Osmotic stimuli increase clearance of mucus in patients with mucociliary dysfunction

Dysfunction in the Cystic Fibrosis Transmembrane Regulator in Chronic Obstructive Pulmonary Disease as a Potential Target for Personalised Medicine

In recent years, numerous pathways were explored in the pathogenesis of COPD in the quest for new potential therapeutic targets for more personalised medical care. In this context, the study of the cystic fibrosis transmembrane conductance regulator (CFTR) began to gain importance, especially since the advent of the new CFTR modulators which had the potential to correct this protein's dysfunction in COPD. The CFTR is an ion transporter that regulates the hydration and viscosity of mucous secretions in the airway. Therefore, its abnormal function favours the accumulation of thicker and more viscous secretions, reduces the periciliary layer and mucociliary clearance, and produces inflammation in the airway, as a consequence of a bronchial infection by both bacteria and viruses. Identifying CFTR dysfunction in the context of COPD pathogenesis is key to fully understanding its role in the complex pathophysiology of COPD and the potential of the different therapeutic approaches proposed to overcome this dysfunction. In particular, the potential of the rehydration of mucus and the role of antioxidants and phosphodiesterase inhibitors should be discussed. Additionally, the modulatory drugs which enhance or restore decreased levels of the protein CFTR were recently described. In particular, two CFTR potentiators, ivacaftor and icenticaftor, were explored in COPD. The present review updated the pathophysiology of the complex role of CFTR in COPD and the therapeutic options which could be explored.

The efficacy of inhaled hypertonic saline for bronchiectasis: a meta-analysis of randomized controlled studies

INTRODUCTION

The efficacy of inhaled hypertonic saline for bronchiectasis remains controversial. We conduct a systematic review and meta-analysis to explore the influence of inhaled hypertonic saline versus 0.9% isotonic saline for the treatment of bronchiectasis.

METHODS

We have searched PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through April 2020 for randomized controlled trials (RCTs) assessing the efficacy of inhaled hypertonic saline versus 0.9% isotonic saline for the treatment of bronchiectasis. This meta-analysis was performed using the random-effect model.

RESULTS

Four RCTs were included in the meta-analysis. Overall, compared with control group for bronchiectasis, inhaled hypertonic saline had no obvious influence on forced expiratory volume in 1 s (FEV1, SMD = 0.12; 95% CI = -0.06 to 0.30; P = .18), forced vital capacity (FVC, SMD = 0.10; 95% CI = -0.09 to 0.28; P = .30), sputum expectorated (SMD = -0.03; 95% CI = -2.73 to 2.68; P = .99) or Leicester Cough Questionnaire (LCQ) score (SMD = -0.15; 95% CI = -0.89 to 0.58; P = .68).

CONCLUSIONS

Inhaled hypertonic saline and 0.9% isotonic saline show similar efficacy for bronchiectasis.

A Comparison between Two Pathophysiologically Different yet Microbiologically Similar Lung Diseases: Cystic Fibrosis and Chronic Obstructive Pulmonary Disease

Cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) are chronic pulmonary diseases that affect ~70,000 and 251 million individuals worldwide, respectively. Although these two diseases have distinctly different pathophysiologies, both cause chronic respiratory insufficiency that erodes quality of life and causes significant morbidity and eventually death. In both CF and COPD, the respiratory microbiome plays a major contributing role in disease progression and morbidity. Pulmonary pathogens can differ dramatically during various stages of each disease and frequently cause acute worsening of lung function due to disease exacerbation. Despite some similarities, outcome and timing/type of exacerbation can also be quite different between CF and COPD. Given these clinical distinctions, both patients and physicians should be aware of emerging therapeutic options currently being offered or in development for the treatment of lung infections in individuals with CF and COPD. Although interventions are available that prolong life and mitigate morbidity, neither disorder is curable. Both acute and chronic pulmonary infections contribute to an inexorable downward course and may trigger exacerbations, culminating in loss of lung function or respiratory failure. Knowledge of the pulmonary pathogens causing these infections, their clinical presentation, consequences, and management are, therefore, critical. In this review, we compare and contrast CF and COPD, including underlying causes, general outcomes, features of the lung microbiome, and potential treatment strategies.

