Nongenomic effects of fluticasone propionate and budesonide on human airway anion secretion

This study investigated the physiological effects of inhaled corticosteroids, which are used widely to treat asthma. The application of fluticasone propionate (FP, 100 μM) induced sustained increases in the short-circuit current (I_SC) in human airway Calu-3 epithelial cells. The FP-induced I_SC was prevented by the presence of H89 (10 μM, a protein kinase A inhibitor) and SQ22536 (100 μM, an adenylate cyclase inhibitor). The FP-induced responses involved bumetanide (a Na ⁺-K⁺-2Cl^- cotransporter inhibitor)-sensitive and 4,4'-dinitrostilbene-2,2'-disulfonic acid (an inhibitor of HCO₃ 2-dependent anion transporters)-sensitive components, both of which reflect basolateral anion transport. Further, FP augmented apical membrane Cl ^- current (I_Cl), reflecting cystic fibrosis transmembrane conductance regulator (CFTR)-mediated conductance, in the nystatin-permeabilized monolayer. In I_SC and I_Cl responses, FP failed to enhance the responses to forskolin (10 μM, an adenylate cyclase activator). Nevertheless, we found that FP synergistically increased cytosolic cAMP concentrations in combination with forskolin. All these effects of FP were reproduced with the use of budesonide. Collectively, inhaled corticosteroids such as FP and budesonide stimulate CFTR-mediated anion transport through adenylate cyclase-mediated mechanisms in a nongenomic fashion, thus sharing elements of a common pathway with forskolin. However, the corticosteroids cooperate with forskolin for synergistic cAMPproduction, suggesting that the corticosteroids and forskolin do not compete with each other to exert their effects on adenylate cyclase. Considering that such synergism was also observed in the FP/salmeterol combination, these nongenomic aspects may play therapeutic roles in mucus congestive airway diseases, in addition to genomic aspects that are generally recognized.