ER stress abrogates the immunosuppressive effect of IL-10 on human macrophages through inhibition of STAT3 activation

Jeroen Den Dunnen,Ivo S Hansen,Josca M Schoonejans,Lathees Sritharan,Carmen A Ambarus,Dominique L P Baeten,Johan A Van Burgsteden

doi:10.1007/s00011-019-01261-9

Jeroen Den Dunnen, Ivo S Hansen + Show 5 more

Open Access

https://doi.org/10.1007/s00011-019-01261-9

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Abstract

Objective and designTo determine whether ER stress affects the inhibitory pathways of the human immune system, particularly the immunosuppressive effect of IL-10 on macrophages.Material or subjectsIn vitro stimulation of human monocyte-derived macrophages.TreatmentCells were stimulated with TLR ligands and IL-10, while ER stress was induced using thapsigargin or tunicamycin.MethodsmRNA expression was determined using qPCR, while cytokine protein production was measured using ELISA. Protein expression of receptors and transcription factors was determined using flow cytometry. Student’s t test was used for statistics.ResultsWhile under normal conditions IL-10 potently suppresses pro-inflammatory cytokine production by LPS-stimulated macrophages, we demonstrate that ER stress counteracts the immunosuppressive effects of IL-10, leading to increased pro-inflammatory cytokine production. We identified that ER stress directly interferes with IL-10R signaling by reducing STAT3 phosphorylation on Tyr705, which thereby inhibits the expression of SOCS3. Moreover, we show that ER stress also inhibits STAT3 activation induced by other receptors such as IL-6R.ConclusionsCombined, these data uncover a new general mechanism by which ER stress promotes inflammation. Considering its potential involvement in the pathogenesis of diseases such as Crohn’s disease and spondyloarthritis, targeting of this mechanism may provide new opportunities to counteract inflammation.

Highlights

The mechanisms triggering immune activation and inflammation during normal host defense responses are currently well understood
To assess if endoplasmic reticulum (ER) stress impacts the regulation of inflammation, we investigated the effect of IL-10 on inflammatory macrophage responses in the presence or absence of ER stress
Stimulation of human GMCSF differentiated macrophages with LPS induced the production of pro-inflammatory cytokine TNF, which was potently inhibited by the addition of IL-10 (Fig. 1a)

Summary

Introduction

The mechanisms triggering immune activation and inflammation during normal host defense responses are currently well understood. This includes the rapid recognition of pathogens by the innate immune system, which is mediated by detection of molecular patterns expressed as structural component of microorganisms by various innate immune cells. These molecular patterns, such as lipopolysaccharide (LPS) or flagellin, are recognized by a group of receptors called pattern recognition receptors (PRR) [1]. Infants with loss-of-function mutations in the IL-10R are unable to downregulate LPS-induced macrophage activation and suffer from dramatic inflammatory bowel disease [4]

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