An update on pediatric bronchiectasis

INTRODUCTION

The prevalence and awareness of bronchiectasis not related to cystic fibrosis (CF) is increasing and it is now recognized as a major cause of respiratory morbidity, mortality and healthcare utilization worldwide. The need to elucidate the early origins of bronchiectasis is increasingly appreciated and has been identified as an important research priority. Current treatments for pediatric bronchiectasis are limited to antimicrobials, airway clearance techniques and vaccination. Several new drugs targeting airway inflammation are currently in development. Areas covered: Current management of pediatric bronchiectasis, including discussion on therapeutics, non-pharmacological interventions and preventative and surveillance strategies are covered in this review. We describe selected adult and pediatric data on bronchiectasis treatments and briefly discuss emerging therapeutics in the field. Expert commentary: Despite the burden of disease, the number of studies evaluating potential treatments for bronchiectasis in children is extremely low and substantially disproportionate to that for CF. Research into the interactions between early life respiratory tract infections and the developing immune system in children is likely to reveal risk factors for bronchiectasis development and inform future preventative and therapeutic strategies. Tailoring interventions to childhood bronchiectasis is imperative to halt the disease in its origins and improve adult outcomes.

A randomised controlled trial on the effect of inhaled hypertonic saline on quality of life in primary ciliary dyskinesia

Hypertonic saline inhalation lowers airway mucous viscosity. Increased cough transportability may improve quality of life (QoL) in primary ciliary dyskinesia (PCD).In this randomised controlled trial (RCT), PCD patients received twice-daily inhalations of hypertonic (7%) saline or isotonic (0.9%) saline for 12 weeks, with 4 weeks washout during crossover. Primary outcome was change in QoL measured by the St George's Respiratory Questionnaire (SGRQ) total score. Secondary outcomes were SGRQ subscores, Quality of Life Questionnaire-Bronchiectasis (QoL-B) scores, lower respiratory tract infection symptoms, exacerbations, spirometry, systemic and sputum inflammatory markers, adherence, and adverse events.There was no significant change in median (interquartile range) SGRQ total score between hypertonic saline (-2.6 (-9.0-1.5)) and isotonic saline (-0.3 (-8.1-6.1)) in 22 patients (age range 22-73 years) (p=0.38). QoL-B Health Perception scale improved with hypertonic saline (p=0.03). Adverse events occurred more frequently with hypertonic saline, but were mild.12 weeks of inhaled hypertonic saline did not improve SGRQ total score in adult PCD patients in this RCT, but the sample size was small. On the secondary and more disease-specific end-point of the QoL-B, a significant improvement was observed in the Health Perception scale. This study found little evidence to support the hypothesis that hypertonic saline improves QoL in PCD patients. We advise the use of disease-specific outcome measures in future trials.

Airway Epithelial Cell Cilia and Obstructive Lung Disease

Airway epithelium is the first line of defense against exposure of the airway and lung to various inflammatory stimuli. Ciliary beating of airway epithelial cells constitutes an important part of the mucociliary transport apparatus. To be effective in transporting secretions out of the lung, the mucociliary transport apparatus must exhibit a cohesive beating of all ciliated epithelial cells that line the upper and lower respiratory tract. Cilia function can be modulated by exposures to endogenous and exogenous factors and by the viscosity of the mucus lining the epithelium. Cilia function is impaired in lung diseases such as COPD and asthma, and pharmacologic agents can modulate cilia function and mucus viscosity. Cilia beating is reduced in COPD, however, more research is needed to determine the structural-functional regulation of ciliary beating via all signaling pathways and how this might relate to the initiation or progression of obstructive lung diseases. Additionally, genotypes and how these can influence phenotypes and epithelial cell cilia function and structure should be taken into consideration in future investigations.

Marked increases in mucociliary clearance produced by synergistic secretory agonists or inhibition of the epithelial sodium channel

Mucociliary clearance (MCC) is a critical host innate defense mechanism in airways, and it is impaired in cystic fibrosis (CF) and other obstructive lung diseases. Epithelial fluid secretion and absorption modify MCC velocity (MCCV). We tested the hypotheses that inhibiting fluid absorption accelerates MCCV, whereas inhibiting fluid secretion decelerates it. In airways, ENaC is mainly responsible for fluid absorption, while anion channels, including CFTR and Ca²⁺-activated chloride channels mediate anion/fluid secretion. MCCV was increased by the cAMP-elevating agonists, forskolin or isoproterenol (10 μM) and by the Ca²⁺-elevating agonist, carbachol (0.3 μM). The CFTR-selective inhibitor, CFTR_inh-172, modestly reduced MCCV-increases induced by forskolin or isoproterenol but not increases induced by carbachol. The ENaC inhibitor benzamil increased basal MCCV as well as MCCV increases produced by forskolin or carbachol. MCC velocity was most dramatically accelerated by the synergistic combination of forskolin and carbachol, which produced near-maximal clearance rates regardless of prior treatment with CFTR or ENaC inhibitors. In CF airways, where CFTR-mediated secretion (and possibly synergistic MCC) is lost, ENaC inhibition via exogenous agents may provide therapeutic benefit, as has long been proposed.

