title: TAM receptor-dependent regulation of SOCS3 and MAPKs contributes to proinflammatory cytokine downregulation following chronic NOD2 stimulation of human macrophages.
abstract: Microbial-induced cytokine regulation is critical to intestinal immune homeostasis. Acute stimulation of nucleotide-binding oligomerization domain 2 (NOD2), the Crohn's disease-associated sensor of bacterial peptidoglycan, induces cytokines. However, cytokines are attenuated after chronic NOD2 and pattern recognition receptor stimulation of macrophages; similar attenuation is observed in intestinal macrophages. The role of Tyro3, Axl, and Mer (TAM) receptors in regulating chronic pattern recognition receptor stimulation and NOD2-induced outcomes has not been examined. Moreover, TAM receptors have been relatively less investigated in human macrophages. Whereas TAM receptors did not downregulate acute NOD2-induced cytokines in primary human macrophages, they were essential for downregulating signaling and proinflammatory cytokine secretion after chronic NOD2 and TLR4 stimulation. Axl and Mer were similarly required in mice for cytokine downregulation after chronic NOD2 stimulation in vivo and in intestinal tissues. Consistently, TAM expression was increased in human intestinal myeloid-derived cells. Chronic NOD2 stimulation led to IL-10- and TGF-β-dependent TAM upregulation in human macrophages, which, in turn, upregulated suppressor of cytokine signaling 3 expression. Restoring suppressor of cytokine signaling 3 expression under TAM knockdown conditions restored chronic NOD2-mediated proinflammatory cytokine downregulation. In contrast to the upregulated proinflammatory cytokines, attenuated IL-10 secretion was maintained in TAM-deficient macrophages upon chronic NOD2 stimulation. The level of MAPK activation in TAM-deficient macrophages after chronic NOD2 stimulation was insufficient to upregulate IL-10 secretion; however, full restoration of MAPK activation under these conditions restored c-Fos, c-Jun, musculoaponeurotic fibrosarcoma oncogene homolog K, and PU.1 binding to the IL-10 promoter and IL-10 secretion. Therefore, TAM receptors are critical for downregulating proinflammatory cytokines under the chronic NOD2 stimulation conditions observed in the intestinal environment.
authors.affiliation: Section of Digestive Diseases, Department of Internal Medicine, Yale University, New Haven, CT 06520.
authors.forename: Shasha
authors.initials: S
authors.lastname: Zheng
authors.affiliation: Section of Digestive Diseases, Department of Internal Medicine, Yale University, New Haven, CT 06520.
authors.forename: Matija
authors.initials: M
authors.lastname: Hedl
authors.affiliation: Section of Digestive Diseases, Department of Internal Medicine, Yale University, New Haven, CT 06520 clara.abraham@yale.edu.
authors.forename: Clara
authors.initials: C
authors.lastname: Abraham
mesh_terms: D000818:Animals; D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D003092:Colitis / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis; D015536:Down-Regulation; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D007249:Inflammation / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000276:immunology*; D053473:Nod2 Signaling Adaptor Protein / Q000276:immunology*; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000276:immunology*; D014162:Transfection
chemical_list: D016207:Cytokines; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; C106644:SOCS3 protein, human; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D020794:Receptor Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases