Cystic fibrosis airway epithelia fail to kill bacteria because of abnormal airway surface fluid

Signal-mediated interactions between Pseudomonas aeruginosa and Candida albicans

Pseudomonas aeruginosa causes infections in a wide variety of hosts and is the leading cause of mortality in cystic fibrosis (CF) patients. Although most clinical isolates of P. aeruginosa share common virulence determinants, it is known that strains evolve and change phenotypically during CF lung infections. These changes can include alterations in the levels of N-acyl homoserine lactones (HSLs), which are secreted signal molecules. In the CF lung, fungi, especially Candida albicans and Aspergillus fumigatus, may coexist with P. aeruginosa but the implications for disease are not known. Recent studies have established that signalling can occur between P. aeruginosa and C. albicans, with the bacterial molecule 3-oxo-C12HSL affecting Candida morphology, and the fungal metabolite farnesol reducing levels of the Pseudomonas quinolone signal and pyocyanin in Pseudomonas. Whether these interactions are common and typical in clinical strains of P. aeruginosa was addressed using CF isolates that produced varied levels of HSLs. It was found that, whereas some clinical P. aeruginosa strains affected C. albicans morphology, others did not. This correlated closely with the amounts of 3-oxo-C12HSL produced by the isolates. Furthermore, it was established that signalling is bidirectional and that the C. albicans molecule farnesol inhibits swarming motility in P. aeruginosa CF strains. This work demonstrates that clinical isolates of these opportunistic pathogens can interact in strain-specific ways via secreted signals and illustrates the importance of studying these interactions to fully understand the microbial contribution to disease in polymicrobial infections.

Cystic fibrosis lung disease in adult patients

As the longevity of all patients with cystic fibrosis (CF) continues to increase (median 2005 survival=36.8 years), more adult patients will be receiving their medical care from nonpediatric adult-care providers. Cystic fibrosis remains a fatal disease, with more than 80% of patients dying after the age of 18 years, and most deaths resulting from pulmonary disease. The changing epidemiology requires adult-care providers to become knowledgeable and competent in the clinical management of adults with CF. Physicians must understand the influence of specific genotype on phenotypic disease presentation and severity, the pathogenic factors determining lung disease onset and progression, the impact of comorbid disease factors such as CF-related diabetes and malnutrition upon lung disease severity, and the currently approved or standard accepted therapies used for chronic management of CF lung disease. This knowledge is critical to help alleviate morbidity and improve mortality for the rapidly expanding population of adults with CF.

Effects of oxygen concentration and exposure time on cultured human airway epithelial cells

OBJECTIVES

To distinguish the direct effects of oxygen dose and exposure time on human airway epithelial cells. We hypothesized that progressive oxygen exposure would induce cell dysfunction and inflammation in a dose-dependent manner.

DESIGN

Interventional laboratory study.

SETTING

An academic medical research facility in the northeastern United States.

SUBJECTS

Calu-3 human airway epithelial cell culture.

INTERVENTIONS

Cells were cultured at a gas-liquid interface with the cells fed basolaterally with medium and grown to full confluence. The apical surfaces were then exposed to gas containing 21%, 40%, 60%, or 80% oxygen, 5% CO2, and balance nitrogen for 24 or 72 hrs.

MEASUREMENTS AND MAIN RESULTS

The effects of oxygen concentration and time-induced cellular change were examined by measuring transepithelial resistance of monolayers, cell viability by trypan blue exclusion, basolateral lactate concentration, histology of monolayer cross-sections, and cytospin slides, plus interleukin (IL)-6 and IL-8 secretion in apical surface fluid. Transepithelial resistance decreased in a dose- and time-dependent manner (p < .001), whereas cell viability was reduced only at 72 hrs and in all hyperoxic groups (p < .05). IL-6 secretion was elevated in all hyperoxic groups at 24 hrs (p < .001), and both IL-6 and IL-8 levels were greater in the 40% FiO2 group compared with all other groups at 72 hrs (p < .01).

CONCLUSIONS

In this model, airway epithelial cells demonstrate profound concentration and time-dependent responses to hyperoxic exposure with respect to cell physiology, viability, histology, and secretion of inflammatory mediators. This model might be a valuable tool for preliminary analysis of potentially protective therapies against hyperoxia-induced airway epithelial injury.

The role of epithelial beta-defensins and cathelicidins in host defense of the lung

The continuous exposure of the epithelial surface of the conducting airways to inhaled pathogens requires the presence of an efficient innate immune system to prevent infections. The innate immune system of the lung provides protection against a broad spectrum of microbial threats through a variety of effector mechanisms. The antimicrobial peptides and proteins form important elements of this defence system in the lung. Defensins and cathelicidins are the main families of antimicrobial peptides (AMPs) that are present in airway secretions and that are expressed by the airway epithelium. Expression and release of these small (3-5 kDa) cationic peptides is regulated by exposure of epithelial cells to a wide variety of substances, including microbial products, cytokines and growth factors. More recently, also active vitamin D(3) has been implicated as a major regulator of AMPs expression. AMPs contribute to host defence through direct antimicrobial activity, as well as by modulating innate and adaptive immunity, and wound repair. Novel insight into the mechanism of action of these peptides and the regulation of their expression may lead to innovative approaches for treatment of infectious and inflammatory lung disorders.

Pulmonary defense and the human cathelicidin hCAP-18/LL-37

Antimicrobial peptides form an important component of the innate immune system. The cathelicidin family, a key member of the antimicrobial peptide defenses, has been highly conserved throughout evolution. Though widespread in mammals, there is currently only one identified human example, hCAP-18/LL-37. The cathelicidins have been found to have multiple functions, in addition to their known antimicrobial and lipopolysaccharide-neutralizing effects. As a result, they profoundly affect both innate and adaptive immunity. Currently, antimicrobial peptides are being evaluated as therapeutic drugs in disease states as diverse as oral mucositis, cystic fibrosis, and septic shock. One such peptide, the cathelicidin hCAP-18/LL-37, is reviewed in detail in the context of its role in lung physiology and defense.

