The following is a summary of “Airway hyperresponsiveness reflects corticosteroid-sensitive mast cell involvement across asthma phenotypes,” published in the JULY 2023 issue of Allergy & Immunology by Hvidtfeldt, et al.
Across all asthma phenotypes, airway hyperresponsiveness is a defining feature of asthma. Despite modest levels of type 2 inflammation, airway hyperresponsiveness to mannitol is directly related to mast cell infiltration of the airways, suggesting that inhaled corticosteroids help lower the reaction to mannitol. For a study, researchers sought to investigate the relationship between airway hyperresponsiveness and infiltrating mast cells and the response to inhaled corticosteroid treatment in patients with asthma.
The study enrolled 50 corticosteroid-free patients with airway hyperresponsiveness to mannitol. Mucosal cryobiopsies were taken from these patients before and after a 6-week daily treatment with 1600 μg of budesonide. The patients were stratified into two groups based on their baseline fractional exhaled nitric oxide (FENO) levels, using a cutoff of 25 parts per billion.
The study found that airway hyperresponsiveness was comparable at baseline and showed similar improvement with treatment in patients with FENO-high and FENO-low asthma. The doubling dose values for airway hyperresponsiveness were 3.98 (95% CI, 2.49-6.38; P < .001) for FENO-high asthma and 3.85 (95% CI, 2.51-5.91; P < .001) for FENO-low asthma, respectively. However, the phenotypes and distribution of mast cells differed between the two groups. In patients with Feno-high asthma, airway hyperresponsiveness correlated with the density of chymase-high mast cells infiltrating the epithelial layer (ρ, −0.42; P = .04), while in patients with Feno-low asthma, it correlated with the density of mast cells in the airway smooth muscle (ρ, −0.51; P = .02). Additionally, the improvement in airway hyperresponsiveness after inhaled corticosteroid treatment was associated with a reduction in mast cell density, as well as in airway thymic stromal lymphopoietin and IL-33 levels.
The study’s findings indicated that airway hyperresponsiveness to mannitol is linked to mast cell infiltration in different areas of the airways across asthma phenotypes. Moreover, the study highlighted the effectiveness of inhaled corticosteroid treatment in reducing airway hyperresponsiveness in both Feno-high and Feno-low asthma patients.