Objective To investigate the antagonistic effects of different doses of Lianhua Qingwen on pulmonary injury induced by fine particulates PM2.5 in rats. Methods Fine particulates suspended in the environment were collected. Forty-eight healthy adult wistar rats were randomly divided into 6 groups with 8 rats in each group. Four groups of rats were exposed to PM2.5 by intratracheally dripping suspensions of fine particulates PM2.5 (7.5 mg/kg) as dust-exposed model rats. Among them 24 rats in three groups received Lianhua Qingwen treatment (crude drug) at a dose of 2 g/kg, 4 g/kg, 8 g/kg per day for 3 days before dust exposure and were defined as low-dose, middle-dose and high-dose Lianhua Qingwen treatment groups respectively. The other dust-exposed model rats without treatment were assigned as PM2.5 control group. The un-exposed rats were set as saline control group (1.5 ml/kg saline) and blank control group. All rats were killed after 24 hours of the exposure. Lung tissue, serum and bronchoalveolar lavage fluid (BALF) were collected. The levels of malonaldehyde (MDA), lactate dehydrogenase (LDH), and glutathione peroxidase (GSH-PX) in blood serum and BALF, and superoxide dismutase (SOD) in blood surum were measured using fluorescent quantitation PCR; Expression of NF-E2-related factor 2(NRF-2), heme oxygenase 1 (HO-1) and quinone oxidoreductase 1 (NQO1) in lung tissues were measured using Western blot. Pathological changes of lung tissues in each group were also examined. Results Pathology revealed thickened alveolar septum, congestion of capillary, interstitial edema and infiltration of lymphocyte and neutrophil surrounding bronchiole in the PM2.5 control group, which were significantly relieved in the Lianhua Qingwen treatment groups. Compared to the blank and saline control groups, the PM2.5 control group had significantly higher levels of LDH and MDA (p<0.01) and lower level of GSH-PS (p<0.01) in BALF, significantly higher levels of LDH and MDA (p<0.05) and lower level of GSH-PS (p<0.05) in rat serum. The levels of MDA in blood serum and BALF were significantly lower in each treatment group than that in PM2.5 control group (all P<0.05). In both middle-dose and high-dose treatment group the measurements of LDH in serum and BALF as well as GSH-PX in serum were significant difference from those of PM2.5 control group (all P<0.05). Expressions of NRF-2, HO-1 and NQO1 in lung tissues were significantly different among middle-dose and high-dose treatment group compared with those in PM2.5 control group (all P<0.05). Conclusion Fine particulates PM2.5 in environment may induce pulmonary oxidative lesions in rats. Middle-dose and high-dose Lianhua Qingwen has antagonist effece on the injuries induced by fine particulates.

Key words: fine particulates (PM2.5), pulmonary lesion, oxidative stress, Lianhua Qingwen, rats