A scientific koan: what is the cause of cystic fibrosis?
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Cystic Fibrosis↗
Biomedical subjects
Bruce K Rubin
Publications and source records attributed to Bruce K Rubin.
Hyperosmolar solutions stimulate mucus secretion in the ferret trachea.
STUDY OBJECTIVES: Inhalation of hypertonic saline or mannitol solutions acutely increases mucociliary clearance. Because increased clearance is often coupled with increased mucus secretion, we hypothesized that hyperosmolar agents would stimulate mucus secretion. SETTING AND SUBJECTS: The isolated tracheae of healthy young adult ferrets were studied in a basic research laboratory. MEASUREMENTS AND RESULTS: We demonstrated that there was a dose-dependent increase in mucin secretion by enzyme-linked lectin assay after incubation with 1.69 g/dL (597 mOsm/L), 3.69 g/dL (1,192 mOsm/L), 5.69 g/dL (1,823 mOsm/L), and 10.69 g/dL (3,612 mOsm/L) of saline solution over Krebs-Henseleit solution control (288 mOsm/L) [p < 0.01 for 1.69 g/dL of saline solution and p < 0.0001 for others]. Mannitol solution, 15 g/dL (1,040 mOsm/L), also significantly increased mucin secretion (n = 4, p < 0.005). There was a 47% and 54% increase in secretion of the serous cell product lysozyme after exposure to 3.69 g/dL (1,192 mOsm/L) and 10.69 g/dL (3,612 mOsm/L) saline solutions, respectively (n = 5, p < 0.05). Secretion was only stimulated when the hyperosmolar exposure was on the luminal side of the epithelium. Mucin secretion was induced within minutes of 3.69 g/dL of saline solution exposure, and this increased mucin secretion quickly peaked. The ratio of mucin to lysozyme secretion was approximately 2. This ratio appeared to be independent of the osmotic concentration of the stimulus and therefore of secretory rate. CONCLUSIONS: Mucus secretion is markedly stimulated in response to hyperosmolarity. This may be a protective response. These results also suggest that the therapeutic use of hyperosmolar aerosols should be evaluated with care when used for patients with mucus hypersecretion and impaired mucus clearance.
Animals↗
A randomized controlled trial of inhaled flunisolide in the management of acute asthma in children.
BACKGROUND: Inhaled corticosteroids (ICS) may provide benefit in the therapy of acute asthma. The purpose of this study was to test the hypothesis that ICS are as effective as oral corticosteroids (OCS) in the management of acute childhood asthma. METHODS: A randomized, masked, placebo-controlled study was conducted in children aged 6 to 16 years seeking emergent care for an acute exacerbation of asthma. Patients were randomized into one of two groups: group 1 (OCS), oral prednisone, 2 mg/kg (maximum of 60 mg/d) for 7 days, and placebo pressurized metered-dose inhaler with valved holding chamber, four inhalations bid; and group 2 (ICS), flunisolide, four inhalations (1 mg) bid for 7 days, and daily placebo tablets. Spirometry (FEV(1)) was performed at baseline, day 3, and day 7 of the study. A symptom diary and twice-daily peak expiratory flow were recorded. RESULTS: A total of 58 subjects receiving ICS (n = 27) or OCS (n = 28) were enrolled. Baseline asthma severity, race, gender, and age were balanced between the two groups. chi(2) showed no significant difference in symptom severity between the two groups at any time during the study. FEV(1) percentage of predicted was lower in the ICS group on day 3 (65% vs 78%, p = 0.03) and on day 7 (77% vs 95%, p = 0.002). CONCLUSION: ICS were found to be useful in the management of acute asthma in children; however, spirometry data suggested a more rapid resolution of asthma with OCS.
Acute Disease↗
Pharmacological approaches to discovery and development of new mucolytic agents.
Airway mucus is the secretory product of the mucous cells; it is a variable mixture of water, mucous glycoproteins, low molecular weight ions, proteins, and lipids, whose physical properties are important for airway defense. The factors that contribute to the physical properties of mucus are complex, and there are a number of pharmacological strategies that can potentially serve to improve the clearability of airway mucus. Novel mucoactive approaches include strategies for mucoregulation--decreasing the abnormal volume of mucus secretion--and medications designed to improve the cough clearability of airway secretions. In vitro results suggest potential benefits from the additive effects of selected combinations of mucoactive medications. Further studies are required to confirm these findings, to perform direct assessments of mucus clearability, and to extend the observations to patients with various types of pulmonary diseases where mucoactive treatments are required.
Cystic Fibrosis↗
Acute renal failure in cystic fibrosis: association with inhaled tobramycin therapy.
