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Abstract Background Prostaglandin D2 (PGD2) signaling via prostaglandin D2 receptor 2 (DP2) contributes to atopic and non-atopic asthma. Inhibiting DP2 has shown therapeutic benefit in certain subsets of asthma patients, improving eosinophilic airway inflammation. PGD2 metabolites prolong the inflammatory response in asthmatic patients via DP2 signaling. The role of PGD2 metabolites on eosinophil and ILC2 activity is not fully understood. Methods Eosinophils and ILC2s were isolated from peripheral blood of atopic asthmatic patients. Eosinophil shape change, ILC2 migration and IL-5/IL-13 cytokine secretion were measured after stimulation with seven PGD2 metabolites in presence or absence of the selective DP2 antagonist fevipiprant. Results Selected metabolites induced eosinophil shape change with similar nanomolar potencies except for 9α,11β-PGF2. Maximal values in forward scatter of eosinophils were comparable between metabolites. ILC2s migrated dose-dependently in the presence of selected metabolites except for 9α,11β-PGF2 with EC50 values ranging from 17.4 to 91.7 nM. Compared to PGD2, the absolute cell migration was enhanced in the presence of Δ12-PGD2, 15-deoxy-Δ12,14-PGD2, PGJ2, Δ12-PGJ2 and 15-deoxy-Δ12,14-PGJ2. ILC2 cytokine production was dose dependent as well but with an average sixfold reduced potency compared to cell migration (IL-5 range 108.1 to 526.9 nM, IL-13 range: 125.2 to 788.3 nM). Compared to PGD2, the absolute cytokine secretion was reduced in the presence of most metabolites. Fevipiprant dose-dependently inhibited eosinophil shape change, ILC2 migration and ILC2 cytokine secretion with (sub)-nanomolar potencies. Conclusion Prostaglandin D2 metabolites initiate ILC2 migration and IL-5 and IL-13 cytokine secretion in a DP2 dependent manner. Our data indicate that metabolites may be important for in vivo eosinophil activation and ILC2 migration and to a lesser extent for ILC2 cytokine secretion.

Abstract Asthma is characterised by chronic airway inflammation, airway obstruction and hyper-responsiveness. The inflammatory cascade in asthma comprises a complex interplay of genetic factors, the airway epithelium, and dysregulation of the immune response. Prostaglandin D2 (PGD2) is a lipid mediator, predominantly released from mast cells, but also by other immune cells such as TH2 cells and dendritic cells, which plays a significant role in the pathophysiology of asthma. PGD2 mainly exerts its biological functions via two G-protein-coupled receptors, the PGD2 receptor 1 (DP1) and 2 (DP2). The DP2 receptor is mainly expressed by the key cells involved in type 2 immune responses, including TH2 cells, type 2 innate lymphoid cells and eosinophils. The DP2 receptor pathway is a novel and important therapeutic target for asthma, because increased PGD2 production induces significant inflammatory cell chemotaxis and degranulation via its interaction with the DP2 receptor. This interaction has serious consequences in the pulmonary milieu, including the release of pro-inflammatory cytokines and harmful cationic proteases, leading to tissue remodelling, mucus production, structural damage, and compromised lung function. This review will discuss the importance of the DP2 receptor pathway and the current understanding of its role in asthma.

This article contains data on clinical endpoints (Peak Flow Expiratory Rate, fractional exhaled nitric oxide and total IgE serum levels) and plasma pharmacokinetic parameters concerning the use of the oral CRTh2 antagonist QAW039 (fevipiprant) in mild to moderate asthma patients. Information on experimental design and methods on how this data was obtained is also described. Further interpretation and discussion of this data can be found in the article “The oral CRTh2 antagonist QAW039 (fevipiprant): a phase II study in uncontrolled allergic asthma” (Erpenbeck et al., in press) [1].

QUESTION: Inflammatory cell numbers are important endpoints in clinical studies relying on endobronchial biopsies. Assumption-based bidimensional (2D) counting methods are widely used, although theoretically design-based stereologic three-dimensional (3D) methods alone offer an unbiased quantitative tool. We assessed the method agreement between 2D and 3D counting designs in practice when applied to identical samples in parallel. MATERIALS AND METHODS: Biopsies from segmental bronchi were collected from healthy non-smokers (n = 7) and smokers (n = 7), embedded and sectioned exhaustively. Systematic uniform random samples were immunohistochemically stained for macrophages (CD68) and T-lymphocytes (CD3), respectively. In identical fields of view, cell numbers per volume unit (NV) were assessed using the physical disector (3D), and profiles per area unit (NA) were counted (2D). For CD68+ cells, profiles with and without nucleus were separately recorded. In order to enable a direct comparison of the two methods, the zero-dimensional CD68+/CD3+-ratio was calculated for each approach. Method agreement was tested by Bland-Altmann analysis. RESULTS: In both groups, mean CD68+/CD3+ ratios for NV and NA were significantly different (non-smokers: 0.39 and 0.68, p

BACKGROUND: Cytochrome P450 monooxygenases (CYP) play an important role in the defense against inhaled toxicants, and expression of CYP enzymes may differ among various lung cells and tissue compartments. METHODS: [...]

