ABSTRACT
Objective To investigate the protective effects of astragaloside IV (AS IV) on chronic intermittent hypoxia (CIH) -induced cardiac injury. Methods Twenty-four male adult Sprague Dawley rats were randomly assigned to control, CIH, CIH+ASIV, and ASIV group, 6 rats in each group. Circular nitrogen and oxygen were filled to make oxygen concentration change between 9%-21% for the CIH treated rats. The exposure cycle was repeated every 3 minutes, 8 hours/ day for 35 days. ASIV was given by intragastric administration daily before intermittent hypoxia exposure in the CIH+ASIV group and AS IV group. The control group and CIH group were given normal saline of the same quantity. Echocardiography was used to analyse cardiac function. Myocardial structure was assessed by HE and wheat germ agglutinin staining. The apoptosis of cardiomyocytes was detected by TUNEL assay. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in heart were detected by commercial kits. Western blotting was used to evaluate the levels of Bcl-2, Bax, LC3, Beclinl, P62, and mammalian target of rapamycin (mTOR). Results In the CIH group, the left ventricular ejection fraction (LVEF) and left ventricular internal diameter at end-systole (LVIDs) were inhibited, the myocyte cells showed disordered arranged, enlarged diameters and higher apoptosis rate. The MDA content was significantly elevated and the SOD activity decreased in CIH group when compared with those of control. What's more, the expression level of Beclin 1 decreased while the P62 expression and the p-mTOR/mTOR ratio increased in the CIH group. Compared with the model group, the LVEF, LVIDs, SOD activity, LC3 H / I ratio, and Beclinl expression of rats in the CIH + AS IV group increased. The cardiomyocytes in the rats of CIH + ASIV group showed normal arrangement and diameters. The apoptosis rate, MDA content, P62 expression and the p-mTOR/mTOR ratio decreased in the CIH+ASIV group when compared with the CIH group. Conclusion AS IV can alleviate CIH-induced cardiac injury by promoting autophagy via mTOR.