Improved clearability of cystic fibrosis sputum with dextran treatment in vitro

Polysaccharide-based formulations as potential carriers for pulmonary delivery - A review of their properties and fates

Polysaccharides can be elite carriers for therapeutic molecules due to their versatility and low probability to trigger toxicity and immunogenic responses. Local and systemic therapies can be achieved through particle pulmonary delivery, a promising non-invasive alternative. Successful pulmonary delivery requires particles with appropriate flowability to reach alveoli and avoid premature clearance mechanisms. Polysaccharides can form micro-, nano-in-micro-, and large porous particles, aerogels, and hydrogels. Herein, the characteristics of polysaccharides used in drug formulations for pulmonary delivery are reviewed, providing insights into structure-function relationships. Charged polysaccharides can confer mucoadhesion, whereas the ability for specific sugar recognition may confer targeting capacity for alveolar macrophages. The method of particle preparation must be chosen considering the properties of the components and the delivery device to be utilized. The fate of polysaccharide-based carriers is dependent on enzyme-triggered hydrolytic and/or oxidative mechanisms, allowing their complete degradation and elimination through urine or reutilization of released monosaccharides.

Polysulfated Hyaluronan GlycoMira-1111 Inhibits Elastase and Improves Rheology in Cystic Fibrosis Sputum

Cystic fibrosis (CF) lung disease is marked by high concentrations of neutrophil elastase (NE) and DNA polymers; both factors contribute to airway disease. Although inhaled recombinant human dornase alfa reduces the frequency of CF pulmonary exacerbations, it also increases free NE activity in the sputum. There are no approved anti-NE therapies for patients with CF. We investigated whether synthetic, low-molecular weight polysulfated hyaluronan GlycoMira-1111 (GM-1111) would be effective as an anti-NE drug using ex vivo CF sputum. Anti-NE activity of GM-1111 was tested in CF sputum in the presence or absence of dornase alfa and/or hypertonic saline using a spectrophotometric assay specific for human NE and was compared with unfractionated heparin. We tested whether GM-1111 disaggregated DNA from CF sputum (using gel electrophoresis analysis) or modified CF sputum viscoelastic properties (using a dynamic rheometer). GM-1111 and unfractionated heparin had near equivalent anti-NE activity in CF sputum in the presence of dornase alfa. Both GM-1111 and unfractionated heparin retained anti-NE activity in hypertonic saline but with decreased activity. GM-1111 increased the release of soluble DNA in CF sputum, resulting in improved depolymerization efficacy of dornase alfa. GM-1111 decreased CF sputum elasticity. GM-1111 inhibited NE activity, enhanced DNA depolymerization by deoxyribonuclease, and decreased viscoelastic properties of CF sputum, similar to effects reported previously for unfractionated heparin. Unlike heparins, GM-1111 is synthetic, with minimal anticoagulant activity, and is not derived from animal products. These key attributes provide advantages over unfractionated heparin as a potential therapeutic for CF.

The Stabilizing Excipients in Dry State Therapeutic Phage Formulations

Phage therapy has gained prominence due to the increasing pathogenicity of "super bugs" and the rise of their multidrug resistance to conventional antibiotics. Dry state formulation of therapeutic phage is attractive to improve their "druggability" by increasing their shelf life, improving their ease of handling, and ultimately retaining their long-term potency. The use and selection of excipients are critical to stabilize phage in solid formulations and protect their viability from stresses encountered during the solidification process and long-term storage prior to use. Here, this review focuses on the current classes of excipients used to manufacture dry state phage formulations and their ability to stabilize and protect phage throughout the process, as discussed in the literature. We provide perspective of outstanding challenges involved in the formulation of dry state phage. We suggest strategies to improve excipient identification and selection, optimize the potential excipient combinations to improve phage viability during formulation, and evaluate new methodologies that can provide greater insight into phage-excipient interactions to improve design criteria to improve formulation of dry state phage therapeutics. Addressing these challenges opens up new opportunities to re-design and re-imagine phage formulations for improved efficacy as a pharmaceutical product.

