Role of NF-kB RelB in Aryl Hydrocarbon Receptor-Mediated Ligand Specific Effects.

Yasuhiro Ishihara,Christoph F A Vogel,Christiane Hoeper,Shelly Harel,Sarah Y Kado

doi:10.3390/ijms20112652

Abstract

Here, we investigate the role of RelB in the regulation of genes which were identified to be induced in an aryl hydrocarbon receptor (AhR)-dependent manner and critically involved in regulation of immune responses. We analyzed the expression of genes of the AhR gene battery, cytokines, and immune regulatory enzymes in bone marrow-derived macrophages (BMM) and thymus of B6 wildtype (wt) mice and RelB knockout (RelB−/−) mice after treatment with various AhR ligands. The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced expression of indoleamine 2,3-dioxygenase 1 (IDO1) and IDO2 was significantly repressed in thymus of RelB−/− mice but not in BMM derived from RelB−/− mice. Interestingly, the induced and basal expression of the cytokines interleukin (IL)-17A, IL-22, and CCL20 required the functional expression of RelB. The RelB-dependent expression of CCL20 was induced by the AhR ligands TCDD and 6-formylindolo[3,2-b]carbazole (FICZ), whereas indole-3-carbinol (I3C) suppressed CCL20 in lipopolysaccharide (LPS)-activated wt BMM. The LPS-induced expression of IL-6 and IL-10 was enhanced by TCDD and FICZ, whereas I3C significantly suppressed these cytokines in BMM. The exposure to FICZ led to higher increases of IL-17A and IL-22 mRNA compared to the effect of TCDD or I3C in thymus of wt mice. On the other hand, TCDD was the strongest inducer of CYP1A1, AhR Repressor (AhRR), and IDO2. In summary, these findings provide evidence for the important role of RelB in the transcriptional regulation of cytokines and enzymes induced by AhR ligands.

Highlights

The mechanism of transcriptional activation of CYP1A1 and other genes of the aryl hydrocarbon receptor (AhR) gene battery has been well studied
We found that the constitutive, TLR4- and AhR-mediated transcriptional activation of the cytokines IL-17A and CCL20 ex vivo in bone marrow-derived macrophages (BMM) and in thymus of B6 mice require NF-κB RelB
The IL-22 expression induced by LPS and TCDD was repressed in BMM and thymus of RelB-deficient mice

Summary

Introduction

The mechanism of transcriptional activation of CYP1A1 and other genes of the AhR gene battery has been well studied. Deficiency or alteration of the activity of AhR and NF-κB RelB have been shown to affect development of T lymphocytes and DCs associated with immunodeficiency and autoimmunity [17,19,20,24,25]. Since both signaling pathways, AhR and NF-κB, are interacting and regulating the function of innate immune cells, it is important to examine the role of RelB in responses mediated by AhR ligands. The current study investigates the function of RelB as an important regulator of the mRNA expression of cytokines and immune regulatory enzymes in thymus and bone marrow-derived macrophages (BMM) mediated by AhR ligands

Results and Discussion

Reagents and Antibodies

Animals and Cell Culture

RNA Isolation and Quantitative Real-Time RT-PCR

Statistics

Conclusions