Liquiritigenin attenuates isoprenaline‑induced myocardial fibrosis in mice through the TGF‑β1/Smad2 and AKT/ERK signaling pathways

Figure 1.. LQ ameliorates ISO-induced myocardial fibrosis in mice. (A) Chemical structure of LQ. (B-E) A mouse model of myocardial fibrosis was established. The serum levels of (B) LDH (U/l), (C) α-HBDH (U/l), (D) CK-MB (IU/l), (E) cTnl (ng/ml) and (F) cTnT (ng/ml) were measured by enzyme-linked immunosorbent assay. ###P<0.001 vs. the control group; *P<0.05, ***P<0.001 vs. the ISO group. (G) Mouse heart tissues were harvested for histopathological examination using Masson's trichrome staining. Representative images at ×200 and 400 magnification are shown. α-HBDH, α-hydroxybutyrate dehydrogenase; CK-MB, creatine kinase isoenzyme MB; cTnI, cardiac troponin I; cTnT, cardiac troponin T; ISO, isoprenaline; LDH, lactate dehydrogenase; LQ, liquiritigenin.

Figure 2.. Effect of LQ on cardiac function in ISO-treated mice. Echocardiography was performed in all groups of mice using an M-mode ultrasound imaging system. The parameters indicating cardiac function were measured, including (A) LV ESD (mm), (B) LV EDD (mm), (C) FS (%) and (D) EF (%). ###P<0.001 vs. the control group; *P<0.05, ***P<0.001 vs. the ISO group. (E) M-mode echocardiograms of the LV from each group of mice are shown. EF, ejection fraction; FS, fractional shortening; ISO, isoprenaline; LQ, liquiritigenin; LV, left ventricle; LV EDD, LV end-diastolic dimension; LV ESD, LV end-systolic dimension.

Figure 3.. Effect of LQ on activation of the TGF-β1/Smad2 and AKT/ERK pathways in ISO-treated mice. Expression levels of proteins related to the (A) TGF-β1/Smad2 and (B) AKT/ERK pathways were measured by western blotting. Semi-quantification of the expression levels of (C) α-SMA, (D) Smad2, (E) TGF-β1, (F) collagen III, (G) collagen I, (H) p-AKT/AKT and (I) p-ERK/ERK normalized to the expression of GAPDH. ##P<0.01, ###P<0.001 vs. the control group; *P<0.05, **P<0.01, ***P<0.001 vs. the ISO group. AKT, protein kinase B; α-SMA, α-smooth muscle actin; ERK, extracellular signal-regulated kinase; ISO, isoprenaline; LQ, liquiritigenin; p-, phosphorylated; TGF- β1, transforming growth factor β1.

Figure 4.. Effect of LQ on the apoptosis of cardiomyocytes following Ang II exposure. An in vitro model of cardiac dysfunction was established in rat myocardial H9C2 cells. Apoptosis of H9C2 cells in the (A) control, (B) Ang II, (C) Ang II + LQ (low), (D) Ang II + LQ (medium) and (E) Ang II + LQ (high) groups was examined by flow cytometry. (F) Apoptosis rate was calculated. ###P<0.001 vs. the control group; *P<0.05, **P<0.01 vs. the Ang II group. Ang II, angiotensin II; LQ, liquiritigenin; PI, propidium iodide.

Figure 5.. Effect of LQ on Ang II-induced activation of the TGF-β1/Smad2 and AKT/ERK pathways. H9C2 cells were collected following LQ pretreatment and Ang II stimulation. Cell lysates were prepared for western blot analysis. The expression levels of proteins related to the (A) TGF-β1/Smad2 and (B) AKT/ERK pathways were assessed. Semi-quantification of the protein expression levels of (C) α-SMA, (D) Smad2, (E) TGF-β1, (F) collagen III, (G) collagen I, (H) p-AKT/AKT and (I) p-ERK/ERK normalized to the expression of GAPDH. ##P<0.01, ###P<0.001 vs. the control group; *P<0.05, **P<0.01, ***P<0.001 vs. the Ang II group. AKT, protein kinase B; Ang II, angiotensin II; α-SMA, α-smooth muscle actin; ERK, extracellular signal-regulated kinase; LQ, liquiritigenin; p-, phosphorylated; TGF- β1, transforming growth factor β1.