A Nanosensor Toolbox for Rapid, Label-Free Measurement of Airway Surface Liquid and Epithelial Cell Function

Ciliated lung epithelial cells and the airway surface liquid (ASL) comprise one of the body's most important protective systems. This system is finely tuned, and perturbations to ASL rheology, ASL depth, ASL pH, the transepithelial potential, and the cilia beat frequency are all associated with disease pathology. Further, these apparently distinct properties interact with each other in a complex manner. For example, changes in ASL rheology can result from altered mucin secretion, changes in ASL pH, or changes in ASL depth. Thus, one of the great challenges in trying to understand airway pathology is that the properties of the ASL/epithelial cell system need to be assessed near-simultaneously and without perturbing the sample. Here, we show that nanosensor probes mounted on a scanning ion conductance microscope make this possible for the first time, without any need for labeling. We also demonstrate that ASL from senescence-retarded human bronchial epithelial cells retains its native properties. Our results demonstrate that by using a nanosensor approach, it is possible to pursue faster, more accurate, more coherent, and more informative studies of ASL and airway epithelia in health and disease.

Nebulised N-Acetylcysteine for Unresponsive Bronchial Obstruction in Allergic Brochopulmonary Aspergillosis: A Case Series and Review of the Literature

Many chronic lung diseases are characterized by the hypersecretion of mucus. In these conditions, the administration of mucoactive agents is often indicated as adjuvant therapy. N-acetylcysteine (NAC) is a typical example of a mucolytic agent. A retrospective review of patients with pulmonary aspergillosis treated at the National Aspergillosis Centre in Manchester, United Kingdom, with NAC between November 2015 and November 2017 was carried out. Six Caucasians with Aspergillus lung disease received NAC to facilitate clearance of their viscid bronchial mucus secretions. One patient developed immediate bronchospasm on the first dose and could not be treated. Of the remainder, two (33%) derived benefit, with increased expectoration and reduced symptoms. Continued response was sustained over 6–7 months, without any apparent toxicity. In addition, a systematic review of the literature is provided to analyze the utility of NAC in the management of respiratory conditions which have unresponsive bronchial obstruction as a feature.

Improving the efficacy of inhaled drugs in cystic fibrosis: challenges and emerging drug delivery strategies

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians associated with early death. Although the faulty gene is expressed in epithelia throughout the body, lung disease is still responsible for most of the morbidity and mortality of CF patients. As a local delivery route, pulmonary administration represents an ideal way to treat respiratory infections, excessive inflammation and other manifestations typical of CF lung disease. Nonetheless, important determinants of the clinical outcomes of inhaled drugs are the concentration/permanence at the lungs as well as the ability of the drug to overcome local extracellular and cellular barriers. This review focuses on emerging delivery strategies used for local treatment of CF pulmonary disease. After a brief description of the disease and formulation rules dictated by CF lung barriers, it describes current and future trends in inhaled drugs for CF. The most promising advanced formulations are discussed, highlighting the advantages along with the major challenges for researchers working in this field.

A new method to improve the clinical evaluation of cystic fibrosis patients by mucus viscoelastic properties

In cystic fibrosis (CF) patients airways mucus shows an increased viscoelasticity due to the concentration of high molecular weight components. Such mucus thickening eventually leads to bacterial overgrowth and prevents mucus clearance. The altered rheological behavior of mucus results in chronic lung infection and inflammation, which causes most of the cases of morbidity and mortality, although the cystic fibrosis complications affect other organs as well. Here, we present a quantitative study on the correlation between cystic fibrosis mucus viscoelasticity and patients clinical status. In particular, a new diagnostic parameter based on the correlation between CF sputum viscoelastic properties and the severity of the disease, expressed in terms of FEV1 and bacterial colonization, was developed. By using principal component analysis, we show that the types of colonization and FEV1 classes are significantly correlated to the elastic modulus, and that the latter can be used for CF severity classification with a high predictive efficiency (88%). The data presented here show that the elastic modulus of airways mucus, given the high predictive efficiency, could be used as a new clinical parameter in the prognostic evaluation of cystic fibrosis.

