Dose-dependent activation of microglial cells by Toll-like receptor agonists alone and in combination.
Microglial cells express Toll-like receptors (TLRs) recognising exogenous and endogenous ligands. Upon stimulation with agonists of TLR2, TLR4, and TLR9, nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) were released by primary mouse microglial cell cultures. Endotoxin was most potent in stimulating microglia followed by pneumolysin, cytosine-guanosine (CpG) oligodesoxynucleotide (ODN), and Tripalmitoyl-S-glyceryl-cysteine. Maximum stimulation of TLR2, TLR4, and TLR9 resulted in approximately equal amounts of nitric oxide release. Pneumolysin was a potent activator of microglial cells; at high concentrations, it reduced cell viability. No cytotoxicity was noted with the other TLR agonists. Costimulation with maximum concentrations of two TLR agonists did not further increase nitric oxide release. Costimulation with submaximum concentrations was additive or supraadditive, suggesting that even low concentrations of products of infectious agents can lead to microglial activation via TLRs.
Ebert
Sandra
S
Department of Neurology, University of Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany.
Gerber
Joachim
J
Bader
Steffi
S
Mühlhauser
Frank
F
Brechtel
Katrin
K
Mitchell
Timothy J
TJ
Nau
Roland
R
D000128:Acholeplasma laidlawii / Q000276:immunology; D000276:Adjuvants, Immunologic / Q000494:pharmacology / Q000633:toxicity; D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology / Q000633:toxicity; D002478:Cells, Cultured; D018899:CpG Islands / Q000276:immunology; D003545:Cysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000819:agonists* / Q000502:physiology; D004306:Dose-Response Relationship, Immunologic; D004338:Drug Combinations; D008070:Lipopolysaccharides / Q000494:pharmacology; D008074:Lipoproteins / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000819:agonists* / Q000502:physiology; D011971:Receptors, Immunologic / Q000819:agonists* / Q000502:physiology*; D013301:Streptolysins / Q000494:pharmacology / Q000633:toxicity; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9
D000276:Adjuvants, Immunologic; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004338:Drug Combinations; D008070:Lipopolysaccharides; D008074:Lipoproteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D013301:Streptolysins; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; C495370:Tlr9 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; C032290:plY protein, Streptococcus pneumoniae; D009569:Nitric Oxide; C069172:2,3-bis(palmitoyloxy)-2-propyl-1-palmitoylcysteine; D003545:Cysteine