title: Engagement of the Aryl Hydrocarbon Receptor in Mycobacterium tuberculosis-Infected Macrophages Has Pleiotropic Effects on Innate Immune Signaling.
abstract: Understanding the mechanisms of host macrophage responses to Mycobacterium tuberculosis is essential for uncovering potential avenues of intervention to boost host resistance to infection. Macrophage transcriptome profiling revealed that M. tuberculosis infection strongly induced the expression of several enzymes controlling tryptophan catabolism. These included IDO1 and tryptophan 2,3-dioxygenase, which catalyze the rate-limiting step in the kynurenine pathway, producing ligands for the aryl hydrocarbon receptor (AHR). The AHR and heterodimeric partners AHR nuclear translocator and RELB are robustly expressed, and AHR and RELB levels increased further during infection. Infection enhanced AHR/AHR nuclear translocator and AHR/RELB DNA binding and stimulated the expression of AHR target genes, including that encoding the inflammatory cytokine IL-1β. AHR target gene expression was further enhanced by exogenous kynurenine, and exogenous tryptophan, kynurenine, or synthetic agonist indirubin reduced mycobacterial viability. Comparative expression profiling revealed that AHR ablation diminished the expression of numerous genes implicated in innate immune responses, including several cytokines. Notably, AHR depletion reduced the expression of IL23A and IL12B transcripts, which encode subunits of IL-23, a macrophage cytokine that stimulates production of IL-22 by innate lymphoid cells. AHR directly induced IL23A transcription in human and mouse macrophages through near-upstream enhancer regions. Taken together, these findings show that AHR signaling is strongly engaged in M. tuberculosis-infected macrophages and has widespread effects on innate immune responses. Moreover, they reveal a cascade of AHR-driven innate immune signaling, because IL-1β and IL-23 stimulate T cell subsets producing IL-22, another direct target of AHR transactivation.
authors.affiliation: Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada;
authors.forename: Babak
authors.identifier: http://orcid.org/0000-0002-4754-6217
authors.initials: B
authors.lastname: Memari
authors.affiliation: Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada;
authors.forename: Manuella
authors.initials: M
authors.lastname: Bouttier
authors.affiliation: Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada;
authors.forename: Vassil
authors.initials: V
authors.lastname: Dimitrov
authors.affiliation: Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada;
authors.forename: Marc
authors.initials: M
authors.lastname: Ouellette
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec H3G 1Y6, Canada; Montreal General Hospital, McGill University, Montreal, Quebec H3G 1A4, Canada; McGill International TB Centre, McGill University, Montreal, Quebec H3G 1A4, Canada; Division of Infectious Diseases and Medical Microbiology, McGill University, Montreal, Quebec H3G 1A4, Canada;
authors.forename: Marcel A
authors.initials: MA
authors.lastname: Behr
authors.affiliation: Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada; Department of Microbiology and Immunology, McGill University, Montreal, Quebec H3G 0B1, Canada; and Complex Traits Group, McGill University, Montreal, Quebec H3G 0B1, Canada.
authors.forename: Jorg H
authors.initials: JH
authors.lastname: Fritz
authors.affiliation: Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada; Department of Medicine, McGill University, Montreal, Quebec H3G 1Y6, Canada; McGill International TB Centre, McGill University, Montreal, Quebec H3G 1A4, Canada; john.white@mcgill.ca.
authors.forename: John H
authors.initials: JH
authors.lastname: White
mesh_terms: D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D058685:Genetic Pleiotropy / Q000276:immunology; D054884:Host-Pathogen Interactions / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics / Q000276:immunology*; D053759:Interleukin-23 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007378:Interleukins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007739:L Cells; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008856:Microscopy, Fluorescence; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis; D034622:RNA Interference; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D051841:Transcription Factor RelB / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D059467:Transcriptome / Q000235:genetics / Q000276:immunology; D000097043:Interleukin-22
chemical_list: D053759:Interleukin-23; D007378:Interleukins; D018336:Receptors, Aryl Hydrocarbon; D051841:Transcription Factor RelB; D000097043:Interleukin-22; C497593:RELB protein, human