New tricks for old drugs- praziquantel ameliorates bleomycin-induced pulmonary fibrosis in mice

Abstract

Background: Pulmonary fibrosis is a chronic progressive disease with complex pathogenesis, short median survival time, and high mortality. There are few effective drugs approved for pulmonary fibrosis treatment. This study aimed to evaluate the effect of praziquantel (PZQ) on bleomycin (BLM)-induced pulmonary fibrosis.

Methods: In this study, we investigated the role and mechanisms of PZQ in pulmonary fibrosis in a murine model induced by BLM. Parameters investigated included survival rate, lung histopathology, pulmonary collagen deposition, mRNA expression of key genes involved in pulmonary fibrosis pathogenesis, the activity of fibroblast, and M2/M1 macrophage ratio.

Results: We found that PZQ improved the survival rate of mice and reduced the body weight loss induced by BLM. Histological examination showed that PZQ significantly inhibited the infiltration of inflammatory cells, collagen deposition, and hydroxyproline content in BLM-induced mice. Besides, PZQ reduced the expression of TGF-β and MMP-12 in vivo and inhibited the proliferation of fibroblast induced by TGF-β in vitro. Furthermore, PZQ affected the balance of M2/M1 macrophages.

Conclusions: Our study demonstrated that PZQ could ameliorate BLM-induced pulmonary fibrosis in mice by affecting the balance of M2/M1 macrophages and suppressing the expression of TGF-β and MMP-12. These findings suggest that PZQ may act as an effective anti-fibrotic agent for preventing the progression of pulmonary fibrosis.

Keywords: Collagen deposition; Macrophage polarization; Praziquantel; Pulmonary fibrosis; TGF-β.

Fig. 1

Protective effect of praziquantel on bleomycin-induced pulmonary injury in mice. (A) Animal experimental protocol. (B) Trends in body weight changes among the different groups of mice. (C) PZQ treatment improved the survival rate of mice injected by BLM (P = 0.0472) (n = 15). (D) Ashcroft scores of histological lung sections. (E) Representative histological lung sections stained with HE (bar = 500 μm; bar = 50 μm). All quantification graphs represent mean ± SEM. ***P < 0.001

Fig. 2

PZQ reduces the collagen deposition of BLM-induced lung fibrosis in mice. (A) Representative histological lung sections stained with Masson (bar = 200 μm; bar = 50 μm). (B) Masson scores of histological lung sections. (C) Hydroxyproline levels of lung tissue. (D) Procollagen I mRNA levels of lung tissue. (E) Procollagen III mRNA levels of lung tissue. These experiments were repeated three times. All quantification graphs represent mean ± SEM. *P < 0.05. ***P < 0.001

Fig. 3

PZQ reduces the levels of TGF-β and MMP-12 in BLM-induced lung fibrosis mice. (A) Relative mRNA levels of TGF-β. (B) Relative mRNA levels of MMP-12. (C) Relative mRNA levels of INF-γ. (D) Relative mRNA levels of IL-4. (E) Relative mRNA levels of IL-12. (F) Relative mRNA levels of IL-13. These experiments were repeated three times. All quantification graphs represent mean ± SEM. **P < 0.01. ***P < 0.001

Fig. 4

PZQ suppresses the activity of fibroblast in vitro. (A) OD of mouse lung fibroblasts treated with TGF-β (0, 0.1, 1, 10, 20, 50 ng/ml) measuring by MTT. (B) OD of mouse lung fibroblasts treated with PZQ (0, 0.05, 1, 4, 8, 16, 32 μg/ml) measuring by MTT. (C) OD of mouse lung fibroblasts treated with TGF-β (0, 10 ng/ml) and PZQ (0, 0.01, 0.1, 1, 10 μg/ml) for 48 h measuring by CCK-8. #compared with cells treated without TGF-β or PZQ; *compared with cells only treated with TGF-β. These experiments were repeated three times. All quantification graphs represent mean ± SEM. ##P < 0.01. *P < 0.05. **P < 0.01

Fig. 5

PZQ may protect against BLM-induced lung fibrosis by affecting the polarization of macrophages. (A) The rate of M1 and M2 was evaluated by flow cytometry. (B) The rate of M/total cells in BALF. (C) The rate of M2/M1 in BALF. M: macrophage; M1: type 1 macrophage; M2: type 2 macrophage. These experiments were repeated three times. All quantification graphs represent mean ± SEM. *P < 0.05