Soluble TLR2 reduces inflammation without compromising bacterial clearance by disrupting TLR2 triggering.
TLR overactivation may lead to end organ damage and serious acute and chronic inflammatory conditions. TLR responses must therefore be tightly regulated to control disease outcomes. We show in this study the ability of the soluble form of TLR2 (sTLR2) to regulate proinflammatory responses, and demonstrate the mechanisms underlying sTLR2 regulatory capacity. Cells overexpressing sTLR2, or stimulated in the presence of the sTLR2 protein, are hyporesponsive to TLR2 ligands. Regulation was TLR2 specific, and affected NF-kappaB activation, phagocytosis, and superoxide production. Natural sTLR2-depleted serum rendered leukocytes hypersensitive to TLR2-mediated stimulation. Mice administered sTLR2 together with Gram-positive bacteria-derived components showed lower peritoneal levels of the neutrophil (PMN) chemoattractant, keratinocyte-derived chemokine; lower PMN numbers; and a reduction in late apoptotic PMN. Mononuclear cell recruitment remained unaffected, and endogenous peritoneal sTLR2 levels increased. Notably, the capacity of sTLR2 to modulate acute inflammatory parameters did not compromise the ability of mice to clear live Gram-positive bacteria-induced infection. Mechanistically, sTLR2 interfered with TLR2 mobilization to lipid rafts for signaling, acted as a decoy microbial receptor, and disrupted the interaction of TLR2 with its coreceptor, CD14, by associating with CD14. These findings establish sTLR2 as a regulator of TLR2-mediated inflammatory responses, capable of blunting immune responses without abrogating microbial recognition and may inform the design of novel therapeutics against acute and chronic inflammatory conditions.
Raby
Anne-Catherine
AC
Department of Medical Biochemistry and Immunology, Cardiff University, United Kingdom.
Le Bouder
Emmanuel
E
Colmont
Chantal
C
Davies
James
J
Richards
Peter
P
Coles
Barbara
B
George
Christopher H
CH
Jones
Simon A
SA
Brennan
Paul
P
Topley
Nicholas
N
Labéta
Mario O
MO
D000208:Acute Disease; D000595:Amino Acid Sequence; D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics / Q000276:immunology; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics; D018836:Inflammation Mediators / Q000037:antagonists & inhibitors / Q000097:blood / Q000502:physiology*; D008024:Ligands; D018950:Lipopolysaccharide Receptors / Q000378:metabolism / Q000502:physiology; D021962:Membrane Microdomains / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010538:Peritonitis / Q000276:immunology* / Q000382:microbiology* / Q000473:pathology / Q000517:prevention & control; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D013203:Staphylococcal Infections / Q000276:immunology* / Q000382:microbiology* / Q000473:pathology / Q000517:prevention & control; D013212:Staphylococcus epidermidis / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000037:antagonists & inhibitors / Q000097:blood / Q000235:genetics / Q000502:physiology*
D018836:Inflammation Mediators; D008024:Ligands; D018950:Lipopolysaccharide Receptors; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2