OBJECTIVE: To observe whether metformin (MET) inhibits transforming growth factor-β₁ (TGF-β₁)/Smad3 signaling pathway by activating adenosine activated protein kinase (AMPK), so as to alleviate the pulmonary fibrosis caused by paraquat (PQ) poisoning in mice. METHODS: Male C57BL/6J mice were randomly divided into the Control group, PQ poisoning model group (PQ group), MET intervention group (PQ+MET group), AMPK agonist group (PQ+AICAR group), and AMPK inhibitor group (PQ+MET+CC group), according to a random number table method. A mouse model of PQ poisoning was established by one-time peritoneal injection of 1 mL PQ solution (20 mg/kg). The Control group was injected with the same volume of normal saline. After 2 hours of modeling, the PQ+MET group was given 2 mL of 200 mg/kg MET solution by gavage, the PQ+AICAR group was given 2 mL of 200 mg/kg AICAR solution by intraperitoneal injection, the PQ+MET+CC group was given 2 mL of 200 mg/kg MET solution by gavage and then 1 mL complex C (CC) solution (20 mg/kg) was intraperitoneally injected, the Control group and PQ group were given 2 mL of normal saline by gavage. The intervention was given once a day for 21 consecutive days. The 21-day survival rate of ten mice in each group was calculated, and the lung tissues of remaining mice were collected at 21 days after modeling. The pathological changes of lung tissues were observed under light microscope after hematoxylin-eosin (HE) staining and Masson staining, and the degree of pulmonary fibrosis was evaluated by Ashcroft score. The content of hydroxyproline in lung tissue and oxidative stress indicators such as malondialdehyde (MDA) and superoxide dismutase (SOD) were detected. The protein expressions of E-cadherin, α-smooth muscle actin (α-SMA), phosphorylated AMPK (p-AMPK), TGF-β₁ and phosphorylated Smad3 (p-Smad3) in lung tissue were detected by Western blotting. RESULTS: Compared with the Control group, the 21 days survival rate was significantly reduced, lung fibrosis and Ashcroft score were significantly increased in PQ group. In addition, the content of hydroxyproline, MDA and the protein expressions of α-SMA, TGF-β₁ and p-Smad3 in lung tissue were significantly increased, while the activity of SOD and the protein expressions of E-cadherin and p-AMPK were significantly decreased in PQ group. Compared with the PQ group, the 21 days survival rates of mice were significantly improved in the PQ+MET group and PQ+AICAR group (70%, 60% vs. 20%, both P < 0.05). The degree of pulmonary fibrosis and the Ashcroft score were significantly reduced (1.50±0.55, 2.00±0.63 vs. 6.67±0.52, both P < 0.05). The content of hydroxyproline and MDA in lung tissue, as well as α-SMA, TGF-β₁ and p-Smad3 protein expressions were significantly reduced [hydroxyproline (mg/L): 2.03±0.11, 3.00±0.85 vs. 4.92±0.65, MDA (kU/g): 2.06±1.48, 2.10±1.80 vs. 4.06±1.33, α-SMA/GAPDH: 0.23±0.06, 0.16±0.06 vs. 1.00±0.09, TGF-β₁/GAPDH: 0.28±0.03, 0.53±0.05 vs. 0.92±0.06 p-Smad3/GAPDH: 0.52±0.04, 0.69±0.06 vs. 1.11±0.10, all P < 0.05], SOD activity and the protein expressions of E-cadherin and p-AMPK were significantly increased [SOD (μmol/g): 39.76±1.35, 33.03±1.28 vs. 20.08±1.79, E-cadherin/GAPDH: 0.91±0.08, 0.72±0.08 vs. 0.26±0.04, p-AMPK/GAPDH: 0.62±0.04, 0.60±0.01 vs. 0.20±0.04, all P < 0.05]. However, these protective effects of MET were inhibited by the addition of AMPK inhibitor CC solution. CONCLUSIONS MET can effectively alleviate the degree of pulmonary fibrosis in mice poisoned with PQ, and its mechanism may be related to the activation of AMPK and inhibition of TGF-β₁/Smad3 signaling pathway, which can be inhibited by AMPK inhibitor CC.
