Objective: To explore the effects of aerosolized earthworm fibrinolytic enzyme (EFE) on bleomycin-induced pulmonary fibrosis in rats.
Methods: A total of 72 male SD rats were divided randomly into 3 groups of bleomycin (BLM) group with intratracheal BLM (5 mg/kg), control group with the same dose of normal saline, then after both receiving aerosolization of normal saline once daily instead of EFE, EFE group with EFE (2500 U/kg) by aerosolization once daily after BLM instillation. Lung histopathology, immunohistochemistry for transforming growth factor β(1) (TGF-β(1)), lung hydroxyproline contents, levels of urokinase PA (uPA), tissue plasminogen activator (tPA) and PA inhibitor 1 (PAI-1) in lung and blood were observed at Days 7, 14 and 28 of experiment, respectively.
Results: Compared with BLM group, pulmonary fibrosis improved and the TGF-β(1) expression of lung tissue decreased (P < 0.01). Hydroxyproline content of lung tissue decreased in EFE group compared with BLM group ((5.8 ± 2.5) vs (9.6 ± 1.3), (6.7 ± 1.4) vs (9.7 ± 1.5), (7.5 ± 1.2) vs (9.7 ± 1.4) mg/L, P < 0.01). Compared with BLM group, the uPA levels of lung were elevated in EFE group at Days 7 and 14 ((1.04 ± 0.36) vs (0.72 ± 0.11), (0.90 ± 0.09) vs (0.75 ± 0.08) µg/L, P < 0.05). Moreover, the plasma levels uPA of increased at Days 14 and 28 ((0.32 ± 0.04) vs (0.25 ± 0.02), (0.36 ± 0.05) vs (0.28 ± 0.04) µg/L, P < 0.05). Consistently, compared with BLM group, the tPA levels of lung increased in EFE group ((4.70 ± 0.87) vs (3.01 ± 0.62), (5.72 ± 0.37) vs (3.00 ± 0.51), (6.73 ± 1.12) vs (3.18 ± 0.38) µg/L, P < 0.01) and the plasma levels of tPA also increased ((3.40 ± 0.36) vs (1.79 ± 0.38), (3.17 ± 0.37) vs (2.18 ± 0.17), (3.85 ± 0.56) vs (2.80 ± 1.06) µg/L, P < 0.01). However, compared with BLM group, the PAI-1 levels of lung decreased in EFE group ((6.04 ± 0.81) vs (8.52 ± 1.01), (6.78 ± 0.81) vs (9.81 ± 1.73), (7.63 + 0.99) vs (11.44 ± 2.54), P < 0.05) and the plasma levels of PAI-1 also decreased in EFE group ((4.82 ± 0.42) vs (6.89 ± 0.84), (5.73 ± 0.40) vs (7.30 ± 1.09), (5.64 ± 0.87) vs (7.98 ± 1.10) µg/L, P < 0.05).
Conclusions: Earthworm fibrinolytic enzyme may decrease bleomycin-induced pulmonary fibrosis and TGF-β(1) expression while increasing fibrinolytic activation. And fibrinolytic strategies are probably useful for the therapy of fibrotic lung diseases.