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PubMed1997

The biogenesis, traffic, and function of the cystic fibrosis transmembrane conductance regulator.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic AMP-activated chloride channel that is encoded by the gene that is defective in cystic fibrosis. This ion channel resides at the luminal surfaces and in endosomes of epithelial cells that line the airways, intestine, and a variety of exocrine glands. In this article we discuss current hypotheses regarding how CFTR functions as a regulated ion channel and how CF mutations lead to disease. We also evaluate the emerging notion that CFTR is a multifunctional protein that is capable of regulating epithelial physiology at several levels, including the modulation of other ion channels and the regulation of intracellular membrane traffic. Elucidating the various functions of CFTR should contribute to our understanding of the pathology in cystic fibrosis, the most common lethal genetic disorder among Caucasians.

Biological Transport↗

PubMed1990

Haemophilus infection in cystic fibrosis.

Twenty seven patients with cystic fibrosis under the age of 12 years and 27 matched patients with asthma were followed up in a prospective study for one year. The isolation rate of non-capsulated strains of Haemophilus influenzae from cough swabs and sputum specimens taken at routine clinic visits every two months was significantly greater in cystic fibrosis than in asthma. Haemophilus para-influenzae was equally common in both groups. During exacerbations the isolation rate of H influenzae in cystic fibrosis was significantly greater than at other times, whereas in asthma there was no significant difference. The distribution of biotypes of H influenzae and H parainfluenzae was similar in the two groups. In cystic fibrosis, biotype I was associated with exacerbations. Biotype V was more common than in previous studies, but was not associated with exacerbations.

Bacterial Typing Techniques↗

PubMed1976

Immunochemical studies of the plasma and cultured fibroblast media fractions containing the cystic fibrosis ciliary inhibitor.

The cystic fibrosis ciliary inhibitor (CFCI) has been fractionated from plasma of cystic fibrosis (CF) homozygotes and from the media of cultured fibroblasts derived from CF homozygotes. Plasma and fibroblast media from normal controls have been fractionated in an identical manner. Fractions from plasma and fibroblast culture media that demonstrate ciliary inhibitory activity contain several proteins in a molecular weight range of approximately 5,000-11,000. These proteins have been partially characterized by immunochemical analysis with antisera to 33 human serum proteins. Immunological determinants of albumin, C3 (but not C3a), C4, C5, alpha1-lipoprotein, beta-lipoprotein, beta2-microglobulin and immunoglobulin light chains have been detected by hemagglutination in fractions of CF plasma that inhibited ciliary activity and in analogous fractions from normal sera. None of the proteins were detected in media of cultured fibroblasts from either genotype. Since the same proteins and protein fragments were identified in both CF and normal plasma fractions, and were not detected in CF fibroblast media, it appears that none of these proteins can be identified as the CFCI. Identification of these proteins will permit further purification of the CFCI by immunochemical methods.

Animals↗

PubMed1994

Transmissibility of Pseudomonas cepacia infection in clinic patients and lung-transplant recipients with cystic fibrosis.

BACKGROUND: In patients with cystic fibrosis, infection with Pseudomonas cepacia is associated with poor outcomes. However, the extent of person-to-person transmission and the source of P. cepacia infection after lung transplantation are not well defined. Using DNA-based typing systems, we sought to determine the genetic relatedness of P. cepacia infection at one cystic fibrosis center. METHODS: We analyzed 65 P. cepacia isolates gathered over a period of eight years at a single cystic fibrosis center from 17 clinic patients and from 5 patients who underwent double-lung transplantation. The isolates were analyzed by ribotyping and chromosomal fingerprinting based on pulsed-field gel electrophoresis. RESULTS: Analyses of serial isolates revealed that each clinic patient and transplant recipient harbored a different P. cepacia clone that was persistent. In the transplant recipients, the preoperative and postoperative isolates were identical. In the two patients with disseminated infection after lung transplantation, isolates from multiple sites were identical and indicated clonal expansion of the previous respiratory P. cepacia strain. Pulsed-field gel electrophoresis proved both more discriminative and more practical than ribotyping as a means of defining the genetic relatedness of the P. cepacia isolates. CONCLUSIONS: Our serial analyses in patients with cystic fibrosis at one center found distinct strains of P. cepacia persistently infecting each patient and no evidence of person-to-person transmission of this organism. P. cepacia infection after lung transplantation was due to the persistence of the strain present before transplantation.