Identification of sodium chloride-regulated genes in Burkholderia cenocepacia

Previous studies have suggested that the airways of cystic fibrosis (CF) patients have elevated sodium chloride (NaCl) levels due to the malfunctioning of the CF transmembrane conductance regulator protein. For bacteria to survive in this high-salt environment, they must adjust by altering the regulation of gene expression. Among the different bacteria inhabiting the airways of CF patients is the opportunistic pathogen Burkholderia cenocepacia. Previous studies have indicated that B. cenocepacia produces a toxin and cable pili under high osmolar conditions. We used transposon mutagenesis to identify NaCl-regulated genes in the clinical strain B. cenocepacia K56-2. Six transconjugants were induced with increasing NaCl concentration. The DNA flanking the transposon was sequenced and five distinct open reading frames were identified encoding the following putative proteins: an integrase, an NAD-dependent deacetylase, TolB, an oxidoreductase, and a novel hypothetical protein. The collective results of this study provide important information about the physiology of B. cenocepacia when faced with osmotic stress and suggest the identity of significant virulence mechanisms in this opportunistic pathogen.

Airway epithelial control of Pseudomonas aeruginosa infection in cystic fibrosis

Defective expression or function of the cystic fibrosis transmembrane conductance regulator (CFTR) underlies the hypersusceptibility of cystic fibrosis (CF) patients to chronic airway infections, particularly with Pseudomonas aeruginosa. CFTR is involved in the specific recognition of P. aeruginosa, thereby contributing to effective innate immunity and proper hydration of the airway surface layer (ASL). In CF, the airway epithelium fails to initiate an appropriate innate immune response, allowing the microbe to bind to mucus plugs that are then not properly cleared because of the dehydrated ASL. Recent studies have identified numerous CFTR-dependent factors that are recruited to the epithelial plasma membrane in response to infection and that are needed for bacterial clearance, a process that is defective in CF patients hypersusceptible to infection with this organism.

Synergistic airway gland mucus secretion in response to vasoactive intestinal peptide and carbachol is lost in cystic fibrosis

Cystic fibrosis (CF) is caused by dysfunction of the CF transmembrane conductance regulator (CFTR), an anion channel whose dysfunction leads to chronic bacterial and fungal airway infections via a pathophysiological cascade that is incompletely understood. Airway glands, which produce most airway mucus, do so in response to both acetylcholine (ACh) and vasoactive intestinal peptide (VIP). CF glands fail to secrete mucus in response to VIP, but do so in response to ACh. Because vagal cholinergic pathways still elicit strong gland mucus secretion in CF subjects, it is unclear whether VIP-stimulated, CFTR-dependent gland secretion participates in innate defense. It was recently hypothesized that airway intrinsic neurons, which express abundant VIP and ACh, are normally active and stimulate low-level gland mucus secretion that is a component of innate mucosal defenses. Here we show that low levels of VIP and ACh produced significant mucus secretion in human glands via strong synergistic interactions; synergy was lost in glands of CF patients. VIP/ACh synergy also existed in pig glands, where it was CFTR dependent, mediated by both Cl(-) and HCO(3) (-), and clotrimazole sensitive. Loss of "housekeeping" gland mucus secretion in CF, in combination with demonstrated defects in surface epithelia, may play a role in the vulnerability of CF airways to bacterial infections.

The role of cathelicidin and defensins in pulmonary inflammatory diseases

Antimicrobial peptides (AMPs) protect the epithelia of mucosal organs like the respiratory or the gastrointestinal tract from invading microorganisms. As an integral part of the innate immune system they display antimicrobial activity against gram- and gram-negative bacteria as well as against fungi and enveloped and non-enveloped viruses. Besides their microbicidal effects they have important functions in the regulation of repair and inflammation. AMPs are sometimes referred to as 'alarmins' due to their ability to recruit, modulate and activate components of the immune system. In contrast, some AMPs suppress activation of the immune system. AMPs are also involved in tissue repair, cancer biology and angiogenesis. Based on their antimicrobial and immunomodulatoy functions, AMPs are probably involved in the pathogenesis of infectious and inflammatory diseases of the lung. Inborn or acquired deficiencies contribute to susceptibility to infection and colonisation. The potential pro-inflammatory role of AMPs contributes to the disease processes in inflammatory disorders such as asthma, chronic obstructive pulmonary disease, sepsis or pulmonary fibrosis. This review summarises the knowledge about the functions of AMPs in the pulmonary innate host defence system and their role in respiratory disease.

Antimicrobial peptides: natural effectors of the innate immune system

Antimicrobial peptides (AMPs) are an evolutionarily conserved component of the innate immune system that defend against invading bacteria, viruses, and fungi through membrane or metabolic disruption. The efficiency of host defense via AMPs derives from the ability of these peptides to quickly identify and eradicate foreign pathogens through precise biochemical mechanisms. Recent advances in this field have expanded the repertoire of activities for AMPs to include immunostimulatory and immunomodulatory capacity as a catalyst for secondary host defense mechanisms. Further scrutiny of the biochemical and regulatory mechanisms of AMPs will lead to novel alternative approaches to the treatment of human pathogenic disorders.

IL-4 and IL-13 negatively regulate TNF-alpha- and IFN-gamma-induced beta-defensin expression through STAT-6, suppressor of cytokine signaling (SOCS)-1, and SOCS-3

Human beta-defensins (HBDs) are a major class of antimicrobial peptides that play an important role in the innate immune response, however, the induction and regulation of these antimicrobial peptides is not well understood. We demonstrate here that stimulation of keratinocytes with TNF-alpha/IFN-gamma induces HBD-2 and HBD-3 by activating STAT-1 and NF-kappaB signaling. We further demonstrate that IL-4 and IL-13 activate STAT-6 and induce the suppressors of cytokine signaling (SOCS)-1 and -3. This interferes with STAT-1 and NF-kappaB signaling, thereby inhibiting TNF-alpha/IFN-gamma-mediated induction of HBD-2 and HBD-3. These data suggest that targeting the STAT-1-signaling pathway or suppressor of cytokine signaling expression enhances beta-defensin expression and represents a new therapeutic strategy for reduction of infection in human diseases associated with beta-defensin deficiency.

The sense of smell, its signalling pathways, and the dichotomy of cilia and microvilli in olfactory sensory cells

Smell is often regarded as an ancillary perception in primates, who seem so dominated by their sense of vision. In this paper, we will portray some aspects of the significance of olfaction to human life and speculate on what evolutionary factors contribute to keeping it alive. We then outline the functional architecture of olfactory sensory neurons and their signal transduction pathways, which are the primary detectors that render olfactory perception possible. Throughout the phylogenetic tree, olfactory neurons, at their apical tip, are either decorated with cilia or with microvilli. The significance of this dichotomy is unknown. It is generally assumed that mammalian olfactory neurons are of the ciliary type only. The existence of so-called olfactory microvillar cells in mammals, however, is well documented, but their nature remains unclear and their function orphaned. This paper discusses the possibility, that in the main olfactory epithelium of mammals ciliated and microvillar sensory cells exist concurrently. We review evidence related to this hypothesis and ask, what function olfactory microvillar cells might have and what signalling mechanisms they use.

