In Vitro Effect of β2-Agonists on Bacterial Killing and Superoxide Anion (O2−) Release From Alveolar Macrophages of Patients With Chronic Bronchitis

Abstract

A new class of long-acting beta 2-adrenoceptor agonists has been studied in the last few years. Apparently, they display an important anti-inflammatory activity with an inhibition of different cellular functions. This study was carried out to compare a long-acting beta 2-agonist, formoterol, with a conventional short-acting one, salbutamol, on the release of superoxide anion (O2-) and bacterial killing by alveolar macrophages obtained with bronchoalveolar lavage (BAL) from 20 patients with chronic bronchitis. The O2- production in basal conditions was not affected by beta 2-agonists. On the contrary, after phagocytosis of opsonized zymosan 10(-5) M formoterol significantly affected the phagocytic index (difference between stimulated and basal O2- release): 7.9 +/- 2.0 nM O2-/10(6) AM/10 min vs 16.8 +/- 2.5, p < 0.0007. Bacterial killing was inhibited by the two drugs in a dose-dependent way, but the effect of formoterol was more evident than that of salbutamol. After blocking beta 2-receptors with propranolol, we observed a prevention of the beta 2-agonist effects on both O2- release and bacterial killing. The inhibition of the alveolar macrophage functions considered in this study is evident for both beta 2-agonists, but it is significantly more pronounced for formoterol. Our data can be interpreted as one possible mechanism of the anti-inflammatory effect described for long-acting beta 2-agonists. On the other hand, also a potential suppression of pulmonary antibacterial defenses must not be overlooked, particularly in chronic bronchitis, a disease characterized by recurrent airways infections. Whether current therapeutic dosages are sufficient to achieve anti-inflammatory or microbicidal suppressive effects of clinical relevance has not been demonstrated so far.