Bacterial Typing Techniques↗

PubMed1990

Conversion of Pseudomonas aeruginosa to the phenotype characteristic of strains from patients with cystic fibrosis.

Isolates of Pseudomonas aeruginosa from cystic fibrosis patients are unusual; they are often susceptible to the bactericidal effect of human serum, have a rough lipopolysaccharide, and produce an exopolysaccharide that is responsible for the characteristic mucoid phenotype. In contrast, strains from the environment and from patients with other diseases usually have smooth lipopolysaccharide, do not produce very much mucoid exopolysaccharide, and are phenotypically nonmucoid. The predominance of mucoid strains of P. aeruginosa in infections of patients with cystic fibrosis has not been explained. In the lower airways, where P. aeruginosa persists in cystic fibrosis, nutrients for bacterial growth may be limited. We investigated whether growth of P. aeruginosa under conditions of suboptimal nutrition causes conversion to the characteristic cystic fibrosis phenotype. Ninety-two strains of P. aeruginosa were maintained for up to 90 days in a minimal medium with acetamide as the sole carbon source. In 56 (52%) of 107 cultures, isolates with rough lipopolysaccharide emerged, and in 20 (19%) of 104 nonmucoid cultures, mucoid isolates were recovered. Strains with rough lipopolysaccharide also were sensitive to the bactericidal effect of normal human serum. Under conditions of suboptimal nutrition in vitro, isolates of P. aeruginosa emerged that produced rough lipopolysaccharide and were mucoid, typical of many isolates from cystic fibrosis patients. This peculiar phenotype may arise as a consequence of nutritional limitation within the cystic fibrosis respiratory tract rather than from features unique to these strains of bacteria.

Blood Bactericidal Activity↗

PubMed2002

Peripheral muscle strength in young males with cystic fibrosis.

BACKGROUND: In children with cystic fibrosis there is a decrease in peak work capacity and oxygen consumption on maximal exercise testing when compared to controls. Previous studies have shown that peripheral muscle force is decreased in children with cystic fibrosis even in those with minimal changes in lung function. However, no studies have examined peripheral muscle strength using isokinetic dynamometry which permits measurement of muscle strength throughout range and is considered the gold standard in orthopaedics and sports medicine. METHODS: Isokinetic muscle strength was measured in the knee flexors and extensors and shoulder flexors and extensors at two speeds of movement in children with cystic fibrosis and matched controls. Activity levels in both groups were calculated. RESULTS: Thirteen subjects and 13 age and height matched controls were assessed. Average peak torque was calculated and expressed in terms of body weight. There was a significant difference in peak torque/body weight in children with cystic fibrosis when compared to controls. FEV1 was significantly correlated with knee muscle strength and shoulder flexion at 90 degrees /s in subjects with CF. CONCLUSION: Children with CF had lower muscle strength than control subjects. Airflow limitation was associated with decreased muscle strength. The relationship between muscle strength and exercise tolerance requires investigation.

Adolescent↗

PubMed1995

New treatment modalities for cystic fibrosis.

Refinements in standard therapy for cystic fibrosis have led to dramatic increases in survival and quality of life over the past three decades. Standard therapy has consisted of oral and intravenous antibiotics, chest percussion with postural drainage, and aerosol bronchodilator therapy. The discovery of the cystic fibrosis gene and elucidation of the underlying biochemical defect have broadened our understanding of the pathophysiology of cystic fibrosis and provided a rationale for many new and innovative therapies. Modulation of airway epithelial ion transport may improve mucociliary clearance and delay colonization by infective organisms. Anti-inflammatory therapy may decrease lung injury that results from the host's attempt to limit airway infection. Supplementation of airway antiproteases may limit the destructive effects of unopposed proteases on pulmonary architecture. Genetic biotechnology has already produced agents that preserve pulmonary function and decrease infectious exacerbations by altering the viscoelastic properties of sputum from patients with cystic fibrosis. Both active and passive immunotherapy are currently being investigated as a measure to delay or combat endobronchial infection with Pseudomonas spp. Aerosolized aminoglycoside antibiotics are being increasingly employed to control pulmonary infection while minimizing systemic toxicity. These treatment modalities, combined with the prospects for gene therapy, provide a brighter outlook for the patient with cystic fibrosis than ever before.

