Understanding the control of Pseudomonas aeruginosa alginate synthesis and the prospects for management of chronic infections in cystic fibrosis

Decades of research have been dedicated to the study of the opportunistic pathogen Pseudomonas aeruginosa, a Gram-negative, environmental bacterium that secretes the exopolysaccharide alginate during chronic lung infection of cystic fibrosis (CF) patients. Although P. aeruginosa utilizes a variety of factors to establish a successful infection in the lungs of CF patients, alginate has stood out as one of the best-studied prognostic indicators of chronic lung infection. While the genetics, biosynthesis and regulation of alginate are well understood, questions still remain concerning its role in biofilm development and its potential as a therapeutic target. The purpose of this review is to provide a brief summary of alginate biosynthesis and regulation, and to highlight recent discoveries in the areas of alginate production, biofilm formation and vaccine design. This information is placed in context with a proposed P. aeruginosa infectious pathway, highlighting avenues for the use of existing therapies as well as the potential for novel agents to reduce or eliminate chronic infections in CF patients.     

Endocrine parameters of cystic fibrosis: Back to basics

Dramatic changes in the life expectancy of cystic fibrosis (CF) patients are occurring, creating a cohort of aging individuals experiencing long‐term complications of this chronic disease. The two most common of these complications include CF‐related diabetes and CF bone disease. The clinical implications of each have become better understood, as have potential therapies. However, data obtained from the basic science studies of both diseases have not been widely recognized. In this review, we focus on the known and hypothesized pathogenesis of these two disorders. Additionally, the molecular underpinnings of CF will be explained along with the potential interactions with endocrine disease phenotypes. J. Cell. Biochem. 108: 353–361, 2009. © 2009 Wiley‐Liss, Inc.     

Hyperacidification in cystic fibrosis: links with lung disease and new prospects for treatment

A new link between the genetic defect and lung pathology in cystic fibrosis (CF) has been established by the recent discovery of an abnormally acidic pH in the organelles of CF respiratory epithelial cells, along with an increased acidity of the CF airway surface liquid. The defect in cystic fibrosis transmembrane resistance regulator (CFTR) results in hyperacidification of the trans-Golgi network, an organelle responsible for glycosylation, and protein- and membrane-sorting in mammalian cells. Hyperacidification and altered surface glycoconjugates might contribute to mucus thickening, bacterial adhesion and colonization, inflammation, and irreversible tissue damage. The increased acidity of the intracellular organelles and of the lung lining in CF could be linked, and both represent potential therapeutic targets.     

Cystic Fibrosis-Related Diabetes Mellitus: Etiology,Evaluation, and Management

ObjectiveTo review the pathophysiology, diagnosis, and management of cystic fibrosis-related diabetes mellitus (CFRD).MethodsWe performed a MEDLINE search of the literature, using the search terms “cystic fibrosis-related diabetes, “CFRD,” and “cystic fibrosis and diabetes,” to identify pertinent articles available in English.ResultsIn patients with cystic fibrosis (CF), CFRD is a major cause for an accelerated decline in health. It is the result of multiple pathophysiologic mechanisms, including destruction of pancreatic islet cells, impaired hepatic response to the antigluconeogenic effects of insulin, and impaired insulin sensitivity. Nutritional management and adequate caloric intake are paramount to successful management of CF. Although insulin remains the standard of care for treating CFRD in conjunction with fasting hyperglycemia, a small but growing body of literature supports the use of oral therapies. In this article, we discuss the benefits of and possible adverse reactions to the various classes of oral and injectable agents used in the treatment of diabetes mellitus, with special attention to the population of patients with CF.ConclusionOrally administered agents can have a role in the treatment of CFRD. Further study is needed to determine the optimal combination of therapeutic modalities for CFRD. (Endocr Pract. 2008;14:1169-1179)     

Some like it hot: curcumin and CFTR

The activation of mutant forms of the cystic fibrosis transmembrane conductance regulator (CFTR), particularly the most frequent mutant allele (DeltaF508), is a potential strategy for the treatment of the disease cystic fibrosis (CF). Therefore, it is of great interest that curcumin, a component of the spice turmeric, is reported to restore function to this allele, both in heterologous expression systems and in DeltaF508 CF mice. Although other laboratories have not been able to confirm the initial observations, activating DeltaF508 CFTR could have such important therapeutic implications that a thorough investigation of the potential of curcumin is warranted.     

