Objectives: The proteolytic enzyme serrapeptase (SER) is widely used in clinical practice in Japan. We investigated the effect of SER on sputum properties and symptoms in patients with chronic airway diseases.
Methods: This study was an open-labelled trial with a non-treatment control group. Patients were randomly assigned to oral treatment with (n = 15) and without (n = 14) SER 30 mg/day for 4 weeks. Patients collected sputum samples for about 4 h in the morning on the day the trial began and 4 weeks later. We measured the amount of sputum by weighing. Part of each sputum sample was weighed and then completely dried and reweighed. The percentage solid component, viscosity and elasticity of the sputum were measured. Mucociliary transportability index was measured using ciliated bovine trachea ex vivo. Sputum smears were also prepared to count sputum neutrophils. Patients’ symptoms were assessed by a questionnaire that used a visual analogue scale.
Results: After 4 weeks of SER treatment, sputum weight in the morning, percentage solid component, viscosity and elasticity of sputum, sputum neutrophil count, frequency of coughing and frequency of expectoration significantly decreased. The mean mucociliary transportability index increased from 13.3 ± 1.8 to 24.4 ± 2.5 (P = 0.0103).
Conclusions: SER may exert a beneficial effect on mucus clearance by reducing neutrophil numbers and altering the viscoelasticity of sputum in patients with chronic airway diseases.