Using Cystic Fibrosis Therapies for Non-Cystic Fibrosis Bronchiectasis

Non-cystic fibrosis bronchiectasis (NCFB) is an increasingly prevalent disease that places a significant burden on patients and health systems globally. Although many of the therapies used to treat NCFB were originally developed as cystic fibrosis (CF) therapies, not all of them have been demonstrated to be efficacious in NCFB and some may even be harmful. This article explores the evidence for which therapeutic strategies used to treat CF have been translated into the care of NCFB. The conclusion is that therapies for adult NCFB cannot be simply extrapolated from CF clinical trials, and in some instances, doing so may actually result in harm.

Hyper-osmolarity and calcium chelation: Effects on cystic fibrosis mucus

A non-functional Cystic Fibrosis Transmembrane conductance Regulator (CFTR) leads to the disease cystic fibrosis (CF). Although the CFTR is expressed in multiple organs, pulmonary disease is the major cause of illness and death in patients with CF. Stagnant mucus, causing airway obstruction, bacterial overgrowth, persistent inflammation and tissue destruction characterizes the disease, but how the defect in CFTR function is coupled to the mucus phenotype is still controversial. We have recently shown that bicarbonate ions passing through CFTR are necessary for proper unfolding of the MUC2 mucin, thus highlighting the importance of bicarbonate ion transport via the CFTR and the ability of these ions to raise the pH and chelate calcium bound to the mucin as the important steps in forming normal mucus. In order to find potential CF treatments and expand our knowledge about the usefulness of bicarbonate as an active ingredient in formulations to alleviate mucus plugging, we used an Ussing-type chamber and explants from the F508del-CFTR mutant mouse ileum to test the effect of calcium chelators on mucus attachment, either in isolation or in combination with osmolytes such as mannitol or hypertonic saline. We found that increasing the concentration of bicarbonate, both alone or in combination with increased osmolarity of the solution, detached the otherwise attached CF mucus.

Effect of apical hyperosmotic sodium challenge and amiloride on sodium transport in human bronchial epithelial cells from cystic fibrosis donors

Hypertonic saline (HS) inhalation therapy benefits cystic fibrosis (CF) patients [Donaldson SH, Bennet WD, Zeman KL, Knowles MR, Tarran R, Boucher RC. N Engl J Med 354: 241-250, 2006; Elkins MR, Robinson M, Rose BR, Harbour C, Moriarty CP, Marks GB, Belousova EG, Xuan W, Bye PT; the National Hypertonic Saline in Cystic Fibrosis (NHSCF) Study Group. N Engl J Med 354: 229-240, 2006]. Surprisingly, these benefits are long-lasting and are diminished by the epithelial Na(+) channel blocker amiloride (Donaldson SH, Bennet WD, Zeman KL, Knowles MR, Tarran R, Boucher RC. N Engl J Med 354: 241-250, 2006). Our aim was to explain these effects. Human bronchial epithelial (hBE) cells from CF lungs were grown in inserts and were used in three experimental approaches: 1) Ussing chambers to measure amiloride-sensitive short-circuit currents (INa); 2) continuous perfusion Ussing chambers; and 3) near "thin-film" conditions in which the airway surface of the inserts was exposed to a small volume (30 μl) of isosmotic or HS solution as the inserts were kept in their incubation tray and were subsequently used to measure INa under isosmotic conditions (near thin-film experiments; Tarran R, Boucher RC. Methods Mol Med 70: 479-492, 2002). HS solutions (660 mosmol/kgH2O) were prepared by adding additional NaCl to the isosmotic buffer. The transepithelial short-circuit current (ISC), conductance (GT), and capacitance (CT) were measured by transepithelial impedance analysis (Danahay H, Atherton HC, Jackson AD, Kreindler JL, Poll CT, Bridges RJ. Am J Physiol Lung Cell Mol Physiol 290: L558-L569, 2006; Singh AK, Singh S, Devor DC, Frizzell RA, van Driessche W, Bridges RJ. Methods Mol Med 70: 129-142, 2002). Exposure to apical HS inhibited INa, GT, and CT. The INa inhibition required 60 min of reexposure to the isosmotic solution to recover 75%. The time of exposure to HS required to inhibit INa was <2.5 min. Under near thin-film conditions, apical exposure to HS inhibited INa, but as osmotically driven water moved to the apical surface, the aqueous apical volume increased, leading to an amiloride-insensitive decrease in its osmolality and to recovery of INa that lagged behind the osmotic recovery. Amiloride significantly accelerated the recovery of INa following exposure to HS. Our conclusions are that exposure to HS inhibits hBE INa and that amiloride diminishes this effect.

