholds for the two HBD genes are different.

* Corresponding author. Mailing address: Department of Oromaxillofacial Infection and Immunity, School of Dentistry and Dental Research Institute, Seoul National University, 28-2 Yeongeon-dong, Jongno-gu, Seoul 110-749, South Korea. Phone: 82-2-740-8643. Fax: 82-2-743-0311. E-mail: youngnim{at}snu.ac.kr

{triangledown} Published ahead of print on 22 December 2008.

Editor: B. A. McCormick

{dagger} S.J. and J.E.S. contributed equally to this study.

Infection and Immunity, March 2009, p. 1044-1052, Vol. 77, No. 3
0019-9567/09/$08.00+0     doi:10.1128/IAI.00449-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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