We describe a 20-year-old patient with cystic fibrosis who developed acute nonoliguric renal failure associated with inhaled tobramycin. Clinical evaluation and renal biopsy findings were consistent with aminoglycoside-induced changes. Renal failure due to inhaled aminoglycosides has not been previously reported. The incidence may rise, however, with the increased use of this treatment modality. Measurable tobramycin levels due to inhalational therapy with conventional dosing in the reported patient indicate that the drug can be systemically absorbed, and renal tubular toxicity may occur.
Acute Kidney Injury↗
Physiology of airway mucus clearance.
Respiratory tract secretions consist of mucus, surfactant, and periciliary fluid. The airway surface fluid is present as a bilayer, with a superficial gel or mucous layer and a layer of periciliary fluid interposed between the mucous layer and the epithelium. A thin layer of surfactant separates the mucous and periciliary fluid layers. The mucous layer extends from the intermediate airway to the upper airway and is approximately 2-10 microm thick in the trachea. Airway mucus is the secretory product of the goblet cells and the submucosal glands. It is a nonhomogeneous, adhesive, viscoelastic gel composed of water, carbohydrates, proteins, and lipids. In health, the mucous gel is primarily composed of a 3-dimensional tangled polymer network of mucous glycoproteins or mucin. Mucin macromolecules are 70-80% carbohydrate, 20% protein, and 1-2% sulfate bound to oligosaccharide side chains. The protein backbones of mucins are encoded by mucin genes (MUC genes), at least 8 of which are expressed in the respiratory tract, although MUC5AC and MUC5B are the 2 principal gel-forming mucins secreted in the airway. Mucus is transported from the lower respiratory tract into the pharynx by air flow and mucociliary clearance. Expectorated sputum is composed of lower respiratory tract secretions along with nasopharyngeal and oropharyngeal secretions, cellular debris, and microorganisms. Disruption of normal secretion or mucociliary clearance impairs pulmonary function and lung defense and increases risk of infection. When there is extensive ciliary damage and mucus hypersecretion, airflow-dependent mucus clearance such as cough becomes critically important for airway hygiene.
Cough↗
The pharmacologic approach to airway clearance: mucoactive agents.
The airway mucosa responds to infection and inflammation in a variety of ways. This response often includes surface mucous (goblet) cell and submucosal gland hyperplasia and hypertrophy, with mucus hypersecretion. Products of inflammation, including neutrophil-derived deoxyribonucleic acid (DNA) and filamentous actin (F-actin), effete cells, bacteria, and cell debris, all contribute to mucus purulence and, when this mucus is expectorated it is called sputum. Mucoactive medications are intended to serve one of 2 purposes; either to increase the ability to expectorate sputum or to decrease mucus hypersecretion. Mucoactive medications have been classified according to their proposed mechanisms of action. Increased knowledge of the properties of mucus has given us tools to better understand the mechanisms of airway disease and mucoactive therapy. Expectorants are thought to increase the volume or hydration of airway secretions. Systemic hydration and classic expectorants have not been demonstrated to be clinically effective. Modifiers of airway water transport are being clinically investigated as expectorants. Mucolytics degrade polymers in secretions. The classic mucolytics have free thiol groups to degrade mucin. Peptide mucolytics break pathologic filaments of neutrophil-derived DNA and actin in sputum. Nondestructive mucolysis includes mucin dispersion by means of charge shielding. Mucokinetics are medications that increase mucociliary efficiency or cough efficiency. Cough flow can be increased by bronchodilators in patients with airway hyperreactivity. Abhesives such as surfactants decrease mucus attachment to the cilia and epithelium, augmenting both cough and mucociliary clearance. Mucoregulatory agents reduce the volume of airway mucus secretion and appear to be especially effective in hypersecretory states such as bronchorrhea, diffuse panbronchiolitis, and some forms of asthma. Mucoregulatory agents include anti-inflammatory agents (indomethacin, glucocorticosteroids), anticholinergic agents, and some macrolide antibiotics. Classifying mucoactive agents should help us to develop and evaluate new types of therapy and to better direct therapy toward the patients who are most likely to benefit.
Anti-Bacterial Agents↗
Nebulizer therapy for children: the device-patient interface.
A therapeutic aerosol benefits the patient only if the medication deposits in the airway. Advances in nebulizer design have made them more efficient and "user friendly," but the greatest problem with administering aerosolized medication continues to be educating patients and caregivers to use aerosol devices properly and consistently. Misuse and nonuse are the greatest impediments to effective aerosol delivery. The respiratory pattern and degree of patient cooperation also profoundly affect aerosol deposition, and those effects are greatly magnified in small children. There are many misconceptions about nebulizer use and nebulizer equipment, even in teaching hospitals, and these can have serious consequences when patients do not receive the medication they need. This review discusses how airway physiology, nebulizer technology, and patient education relate to appropriate nebulizer use. Education is critically important, but unfortunately it is often a misunderstood or neglected part of aerosol administration.
Administration, Inhalation↗