Inhaled Hypertonic Saline as a Therapeutic Strategy to Dampen Inflammation in Cystic Fibrosis

Cystic fibrosis (CF) is a complex genetic chloride channelopathy, manifesting clinically as a multisystem disorder. Patients with CF have significant morbidity and decreased life expectancy, primarily due to respiratory disease, which is characterised by frequent pulmonary exacerbations and decline in lung function. The pathogenesis of pulmonary disease in CF is explained in part by dehydration of airway surface liquid with reduced mucociliary clearance leading to accumulation of thick inspissated mucus in the airways. This results in airway obstruction, and provides a suitable environment for pathogens to grow and colonize, giving rise to a cycle of recurrent airway inflammation in the CF lung. Multiple therapeutic interventions in CF care are aimed at improving mucus clearance. These include improved chest physiotherapy techniques, recombinant DNase, and more recently nebulised hypertonic saline (HTS). Treatment with HTS has been shown to improve mucus clearance in CF and decrease exacerbations, with subsequent improvements in quality of life, and lung function. While the mechanisms by which HTS elicits these improvements are likely related to increase in mucociliary clearance, there is increasing evidence to suggest that HTS also exerts significant anti-inflammatory and anti-microbial effects in the CF lung. This review will describe these effects of HTS looking at the interaction between HTS and neutrophils, the major inflammatory cell in the CF lung, and the effects of HTS on the antimicrobial peptides found in the airways.