Endotoxic activity of lipopolysaccharides isolated from emergent potential cystic fibrosis pathogens

Improved antimicrobial therapies against the classical spectrum of pathogenic bacteria which colonise the lungs of cystic fibrosis (CF) patients has resulted in improved life expectancy and quality of life. Bacterial species that are resistant to a broad range of antibiotics including Stenotrophomonas maltophilia and Alcaligenes xylosoxidans have now emerged as potential new pathogens to fill the niche. At present, it is unclear from clinical data whether these microbes are commensal or pathogenic. In this study we have quantified the inflammatory potential of lipopolysaccharide (LPS) from eight species of Gram-negative organisms which have been cultured with increasing frequency from CF patients. Inflammatory responses induced by LPS from whole human blood and a human-derived monocyte cell line (THP-1) were assessed. Enzyme-linked immunosorbent assays were used to detect interleukin-6, interleukin-8, and tumour necrosis factor alpha (TNF). A bioassay was also used to assess TNF activity. With the exception of S. maltophilia, LPS extracted from all of the bacteria tested upregulated, by varying degrees, expression of each of the proinflammatory cytokines assayed. This study represents the first comprehensive report of the endotoxic potential of a new wave of microbes which are associated with CF.     

Cystic fibrosis and calcium oxalate nephrolithiasis.

During the past six years, we have treated eight patients with cystic fibrosis (CF) for nephrolithiasis. In seven patients, the stones were comprised of calcium oxalate. Another six patients had calcium oxalate crystalluria. In our CF population of 140 patients, this represents a cumulative incidence of calcium oxalate nephrolithiasis of 5.7 percent and an additional 4.2 percent incidence of crystalluria. Experience with these patients is reviewed. Pancreatic insufficiency was universally associated with nephrolithiasis or crystalluria. Diabetes and cirrhosis were also common. Predisposing factors and potential mechanisms of stone disease in pancreatic insufficient CF patients are discussed, focusing on the relationship between fat malabsorption in CF to oxalate metabolism.     

Cystic fibrosis--the way forward from the gene.

Cloning of the cystic fibrosis (CF) gene and elucidation of the physiological functions of the encoded protein is a triumph, not only for molecular biology, but also for people affected by CF. For them, not only is there now the possibility of screening for the commonest mutations, but they may also look forward to the prospect of improved therapies being developed.     

A synthetic chloride channel restores chloride conductance in human cystic fibrosis epithelial cells

Mutations in the gene-encoding cystic fibrosis transmembrane conductance regulator (CFTR) cause defective transepithelial transport of chloride (Cl(-)) ions and fluid, thereby becoming responsible for the onset of cystic fibrosis (CF). One strategy to reduce the pathophysiology associated with CF is to increase Cl(-) transport through alternative pathways. In this paper, we demonstrate that a small synthetic molecule which forms Cl(-) channels to mediate Cl(-) transport across lipid bilayer membranes is capable of restoring Cl(-) permeability in human CF epithelial cells; as a result, it has the potential to become a lead compound for the treatment of human diseases associated with Cl(-) channel dysfunction.     

Cystic fibrosis transmembrane conductance regulator and the etiology and pathogenesis of cystic fibrosis.

Cystic fibrosis (CF) is an inherited disorder causing pancreatic, pulmonary, and sinus disease in children and young adults. Abnormal viscosity of mucous secretions is a hallmark of the disease, and is believed to be the result of altered electrolyte transport across epithelial cell membranes. The monogenic etiology of this disease has been apparent for more than 40 years, but the defective gene has only recently been identified. This was made possible because of a revolution in genetic technology, called positional cloning, which can pinpoint disease genes without previous knowledge of the abnormal protein product. The protein encoded by the gene defective in CF has been termed the CF transmembrane conductance regulator (CFTR) because of its postulated role in electrolyte transport. Studies investigating the normal function of CFTR and how mutations affect that function, thereby causing CF, have required the combined skills of clinicians, geneticists, molecular biologists, and physiologists. From this collaborative effort a greater understanding of the pathogenesis of this disorder is now emerging. It may soon be possible to introduce novel therapies derived from this new knowledge that will be aimed directly at the basic defect. An ever-increasing number of genes of unknown function will be identified by continuing advances in molecular genetic technology and the advent of the genome sequencing project. The experience in cystic fibrosis research may prove to be a paradigm for investigation of the function of genes isolated by positional cloning methods.     

