The GCC repeat length in the 5'UTR of MRP1 gene is polymorphic: a functional characterization of its relevance for cystic fibrosis

BACKGROUND: Among the members of the ATP binding cassette transporter superfamily, MRPs share the closest homology with the CFTR protein, which is defective in CF disease. MRP1 has been proposed as a potential modifier gene and/or as novel target for pharmacotherapy of CF to explain the clinical benefits observed in some CF patients treated with the macrolide AZM. The 5'UTR of the MRP1 gene contains a GCC triplet repeat that could represent a polymorphic site and affect the activity of the promoter. METHODS: The MRP1 5' flanking region was amplified by PCR from 36 CF patients and 100 non-CF subjects and the number of GCC triplets of each allele was determined by sequence and electrophoretic analysis. We performed gene reporter studies in CF airway epithelial cells 16HBE14o-AS3, in basal conditions and in the presence of AZM. RESULTS: We found that the GCC repeat is polymorphic, ranging from 7 to 14 triplets either in CF or in non-CF subjects. Our data are preliminary and have to be confirmed on a larger population of CF subjects. The transcriptional activity of the proximal MRP1 5' regulatory region revealed no statistically significant correlations between the number of repeats and treatment with AZM. CONCLUSION: We identified a novel polymorphism in the 5'UTR of MRP1 gene that provides multiple alleles in a gene relevant for multidrug resistance as well as for CF, determining that this region is transcriptionally active and that this activity does not appear to be influenced by AZM treatment

Azithromycin reduces spontaneous and induced inflammation in ΔF508 cystic fibrosis mice

BACKGROUND: Inflammation plays a critical role in lung disease development and progression in cystic fibrosis. Azithromycin is used for the treatment of cystic fibrosis lung disease, although its mechanisms of action are poorly understood. We tested the hypothesis that azithromycin modulates lung inflammation in cystic fibrosis mice. METHODS: We monitored cellular and molecular inflammatory markers in lungs of cystic fibrosis mutant mice homozygous for the ΔF508 mutation and their littermate controls, either in baseline conditions or after induction of acute inflammation by intratracheal instillation of lipopolysaccharide from Pseudomonas aeruginosa, which would be independent of interactions of bacteria with epithelial cells. The effect of azithromycin pretreatment (10 mg/kg/day) given by oral administration for 4 weeks was evaluated. RESULTS: In naive cystic fibrosis mice, a spontaneous lung inflammation was observed, characterized by macrophage and neutrophil infiltration, and increased intra-luminal content of the pro-inflammatory cytokine macrophage inflammatory protein-2. After induced inflammation, cystic fibrosis mice combined exaggerated cellular infiltration and lower anti-inflammatory interleukin-10 production. In cystic fibrosis mice, azithromycin attenuated cellular infiltration in both baseline and induced inflammatory condition, and inhibited cytokine (tumor necrosis factor-α and macrophage inflammatory protein-2) release in lipopolysaccharide-induced inflammation. CONCLUSION: Our findings further support the concept that inflammatory responses are upregulated in cystic fibrosis. Azithromycin reduces some lung inflammation outcome measures in cystic fibrosis mice. We postulate that some of the benefits of azithromycin treatment in cystic fibrosis patients are due to modulation of lung inflammation

Cystic fibrosis patients, infertile men, and their noses.

The paper is an editorial on the role of nasal investigation in the diagnosis of cistic fibrosis

Nasal potential difference in cystic fibrosis patients presenting borderline sweat test

The diagnosis of cystic fibrosis (CF) can be difficult if the sweat test and routine deoxyribonucleic acid (DNA) analysis are inconclusive. Under these circumstances, measurement of nasal potential difference (NPD) was proposed as a complementary diagnostic tool, as demonstrated in subjects bearing the G551S or 3849+10KbC-->T mutations. The purpose of the present study was to verify the diagnostic value of this technique in CF patients with a borderline sweat test. NPD was measured in 18 patients with a borderline sweat test, in whom CF diagnosis was based on the presence of one CF gene mutation in each chromosome (CF borderline). These patients were compared both to non-CF controls and CF patients with an abnormal sweat test (CF controls). Basal NPD values of CF borderline patients (mean value -39+/-6 mV, range -29 to -52 mV; n=18) were in the pathological range of CF controls (-39+/-8 mV, range -28 to -57 mV; n=37), and both were statistically different from values obtained in non-CF controls (-15+/-4 mV, range -6 to -23 mV; n=24; pT mutation in this group of CF borderline patients (positive in 14 out of 18 subjects), whereas other mutations, such as AF508, Q552X, N1303K and R1162X, were also found to be associated with this atypical CF phenotype. These results confirm the presence of pathological values of basal NPD in CF patients with borderline sweat test, and also extend this finding to subjects bearing genotypes other than the G551S and 3849+10KbC-->T mutations. The present findings, therefore, confirm the usefulness of measurement of basal nasal potential difference in all those patients in whom diagnosis of cystic fibrosis can be suspected but the sweat test remains inconclusive

Nasal potential difference in cystic fibrosis patients presenting borderline sweat test

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