Neutrophils induce macrophage anti-inflammatory reprogramming by suppressing NF-\u03baB activation

John A Marwick,Jillian Stephen,Adriano G Rossi,Nikhil Hirani,Oliver Kay,Ross Mills,Ian Dransfield,Kyriakos Michail

doi:10.1038/s41419-018-0710-y

Abstract

Apoptotic cells modulate the function of macrophages to control and resolve inflammation. Here, we show that neutrophils induce a rapid and sustained suppression of NF-κB signalling in the macrophage through a unique regulatory relationship which is independent of apoptosis. The reduction of macrophage NF-κB activation occurs through a blockade in transforming growth factor β-activated kinase 1 (TAK1) and IKKβ activation. As a consequence, NF-κB (p65) phosphorylation is reduced, its translocation to the nucleus is inhibited and NF-κB-mediated inflammatory cytokine transcription is suppressed. Gene Set Enrichment Analysis reveals that this suppression of NF-κB activation is not restricted to post-translational modifications of the canonical NF-κB pathway, but is also imprinted at the transcriptional level. Thus neutrophils exert a sustained anti-inflammatory phenotypic reprogramming of the macrophage, which is reflected by the sustained reduction in the release of pro- but not anti- inflammatory cytokines from the macrophage. Together, our findings identify a novel apoptosis-independent mechanism by which neutrophils regulate the mediator profile and reprogramming of monocytes/macrophages, representing an important nodal point for inflammatory control.

Highlights

Apoptotic cells modulate the function of macrophages to control and resolve inflammation
We sought to address the question of whether the LPS-induced macrophage cytokine profile was modulated by co-culture with either viable or apoptotic neutrophils and, if so, whether they exert differential effects? We measured the release of TNF induced by LPS from human monocyte-derived macrophages (MDMs) which were cocultured for 6 h with either viable or apoptotic populations from three distinct human immune cell lineages; blood neutrophils, T cells (Jurkat cell line) and B cells (BL-2 cell line)
We extended our analysis to include blood monocytes, inflammatory (IFN-γ) primed MDMs and primary human alveolar macrophages (Fig. 1c), all of which showed a reduction in LPS-induced TNF release when co-cultured in the presence of either viable or apoptotic neutrophils

Summary

Introduction

Apoptotic cells modulate the function of macrophages to control and resolve inflammation. Studies focusing on the effect of apoptotic neutrophils show a reduction in TLR4-induced release of inflammatory cytokines from macrophages (e.g., TNF and CXCL8)[4]. This implicates an involvement of NF-κB, which is activated through canonical TLR4 signalling to facilitate the transcription of inflammatory mediators such as TNF and CXCL-810,11. There are no studies relating to whether viable and apoptotic neutrophils exert distinct effects on NF-κB activation to modulate macrophage mediator profiles and whether these regulatory mechanisms are present in human cells. We use primary human cells to address the key questions of whether neutrophils modulate the inflammatory signalling of macrophages by suppressing NF-κB activation and whether this modulation differs once the apoptotic program is engaged

Methods

Results

Conclusion