The long term effect of inhaled hypertonic saline 6% in non-cystic fibrosis bronchiectasis

BACKGROUND AND AIMS

Inhalation of hypertonic saline (HTS) has short term positive effects on airways clearance in non-cystic fibrosis (CF) bronchiectasis, however its long term effects are unknown. The aim of this study was to determine the effect of HTS 6% on exacerbations, quality of life (QOL) and respiratory function over 12 months in non-CF bronchiectasis.

METHODS

Forty patients were randomised to inhale isotonic saline (IS) 0.9% or HTS 6% daily for 12 months. Participants recorded their symptoms in a daily diary. Quality of life and respiratory function were measured after three, six and 12 months. Number of exacerbations and changes in sputum colonisation were recorded at 12 months. Participants, assessors and clinicians were blinded to group allocation.

RESULTS

The exacerbation rate at 12 months was similar in the two groups and similar clinically significant improvements in QOL were seen in both groups. The FEV(1) increased in both groups after six months (mean 90 ml, 95% confidence interval 11-169 ml) with no difference between groups (p = 0.394). The FEF(25-75%) significantly improved at all time points (mean increase at 12 months 187 ml, 69-304 ml) with no difference between groups (p = 0.705). There was a reduction in sputum colonisation in both groups (p = 0.046).

CONCLUSIONS

Inhalation of HTS or IS has similar effects on exacerbations, QOL, sputum colonisation and respiratory function over 12 months in non-CF bronchiectasis. The trial was registered with both Clinical Trials.gov - NCT00484263 and Australian New Zealand Clinical Trials Registry - ACTRN12607000367448.

The direct effect of hyperosmolar agents on ciliary beating of human bronchial epithelial cells

BACKGROUND

Inhalation of hypertonic saline and mannitol improve mucociliary clearance in patients with bronchiectasis, but little is known about how the relative osmotic strengths of these compounds affect ciliary beat frequency (CBF) of ciliated human bronchial epithelial cells (HBEC). Our aim was to compare in vitro the direct effects of osmotically equivalent solutions on CBF of HBEC.

METHODS

HBEC were acutely (10, 30 min) exposed to comparable osmolar solutions of saline (0.03-0.48%), mannitol (0.19-3%) and dextran (10%-39.39%). Effects of higher % solutions, reversibility of responses, and prolonged treatments (15-20 h) were also compared. CBF was measured using digital videomicroscopy at baseline and at all time points.

RESULTS

CBF of HBEC increased significantly after acute exposure to mannitol (0.19%, 0.38%), decreased with dextran and remained unchanged with saline. Prolonged exposure to mannitol at high (3%, 6%) osmolar concentrations reversibly suppressed CBF. In comparison, acute and prolonged treatment with 39.39% dextran (equivalent to 3% mannitol) reduced CBF irreversibly. Furthermore, acute and prolonged treatment with 1% saline (equivalent to 6% mannitol) suppressed CBF with only the acute effect being reversible.

CONCLUSIONS

Mannitol had a direct osmolarity-independent cilio-stimulatory effect at lower % solutions and a reversible cilio-inhibitory effect at higher % solutions, and prolonged exposure to mannitol inhibited CBF reversibly. Both the acute and prolonged effects of mannitol compared to dextran and saline on CBF of HBEC in vitro, imply a unique mechanism of action for mannitol on ciliary beating and might contribute to the improved clearance observed in mannitol-treated patients.

Hypertonic saline solutions do not influence the solubility of sputum from secretor and non-secretor cystic fibrosis patients

INTRODUCTION

Functional alterations of the cystic fibrosis transmembrane conductance regulator gene (CFTR) increase the viscoelasticity of pulmonary secretions of cystic fibrosis (CF) patients and require the use of therapeutic aerosols. The biochemical properties of exocrine secretions are influenced by the expression of the FUT2 gene which determine the secretor and non-secretor phenotypes of the ABH glycoconjugates. The aim of this study was to determine the influence of secretor and non-secretor phenotypes by means of photoacoustic analysis, both the typical interaction time (t(0)) and the solubilization interval (Δt) of the sputum of secretor and non-secretor CF patients nebulized by hypertonic saline solutions at different concentrations.

