Bilirubin suppresses Th17 immunity in colitis by upregulating CD39
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
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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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 2

UCB boosts IL-10 expression in human Th17 cells.

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UCB boosts IL-10 expression in human Th17 cells. (A) CD4 cells were pola...
(A) CD4 cells were polarized in the presence of Th17-skewing conditions; on day 6, cells were exposed to UCB. Cells were initially gated on CD4+IL-17+ lymphocytes, and then the frequency of IL-10+ cells within the CD4+IL-17+ subset was measured. Representative dot plot of CD4 and IL-17 fluorescence and contour plots of CD4 and IL-10 fluorescence in the absence and presence of UCB are shown. Mean ± SEM frequency of IL-10–producing cells in untreated and UCB-treated Th17 cells (n = 8 healthy subjects [HS]). (B) Histogram of IL-10 MFI of untreated and UCB-treated Th17 cells from a representative healthy control. Cumulative data from n = 8 HS are also shown. (C) Mean ± SEM relative IL10 mRNA expression in untreated and UCB-treated Th17 cells (n = 22 HS). (D) Histograms of IL-17, RORC, IL-23R, and CCR6 MFI from a representative healthy control. Mean ± SEM frequency of IL-17+, RORC+, IL-23R+, and CCR6+ lymphocytes within untreated and UCB-treated Th17 cells from n = 8 HS is also shown. (E) Mean ± SEM relative IL22 and IL1B mRNA expression in untreated and UCB-treated Th17 cells (n = 12 HS). (F) Mean ± SEM cpm of untreated and UCB-treated Th17 cells (n = 5 HS). (G) Mean ± SEM frequency of annexin V+ cells within untreated and UCB-treated Th17 cells (n = 5 HS). P values derived using paired t test. *P ≤ 0.05. UCB, unconjugated bilirubin; MFI, mean fluorescence intensity; RORC, RAR-related orphan receptor C; IL-23R, IL-23 receptor.