Mast cells play a key role in allergy and asthma. They reside at the host-environment interface and are among the first cells to make contact with inhaled microorganisms and particulate antigens. Pulmonary surfactant proteins A and D (SP-A and SP-D) function in lung host defense by enhancing microbe phagocytosis and mediating other immune cell functions, but little is known about their effects on mast cells. We hypothesized that SP-A and/or SP-D modulate IgE-dependent mast cell functions. Pollen starch granules (PSG) extracted from Dactylis glomerata and coated with trinitrophenol (TNP) were used as a model of an inhaled organic particulate allergen. Our data revealed that SP-D inhibited by 50% the release of [beta]-hexosaminidase by peritoneal mast cells sensitized with IgE anti-TNP and stimulated with TNP-PSG. In contrast, SP-A had no effect. Furthermore, SP-D aggregated PSG in a dose-dependent manner, and this aggregation was mediated by SP-D's carbohydrate recognition domain. A single arm SP-D mutant (RrSP-Dser 15,20) neither aggregated PSG nor inhibited degranulation, suggesting that multimefization of SP-D is required for maximal PSG aggregation and inhibition of PSG-induced mast cell degranulation. This study is the first to demonstrate that SP-D modulates IgE-mediated mast cell functions, which are important in asthma and allergic inflammation. collectins; allergen; lung; innate immunity; immunoglobulin E

Recent studies have shown that surfactant components, in particular the collectins surfactant protein (SP)-A and -D, modulate the phagocytosis of various pathogens by alveolar macrophages. This interaction might be important not only for the elimination of pathogens but also for the elimination of inhaled allergens and might explain anti-inflammatory effects of SP-A and SP-D in allergic airway inflammation. We investigated the effect of surfactant components on the phagocytosis of allergen-containing pollen starch granules (PSG) by alveolar macrophages. PSG were isolated from Dactylis glomerata or Phleum pratense, two common grass pollen allergens, and incubated with either rat or human alveolar macrophages in the presence of recombinant human SP-A, SP-A purified from patients suffering from alveolar proteinosis, a recombinant fragment of human SP-D, dodecameric recombinant rat SP-D, or the commercially available surfactant preparations Curosurf and Alveofact. Dodecameric rat recombinant SP-D enhanced binding and phagocytosis of the PSG by alveolar macrophages, whereas the recombinant fragment of human SP-D, SP-A, or the surfactant lipid preparations had no effect. In addition, recombinant rat SP-D bound to the surface of the PSG and induced aggregation. Binding, aggregation, and enhancement of phagocytosis by recombinant rat SP-D was completely blocked by EDTA and inhibited by D-maltose and to a lesser extent by D-galactose, indicating the involvement of the carbohydrate recognition domain of SP-D in these functions. The modulation of allergen phagocytosis by SP-D might play an important role in allergen clearance from the lung and thereby modulate the allergic inflammation of asthma. innate immunity; antigen processing; allergy; lung

Background: Prostaglandin D2 (PGD2) signaling via prostaglandin D2 receptor 2 (DP2) contributes to atopic and non-atopic asthma. Inhibiting DP2 has shown therapeutic benefit in certain subsets of asthma patients, improving eosinophilic airway inflammation. PGD2 metabolites prolong the inflammatory response in asthmatic patients via DP2 signaling. The role of PGD2 metabolites on eosinophil and ILC2 activity is not fully understood.Methods: Eosinophils and ILC2s were isolated from peripheral blood of atopic asthmatic patients. Eosinophil shape change, ILC2 migration and IL-5/IL-13 cytokine secretion were measured after stimulation with seven PGD2 metabolites in presence or absence of the selective DP2 antagonist fevipiprant.Results: Selected metabolites induced eosinophil shape change with similar nanomolar potencies except for 9α,11β-PGF2. Maximal values in forward scatter of eosinophils were comparable between metabolites. ILC2s migrated dose-dependently in the presence of selected metabolites except for 9α,11β-PGF2 with EC50 values ranging from 17.4 to 91.7 nM. Compared to PGD2, the absolute cell migration was enhanced in the presence of Δ12-PGD2, 15-deoxy-Δ12,14-PGD2, PGJ2, Δ12-PGJ2 and 15-deoxy-Δ12,14-PGJ2. ILC2 cytokine production was dose dependent as well but with an average sixfold reduced potency compared to cell migration (IL-5 range 108.1 to 526.9 nM, IL-13 range: 125.2 to 788.3 nM). Compared to PGD2, the absolute cytokine secretion was reduced in the presence of most metabolites. Fevipiprant dose-dependently inhibited eosinophil shape change, ILC2 migration and ILC2 cytokine secretion with (sub)-nanomolar potencies.Conclusion: Prostaglandin D2 metabolites initiate ILC2 migration and IL-5 and IL-13 cytokine secretion in a DP2 dependent manner. Our data indicate that metabolites may be important for in vivo eosinophil activation and ILC2 migration and to a lesser extent for ILC2 cytokine secretion. [ABSTRACT FROM AUTHOR]