Background/Objectives: Pulmonary hypertension is a progressive disease leading to right heart failure. One treatment strategy is to induce vasodilation via the nitric oxide–soluble guanylate cyclase–cyclic guanosine monophosphate (NO–sGC–cGMP) signaling pathway. There are currently two soluble guanylate cyclase stimulators on the market: Riociguat and vericiguat, with vericiguat having a longer half-life and needing to be taken only once a day. This study investigated whether the pharmacological differences between the drugs affect pulmonary vessels and airways. Methods: The effects of vericiguat and riociguat on pulmonary arteries, veins, and airways were studied using rat precision-cut lung slices (PCLS). Vessels were pretreated with endothelin-1 and airways with serotonin. In isolated perfused lungs (IPL), the effects of sGC stimulation on pulmonary artery pressure (PAP), airway resistance, inflammatory cytokine, and chemokine release were quantified. Results: Riociguat and vericiguat caused pulmonary artery dilation in PCLS. During IPL, riociguat was more effective than vericiguat in reducing PAP with a statistically significant reduction of 10%. Both drugs were potent bronchodilators in preconstricted airways (p < 0.001). Only vericiguat reduced airway resistance during IPL, as shown here for the first time. Both drugs significantly reduced IL-6 and IL-1ß levels, while riociguat also reduced VEGF-A and KC-GRO levels. Conclusions: Riociguat and vericiguat had three main effects in the two rat ex-vivo models: They dilated the pulmonary arteries, induced bronchodilation, and reduced inflammation. These properties could make sGC stimulators useful for treating diseases associated with endothelial dysfunction. In the future, vericiguat may provide an alternative treatment to induce bronchodilation in respiratory diseases.

Background: Allergic asthma is defined by bronchial hyperresponsiveness (BHR) and chronic airway inflammation. Existing treatments often fail to achieve full disease control, demanding novel therapeutic approaches. Previous in vitro studies have indicated that amitriptyline (AMI), known as tricyclic antidepressant, may influence immune cells and airway smooth muscle cells. Aim: To evaluate the effects of inhaled AMI on lung function, airway inflammation, and T-cell mediated immune modulation across different in vivo mouse models of allergic asthma. Methods: Mice were treated with inhaled amitriptyline in a prophylactic ovalbumin (OVA) asthma model (start of AMI on d1) and a therapeutic house dust mite (HDM) model (start of AMI on d7). Primary endpoints included lung function, bronchoalveolar lavage fluid (BALF) cell counts, and Th2 cytokine profiling. Additionally, we performed in vitro human Th2 lymphocytes assays. Precision-cut lung slices (PCLS) of rats were passively sensitized with serum of OVA-treated rats and airway reactivity was measured after allergen stimulation. Results: In the prophylactic OVA model, inhaled AMI significantly attenuated BHR and reduced eosinophilic cell infiltration in BALF compared to controls. In the therapeutic HDM model, AMI improved lung function parameters without altering inflammatory cell counts or Th2 cytokine levels. In differentiated human Th2 lymphocytes, AMI did not suppress cytokine expression. However, PCLS experiments demonstrated an inhibition of bronchoconstriction after passive sensitization. Conclusion: These findings indicate that inhaled amitriptyline seems to be a new and highly effective anti-obstructive therapy in allergic asthma, mainly through direct effects on airway smooth muscle rather than systemic immune modulation.

Background: 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. Methods: 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. Results: 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. Conclusions: 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.