Characterization of signaling pathways regulating the expression of pro-inflammatory long form thymic stromal lymphopoietin upon human metapneumovirus infection

Youxian Li,Marit W Anthonsen,Ingvild B Johnsen,Henrik Døllner,Cecilie Lund,Ida Nervik,Simon Loevenich

doi:10.1038/s41598-018-19225-0

Youxian Li, Marit W Anthonsen + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-19225-0

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Abstract

Thymic stromal lymphopoietin (TSLP) is associated with several allergic diseases including asthma. Two isoforms of TSLP exist in humans, a long form (lfTSLP) and a short form (sfTSLP), displaying distinct immunological functions. Recently, TSLP was found to be upregulated in human airway cells upon human metapneumovirus (hMPV) infection, yet it remains unclear if the two isoforms are regulated differently during hMPV infection. Importantly, the molecular mechanisms underlying hMPV-mediated TSLP induction remain undescribed. In this study, we characterized the expression and regulation of TSLP in hMPV-infected human airway cells. We demonstrated that hMPV strongly induced the expression of pro-inflammatory lfTSLP in human airway epithelial cells and lung fibroblasts. Further, knockdown of pattern recognition receptors retinoic acid-inducible gene I (RIG-I) or Toll-like receptor 3 (TLR3), as well as downstream signal transducers, abrogated hMPV-mediated lfTSLP induction. Importantly, silencing of TANK-binding kinase 1 (TBK1) also impaired hMPV-mediated lfTSLP induction, which could be attributed to compromised NF-κB activation. Overall, these results suggest that TBK1 may be instrumental for hMPV-mediated activation of NF-κB downstream RIG-I and TLR3, leading to a specific induction of lfTSLP in hMPV-infected human airway cells.

Highlights

Respiratory tract infections (RTIs) are a major cause of childhood mortality and morbidity worldwide, especially in developing countries[1]
Importantly, to examine if the two Thymic stromal lymphopoietin (TSLP) isoforms are differentially expressed during human metapneumovirus (hMPV) infection, we assessed the gene expression of lfTSLP and sfTSLP in three different cell lines derived from human respiratory system: two human airway epithelial cell lines (BEAS-2B and A549) and a human fetal lung fibroblast cell line (WI-38)
Cells were infected by hMPV at multiplicity of infection (MOI) 1 and mRNA expression levels of lfTSLP and sfTSLP were determined by quantitative real-time PCR

Summary

Introduction

Respiratory tract infections (RTIs) are a major cause of childhood mortality and morbidity worldwide, especially in developing countries[1]. TSLP has been shown to be upregulated in human airway epithelial cells upon infection with respiratory viruses, such as rhinovirus (RV), respiratory syncytial virus (RSV) and hMPV, providing a possible link between viral infections and asthma pathogenesis[16,17,18]. TSLP-conditioned DCs prime naïve T cells to differentiate into a T-helper type 2 (Th2) phenotype, producing cytokines involved in allergic inflammation including IL-4, IL-5, IL-13, and TNF-α20,21. Recent studies suggest that lfTSLP is induced by pro-inflammatory signals and associated with allergic inflammation, whilst sfTSLP is constitutively expressed and may have an anti-inflammatory or anti-microbial role[22,23,24]. We examined the differential expression of lfTSLP and sfTSLP in human airway epithelial cells and lung fibroblasts upon hMPV infection. We further investigated the signaling pathways mediating hMPV-induced lfTSLP expression using human lung fibroblasts as the model system

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