Molecular and functional changes of pulmonary surfactant in response to hyperoxia.

Surfactant comprises phosphatidylcholine (PC) together with anionic phospholipids, neutral lipids, and surfactant proteins SP-A to-D. Its composition is highly specific, with dipalmitoyl-PC, palmitoyl-myristoyl-PC, and palmitoyl-palmitoleoyl-PC as its predominant PC species, but with low polyunsaturated phospholipids. Changes in pulmonary metabolism and function in response to injuries depend on their duration and whether adaptation can occur. We examined in rats prolonged (7 days) versus acute (2 days) exposure to non-lethal oxygen concentrations (85%) with respect to the composition and metabolism of individual lung phospholipid molecular species. Progressive inflammation, structural alteration, and involvement of type II pneumocytes were confirmed by augmented bromodeoxyuridine incorporation, broadening of alveolar septa, and increased granulocyte, macrophage, SP-A, and SP-D concentrations. Surfactant function was impaired after 2 days, but normalized with duration of hyperoxia, which was attributable to inhibition but not to alteration in SP-B/C concentrations. Phospholipid pool sizes and PC synthesis by lung tissue, as assessed by [methyl-(3)H]-choline incorporation, were unchanged after 2 days, although after 7 days they were elevated 1.7-fold. By contrast, incorporation of labeled PC into tissue pools of surfactant and lung lavage fluid decreased progressively. Moreover, concentrations of arachidonic acid containing phospholipids were augmented at the expense of saturated palmitoyl-myristoyl-PC and dipalmitoyl-PC. We conclude a persisting impairment in the intracellular trafficking and secretion of newly synthesized PC, accompanied by a progressive increase in alveolar arachidonic acid containing phospholipids in spite of recovery of acutely impaired surfactant function and adaptive increase of overall PC synthesis.

Long term azithromycin therapy in cystic fibrosis patients: a study on drug levels and sputum properties.

BACKGROUND: Following reports on the treatment of diffuse panbronchiolitis (DPB), recent studies demonstrate that long term therapy with azithromycin (AZM) is effective in cystic fibrosis (CF) patients. However, the underlying mechanisms remain uncertain. Some macrolides, including AZM, display inhibition of virulence factors and other antipseudomonal effects at subinhibitory levels in vitro. OBJECTIVES: Drug doses used for CF and DPB therapy were investigated to determine whether they achieve corresponding sputum drug levels in CF patients in vivo. METHODS: In an open, prospective study, 14 CF patients with chronic Pseudomonas aeruginosa airway infection received 250 mg AZM either daily ('high dose') or twice weekly ('low dose') for 12 weeks. Viscoelasticity of sputum was assessed by magnetic microrheology. RESULTS: AZM accumulated in sputum by two orders of magnitude over a period of four weeks. In the following steady state, median AZM concentrations in sputum were 9.5 microg/mL (0.6 to 79.3 microg/mL, interquartiles 1.4 to 33.4 microg/mL) and 0.5 microg/mL (range less than 0.1 [below detection level] to 5.2 microg/mL, interquartiles 0.2 to 1.4 microg/mL) in the high and low dose groups, respectively. Viscoelasticity improved in all patients but one. CONCLUSIONS: The findings suggest that antipseudomonal activity has to be considered among the potential mechanisms of macrolide therapy. Further, viscoelasticity may be a valuable parameter in future clinical trials.

Cystic fibrosis transmembrane conductance regulator (CFTR)-mediated residual chloride secretion does not protect against early chronic Pseudomonas aeruginosa infection in F508del homozygous cystic fibrosis patients.

Cystic fibrosis (CF) disease severity is characterized by a broad variability that has been attributed, in addition to the CF transmembrane conductance regulator (CFTR) genotype, to modulating factors such as CFTR-mediated residual chloride (Cl-) secretion. Moreover, CFTR has been suggested to function as a receptor for Pseudomonas aeruginosa (PA). In this study, we investigated whether or not the presence of residual Cl- secretion protects against early chronic PA colonization of patients' airways. Excluding influences on the phenotype caused by different CFTR mutations, we evaluated a cohort of F508del homozygous individuals with respect to the correlation between residual Cl- secretion and the age of onset of PA colonization as an important marker of clinical phenotype. A group with early chronic PA colonization before the age of 7 y (n = 14) was compared with a cohort that had no initial PA detection at least until the age of 13 y (n = 10). We determined the Cl- transport properties by using the intestinal current measurement in rectal suction biopsies. Residual Cl- secretion, most likely due to the CFTR Cl- channel, was observed in 63% of subjects, more frequently in early chronically PA colonized than among late or not colonized patients. These results demonstrate the presence of some active F508del-CFTR in the apical cell membrane and imply that factors other than the CFTR-mediated residual Cl- secretion determine the age of onset of PA colonization.

Phosphatidylcholine metabolism of rat trachea in relation to lung parenchyma and surfactant.

Pulmonary surfactant prevents alveolar collapse and contributes to airway patency by reducing surface tension. Although alveolar surfactant, consisting mainly of phospholipids (PL) together with neutral lipids and surfactant-specific proteins, originates from type II pneumocytes, the contribution of airway epithelia to the PL fraction of conductive airway surfactant is still debated. We, therefore, analyzed the composition, synthesis, and release of phosphatidylcholine (PC) molecular species as the main surfactant PL of the rat trachea compared with the lung. Analyses of individual PC molecular species with HPLC and electrospray ionization mass spectrometry revealed that the rat trachea contained and synthesized much more palmitoyloleoyl-PC, palmitoyllinoleoyl-PC, and palmitoylarachidonoyl-PC, together with increased amounts of alkylacyl-PC, and less surfactant-specific species such as dipalmitoyl-PC than the lung. Organ cultures with [methyl-3H]choline as precursor of PC revealed that, in the trachea, synthesized PC was retained in the tissue, rather than secreted. [Methyl-3H]choline-labeled dipalmitoyl-PC was a negligible component in the trachea, and, in contrast to the lungs, palmitoyloleoyl-PC was enriched in tracheal secretions. We conclude that the surfactant fraction in the airways does not originate from the airways but is produced in the alveolar space and transported upward.

Cost of care and clinical condition in paediatric cystic fibrosis patients.

BACKGROUND: The clinical course of cystic fibrosis (CF) shows considerable variation resulting in differences in health care utilisation. We investigated important clinical parameters and their relation to costs. METHODS: We collected clinical parameters together with health care utilisation of a representative paediatric CF population (n=138 patients) attending Hanover Medical School over a period of 1 year. 49% of the patients were chronically infected with Pseudomonas aeruginosa. Costs were calculated on the basis of the annual individual health care utilisation from the perspective of health insurance. RESULTS: Total annual expenditure per patient amounted to 23,989 euro (S.D. 18,026), with home drug treatment representing the most important single cost factor (47% of total costs). While costs rose with age and doubled in the first 18 years, they correlated foremost with P. aeruginosa airway colonisation status and lung function expressed as FEV(1). Costs of patients with chronic P. aeruginosa infection were more than three times higher than of uninfected patients. CONCLUSIONS: Health care expenditures for patients with CF vary with the clinical course. The variation can be explained to a large extend by clinical parameters.