Abstract
Background Severe asthma is associated with multiple co-morbidities, including gastro-oesophageal reflux disease (GORD) which can contribute to exacerbation frequency and poor quality of life. Since epithelial dysfunction is an important feature in asthma, we hypothesised that in severe asthma the bronchial epithelium is more susceptible to the effects of acid reflux.
Methods We developed an in vitro model of GORD using differentiated bronchial epithelial cells (BECs) from normal or severe asthmatic donors exposed to a combination of pepsin, acid pH, and bile acids using a multiple challenge protocol (MCP-PAB). We also analysed bronchial biopsies and undertook RNA-sequencing of bronchial brushings from controls and severe asthmatics without or with GORD.
Results Exposure of BECs to the MCP-PAB caused structural disruption, increased permeability, IL-33 expression, inflammatory mediator release and changes in gene expression for multiple biological processes. Cultures from severe asthmatics were significantly more affected than those from healthy donors. Analysis of bronchial biopsies confirmed increased IL-33 expression in severe asthmatics with GORD. RNA-sequencing of bronchial brushings from this group identified 15 of the top 37 dysregulated genes found in MCP-PAB treated BECs, including genes involved in oxidative stress responses.
Conclusions By affecting epithelial permeability, GORD may increase exposure of the airway submucosa to allergens and pathogens, resulting in increased risk of inflammation and exacerbations. Clinical implication: These results suggest the need for research into alternative therapeutic management of GORD in severe asthma.
Footnotes
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Conflict of interest: Prof. Perotin has nothing to disclose.
Conflict of interest: Dr. Wheway has nothing to disclose.
Conflict of interest: Dr. Tariq has nothing to disclose.
Conflict of interest: Dr. Azim has nothing to disclose.
Conflict of interest: Mr. Ridley has nothing to disclose.
Conflict of interest: Mr. Ward has nothing to disclose.
Conflict of interest: Dr. Schofield reports being Director and shareholder in TopMD Precision Medicine Ltd.
Conflict of interest: Ms. Barber has nothing to disclose.
Conflict of interest: Dr. Howarth reports personal fees from GSK, outside the submitted work.
Conflict of interest: Prof Davies has nothing to disclose.
Conflict of interest: Prof Djukanovic reports receiving fees for lectures at symposia organised by Novartis, AstraZeneca and TEVA, consultation for TEVA and Novartis as member of advisory boards, and participation in a scientific discussion about asthma organised by GlaxoSmithKline. He is a co-founder and current consultant, and has shares in Synairgen, a University of Southampton spin out company.
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- Received June 9, 2021.
- Accepted December 10, 2021.
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