Cystic Fibrosis↗

PubMed2000

Energy supplements rich in linoleic acid improve body weight and essential fatty acid status of cystic fibrosis patients.

BACKGROUND: Patients with cystic fibrosis who have steatorrhea frequently are underweight and have essential fatty acid (EFA) depletion, which is associated with a poor clinical course. It has been stated that poor EFA status is difficult to correct in patients with cystic fibrosis, and an impaired EFA metabolism with reduced synthesis of long-chain polyunsaturated fatty acids has been proposed. In this study, the effects of an oral energy supplement rich in linoleic acid were investigated in patients with cystic fibrosis who had a body weight below 95% of normal for height. METHODS: Thirty-six patients (16 girls) more than 4 years of age were randomized either to a control group (n = 20, age 13.3 +/- 3.8 years, mean +/- SD) receiving intensive dietary counseling only, or an intervention group (n = 16, age, 10.4 +/- 4.3 years) treated for 3 months with dietary counseling plus 628 +/- 254 mL (= kcal) per day of an energy supplement rich in fat (31% of energy) and linoleic acid (16% of energy). RESULTS: In contrast to the control group, the patients with supplemented diets achieved significant increases of energy intake (2189 +/- 731 kcal/day vs. 2733 +/- 762 kcal/day), weight for height (82.8% +/- 8.6% vs. 84.8% +/- 9.6% of normal), and body fat (5.1 +/- 1.7 kg vs. 5.8 +/- 2.2 kg) as well as the initially low values of plasma phospholipid linoleic acid (11.8% +/- 1.1% vs. 17.6% +/- 1.6% of total phospholipid fatty acids) and its main metabolite arachidonic acid (4.4% +/- 0.4% vs. 5.9% +/- 0.3%). CONCLUSIONS: Patients with cystic fibrosis with low body weight and poor EFA status benefit from EFA-rich energy supplements and can synthesize arachidonic acid from the precursor linoleic acid.

Adolescent↗

PubMed1983

Autonomic nervous system abnormalities in cystic fibrosis.

The basic defect in cystic fibrosis, the most common lethal genetic diseases of white Americans, is unknown, but the character of the generalized exocrinopathy suggests some disorder of the regulation and control of the process of glandular secretion. Definite abnormalities in all branches of the autonomic nervous system have been demonstrated in patients with cystic fibrosis, including increased sensitivity to alpha-adrenergically stimulated pupillary dilation; increased responsiveness to cholinergic stimulation of pupillary constriction, parotid saliva secretion, and eccrine sweat secretion; and decreased responsiveness to beta-adrenergic stimulation of the cardiovascular system as well as circulating lymphocytes and granulocytes. Since these abnormalities also occur in asymptomatic heterozygotes for cystic fibrosis (parents of patients), they are likely to be inherited characteristics and not secondarily acquired. This constellation of inherited autonomic abnormalities--alpha-adrenergic and cholinergic hyperresponsiveness and beta-adrenergic resistance--may contribute to the pathophysiology of cystic fibrosis and may also be an important clue to the nature of the basic defect.

Animals↗

PubMed1999

Fas and Fas ligand expression in cystic fibrosis airway epithelium.

