Purpose:
IL-33 is known to induce
corticosteroid-resistant eosinophilic
inflammation and
airway remodeling by activating type 2 innate lymphoid cells (ILC2s). Although the RAS signal pathway plays an important role in IL-33-induced ILC2s activation and
airway remodeling, it is not known if RAS inhibitors are effective against refractory
asthma. We examined the effects of the RAS inhibitor XRP44X in refractory
asthma. Methods: RAS activity were examined by BAL fluid and T-cells isolated from spleen cells in Dermatophagoides pteronyssinus (Dp)-sensitized/challenged acute allergic airway
inflammation model. A chronic allergic airway
inflammation mouse model was generated by challenged with Dp. XRP44X and/or
fluticasone were administrated nasally to different experimental groups. The effects of nasal simultaneous administration of XRP44X or
fluticasone were assessed in mice administrated with
IL-33 or Dp. Results: RAS activity in CD4+ T cells stimulated by Dp were suppressed by XRP44X. Although
fluticasone and XRP44X only improved allergic airway
inflammation in mice, XRP44X in combination with
fluticasone produced further improvement in not only eosinophilic
inflammation but also bronchial subepithelial thickness. XRP44X suppressed
IL-5 and
IL-13 production from ILC2s, although this effect was not suppressed by
fluticasone. IL-33-induced airway
inflammation resistant to
fluticasone was ameliorated by XRP44X via regulating the accumulation of lung ILC2s. Conclusion: The RAS signal pathway plays a crucial role in
allergen-induced
airway remodeling associated with ILC2s. XRP44X may have therapeutic potential for refractory
asthma.