Effects of betaine, coumarin and flavonoids on mucin release from cultured hamster tracheal surface epithelial cells.

Betaine, coumarin, hesperidin and kaempferol are the components derived from Lycium chinense, Angelicae decursiva, Poncirus trifoliata and Polygonatum odoratum, respectively. These plants have been used for the treatment of respiratory diseases in oriental medicine and their respective components were reported to have various biological effects. In this study, we investigated whether these natural products affect mucin release from cultured hamster tracheal surface epithelial cells and compared the possible activities of these agents with the inhibitory action on mucin release by poly-L-lysine and the stimulatory action by adenosine triphosphate. Confluent primary hamster tracheal surface epithelial cells were metabolically radiolabeled using (3)H-glucosamine for 24 h and treated for 30 min in the presence of varying concentrations of each agent to assess the effects on (3)H-mucin release. The results were as follows: (i) Coumarin and kaempferol did not affect mucin release significantly; (ii) Betaine and hesperidin increased mucin release at the highest concentration; (iii) Poly-L-lysine inhibited and adenosine triphosphate increased mucin release. We conclude that betaine and hesperidin can increase mucin release by direct acting on airway mucin-secreting cells and suggest these agents be further studied for the possible use as mild expectorants during the treatment of chronic airway diseases.