title: The early induction of suppressor of cytokine signaling 1 and the downregulation of toll-like receptors 7 and 9 induce tolerance in costimulated macrophages.
abstract: Toll-like receptors (TLR) 7 and 9 transduce a cellular signal through the MyD88-dependent pathway and induce the production of inflammatory mediators against microbial nucleotide components. The repeated stimulation of TLR4 leads to endotoxin tolerance, but the molecular mechanisms of tolerance induced through the costimulation of individual TLR has not yet been established, although endosomal TLRs share signaling pathways with TLR4. In the present study, mouse macrophages were simultaneously stimulated with the TLR7 agonist, gardiquimod (GDQ), and the TLR9 agonist, CpG ODN 1826, to examine the mechanism and effector functions of macrophage tolerance. Compared with individual stimulation, the costimulation of both TLRs reduced the secretion of TNF-α and IL-6 through the delayed activation of the NF-κB pathway; notably, IL-10 remained unchanged in costimulated macrophages. This tolerance reflected the early induction of suppressor of cytokine signaling-1 (SOCS-1), according to the detection of elevated TNF-α secretion and restored NF-κB signaling in response to the siRNA-mediated abrogation of SOCS-1 signaling. In addition, the restimulation of each TLRs using the same ligand significantly reduced the expression of both TLRs in endosomes. These findings revealed that the costimulation of TLR7 and TLR9 induced macrophage tolerance via SOCS-1, and the restimulation of each receptor or both TLR7 and TLR9 downregulated TLR expression through a negative feedback mechanisms that protects the host from excessive inflammatory responses. Moreover, the insufficient and impaired immune response in chronic viral infection might also reflect the repeated and simultaneous stimulation of those endosomal TLRs.
authors.affiliation: BIT Medical Convergence Graduate Program, Kangwon National University, Chuncheon 200-701, Korea ; Department of Biological Sciences, Kangwon National University, Chuncheon 200-701, Korea.
authors.forename: Hyo-Ji
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Biological Sciences, Kangwon National University, Chuncheon 200-701, Korea.
authors.forename: Keun-Cheol
authors.initials: KC
authors.lastname: Kim
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, Kangwon National University, Chuncheon 200-701, Korea.
authors.forename: Jeong A
authors.initials: JA
authors.lastname: Han
authors.affiliation: Department of Medical Biotechnology, Kangwon National University, Chuncheon 200-701, Korea.
authors.forename: Sun Shim
authors.initials: SS
authors.lastname: Choi
authors.affiliation: BIT Medical Convergence Graduate Program, Kangwon National University, Chuncheon 200-701, Korea ; Department of Biological Sciences, Kangwon National University, Chuncheon 200-701, Korea.
authors.forename: Yu-Jin
authors.initials: YJ
authors.lastname: Jung
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D015536:Down-Regulation; D005786:Gene Expression Regulation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007108:Immune Tolerance; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D008297:Male; D008562:Membrane Glycoproteins / Q000819:agonists / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D051199:Toll-Like Receptor 7 / Q000819:agonists / Q000378:metabolism*; D051217:Toll-Like Receptor 9 / Q000819:agonists / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; C423449:CpG ODN 1826; D016207:Cytokines; D007093:Imidazoles; D008562:Membrane Glycoproteins; D009838:Oligodeoxyribonucleotides; C491590:Socs1 protein, mouse; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C477038:Tlr7 protein, mouse; C495370:Tlr9 protein, mouse; D051199:Toll-Like Receptor 7; D051217:Toll-Like Receptor 9; C546771:gardiquimod
keywords: NF-κB; SOCS-1; TLRs; inflammation; macrophage; tolerance