Stem cell transplantation uncovers TDO-AHR regulation of lung dendritic cells in herpesvirus-induced pathology
Stephen J. Gurczynski, Nicolas L. Pereira, Steven M. Hrycaj, Carol Wilke, Rachel L. Zemans, Bethany B. Moore
Stephen J. Gurczynski, Nicolas L. Pereira, Steven M. Hrycaj, Carol Wilke, Rachel L. Zemans, Bethany B. Moore
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Research Article Immunology Transplantation

Stem cell transplantation uncovers TDO-AHR regulation of lung dendritic cells in herpesvirus-induced pathology

Abstract

The aryl-hydrocarbon receptor (AHR) is an intracellular sensor of aromatic hydrocarbons that sits at the top of various immunomodulatory pathways. Here, we present evidence that AHR plays a role in controlling IL-17 responses and the development of pulmonary fibrosis in response to respiratory pathogens following bone marrow transplant (BMT). Mice infected intranasally with gamma-herpesvirus 68 (γHV-68) following BMT displayed elevated levels of the AHR ligand, kynurenine (kyn), in comparison with control mice. Inhibition or genetic ablation of AHR signaling resulted in a significant decrease in IL-17 expression as well as a reduction in lung pathology. Lung CD103+ DCs expressed AHR following BMT, and treatment of induced CD103+ DCs with kyn resulted in altered cytokine production in response to γHV-68. Interestingly, mice deficient in the kyn-producing enzyme indolamine 2-3 dioxygenase showed no differences in cytokine responses to γHV-68 following BMT; however, isolated pulmonary fibroblasts infected with γHV-68 expressed the kyn-producing enzyme tryptophan dioxygenase (TDO2). Our data indicate that alterations in the production of AHR ligands in response to respiratory pathogens following BMT results in a pro-Th17 phenotype that drives lung pathology. We have further identified the TDO2/AHR axis as a potentially novel form of intercellular communication between fibroblasts and DCs that shapes immune responses to respiratory pathogens.

Authors

Stephen J. Gurczynski, Nicolas L. Pereira, Steven M. Hrycaj, Carol Wilke, Rachel L. Zemans, Bethany B. Moore

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Figure 1

Ablation of AHR signaling rescues γHV-68–induced fibrosis following BMT.

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Ablation of AHR signaling rescues γHV-68–induced fibrosis following BMT....
(A) Concentration of kyn was assessed in whole-lung homogenates by ELISA from groups of BMT (mean ± SEM, n = 5) or non-BMT (mean ± SEM, n = 5) mice infected with γHV-68 or mock infected for 7 days. (B) Relative quantity of Cyp1b1 transcript was determined from lung leukocytes isolated from collagenase-digested lungs of either non-BMT (shown as mean ± SEM, vehicle treated n = 5, kyn treated n = 4, CH223191 treated n = 4) or BMT (shown as mean ± SEM, vehicle treated n = 3, kyn treated n = 5, CH223191 treated n = 5) mice infected with γHV-68 for 7 days. (C) Groups of non-BMT or BMT mice were infected with γHV-68 and treated with the AHR inhibitor, CH223191, 10 μg, every 2 days for 14 days. At 21 dpi lungs were harvested, and collagen content was assessed by hydroxyproline assay (shown as mean ± SEM, non-BMT n = 5, BMT + vehicle n = 4, BMT + CH223191 n = 5). (D) Sections from formalin-fixed paraffin-embedded mouse lung were prepared and stained with H&E or trichrome to detect collagen. Statistical significance was determined by ANOVA, *P < 0.05, **P < 0.01.