Toll-like receptor ligands induce polymorphonuclear leukocyte migration: key roles for leukotriene B4 and platelet-activating factor.
Activation of toll-like receptors (TLRs) and polymorphonuclear leukocyte (PMN) accumulation at infection sites are critical events of host defense. The involvement of leukotriene (LT) B(4) and platelet-activating factor (PAF) in TLR ligand-induced activation of inflammatory cell functions is essentially unknown. Using an in vitro model of human PMN migration through human endothelial cell monolayers, we demonstrate that prototypic ligands of TLR1/2, 2/6, 3, 4, 5, and 7/8 promote PMN migration, an effect markedly inhibited by 3 LTB(4) receptor antagonists (70-80% inhibition at 100 nM compared to vehicle-treated cells), 3 PAF receptor antagonists (20-50% inhibition at 10 nM), 3 LT biosynthesis inhibitors (75-85% inhibition at 100 nM), and 1 cytosolic phospholipase A(2)alpha (cPLA(2)alpha) inhibitor (90% inhibition at 1 microM). Accordingly, selected TLR ligands caused Ser-505-phosphorylation of cPLA(2)alpha and measurable LTB(4) and PAF biosynthesis in the transmigration assay. As negative controls, interleukin-8- and formyl-methionyl-leucyl-phenylalanine-elicited migration in vitro was not inhibited either by an LTB(4) receptor antagonist or by the cPLA(2)alpha inhibitor. Finally, LTB(4) and PAF receptor antagonists inhibited (up to approximately 65% at optimal doses) TLR ligand-induced PMN infiltration in the mouse air-pouch model. These studies unravel the critical involvement of de novo LTB(4) and PAF biosynthesis in PMN migration elicited by TLR ligands.
Lefebvre
Julie S
JS
Centre de Recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec, 2705 Laurier Blvd., Rm. T1-49, Québec, QC, Canada, G1V 4G2.
Marleau
Sylvie
S
Milot
Valérie
V
Lévesque
Tania
T
Picard
Serge
S
Flamand
Nicolas
N
Borgeat
Pierre
P
D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002465:Cell Movement / Q000187:drug effects*; D004095:Dihydropyridines / Q000494:pharmacology; D005260:Female; D005408:Flagellin / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007975:Leukotriene B4 / Q000502:physiology*; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000502:physiology*; D010972:Platelet Activating Factor / Q000502:physiology*; D011070:Poly I-C / Q000494:pharmacology; D011422:Propionates / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D058924:Thienopyridines; D051193:Toll-Like Receptors / Q000819:agonists / Q000276:immunology / Q000502:physiology*; D014230:Triazoles / Q000494:pharmacology
D001381:Azepines; D004095:Dihydropyridines; D007093:Imidazoles; D008024:Ligands; D010972:Platelet Activating Factor; D011422:Propionates; D011804:Quinolines; D058924:Thienopyridines; D051193:Toll-Like Receptors; D014230:Triazoles; C052518:WEB 2086; D005408:Flagellin; C066686:BN 50730; C073027:modipafant; D007975:Leukotriene B4; C059141:verlukast; D011070:Poly I-C