Epigenetic and transcriptional regulation of IL4-induced CCL17 production in human monocytes and murine macrophages

Amy T Hsu,Tanya J Lupancu,Ming-Chin Lee,Andrew J Fleetwood,Andrew D Cook,John A Hamilton,Adrian Achuthan

doi:10.1074/jbc.ra118.002416

Abstract

Interleukin 4 (IL4) is generally viewed as a Th2 cytokine capable of polarizing macrophages into an anti-inflammatory phenotype, whereas granulocyte macrophage-colony-stimulating factor (GM-CSF) is often viewed as a proinflammatory cytokine with part of this function due to its action on monocytes/macrophages. Paradoxically, these two cytokines act additively to enhance the in vitro differentiation of dendritic cells from precursors such as monocytes. One up-regulated marker of an IL4-polarized M2 macrophage is the chemokine (C-C motif) ligand 17 (CCL17), which we have recently reported to be induced by GM-CSF in monocytes/macrophages in an interferon regulatory factor 4 (IRF4)-dependent manner. In this study, we report that IL4 also induces CCL17 production by acting through IRF4 in human monocytes and murine macrophages. Furthermore, evidence is presented that IL4 up-regulates IRF4 expression at the epigenetic level by enhancing the expression and activity of jumonji domain-containing protein 3 (JMJD3) demethylase. Intriguingly, silencing the signal transducer and activator of transcription 6 (STAT6) gene led to a decrease in not only CCL17 formation, but also in that of its upstream regulators, JMJD3 and IRF4. Moreover, IL4 treatment of human monocytes resulted in an increased association of STAT6 to the promoter regions of the CCL17, IRF4, and JMJD3 genes. Thus, despite their vastly different functions, IL4 and GM-CSF appear to share elements of a common signaling pathway in regulating CCL17 production in human monocytes and murine macrophages.

Highlights

Cells of the monocyte/macrophage lineage are involved in host defense and inflammation, including in the resolution phase leading to homeostasis [1]
We have recently shown that granulocyte macrophage-colony-stimulating factor (GM-CSF) can induce CCL17 production in human monocytes and murine macrophages in an interferon regulatory factor 4 (IRF4)-dependent manner [29]; we demonstrated that GM-CSF–mediated up-regulation of IRF4 expression was in turn dependent on increased JMJD3 activity
We have reported that GM-CSF can induce CCL17 mRNA and protein secretion in human monocytes and murine bone marrow– derived macrophages (BMM) [29]

Summary

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Molecular mechanism of IL4-induced CCL17 production these sites is usually associated with repression of transcription, JMJD3 activity is expected to enhance gene expression. We have recently shown that GM-CSF can induce CCL17 production in human monocytes and murine macrophages in an IRF4-dependent manner [29]; we demonstrated that GM-CSF–mediated up-regulation of IRF4 expression was in turn dependent on increased JMJD3 activity. Given the above background literature on IL4 and GM-CSF, either alone or combination, we considered that IL4 might induce CCL17 production in the monocyte/macrophage population via a similar pathway.

Results

Discussion

Experimental procedures