Nonsense-mediated mRNA decay affects nonsense transcript levels and governs response of cystic fibrosis patients to gentamicin.

Aminoglycosides can readthrough premature termination codons (PTCs), permitting translation of full-length proteins. Previously we have found variable efficiency of readthrough in response to the aminoglycoside gentamicin among cystic fibrosis (CF) patients, all carrying the W1282X nonsense mutation. Here we demonstrate that there are patients in whom the level of CF transmembrane conductance regulator (CFTR) nonsense transcripts is markedly reduced, while in others it is significantly higher. Response to gentamicin was found only in patients with the higher level. We further investigated the possibility that the nonsense-mediated mRNA decay (NMD) might vary among cells and hence governs the level of nonsense transcripts available for readthrough. Our results demonstrate differences in NMD efficiency of CFTR transcripts carrying the W1282X mutation among different epithelial cell lines derived from the same tissue. Variability was also found for 5 physiologic NMD substrates, RPL3, SC35 1.6 kb, SC35 1.7 kb, ASNS, and CARS. Importantly, our results demonstrate the existence of cells in which NMD of all transcripts was efficient and others in which the NMD was less efficient. Downregulation of NMD in cells carrying the W1282X mutation increased the level of CFTR nonsense transcripts and enhanced the CFTR chloride channel activity in response to gentamicin. Together our results suggest that the efficiency of NMD might vary and hence have an important role in governing the response to treatments aiming to promote readthrough of PTCs in many genetic diseases.

A single dose of dexamethasone to prevent postbronchoscopy fever in children: a randomized placebo-controlled trial.

STUDY OBJECTIVE: To assess the effectiveness of one dose of dexamethasone (0.5 mg/kg; maximum, 10 mg) to prevent fever after bronchoscopy with BAL. DESIGN: Randomized, placebo-controlled study. PATIENTS: Immunocompetent nonfebrile children undergoing fiberoptic bronchoscopy with BAL. MEASUREMENTS AND RESULTS: Sixty-nine children were included in the study. Thirty-eight children received saline solution, and 31 children received dexamethasone. The two groups were similar regarding the number of children < 2 years old, the percentage of abnormal bronchoscopic findings, the number of positive BAL culture findings, and the index of lipid-laden macrophages. Twenty-six children (68%) in the saline solution group (SG) had fever, compared to 3 children (9.6%) in the dexamethasone group (DG) [p < 0.001]. Fever after the procedure appeared later (12.3 +/- 5.5 h) in the DG compared to 5.4 +/- 2.7 h in the SG. CONCLUSIONS: One dose of dexamethasone administered prior to performing bronchoscopy with BAL may prevent fever subsequent to the procedure. Further studies are necessary in order to determine the optimal dosing regimen for dexamethasone when used for this purpose.

Rate and place of death from asthma among different ethnic groups in Israel: national trends 1980 to 1997.

STUDY OBJECTIVES: To compare the trends of asthma mortality and place of death in young patients (ages 5 to 34 years) from different major population groups in Israel. DESIGN: Retrospective study. PATIENTS AND PARTICIPANTS: Patients who died from asthma between the years 1980 and 1997 according to the death record of the National Israeli Health Registry. RESULTS: During the period studied, 100 asthma mortality cases were reported, which yields a mean mortality rate of 0.226 per 100,000 population. There were no significant changes in the mortality rates over the years. The mean (+/- SD) age of death was 23 +/- 7 years. Of this population, 84.5% were Jews and 15.5% were Arabs, which is proportionate to the general Israeli population. In 52% of the cases, the patients died outside a hospital. There was no significant difference in the place of death between Jews and Arabs. Significantly more men (62.5%) than women (40%) died outside the hospital (p = 0.025). CONCLUSIONS: The asthma mortality rate in Israel during the years 1980 to 1997 was low and stable. Most of the patients still died outside the hospital. There was no difference in the asthma death rate and place of death between Jews and Arabs, suggesting that in our population genetic predisposition is not likely to be a risk factor for mortality.

[Cystic fibrosis from the exocrine pancreatic point of view].

Cystic fibrosis (CF) is the most common life-limiting autosomal recessive genetic disorder in Caucasians and is characterized by a wide variability of clinical expression. The vast majority of patients with CF have pancreatic insufficiency (PI) requiring exogenous pancreatic enzyme replacement therapy with meals. It is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a protein that functions as a chloride channel and is regulated by cAMP. CFTR gene mutations may be classified as severe or mild with respect to pancreatic function status. Patients homozygous for two severe mutations experience severe clinical presentation including PI. Patients carrying at least one mild mutation are considered to be pancreatic sufficient (PS) and carry an overall prognosis that is vastly superior to CF patients with PI. Thus mild mutations appear to be dominant, providing enough functional CFTR to avoid PI. Five general mechanisms have been proposed which describe how CFTR gene mutations influence CFTR-mediated chloride secretion. Classes 1, 2, and 3. that confer little or no chloride channel function, confer the PI phenotype. In contrast, classes 4 and 5 allow CFTR residual function, that are expected to confer the less severe PS phenotype. Recent advances in mutation detection technology and the demonstration of characteristic abnormalities in trans-epithelial potential difference measurements, have expanded the spectrum of diseases associated with the CFTR mutant genes, and paradoxically, in some ways complicated rather than simplified CF diagnosis. Until new diagnostic criteria is conclusively determined, CF diagnosis should be made on clinical rather than laboratory grounds.

Adrenal suppression in asthmatic children receiving low-dose inhaled budesonide: comparison between dry powder inhaler and pressurized metered-dose inhaler attached to a spacer.

BACKGROUND: Dry powder inhalers (DPI) have in recent years become a common mode for administration of inhaled corticosteroids for preventive therapy of asthma. Inhaled steroids delivered by DPI achieve increased lung deposition compared with pressurized metered-dose inhalers (pMDI), which is associated with increased therapeutic effect. This may be associated with increased systemic absorption. OBJECTIVE: The purpose of this study was to evaluate the prevalence of adrenal suppression in children using low-dose budesonide given by DPI, as compared with pMDI attached to a large-volume spacer device (pMDI + spacer). METHODS: In an open-labeled crossover study, 15 asthmatic children aged 5 to 15 years received 200 microg of inhaled budesonide twice daily by DPI (Turbuhaler, Astra, Draco AB, Lund, Sweden) and by pMDI + spacer, 1 month each, in a randomized order. Twenty-four-hour urine collections were performed at baseline and at the end of each of the 2 months of the study period, and urinary cortisol and creatinine were measured. RESULTS: Baseline urinary cortisol:creatinine was 0.038 +/- 0.012 microg/mg, similar in both groups. After 1 month of DPI therapy, urinary cortisol:creatinine was reduced by 27 +/- 16% to 0.028 +/- 0.012 microg/mg (P = 0.018). Urinary cortisol:creatinine after 1 month of pMDI + spacer therapy was similar to baseline 0.037 +/- 0.019 microg/mg (P = 0.78). CONCLUSIONS: Treatment of asthmatic children with budesonide 400 microg daily given via a DPI for 1 month was associated with hypothalamic-pituitary-adrenal axis suppression. This effect was not observed with the same dose of budesonide administered via pMDI + spacer. This indicates that systemic absorption might be reduced with pMDI + spacer therapy.