Toll-like receptor 2 and NALP2 mediate induction of human beta-defensins by fusobacterium nucleatum in gingival epithelial cells.
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.
Ji
Suk
S
Department of Oromaxillofacial Infection and Immunity, School of Dentistry and Dental Research Institute, Seoul National University, Jongno-gu, Seoul, South Korea.
Shin
Ji Eun
JE
Kim
Young Sook
YS
Oh
Ju-Eun
JE
Min
Byung-Moo
BM
Choi
Youngnim
Y
D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology / Q000378:metabolism*; D000328:Adult; D051017:Apoptosis Regulatory Proteins; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D005434:Flow Cytometry; D005674:Fusobacterium Infections / Q000276:immunology / Q000378:metabolism*; D016967:Fusobacterium nucleatum / Q000276:immunology; D015870:Gene Expression; D005881:Gingiva / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D018613:Microscopy, Confocal; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000378:metabolism*; D023083:beta-Defensins / Q000276:immunology / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D016209:Interleukin-8; C495732:NLRP2 protein, human; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D023083:beta-Defensins