2.1. Induction of COPD in rats

Sixteen male SD rats (6–8 weeks, purchased from SLAC, Shanghai, China) were used. The animal experiment protocols were approved and in compliance with the guidelines for animal research of Cangzhou Central Hospital. The rats were randomly divided into the control group (i.e. normal group) and the model group (i.e. COPD group). To induce COPS, the rats were challenged with intratracheal lipopolysaccharide (LPS, 100 μg dissolved in 0.5 ml of PBS) as described in reference (Zhang et al., 2003). Control animals were challenged with 0.5 ml of PBS. At 3 days after challenge, the rats were sacrificed to collect lung tissues and whole blood samples. Plasma were separated and stored at −20 °C for subsequent assays. For each rat, left lung tissue was fixed and used for histopathological tests; right lung tissue was stored in −80 °C and used for RNA and protein extraction.