Inhalable DNase I microparticles engineered with biologically active excipients

Highly viscous mucus poses a big challenge for the delivery of particulates carrying therapeutics to patients with cystic fibrosis. In this study, surface modifying DNase I loaded particles using different excipients to achieve better lung deposition, higher enzyme stability or better biological activity had been exploited. For the purpose, controlled release microparticles (MP) were prepared by co-spray drying DNase I with the polymer poly-lactic-co-glycolic acid (PLGA) and the biocompatible lipid surfactant 1,2-dipalmitoyl-Sn-phosphatidyl choline (DPPC) using various hydrophilic excipients. The effect of the included modifiers on the particle morphology, size, zeta potential as well as enzyme encapsulation efficiency, biological activity and release had been evaluated. Powder aerosolisation performance and particle phagocytosis by murine macrophages were also investigated. The results showed that more than 80% of enzyme activity was recovered after MP preparation and that selected surface modifiers greatly increased the enzyme encapsulation efficiency. The particle morphology was greatly modified altering in turn the powders inhalation indices where dextran, ovalbumin and chitosan hydrochloride increased considerably the respirable fraction compared to the normal hydrophilic carriers lactose and PVP. Despite of the improved aerosolisation caused by chitosan hydrochloride, yet retardation of chitosan coated particles in artificial mucus samples discouraged its application. On the other hand, dextran and polyanions enhanced DNase I effect in reducing cystic fibrosis mucus viscosity. DPPC proved good ability to reduce particles phagocytic uptake even in the presence of the selected adjuvants. The prepared MP systems were biocompatible with lung epithelial cells. To conclude, controlled release DNase I loaded PLGA-MP with high inhalation indices and enhanced mucolytic activity on CF sputum could be obtained by surface modifying the particles with PGA or dextran.

Effect of inhaled dry powder mannitol on mucus and its clearance

Insufficient hydration at the airway surface can make mucus adherent and poorly cleared. Cough, the major mechanism of mucus clearance in disease, is ineffective when mucus is adhesive. Inhaled mannitol creates an osmotic drive for water to move into the airway lumen. The consequent increased hydration of the airway surface decreases the adherence of mucus to the epithelium, facilitates the coupling of mucus and cilia thereby increasing mucus clearance. Inhaled mannitol also promotes effective coughing and stimulates mucociliary clearance. The beneficial effect of mannitol on mucus and its clearance has been demonstrated in patients with asthma, bronchiectasis and cystic fibrosis. Inhaled dry powder mannitol (Bronchitol™) is promising to be an effective treatment for the clearance of retained airway secretions.

Feasibility of spray drying bacteriophages into respirable powders to combat pulmonary bacterial infections

The use of bacterial viruses for antibacterial treatment (bacteriophage therapy) is currently being reevaluated. In this study, we analyze the potential of processing bacteriophages in a dry powder formulation, using a laboratory spray dryer. The phages were dried in the presence of lactose, trehalose or dextran 35, serving as an excipient to give the resulting powder the necessary bulk mass and offer protection to the delicate phage structure. Out of the three excipients tested, trehalose was found to be the most efficient in protecting the phages from temperature and shear stress throughout the spray drying process. A low inlet air temperature and atomizing force appeared to be the best parameter conditions for phage survival. Pseudomonas podovirus LUZ19 was remarkably stable, suffering less than 1 logarithmic unit reduction in phage titer. The phage titer of Staphyloccus phage Romulus-containing powders, a member of the Myoviridae family, showed more than 2.5 logarithmic units reduction. On the other hand, Romulus-containing powders showed more favorable characteristics for pulmonary delivery, with a high percentage of dry powder particles in the pulmonary deposition fraction (1-5 μm particle diameter). Even though the parameters were not optimized for spray drying all phages, it was demonstrated that spray drying phages with this industrial relevant and scalable set up was possible. The resulting powders had desirable size ranges for pulmonary delivery of phages with dry powder inhalers (DPIs).

Modified wound dressing with phyto-nanostructured coating to prevent staphylococcal and pseudomonal biofilm development

This paper reports a newly fabricated nanophyto-modified wound dressing with microbicidal and anti-adherence properties. Nanofluid-based magnetite doped with eugenol or limonene was used to fabricate modified wound dressings. Nanostructure coated materials were characterized by TEM, XRD, and FT-IR. For the quantitative measurement of biofilm-embedded microbial cells, a culture-based method for viable cell count was used. The optimized textile dressing samples proved to be more resistant to staphylococcal and pseudomonal colonization and biofilm formation compared to the uncoated controls. The functionalized surfaces for wound dressing seems to be a very useful tool for the prevention of wound microbial contamination on viable tissues.

