Abstract
Aim:
Plasminogen activator inhibitor-1 (PAI-1) is involved in the progression of pulmonary fibrosis. The present study was undertaken to examine the effects on pulmonary fibrosis of silencing PAI-1 expression with small interfering RNA (siRNA) and to assess the possible underlying mechanisms.
Methods:
Male Wistar rats were subjected to intratracheal injection of bleomycin (BLM, 5 mg/kg, 0.2 mL) to induce pulmonary fibrosis. Histopathological changes of lung tissue were examined with HE or Masson's trichrome staining. The expression levels of α-smooth muscle actin (α-SMA), collagen type-I and type-III, caspase-3, as well as p-ERK1/2 and PI3K/Akt in the lung tissue were evaluated using imunohistochemistry and Western blot analyses. The fibroblasts isolated from BLM-induced fibrotic lung tissue were cultured and transfected with pcDNA-PAI-1 or PAI-1siRNA. The expression level of PAI-1 in the fibroblasts was measured using real time RT-PCR and Western blot analysis. The fibroblast proliferation was evaluated using MTT assay.
Results:
Intratracheal injection of PAI-1-siRNA (7.5 nmoL/0.2 mL) significantly alleviated alveolitis and collagen deposition, reduced the expression of PAI-1, α-SMA, collagen type-I and collagen type-III, and increased the expression of caspase-3 in BLM-induced fibrotic lung tissue. In consistence with the in vivo results, the proliferation of the cultured fibroblasts from BLM-induced fibrotic lung tissue was inhibited by transfection with PAI-1-siRNA, and accelerated by overexpression of PAI-1 by transfection with pcDNA-PAI-1. The expression of caspase-3 was increased as a result of PAI-1 siRNA transfection, and decreased after transfection with pcDNA-PAI-1. In addition, the levels of p-ERK1/2 and PI3K/Akt in the fibrogenic lung tissue were reduced after treatment with PAI-1siRNA.
Conclusion:
The data demonstrate that PAI-1 siRNA inhibits alveolitis and pulmonary fibrosis in BLM-treated rats via inhibiting the proliferation and promoting the apoptosis of fibroblasts. Suppression ERK and AKT signalling pathways might have at least partly contributed to this process. Targeting PAI-1 is a promising therapeutic strategy for pulmonary fibrosis.
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Acknowledgements
We gratefully acknowledge Dr Fang WANG for providing the plasmid pcDNA-PAI-1 and the vector pcDNA3.1; Dr Wen-xin WU and Cui-qing MA for their technical assistance; and Madam Li-Mei LIU for her assistance with the writing.
This work was funded by the National Natural Science Foundation of China (No: 30770738; No: 31040036; No: 81000477), the Key Base Research Project of Hebei Province (No: 11966121D), and the Natural Science Foundation of Hebei Province (No: C2009001161).
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Zhang, Yp., Li, Wb., Wang, Wl. et al. siRNA against plasminogen activator inhibitor-1 ameliorates bleomycin-induced lung fibrosis in rats. Acta Pharmacol Sin 33, 897–908 (2012). https://doi.org/10.1038/aps.2012.39
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DOI: https://doi.org/10.1038/aps.2012.39
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