BACKGROUND: Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and defective expression of CFTR protein in epithelial cells. The main cause of mortality in CF is linked to chronic inflammatory and infectious airway processes. Recent studies have suggested perturbations in the apoptotic process in CF cell lines and enterocytes. A study was undertaken to investigate the expression of Fas and Fas ligand (FasL) in CF bronchial epithelium and CF tracheal cell lines. METHODS: Immunohistochemical staining for Fas (alkaline phosphatase anti-alkaline phosphatase) and FasL (immunoperoxidase) was performed in eight CF bronchial epithelial samples and four controls and immunohistochemical DNA fragmentation (TUNEL) was carried out in four CF patients and four controls. Immunofluorescence staining and flow cytometric analysis of Fas and FasL expression was performed in two human tracheal epithelial cell lines (HTEC) with normal and CF genotype. The dosage of serum soluble FasL was examined in 21 patients with CF and 14 healthy volunteers. RESULTS: FasL expression was markedly increased in patients with CF in both the ciliated and submucosal glandular bronchial epithelium compared with controls; Fas was similarly expressed in bronchial samples from controls and CF patients in both the ciliated epithelium and submucosal glands. High levels of DNA fragmentation were observed in CF but with some epithelial cell alterations. Serum concentrations of soluble FasL were frequently undetectable in patients with CF. In vitro, HTEC expressed Fas and FasL in both genotypes. A higher mean fluorescence intensity for FasL expression was noted in CF genotype HTEC with median (range) for six experiments of 74 (25-101) for CF cells and 42 (21-70) for non-CF cells. CONCLUSION: Fas/FasL interaction is probably implicated in the human CF airway apoptotic pathway. The mechanisms of induction of FasL expression and its role in inducing tissue damage or remodelling or in controlling local inflammatory cell apoptosis remain to be determined.

Adolescent↗

PubMed1996

Reduced renal fractional excretion of lithium in cystic fibrosis.

We hypothesized that patients with cystic fibrosis would have abnormal lithium handling because the genetic defect in cystic fibrosis encodes an ion channel which causes a generalized electrolyte transport disorder in epithelial membranes. Eight patients with cystic fibrosis and eight age-sex matched healthy subjects ingested 600 mg lithium carbonate and had urine and serum lithium levels assessed 24 h later. Compared with healthy subjects, the patients with cystic fibrosis had higher serum lithium levels (0.071 +/- 0.038 vs 0.113 +/- 0.055 mmol l-1, P = 0.03) and had lower fractional renal excretion of lithium (27.5 +/- 14.8 vs 18.8 +/- 9.3%, P = 0.03). Caution should be used in prescribing standard doses of lithium to patients with cystic fibrosis until more definitive data are available.

Adult↗

PubMed1980

Effect of cimetidine and pancreatic enzymes on serum and fecal bile acids and fat absorption in cystic fibrosis.

Steatorrhea persists in most cystic fibrosis patients with exocrine pancreatic insufficiency despite enzyme replacement, perhaps because gastric acid inactivates oral enzymes. Bile acid malabsorption may parallel steatorrhea. We studied the effect of adding cimetidine (300 mg a.c.) to pancreatic enzyme therapy in 8 patients with cystic fibrosis and steatorrhea. Fecal bile acid, weight and fat, and postprandial serum bile acids were measured with and without cimetidine. D-Xylose absorption was normal in all patients. On constant diets, 72-hr stools were collected during enzyme therapy and during a 5-day course of enzymes plus cimetidine. Addition of cimetidine to enzyme decreased fecal weight (257 +/- 32.6 to 198.6 +/- 32.5 g/day), increased the percent of dietary fat absorbed (75.0 +/- 4.9 to 80.1 +/- 4.1%, P less than 0.05), but had no effect on fecal bile acids (4.7 +/- 0.9 to 4.2 +/- 1.0 mmol/m2/day). Compared with no therapy, enzymes increased postprandial serum bile acid at 60 min (9.56 +/- 1.0 to 14.0 +/- 1.3 muM/liter, P less than 0.05) and at 120 min (9.4 +/- 1.2 to 12.4 +/- 1.6 muM/liter, P less than 0.02). The addition of cimetidine to enzymes abolished this postpranidial bile acid rise. In conclusion, addition of cimetidine to oral pancreatic enzyme therapy decreases stool weight and fat but perhaps not stool bile acids in cystic fibrosis. However, correction of fat absorption is incomplete. Enzyme therapy increases postprandial serum bile acids, and this increase is abolished with oral cimetidine. In view of the incomplete correction of steatorrhea and the alterations in serum bile acids induced by cimetidine, further research with this new medication is needed before it can be recommended for routine clinical use in patients with cystic fibrosis.

