2.9. Mice protection and lung lesion assay
Balb/c mice (♂, ♀, 18-19g, 8 weeks old) were purchased from Animal Center of China Three Gorges University (Hubei, China). All mice were exposed to alternating light and dark for 12 hours, and food and water were provided free of charge at the animal center.
The protective effect of AS-IV on mice was observed by simulating IAV infection with poly (I: C) (Yuanye Bio-Technology Co., Ltd, 24939-03-5, Shanghai, China) attack. The mice were randomly divided into normal control group (NC), poly (I: C) group, poly (I: C) + AS-IV (25mg/kg) group, poly (I: C) + AS-IV (50mg/kg) group, and poly (I: C) + DEX (5mg/kg) group (n=6 for each group). Poly (I: C) group and drug therapy groups received poly (I: C) (100 μg/mice, dissolved in 50 μl PBS) nasal drops for 3 days to establish pneumonia mice models, while the NC group received 50 μl of PBS nasal drops for 3 days. Then the mice were given different concentrations of AS-IV, Dexamethasone (DEX, Solarbio, CAS: 50-02-2, purity >98%, Beijing, China), or PBS, administered by intragastric administration every day for 5 days. All the mice on day 6 and sacrificed on day 6, and the lung tissues were harvested and weighed. The lung index was expressed as the ratio of mean lung weights to mean body weights. Finally, the lung tissues of mice in each group were stained with hematoxylin and eosin (H&E). The pathologically. Pathological grading was performed according to the relative degree of lung injury and inflammatory infiltration[26]. The scoring was on a scale from 0 to 4: 0, lung tissue structure is normal, no inflammatory cell infiltration; 1, mild structural abnormalities of lung tissue with or without inflammatory cell infiltration; 2, moderate abnormality of lung tissue structure, no inflammatory cell infiltration; 3, moderate abnormality of lung tissue structure with inflammatory cell infiltration; 4, severe abnormality of lung tissue structure with or without inflammatory cell infiltration.
All operations and experiments were performed in accordance with the principles of the National Guidelines for the Nursing.