Cystic fibrosis: a polymicrobial infectious disease

Cystic fibrosis (CF) is the most common lethal genetic disease in the Caucasian population, and should be considered an infectious disease because of the basic pathophysiology. Chronic lower airway infections cause a progressive pathologic deterioration of lung tissue, a decline in pulmonary function and, ultimately, respiratory failure and death in 90% of CF patients. Historically, very few bacterial species have been implicated as principal CF pathogens. However, molecular evidence suggests the presence of a diverse mosaic of bacteria in CF lungs, and infections can be defined as polymicrobial. Here we review the work that supports this concept and we discuss the potential significance of the polymicrobial community in lung pathology. Understanding the dynamics of polymicrobial infections, the interplay between pathogen(s), normal oropharyngeal flora and the host immune system may lead to future advances in the therapeutic management of chronic lung infections.

ETCare: a randomized, controlled, masked trial comparing two solutions for upper airway care in the NICU

BACKGROUND

Small quantities of normal saline are sometimes instilled into the endotracheal tube of intubated neonates, to assist with the removal of thick secretions and maintain patency of the endotracheal tube. However, saline is detrimental to the innate immune system of the upper airway mucosa, rapidly unfolding and inactivating antimicrobial peptides such as LL-37. We previously reported the preparation and feasibility testing of 'ETCare', a low-sodium, physiologically based solution for airway care, and we now report results of a randomized, masked, controlled, two-centered study testing ETCare vs sterile saline among 60 intubated NICU patients.

STUDY DESIGN

Sixty intubated NICU patients were randomized to having their airway care with ETCare vs saline. Three hypotheses were tested: (1) tolerance - patients will tolerate ETCare for airway care as well as they tolerate saline, (2) nosocomial infections - ETCare will result in fewer tracheal aspirates where organisms grow and fewer cases of nosocomial sepsis, and (3) chronic lung disuse - ETCare will result in fewer patients discharged home on supplemental O2.

RESULTS

Thirty NICU patients with an endotracheal tube in place were randomized to receive their airway care with ETCare, and 30 to receive their care with saline. Only the pharmacist was aware of the randomization; the two solutions were visually indistinguishable and were dispensed in identical syringes. Tolerance of the solutions was similar. The ETCare recipients had trends toward fewer positive blood cultures (odds ratios (OR), 0.48; 95% confidence interval (CI), 0.13 to 1.68), and fewer discharges home on supplemental O2 (OR, 0.43; 95% CI, 0.14 to 1.32; P=0.075).

CONCLUSIONS

On the basis of this study and our previous 10-patient feasibility trial, we maintain that, for airway care, intubated NICU patients tolerate ETCare as well as saline. Data from this study can be used in estimating the sample sizes needed for a phase III trial. We speculate that such a trial will demonstrate that, compared with saline, ETCare will result in fewer nosocomial infections and less chronic lung disease.

Resistance of the antibacterial agent ceragenin CSA-13 to inactivation by DNA or F-actin and its activity in cystic fibrosis sputum

OBJECTIVES

The goal of this study was to evaluate the effects of DNA and F-actin [polyanions present in high concentration in cystic fibrosis (CF) airway fluid] on the antibacterial activities of the cationic steroid antibiotic CSA-13 and the cationic peptides LL37, WLBU2 and HB71.

METHODS

Light scattering intensity was used to evaluate the aggregation of DNA and F-actin by the cationic antibacterial agents. Bacterial killing assays, atomic force microscopy, determination of MIC values and bacterial load of CF sputa were used to determine the bactericidal activity. Inhibition of nuclear factor-kappaB (NF-kappaB) translocation in human aorta endothelial cells (HAECs) was quantified as an assay of anti-inflammatory action.

RESULTS

CSA-13 is significantly more effective than cationic antibacterial peptides against kanamycin-resistant Pseudomonas aeruginosa and less susceptible to inactivation by DNA or F-actin. The concentration of CSA-13 sufficient to decrease the CF sputa bacteria load by approximately 90% is at least 10 times lower than that at which CSA-13 formed aggregates with DNA or F-actin. Both CSA-13 and LL37 prevent lipopolysaccharide-induced translocation of NF-kappaB in HAEC, thereby suggesting that these antibacterial molecules might prevent systemic inflammation caused by bacterial wall components.

CONCLUSIONS

Charge-based interactions that strongly inhibit the antibacterial activity of host cationic antibacterial peptides present in CF sputa have significantly less effect on molecules from the ceragenin family such as CSA-13 due in part to their smaller net charge and distribution of this charge over a hydrophobic scaffold. CSA molecules therefore have potential for the treatment of chronic infections and inflammation that occur in CF airways and other settings in which extracellular polyanions accumulate.

ENaCbeta and gamma genes as modifier genes in cystic fibrosis

BACKGROUND

Clinical phenotype varies among cystic fibrosis (CF) patients with identical CF transmembrane conductance regulator (CFTR)genotype, suggesting that genetic modifiers exist. Transgenic mice that overexpress SCNN1beta present CF-like lung disease symptoms. Mutations or variants in SCNN1beta may therefore potentially modulate the clinical phenotype in CF patients.

METHODS

We analysed by DHPLC SCNN1beta and SCNN1gamma genes in 56 patients with classical CF. Patients were classified into two groups according to their CFTR genotype and their severity: 38 patients with severe genotype and an unexpectedly mild lung phenotype, and 18 patients with mild genotype and a severe lung phenotype.

RESULTS

We found 3 patients out of 56 carrying at least one missense mutation. Two were novel (p.Thr313Met in SCNN1beta, p.Leu481Gln in SCNN1gamma) and two were previously described (p.Gly589Ser in SCNN1beta and p.Val546Ileu in SCNNgamma). p.Thr313Met has been identified in a CF patient with mild genotype and severe lung phenotype suggesting that it could act in increasing ENaC activity. The three other variants have been identified in CF patients with severe genotype and mild lung phenotype suggesting that they might decrease ENaC activity. However, the function of ENaC in the nasal epithelia of these patients, evaluated by nasal potential difference measurements, did not support the fact that these variants were functional, at least in nasal epithelium.

CONCLUSION

Our results suggest that genetic variants in ENaCbeta and gamma genes do not modulate disease severity in the majority of CF patients.

