Collagen synthesis and secretion in mouse lung tissue after LPS challenge. (A) ELISA was used to detect PICP contents in mouse BALF to compare the synthesis of pulmonary type I collagen 72 hours after intraperitoneal injection of LPS. (B) Pulmonary collagen secretion and deposition 28 days after application of LPS in mice were quantitatively analyzed with hydroxyproline assay. (C) The mRNA expression of type I procollagen, α-SMA, and TLR4 in mouse lung tissue was detected by real-time PCR. (D) Protein expression of α-SMA and TLR4 were detected using Western blots. Type I procollagen, α-SMA, and TLR4 expression in mouse lung tissue increased significantly 72 hours after LPS challenge and become intensive 4 weeks later. Infection with TLR4-shRNA lentivirus significantly inhibited these changes. BC: blank control group; NC: negative control group; PC: positive control group; TI: TLR4 inhibition group; TI+L: TLR4 inhibition group stimulated with LPS; 3d: specimens were collected 72 hours after LPS (or physiological saline) challenge. 4w: specimens were collected 28 days after LPS (or physiological saline) challenge. Each subgroup contains 6 specimens respectively (n = 6). Results were expressed as mean ± standard deviation indicated with column graph and error bar. Blots were representative of six separate experiments. Statistical significance was defined at p values < 0.05. *: P < 0.05 versus PC; **:P < 0.05 versus TI.