Calycosin ameliorates atherosclerosis by enhancing autophagy via regulating the interaction between KLF2 and MLKL in apolipoprotein E gene‐deleted mice

Background and Purpose Atherosclerosis is one of the underlying causes of cardiovascular disease. Formation of foam cells and necrotic core in the plaque is a hallmark of atherosclerosis, which results from lipid deposition, apoptosis, and inflammation in macrophages. Macrophage autophagy is a critical anti‐atherogenic process and defective autophagy aggravates atherosclerosis by enhancing foam cell formation, apoptosis, and inflammation. Hence, enhancing autophagy can be a strategy for atherosclerosis treatment. Calycosin, a flavonoid from Radix Astragali, displays anti‐oxidant and anti‐inflammatory activities and therefore is potential to reduce the risk of cardiovascular disease. However, the anti‐atherogenic effect of calycosin and the involved mechanism remains unclear. In this study, we assessed the potential benefits of calycosin on autophagy and atherosclerosis, and revealed the underlying mechanism. Experimental Approach In this study, apoE−/− mice were fed high‐fat diet for 16 weeks in the presence of calycosin and/or autophagy inhibitor chloroquine, which was followed by determination of atherosclerosis development, autophagy activity, and involved mechanisms. Key Results Calycosin protected against atherosclerosis and enhanced plaque stability via promoting autophagy. Calycosin inhibited foam cell formation, inflammation, and apoptosis by enhancing autophagy. MLKL was demonstrated as a new autophagy regulator, which can be negatively regulated by KLF2. Mechanistically, inhibitory effects of calycosin on atherogenesis were via improved autophagy through KLF2‐MLKL signalling pathway modulation. Conclusions and Implications This study demonstrated the atheroprotective effect of calycosin was through upregulating KLF2‐MLKL‐mediated autophagy, which not only proposed novel mechanistic insights into t atherogenesis but also identified calycosin as a potential drug candidate for atherosclerosis treatment. apoE‐deficient (apoE−/−) mice (8‐week‐old, male, C57BL/6 background, purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd.) were randomly divided into four groups and received the following treatments: Ctrl group (n = 10), mice were fed high‐fat food (HFD, 21% fat and 0.5% cholesterol); Cal group (n = 10), mice were fed HFD containing calycosin (Calycosin, 60 mg·day−1·kg−1 body weight); CQ group (n = 10), mice were fed HFD and were intraperitoneally preinjected with CQ (chloroquine, 50 mg·kg−1 body weight, dissolved in 0.9% NaCl).