Cystic Fibrosis: The Mechanisms of Pathogenesis of an Inherited Lung Disorder

Cystic fibrosis patients exhibit lung disease consistent with a failure of innate airway defense mechanisms. The link between abnormal ion transport and disease initiation and progression is not fully understood, but airway mucus dehydration seems paramount in the initiation of CF lung disease. New therapies are currently in development that target the ion transport defects in CF with the intention of rehydrating airway surfaces.

Cystic fibrosis: a disease of vulnerability to airway surface dehydration

Cystic fibrosis (CF) lung disease involves chronic bacterial infection of retained airway secretions (mucus). Recent data suggest that CF lung disease pathogenesis reflects the vulnerability of airway surfaces to dehydration and collapse of mucus clearance. This predisposition is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, resulting in (i) the absence of CFTR-mediated Cl- secretion and regulation of epithelial Na+ channel (ENaC) function; and (ii) the sole dependence on extracellular ATP to rebalance these ion transport processes through P2 purinoceptor signaling. Recent clinical studies indicate that inhalation of hypertonic saline osmotically draws sufficient water onto CF airway surfaces to provide clinical benefit.

Inducibility of the endogenous antibiotic peptide beta-defensin 2 is impaired in patients with severe sepsis

Introduction

The potent endogenous antimicrobial peptide human β-defensin 2 (hBD2) is a crucial mediator of innate immunity. In addition to direct antimicrobial properties, different effects on immune cells have been described. In contrast to the well-documented epithelial β-defensin actions in local infections, little is known about the leukocyte-released hBD2 in systemic infectious disorders. This study investigated the basic expression levels and the ex vivo inducibility of hBD2 mRNA in peripheral whole blood cells from patients with severe sepsis in comparison to non-septic critically ill patients and healthy individuals.

Methods

This investigation was a prospective case-control study performed at a surgical intensive care unit at a university hospital. A total of 34 individuals were tested: 16 patients with severe sepsis, 9 critically ill but non-septic patients, and 9 healthy individuals. Serial blood samples were drawn from septic patients, and singular samples were obtained from critically ill non-septic patients and healthy controls. hBD2 mRNA levels in peripheral white blood cells were quantified by real-time polymerase chain reaction in native peripheral blood cells and following ex vivo endotoxin stimulation. Defensin plasma levels were quantified by enzyme-linked immunosorbent assay.

Results

Endotoxin-inducible hBD2 mRNA expression was significantly decreased in patients with severe sepsis compared to healthy controls and non-septic critically ill patients (0.02 versus 0.95 versus 0.52, p < 0.05, arbitrary units). hBD2 plasma levels in septic patients were significantly higher compared to healthy controls and critically ill non-septic patients (541 versus 339 versus 295 pg/ml, p < 0.05).

Conclusion

In contrast to healthy individuals and critically ill non-septic patients, ex vivo inducibility of hBD2 in peripheral blood cells from septic patients is reduced. Impaired hBD2 inducibility may contribute to the complex immunological dysfunction in patients with severe sepsis.

Induction of cathelicidin in normal and CF bronchial epithelial cells by 1,25-dihydroxyvitamin D(3)

BACKGROUND

Antimicrobial peptides (AMPs) such as cathelicidins contribute to initial defense of the airway against inhaled pathogens. Recent studies have shown that the hormonally active form of vitamin D(3), 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) up-regulates AMP gene expression in several established cell lines. Furthermore, serum levels of vitamin D are often deficient in cystic fibrosis (CF) patients.

METHODS

We investigated the effect of 1,25(OH)(2)D(3) on AMP mRNA levels in primary cultures of normal human bronchial epithelial (NHBE) cells by real-time PCR, and protein levels by Western blot. Antimicrobial activity of airway surface fluid from these cells was measured by in vitro assay against laboratory strains of bacteria.

RESULTS

Treatment of NHBE cells with 1,25(OH)(2)D(3) (10(-8)M), resulted in a 10-fold up-regulation of cathelicidin mRNA levels after 12 h, which was augmented 2-fold with co-incubation of 1 mM Calcium. Moreover, 1,25(OH)(2)D(3) induced antimicrobial activity against the airway pathogens Bordetella bronchiseptica and Pseudomonas aeruginosa. 1,25(OH)(2)D(3) induced cathelicidin mRNA expression equally in both normal and CF bronchial epithelial cells.

CONCLUSIONS

Elucidation of the effect of 1,25(OH)(2)D(3) on cathelicidin expression in NHBE cells and CF bronchial epithelial cells will aid in the development of novel therapeutic agents for treatment of airway infections in CF.

A potentiating effect of endogenous NO in the physiologic secretion from airway submucosal glands

It is known that several second messengers, such as Ca(2+) or cAMP, play important roles in the intracellular pathway of electrolyte secretion in tracheal submucosal gland. However, the participation of cGMP, and therefore nitric oxide (NO), is not well understood. To investigate the physiologic role of NO, we first examined whether tracheal glands can synthesize NO in response to acetylcholine (ACh), and then whether endogenous NO has some effects on the ACh-triggered ionic currents. From the experiments using the NO-specific fluorescent indicator 4,5-diaminofluorescein diacetate salt (DAF-2DA), we found that a physiologically relevant low dose of ACh (100 nM) stimulated the endogenous NO synthesis, and it was almost completely suppressed in the presence of the nonspecific NO synthase (NOS) inhibitor Nomega-Nitro-L-arginine Methyl Ester Hydrochloride (L-NAME) or the neuronal NOS (nNOS)-specific inhibitor 7-Nitroindazole (7-NI). Patch-clamp experiments revealed that both the NOS inhibitors (L-NAME or 7-NI) and cGK inhibitors (KT-5823 or Rp-8-Br-cGMP) partially decreased ionic currents induced by 30 nM of ACh, but not in the case of 300 nM of ACh. Our results indicate that NO can be synthesized through the activation of nNOS endogenously and has potentiating effects on the gland secretion, under a physiologically relevant ACh stimulation. When cells were stimulated by an inadequately potent dose of ACh, which caused an excess elevation in [Ca(2+)](i), the cells were desensitized. Therefore, due to NO, gland cells become more sensitive to calcium signaling and are able to maintain electrolyte secretion without desensitization.