Conception, preparation and properties of functional carrier particles for pulmonary drug delivery

BACKGROUND

The effectiveness of aerosol therapy is significantly reduced by the mucus layer covering the airways of the tracheobronchial tree. According to the present concept, drug particles are delivered to the lung together with the functional carrier particle that facilitates both the drug transport into the lungs and the penetration of deposited particles through the mucus. The approach of manufacturing multi-component powders with mucoactive compounds and anti-asthmatic medicines (DSCG) bound together in a single particle is additionally considered.

METHODS

Powders were produced with the spray-drying technique from aqueous precursor solutions containing pure low molecular weight dextran, pure mannitol and dextran/mannitol-N-acetyl cysteine (NAC) mixtures (4:1 and 1:1). NAC has been selected for this purpose as a compound, which is known to be mucolytic. Dextran and mannitol are potentially applicable in the field of inhalation drug delivery. They have been used as stabilizers of functional carrier particles. Powders were characterized for their yield and physicochemical properties including: morphology (SEM), moisture content and thermal properties (DSC). Aerosol performance was determined with NGI impactor after standardized aerosolization of the produced powders in a commercial DPI.

RESULTS

Particle size distributions of dextran-NAC powders were characterized by high fine particle fraction (45-62%), which assures good particle deposition in the lower airways. The thermodynamic properties of the powders based on the temperature of the glass transition T(g) (50-63 °C) suggest the required stability during storage at moderate humidity.

CONCLUSIONS

Preliminary examination of the required properties of these particles confirms their potential as functional carriers for pulmonary drug delivery.

Functionalized carboxyl nanoparticles enhance mucus dispersion and hydration

Luminal accumulation of viscous, poorly hydrated, and less transportable mucus has been associated with altered mucus rheology and reduced mucociliary clearance. These symptoms are some of the cardinal clinical manifestations found throughout major respiratory diseases as well as gastrointestinal and digestive disorders. Applications of current mucolytics may yield short-term improvements but are continuously challenged by undesirable side-effects. While nanoparticles (NPs) can interact with mucin polymers,whether functionalized NPs can rectify mucus rheology is unknown. Herein, we report that carboxyl-functionalized NPs (24 nm and 120 nm) dramatically reduced mucin gel size and accelerated mucin matrix hydration rate (diffusivity). Our results suggest that carboxyl-functionalized NPs disperse mucin gels possibly by enhancing network hydration. This report highlights the prospective usages of carboxyl-functionalized NPs as a novel mucus dispersant or mucolytic agent in adjusting mucus rheological properties and improving mucociliary transport to relieve clinical symptoms of patients suffering from relevant diseases.

Mannitol-guided delivery of Ciprofloxacin in artificial cystic fibrosis mucus model

Abnormal airway mucus presents a significant challenge for inhalational drug delivery. Recognizing the thick and tenacious airway mucus seen in the cystic fibrosis (CF) patients as a critical barrier to effective drug delivery, both into the mucus layer itself as well as across that layer to the underlying airway epithelium, we hypothesize that mannitol or NaCl can form inhalable drug carriers, improve drug penetration into the mucus, and ultimately enhance the drug's therapeutic effect. The objective of this study is to test whether mannitol and NaCl particles, as inhalable drug carriers, improve drug delivery into and enhance a drug's activity within a mucus-like material. Microparticles containing Ciprofloxacin (Cipro), an active ingredient, and either mannitol or NaCl were produced by spray-drying. Cipro encapsulated in mannitol particles (Cipro-mannitol) was significantly more effective at killing Pseudomonas aeruginosa (P. aeruginosa) grown in artificial mucus (AM) than Cipro encapsulated in either NaCl particles (Cipro-NaCl) or in hydrophobic particles consisting of dipalmitoylphosphatidylcholine (DPPC), albumin, and lactose (Cipro-DAL). The relatively high antibacterial effectiveness of Cipro-mannitol was not due to the effect of mannitol on bacteria or on Cipro. Rather, the unique performance of the mannitol-based particles in AM is attributable to its ability to increase local water content in the AM and enhance drug penetration into it. Mannitol is a promising excipient for inhalable microparticles that facilitate the drug delivery into the CF mucus.

