Astragalus flavone ameliorates atherosclerosis and hepatic steatosis via improving lipid metabolism and inhibition of inflammation in apoE-/- mice

Abstract

Background: Atherosclerosis is a major pathogenic factor in cardiovascular diseases during the aging process. Foam cell formation and endothelial dysfunction play a key role in the initiation and development of atherosclerosis, which are affected by lipid disorder and inflammation. Therefore, the drug for inhibition of endothelial dysfunction and the subsequent foam cell formation is a therapeutic approach for atherosclerosis treatment. Total flavone of Astragalus membranaceus (TFA) is extracted from Astragalus membranaceus that has protective effect on cardiovascular disease. However, the effect of TFA on atherosclerosis and the underlying mechanism remains unknown. Methods: In this study, we determined whether TFA could inhibit atherosclerosis; and uncovered the underlying molecular mechanisms. In vivo, apoE deficient mice were treated with TFA contained in high-fat diet for 16 weeks. After treatment, aorta, macrophage and serum samples were collected to determine atherosclerotic lesions, lipid metabolism, and expression of associated genes. Concurrently, we investigated the effect of TFA on monocyte adhesion, foam cell formation, endothelial activation, and macrophage polarization in vitro and in vivo. Results: TFA reduced atherosclerotic plaque size; and enhanced lesion stability by changing the composition of plaque. Moreover, foam cell formation and its accumulation in arterial wall were attenuated by TFA, which might be attributed to improved lipid disorder, reduced inflammation, and decreased monocyte adhesion to endothelial cells. Mechanistically, TFA reduced the expression of scavenger receptor, such as CD36 and SRA; promoted the expression of ATP-binding cassette transporter A1 and G1 (ABCA1/G1). More importantly, TFA reduced the expression of miR-33, a negative regulator of cholesterol efflux as well as positive mediator on inflammation; and concurrently reduced NFkB activity, by which de-repressed ABCA1/G1 activity and inhibited the inflammation. Conclusions: This study demonstrates that TFA can attenuate atherosclerosis via dual inactivation of miR-33 and NFkB signaling pathway and inhibition of scavenger receptors (CD36 and SRA), which suggests that TFA might be a novel therapeutic approach for inhibition of atherosclerosis.