Antibacterial activity of apical surface fluid from the human airway cell line Calu-3 - Pharmacologic alteration by corticosteroids and beta 2-agonists

Calu-3 cells, a human lung carcinoma cell line with properties like serous cells of the upper airway, were used to develop an in vitro model for airwa y antibacterial activity. Calu-3 cell monolayers were cultured on permeable supports at an air-liquid interface. Apical surface fluid (ASF) was collec ted by washing; antibacterial activity was assayed by incubating ASF washin gs with bacteria for 18 h and counting surviving colony-forming units. ASF washings killed Escherichia coli and Pseudomonas aeruginosa. Antibacterial activity was salt sensitive and dependent on protein concentration. After w ashing, approximately 30 h were required before antibacterial activity reco vered to its initial level. After culturing with topical corticosteroids (b udesonide, triamcinolone, or beclomethasone, 0.1 mug/ml for 48 h), ASF anti bacterial activity was 4- to 10-fold greater than the ASF from control mono layers. The increase in antibacterial activity was dose-dependent. The beta (2)-agonists salbutamol and terbutaline (100 mug/ml for 48 h) decreased AS F antibacterial activity by 5- to 8-fold. The nonsteroidal anti-inflammator y agents ibuprofen and cromolyn sodium had no effect. Our results are most consistent with agonist-dependent changes in the composition of ASF antibac terial proteins. We conclude that Calu-3 cells synthesize and secrete antib acterial proteins and that clinical agents can alter these functions.