Inhaled mannitol improves the hydration and surface properties of sputum in patients with cystic fibrosis

BACKGROUND

The airway mucus in patients with cystic fibrosis (CF) is dehydrated and adhesive and accumulates in the airways, resulting in chronic inflammation, infection, and progressive loss of lung function. Inhaled mannitol improves mucus clearance and, when administered over 2 weeks, it improves lung function in CF (Jaques et al. Chest. 2008;133(6):1388-1396). The changes in the physical properties of sputum after a 2-week treatment with mannitol were investigated in the same subjects with CF.

METHODS

Sputum was collected before and at the end of the 2-week treatment period from 28 subjects with CF who participated in the double-blind crossover study. Mannitol or placebo 420 mg bid was inhaled over 2 weeks. The solids content, surface tension, contact angle, and viscoelasticity were measured.

RESULTS

Two-week treatment with mannitol reduced the solids from 7.3% +/- 3.0% to 5.7% +/- 3.0% (P = .012), surface tension from 83.1 +/- 7.2 to 78.6 +/- 8.0 mN/m (P < .039), and contact angle from 52.4 +/- 7.7 to 47.9 +/- 7.3 degrees. There was no significant change in the viscoelastic properties of sputum (P > .1). Placebo treatment had no significant effect on the sputum properties. The change in solids content correlated with the change in both FEV(1) (r = -0.78, P = .004) and forced expiratory flow in the middle half of the FVC (r = -0.80, P = .003), and the percentage change in surface tension and contact angle correlated with the percentage change in the FEV(1) (r = -0.73, P = .012 and r = -0.63, P = .03, respectively) in these subjects.

CONCLUSION

Treatment with inhaled mannitol over 2 weeks improved the hydration and surface properties of sputum in patients with CF. This effect was sustained and correlated with airway function changes.

TRIAL REGISTRATION

clinicaltrials.gov; Identifier: NCT00455130.

The pharmacologic approach to airway clearance: mucoactive agents

The term "mucoactive agent" refers to any medication used to improve the clearance of airway secretions. It is not synonymous with the word "mucolytic" as this strictly means a drug that decreases the viscosity of secretions. In many cases, decreased viscosity will adversely affect cough transport. For this reason many of the older mucolytic agents such as acetylcysteine are not effective for the therapy of lung disease and their use is not recommended. I review here the many classes of mucoactive agents and identify a number of medications with great promise for the treatment of chronic airway disease.

Other medications for aerosol delivery

Although aerosol therapy is most commonly used to treat asthma and COPD, there are a large number of aerosol medications now used or in development for other diseases. Mucoactive agents have long been available by aerosol, but now we have truly effective drugs to improve effective airway clearance including dornase alfa, hyperosmolar saline, and aerosol surfactant. Inhaled antibiotics are available for the treatment of cystic fibrosis, bronchiectasis and other chronic airway infections. With the development of devices that can target aerosol to the deep lung, the opportunity to deliver medications systemically by the aerosol route has become a reality. Insulin, recently approved in the US as aerosol therapy, and other peptides are systemically absorbed from the distal airway and alveolus. Aerosol gene transfer therapy to correct abnormalities associated with cystic fibrosis, primary ciliary dyskinesia and other airway diseases also holds great potential.

Hypertonic saline therapy in cystic fibrosis: Evidence against the proposed mechanism involving aquaporins

Recent data indicate the clinical benefit of nebulized hypertonic saline in cystic fibrosis lung disease, with a proposed mechanism involving sustained increase in airway surface liquid volume. To account for the paradoxical observation that amiloride suppresses the beneficial effect of hypertonic saline, it has been previously concluded (Donaldson, S. H., Bennett, W. D., Zeman, K. L., Knowles, M. R., Tarran, R., and Boucher, R. C. (2006) N. Engl. J. Med. 354, 241-250) that amiloride-inhibitable aquaporin (AQP) water channels in airway epithelia modulate airway surface liquid volume. Here, we have characterized water permeability and amiloride effects in well differentiated, primary cultures of human airway epithelial cells, stably transfected Fisher rat thyroid epithelial cells expressing individual airway/lung AQPs, and perfused mouse lung. We found high transepithelial water permeability (P(f), 54 +/- 5 microm/s) in airway epithelial cells that was weakly temperature-dependent and inhibited by >90% by reduced pH in the basal membrane-facing solution. Reverse transcription-PCR and immunofluorescence suggested the involvement of AQPs 3, 4, and 5 in high airway water permeability. Experiments using several sensitive measurement methods indicated that amiloride does not inhibit water permeability in non-cystic fibrosis (non-CF) or CF airway epithelia, AQP-transfected Fisher rat thyroid cells, or intact lung. Our data provide evidence against the mechanism proposed by Donaldson et al. to account for the effects of amiloride and hypertonic saline in CF lung disease, indicating the need to identify alternate mechanisms.