Mice ; Male ; Animals ; Pulmonary Fibrosis/drug therapy* ; Paraquat ; AMP-Activated Protein Kinases/pharmacology* ; Metformin/pharmacology* ; Hydroxyproline/pharmacology* ; Saline Solution ; Mice, Inbred C57BL ; Lung/metabolism* ; Transforming Growth Factor beta1/pharmacology* ; Cadherins ; Superoxide Dismutase

Objective:To investigate the protective effect and possible mechanism of sulforaphane (SFN) on acute liver injury in mice induced by diquat (DQ) poisoning.Methods:Forty-eight male C57BL/6 mice were divided into Control group, DQ model group (DQ group), SFN intervention group (DQ+SFN group), and SFN control group (SFN group) using a random number table method, with 12 mice in each group. Acute liver injury mice model was established by one-time intraperitoneal injection of 1 mL of 40 mg/kg DQ solution at once. SFN group was injected with 1 mL of ddH 2O. After 4 hours of molding, 0.5 mL of 5 mg/kg SFN solution was injected into the peritoneal cavity of the DQ+SFN group and SFN group, once daily for 7 consecutive days. DQ group and Control group were injected with an equal amount of ddH 2O. Then, the mice were euthanized to collect liver tissue and blood samples, and the levels of plasma biomarkers alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as oxidative stress indicators such as superoxide dismutase (SOD), glutathione (GSH), and malondialdehyde (MDA) in liver tissue were measured. The changes of liver structure were observed under transmission electron microscopy. The apoptosis and reactive oxygen species (ROS) level in liver tissue were observed under fluorescence microscope. Western blotting was used to detect the protein expressions of nuclear factor E2-related factor 2 (Nrf2), hemeoxygenase-1 (HO-1), Kelch-like ECH-associated protein 1 (Keap1), and cleaved caspase-9 in liver tissue. Results:Compared with the Control group, the liver mitochondria in the DQ group showed severe swelling, partial dissolution of the matrix, and cristae rupture and loss; the levels of plasma AST and ALT significantly increased, the MDA content in the liver increased, the activities of SOD and GSH decreased, the level of ROS significantly increased, the number of apoptotic cells in the liver significantly increased, the protein expressions of Nrf2 and HO-1 significantly decreased, and the protein expressions of Keap1 and cleaved caspase-9 significantly increased. Compared with the DQ group, the mitochondrial damage in the DQ+SFN group was reduced, the levels of plasma AST and ALT were significantly reduced [ALT (U/L): 58.22±4.39 vs. 79.94±3.32, AST (U/L): 177.64±8.40 vs. 219.62±11.60, both P < 0.01], the liver MDA content decreased, and the activities of SOD and GSH increased [MDA (μmol/g: 5.63±0.18 vs. 5.96±0.29, SOD (kU/g): 102.05±4.01 vs. 84.34±5.34, GSH (mmol/g): 16.32±1.40 vs. 13.12±1.84, all P < 0.05], the production of ROS in liver tissue was significantly reduced [ROS (fluorescence intensity): 115.90±10.89 vs. 190.70±10.16, P < 0.05], and apoptotic cells were significantly reduced (cell apoptosis index: 4.39±1.00 vs. 10.71±0.56, P < 0.01), the protein expressions of Nrf2 and HO-1 were significantly increased, while the protein expressions of Keap1 and cleaved caspase-9 were significantly decreased (Nrf2/β-actin: 1.15±0.04 vs. 0.93±0.05, HO-1/β-actin: 1.75±0.12 vs. 0.78±0.04, Keap1/β-actin: 1.00±0.14 vs. 1.28±0.13, cleaved caspase-9/β-actin: 1.31±0.12 vs. 1.81±0.09, all P < 0.05). However, there was no statistically significant difference in various indicators between the SFN group and the Control group. Conclusion:SFN can activate the Keap1/Nrf2 signaling pathway to alleviate DQ induced acute liver injury in mice.