Bilirubin suppresses Th17 immunity in colitis by upregulating CD39
Maria Serena Longhi, … , Francisco J. Quintana, Simon C. Robson
Maria Serena Longhi, … , Francisco J. Quintana, Simon C. Robson
Published May 4, 2017
Citation Information: JCI Insight. 2017;2(9):e92791. https://doi.org/10.1172/jci.insight.92791.
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Research Article Gastroenterology Immunology

Bilirubin suppresses Th17 immunity in colitis by upregulating CD39

Abstract

Unconjugated bilirubin (UCB), a product of heme oxidation, has known immunosuppressant properties but the molecular mechanisms, other than antioxidant effects, remain largely unexplored. We note that UCB modulates T helper type 17 (Th17) immune responses, in a manner dependent upon heightened expression of CD39 ectonucleotidase. UCB has protective effects in experimental colitis, where it enhances recovery after injury and preferentially boosts IL-10 production by colonic intraepithelial CD4+ cells. In vitro, UCB confers immunoregulatory properties on human control Th17 cells, as reflected by increased levels of FOXP3 and CD39 with heightened cellular suppressor ability. Upregulation of CD39 by Th17 cells is dependent upon ligation of the aryl hydrocarbon receptor (AHR) by UCB. Genetic deletion of CD39, as in Entpd1–/– mice, or dysfunction of AHR, as in Ahrd mice, abrogates these UCB salutary effects in experimental colitis. However, in inflammatory bowel disease (IBD) samples, UCB fails to confer substantive immunosuppressive properties upon Th17 cells, because of decreased AHR levels under the conditions tested in vitro. Immunosuppressive effects of UCB are mediated by AHR resulting in CD39 upregulation by Th17. Boosting downstream effects of AHR via UCB or enhancing CD39-mediated ectoenzymatic activity might provide therapeutic options to address development of Th17 dysfunction in IBD.

Authors

Maria Serena Longhi, Marta Vuerich, Alireza Kalbasi, Jessica E. Kenison, Ada Yeste, Eva Csizmadia, Byron Vaughn, Linda Feldbrugge, Shuji Mitsuhashi, Barbara Wegiel, Leo Otterbein, Alan Moss, Francisco J. Quintana, Simon C. Robson

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Figure 3

UCB confers Th17 regulatory properties in healthy subjects but not in Crohn’s disease patients.

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UCB confers Th17 regulatory properties in healthy subjects but not in Cr...
Frequencies of FOXP3+, CD39+, and CD73+ cells were determined after polarizing CD4+ cells under Th17 conditions and UCB treatment. Cells were initially gated on CD4+IL-17+ and the frequency of FOXP3+, CD39+, and FOXP3+ lymphocytes determined. CD4 and FOXP3 (A) or CD39 (B) fluorescence of Th17 cells. Mean ± SEM frequency of FOXP3+ and CD39+ lymphocytes within Th17 cells is also shown (n = 12 HS and n = 10 Crohn’s). (C) Mean ± SEM frequency of CD73+ cells within CD39+ Th17 (n = 12 HS and n = 10 Crohn’s). (D) Mean ± SEM frequency of FOXP3+, CD39+, and CD73+ lymphocytes within LPMC-derived Th17 cells (n = 14 Crohn’s). (E–G) Mean ± SEM frequency of FOXP3+, CD39+, and CD73+ lymphocytes within LPMC-derived Th17 cells from noninflamed and inflamed colon areas (n = 5 Crohn’s). (H) Suppressive function of untreated and UCB-treated Th17 was assessed following sorting of CCR6+CXCR3– cells from CD4+ lymphocytes polarized under Th17 conditions. CD4, IL-17, CCR6, and CXCR3 fluorescence from 1 HS is shown. (I) Mean ± SEM percentage inhibition of IL-17 and IFN-γ production by CD4+CD25– responders in the presence of untreated or UCB-treated Th17 cells (n = 15 HS and n = 15 Crohn’s). (J) Mean ± SEM free phosphate concentrations in the supernatant of Th17 cells (n = 5 HS and n = 5 Crohn’s). P values derived using 1-way ANOVA followed by Tukey’s multiple comparisons test. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. HS, healthy subjects; UCB, unconjugated bilirubin; LPMCs, lamina propria–derived mononuclear cells.