Muramyldipeptide and diaminopimelic acid-containing desmuramylpeptides in combination with chemically synthesized Toll-like receptor agonists synergistically induced production of interleukin-8 in a NOD2- and NOD1-dependent manner, respectively, in human monocytic cells in culture.
Two types of synthetic peptidoglycan fragments, diaminopimelic acid (DAP)-containing desmuramylpeptides (DMP) and muramyldipeptide (MDP), induced secretion of interleukin (IL)-8 in a dose-dependent manner in human monocytic THP-1 cells, although high concentrations of compounds are required as compared with chemically synthesized Toll-like receptor (TLR) agonists mimicking bacterial components: TLR2 agonistic lipopeptide (Pam3CSSNA), TLR4 agonistic lipid A (LA-15-PP) and TLR9 agonistic bacterial CpG DNA. We found marked synergistic IL-8 secretion induced by MDP or DAP-containing DMP in combination with synthetic TLR agonists in THP-1 cells. Suppression of the mRNA expression of nucleotide-binding oligomerization domain (NOD)1 and NOD2 by RNA interference specifically inhibited the synergistic IL-8 secretion induced by DMP and MDP with these TLR agonists respectively. In accordance with the above results, enhanced IL-8 mRNA expression and the activation of nuclear factor (NF)-kappaB induced by MDP or DMP in combination with synthetic TLR agonists were markedly suppressed in NOD2- and NOD1-silenced cells respectively. These findings indicated that NOD2 and NOD1 are specifically responsible for the synergistic effects of MDP and DMP with TLR agonists, and suggested that in host innate immune responses to invading bacteria, combinatory dual signalling through extracellular TLRs and intracellular NODs might lead to the synergistic activation of host cells.
Uehara
A
A
Department of Microbiology and Immunology, Tohoku University Graduate School of Dentistry, Sendai 980-8575, Japan.
Yang
S
S
Fujimoto
Y
Y
Fukase
K
K
Kusumoto
S
S
Shibata
K
K
Sugawara
S
S
Takada
H
H
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000276:immunology / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D045744:Cell Line, Tumor; D004926:Escherichia coli / Q000276:immunology / Q000378:metabolism; D015870:Gene Expression; D020868:Gene Silencing; D006801:Humans; D016209:Interleukin-8 / Q000032:analysis / Q000096:biosynthesis*; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D008050:Lipid A / Q000031:analogs & derivatives / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000819:agonists*; D009000:Monocytes / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000494:pharmacology; D010457:Peptidoglycan / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000819:agonists*; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors
D048868:Adaptor Proteins, Signal Transducing; C408982:CPG-oligonucleotide; D016209:Interleukin-8; D047908:Intracellular Signaling Peptides and Proteins; D008050:Lipid A; D008562:Membrane Glycoproteins; D016328:NF-kappa B; C119067:NOD1 protein, human; C429018:NOD2 protein, human; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D009838:Oligodeoxyribonucleotides; D010457:Peptidoglycan; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; C495371:TLR9 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors; D000119:Acetylmuramyl-Alanyl-Isoglutamine