Airway inflammation in cystic fibrosis

Patients with cystic fibrosis (CF) experience declining pulmonary function related to chronic airway inflammation, which results from epithelial and immune cell secretion of proinflammatory mediators that promote neutrophil influx into the airways. This inflammatory response may be disproportionate to the inciting infectious stimulus, resulting in an overly exuberant influx of neutrophils. The neutrophils release proteases, including neutrophil elastase, that eventually overwhelm the antiprotease capacity of the lung and cleave structural proteins, leading to bronchiectasis. This deleterious inflammatory process in patients with CF has become a potential therapeutic target, though the development of effective antiinflammatory therapies has been limited by the lack of sensitive outcome measures. Historically, indirect measures of lung disease, such as spirometry, have been used to assess the effect of antiinflammatory drugs. BAL remains the primary method of interrogating the inflammatory status of the airway, but the procedure is invasive and may eventually be supplanted by induced sputum. Anatomic imaging with high-resolution CT scanning is used clinically, but has unknown utility, and functional imaging, using positron emission tomography, appears promising but is still investigational. Despite the paucity of outcome measures, clinical trials of antiinflammatory agents, including corticosteroids and ibuprofen, have demonstrated benefits, though their use has been limited by adverse effects. Azithromycin is increasingly used as an immunomodulatory agent, although its mechanism of action remains unclear. Strategies for modulating the airway inflammation in patients with CF are currently under development and may offer new therapeutic options for these patients.