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

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. Overall design: House dust mite (HDM) and lipopolysaccharide (LPS) challenged alveolar macrophages (n=8); saline control alveolar macrophages (n=8)