Adolescent↗

PubMed2003

Congenital absence of vas deferens and cystic fibrosis.

BACKGROUND: Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are a relatively frequent cause of male infertility such as congenital absence of vas deferens. This finding suggests that CFTR could play a significant role in the etiopathogenesis of congenital absence of vas deferens. METHODS: To assess how often CFTR mutations and 5-thymidine variant of the polythymidine tract of intron 8 are detected in congenital absence of vas deferens we selected 35 infertile male adults caused by congenital absence of vas deferens. RESULTS: Frequency of mutations differs significantly from that in the general population (2% vs 40% respectively) and the delta F 508 mutation accounts for 35% of these mutations. Abnormal sweat test resulted in several patients with a mutation than in others and this difference was highly significant. CONCLUSIONS: This result confirms the role of CFTR protein in the pathogenesis of this malformation and suggests that CBAVD phenotype can represent a mild form of cystic fibrosis. Consequently genetic analysis should take into account the presence of an associated mutation and patients with bilateral agenesia and their partners should be screened for cystic fibrosis prior to any in vitro fertilization techniques.

Adult↗

PubMed1992

Immunocytochemical analysis reveals differences between the subcellular localization of normal and delta Phe508 recombinant cystic fibrosis transmembrane conductance regulator.

Cystic fibrosis (CF) is caused by mutations in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR). The most common mutation responsible for CF is the deletion of amino acid residue Phe508, with an average allelic frequency of 70%. We have isolated an anti-CFTR monoclonal antibody which specifically recognizes recombinant normal and delta Phe508-CFTR produced by a vaccinia virus expression system. Immunocytochemical analysis of L cells expressing either normal or delta Phe508-CFTR showed a marked difference in subcellular distribution. Normal CFTR had a distinct localization in the perinuclear area and was also associated with the plasma membrane. delta Phe508-CFTR essentially lacked the membrane-associated distribution and was present throughout the cytoplasm. This heterologous expression system thus provides a model system for studying the subcellular localization of different mutant forms of CFTR.

Animals↗

PubMed2000

Defects in processing and trafficking of the cystic fibrosis transmembrane conductance regulator.

Cystic fibrosis (CF) is caused by inherited mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated chloride channel expressed in epithelial tissues. Most mutations in CF patients result in rapid intracellular degradation of the CFTR protein. While this defect is thought to result from abnormal protein folding, it is unclear how mutant and wild-type (WT) proteins differ in structure, how the cell is able to distinguish these differences, and how the fate of the mutant protein is determined. By examining the initial steps of CFTR assembly into the endoplasmic reticulum (ER) membrane, it has recently been shown that CFTR utilizes two redundant translocation pathways to direct N-terminus folding events. Mutations that block one pathway therefore do not alter transmembrane topology, but rather appear to disrupt intracellular trafficking through perturbations in higher order tertiary structure. These studies suggest that cellular quality control machinery acts at least in part, by monitoring proper interactions between CFTR subdomains. The end result of this process is the conversion of misfolded CFTR into a membrane-bound, polyubiquitinated complex. This complex recruits cytosolic degradation machinery to the endoplasmic reticulum membrane where CFTR is degraded as it is extracted from the lipid bilayer. Understanding how cellular machinery mediates this process will be an important step in designing strategies to modify protein folding and degradation in CF and related ion channelopathies.

Animals↗

PubMed1995

Use of a membrane potential-sensitive probe to assess biological expression of the cystic fibrosis transmembrane conductance regulator.