Voice Disorder in Cystic Fibrosis Patients

Cystic fibrosis is a common autosomal recessive disorder with drastic respiratory symptoms, including shortness of breath and chronic cough. While most of cystic fibrosis treatment is dedicated to mitigating the effects of respiratory dysfunction, the potential effects of this disease on vocal parameters have not been systematically studied. We hypothesized that cystic fibrosis patients, given their characteristic respiratory disorders, would also present dysphonic symptoms. Given that voice disorders can severely impair quality of life, the identification of a potential cystic fibrosis-related dysphonia could be of great value for the clinical evaluation and treatment of this disease. We tested our hypothesis by measuring vocal parameters, using both objective physical measures and the GRBAS subjective evaluation method, in male and female cystic fibrosis patients undergoing conventional treatment and compared them to age and sex matched controls. We found that cystic fibrosis patients had a significantly lower vocal intensity and harmonic to noise ratio, as well as increased levels of jitter and shimmer. In addition, cystic fibrosis patients also showed higher scores of roughness, breathiness and asthenia, as well as a significantly altered general grade of dysphonia. When we segregated the results according to sex, we observed that, as a group, only female cystic fibrosis patients had significantly lower values of harmonic to noise ratio and an abnormal general grade of dysphonia in relation to matched controls, suggesting that cystic fibrosis exerts a more pronounced effect on vocal parameters of women in relation to men. Overall, the dysphonic characteristics of CF patients can be explained by dysfunctions in vocal fold movement and partial upper airway obstruction, potentially caused by the accumulation of mucus and chronic cough characteristic of CF symptomatology. Our results show that CF patients exhibit significant dysphonia and suggest they may potentially benefit from voice therapy as a parallel treatment strategy.     

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.     

Detection of a NotI polymorphism with the pmetH probe by pulsed-field gel electrophoresis.

The pmetH probe, tightly linked to the locus for cystic fibrosis (CF), detected a NotI polymorphism with allele sizes of 1,000 and 550 kb that could be separated by pulsed-field gel electrophoresis. Both alleles were found on chromosomes bearing either the normal or the CF allele. Preliminary data showed that this polymorphism was not in strong linkage disequilibrium with the CF locus. Preliminary large-scale restriction mapping of the fragment showed that the NotI polymorphic site is 200-370 kb distant from the MET locus; thus it defines a new polymorphic locus in the CF region. This locus is of potential interest for studying CF families that show recombinants between CF and its tightly linked probes, in order to increase the precision of the genetic map of the region.     

Antioxidants in cystic fibrosis. Conclusions from the CF antioxidant workshop, Bethesda, Maryland, November 11-12, 2003

Although great strides are being made in the care of individuals with cystic fibrosis (CF), this condition remains the most common fatal hereditary disease in North America. Numerous links exist between progression of CF lung disease and oxidative stress. The defect in CF is the loss of function of the transmembrane conductance regulator (CFTR) protein; recent evidence that CFTR expression and function are modulated by oxidative stress suggests that the loss may result in a poor adaptive response to oxidants. Pancreatic insufficiency in CF also increases susceptibility to deficiencies in lipophilic antioxidants. Finally the airway infection and inflammatory processes in the CF lung are potential sources of oxidants that can affect normal airway physiology and contribute to the mechanisms causing characteristic changes associated with bronchiectasis and loss of lung function. These multiple abnormalities in the oxidant/antioxidant balance raise several possibilities for therapeutic interventions that must be carefully assessed.     

Unique presentations and chronic complications in adult cystic fibrosis: do they teach us anything about CFTR?

The increase in numbers of adults with cystic fibrosis (CF) has allowed us to identify previously unrecognized chronic complications of CF, as well as appreciate unique presentations of cystic fibrosis-related diseases. Do these chronic complications and unique presentations provide us with new insight into cystic fibrosis transmembrane conductance regulator (CFTR) function? Current data suggest that the 'chronic complications' reveal mainly the effect of a long-term absence of previously recognized CFTR functions. In contrast, the 'unique presentations' provide new insight into the role of CFTR in different tissues.     

