Cystic fibrosis: leakage of lysosomal enzymes and of alkaline phosphatase into the extracellular space

Nine lysosomal enzymes and alkaline phosphatase have been assayed with two different ultramicro techniques in the intra- and extracellular space of fibroblast cultures derived from the skin of cystic fibrosis patients, cystic fibrosis carriers, and normal controls, respectively. Evidence has been obtained for a multiple leakage of lysosomal enzymes and of alkaline phosphatase into the medium of fibroblast cultures from cystic fibrosis patients and carriers. The situation is comparable to a certain extent, to that observed in I-cell-disease (mucolipidosis II). This multiple leakage results in the decrease of intracellular activity of several lysosomal enzymes in cultures from cystic fibrosis patients and carriers and due to the coordinate regulation of the synthesis of the “leaky enzymes” in an overshooting of the intracellular alkaline phosphatase activity in cultures from cystic fibrosis patients. It also explains the retarded catabolism of certain molecules, such as the Tamm-Horsfall glycoprotein, in cystic fibrosis cells. It is speculated that the basic defect in cystic fibrosis leads to abnormal recognition sites on lysosomal enzymes and on alkaline phosphatase, and in consequence to the leakage of these enzymes into the extracellular space. The present findings allow one to develop methods for the pre- and postnatal diagnosis of cystic fibrosis with cell cultures, and for the detection of cystic fibrosis carriers with the peripheral blood.     

Accumulation of ceramide in the trachea and intestine of cystic fibrosis mice causes inflammation and cell death

Cystic fibrosis is a hereditary metabolic disorder caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene and characterized by severe intestinal and pulmonary symptoms, in particular intestinal obstruction, pancreatic insufficiency, chronic pulmonary inflammation, and microbial lung infections. Recent studies have demonstrated an accumulation of ceramide in the lungs of cystic fibrosis patients and in several mouse models. These findings showed that pulmonary ceramide concentrations play an important role in pulmonary inflammation and infection. In this study we investigated whether ceramide concentrations are also altered in the trachea and the intestine of cystic fibrosis mice and whether an accumulation of ceramide in these organs has functional consequences that are typical of cystic fibrosis. Our findings demonstrate a marked accumulation of ceramide in tracheal and intestinal epithelial cells of cystic fibrosis mice. When acid sphingomyelinase activity is inhibited by treating cystic fibrosis mice with amitriptyline or by genetic heterozygosity of acid sphingomyelinase in cystic fibrosis mice, ceramide concentrations in the trachea and the intestine are normalized. Moreover, increased rates of cell death and increased cytokine concentrations in the trachea, the intestine, or both were normalized by the inhibition of acid sphingomyelinase activity and the concomitant normalization of ceramide concentrations. These findings suggest that ceramide plays a crucial role in inflammation and increased rates of cell death in several organs of cystic fibrosis mice.     

Interdomain interactions within the gene 3 protein of filamentous phage

A number of disorders related to cystic fibrosis have been described since the cloning of the cystic fibrosis gene, including infertility due to the congenital bilateral absence of the vas deferens. We have identified, in several patients, complex cystic fibrosis transmembrane conductance regulator genotypes like double-mutant alleles. We have now analyzed the structure-function relationships of one of these mutants, R74W-D1270N cystic fibrosis transmembrane conductance regulator, expressed in HeLa cells, to evaluate the contribution of each mutation in the phenotype. We found that R74W cystic fibrosis transmembrane conductance regulator appears to be a polymorphism, while D1270N cystic fibrosis transmembrane conductance regulator could be responsible for the congenital bilateral absence of the vas deferens phenotype. The combination of the two produced a more severe effect on the chloride conductance pathway as well as on the phenotype.     

Cloning the mouse homolog of the human cystic fibrosis transmembrane conductance regulator gene.

The cystic fibrosis transmembrane conductance regulator is encoded by the gene known to be mutated in patients with cystic fibrosis. This paper reports the cloning and sequencing of cDNAs for the murine homolog of the human cystic fibrosis transmembrane conductance regulator gene. A clone that, by analogy to the human sequence, extends 3' from exon 9 to the poly(A) tail was isolated from a mouse lung cDNA library. cDNA clones containing exons 4 and 6b were also isolated and sequenced, but the remainder of the mRNA proved difficult to obtain by conventional cDNA library screening. Sequences spanning exons 1-9 were cloned by PCR from mouse RNA. The deduced mouse protein sequence is 78% identical to the human cystic fibrosis transmembrane regulator, with higher conservation in the transmembrane and nucleotide-binding domains. Amino acid sequences in which known cystic fibrosis missense mutations occur are conserved between man and mouse; in particular, the predicted mouse protein has a phenylalanine residue corresponding to that deleted in the most common human cystic fibrosis mutation (delta F508), which should allow the use of transgenic strategies to introduce this mutation in attempts to create a "cystic fibrosis mouse".     