MATERIAL AND METHODS

Sputum samples were obtained by spontaneous expectoration from 6 secretor and 4 non-secretor patients with CF. Each sample was nebulized with 3%, 6%, and 7% hypertonic saline solutions in a photoacoustic cell. The values of t(0) and Δt were determined using the Origin 7.5(®) computer program (Microcal Software Inc.). The t-test was employed using the GraphPad Instat 3.0(®) computer program to calculate the mean and standard deviation for each parameter.

RESULTS

For all hypertonic saline solutions tested, the mean values of t(0) and Δt do not show statistically significant differences between secretor and non-secretor patients.

CONCLUSIONS

The secretor and non-secretor phenotypes do not influence the in vitro solubilization of the sputum nebulized by hypertonic saline solutions at different concentrations when analysed by photoacoustic technique.

Managing cystic fibrosis: strategies that increase life expectancy and improve quality of life

The survival of patients with cystic fibrosis (CF) continues to improve. The discovery and cloning of the CFTR gene more than 21 years ago led to the identification of the structure and function of the CFTR chloride channel. New therapies based on the understanding of the function of CFTR are currently under development. The better clinical status and improved survival of patients with CF is not only a result of understanding of the molecular mechanisms of CF but also a result of the development of therapeutic strategies that are based on insights into the natural course of the disease. Current CF treatments that target respiratory infections, inflammation, mucociliary clearance, and nutritional status are associated with improved pulmonary function and reduced exacerbations. Patients benefit from treatment at a specialized CF center by a multidisciplinary dedicated team with emphasis being placed on frequent visits, periodic testing, and monitoring adherence to therapy. The purpose of this review is to survey recent developments in CF care that are responsible for the improved survival and quality of life of patients with CF.

Safety and tolerability of inhaled hypertonic saline in young children with cystic fibrosis

BACKGROUND

Inhaled hypertonic saline (HS) improves lung function and decreases pulmonary exacerbations in older patients with cystic fibrosis (CF). Initiating therapies in young patients has potential to preserve lung function. Before conducting a therapeutic trial of HS in this population, its safety must be evaluated and protocols for monitoring response must be tested.

METHODS

We administered single dose 3% and 7% HS post-albuterol to 4-7 year-olds with CF able to perform spirometry ("preschool" group) and 4 month to 3 year-olds ("infant" group) using the raised volume rapid thoracoabdominal compression technique (RVRTC). Vital signs and cough episodes were measured after each inhaled treatment.

RESULTS

Eight preschool subjects (mean age 5.7 +/- 0.8 years) and 6 infants (1.6 +/- 1.0 years) completed the 3% HS protocol, and no clinically important change in vital signs or decrease in FVC, FEV(1), FEV(0.5), or FEF(25-75) occurred post-HS. Preschoolers had more cough episodes post-HS (P = 0.01). Seven preschoolers (6.1 +/- 0.7 years) and 8 infants (1.6 +/- 0.7 years) completed the 7% HS protocol. In the preschool group, FVC, FEV(0.5), and FEF(25-75) did not change significantly. A statistically significant drop in median FEV(1) occurred post-7% HS attributable to a transient >20% drop in one subject. Infant PFT parameters were unchanged post-7% HS. Preschoolers had more cough episodes post-HS (P = 0.03).

CONCLUSION

Acute administration of 3% and 7% HS appears to be safe and well-tolerated in most young children with CF. Given the demonstrated benefits in older patients, a therapeutic trial in this age group is warranted.

Bronchial provocation testing with dry powder mannitol in children with cystic fibrosis

BACKGROUND/AIM

There has been recent interest in dry powder inhaled mannitol as a therapeutic agent in patients with cystic fibrosis (CF). It is has been shown to increase mucociliary clearance (MCC) by rehydrating the airway. To date there have been no studies exclusively in children with CF examining the effect of dry powder mannitol on the airways. The aim of this study was to determine acute tolerability of inhaled mannitol in children with CF.

METHODS

Thirty-nine children (aged 8-18 years) with CF underwent a bronchial provocation challenge with incrementally increasing doses of dry powder mannitol (up to a maximum cumulative dose of 475 mg). A positive challenge was defined as a drop in FEV(1) of >or=15% from baseline.

RESULTS

Nine out of 38 subjects (24%; 95% confidence interval 10-38%) had a positive challenge. Only two of these nine subjects had a PD(15) (dose of mannitol required to cause a 15% reduction in FEV(1)) prior to the 315 mg dose, the remaining seven children dropping their FEV(1) by >or=15% on the 315 or 475 mg (final) cumulative dose. We found no association between patient characteristics and a positive challenge. Although cough was common during the challenge, other adverse events were infrequent.

