Rapid nongenomic actions of inhaled corticosteroids on long-acting β(2)-agonist transport in the airway

Abstract

Corticosteroids inhibit organic cation transporters (OCTs) that play an important role in drug absorption, tissue distribution and elimination. Corticosteroid sensitivity of bronchodilator trafficking in the airway tissue, however, is poorly understood. To assess the effects of inhaled corticosteroids on airway absorption and disposal mechanisms of long-acting β(2)-agonists, human airway epithelial and smooth muscle cell uptake of tritiated formoterol and salmeterol was measured in vitro. Corticosteroids caused a rapid, concentration-dependent inhibition of uptake of the cationic formoterol by airway smooth muscle cells, but not airway epithelial cells. Uptake of the non-charged lipophilic salmeterol was corticosteroid-insensitive in both cell types. In smooth muscle cells, inhaled corticosteroids inhibited formoterol uptake with a novel potency rank order: des-ciclesonide > budesonide > beclomethasone 17-monopropionate > beclomethasone dipropionate > ciclesonide > fluticasone. The inhibitory action was rapidly reversible, and was not enhanced by prolonged corticosteroid exposure or sensitive to a transcription inhibitor. Suppression of OCT3 expression using lentivirus-mediated production of shRNA reduced corticosteroid sensitivity of formoterol uptake by smooth muscle cells. Our data support a corticosteroid insensitive absorption and a corticosteroid-sensitive disposition mechanism for cationic long-acting β(2)-agonist bronchodilators in the airway. Potency rank order and other 'classical' features of anti-inflammatory effects do not apply to inhaled corticosteroids' rapid drug transport actions.

Figure 1

Drug uptake and rapid (15 min) inhibitory effect of corticosterone (Cort; 5 μM) in human bronchial smooth muscle cells (BSMC) and airway epithelial cells (AEC). Bars represent mean ± SD (n = 6 experiments).

Figure 2

Nongenomic, inhibitory effect of corticosterone (Cort; 5 μM) on formoterol uptake by human bronchial smooth muscle cells. A, The rapid (15 min) inhibitory corticosteroid effect was not enhanced by prolonged corticosteroid pretreatment for 45 and 90 min (+pre45’ and +pre90’, respectively). B, Corticosterone effect in the presence of the transcription inhibitor actinomycin D (Act; 100 μM). C, Formoterol uptake in cells exposed to corticosterone for 15 min followed by corticosterone washout prior to transport measurements (post-Cort). Bars represent mean ± SD (n = 6 experiments).

Figure 3

The role of OCT3 in rapidly inhibiting formoterol uptake into human bronchial smooth muscle cells. A, OCT3 mRNA relative expression in cells that were infected with OCT3 targeted (-OCT3) and non-targeted shRNA-containing lentivirus. B, OCT3 mRNA suppression reduces formoterol uptake and the inhibitory effect of corticosterone (Cort). Results represent mean ± SD (n = 4 experiments).