Abstract: Objective To investigate the damage effect of fine particulate matter(PM2.5)exposure on mucociliary clearance, and analyze the effect of myrtol standardized on it. Methods Rats were divided into control group(group N),PM2.5 exposure group(group PM) and myrtol standardized group(group PM+CS).Rats were respectively given inhalation to filtered clean air indoor, exposure to ambient air of Shijiazhuang city (the range of PM2.5 concentration from 29.90 mg/m³ to 99.65 mg/m³) and gavage of myrtol standardized suspension 300 mg/(kg·d).Eight rats in each group were sacrificed after 3 months and 6 months.The lung and tracheal tissues were stained with HE and AB-PAS.The ultrastructure of cilia was observed by scanning electron microscope.The number of total cells,neutrophil count and classification in the BALF were detected by microscopy.The gene expression level of MUC5AC and AQP5 in pulmonary tissue were measured by real-time PCR. The protein expressional level of MUC5AC in lung tissue was respectively measured by immunohistochemistry and Western blot. Results In the PM groups, inflammatory injury and myxocyte metaplasia of lung and tracheal tissues were obvious, and tracheal cilia were adhesive, lodging and absent, sparse and disordered.The total number of white blood cells and percentage of neutrophils in BALF were significantly higher than those in N groups(P＜0.05).The expression of MUC5AC mRNA and MUC5AC protein in PM groups was higher than that in N groups(P＜0.05),but the relative expression of AQP5 mRNA in PM groups was significantly lower than that in N groups(P＜0.05).Compared with PM group, myrtol standardized can reduce the above damage effect(P＜0.05). Conclusions Myrtol standardized can protect the mucociliary clearance system in rats by reducing the damage of cilia structure, hypersecretion of mucus and inflammatory damage caused by PM2.5.

Key words: PM2.5, myrtol standardized, MCC, MUC5AC, AQP5