Citrus jabara Extracts Suppress MUC5AC Mucin Production in Human Lung Epithelial Cells

In the human airway, the overproduction of MUC5AC mucin is a key feature of allergic asthma, and it induces airway narrowing and obstruction. The production of MUC5AC is regulated by several signals, but the mechanism is not completely understood. We investigated the effect of jabara, a citrus containing abundant flavonoids, on the regulation of MUC5AC production. When NCI-H292 human airway epithelial cells were cultured with jabara extracts, we found that the expression of Periodic acid-schiff stained mucin was suppressed with downregulated MUC5AC production. In human primary airway cells derived from asthmatic patients, MUC5AC production was also suppressed by jabara extracts. The treatment of cells with jabara extracts decreased ERK activation in NCI-H292 and in primary cells. These results show that jabara extracts contain some factors that suppress MUC5AC production and ERK activity and suggest that it will be useful for relieving asthma.