BackgroundPrevious observations demonstrate that Cftr-null cells and tissues exhibit alterations in cholesterol processing including perinuclear cholesterol accumulation, increased de novo synthesis, and an increase in plasma membrane cholesterol accessibility compared to wild type controls. The hypothesis of this study is that membrane cholesterol accessibility correlates with CFTR genotype and is in part influenced by de novo cholesterol synthesis.MethodsElectrochemical detection of cholesterol at the plasma membrane is achieved with capillary microelectrodes with a modified platinum coil that accepts covalent attachment of cholesterol oxidase. Modified electrodes absent cholesterol oxidase serves as a baseline control. Cholesterol synthesis is determined by deuterium incorporation into lipids over time. Incorporation into cholesterol specifically is determined by mass spectrometry analysis. All mice used in the study are on a C57Bl/6 background and are between 6 and 8 weeks of age.ResultsMembrane cholesterol measurements are elevated in both R117H and ΔF508 mouse nasal epithelium compared to age-matched sibling wt controls demonstrating a genotype correlation to membrane cholesterol detection. Expression of wt CFTR in CF epithelial cells reverts membrane cholesterol to WT levels further demonstrating the impact of CFTR on these processes. In wt epithelial cell, the addition of the CFTR inhibitors, Gly H101 or CFTRinh-172, for 24 h surprisingly results in an initial drop in membrane cholesterol measurement followed by a rebound at 72 h suggesting a feedback mechanism may be driving the increase in membrane cholesterol. De novo cholesterol synthesis contributes to membrane cholesterol accessibility.ConclusionsThe data in this study suggest that CFTR influences cholesterol trafficking to the plasma membrane, which when depleted, leads to an increase in de novo cholesterol synthesis to restore membrane content.

Background: Dosing of tobramycin solution for inhalation (TSI) in cystic fibrosis (CF) patients was based on single-dose pharmacokinetic studies. This investigation was prompted by evidence of possible antibiotic accumulation in respiratory secretions with repeated dosing. The objectives were to evaluate whether tobramycin accumulates in respiratory secretions with repeated inhalation, compare total and biologically active tobramycin concentrations in CF sputum, and evaluate sputum induction for obtaining secretions for drug concentration assay. Methods: Individuals with CF ‡ 10 years of age were enrolled at the beginning of a course of TSI, 300 mg twice daily for 28 days. Two study visits were conducted, 1-2 days and 24-28 days after initiation of TSI treatment. Induced sputum and expectorated sputum samples were collected for measurement of trough and peak tobramycin concentrations at each visit. Total tobramycin concentrations were measured by high-pressure liquid chromatography and bioactive concentrations by bioassay. Results: Twenty participants completed the study. Trough concentrations were similar at visits 1 and 2, as were peak concentrations. Trough bioactive and total tobramycin concentrations were similar (mean ratio 1.2, 95% CI 0.56, 1.87), but peak bioactive concentrations were significantly lower than peak total concentrations (mean ratio 0.33, 95% CI 0.23, 0.44). Sputum induction was well tolerated. Conclusions: No evidence of significant drug accumulation in respiratory secretions with repeat dosing of TSI was seen. Peak bioactive concentrations, although lower than peak total concentrations, were still generally well within the bactericidal range. Sputum induction as a method for determining airway drug concentrations appears safe and feasible.

Rationale:Yoga has been shown to improve outcomes in patients with asthma but has not been investigated in cystic fibrosis (CF) patients.Methods:This was a prospective pilot study to evaluate the safety of a standardized yoga program among CF patients aged 12 to 25 years. Participants engaged in a 50-minute yoga session twice weekly for 8 weeks conducted by a certified yoga instructor using a standardized program designed to be safe for health-compromised individuals. Yoga sessions were individual to avoid transmission of infections. Primary outcome was safety and tolerability. Secondary outcome measures included respiratory symptoms, the Cystic Fibrosis Quality of Life instrument (CFQ-R), lung function, Ease of Breathing Score (measure of exercise tolerance), and weight.Results:Eleven participants were enrolled, and 10 completed the study. Adherence was very good; the mean (SD) number of sessions completed was 14.2 (1.3) out of 16 sessions. Eight patients reported 25 adverse events. The most common was cough, reported in 7. Two events were possibly related to study procedures: calf pain and headache. There were no significant changes in dyspnea or pain scales. The mean (SD) CFQ-R respiratory domain score increased from screening to end of study: 67.9 (11.4) to 82.1 (9.9), P=.04. There were no significant changes in the other outcome measures.Conclusions:In this pilot study, a standardized 8-week yoga program was safe and well tolerated among adolescent and young adult CF patients with mild to moderate lung disease. This study may be helpful to yoga instructors who are interested in working with CF patients. Larger controlled trials are warranted to determine further benefits.

Ipratropium and magnesium were both often used in children with severe asthma hospitalizations that required continuous albuterol therapy. Magnesium use was associated with unfavorable outcomes, possibly reflecting preferential treatment to patients with more severe cases and differing practices between centers. Given the high prevalence of asthma, wide variations in practice, and the potential to improve outcomes and costs, prospective trials of these adjunctive therapies are needed.