E3317 promotes cholesterol efflux in macrophage cells via enhancing ABCA1 expression

Reverse cholesterol transport (RCT) plays an important role in cholesterol and lipid metabolism. Regulating the activities of key transporters and receptors in RCT, such as ATP-binding cassette transporter A1 (ABCA1), helps to prevent atherosclerotic cardiovascular disease. In this study, we used an ABCA1 promoter luciferase reporter assay to screen 20,000 compounds for ABCA1 upregulators. Compound E3317 (N-(6-butylbenzo[d]thiazol-2(3H)-ylidene)-3-(N-(2-cyanoethyl)sulfamoyl)benzamide)) was identified as a positive hit with an EC50 value of 0.2 mu M in ABCA1 p-LUC HepG2 cells. Thus, we hypothesized that E3317 might have cholesterol- and lipid metabolism-regulating effects through ABCA1 upregulation. E3317 significantly increased ABCA1 mRNA and protein expression in hepatic LO2 cells and RAW264.7 macrophages. E3317 promoted cholesterol efflux to apolipoprotein A-I in RAW264.7 macrophages and significantly decreased lipid accumulation in oxidized low-density lipoprotein-induced murine RAW264.7 macrophages. Further studies using ABCA1 siRNA showed that the promotion of cholesterol efflux and decrease of lipid accumulation by E3317 depended on ABCA1 expression. Mechanistic studies indicated that E3317 regulated ABCA1 expression via activating nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR gamma), which plays an important role in the regulation of glucose homeostasis and lipid metabolism. The structure of E3317 was docked in the ligand-binding domain of PPAR gamma (PBD code: 4EMA) to find the key binding amino acids. Site mutation assays confirmed that Y327 and F363 were the key PPAR gamma binding epitopes of E3317. Our results revealed that E3317 upregulates ABCA1 expression and thereby promotes cholesterol efflux. E3317 may regulate ABCA1 expression through PPAR gamma. Our findings provide a new compound, E3317, which may have beneficial cardiovascular effects. (C) 2018 Elsevier Inc. All rights reserved.