CONCLUSIONS

We report that 24% of children with CF had a positive airway challenge with inhaled mannitol. This compares with a previously reported 12% of subjects in a study including both adults and children. We could not identify factors predictive of a positive mannitol challenge in our children.

Effects of hyperosmotic stress on cultured airway epithelial cells

Inhalation of hyperosmotic solutions (salt, mannitol) has been used in the treatment of patients with cystic fibrosis or asthma, but the mechanism behind the effect of hyperosmotic solutions is unclear. The relation between osmolarity and permeability changes was examined in an airway cell line by the addition of NaCl, NaBr, LiCl, mannitol, or xylitol (295-700 mOsm). Transepithelial resistance was measured as an indicator of the tightness of the cultures. Cell-cell contacts and morphology were investigated by immunofluorescence and by transmission electron microscopy, with lanthanum nitrate added to the luminal side of the epithelium to investigate tight junction permeability. The electrolyte solutions caused a significant decrease in transepithelial resistance from 450 mOsm upwards, when the hyperosmolar exposure was gradually increased from 295 to 700 mOsm; whereas the nonelectrolyte solutions caused a decrease in transepithelial resistance from 700 mOsm upwards. Old cultures reacted in a more rigid way compared to young cultures. Immuno-fluorescence pictures showed weaker staining for the proteins ZO-1, claudin-4, and plakoglobin in treated samples compared to the control. The ultrastructure revealed an increased number of open tight junctions as well as a disturbed morphology with increasing osmolarity, and electrolyte solutions opened a larger proportion of tight junctions than nonelectrolyte solutions. This study shows that hyperosmotic solutions cause the opening of tight junctions, which may increase the permeability of the paracellular pathway and result in increased transepithelial water transport.

Vocal fold epithelial response to luminal osmotic perturbation

PURPOSE

Dry-air challenges increase the osmolarity of fluid lining the luminal surface of the proximal airway. The homeostasis of surface fluid is thought to be essential for voice production and laryngeal defense. Therefore, the authors hypothesized that viable vocal fold epithelium would generate a water flux to reduce an osmotic challenge (150 mOsm mannitol) on the lumen. Bidirectional transepithelial water fluxes were measured in vocal folds exposed to physiologically realistic luminal osmotic perturbations in vitro.

METHOD

Thirty-six native ovine vocal folds were exposed to either luminal hyperosmotic or isosmotic perturbations. Vocal fold viability and water fluxes toward the lumen and into the mucosa were measured at prechallenge baseline and for 30 min after challenge.

RESULTS

Vocal fold electrophysiological viability was maintained for the duration of osmotic perturbation. Luminal osmotic exposure increased luminally directed transepithelial water fluxes in 60% of vocal folds. This increase was electrically silent, of short duration, and would not negate the osmotic gradient.

CONCLUSION

Ovine vocal fold epithelia detect osmotic perturbations to the luminal surface in vitro. This ability to detect and respond to changes in surface composition may be important in homeostatic regulation of vocal fold surface fluid during osmotic perturbations in respiration and phonation.

Pilot study of safety and tolerability of inhaled hypertonic saline in infants with cystic fibrosis

Inhaled hypertonic saline (HS) positively affects both lung function and pulmonary exacerbations in children and adults with cystic fibrosis (CF). Early initiation of treatment may potentially reduce lung function decline and improve outcome of CF patients. However, the safety and tolerability of HS have not been established in infants and young children. We conducted a prospective trial of inhaled HS in infants with CF. Raised volume rapid thoracoabdominal compression (RVRTC) maneuvers were performed at baseline, 10 min after salbutamol inhalation and 15 min after inhalation of a 7% HS solution. Oxygen saturation, respiratory rate, heart rate, and cough frequency were recorded during each inhalation. A clinically important change in lung function was defined a priori as a change in FEV 0.5 of > or =20%. Thirteen infants (5 female) aged 25-140 weeks were enrolled in the study. Overall, there was no difference between FEV(0.5) or FEF(25-75) at baseline, after bronchodilator or after HS. Respiratory and heart rate as well as oxygen saturation remained stable during inhalation of the HS. Three infants had cough during inhalation; one of the infants woke up due to cough but recovered within 5 min. No other side effects were observed during or immediately after inhalation. There was no difference in microbiologic yield between pre- and post-HS throat swabs. In this pilot study, inhalation of HS was well tolerated in CF infants. These results support a study of the efficacy of HS in this age group.

