Global analysis of glycoproteins identifies markers of endotoxin tolerant monocytes and GPR84 as a modulator of TNF\u03b1 expression

Mario M Müller,Christoph Moore,Andrea Behnert,Roland Lehmann,Stella Reifenstein,Reinhard Guthke,Hortense Slevogt,Theresia Conrad,Tilman E Klassert,Anna Kuhn,Dominik Driesch

doi:10.1038/s41598-017-00828-y

Mario M Müller, Christoph Moore + Show 9 more

Open Access

https://doi.org/10.1038/s41598-017-00828-y

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Abstract

Exposure of human monocytes to lipopolysaccharide (LPS) induces a temporary insensitivity to subsequent LPS challenges, a cellular state called endotoxin tolerance. In this study, we investigated the LPS-induced global glycoprotein expression changes of tolerant human monocytes and THP-1 cells to identify markers and glycoprotein targets capable to modulate the immunosuppressive state. Using hydrazide chemistry and LC-MS/MS analysis, we analyzed glycoprotein expression changes during a 48 h LPS time course. The cellular snapshots at different time points identified 1491 glycoproteins expressed by monocytes and THP-1 cells. Label-free quantitative analysis revealed transient or long-lasting LPS-induced expression changes of secreted or membrane-anchored glycoproteins derived from intracellular membrane coated organelles or from the plasma membrane. Monocytes and THP-1 cells demonstrated marked differences in glycoproteins differentially expressed in the tolerant state. Among the shared differentially expressed glycoproteins G protein-coupled receptor 84 (GPR84) was identified as being capable of modulating pro-inflammatory TNFα mRNA expression in the tolerant cell state when activated with its ligand Decanoic acid.

Highlights

Glycoproteins are of particular importance for molecular and cellular recognition and for the modulation of intra- and intercellular crosstalk
Two hours of re-stimulation after 24 h and, likewise, after 48 h of pre-stimulation resulted in a pronounced attenuation of TNF-α mRNA production in monocytes and THP-1 cells, indicating that the cells entered the transient state of endotoxin tolerance
Endotoxin tolerance is a mechanism for attenuation of exuberant immune responses and is defined as transient unresponsiveness to repeated doses of LPS or other pathogen-associated molecular patterns (PAMPs), accompanied with specific alterations in gene transcription mediated by epigenic modifications[54] and altered signaling pathways downstream of toll-like receptor (TLR) activation[27]

Summary

Introduction

Glycoproteins are of particular importance for molecular and cellular recognition and for the modulation of intra- and intercellular crosstalk. Among the LPS regulated glycoproteins upregulated in both monocytes and THP-1 cells, we identified GPR84, a G protein-coupled receptor for medium-chain fatty acids. The analysis of NGP and TPG fractions of all stimulations and time points resulted in the identification of 1179 and 1189 annotated glycoproteins detected in CD14+ monocytes and THP-1 cells data sets, respectively.

Results

Conclusion