Airway surface dehydration in cystic fibrosis: pathogenesis and therapy

Cystic fibrosis (CF) lung disease reflects the failure of airways defense against chronic bacterial infection. Studies of CF cultures, transgenic mice, and CF patients suggest that the initiating event in CF airways disease pathogenesis is reduced airway surface liquid (ASL) volume, i.e., dehydration. CF ASL volume regulation depends on a single extracellular signaling system, ATP, which renders CF airways more vulnerable to disease-causing insults (e.g., viruses) than are normal airways, which regulate ASL volume by dual ATP and adenosine signaling pathways. Clinical studies have explored the hypothesis that treating the dehydration of CF airways will be therapeutically beneficial. Inhaled hypertonic saline osmotically draws water onto airway surfaces, improves mucus clearance and pulmonary function, and reduces acute exacerbations in CF patients. Thus, rehydration therapies may slow the progression of CF lung disease in patients with established bacterial infection and may prevent the onset of CF lung disease if initiated early in life.

Aquaporin-8 expression is reduced in ileum and induced in colon of patients with ulcerative colitis

AIM: To study susceptibility genes which may play a potential role in the pathogenesis and etiology of inflammatory bowel disease (IBD).

METHODS: To identify potential susceptibility genes we performed global gene expression profiling in patients with IBD and control specimens. For determination of an intrinsic gene expression profile in ulcerative colitis (UC) and Crohn's disease (CD) compared to normal subjects, mucosal biopsies of non-inflamed regions of the colon and the terminal ileum were subjected to DNA microarray analysis. Real-time RT-PCR and immunohistochemistry were used for verification of selected regulated candidate genes and a genetic analysis was performed.

RESULTS: We could show that aquaporin-8 (AQP8) mRNA and protein levels were significantly increased in the colon of UC patients compared to controls. Genetic analysis of the six exons and the promoter region of AQP8, however, revealed no mutations or polymorphisms in IBD patients.

CONCLUSION: Our results suggest that upregulation of AQP8 in the colon of UC patients represents a secondary phenomenon which may, due to altered water exchange of the distal intestinal mucosa, disturb the physiologic colonic mucus barrier and thus lead to chronic infla-mmation and ulceration.

Other mucoactive agents for cystic fibrosis

This review examines specific mucoactive agents from three classes: expectorants, which add water to the airway; ion-transport modifiers, which promote ion and water transport across the epithelium of the airway; and mucokinetics, which improve cough-mediated clearance by increasing airflow or reducing sputum adhesivity. The agents are isotonic and hypertonic saline, mannitol, denufosol and beta-agonists. Our understanding of these agents has recently improved through pre-clinical research, clinical trials and, in particular, extensive research into the nature of the liquid lining the surface of the airway, both in health and in cystic fibrosis (CF). For each agent, recent research is reviewed, highlighting the evidence for possible mechanisms of action and for clinical efficacy in CF, as well as the implications for the optimal clinical application of the agent.

Mucociliary clearance – a critical upper airway host defense mechanism and methods of assessment

PURPOSE OF REVIEW

Mucociliary clearance is a critical host defense mechanism of the airways. Effective mucociliary clearance requires appropriate mucus production and coordinated ciliary activity. The important role of these two components is best demonstrated in disorders such as primary ciliary dyskinesia and cystic fibrosis, both of which lead to lifelong recurrent respiratory tract infections. We review the methods used to analyze mucociliary clearance.

RECENT FINDINGS

Utilization of microdialysis probes has improved temporal resolution of mucociliary clearance in murine airways, availing many genetic mouse models to critical mucociliary clearance analysis, while improved fixation technique for transmission electron microscopy has allowed for detailed resolution of the airway surface liquid. High-speed digital video analysis has improved quantification of ciliary beat frequency while advancements in air-liquid interface culturing techniques have generated in-vitro models to investigate mucociliary clearance.

SUMMARY

Advancements in techniques for analysis of mucociliary clearance have improved our understanding of the interaction between the respiratory epithelium and the airway surface liquid, resulting in the ability to study pathologic processes involving mucociliary clearance in great detail.

CFTR inhibition mimics the cystic fibrosis inflammatory profile

Primary airway epithelial cells grown in air-liquid interface differentiate into cultures that resemble native epithelium morphologically, express ion transport similar to those in vivo, and secrete cytokines in response to stimuli. Comparisons of cultures derived from normal and cystic fibrosis (CF) individuals are difficult to interpret due to genetic differences besides CFTR. The recently discovered CFTR inhibitor, CFTRinh-172, was used to create a CF model with its own control to test if loss of CFTR-Cl− conductance alone was sufficient to initiate the CF inflammatory response. Continuous inhibition of CFTR-Cl− conductance for 3–5 days resulted in significant increase in IL-8 secretion at basal ( P = 0.006) and in response to 109 Pseudomonas ( P = 0.0001), a fourfold decrease in Smad3 expression ( P = 0.02), a threefold increase in RhoA expression, and increased NF-κB nuclear translocation upon TNF-α/IL-1β stimulation ( P < 0.000001). CFTR inhibition by CFTRinh-172 over this period does not increase epithelial sodium channel activity, so lack of Cl− conductance alone can mimic the inflammatory CF phenotype. CFTRinh-172 does not affect IL-8, IL-6, or granulocyte/macrophage colony-stimulating factor secretion in two CF phenotype immortalized cell lines: 9/HTEo− pCEP-R and 16HBE14o− AS, or IL-8 secretion in primary CF cells, and inhibitor withdrawal abolishes the increased response, so CFTRinh-172 effects on cytokines are not direct. Five-day treatment with CFTRinh-172 does not affect cells deleteriously as evidenced by lactate dehydrogenase, trypan blue, ciliary activity, electron micrograph histology, and inhibition reversibility. Our results support the hypothesis that lack of CFTR activity is responsible for the onset of the inflammatory cascade in the CF lung.

A model of tracer transport in airway surface liquid

This study is concerned with reconciling theoretical modelling of the fluid flow in the airway surface liquid with experimental visualisation of tracer transport in human airway epithelial cultures. The airways are covered by a dense mat of cilia of length approximately 6 microm beating in a watery periciliary liquid (PCL). Above this there is a layer of viscoelastic mucus which traps inhaled pathogens. Cilia propel mucus along the airway towards the trachea and mouth. Theoretical analyses of the beat cycle (smith et al., 2006b; Fulford and Blake, 1986) predict small transport of PCL compared with mucus, based on the assumption that the epithelium is impermeable to fluid. However, an experimental study (Matsui et al., 1998) indicates nearly equal transport of PCL and mucus. Building on existing understanding of steady advection-diffusion in the ASL (Blake and Gaffney, 2001; Mitran, 2004), numerical simulation of an advection-diffusion model of tracer transport is used to test several proposed flow profiles and to test the importance of oscillatory shearing caused by the beating cilia. A mechanically derived oscillatory flow with very low mean transport of PCL results in relatively little 'smearing' of the tracer pulses. Other effects such as mixing between the PCL and mucus, and significant transport in the upper part of the PCL above the cilia tips are tested and result in still closer transport, with separation between the tracer pulses in the two layers being less than 9%. Furthermore, experimental results may be replicated to a very high degree of accuracy if mean transport of PCL is only 50% of mucus transport, significantly less than the mean PCL transport first inferred on the basis of experimental results.

