siRNA against plasminogen activator inhibitor-1 ameliorates bleomycin-induced lung fibrosis in rats

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 immunohistochemistry and Western blot analysis. The fibroblasts isolated from BLM-induced fibrotic lung tissue were cultured and transfected with pcDNA-PAI-1 or PAI-1 siRNA. 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-1 siRNA.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.

Plasminogen Activator Inhibitor-1 Suppresses Profibrotic Responses in Fibroblasts from Fibrotic Lungs

“…We (12,13,15) and others (28) have demonstrated that mitigation of ATII cell apoptosis occurs via inhibition of PAI-1, which is otherwise induced during fibrosing lung injury. These observations support the contention that the well established pro-fibrogenic effect of increased PAI-1-mediated ATII cell apoptosis can be prevented by the protection of ATII cells during lung injury using PAI-1 inhibitors (siRNA or chemical inhibitors), as reported by multiple laboratories, including ours (12,13,15,19,28,56,57). The role of PAI-1 in the regulation of fibroblast expansion, viability, and matrix deposition has been less well studied in the context of fibrosing lung injury, which is a basis for this report.…”

Role of irbesartan in protection against pulmonary toxicity induced by bleomycin in rats

“…Importantly, clinical data demonstrated a reduction in plasma levels of PAI-1 which was observed after 4 weeks of irbesartan therapy in patients with metabolic syndrome [31]. Additionally, the progression of pulmonary fibrosis induced by BLM in rats was attenuated by administration of PAI-1 small interfering RNA [32]. Therefore, PAI-1 is an important factor attributed in lung fibrosis.…”

Hybrid pulmonary surfactant-coated nanogels mediate efficient in vivo delivery of siRNA to murine alveolar macrophages

“…The benefit of a delivery vehicle for pulmonary administration of siRNA has been a subject of controversial discussion. In different pre-clinical models, a successful delivery in the respiratory tract of siRNA in the absence of a nanocarrier has been documented [33][34][35]. Moreover, promising results were obtained upon inhalation of free siRNA in human clinical trials for the treatment of patients infected with respiratory syncytial virus [36].…”