Serum Binding of Calcium and the Red Cell Membrane in Cystic Fibrosis

THERE is evidence for a factor in the serum of cystic fibrosis patients which may play a role in the pathological manifestation of the genetic syndrome: serum of patients with cystic fibrosis alters the cilia movement of rabbit trachea in vitro¹ and of oyster cilia². This activity is apparently associated with the immunoglobulin fraction^3,4. Balfe et al.⁵ reported a modification of sodium flux in red cells obtained from patients with cystic fibrosis. In the course of searching for evidence of interaction of serum with red cells in cystic fibrosis, we found that there is a substantial increase in serum calcium binding in patients with cystic fibrosis. This seems to be associated with a modified membrane protein electrophoretic pattern of cystic fibrosis red cells in specified experimental conditions.     

CYSTIC FIBROSIS

To determine the actual number of deaths from cystic fibrosis reported in 1957 in California, all death certificates mentioning any one of the various terms used to describe the condition were reviewed.As a cause of death, cystic fibrosis is infrequently mentioned on death certificates. In 1957, only 42 of a total of 124,082 death certificates mentioned cystic fibrosis. Half of the deaths occurred in persons less than 12 months of age. There was no significant difference by sex between deaths due to cystic fibrosis and deaths from all causes. All deaths occurred in the white population.     

Serum pancreatic lipase activity in cystic fibrosis.

Patients with cystic fibrosis have been found to have abnormal serum concentrations of immunoreactive trypsin and abnormal activities of pancreatic isoamylase. A study was undertaken to discover whether activity of pancreatic lipase is also altered in cystic fibrosis. Serum from 23 patients with cystic fibrosis was assayed for immunoreactive trypsin and pancreatic lipase. Median serum pancreatic lipase activity was significantly lower in patients with cystic fibrosis than in controls, as was immunoreactive trypsin concentration (p less than 0.0001). Some patients had supranormal lipase concentrations but these were not always associated with absence of malabsorption. Serum pancreatic lipase activity is considerably changed in cystic fibrosis.     

Differential concanavalin A binding of cystic fibrosis and normal liver alpha-L-fucosidase.

A novel technique has been employed to demonstrate that α-L-fucosidase purified from cystic fibrosis and control livers exhibits differential binding to the lectin Concanavalin A. The concentration of α-CH₃-mannoside necessary to prevent 50% binding of α-L-fucosidase to Concanavalin A is considerably lower for the cystic fibrosis enzyme (13.5 vs. 33.3 mM). Comparable results were found when binding studies were done on crude supernatant α-L-fucosidase from 8 cystic fibrosis and 8 control livers (5.6 ± 0.4 mM and 13.2 ± 3.4 mM, respectively), without any overlap of values between the cystic fibrosis and control livers. These results suggest that comparative lectin binding studies on cystic fibrosis and normal glycoproteins from readily available tissues might result in an assay for detecting the cystic fibrosis genotype.     

Demographic and social characteristics of adults with cystic fibrosis in the United Kingdom.

OBJECTIVE--To obtain information about social and demographic characteristics and lifestyle of adult patients with cystic fibrosis, including those who do not attend major specialist clinics. DESIGN--Confidential self completion postal questionnaire to adult patients with cystic fibrosis, asking about social and demographic characteristics, social class and occupation, employment, education, insurance and social security benefits, symptom severity, and medical care. SETTING--National association for adults with cystic fibrosis. SUBJECTS--1052 adult members of the Association of Cystic Fibrosis Adults UK, accounting for 68% of those with cystic fibrosis in the United Kingdom population over 16 years of age and over 80% of those over 25 in June 1990. RESULTS--The response rate was 82% (397 women, 423 men). Most adults with cystic fibrosis were found to be living fulfilling lives into adulthood. Significantly fewer men were married or cohabiting than women (110 (26%) men, 175 (44%) women). 420 (55%) responders were working, and of these 235 (56%) had less than two weeks'' sick leave a year. Half of those not employed gave ill health as the reason. Revealing that they had cystic fibrosis at job interviews reduced likelihood of being employed for those with mild to moderate disease. People with cystic fibrosis had been less successful than the general population in achieving O level or equivalent qualifications, but more successful in achieving A level or higher qualifications. Achievement of any qualifications enhanced employment prospects irrespective of disease severity. CONCLUSION--Contrary to an image of chronic ill health and disability, a high proportion of adults with cystic fibrosis are living full and productive lives.     

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.     

