Lipoteichoic acid-induced lung inflammation depends on TLR2 and the concerted action of TLR4 and the platelet-activating factor receptor.
Lipoteichoic acid (LTA) is a major outer cell wall component of Gram-positive bacteria that has been implicated as an important factor in the inflammatory response following bacterial infection. In vitro data indicate roles for TLR2, platelet-activating factor receptor (PAFR), CD14, and LPS-binding protein (LBP) in cellular responsiveness to LTA, whereas the mechanisms contributing to LTA effects in vivo have never been investigated. Using mice deficient for LBP, CD14, TLR2, TLR4, or PAFR, we now examined the role of these molecules in pulmonary inflammation induced by highly purified LTA in vivo. Although pulmonary LBP increased dose-dependently following administration of LTA, the inflammatory response was unaltered in LBP-/- mice. TLR2 proved to be indispensable for the initiation of an inflammatory response, as polymorphonuclear cell influx, TNF-alpha, keratinocyte-derived chemokine, and MIP-2 release were abolished in TLR2-/- mice. Minor effects such as moderately decreased TNF-alpha and MIP-2 levels were observed in the absence of CD14, indicating a role for CD14 as a coreceptor. Quite surprisingly, the absence of TLR4 greatly diminished pulmonary inflammation and the same phenotype was observed in PAFR-/- animals. In contrast to all other mice studied, only TLR4-/- and PAFR-/- mice displayed significantly elevated IL-10 pulmonary concentrations. These data suggest that TLR2 is the single most important receptor signaling the presence of LTA within the lungs in vivo, whereas TLR4 and PAFR may influence lung inflammation induced by LTA either by sensing LTA directly or through recognition and signaling of endogenous mediators induced by the interaction between LTA and TLR2.
Knapp
Sylvia
S
Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. sylvia.knapp@meduniwien.ac.at
von Aulock
Sonja
S
Leendertse
Masja
M
Haslinger
Isabella
I
Draing
Christian
C
Golenbock
Douglas T
DT
van der Poll
Tom
T
D000208:Acute Disease; D000818:Animals; D002460:Cell Line; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000008:administration & dosage* / Q000378:metabolism / Q000502:physiology; D018950:Lipopolysaccharide Receptors / Q000378:metabolism / Q000502:physiology; D008070:Lipopolysaccharides / Q000008:administration & dosage* / Q000378:metabolism; D008168:Lung / Q000276:immunology* / Q000382:microbiology / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010972:Platelet Activating Factor / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D018410:Pneumonia, Bacterial / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D011650:Pulmonary Alveoli / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D043562:Receptors, G-Protein-Coupled / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D013682:Teichoic Acids / Q000008:administration & dosage* / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
D018836:Inflammation Mediators; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; D013682:Teichoic Acids; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C039351:platelet activating factor receptor; C009900:lipoteichoic acid