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.

A novel model to study bacterial adherence to the transplanted airway: inhibition of Burkholderia cepacia adherence to human airway by dextran and xylitol

BACKGROUND

Lung infection with Burkholderia cepacia complex before lung transplantation in patients with cystic fibrosis is a major risk factor for decreased post-operative survival rates compared with those of patients colonized with the more common opportunistic pathogen Pseudomonas aeruginosa. Because adherence to mucosal surfaces is an important initial step in infection, we investigated the use of non-toxic neutral polysaccharides and a sugar alcohol to prevent adherence of B cepacia complex to allograft airway epithelium.

METHODS

We used human airway explants prepared from donor tracheobronchial tissue to test the effect of dextrans and xylitol in inhibiting the binding of Burkholderia cepacia complex. We used immunofluorescence and electron microscopy to determine the distribution of bacteria in the explants.

RESULTS

Burkholderia cepacia complex bound to the explants and was found only in the surface mucus layer. Dextran 40 kd applied before adding the bacteria decreased the number of bound organisms by 80% to 99%. Smaller molecular mass dextrans (4 and 20 kd) were ineffective. Xylitol inhibited bacterial binding by 67% to 85%. Both agents seemed to decrease the thickness of the surface mucus, suggesting that they may indirectly inhibit bacterial binding by removing adherent surface mucus.

CONCLUSIONS

Treating donor lungs with dextran 40 kd or xylitol before (and possibly after) surgery may inhibit the adherence of Burkholderia cepacia complex to airways and may prevent or decrease subsequent infection of the allografts.

Inhaled mannitol for the treatment of mucociliary dysfunction in patients with bronchiectasis: Effect on lung function, health status and sputum

OBJECTIVE

Inhaled mannitol increases mucus clearance in patients with bronchiectasis by an unclear mechanism. The effect of mannitol on lung function, health status and sputum properties was investigated.

METHODOLOGY

Nine patients with bronchiectasis inhaled 400 mg of mannitol once daily for 12 days. Health status was assessed using the St George's Respiratory Questionnaire (SGRQ). Sputum was analysed for viscosity, elasticity, spinnability, surface tension, contact angle, solids, mucociliary transportability (MCTR) on a frog palate, and cough transportability (CTR) on a simulated cough machine.

RESULTS

Lung function was unchanged with treatment (baseline FEV1 82.0 +/- 16.2%) apart from an improvement in FEF from 85.4 +/- 13% (baseline) to 90.7 +/- 14.4% (P < 0.05; 12th treatment; visit 7). The total SGRQ score (mean +/- SD) of 49.3 +/- 13.8 at baseline, decreased by 12.4 +/- 10.2 (P < 0.01; visit 7) and 10.1 +/- 9.4 units (P < 0.02) 6-10 days after treatment cessation. The baseline subscores for symptoms (72.9 +/- 11.8), activity (44.7 +/- 20.9) and impact (44.4 +/- 14.3) were reduced by 0.8 +/- 9.1 (P > 0.7), 8.4 +/- 16.0 (P > 0.1) and 19.2 +/- 13.7 (P < 0.005) units, respectively (visit 7). Mannitol reduced the baseline (mean +/- SE) surface tension from 94.5 +/- 1.4 to 84.7 +/- 2.1 mN/m (P < 0.0001), contact angle from 51.1 +/- 2.8 to 33.2 +/- 2.4 degrees (P < 0.0001), spinnability from 11.6 +/- 0.4 to 10.0 +/- 0.2 mm (P < 0.005), and solids from 5.7 +/- 0.4 to 4.3 +/- 0.7% (P < 0.02), acutely (visit 7). Viscosity, elasticity and MCTR did not change significantly, while CTR was increased from 25.8 +/- 1.0 to 34.1 +/- 2.7 mm (P < 0.003).