Characterization of alpha 2-macroglobulin from plasma of cystic fibrosis patients and controls

The physical, kinetic, and isoelectric focusing properties of native alpha 2-macroglobulin from cystic fibrosis and control plasmas were studied. No differences were found in the esterolytic activity levels of control, obligate heterozygote, and cystic fibrosis plasmas. Stability studies indicated that both control and cystic fibrosis alpha 2-macroglobulin retained full activity for at least 8 months at -20 degrees C, a week at 0-4 degrees C, 11 hr at 50 degrees C, and showed no differences in thermostability at several preincubation temperatures. The microheterogeneity of native alpha 2-macroglobulin was studied by column isoelectric focusing of five control and five cystic fibrosis plasmas. The number and pI values of the isoelectric forms between pH 4.5-8.0 were quite similar for both groups even though consistently less cystic fibrosis alpha 2-macroglobulin activity was recovered after isoelectric focusing.     

Controlled trial of serum isoelectric focusing in the detection of the cystic fibrosis gene

Summary Three independent observers assessed the discriminating power of serum isoelectric focusing in detecting the presence of the cystic fibrosis gene. On the basis of average scores, four out of 23 cystic fibrosis patients, six out of 22 heterozygotes, and three out of 16 controls were misclassified. However, the mean scores for the cystic fibrosis and heterozygote groups were significantly different to that for the control group. It is concluded that isoelectric focusing is insufficiently reliable to be used for diagnosis or heterozygote detection in cystic fibrosis, but that it does provide evidence for the presence of a protein associated with the mutant gene.     

Identification of 'cystic fibrosis protein' as a complex of two calcium-binding proteins present in human cells of myeloid origin

Cystic fibrosis protein is a serum protein characterized by a pI close to 8.4 and present with a higher concentration in serum and plasma of cystic fibrosis carriers than in controls. This protein was found immunologically indistinguishable from the cystic fibrosis antigen isolated from granulocytes and presenting a sequence analogous to that of MRP-8, a calcium-binding protein expressed in the myeloid cell lineage. Using antibodies directed against MRP-8 and its closely associated calcium-binding protein, MRP-14, we demonstrate here that cystic fibrosis protein purified from serum is a complex of the two proteins MRP-8 and MRP-14.     

The role of calmodulin in the regulation of (Mg + Ca)-ATPase activity in erythrocyte membranes of cystic fibrosis patients and controls

(Mg²⁺ + Ca²⁺)-ATPase activity has been found to be significantly reduced in EDTA-washed erythrocyte membrane preparations from cystic fibrosis patients compared to aged-matched controls. Calmodulin was found to be present in erythrocytes from cystic fibrosis patients and characterized similarly to calmodulin isolated from control preparations. Calmodulin from control erythrocyte preparations stimulated the (Mg²⁺ + Ca²⁺)-ATPase activity of EDTA-washed erythrocyte membranes derived from cystic fibrosis patients to the same extent as those membranes derived from controls. Similarly, calmodulin obtained from erythrocytes of cystic fibrosis patients stimulated the (Mg²⁺ + Ca²⁺)-ATPase activity of control and cystic fibrosis erythrocyte membrane preparations to a similar extent. These results indicate that this decrease in (Mg²⁺ + Ca²⁺)-ATPase activity in erythrocytes from cystic fibrosis patients is not due to an alteration in the regulatory function of calmodulin.     

Hyperacidification of cellubrevin endocytic compartments and defective endosomal recycling in cystic fibrosis respiratory epithelial cells.

The cystic fibrosis transmembrane conductance regulator (CFTR), which is aberrant in patients with cystic fibrosis, normally functions both as a chloride channel and as a pleiotropic regulator of other ion transporters. Here we show, by ratiometric imaging with luminally exposed pH-sensitive green fluorescent protein, that CFTR affects the pH of cellubrevin-labeled endosomal organelles resulting in hyperacidification of these compartments in cystic fibrosis lung epithelial cells. The excessive acidification of intracellular organelles was corrected with low concentrations of weak base. Studies with proton ATPase and sodium channel inhibitors showed that the increased acidification was dependent on proton pump activity and sodium transport. These observations implicate sodium efflux in the pH homeostasis of a subset of endocytic organelles and indicate that a dysfunctional CFTR in cystic fibrosis leads to organellar hyperacidification in lung epithelial cells because of a loss of CFTR inhibitory effects on sodium transport. Furthermore, recycling of transferrin receptor was altered in CFTR mutant cells, suggesting a previously unrecognized cellular defect in cystic fibrosis, which may have functional consequences for the receptors on the plasma membrane or within endosomal compartments.     

Neonatal screening for cystic fibrosis using immunoreactive trypsinogen and direct gene analysis: four years' experience.

