Autophagy as a novel insight into mechanism of Danqi pill against post-acute myocardial infarction heart failure

Ethnopharmacological relevance: Danqi Pill, composed of the root of Salvia miltiorrhiza Bunge and the root of Panax notoginseng, is effective in the clinical treatment of myocardial ischemia in coronary heart diseases. A number of studies have shown that autophagy plays an essential role in cardiac function and energy metabolism, and disordered autophagy is associated with the progression of heart failure. However, the effect and mechanism of Danqi pill on autophagy have not been reported yet.

Aim of the study: This study aims to elucidate whether Danqi pill restores autophagy to protect against HF and its potential mechanism.

Materials and methods: Left anterior descending ligation was established to induce an HF rat model, H₂O₂-stimulated H9C2 cells model was conducted to clarify the effects and potential mechanism of Danqi pill. In vivo, Danqi pill (1.5 g/kg) were orally administered for four weeks and Fenofibrate (10 mg/kg) was selected as a positive group. In vitro, Danqi pill (10∼200 μg/mL) was pre-cultured for 24 h and co-cultured with H₂O₂ stimulation for 4 h. Importantly, transmission electron microscopy and fluorescence GPF-mRFP-LC3 reporter system were combined to monitor autophagy flux. Furtherly, we utilized Compound C, a specific AMPK inhibitor, to validate whether the autophagy was mediated by AMPK-TSC2-mTOR pathway.

Results: Danqi pill significantly improved cardiac function and myocardial injury in HF rats. Intriguingly, Danqi pill potently regulated autophagy mainly by promoting the formation of autophagosomes in vivo. Further results demonstrated that expressions of p-AMPK (P<0.001) and p-TSC2 (P<0.001) in cardiac tissue were upregulated by Danqi pill, accompanied with downregulation of p-mTOR (P<0.01) and p-ULK1(P<0.01). In parallel with the vivo experiment, in vitro study indicated that Danqi pill dramatically restored autophagy flux and regulated expressions of critical autophagy-related molecules. Finally, utilization of Compound C abrogated the effects of Danqi pill on autophagy flux and the expressions of p-TSC2 (P<0.05), p-mTOR (P<0.01) and p-ULK1 (P<0.05).

Conclusion: Danqi pill could improve cardiac function and protect against cardiomyocytes injury by restoring autophagy via regulating the AMPK-TSC2-mTOR signaling pathway.

Keywords: AMPK-TSC2; Autophagy flux; acute myocardial infarction; heart failure.