The i.v. infusion of mannitol decreases airway responsiveness to methacholine in asthma

Bronchial asthma and chronic obstructive pulmonary disease (COPD) are characterized by airway inflammation and oedema. The oedema of the airway wall may contribute to airway narrowing and hyperresponsiveness by increasing airway wall thickness, by altering airway compliance, or by impairing the transmission of the lung elastic recoil to the airway smooth muscle (ASM). We hypothesized that the i.v. infusion of mannitol, an osmotic diuretic, would reduce the water content of the airway wall in asthma and COPD, thus decreasing airway responsiveness to methacholine (MCh). In eight asthmatic and in six COPD patients, airway responsiveness to MCh, lung volumes and lung mechanics were measured before and after infusion of mannitol. In the asthmatics, mannitol decreased airway responsiveness to MCh and lung elastic recoil. In the COPD patients, no differences were recorded after mannitol infusion. These data suggest that the airway wall oedema, in asthma, has an impact on airway responsiveness to MCh. The differential effect of mannitol in asthma versus COPD, may relate to the specific pathologic features of the diseases.

Differential in vivo effects of whole cigarette smoke exposure versus cigarette smoke extract on mouse ciliated tracheal epithelium

In this study the authors compared the affect of vapor phase cigarette smoke (CS) versus cigarette smoke extract (CSE) on the lungs and upper airway of C57BL/6 mice. The authors found that CSE treatment significantly increased neutrophil influx (P < .001), baseline ciliary beat frequency (CBF) (P < .05), and protein kinase C activity compared to CS and controls. Isoproterenol increased CBF with CS exposure, but decreased CBF with CSE (P < .01). Isoproterenol increased protein kinase A (PKA) activity in all groups except CSE. CSE exposure induced inflammatory cell bronchiolitis. These data indicate that CSE exposure has differential effects on the lungs and tracheal epithelium compared to CS exposure.

A modified technique for the impregnation of lanthanum tracer to study the integrity of tight junctions on cells grown on a permeable substrate

Ionic lanthanum is commonly used to trace permeability pathways across epithelia and endothelia in biological electron microscopy. A method for obtaining a uniformly dense precipitate of lanthanum is described. The method, which is a modification of the technique described by Shaklai and Tavassoli (1977) was suitable for fixation of cell cultures grown on permeable filter inserts and was successfully applied to study opening of tight junctions by hypertonic solutions in the airway epithelial cell line 16HBE14o(-). The preparation method formed the basis for a semiquantitative morphological determination in which the tight junctions were subdivided as "intact," "weakened," and "open." By using this modified technique, it could be demonstrated that opening of tight junctions in airway epithelial cells increased, with increasing osmolarity with electrolytes having a stronger effect than nonelectrolytes. A significant linear relationship was found between the osmolarity of the medium and the open state of the tight junctions (as determined by the semiquantitative morphological technique) or the transepithelial electrical resistance.

Hyperosmolar agents and clearance of mucus in the diseased airway

Clearance of mucus is an important function of the airways to maintain hygiene. In disease, persistent inflammation leads to excessive production of mucus, with high viscoelasticity and adhesivity, which is not easily transported by cilia or cough interactions. Accumulated mucus in the airways can lead to airway obstruction, bacterial colonisation, and recurrent infections, resulting in poor quality of life and increased morbidity and mortality. Hyperosmolar agents have the potential to alter the physical properties of mucus and facilitate its clearance by increasing the water in the airway lumen and by reducing the entanglements of the mucin network. Clinical studies using radioaerosols, and imaging with a gamma camera, have demonstrated that hypertonic saline (HS; 3-14.4%) and mannitol (300-400 mg) increase clearance of mucus acutely in patients with mild asthma, bronchiectasis, and cystic fibrosis (CF). Further, in sputum studies, a reduction in the viscoelastic properties, surface tension and spinnability and an increase in the hydration of mucus have been measured in response to HS, mannitol, and other sugars. Inhalation of mannitol (400 mg) twice daily over 2 weeks improved the quality of life significantly in patients with bronchiectasis. Inhalation of 7% HS, four times daily, over 2 weeks improved significantly the baseline mucus clearance rate and lung function in CF patients. In addition, inhalation of 7% HS twice daily over 12 months showed similar results to the short-term studies without a change in the bacterial load in CF patients. Further studies of the long-term clinical effect of hyperosmolar agents are needed.

Influence of air flow on the performance of a dry powder inhaler using computational and experimental analyses

PURPOSE

The aims of the study are to analyze the influence of air flow on the overall performance of a dry powder inhaler (Aerolizer and to provide an initial quantification of the flow turbulence levels and particle impaction velocities that maximized the inhaler dispersion performance.

