Acute Effect of Mometasone on Beta-adrenergic Airway and Airway Vascular Relaxation in Severe Asthma

Glucocorticosteroids inhibit the disposal of organic cations by blocking organic cation transporters expressed by non-neuronal cells, thereby interfering with the inactivation of the organic cations by intracellular enzymes. Beta2-adrenergic agonists are organic cations, and the concentration of inhaled beta2-adrenergic agonists at beta2-adrenergic receptor sites on smooth muscle is likely to be increased by inhaled glucocorticosteroids (ICS) by the ICS' effect on the glucocorticosteroid-sensitive organic cation transporters. The investigators have shown in human airway vascular smooth muscle cells that the glucocorticosteroid action on organic cation uptake occurs within minutes, does not involve gene transcription or protein synthesis, is not mediated through classical steroid receptors, and is cell membrane-linked. In the present proposal, the investigators wish to use different single doses of mometasone, a clinically effective ICS, administered with or at different times before albuterol inhalation in subjects with moderate persistent asthma who are obstructed at the time of study. With this approach the investigators will test the hypothesis that a single inhalation of mometasone causes an acute, transient, dose-dependent potentiation of beta2-adrenergic bronchodilation. If the hypothesis that a single dose of mometasone acutely potentiates beta2-adrenergic bronchodilation is correct, the results would have a significant impact on treatment strategies involving ICSs and beta2-adrenergic agonists in patients with asthma.