Lipoteichoic acid partially contributes to the inflammatory responses to Enterococcus faecalis.
Enterococcus faecalis, a pathogenic gram-positive bacterium, is closely related to refractory apical periodontitis. Because lipoteichoic acid (LTA) is considered a major virulence factor of gram-positive bacteria, in the present study, highly pure LTA from E. faecalis was prepared, and its ability to stimulate murine macrophages was investigated in comparison with those of the killed whole cells. Upon exposure to E. faecalis LTA, RAW 264.7 (a murine macrophage cell line) produced a significantly (p < 0.05) high level of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) in a concentration-dependent manner. It is to note that the LTA was able to stimulate Toll-like receptor 2 (TLR2) but not TLR4. Concomitantly, LTA enhanced the DNA-binding activity of a transcription factor, nuclear factor-kappa B (NF-kappaB), which plays an important role in the transcriptional activation of genes encoding inflammatory mediators. In contrast, heat-killed E. faecalis stimulated both TLR2 and TLR4, whereas the killed E. faecalis whole cells induced significant (p < 0.05) levels of TNF-alpha and NO in RAW 264.7 cells as their LTA did. These results suggest that LTA partially contributes to E. faecalis-induced inflammatory responses.
Baik
Jung Eun
JE
Department of Oral Microbiology & Immunology, Dental Research Institute and BK21 Program, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
Ryu
Young Hee
YH
Han
Ji Young
JY
Im
Jintaek
J
Kum
Kee-Yeon
KY
Yun
Cheol-Heui
CH
Lee
Kangseok
K
Han
Seung Hyun
SH
D000818:Animals; D002460:Cell Line; D013293:Enterococcus faecalis / Q000276:immunology / Q000472:pathogenicity*; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000276:immunology* / Q000494:pharmacology; D008262:Macrophage Activation / Q000276:immunology*; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D010485:Periapical Periodontitis / Q000276:immunology / Q000382:microbiology*; D013682:Teichoic Acids / Q000276:immunology* / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000096:biosynthesis; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D037521:Virulence Factors
D008070:Lipopolysaccharides; D016328:NF-kappa B; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D037521:Virulence Factors; D009569:Nitric Oxide; C009900:lipoteichoic acid