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Transcriptional changes in alveolar macrophages from adults with asthma after intrabronchial allergen challenge.

ABSTRACT: In recent years, alveolar macrophages (AM) have been shown to play an important role in environmental allergen-induced airway inflammation in asthma. In this study, we investigated the effect of house dust mite (HDM) and lipopolysaccharide (LPS) challenge on the transcriptome of AM from patients with mild asthma. We have shown previously that intrabronchial HDM/LPS challenge induces a mixed eosinophilic and neutrophil airways inflammation in asthma patients(5). Therefore, we hypothesize that exposure of AM to HDM/LPS would upregulate genes associated with eosinophil and neutrophil signaling. AM were harvested from the bronchoalveolar fluid of 8 asthma patients who were challenged with either saline in one lung segment or HDM/LPS in the contralateral lung segment. We performed RNA sequencing and found over 1000 significantly different expressed genes following HDM/LPS challenge. To the best of our knowledge, this is the first investigation to examine gene expression profiles in AM from asthma patients challenged with HDM and LPS in vivo. Using a well-controlled study design allowing paired analysis of saline and HDM/LPS effects in the same patient, we identified different transcriptional profiles in AM as consequence of local exposure to HDM and LPS. These findings may provide a better understanding of AM functions in (exacerbations of) allergic asthma.

ORGANISM(S): Homo sapiens

PROVIDER: GSE144576 | GEO | 2021/03/16

REPOSITORIES: GEO

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Project description:Segmental instillation of lipopolysaccharide (LPS) by bronchoscopy can be used as a model to safely induce transient airway inflammation in the human lung. The LPS challenge model enables investigation of cellular mechanisms involved in pulmonary inflammatory processes as well as pharmacodynamic analysis of investigational drugs for the treatment of respiratory diseases. Aim of this work was to describe the transcriptomic profile of the human segmental LPS challenge model with contextualization to major respiratory diseases. Pre-challenge bronchoalveolar lavage fluid (BAL) and biopsies were sampled from twenty-eight smoking, healthy subjects, followed by segmental LPS challenge and saline control challenge. Twenty-four hours post instillation, BAL and biopsies were collected from the challenged lung segments. Total RNA of cells from BAL and biopsy samples were sequenced for subsequent data analysis. Differential gene expression analysis resulted in 6316 upregulated differentially expressed genes (DEGs) and 241 downregulated DEG in BAL, but only one downregulated DEG in biopsy samples after LPS challenge compared to saline challenge. Upregulated DEG in BAL were related to molecular functions such as “Inflammatory response” or “antimicrobial humoral immune response mediated by antimicrobial peptide”, enriched biological processes such as “chemokine receptor activity”, and upregulated pro-inflammatory pathways such as “Wnt signaling pathway”, “Ras signaling pathway” or “JAK-STAT signaling pathway”. Furthermore, the segmental LPS challenge model resembled aspects of the five most prevalent respiratory diseases chronic obstructive pulmonary disease (COPD), asthma, pneumonia, tuberculosis and lung cancer and featured similarities with acute exacerbations in COPD (AECOPD) and community-acquired pneumonia (CAP). Overall, our study provides extensive information about the transcriptomic profile from BAL cells and mucosal biopsies following LPS challenge in healthy smokers. It expands the knowledge about the LPS challenge model providing potential overlap with respiratory diseases in general and infection-triggered respiratory insults such as AECOPD in particular.