Objective To explore the protective effect of herb pair Kuxingren (Armeniacae Semen Amarum)-Kushen (Sophorae Flavescentis Radix) on bleomycin-induced idiopathic pulmonary fibrosis (IPF) in rats and investigate its mechanism. Methods SD rats were randomly divided into control group, model group, pirfenidone (200 mg/kg) group, Armeniacae Semen Amarum-Sophorae Flavescentis Radix low-, medium-and high-dose (1, 2, 4 g/kg) groups. The IPF rat model was established by one-time tracheal instillation of bleomycin sulfate (5 mg/kg). After drug intervention, the pathological changes in lung tissue were observed using hematoxylin-eosin (HE) and Masson staining. ELISA was used to detect the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6 and hydroxyproline (Hyp) in serum and bronchoalveolar lavage fluid. TUNEL staining was used to detect cell apoptosis in lung tissue. The expressions of α-smooth muscle actin (α-SMA), collagen type I (collagen-I) and fibronectin-1 (FN-1) in lung tissue were detected by immunofluorescence. Western blotting was used to detect the expressions of p-p38, phosphorylated extracellular signal regulated kinase (p-ERK), phosphorylated c-Jun N-terminal kinase (p-JNK), B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) in lung tissue. Transforming growth factor-β1 (TGF-β1) was used to induce human lung fibroblasts (MRC-5) in vitro model. After intervention with Armeniacae Semen Amarum-Sophorae Flavescentis Radix containing serum, cell proliferation activity was detected using CCK-8 method. TUNEL staining was used to detect cell apoptosis. The expressions of α-SMA, collagen-I and FN-1 were detected by immunofluorescence. Western blotting was used to detect the expressions of p-RAF, phosphorylated mitogen activated protein kinase (p-MEK), p-ERK, Cyclin D1, proliferating cell nuclear antigen (PCNA), Bax and Bcl-2 proteins. Results In the in vivo experiment, compared with control group, the body weight of rats in model group was decreased (P < 0.01), the dry wet mass ratio and lung index of lung tissue were increased (P < 0.01), the lung tissue showed significant inflammatory infiltration, thickening and edema of alveolar space, and the cell apoptosis rate of lung tissue was decreased (P < 0.01), the levels of inflammatory factors in serum and bronchoalveolar lavage fluid were increased (P < 0.01), the protein expressions of α-SMA, collagen-I, FN-1, p-p38, p-ERK, p-JNK and Bcl-2 in lung tissue were significantly up-regulated (P < 0.01), while the protein expression of Bax was significantly down-regulated (P < 0.01). Compared with model group, the body weight of rats in each treatment group were increased (P < 0.01), the dry wet mass ratio and lung index of lung tissue were decreased (P < 0.01), the pathological changes of lung tissue were significantly improved, the cell apoptosis rate of lung tissue was increased (P < 0.01), the levels of inflammatory factors in serum and bronchoalveolar lavage fluid were decreased (P < 0.05, 0.01), the expressions of α-SMA, collagen-I, FN-1, p-p38, p-ERK, p-JNK and Bcl-2 proteins in lung tissue were significantly down-regulated (P < 0.01), and the expression of Bax protein was significantly up-regulated (P < 0.01). In the in vitro experiments, compared with control group, cell proliferation activity in model group was increased (P < 0.01), cell apoptosis rate was decreased (P < 0.01), α-SMA, collagen-Ⅰ, FN-1, p-RAF, p-MEK, p-ERK, Cyclin D1, PCNA, Bcl-2 protein expressions were increased (P < 0.01), and Bax protein expression was decreased (P < 0.01). Compared with model group, Armeniacae Semen Amarum-Sophorae Flavescentis Radix containing serum and RAF inhibitor GW5074 intervention resulted in a decrease in cell proliferation activity (P < 0.05, 0.01), an increase in cell apoptosis rate (P < 0.01), a decrease in the expressions of α-SMA, collagen-I, FN-1, p-RAF, p-MEK, p-ERK, Cyclin D1, PCNA, Bcl-2 proteins (P < 0.05, 0.01), and an increase in Bax protein expression (P < 0.05, 0.01). Conclusion Armeniacae Semen Amarum-Sophorae Flavescentis Radix exerts an anti-IPF effect by regulating RAF/MEK/ERK signaling pathway, inhibiting inflammatory response, suppressing cell proliferation and promoting cell apoptosis.

idiopathic pulmonary fibrosis  /  Armeniacae Semen Amarum-Sophorae Flavescentis Radix  /  RAF/MEK/ERK signaling pathway  /  inflammatory response  /  apoptosis