Multifunctional antimicrobial peptides: therapeutic targets in several human diseases

Antimicrobial peptides have emerged as promising agents against antibiotic-resistant pathogens. They represent essential components of the innate immunity and permit humans to resist infection by microbes. These gene-encoded peptides are found mainly in phagocytes and epithelial cells, showing a direct activity against a wide range of microorganisms. Their role has now broadened from that of simply endogenous antibiotics to multifunctional mediators, and their antimicrobial activity is probably not the only primary function. Although antimicrobial peptide deficiency, dysregulation, or overproduction is not known to be a direct cause of any single human disease, numerous studies have now provided compelling evidence for their involvement in the complex network of immune responses and inflammatory diseases, thereby influencing diverse processes including cytokine release, chemotaxis, angiogenesis, wound repair, and adaptive immune induction. The purpose of this review is to highlight recent literature, showing that antimicrobial peptides are associated with several human conditions including infectious and inflammatory diseases, and to discuss current clinical development of peptide-based therapeutics for future use.

Inhaled hypertonic saline as a therapy for cystic fibrosis

PURPOSE OF REVIEW

The beneficial effect of a short course of nebulized hypertonic saline on lung function for people with cystic fibrosis was first identified in 1996. At that time, competing hypotheses about the pathogenesis of cystic fibrosis lung disease predicted very different responses to long-term inhalation of hypertonic saline.

RECENT FINDINGS

Recent benchtop research supports the hypothesis that the liquid layer lining the airways is depleted in cystic fibrosis. In addition to osmotically restoring this liquid layer, hypertonic saline improves the rheological properties of the mucus and stimulates cough. The net result is accelerated mucus clearance that is short-lived for single doses but sustained with regular inhalation. Long-term use improves lung function mildly but has marked benefits with respect to exacerbations, quality of life and absenteeism, without promoting infection or inflammation.

SUMMARY

Hypertonic saline appears broadly applicable as an inexpensive therapy for most patients with cystic fibrosis.

The role of airway secretions in COPD--clinical applications

It has been established that mucus hypersecretion and decreased mucus clearance contribute to the morbidity of chronic obstructive pulmonary disease (COPD). Indeed, the classic definition of chronic bronchitis relies on determining the frequency and duration of sputum expectoration. Despite the well recognized importance of this symptom, there are few therapies routinely used to decrease the sputum production or to improve clearance. There are fewer well conducted clinical trials of existing medications and this has led many regulatory agencies, notably the Food and Drug Administration (FDA), to refuse to register these medications or approve their sale. Similarly, airway clearance devices and chest physical therapy have not been well studied in COPD. Carefully conducted studies of interventions to improve airway clearance, similar to those done in cystic fibrosis (CF), may help us to identify effective therapies and possibly novel diagnostic tests for the management of COPD.

Proteomic identification and characterization of bacterial factors associated with Burkholderia cenocepacia survival in a murine host

Burkholderia cenocepacia is a member of the Burkholderia cepacia complex, a diverse family of Gram-negative bacteria that are serious respiratory pathogens in immunocompromised patients and individuals with cystic fibrosis. To identify putative bacterial virulence determinants, proteomic profiles were compared between two B. cenocepacia isolates that demonstrated differential persistence in a mouse model of pulmonary infection; clinical isolate C1394 is rapidly cleared from the murine lung whereas the strain variant, C1394mp2, persists. Two-dimensional (2D) gel electrophoresis was used to identify candidate proteins involved in B. cenocepacia survival in a susceptible host. The 2D proteome of the persistent isolate (C1394mp2) revealed loss of an alkyl hydroperoxide reductase subunit C (AhpC) protein spot and increased production of flagellin proteins. Loss of AhpC expression in C1394mp2 correlated with enhanced susceptibility to oxidative stress. C1394mp2 expressed increased flagellin production and enhanced swimming motility, traits that were subject to regulation by heat and low pH. Together, these results revealed differential expression and stress regulation of putative virulence determinants associated with B. cenocepacia persistence in a susceptible host.

Evidence for airway surface dehydration as the initiating event in CF airway disease

Cystic fibrosis (CF) lung disease reflects persistent bacterial infection of airway lumens. Several hypotheses have been advanced to link mutations in the CFTR gene to the failure of the CF lung to defend itself against bacterial infection. Amongst the most productive hypotheses at present is the ''low airway surface liquid (ASL) volume'' or ''dehydration'' hypothesis. This hypothesis predicts that airway surface dehydration produces the mucus adhesion, inflammation, and bacterial biofilm formation characteristic of CF. Clinical trials of inhaled hypertonic saline have demonstrated therapeutic benefit of manoeuvres designed to rehydrate CF airway surfaces.

The lactoperoxidase system links anion transport to host defense in cystic fibrosis

Chronic respiratory infections in cystic fibrosis result from CFTR channel mutations but how these impair antibacterial defense is less clear. Airway host defense depends on lactoperoxidase (LPO) that requires thiocyanate (SCN-) to function and epithelia use CFTR to concentrate SCN- at the apical surface. To test whether CFTR mutations result in impaired LPO-mediated host defense, CF epithelial SCN- transport was measured. CF epithelia had significantly lower transport rates and did not accumulate SCN- in the apical compartment. The lower CF [SCN-] did not support LPO antibacterial activity. Modeling of airway LPO activity suggested that reduced transport impairs LPO-mediated defense and cannot be compensated by LPO or H2O2 upregulation.

Neutrophil elastase, an innate immunity effector molecule, represses flagellin transcription in Pseudomonas aeruginosa

Recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors triggers an innate immune response to colonizing or invading bacteria. Conversely, many bacteria have evolved mechanisms to dampen this response by downregulating the synthesis of such PAMPs. We have previously demonstrated that Pseudomonas aeruginosa growing in mucopurulent human respiratory mucus from cystic fibrosis patients represses the expression of its flagellin, a potent stimulant of the innate immune response. Here we demonstrate that this phenomenon occurs in response to the presence of neutrophil elastase in such mucus. Nonpurulent mucus from animals had no such repressive effect. Furthermore, lysed neutrophils from human blood reproduced the flagellin-repressive effect ex mucus and, significantly, had no effect on the viability of this organism. Neutrophil elastase, a component of the innate host defense system, has been described to be bactericidal for gram-negative bacteria and to degrade bacterial virulence factors. Thus, the resistance of P. aeruginosa to the bactericidal effect of neutrophil elastase, as well as this organism's ability to sense this enzyme's presence and downregulate the synthesis of a PAMP, may be the key factors in allowing P. aeruginosa to colonize the lungs. These findings demonstrate the dynamic nature of this bacterium's response to host defenses that ensures its success as a colonizer and also highlights the dual nature of defense molecules that confer advantages and disadvantages to both hosts and pathogens.

