SIGIRR inhibits toll-like receptor 4, 5, 9-mediated immune responses in human airway epithelial cells.
Human airway epithelial cells (HAEC) may contribute to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) through toll-like receptors (TLRs)-mediated molecular mechanisms. TLRs exist on the surface of HAEC where binding to their cognate ligands initiates airway inflammation. Single immunoglobulin interleukin-1 receptor-related protein (SIGIRR) is a member of the toll-interleukin-1 receptor (TIR) family that can negatively modulate the immune response. We carried out studies to characterize SIGIRR modulation of TLR-mediated immune response in HAEC and to define its mechanisms of action. Following treatment with various concentrations of LPS, flagellin and CpG DNA, the levels of cognate TLRs 4, 5, and 9 were measured in the supernatants of HAEC over-expressing the SIGIRR molecule. Moreover, the interaction of the TLR adaptor myeloid differentiation factor 88 (MyD88) with SIGIRR in response to LPS-, flagellin- and CpG DNA-stimulation was examined by co-immunoprecipitation. The findings from this study revealed that overexpression of SIGIRR in HAEC stimulated by LPS, flagellin or CpG DNA resulted in attenuated production of the inflammatory mediators IL-6 and TNF-α. This attenuation was not the result of decreased expression of TLR4, 5 or 9, but rather a sequestration of MyD88 to the TLRs. In conclusion, SIGIRR can inhibit TLR4, 5, and 9-mediated immune responses in HAEC and may be a valuable therapeutic target for the prevention of ALI/ARDS.
Zhang
Chun
C
Institute of Respiratory Medicine, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, People's Republic of China.
Wu
Xueling
X
Zhao
Yunfeng
Y
Deng
Zhaoxia
Z
Qian
Guisheng
G
D016207:Cytokines / Q000096:biosynthesis; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D005408:Flagellin / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007109:Immunity / Q000276:immunology*; D018836:Inflammation Mediators / Q000378:metabolism; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017472:Receptors, Interleukin-1 / Q000235:genetics / Q000378:metabolism*; D012137:Respiratory System / Q000166:cytology*; D051197:Toll-Like Receptor 4 / Q000276:immunology; D051198:Toll-Like Receptor 5 / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000276:immunology; D051193:Toll-Like Receptors / Q000276:immunology*
D016207:Cytokines; D005408:Flagellin; D018836:Inflammation Mediators; D008024:Ligands; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1; D051197:Toll-Like Receptor 4; D051198:Toll-Like Receptor 5; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors; C408982:CPG-oligonucleotide; C546891:SIGIRR protein, human; C495345:TLR4 protein, human; C495346:TLR5 protein, human; C495371:TLR9 protein, human