Background: beta2-Adrenergic agonists play a pivotal role in the management of bronchial asthma. Although the major effect of short-acting beta2-agonists on the airway is relaxation of smooth muscles, they may also have several effects on surrounding immunomodulatory cells.
Methods: We examined whether widely used short-acting beta2-agonists differ in their ability to modulate granulocyte functions, such as superoxide anion (O2-) production and degranulation.
Results: Procaterol (PC), a full agonist, significantly inhibited both O2- production by granulocytes (neutrophils and eosinophils) and their degranulation at the clinically relevant concentrations, whereas salbutamol and tulobuterol (partial agonists) showed smaller effects. PC inhibited N-formyl methionyl-leucyl-phenylalanine-induced O2- production and peroxidase release, but failed to inhibit responses induced by phorbol 12-myristate 13-acetate and/or opsonized zymosan. Exposure to 5 x 10(-8)M PC for 120 min resulted in approximately 50% inhibition of O2- production and degranulation of neutrophils. The effects of beta2-agonists were more obvious in neutrophils than in eosinophils. A selective beta2-receptor antagonist, ICI-118551, reversed the inhibitory effect of beta2-agonists (PC, salbutamol, tulobuterol B) on N-formyl methionyl-leucyl-phenylalanine-induced O2- production.
Conclusions: These results suggest that beta2-agonists had an inhibitory effect on granulocyte functions, mainly mediated viareceptors and their efficacy. Our observations support that beta2-agonists with a rapid onset of action and high intrinsic efficacy (short-acting and full agonists) may be optimal for the rescue therapy against acute asthma attack and sedation of its airway inflammation in an early phase.
(c) 2006 S. Karger AG, Basel