A novel host defense system of airways is defective in cystic fibrosis

RATIONALE

The respiratory tract is constantly exposed to airborne microorganisms. Nevertheless, normal airways remain sterile without recruiting phagocytes. This innate immune activity has been attributed to mucociliary clearance and antimicrobial polypeptides of airway surface liquid. Defective airway immunity characterizes cystic fibrosis (CF), a disease caused by mutations in the CF transmembrane conductance regulator, a chloride channel. The pathophysiology of defective immunity in CF remains to be elucidated.

OBJECTIVE

We investigated the ability of non-CF and CF airway epithelia to kill bacteria through the generation of reactive oxygen species (ROS).

METHODS

ROS production and ROS-mediated bactericidal activity were determined on the apical surfaces of human and rat airway epithelia and on cow tracheal explants.

MEASUREMENTS AND MAIN RESULTS

Dual oxidase enzyme of airway epithelial cells generated sufficient H(2)O(2) to support production of bactericidal hypothiocyanite (OSCN(-)) in the presence of airway surface liquid components lactoperoxidase and thiocyanate (SCN(-)). This OSCN(-) formation eliminated Staphylococcus aureus and Pseudomonas aeruginosa on airway mucosal surfaces, whereas it was nontoxic to the host. In contrast to normal epithelia, CF epithelia failed to secrete SCN(-), thereby rendering the oxidative antimicrobial system inactive.

CONCLUSIONS

These data indicate a novel innate defense mechanism of airways that kills bacteria via ROS and suggest a new cellular and molecular basis for defective airway immunity in CF.

Host antimicrobial defence peptides in human disease

Antimicrobial peptides or host defence peptides are endogenous peptide antibiotics, which have been confirmed as an essential part of the immune system. Apart from direct killing of bacteria, a role for the peptides in antiviral and immunomodulatory functions has recently been claimed. In this chapter we have focused on the host contact with microbes, where these host defence peptides are key players. The interplay with commensals and pathogens in relation to antimicrobial peptide expression is discussed, with specific emphasis on the respiratory and the alimentary systems. A possible novel difference in epithelial interactions between commensals and pathogens is considered in relation to disease.

Antimicrobial peptides in the airway

The airway provides numerous defense mechanisms to prevent microbial colonization by the large numbers of bacteria and viruses present in ambient air. An important component of this defense is the antimicrobial peptides and proteins present in the airway surface fluid (ASF), the mucin-rich fluid covering the respiratory epithelium. These include larger proteins such as lysozyme and lactoferrin, as well as the cationic defensin and cathelicidin peptides. While some of these peptides, such as human beta-defensin (hBD)-1, are present constitutively, others, including hBD2 and -3 are inducible in response to bacterial recognition by Toll-like receptor-mediated pathways. These peptides can act as microbicides in the ASF, but also exhibit other activities, including potent chemotactic activity for cells of the innate and adaptive immune systems, suggesting they play a complex role in the host defense of the airway. Inhibition of antimicrobial peptide activity or gene expression can result in increased susceptibility to infections. This has been observed with cystic fibrosis (CF), where the CF phenotype leads to reduced antimicrobial capacity of peptides in the airway. Pathogenic virulence factors can inhibit defensin gene expression, as can environmental factors such as air pollution. Such an interference can result in infections by airway-specific pathogens including Bordetella bronchiseptica, Mycobacterium tuberculosis, and influenza virus. Research into the modulation of peptide gene expression in animal models, as well as the optimization of peptide-based therapeutics shows promise for the treatment and prevention of airway infectious diseases.

Regulation of chemokine expression by NaCl occurs independently of cystic fibrosis transmembrane conductance regulator in macrophages

Chronic pulmonary inflammation and infection are the leading causes of morbidity and mortality in cystic fibrosis (CF). While the effect of mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) on airways remains controversial, some groups have demonstrated increases in Na(+) and Cl(-) in CF airway surface liquid compared to normal airways. We investigated the consequences of NaCl on pro-inflammatory chemokine and cytokine production by macrophages. Stimulation of mouse macrophages with increasing amounts of NaCl induced macrophage inflammatory protein-2 (MIP-2) and tumor necrosis factor-alpha (TNF-alpha) production. Further, co-incubation of macrophages with NaCl in the presence of either lipopolysaccharide (LPS) or TNF-alpha synergistically increased MIP-2 production. Both the NaCl and NaCl plus LPS responses were partially dependent on endogenous production and autocrine signaling by TNF-alpha. To investigate the role of CFTR in MIP-2 production, we compared the responses of wild-type and DeltaF508 CF mouse macrophages to NaCl and LPS. The responses of macrophages from both strains were indistinguishable. In addition, CFTR mRNA was not expressed in macrophages. Taken together, these findings suggest that NaCl stimulates MIP-2 production by macrophages through a mechanism that is partially dependent on TNF-alpha but independent of macrophage CFTR expression.

Relationships between cystic fibrosis transmembrane conductance regulator, extracellular nucleotides and cystic fibrosis

Cystic fibrosis (CF) is one of the most common lethal autosomal recessive genetic diseases in the Caucasian population, with a frequency of about 1 in 3000 livebirths. CF is due to a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene encoding the CFTR protein, a cyclic adenosine 5'-monophosphate (cAMP)-regulated chloride channel localized in the apical membrane of epithelial cells. CFTR is a multifunctional protein which, in addition to be a Cl-channel, is also a regulator of multiple ion channels and other proteins. In particular CFTR has been reported to play a role in the outflow of adenosine 5'-triphosphate (ATP) from cells, but this remains controversial. Extracellular nucleotides are signaling molecules that regulate ion transport and mucociliary clearance by acting on P2 nucleotide receptors, in particular the P2Y(2) receptor. Nucleotides activating the P2Y(2) receptor represent thus one pharmacotherapeutic strategy to treat CF disease, via improvement of mucus hydration and mucociliary clearance in airways. Phase II clinical trials have recently shown that aerosolized denufosol (INS37217, Inspire(R)) improves pulmonary function in CF patients: denufosol was granted orphan drug status and phase III trials are planned. Here, we review what is known about the relationship between extracellular nucleotides and CFTR, the role of extracellular nucleotides in epithelial pathophysiology and their putative role as therapeutic agents.