Cystic fibrosis is caused by defects in a chloride-transporting protein termed cystic fibrosis transmembrane conductance regulator (CFTR). This study presents an innovative procedure to evaluate expression of functional CFTR. The technique uses the potential-sensitive probe bis-(1,3-diethylthiobarbituric acid) trimethine oxonol or DiSBAC2(3), by single-cell fluorescence imaging. The DiSBAC2(3) method was first validated on the mouse mammary tumor cell line C127, stably expressing wild-type CFTR. Activation of protein kinase A by the cAMP-permeable analogue 8-Br-cAMP induced cell membrane depolarization consistent with expression of wild-type CFTR. The DiSBAC2(3) method is quick, simple, and reproducible, and does not require invasive cell loading procedures. The system was then applied to the cell model of the human lung tumor cell line A549, in which exogenous CFTR was expressed by infecting with the replication-deficient recombinant adenovirus AdCFTR. DiSBAC2(3) was able to detect the fraction of cells in which the expression of CFTR protein was confirmed by immunocytochemistry. The DiSBAC2(3) probe was also used in human nasal respiratory cells cultured in vitro, in which it efficiently discriminated between endogenous CFTR in normal and CF cells. Functional evaluation of CFTR function by the described method can be a useful tool to detect the expression of the CF gene transferred by adenoviral vectors for use in gene therapy trials.

Adenoviridae↗

PubMed2006

Changing their minds with time: a comparison of hypothetical and actual reproductive behaviors in parents of children with cystic fibrosis.

OBJECTIVE: Newborn screening for cystic fibrosis, with appropriate counseling, enables carrier parents to be informed early about future reproductive choices. Previous studies have assessed attitudes toward reproductive decisions in a hypothetical pregnancy or have measured reproductive behaviors. We aimed to measure parent attitudes to reproductive technologies and to compare prospectively these attitudes with later reproductive behaviors. METHODS: Parents of children who had cystic fibrosis and were aged 2 to 7 years were surveyed at baseline using a written questionnaire that explored attitudes to prenatal testing and termination of pregnancy in a hypothetical pregnancy. Parent knowledge and access to genetic counseling services also were assessed. Five years later, we compared attitudes with actual reproductive behaviors. RESULTS: Fifty-six mothers participated at baseline, and 43 were resurveyed 5 years later. Parent knowledge of cystic fibrosis and genetics was very good. A total of 93% had met a genetic counselor at the time of diagnosis, and more than half had on at least 1 subsequent occasion. At baseline, 82% reported that they would be likely to have prenatal diagnosis in a subsequent pregnancy, and 56% reported that they would be likely to terminate an affected pregnancy. Twenty-seven mothers since had been pregnant, with prenatal diagnosis used in 33 of the 55 pregnancies. In 67%, the hypothetically reported behavior regarding use of prenatal testing was the same as their actual behavior. Five of the 33 tested pregnancies were affected; all ended in termination. Reproductive choices in relationship to the number of children wanted, together with attitudes toward prenatal diagnosis and termination of pregnancy, were dynamic over time, with decisions having changed in both directions. CONCLUSIONS: This cohort of parents has actively used reproductive technologies since the birth of a child who has cystic fibrosis that was diagnosed by newborn screening. The dynamic aspect of reproductive choices highlights the importance of ongoing access to genetic counseling beyond the initial period of diagnosis and education, regardless of whether parents report that they expect to use reproductive technologies.

Abortion, Induced↗

PubMed1991

Carrier screening for cystic fibrosis: implications for obstetric and gynecologic practice.

Cystic fibrosis, which is one of the most common autosomal recessive disorders, has a carrier frequency of approximately 1 in 25 among whites in the United States. In this population approximately 75% of the mutations in patients with cystic fibrosis correspond to a 3 base pair deletion that results in the loss of a phenylalanine residue at amino acid position 508 (designated delta F508) from the coding region of the cystic fibrosis gene. Currently, only about half of the couples at risk can be identified as cystic fibrosis carriers. We support conclusions of the National Institutes of Health Workshop on Population Screening for the Cystic Fibrosis Gene, which state that carrier testing should be offered to all individuals or couples with a family history of cystic fibrosis. Good science and solid educational and counseling strategies must be in place before screening for cystic fibrosis is routinely offered to those with a negative family history. Pilot programs that investigate research questions in the delivery of population screening for cystic fibrosis carriers are urgently needed.

Advisory Committees↗