OBJECTIVE--To assess the performance and impact of a two tier neonatal screening programme for cystic fibrosis based on an initial estimation of immunoreactive trypsinogen followed by direct gene analysis. DESIGN--Four year prospective study of two tier screening strategy. First tier: immunoreactive trypsinogen measured in dried blood spot samples from neonates aged 3-5 days. Second tier: direct gene analysis of cystic fibrosis mutations (delta F508, delta I506, G551D, G542X, and R553X) in samples with immunoreactive trypsinogen concentrations in highest 1% and in all neonates with meconium ileus or family history of cystic fibrosis. SETTING--South Australian Neonatal Screening Programme, Adelaide. SUBJECTS--All 88,752 neonates born in South Australia between December 1989 and December 1993. INTERVENTIONS--Neonates with two identifiable mutations were referred directly for clinical assessment and confirmatory sweat test; infants with only one identifiable mutation were recalled for sweat test at age 3-4 weeks. Parents of neonates identified as carriers of cystic fibrosis mutation were counselled and offered genetic testing. MAIN OUTCOME MEASURES--Identification of all children with cystic fibrosis in the screened population. RESULTS--Of 1004 (1.13%) neonates with immunoreactive trypsinogen > or = 99th centile, 912 (90.8%) had no identifiable mutation. 23 neonates were homozygotes or compound heterozygotes; 69 carried one identifiable mutation, of whom six had positive sweat tests. Median age at clinical assessment for the 29 neonates with cystic fibrosis was 3 weeks; six had meconium ileus and two had affected siblings. 63 neonates were identified as carriers of a cystic fibrosis mutation. Extra laboratory costs for measuring immunoreactive trypsinogen and direct gene analysis were $A1.50 per neonate screened. CONCLUSION--This strategy results in early and accurate diagnosis of cystic fibrosis and performs better than screening strategies based on immunoreactive trypsinogen measurement alone.     

Electron paramagnetic resonance spectroscopy as a monitor of the pathway of the thermal unfolding of ribonuclease A.

α-L-Fucosidase activity is elevated in skin fibroblasts from cystic fibrosis patients when compared to controls. The activities of nine other acid hydrolases including neuraminidase are similar in cystic fibrosis and control fibroblasts. The relationship of these results to the recent finding of a decreased activity of α-L-fucosidase in the serum of cystic fibrosis patients is discussed. It is proposed that an abnormal distribution of α-L-fucosidase is involved in the pathogenesis of this disease.     

The high lipid content of respiratory mucins in cystic fibrosis is related to infection

Seven human bronchial mucins secreted by patients suffering from chronic bronchitis or from cystic fibrosis were prepared by exclusion from a Sepharose CL-2B column in 6 M guanidinium chloride. Their behaviour in CsBr density gradient centrifugation was compared. The mucin fractions were associated with peptides and lipids, the abundance of which decreases with the buoyant density. The lipid content of the mucin fractions appears to be related to the infectious character of the bronchial secretion and seems to be independent of cystic fibrosis. The content of fatty acids remaining after delipidation of mucin fractions from patients with chronic bronchitis or with cystic fibrosis also appears to be related more to the purulent character of the sputum than to cystic fibrosis or chronic bronchitis.     

The role of calmodulin in the regulation of (Mg2+ + Ca2+)-ATPase activity in erythrocyte membranes of cystic fibrosis patients and controls

(Mg²⁺ + Ca²⁺)-ATPase activity has been found to be significantly reduced in EDTA-washed erythrocyte membrane preparations from cystic fibrosis patients compared to aged-matched controls. Calmodulin was found to be present in erythrocytes from cystic fibrosis patients and characterized similarly to calmodulin isolated from control preparations. Calmodulin from control erythrocyte preparations stimulated the (Mg²⁺ + Ca²⁺)-ATPase activity of EDTA-washed erythrocyte membranes derived from cystic fibrosis patients to the same extent as those membranes derived from controls. Similarly, calmodulin obtained from erythrocytes of cystic fibrosis patients stimulated the (Mg²⁺ + Ca²⁺)-ATPase activity of control and cystic fibrosis erythrocyte membrane preparations to a similar extent. These results indicate that this decrease in (Mg²⁺ + Ca²⁺)-ATPase activity in erythrocytes from cystic fibrosis patients is not due to an alteration in the regulatory function of calmodulin.     

Patterns of polymorphism and linkage disequilibrium for cystic fibrosis

Four polymorphic markers that map within 80 kb of an HTF island which is genetically very close to the cystic fibrosis locus have been identified. We have analyzed the linkage disequilibrium between each of these markers and the cystic fibrosis mutation in 89 families from four European countries, Denmark, Finland, Spain, and Great Britain. Strong linkage disequilibrium between three polymorphic sites and cystic fibrosis was observed. The markers on the J3.11 (D7S8) side of the HTF island show stronger disequilibrium than those on the met side. Linkage disequilibrium between markers and disease alters the probability that a person of a given haplotype is a carrier in some populations and helps to identify regions of a sequence that are most likely to contain the cystic fibrosis mutation.