CONCLUSION

Mannitol significantly improved the health status over 12 days and this improvement was maintained for 6-10 days after cessation of treatment. In addition, mannitol reduced the tenacity, increased the hydration of mucus acutely and improved cough clearability in patients with bronchiectasis.

Pathophysiology and management of pulmonary infections in cystic fibrosis

This comprehensive State of the Art review summarizes the current published knowledge base regarding the pathophysiology and microbiology of pulmonary disease in cystic fibrosis (CF). The molecular basis of CF lung disease including the impact of defective cystic fibrosis transmembrane regulator (CFTR) protein function on airway physiology, mucociliary clearance, and establishment of Pseudomonas aeruginosa infection is described. An extensive review of the microbiology of CF lung disease with particular reference to infection with P. aeruginosa is provided. Other pathogens commonly associated with CF lung disease including Staphylococcal aureus, Burkholderia cepacia, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and atypical mycobacteria are also described. Clinical presentation and assessment of CF lung disease including diagnostic microbiology and other measures of pulmonary health are reviewed. Current recommendations for management of CF lung disease are provided. An extensive review of antipseudomonal therapies in the settings of treatment for early P. aeruginosa infection, maintenance for patients with chronic P. aeruginosa infection, and treatment of exacerbation in pulmonary symptoms, as well as antibiotic therapies for other CF respiratory pathogens, are included. In addition, the article discusses infection control policies, therapies to optimize airway clearance and reduce inflammation, and potential future therapies.

Effect of chondroitinase ABC on purulent sputum from cystic fibrosis and other patients

Cystic fibrosis (CF) patients develop chronic lung infections associated with airway obstruction by viscous and insoluble mucus secretions. Although mucus glycoproteins (mucins) are thought to be responsible for mucus plugs, other glycoconjugate components of airway secretions have not been systematically evaluated. The aim of the present study was to determine whether chondroitin sulfate proteoglycans (CSPG) contribute to the insolubility of CF sputum. Sputa obtained from 18 CF patients were incubated with chondroitinase ABC (ChABC) or buffer (control) for 18 h at 37 degrees C, and after centrifugation at 12,000 g, the volume of the insoluble pellet and turbidity of the supernatant were determined as measures of solubility. ChABC caused a 70-90% reduction in supernatant turbidity and a 60-70% decrease in pellet volume of the 13 purulent CF sputa, but had much less effect on the five nonpurulent CF sputa tested. Similar results were obtained with two non-CF purulent and two non-CF, nonpurulent sputa. Gel electrophoresis, Western blot, and slot blot immunoassays with antichondroitin sulfate and antimucin antibodies revealed that purulent sputa (CF and non-CF) contained more CSPG and less mucin than nonpurulent sputa. In vitro mixing experiments showed that mucin in nonpurulent sputa was reduced upon incubation with purulent sputa, presumably because of degradation or a loss of immunoreactive mucin epitopes from leukocyte and/or bacterial enzymes present in purulent sputa. Our results suggest that CSPG contribute more significantly than mucins to the insolubility of purulent tracheobronchial secretions from CF patients. Because purulent sputa from non-CF patients showed a similar pattern, our observations with CF sputa may have wider applicability.

Pharmacological approaches to discovery and development of new mucolytic agents

Airway mucus is the secretory product of the mucous cells; it is a variable mixture of water, mucous glycoproteins, low molecular weight ions, proteins, and lipids, whose physical properties are important for airway defense. The factors that contribute to the physical properties of mucus are complex, and there are a number of pharmacological strategies that can potentially serve to improve the clearability of airway mucus. Novel mucoactive approaches include strategies for mucoregulation--decreasing the abnormal volume of mucus secretion--and medications designed to improve the cough clearability of airway secretions. In vitro results suggest potential benefits from the additive effects of selected combinations of mucoactive medications. Further studies are required to confirm these findings, to perform direct assessments of mucus clearability, and to extend the observations to patients with various types of pulmonary diseases where mucoactive treatments are required.

