Abstract: Objective To investigate the inhibitory effect of limonin on airway inflammation and mucus hypersecretion. Methods The experiment was divided into three groups (n=10), namely blank control group, PM2.5 group (the rat models of chronic airway inflammation were established by aerosolized PM2.5 suspension ) and PM2.5+limonin group (intervening with the extract from tangerine peel). The levels of mRNA and protein of inflammatory cytokines, mucin (MUC) and TAS2Rs were measured by ELISA, RT-PCR and Western blot respectively. Results The mRNA and protein expression levels of IL-1β, CINC-1 and MUC5AC and MUC5B in PM2.5 group were significantly higher than those in control group (P<0.05), and then the expression of MUC5AC protein in broncho alveolar lavage fluid (BALF) was increased. Compared with PM2.5 stimulated group, the levels of mRNA and protein of TAS2R14 in PM2.5+limonin intervented group was significantly higher (P<0.05). Moreover, the expression of IL-1β, CINC-1 and MUC5AC, MUC5B was lower than PM2.5 group (P<0.05).While the expression of MUC5B was mainly increased in BALF. Conclusions The production of mucin can been inhibited by aerosolized limonin, meanwhile the secretion of mucin also can be promoted.This effect is achieved by activating the expression of TAS2Rs in the lungs, which enhances the anti-inflammatory effect of airway inflammation.

Key words: mucus hypersecretion, bitter taste receptor, mucin, inflammatory cytokine, limonin