METHODS

Computational fluid dynamics (CFD) analysis of the flow field in the Aerolizer, in conjunction with experimental dispersions of mannitol powder using a multistage liquid impinger, was used to determine how the inhaler dispersion performance varied as the device flow rate was increased.

RESULTS

Both the powder dispersion and throat deposition were increased with air flow. The capsule retention was decreased with flow, whereas the device retention first increased then decreased with flow. The optimal inhaler performance was found at 65 l min(-1) showing a high fine particle fraction (FPF) of 63 wt.% with low throat deposition (9.0 wt.%) and capsule retention (4.3 wt.%). Computational fluid dynamics analysis showed that at the critical flow rate of 65 l min(-1), the volume-averaged integral scale strain rate (ISSR) was 5,400 s(-1), and the average particle impaction velocities were 12.7 and 19.0 m s(-1) at the inhaler base and grid, respectively. Correlations between the device flow rate and (a) the amount of throat deposition and (b) the capsule emptying times were also developed.

CONCLUSIONS

The use of CFD has provided further insight into the effect of air flow on the performance of the Aerolizer. The approach of using CFD coupled with powder dispersion is readily applicable to other dry powder inhalers (DPIs) to help better understand their performance optimization.

Cystic fibrosis lung disease: genetic influences, microbial interactions, and radiological assessment

Cystic fibrosis (CF) is a multiorgan disease caused by mutation of the CF transmembrane conductance regulator (CFTR) gene. Obstructive lung disease is the predominant cause of morbidity and mortality; thus, most efforts to improve outcomes are directed toward slowing or halting lung-disease progression. Current therapies, such as mucolytics, airway clearance techniques, bronchodilators, and antibiotics, aim to suppress airway inflammation and the processes that stimulate it, namely, retention and infection of mucus plaques at the airway surface. New approaches to therapy that aim to ameliorate specific CFTR mutations or mutational classes by restoring normal expression or function are being investigated. Because of its sensitivity in detecting changes associated with early airway obstruction and regional lung disease, high-resolution CT (HRCT) complements pulmonary function testing in defining disease natural history and measuring response to both conventional and experimental therapies. In this review, perspectives on the genetics and microbiology of CF provide a context for understanding the increasing importance of HRCT and other imaging techniques in assessing CF therapies.

A Pilot Study of the Effect of Inhaled Buffered Reduced Glutathione on the Clinical Status of Patients With Cystic Fibrosis

STUDY OBJECTIVES

To assess the impact of inhaled, buffered reduced glutathione (GSH) on clinical indicators of cystic fibrosis (CF) pathophysiology.

DESIGN AND PATIENTS

A randomized, double-blind, placebo-controlled pilot study was conducted over an 8-week period. Nineteen subjects, age 6 to 19 years, with CF status documented by positive sweat chloride test results (> 60 mEq/L) were recruited for the trial. After matching on age and sex, 10 patients were randomly assigned to the treatment group and 9 patients to the placebo group. Primary outcomes were FEV1, FVC, forced expiratory flow at 25 to 75% of vital capacity, and peak flow; secondary outcomes were body mass index, 6-min walk distance, and self-reported cough frequency, mucus production/viscosity/color, wellness, improvement, and stamina. INTERVENTIONS AND ANALYSIS: Treatment was buffered GSH, and placebo was sodium chloride with a hint of quinine. The total daily dose of buffered GSH was approximately 66 mg/kg of body weight, and the total daily dose of placebo was approximately 15 mg/kg of body weight (quinine, 25 to 30 microg/kg). Doses were distributed across four inhalation sessions per day and spaced 3- to 4-h apart. General linear mixed models were used to analyze the data. The final sample size was nine subjects in the treatment group and seven subjects in the placebo group.

RESULTS

Mean change for peak flow was -6.5 L/min for the placebo group and +33.7 L/min for the GSH group (p = 0.04), and self-reported average improvement on a scale from 1 to 5 (1 being much worse and 5 being much better) was 2.8 for placebo and 4.7 for GSH (p = 0.004). Of the 13 primary and secondary outcomes examined, 11 outcomes favored the treatment group over the placebo group (p = 0.002), indicating a general tendency of improvement in the GSH group. No adverse events in the treatment group were noted.

CONCLUSION

This pilot study indicates the promise of nebulized buffered GSH to ameliorate CF disease, and longer, larger, and improved studies of inhaled GSH are warranted.