Schisandrin B Antagonizes Cardiotoxicity Induced by Pirarubicin by Inhibiting Mitochondrial Permeability Transition Pore (mPTP) Opening and Decreasing Cardiomyocyte Apoptosis

FIGURE 1. SchB effectively improved the abnormal body weight and food intake of SD rats induced by THP. (A) From the third week, the body weight of rats injected with THP alone was significantly lower than that of normal rats (THP vs. CON, p < 0.05). The weight loss of THP rats was further reduced after 4 weeks (p < 0.01, THP vs. CON). In THP rats treated with SchB (50 mg*kg−1), weight loss was significantly improved (p < 0.05, SchB + THP vs. THP). The improvement was more significant after the fifth week (p < 0.01, SchB + THP vs. THP). (B) From the fourth week, the food intake of rats injected with THP alone was significantly lower than that of normal rats (THP group vs. CON group, p < 0.05). The food intake of THP rats decreased further after 6 weeks (p < 0.01, THP and CON). In THP rats treated with SchB (50 mg*kg−1), the food intake increased significantly (p < 0.05, SchB + THP vs. THP). The improvement was more significant after the seventh week (p < 0.01, SchB + THP vs. THP). All values are mean ± SD. * p < 0.05 vs. CON, ** p < 0.01 vs. CON; # p < 0.05 vs. THP, and ## p < 0.01 vs. THP.

FIGURE 2. SchB effectively improved the echocardiographic and ECG changes of SD rats induced by THP. Compared with normal rats, EF (A) and % FS (B) decreased and LVIDd (C) and LVIDs (D) thickened (THP vs. CON). Compared with normal SD rats, the ECG of THP rats was also abnormal (THP vs CON). The R wave (E) and T wave (G) voltage increased; S wave voltage decreased (F); and QT interval (H) prolonged (THP vs. CON). After treatment with SchB (50 mg*kg−1), the above changes were significantly improved (SchB + THP vs. THP). All values are mean ± SD. * p < 0.05 vs. CON, ** p < 0.01 vs. CON, # p < 0.05 vs. THP, and ## p < 0.01 vs. THP.

FIGURE 3. SchB attenuated THP-induced cardiac histopathological changes, apoptosis, and increased CWI. The myocardial tissue structure of the CON and SchB group was normal. In the THP group, the arrangement of cardiomyocytes was disordered, the intercellular space was significantly increased, and the cardiomyocytes were focal vacuolization or steatosis. The vacuolation and steatosis of myocardial cells in rats treated with SchB were significantly improved. TUNEL staining showed that there was no apoptosis in the control group and SchB group. In the THP group, there was partial apoptosis. In the group of SchB + THP, a few or a single cell apoptosis was occasionally observed. The CWI of rats in the THP group was significantly higher than that in the normal group, and the CWI of rats in the SchB + THP group was significantly lower than that in the THP group. All values are the mean ± SD. * p < 0.05 vs. CON, ** p < 0.01 vs. CON, # p < 0.05 vs. THP, and ## p < 0.01 vs. THP.

FIGURE 4. SchB effectively improved the level of serum markers in heart injury induced by THP: (A) superoxide dismutase (SOD) levels, (B) malondialdehyde (MDA) levels, (C) lactate dehydrogenase (LDH) levels, (D) brain natriuretic peptide (BNP) levels, (E) creatine kinase MB (CK-MB) levels, and (F) cardiac troponin T (cTnT) levels. All values are mean ± SD. * p < 0.05 vs. CON, ** p < 0.01 vs. CON, # p < 0.05 vs. THP, and ## p < 0.01 vs. THP.

FIGURE 5. SchB ameliorates THP-induced abnormal expression of apoptosis-related proteins in rat heart. The content of mitochondrial Cyt C (A) decreased and Bax (B) increased in the THP group, but reversed in the SchB + THP group (C). In the THP group, the expression of cytosolic Cyt C and cleaved-caspase 9/3 increased, while procaspase 3 and Bcl-2/Bax ratio decreased. The above changes were reversed in the SchB + THP group. More evidence can be found in the semiquantitative analysis (A–C). All values are mean ± SD. * p < 0.05 vs. CON, ** p < 0.01 vs. CON, # p < 0.05 vs. THP, and ## p < 0.01 vs. THP.

FIGURE 6. SchB ameliorates THP-induced abnormal expression of apoptosis-related proteins in rat heart. (A) Screening of optimum treatment concentration of SchB. (B) Observation on the effect of coculture of SchB and CsA. (C) ROS staining in each group. (D) Quantification of relative fluorescence intensity of ROS in each group. (E) H9C2 cells in CON, SchB, and CsA groups showed bright green fluorescence, while only weak green fluorescence was observed in the THP group. The green fluorescence was more obvious in SchB + THP and CsA + THP groups, which was greatly improved compared with THP. Ionomycin was a strong positive control. Nonquenched Cyt Flu was that the cytoplasmic fluorescence is not quenched. (F) Fluorescence quantitative analysis. (G) Mitochondrial swelling was analyzed for 10 min. All values are mean ± SD. * p < 0.05 vs. CON, ** p < 0.01 vs. CON, # p < 0.05 vs. THP, and ## p < 0.01 vs THP.

FIGURE 7. SchB ameliorates THP-induced abnormal expression of apoptosis-related proteins in rat heart. THP caused the decrease of Cyt C (A) and increase of Bax (B) content in mitochondria. The above changes were alleviated by the treatment of mPTP inhibitor CsA. SchB treatment showed similar effects. In addition, THP also increased the expression of Cyt C and cleaved-caspase 3/9, decreased the expression of procaspase 3, and decreased the ratio of Bcl-2/Bax in cytoplasm (C). After treatment with SchB or CsA, the above changes were alleviated effectively (C). More evidence can be found in the semiquantitative analysis (A–C). All values are mean ± SD. * p < 0.05 vs. CON, ** p < 0.01 vs. CON, # p < 0.05 vs. THP, and ## p < 0.01 vs. THP.