Cystic fibrosis enters the proteomics scene: New answers to old questions

The discovery in 1989 of the gene encoding for the cystic fibrosis transmembrane conductance regulator (CFTR) and its mutation as the primary cause of cystic fibrosis (CF), generated an optimistic reaction with respect to the development of potential therapies. This extraordinary milestone, however, represented only the initial key step in a long path. Many of the mechanisms that govern the pathogenesis of CF, the most commonly inherited lethal pulmonary disorder in Caucasians, remain even today unknown. As a continuation to genomic research, proteomics now offers the unique advantage to examine global alterations in the protein expression patterns of CF cells and tissues. The systematic use of this approach will probably provide new insights into the cellular mechanisms involved in CF dysfunctions, and should ultimately result in the finding of new prognostic markers, and in the generation of new therapies. In this article we review the current status of proteomic research applied to the study of CF, including CFTR-related interactomics, and evaluate the potential of these technologies for future investigations.

A viscoelastic traction layer model of muco-ciliary transport

A new mathematical model of the transport of mucus and periciliary liquid (PCL) in the airways by cilia is presented. Mucus is represented by a linearly viscoelastic fluid, the mat of cilia is modelled as an 'active porous medium.' The propulsive effect of the cilia is modelled by a time-dependent force acting in a shear-thinned 'traction layer' between the mucus and the PCL. The effects of surface and interface tension are modelled by constraining the mucus free surface and mucus-PCL interface to be flat. It is assumed that the epithelium is impermeable to fluid. Using Fourier series, the system is converted into ODEs and solved numerically. We calculate values for mean mucus speed close to those observed by Matsui et al. [J. Clin. Invest., 102(6):1125-1131, 1998], (approximately 40 microm s(-1)). We obtain more detail regarding the dynamics of the flow and the nonlinear relationships between physical parameters in healthy and diseased states than in previously published models. Pressure gradients in the PCL caused by interface and surface tension are vital to ensuring efficient transport of mucus, and the role of the mucus-PCL interface appears to be to support such pressure gradients, ensuring efficient transport. Mean transport of PCL is found to be very small, consistent with previous analyses, providing insight into theories regarding the normal tonicity of PCL.

Novel effects of azithromycin on tight junction proteins in human airway epithelia

The macrolide antibiotic azithromycin improves lung function and prognosis among patients with cystic fibrosis or diffuse panbronchiolitis, independently of bacterial eradication. Anti-inflammatory effects have been implicated, but data from in vivo studies are scarce, and the link between abnormal electrolyte content in airway surface liquid and bronchial infections remains uncertain. In the present study, we treated human airway epithelia on filter supports with azithromycin and monitored transepithelial electrical resistance. We found that azithromycin increased transepithelial electrical resistance of airway epithelia in a dose-dependent manner. Immunocytochemistry and Western blotting showed that addition of azithromycin changed the locations of proteins in cell cultures and induced processing of the tight junction proteins claudin-1 and claudin-4, occludin, and junctional adhesion molecule-A. These effects were reversible, and no effect was seen when cells were treated with penicillin or erythromycin. The data indicate that azithromycin increases the transepithelial electrical resistance of human airway epithelia by changing the processing of tight junction proteins. The results are novel and may help explain the beneficial effects of azithromycin in patients with cystic fibrosis, diffuse panbronchiolitis, and community-acquired pneumonia.

Biological activity of Tat (47–58) peptide on human pathogenic fungi

Tat (47-58) peptide, a positively charged Arginine-rich peptide derived from HIV-1 regulatory protein Tat, is known for a peptidic delivery factor as a cell-penetrating peptide on mammalian cells. In this study, antifungal effect and its mode of action of Tat peptide were investigated on fungal cells. The results indicate that Tat peptide exhibits antifungal activity against pathogenic fungal cells without hemolytic effect on human erythrocytes. To understand the mechanism(s) of Tat peptide, the cellular distribution of the peptide was investigated. Tat peptide internalized in the fungal cells without any damage to cell membrane when examined using an artificial liposome (PC/cholesterol; 10:1, w/w). Moreover, flow cytometry analysis exhibited the uptake of Tat peptide by energy- and salt-independent pathway, and confocal scanning microscopy displayed that this peptide accumulated in the nucleus of fungal cells rapidly without any impediment by time or temperature, which generally influence on the viral infections. After penetration into the nuclear, the peptide affected the process of cell cycle of Candida albicans through the arrest at G1 phase.

Composition of nasal airway surface liquid in cystic fibrosis and other airway diseases determined by X-ray microanalysis

The ionic composition of the airway surface liquid (ASL) in healthy individuals and in patients with cystic fibrosis (CF) has been debated. Ion transport properties of the upper airway epithelium are similar to those of the lower airways and it is easier to collect nasal ASL from the nose. ASL was collected with ion exchange beads, and the elemental composition of nasal fluid was determined by X-ray microanalysis in healthy subjects, CF patients, CF heterozygotes, patients with rhinitis, and with primary ciliary dyskinesia (PCD). In healthy subjects, the ionic concentrations were approximately isotonic. In CF patients, CF heterozygotes, rhinitis, and PCD patients, [Na] and [Cl] were significantly higher compared when compared with those in controls. [K] was significantly higher in CF and PCD patients compared with that in controls. Severely affected CF patients had higher ionic concentrations in their nasal ASL than in patients with mild or moderate symptoms. Female CF patients had higher levels of Na, Cl, and K than male patients. As higher salt concentrations in the ASL are also found in other patients with airway diseases involving chronic inflammation, it appears likely that inflammation-induced epithelial damage is important in determining the ionic composition of the ASL.

Applications of microscopy to genetic therapy of cystic fibrosis and other human diseases

Gene therapy has become an extremely important and active field of biomedical research. Microscopy is an integral component of this effort. This chapter presents an overview of imaging techniques used in our facility in support of cystic fibrosis gene therapy research. Instrumentation used in these studies includes light and confocal microscopy, transmission electron microscopy, and scanning electron microscopy. Techniques outlined include negative staining, cryo-electron microscopy, three-dimentional reconstruction, enzyme cytochemistry, immunocytochemistry, and fluorescence imaging.

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.