Polarization State of Macrophages Affects Their Expression of Upstream TH2-Cytokines and Interferon-Beta Signalling Pathway in Response to Rhinovirus Infection

Abstract

Introduction: TH2-upstream cytokines (IL-33, IL-25 and TSLP) have emerged as key cytokines in the promotion of allergic asthma. Macrophages (Mϕs) play an important role in the pathogenesis of asthma both in the inflammatory and resolution phases of the disease. Mϕs can acquire different phenotypes depending on their microenvironment. Our aim was to investigate the difference in expression of TH2-upstream cytokines and IFN-ß signalling in response to rhinovirus (RV) and a viral surrogate (PolyI:C) in different cytokine milieus.
Methods: THP-1 (Human monocytic cell line) was polarized into M1 and M2 by TH1- or TH2-cytokines, respectively, while murine wildtype (C57BL/6), NF-κB-/- and IRF3-/- bone marrow derived Mϕs were treated with M-CSF or GM-CSF. Cells were stimulated with PolyI:C alone or with house-dust mite pre-treatment or RV16/RV1B alone. Gene and protein expression for IL-33, IL-25, TSLP, IRF4, TLR3, RIG-I, MDA5, IFN-ß and viral RNA were measured by RT-qPCR and western blot.
Results: We observed that GM-CSF –treated mouse Mϕs had higher basal gene expression of IL-33 compared to M-CSF –treated Mϕs. This was further increased by PolyI:C. TSLP was induced in M-CSF-treated Mϕs in response to PolyI:C and RV1B. In human Mϕs we saw an increased basal gene expression of IL-33 in a TH2 cytokine milieu compared to TH1. IL-25 was induced in response to RV in TH1- compared to TH2-cytokine milieu. TH2-cytokine milieu in human Mϕs and GM-CSF milieu in mouse Mϕs caused reduced TLR3, RIG-I and MDA5 expression leading to a reduced IFN-ß response compared to TH1-cytokine and M-CSF milieu in response to RV and PolyI:C.
Conclusion: This study showed that microenvironment which Mϕs reside in affects their expression of TH2-upstream cytokines, at basal level and also in response to RV and PolyI:C. Our data showed that polarization state of Mϕs can affect the dependency of these cytokines on different signalling pathways. Mϕs in TH2 and GM-CSF cytokine milieu have lower expression of PRRs and anti-viral IFN-β in response to RV infection. These findings can have clinical implications in viral-induced asthma exacerbations.

Popular Abstract

The micro-environment of the most abundant immune cells in the airways affects their response to common cold virus

Asthma is a chronic inflammatory disease causing obstruction of the airways, making it harder to breathe. The common cold virus among other respiratory viruses causes periods of worsening in symptoms called exacerbations which does not happen in healthy individuals. These episodes are difficult to treat and are a major burden for patients and health system. In any inflammatory disease such as asthma, different types of immune cells may play a role. Macrophages are one of the most numerous immune cells in the lungs. These cells have an interesting characteristic which is their flexibility. These cells can change their function depending on the micro-environment which they encounter. They can have completely opposite roles in different milieus. During respiratory viral infections structural and immune cells secrete various proteins with different functions. In this study we investigated the production of three mediators by macrophages and the effect of different micro-environments on this production. These three mediators have recently been associated with allergic type of inflammation, which may worsen the ongoing inflammation in asthmatic patients and lead to worsening of their symptoms. These three mediators work as a bridge between non-specific and specific immune response. The interesting feature of these three is that, they can start an allergic inflammation in response to respiratory viruses. In asthmatic patients the levels of these three mediators have been shown to be higher. Researchers have suggested that asthmatic patients may have an impaired anti-viral response which may lead to severe clinical symptoms compared to healthy individuals. So we studied the anti-viral response of macrophages in different milieus.
We used human and mouse macrophages and grew them in two different types of micro-environments. One of these environments is similar to what exists in allergic asthmatic patients. We then infected the macrophages with common cold virus or stimulated them with a synthetic rhinovirus mimic. Then we measured the gene and protein levels of the mediators of our interest including those three mediators and also anti-viral mediators.
Our results showed that different micro-environments which macrophages grew in had a significant effect on them for the production of those important three mediators which we studied. Both human and mouse macrophages had dependency on their type of micro-environment for producing specific mediators in response to common cold virus infection. We also observed that the asthma-like micro-environment makes macrophages to produce less anti-viral mediators in response to common cold virus infection. This may partly be responsible for impaired anti-viral response which has been observed in asthmatic patients.
In conclusion, we showed that the milieu which macrophages reside in plays an important role in macrophages response to common cold virus. This may have some implications in better understanding of viral-induced asthma exacerbations.

Master´s Degree Project 60 credits in Molecular Biology, 2017
Department of Biology, Lund University
Advisors: Hamid Akbarshahi and Lena Uller
Respiratory immunopharmacology

• author: Kosinski, Joakim
• supervisor: Hamid Akbarshahi; Lena Uller
• organization: Degree Projects in Molecular Biology
• course: MOBT01 20162
• year: 2017
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 8907104
• date added to LUP: 2017-05-17 12:18:17
• date last changed: 2017-05-17 12:18:17