Effects of dextran sulfate on tracheal mucociliary velocity in dogs

We have shown that low molecular weight dextran, as a potential mucolytic agent, reduced the viscoelasticity and spinnability of cystic fibrosis (CF) sputum and improved its ciliary transportability in vitro; it also reduced viscoelasticity of healthy dog mucus in in vitro testing. In anesthetized dogs, dextran administered by aerosol at 65 mg/mL increased tracheal mucus velocity, but this increase was not sustained for higher concentrations. The purpose of the present study is to evaluate whether low mol. wt. dextran sulfate, a charged oligosaccharide, exhibits similar effects to previously tested neutral dextran when administered by aerosol to anesthetized dogs in terms of mucus rheology and mucociliary clearance rate. Healthy mongrel dogs were anesthetized with pentobarbital and intubated. Aerosols of Ringer's solution or dextran sulfate (m.w. 5000) dissolved in Ringer's were generated by Pari LC STAR nebulizer, and delivered during 30-min periods of spontaneous breathing. Tracheal transepithelial potential difference (PD, using agar filled electrodes) and tracheal mucociliary velocity (TMV, by charcoal marker particle transport) were measured under bronchoscopic control, and mucus for viscoelasticity analysis by magnetic rheometry was collected by the endotracheal tube method. We performed experiments in seven dogs, involving 30-min administrations of aerosol, separated by 30-min periods of no aerosol. All dogs received inhalations of 6.5 mg/mL, 20 mg/mL, and 65 mg/mL dextran sulfate. Tracheal mucus viscoelasticity (average log G* over 1-100 rad/s) decreased progressively with increasing dose of dextran sulfate; for the highest concentration (65 mg/mL), log G* decreased by a factor of 2.61 (p = 0.021). A modest increase in the TMV was observed for the first dose of dextran sulfate (128% of baseline at 6.5 mg/mL, p = 0.066); thereafter TMV was stable. PD increased significantly at each concentration of dextran sulfate compared with Ringer control; however, there was no additional change between the three groups. The solids content of collected airway fluid (%SC) was gradually increased during successive 30-min dextran sulfate aerosols, indicating a significant residence time for the dextran in the mucus, and correlating with the decrease in viscoelasticity. These results suggest that dextran sulfate may be potentially of therapeutic value as a mucolytic agent, assisting mucus clearance by cough and physiotherapy, although whether it stimulates mucociliary clearance remains to be proven.

Lung delivery of aerosolized dextran

The ability of nebulizers to deliver dextran (nominal molecular mass, 4,000 g/mol) to the lung as an inhaled aerosol is evaluated by in vitro experimental methods and mathematical models. Dextran in isotonic saline was aerosolized by four nebulizer types (Pari LC STAR, Hudson T-Updraft II, Acorn II, and Sonix 2000) at dextran concentrations </= 400 mg/ml and with 2.5- and 4-ml volume fills. Aerosols inhaled during breath simulation were characterized by in-line phase Doppler anemometry, filter collection, osmometry, and gravimetry. Mathematical models were used to estimate amounts of the characterized aerosols depositing in the different regions of lung models, and mathematical models of mucous thickness were then developed to estimate initial concentrations of the depositing dextran in the mucus of each conducting airway generation. Models of three subjects (4 yr old, 8 yr old, and adult) were used. The high viscosity of the dextran solutions tested (up to seven times that of water) negatively impacts nebulization, and results in poor performance with most delivery systems tested. Our results suggest that airway mucosal dextran concentrations associated with efficacy in previous animal and in vitro models are achievable with reasonable delivery times (</= 12 min) with only one of the delivery systems/formulations tested: the Pari LC STAR nebulizer, using a 2. 5-ml volume fill and a dextran concentration of 200 mg/ml.

Update on clinical trials in the treatment of pulmonary disease in patients with cystic fibrosis

Cystic fibrosis is a congenital disease resulting from an abnormality of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. A defect in ion transport leads to poor clearance of viscoelastic secretions and a susceptibility to bacterial infection. This initiates a self-perpetuating cycle of infection and inflammation that accounts for the chronic endobronchial sepsis and pulmonary damage observed in patients with cystic fibrosis. Recent studies have attempted to correct the gene defect, enhance the expression and function of the CFTR protein and correct the ion transport defect. Improving the rheological properties of airway secretions, enhancing host defence and controlling inflammation are the other key strategies.