β2-agonists promote host defense against bacterial infection in primary human bronchial epithelial cells

Abstract

BackgroundAirway epithelial cells are critical in host defense against bacteria including Mycoplasma pneumoniae (Mp) in chronic obstructive pulmonary disease (COPD) and asthma. β2-agonists are mainstay of COPD and asthma therapy, but whether β2-agonists directly affect airway epithelial host defense functions is unclear.MethodsEpithelial cells from bronchial brushings of normal (n = 8), asthma (n = 8) and COPD (n = 8) subjects were grown in air-liquid interface cultures, and treated with cigarette smoke extract (CSE) and/or Th2 cytokine IL-13, followed by Mp infection and treatment with β2-agonists albuterol and formoterol for up to seven days. Mp and host defense proteins short palate, lung, and nasal epithelial clone 1 (SPLUNC1) and β-defensin-2 were quantified. Expression of β2-adrenergic receptors was also measured by real-time quantitative RT-PCR.Results(R)- or racemic albuterol and (R,R)- or racemic formoterol significantly decreased Mp levels in normal and asthma epithelial cells. Normal cells treated with Mp and (R)- or racemic albuterol showed an increase in SPLUNC1, but not in β-defensin-2. COPD cells did not respond to drug treatment with a significant decrease in Mp or an increase in SPLUNC1. IL-13 attenuated drug effects on Mp, and markedly decreased SPLUNC1 and β2-adrenergic receptors.ConclusionsThese results for the first time show that β2-agonists enhance host defense functions of primary bronchial epithelial cells from normal and asthma subjects, which is attenuated by IL-13.

Up-Regulation of MUC18 in Airway Epithelial Cells by IL-13

“…Using Mp as an infection model, NCI-H292 cells treated with IL-13 demonstrated higher Mp levels than those without IL-13 treatment (Figure 3), which is similar to the results in our previous publications in primary human bronchial epithelial cells (16,17). Therefore, the NCI-H292 cell line was used as a valuable model to study the mechanisms (e.g., Sp1) underlying IL-13-induced MUC18 expression.…”

“…Brushed bronchial epithelial cells were cultured under ALI conditions with or without IL-13 (10 ng/ml) treatments as previously reported (17,(19)(20)(21)(22) (see details in the online supplement). After 16 days of treatment, cells were harvested into TRIzol (Invitrogen, Carlsbad, CA) and Western lysis buffer for MUC18 mRNA and protein detection, respectively.…”

“…All subjects with asthma met the American Thoracic Society criteria for mild to moderate asthma (18). Bronchial brushings were performed as previously described (17,19). Up to six brushings were obtained per subject for MUC18 protein and mRNA measurements and cell culture.…”

“…The common bacteria seen in asthma and COPD airways include, but are not limited to, Mycoplasma pneumoniae (Mp), nontypeable Haemophilus influenzae (NTHi), and Moraxella catarrhalis (12,13). Our previous studies have shown that the Th2 cytokine IL-13 increased Mp load in well differentiated human airway epithelial cells under the air-liquid interface (ALI) cultures (16,17), suggesting a damaging role of IL-13 in epithelial defense against pathogenic bacteria. However, the mechanisms by which IL-13 increases bacterial load on airway epithelium remain largely unknown.…”

Bactericidal/Permeability-Increasing Protein Fold–Containing Family Member A1 in Airway Host Protection and Respiratory Disease

“…This likely reflects increased surface tension and decreased ASL water content caused by loss of surfactant and ion transport properties in BPIFA1-deficient animals (51, 57). Gross and colleagues suggested that the induction of BPIFA1 expression in airway epithelial cells by b 2 -agonist treatment should improve Mp clearance through the mechanisms described above (60). BPIFA1 may also modulate the secretion of other antimicrobial proteins in the airway because naive BPIFA1-deficient mice exhibited decreased expression of antimicrobial peptides LL37, lactoferrin, and lyzozyme.…”