Influence of an Allergen-Specific Th17 Response on Remodeling of the Airways.

We showed previously that sensitization of mice with dendritic cells (DCs) via the airways depends on activation of these cells with LPS. Allergen-pulsed DCs that were stimulated with low doses of LPS induce a strong Th2 response in vivo. Our objective was to investigate whether airway sensitization of mice by the application of DCs with a phenotype that is able to induce Th17 cells results in increased remodeling of the airways. We generated DCs from the bone marrow of mice and pulsed them with LPS-free ovalbumin. Subsequently, cells were activated with LPS with or without ATP for inflammasome activation. The activated cells were used to sensitize mice via the airways. Intranasal instillation of DCs that were activated with 0.1 ng/ml LPS induced a Th2 response with airway eosinophilia. High doses of LPS, particularly when given in combination with ATP, led to induction of a mixed Th2/Th17 response. Interestingly, we found a correlation between IL-17A production and the remodeling of the airways. Stimulation of mouse fibroblasts with purified IL-17A protein in vitro resulted in transforming growth factor-ß1 secretion and collagen transcription. Interestingly, we found enhanced secretion of transforming growth factor-ß1 by fibroblasts after costimulation with IL-17A and the profibrotic factor wingless-type MMTV integration site family, member 5A (Wnt5a). We showed that an allergen-specific Th17 response in the airway is accompanied by increased airway remodeling. Furthermore, we revealed that increased remodeling is not only based on neutrophilic inflammation, but also on the direct impact of IL-17A on airway structural cells.

Endothelin receptor-antagonists suppress lipopolysaccharide-induced cytokine release from alveolar macrophages of non-smokers, smokers and COPD subjects.

Smoking-induced COPD is characterized by chronic airway inflammation, which becomes enhanced by bacterial infections resulting in accelerated disease progression called exacerbation. Alveolar macrophages (AM) release endothelin-1 (ET-1), IL-6, CCL-2 and MMP-9, all of which are linked to COPD pathogenesis and exacerbation. ET-1 signals via ETA- and ETB-receptors (ETAR, ETBR). This is blocked by endothelin receptor antagonists (ERAs), like bosentan, which targets both receptors, ETAR-selective ambrisentan and ETBR-specific BQ788. Therefore, ERAs could have anti-inflammatory potential, which might be useful in COPD and other inflammatory lung diseases. We hypothesized that ERAs suppress cytokine release from AM of smokers and COPD subjects induced by lipopolysaccharide (LPS), the most important immunogen of gram-negative bacteria. AM were isolated from the broncho-alveolar lavage (BAL) of n=29 subjects (11 non-smokers, 10 current smokers without COPD, 8 smokers with COPD), cultivated and stimulated with LPS in the presence or absence of ERAs. Cytokines were measured by ELISA. Endothelin receptor expression was investigated by RT-PCR and western blot. AM expressed ETAR and ETBR mRNA, but only ETBR protein was detected. LPS and ET-1 both induced IL-6, CCL-2 and MMP-9. LPS-induced IL-6 release was increased in COPD versus non-smokers and smokers. Bosentan, ambrisentan and BQ788 all partially reduced all cytokines without differences between cohorts. Specific ETBR inhibition was most effective. LPS induced ET-1, which was exclusively blocked by BQ788. In conclusion, LPS induces ET-1 release in AM, which in turn leads to CCL-2, IL-6 and MMP-9 expression rendering AM sensitive for ERAs. ERAs could have anti-inflammatory potential in smoking-induced COPD.