Sputum microRNA‐screening reveals Prostaglandin EP3 receptor as selective target in allergen‐specific immunotherapy

Abstract

Background Several microRNAs (miRs) have been described as potential biomarkers in liquid biopsies and in the context of allergic asthma, while therapeutic effects on the airway expression of miRs remain elusive. In this study, we investigated epigenetic miR‐associated mechanisms in the sputum of grass pollen‐allergic patients with and without allergen‐specific immunotherapy (AIT). Methods Induced sputum samples of healthy controls (HC), AIT‐treated and ‐untreated grass pollen‐allergic rhinitis patients with (AA) and without asthma (AR) were profiled using miR microarray and whole‐transcriptome microarray analysis of the same samples. miR targets were predicted in silico and used to identify inverse regulation. Local PGE2 levels were measured using ELISA. Results Two hundred and fifty nine miRs were upregulated in the sputum of AA patients compared with HC, while only one was downregulated. The inverse picture was observed in induced sputum of AIT‐treated patients: while 21 miRs were downregulated, only 4 miRs were upregulated in asthmatics upon AIT. Of these 4 miRs, miR‐3935 stood out, as its predicted target PTGER3, the prostaglandin EP3 receptor, was downregulated in treated AA patients compared with untreated. The levels of its ligand PGE2 in the sputum supernatants of these samples were increased in allergic patients, especially asthmatics, and downregulated after AIT. Finally, local PGE2 levels correlated with ILC2 frequencies, secreted sputum IL‐13 levels, inflammatory cell load, sputum eosinophils and symptom burden. Conclusions While profiling the sputum of allergic patients for novel miR expression patterns, we uncovered an association between miR‐3935 and its predicted target gene, the prostaglandin E3 receptor, which might mediate AIT effects through suppression of the PGE2‐PTGER3 axis.

Bronchial inflammation biomarker patterns link humoral immunodeficiency with bronchiectasis‐related small airway dysfunction

“…As it was not possible to reveal all bronchiectasis‐related changes on the basis of FEV1 and FVC, the present observations are consistent with previously published data 35 . Patients with concomitant bronchiectasis but normal FEV1 and FVC, however, showed either a MEF25 below 50% or a significantly increased inflammatory cell load in the sputum (leucocyte number per mL sputum) 28,29 accompanied by high neutrophil numbers.…”

“…or a significantly increased inflammatory cell load in the sputum (leucocyte number per mL sputum) 28,29 accompanied by high neutrophil numbers.…”

“…The cell suspension was centrifuged in a Labofuge 400 cytospin column (Heraeus, Germany) at 44 × g for 6 min. The slides produced were air‐dried, fixed with methanol for 5 min and stained using the Pappenheim method 28,29 . Specimens with a content of less than 15% of squamous epithelial cells were considered adequate.…”

Chronic Allergen Challenge Induces Corticosteroid Insensitivity With Persistent Airway Remodeling and Type 2 Inflammation

“…ILC2 regulation involves negative regulatory signals from IFNγ or PGE 2 ( Duerr et al, 2016 ; Maric et al, 2018 ; Zhou et al, 2018 ; Zhou et al, 2020 ). While PGE 2 inhibits ILC2 expansion through its receptors EP2 and EP4 ( Maric et al, 2018 ; Zhou et al, 2018 ), PGE 2 may also enhance ILC2 pro-inflammatory effector functions through EP3 ( Jakwerth et al, 2021 ). Additional studies are needed to better understand why Th2 cells, and potentially other type 2 immune cells, persist in the MA but not OVA model.…”

Allergic diseases and novel targets in allergen immunotherapy

“…3 Little is known of how allergenspecific immunotherapy (AIT) affects local miRs and levels of corresponding gene transcripts of asthma patients. The study conducted by Jakwerth et al 4 identified miR-3935 as one of the most relevant out of four miRs up-regulated in asthmatics undergoing AIT, as its target PTGER3, the prostaglandin EP3 receptor, was downregulated compared to untreated asthmatics. Subsequently, sputum supernatants obtained from asthmatics contained elevated levels of its ligand PGE2 and ILC2 numbers compared to the AIT-treated group.…”