Effects of Inhaled Amitriptyline on Airway Function and Immune Responses in Experimental Asthma

Bronchial asthma is a chronic inflammatory airway disease characterized by acute bronchoconstriction and type 2-driven inflammation. This study investigated whether inhaled amitriptyline, a functional inhibitor of acid sphingomyelinase, exerts both bronchodilatory and immunomodulatory effects in experimental murine models of allergic airway inflammation (AAI) and human cellular systems.

Acute AAI was induced in mice using ovalbumin (OVA) and house dust mite (HDM) protocols, respectively. Inhaled amitriptyline (3.3 mg/mL) was administered for either 20 days (short-term) or 36 days (long-term). Lung function was assessed using FlexiVent^®, and inflammatory markers including IgE, eosinophils, and type 2 cytokines were measured in bronchoalveolar lavage fluid and lung tissue. Complementary experiments were included using passively sensitized PCLSs and human type 2-differentiated CD4⁺ T cells.

Inhaled amitriptyline improved lung mechanics in both the OVA and HDM models, reducing total respiratory resistance and elastance. In the OVA model, eosinophil and T cell counts in BALF were decreased, whereas immunomodulatory effects were less pronounced in the short-term HDM model. In human T_H2 cells, no significant changes in cytokine production or gene expression were observed. Ex vivo, amitriptyline dose-dependently inhibited allergen-induced bronchoconstriction in PCLSs.

Inhaled amitriptyline improves lung function across murine models of AAI, supporting its potential in exhibiting model-dependent immunomodulatory effects, and directly attenuates allergen-induced bronchoconstriction, supporting its potential as a bronchodilator with context-dependent immunomodulatory properties.