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Mol Immunol. 2017 Nov;91:218-224. doi: 10.1016/j.molimm.2017.09.009. Epub 2017 Sep 30.

Streptococcus gordonii lipoproteins induce IL-8 in human periodontal ligament cells.

Author information

1
Department of Oral Microbiology and Immunology, DRI, and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul 08826, Republic of Korea.
2
Department of Oral Microbiology and Immunology, DRI, and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul 08826, Republic of Korea; Research Division for Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 56212, Republic of Korea.
3
Research Division for Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 56212, Republic of Korea.
4
Department of Conservative Dentistry and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea.
5
Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea.
6
Department of Oral Microbiology and Immunology, DRI, and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul 08826, Republic of Korea. Electronic address: shhan-mi@snu.ac.kr.

Abstract

Streptococcus gordonii, a Gram-positive oral bacterium, is a life-threatening pathogen that causes infective endocarditis. It is frequently isolated from the periapical lesions of patients with apical periodontitis and has thus been implicated in inflammatory responses. However, little is known about the virulence factors of S. gordonii responsible for the induction of inflammatory responses in the periapical areas. Here, we investigated the role of S. gordonii cell wall-associated virulence factors on interleukin (IL)-8 induction in human periodontal ligament (PDL) cells using ethanol-inactivated wild-type S. gordonii, a lipoteichoic acid (LTA)-deficient mutant (ΔltaS), and a lipoprotein-deficient mutant (Δlgt). Wild-type S. gordonii induced IL-8 expression at both the protein and mRNA levels in human PDL cells in a dose- and time-dependent manner. A transient transfection and reporter gene assay demonstrated that wild-type S. gordonii activated Toll-like receptor 2 (TLR2). Additionally, IL-8 production induced by wild-type S. gordonii was substantially inhibited by anti-TLR2-neutralizing antibodies. Both wild-type S. gordonii and the ΔltaS mutant induced IL-8 production; however, this response was not observed when cells were stimulated with the Δlgt mutant. Interestingly, lipoproteins purified from S. gordonii induced IL-8 production, whereas purified LTA did not. In addition, purified lipoproteins stimulated TLR2 more potently than LTA. Furthermore, S. gordonii-induced IL-8 expression was specifically inhibited by blocking p38 kinase, while lipoprotein-induced IL-8 expression was inhibited by blocking p38 kinase, ERK, or JNK. Of particular note, exogenous addition of purified S. gordonii lipoproteins enhanced Δlgt-induced IL-8 production in human PDL cells to an extent similar to that induced by the wild-type strain. Collectively, these results suggest that lipoproteins are an important component of S. gordonii for the induction of IL-8 production in human PDL cells through TLR2 activation. Therefore, lipoproteins potentially contribute to inflammatory apical periodontitis.

KEYWORDS:

Apical periodontitis; Human periodontal ligament cells; IL-8; Lipoprotein; Streptococcus gordonii; TLR2

PMID:
28963931
DOI:
10.1016/j.molimm.2017.09.009
[Indexed for MEDLINE]

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