NEMOTO Eiji School of Dentistry, Tohoku University, Research Associate, 歯学部, 助手 (40292221)
SUGAWARA Shunji School of Dentistry, Tohoku University, Research Associate, 歯学部, 助手 (10241639)
|Budget Amount *help
¥12,800,000 (Direct Cost : ¥12,800,000)
Fiscal Year 1999 : ¥6,200,000 (Direct Cost : ¥6,200,000)
Fiscal Year 1998 : ¥6,600,000 (Direct Cost : ¥6,600,000)
Bacterial cell surface amphiphiles exhibit various biological activities. Endotoxic lipopolysaccharides (LPS) distributed in the outer membrane of gram-negative bacteria and lipoteichoic acid (LTA) distributed in the cell surfaces of gram-positive bacteria are representative bioactive amphiphiles. Bacterial amphiphiles activate host cells such as macrophages through membrane CD14 (mCD14) expressed on cell surfaces. Last year, we demonstrated the presence of two types of human gingival fibroblasts that highly and lowly express mCD14, and the former cells produced interleukin-8 (IL-8) upon stimulation with LPS and lipid A from Enterobacteriaceae. This year, we found that 1. Bacillus subtilis LTA also activated human gingival fibroblasts via mCD14, whereas LTA from oral streptococci such as Streptococcus sanguis and Streptococcus mutans acted as an LPS-antagonist to inhibit IL-8-induction by LPS. 2. The LPS fraction from Prevotella intermedia, periodontal disease-associated bacteria, activated human dental pulp cells that lack mCD14, in a soluble CD14- and nuclear factor AP-1-dependent manner. 3. Furthermore, in collaboration with Prof. Shizuo Akira, Osaka University, we studied the relationship between amphiphiles and the Toll-like receptor (TLR) system, which was recently revealed to be associated with CD14 and is involved in LPS signaling. We revealed that LTA as well as LPS was recognized by TLR4 in contrast to previous reports. We also obtained evidence suggesting that a bioactive glycoprotein, PGP, prepared from P. intermedia, was recognized by TLR2.
With the viewpoint that "bacterial products overstimulate the innate immune system, and result in tissue destruction," we would like to reveal how the CD14/TLR system recognizes and responds to microbes in periodontal tissues in relation to the pathogenesis of periodontal diseases.