Rationale: Chronic obstructive pulmonary disease (COPD) is one of the leading causes of deaths worldwide. Patients with COPD have episodes of aggravated symptoms called exacerbations caused by pathogens or pollution. Respiratory viruses are associated with a significant number of COPD exacerbations with the most common virus being the rhinovirus (RV). The mechanisms by which RVs trigger COPD exacerbations are still unclear. Using human whole lung tissue explants (WTE), a novel model of RV-induced COPD exacerbations is proposed. Methods: WTE from COPD patients and smokers were initially stimulated with TLR ligands that are known to activate the same receptors as RV: poly(I:C) for TLR3 and R848 for TLR7/8 activation. Pro-inflammatory cytokines and type I and III IFN gene expression was measured by ELISA and qRT-PCR, respectively. A neutralising antibody against TNFα, a corticosteroid, and a panel of inhibitors targeting TLR pathway (p38 MAPK, IKK-2 and IRAK1/4) was applied to the tissue from COPD patients to establish which signalling pathways are responsible for the inflammatory response and IFN release. Explants from COPD patients and smokers was also exposed to two RV serotypes, RV-16 and RV-1B, in order to compare findings with a clinically relevant stimulant. Results: Poly(I:C) and R848 caused a significant increase of protein and gene expression of pro-inflammatory cytokines (TNFα, CCL5 and IL-6). Type I and III IFN gene expression was also significantly increased. Using the two ligands together caused a synergistic release of TNFα and CCL5. Tissue from COPD patients released more pro-inflammatory cytokines and expressed less IFNβ when compared to smokers. TNFα neutralisation inhibited subsequent release of CCL5 and IL-6. Dexamethasone and p38 MAPK inhibitor decreased TLR3- and TLR7/8-induced pro-inflammatory response whereas IKK-2 and IRAK1/4 inhibition had little effect on cytokine release. Dexamethasone and IKK-2 showed limited effect on IFN gene expression whereas p38 MAPK inhibitor significantly decreased and IRAK1/4 inhibition enhanced IFN expression. RV-16 induced modest but significant pro-inflammatory response in lung tissue, whereas RV-1B did not induce cytokine release. Both serotypes induced type I and III IFN gene expression. Tissue from COPD patients showed a lower expression of IFNβ and IFNλ when compared to smokers. Conclusion: This tissue explant was responsive to both synthetic TLR ligands and RV. The release of pro-inflammatory cytokines in response to TLR stimulation was partially inhibited by steroid. p38 MAPK is involved in TLR-induced inflammation but it also further decreases the already impaired IFN gene expression in COPD tissue. The role of IKK-2 and IRAK1/4 in TLR-induced innate immune response remains unclear. This model is a valuable system to study the mechanisms underlying RV-induced COPD exacerbations and also to test new inhibitors in the whole tissue environment.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:697743 |
| Date | January 2015 |
| Creators | Pomerenke, Anna Ewa |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/investigating-the-immune-responses-of-copd-lung-tissue-explants-to-viral-stimuli(d356174a-5f50-4786-8815-e11abb4a64ff).html |
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