Biological properties of the native and synthetic lipid A of Porphyromonas gingivalis lipopolysaccharide.
METHODS
A pentaacyl and diphosphoryl lipid A molecule found in the lipid A isolated from Porphyromonas gingivalis lipopolysaccharide (LPS) was chemically synthesized, and its characteristics were evaluated to reconfirm its interesting bioactivities including low endotoxicity and activity against LPS-unresponsive C3H/HeJ mouse cells.


RESULTS
The synthesized P. gingivalis lipid A (synthetic Pg-LA) exhibited strong activities almost equivalent to those of Escherichia coli-type synthetic lipid A (compound 506) in all assays on LPS-responsive mice, and cells. LPS and native lipid A of P. gingivalis displayed overall endotoxic activities, but its potency was reduced in comparison to the synthetic analogs. In the assays using C3H/HeJ mouse cells, the LPS and native lipid A significantly stimulated splenocytes to cause mitosis, and peritoneal macrophages to induce tumor necrosis factor-alpha and interleukin-6 production. However, synthetic Pg-LA and compound 506 showed no activity on the LPS-unresponsive cells. Inhibition assays using some inhibitors including anti-human Toll-like receptor 2 (TLR2) and TLR4/MD-2 complex monoclonal antibodies showed that the biological activity of synthetic Pg-LA was mediated only through the TLR4 signaling pathway, which might act as a receptor for LPS, whereas TLR2, possibly together with CD14, was associated with the signaling cascade for LPS and native lipid A of P. gingivalis, in addition to the TLR4 pathway.


CONCLUSIONS
These results suggested that the moderated and reduced biological activity of P. gingivalis LPS and native lipid A, including their activity on C3H/HeJ mouse cells via the TLR2-mediated pathway, may be mediated by bioactive contaminants or low acylated molecules present in the native preparations having multiple lipid A moieties.
Kumada
H
H
Department of Oral Microbiology, Kanagawa Dental College, Yokosuka, Kanagawa, Japan. kumadahi@kdcnet.ac.jp
Haishima
Y
Y
Watanabe
K
K
Hasegawa
C
C
Tsuchiya
T
T
Tanamoto
K
K
Umemoto
T
T
D000818:Animals; D002478:Cells, Cultured; D004731:Endotoxins / Q000494:pharmacology; D004926:Escherichia coli / Q000737:chemistry; D005260:Female; D015850:Interleukin-6 / Q000378:metabolism; D008050:Lipid A / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000494:pharmacology*; D018950:Lipopolysaccharide Receptors / Q000187:drug effects; D051218:Lymphocyte Antigen 96 / Q000037:antagonists & inhibitors; D017737:Macrophages, Peritoneal / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D008815:Mice, Inbred Strains; D008938:Mitosis / Q000187:drug effects; D016966:Porphyromonas gingivalis / Q000737:chemistry*; D011817:Rabbits; D013154:Spleen / Q000166:cytology / Q000187:drug effects; D051195:Toll-Like Receptor 2 / Q000037:antagonists & inhibitors; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects
D004731:Endotoxins; D015850:Interleukin-6; C495377:LY96 protein, human; D008050:Lipid A; D018950:Lipopolysaccharide Receptors; D051218:Lymphocyte Antigen 96; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C049596:diphosphoryl lipid A