Effects of sodium concentration on human neutrophil bactericidal functions

Nebulized hypertonic saline in noncystic fibrosis bronchiectasis: a comprehensive review

Bronchiectasis occurs as a result of a vicious circle consisting of an impaired mucociliary transport system, inflammation, and infection and repair of the airways. Damage to the mucociliary system prevents secretion elimination and facilitates bacterial growth and bronchial inflammation. To facilitate mucociliary clearance, current guidelines recommend the use of hypertonic saline (HS) solutions in patients with bronchiectasis not secondary to cystic fibrosis (CF), although the evidence of efficacy in this pathology is sparse. A high percentage of patients with CF and bronchiectasis tolerate HS solutions, but often patients report cough, dyspnoea, throat irritation, or salty taste after inhalation. These adverse effects negatively impact adherence to treatment, which sometimes must be discontinued. Some studies have shown that the addition of hyaluronic acid increases the tolerability of HS solutions, both in patients with CF and in bronchiectasis of other etiologies. We aimed to review the benefits and safety of HS solutions in patients with bronchiectasis. The reviews of this paper are available via the supplemental material section.

In vivo therapeutic efficacy of frog skin-derived peptides against Pseudomonas aeruginosa-induced pulmonary infection

Pseudomonas aeruginosa is an opportunistic and frequently drug-resistant pulmonary pathogen especially in cystic fibrosis sufferers. Recently, the frog skin-derived antimicrobial peptide (AMP) Esc(1-21) and its diastereomer Esc(1-21)-1c were found to possess potent in vitro antipseudomonal activity. Here, they were first shown to preserve the barrier integrity of airway epithelial cells better than the human AMP LL-37. Furthermore, Esc(1-21)-1c was more efficacious than Esc(1-21) and LL-37 in protecting host from pulmonary bacterial infection after a single intra-tracheal instillation at a very low dosage of 0.1 mg/kg. The protection was evidenced by 2-log reduction of lung bacterial burden and was accompanied by less leukocytes recruitment and attenuated inflammatory response. In addition, the diastereomer was more efficient in reducing the systemic dissemination of bacterial cells. Importantly, in contrast to what reported for other AMPs, the peptide was administered at 2 hours after bacterial challenge to better reflect the real life infectious conditions. To the best of our knowledge, this is also the first study investigating the effect of AMPs on airway-epithelia associated genes upon administration to infected lungs. Overall, our data highly support advanced preclinical studies for the development of Esc(1-21)-1c as an efficacious therapeutic alternative against pulmonary P. aeruginosa infections.

Abnormalities in the pulmonary innate immune system in cystic fibrosis

Pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the basis for this susceptibility remains incompletely understood. One hypothesis is that CF airway surface liquid (ASL) is abnormal and interferes with neutrophil function. To study this possibility, we developed an in vitro system in which we collected ASL from primary cultures of normal and CF airway epithelial cells. Microbial killing was less efficient when bacteria were incubated with neutrophils in the presence of ASL from CF epithelia compared with normal ASL. Antimicrobial functions of human neutrophils were assessed in ASL from CF and normal epithelia using a combination of quantitative bacterial culture, flow cytometry, and microfluorescence imaging. The results of these assays of neutrophil function were indistinguishable in CF and normal ASL. In contrast, the direct bactericidal activity of ASL to Escherichia coli and to clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa was substantially less in CF than in normal ASL, even when highly diluted in media of identical ionic strength. Together, these observations indicate that the antimicrobial properties of ASL in CF are compromised in a manner independent of ionic strength of the ASL, and that this effect is not mediated through a direct effect of the ASL on phagocyte function.

Sodium chloride increases the ciliary transportability of cystic fibrosis and bronchiectasis sputum on the mucus-depleted bovine trachea

Mucus retention in the lungs is an important feature of several respiratory diseases (Regnis, J.A., M. Robinson, D.L. Bailey, P. Cook, P. Hooper, H.K. Chan, I. Gonda, G. Bautovich, and P.T.P. Bye. 1994. Am. J. Respir. Crit. Care Med. 150:66-71 and Currie, D.C., D. Pavia, J.E. Agnew, M.T. Lopez-Vidriero, P.D. Diamond, P.J. Cole, and S.W. Clarke. 1987. Thorax. 42:126-130). On the mucus-depleted bovine trachea, the ciliary transport rate of sputum from patients with cystic fibrosis and bronchiectasis of other causes was slow, but the rate was doubled by increasing the sodium chloride content by 90 mM. Increasing the sputum osmolality by inspissation or by the addition of nonelectrolytes had a similar effect. The viscoelasticity of sputum, but not the bovine ciliary beat frequency, was markedly saline dependent over the pathophysiological range. This suggests that low mucus salinity, not (as is generally assumed) its under-hydration, contributes to its retention in bronchiectasis due to cystic fibrosis and other causes, probably by affecting its rheology. It also indicates how the genetic defect in cystic fibrosis might lead to impaired mucus clearance. Therapies that increase the osmolality of lung mucus might benefit patients with mucus retention.