Intrinsic pro-angiogenic status of cystic fibrosis airway epithelial cells

Cystic fibrosis is a common genetic disorder characterized by a severe lung inflammation and fibrosis leading to the patient's death. Enhanced angiogenesis in cystic fibrosis (CF) tissue has been suggested, probably caused by the process of inflammation, as similarly described in asthma and chronic bronchitis. The present study demonstrates an intrinsic pro-angiogenic status of cystic fibrosis airway epithelial cells. Microarray experiments showed that CF airway epithelial cells expressed several angiogenic factors such as VEGF-A, VEGF-C, bFGF, and PLGF at higher levels than control cells. These data were confirmed by real-time quantitative PCR and, at the protein level, by ELISA. Conditioned media of these cystic fibrosis cells were able to induce proliferation, migration and sprouting of cultured primary endothelial cells. This report describes for the first time that cystic fibrosis epithelial cells have an intrinsic angiogenic activity. Since excess of angiogenesis is correlated with more severe pulmonary disease, our results could lead to the development of new therapeutic applications.     

Prospects for virus-based gene therapy for cystic fibrosis

Gene therapy for cystic fibrosis (CF) could potentially be accomplished with one of several recombinant virus vectors, including a murine retrovirus (MMuLV), adenovirus, or adeno-associated virus (AAV). All these vectors take advantage of their respective viruses' mechanisms for delivery of viral DNA to cells, evasion of lyosomal degradation, and optimization of the levels and duration of expression of viral (or vector) DNA. Each has its own unique life cycle, however. The differences among these viruses result in certain advantages and disadvantages, such as the requirement of retroviruses for active cell division, and the potential pathogenic effects from expression of certain adenovirus genes present in adenovectors. While no single vector may be optimal for CF gene therapy in humans, new techniques, such as receptor-mediated gene transfer, seek to take advantage of the desirable properties of one or more of the virus-based systems while avoiding certain potential hazards.     

The metabolomics of airway diseases,including COPD,asthma and cystic fibrosis

Abstract

Chronic obstructive pulmonary disease (COPD), asthma and cystic fibrosis (CF) are characterized by airway obstruction and an inflammatory process. Reaching early diagnosis and discrimination of subtypes of these respiratory diseases are quite a challenging task than other chronic illnesses. Metabolomics is the study of metabolic pathways and the measurement of unique biochemical molecules generated in a living system. In the last decade, metabolomics has already proved to be useful for the characterization of several pathological conditions and offers promises as a clinical tool. In this article, we review the current state of the metabolomics of COPD, asthma and CF with a focus on the different methods and instrumentation being used for the discovery of biomarkers in research and translation into clinic as diagnostic aids for the choice of patient-specific therapies.     

Mapping of genetic factors influencing the weight of cystic fibrosis knockout mice

One of the poorly understood clinical manifestations of cystic fibrosis (CF) is low body weight. Mice in which the CF causative gene, cystic fibrosis transmembrane conductance regulator (Cftr), has been knocked out reflect this as they are smaller than age-matched littermates. The variable weight of F2 Cftr -/- (CF) mice derived from a cross between congenic C57BL/6J and BALB/cJ Cftr heterozygotic mice permits the mapping of modifiers of this cystic fibrosis phenotype. In this report, quantitative trait loci (QTL) mapping was used to identify the chromosomal locations of genes that contribute to the body weight of 12-week-old F2 CF mice. Five loci of CF body weight were detected with four of the five acting in a sex-specific manner. Significant linkage of the phenotype to a region of Chromosome (Chr) 13 from D13Mit179 to D13Mit254 (LOD = 4.2) was established in female mice; and suggestive loci on Chrs 7 and 10 were identified. The weights of F2 male CF mice were suggestively linked to regions of Chrs 1 and 6, and to the same locus on Chr 7 as in female mice. The suggestive loci did not influence the weight of the limited set of control mice and thus are presumed to be CF specific in their effects. Further study of these putative CF body weight modifiers may provide insight on the pathogenesis of cystic fibrosis.