Investigating Mucinase Activity in Airway Disease

Accumulation of mucus in the airway involves the process of overproduction and reduced clearance of mucin glycoproteins. To date, little attention has been focused on mechanisms of mucin clearance from the airway. We hypothesize that there is enzymatic degradation of mucins ("mucinase activity") in the airway, which acts to break down mucins and facilitate their clearance. We further hypothesize that glycosidases function as mucinases by removing peripheral monosaccharides from oligosaccharides, including oligosaccharides on mucins. Removal of terminal or capping sugars on mucin side chains may be an important mechanism in mucin degradation and clearance from the lung. If mucinase activity exists in the airway then mucus collected from human subjects should demonstrate evidence of mucin degradation ex vivo, especially at 37º celsius. As part of our protocol we propose to examine changes in airway mucus ex vivo under different experimental conditions. Our primary readout will be measures of sputum rheology, namely viscosity and elasticity. Our consultant for this methodology will be Dr Susan Muller (Chemical Engineering, University of California, Berkeley). In order to conduct experimental studies in this way we will need multiple samples from the same subjects. Thus, up to 10 or more sputum samples per subject will be collected on different days. In addition, we are interested in the biochemical properties of sputum and saliva, specifically the composition of mucin molecules found in these fluids.

Inclusion criteria

Asthma:

• Male and female subjects aged 18 - 70 years
• Medical history consistent with asthma
• PC20 (provocative concentration causing a 20% fall) methacholine ≤ 8 mg/ml for subjects not taking inhaled corticosteroids
• PC20 methacholine ≤ 16 mg/ml for subjects taking inhaled corticosteroids
• Ability to provide informed consent

Cystic Fibrosis:

• Male and female subjects aged 18-55 years
• Prior diagnosis of cystic fibrosis
• Ability to provide informed consent

Healthy:

• Male and female subjects aged 18-70 years
• No current smoking history
• No history of asthma or allergic rhinitis
• FEV1 (forced expiratory volume in 1 second) > 80% predicted
• Ability to provide informed consent

Exclusion criteria

• Recent heart attack or stroke
• Known aortic or cerebral aneurysm
• Uncontrolled hypertension
• Pregnancy
• Lactation
• Lung disease other than asthma,cystic fibrosis, or chronic obstructive pulmonary disease (COPD)/emphysema/chronic bronchitis
• Upper- or lower-respiratory tract infection 6 weeks prior to study enrollment
• Significant asthma exacerbation 6 weeks prior to study enrollment
• Increasing hyposensitization therapy for the past 3 months