A novel small molecule liver X receptor transcriptional regulator, nagilactone B, suppresses atherosclerosis in apoE-deficient mice.

Atherosclerosis is the most common cause of cardiovascular diseases, such as myocardial infarction and stroke. We hypothesized that nagilactone B (NLB), a small molecule extracted from the root bark of Podocarpus nagi (Podocarpaceae), suppresses atherosclerosis in an atherosclerotic mouse model. Male apoE-deficient mice on C57BL/6J background received NLB (10 and 30 mg/kg) for 12 weeks. Compared with the model group, NLB treatment (10 and 30 mg/kg) significantly reduced en face lesions of total aorta areas. In RAW264.7 cells, NLB significantly ameliorated cholesterol accumulation in macrophages via enhancing apolipoprotein A-I and HDL-mediated cholesterol efflux. Mechanistically, NLB induced messenger RNA and protein expression of the ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) in RAW264.7 and THP-1 cells. Liver X receptor (LXR) site mutations in the mouse ABCA1 promoter abrogated NLB-mediated luciferase reporter activity. LXRα and LXRβ small interfering RNA suppressed NLB-mediated induction of ABCA1 expression. Consistent with in vitro results, NLB induced ABCA1 expression and suppressed macrophage areas in the aortic sinus. Moreover, NLB treatment did not induce the protein expression of LXR in liver. Hepatic and intestinal cholesterol accumulation was significantly alleviated on NLB treatment. Besides, NLB significantly improved plasma lipid profiles in apoE-deficient mice. Selective LXR activation in macrophages with NLB induces ABCA1- and ABCG1-mediated cholesterol efflux while exerting minimal effects on lipogenesis and lipid accumulation in liver, resulting in regression of atherosclerosis, and therefore might be a promising strategy for therapeutics.

Gui Y ，Yao S ，Yan H ，Hu L ，Yu C ，Gao F ，Xi C ，Li H ，Ye Y ，Wang Y ... -  《-》

Insulin-Like Growth Factor-1 Receptor Deficiency in Macrophages Accelerates Atherosclerosis and Induces an Unstable Plaque Phenotype in Apolipoprotein E-Deficient Mice.

We have previously shown that systemic infusion of insulin-like growth factor-1 (IGF-1) exerts anti-inflammatory and antioxidant effects and reduces atherosclerotic burden in apolipoprotein E (Apoe)-deficient mice. Monocytes/macrophages express high levels of IGF-1 receptor (IGF1R) and play a pivotal role in atherogenesis, but the potential effects of IGF-1 on their function are unknown. To determine mechanisms whereby IGF-1 reduces atherosclerosis and to explore the potential involvement of monocytes/macrophages, we created monocyte/macrophage-specific IGF1R knockout (MΦ-IGF1R-KO) mice on an Apoe(-/-) background. We assessed atherosclerotic burden, plaque features of stability, and monocyte recruitment to atherosclerotic lesions. Phenotypic changes of IGF1R-deficient macrophages were investigated in culture. MΦ-IGF1R-KO significantly increased atherosclerotic lesion formation, as assessed by Oil Red O staining of en face aortas and aortic root cross-sections, and changed plaque composition to a less stable phenotype, characterized by increased macrophage and decreased α-smooth muscle actin-positive cell population, fibrous cap thinning, and decreased collagen content. Brachiocephalic artery lesions of MΦ-IGF1R-KO mice had histological features implying plaque vulnerability. Macrophages isolated from MΦ-IGF1R-KO mice showed enhanced proinflammatory responses on stimulation by interferon-γ and oxidized low-density lipoprotein and elevated antioxidant gene expression levels. Moreover, IGF1R-deficient macrophages had decreased expression of ABCA1 and ABCG1 and reduced lipid efflux. Our data indicate that macrophage IGF1R signaling suppresses macrophage and foam cell accumulation in lesions and reduces plaque vulnerability, providing a novel mechanism whereby IGF-1 exerts antiatherogenic effects.

Higashi Y ，Sukhanov S ，Shai SY ，Danchuk S ，Tang R ，Snarski P ，Li Z ，Lobelle-Rich P ，Wang M ，Wang D ，Yu H ，Korthuis R ，Delafontaine P ... -  《-》

G004, a synthetic sulfonylurea compound, exerts anti-atherosclerosis effects by targeting SIRT1 in ApoE(-/-) mice.

Atherosclerosis attracts increasing global attention because of its morbidity and mortality. G004, as a synthetic sulfonylurea compound, has been confirmed to have anti-hyperglycaemia, anti-platelet and anti-thrombus effects. The aim of the present study was to investigate whether G004 suppress the onset and development of atherosclerosis and illuminate its probable mechanism of action. ApoE-/- mice that were fed a high-fat diet were randomly divided into five groups by weight; subsequently, they were treated with vehicle, G004, at different doses or atorvastatin once daily for 12weeks. Meanwhile, C57BL/6 mice with the same diet served as the normal controls. Then, the serum lipid profiles and histopathological damage to the liver, kidney, aortic arch and aortic root were analysed. The activation of endothelial nitric oxide synthase (eNOS) and levels of inflammatory markers were detected. Reverse cholesterol transport (RCT) was assessed in vivo by intraperitoneal injection of RAW264.7 cells that were radiolabelled with 3H-cholesterol. The results indicated that G004 ameliorated the serum lipid accumulation, atherosclerotic lesions and liver steatosis. Additionally, this compound increased the expression of SIRT1 and eNOS as well as the phosphorylation and deacetylation of eNOS in the aorta, alleviating the inflammatory state. RCT was promoted in ApoE-/- mice, which was accompanied by increased expression of SIRT1/LXRα/ABCA1/G1 in the liver, and similar results appeared in the cholesterol efflux assay in RAW264.7 cells. The results provide a strong rationale for G004 to be an efficient anti-atherosclerosis agent that improved vascular endothelial dysfunction by stimulating SIRT1/eNOS and promoted RCT by stimulating SIRT1/LXRα/ABCA1/G1.

Qian L ，Ma L ，Wu G ，Yu Q ，Lin H ，Ying Q ，Wen D ，Gao C ... -  《-》

Diosgenin inhibits atherosclerosis via suppressing the MiR-19b-induced downregulation of ATP-binding cassette transporter A1.

Diosgenin (Dgn), a structural analogue of cholesterol, has been reported to have the hypolipidemic and antiatherogenic properties, but the underlying mechanisms are not fully understood. Given the key roles of macrophages in cholesterol metabolism and atherogenesis, it is critical to investigate macrophage cholesterol efflux and development of atherosclerotic lesion after Dgn treatment. This study was designed to evaluate the potential effects of Dgn on macrophage cholesterol metabolism and the development of aortic atherosclerosis, and to explore its underlying mechanisms. Dgn significantly up-regulated the expression of ATP-binding cassette transporter A1 (ABCA1) protein, but didn't affect liver X receptor α levels in foam cells derived from human THP-1 macrophages and mouse peritoneal macrophages (MPMs) as determined by western blotting. The miR-19b levels were markedly down-regulated in Dgn-treated THP-1 macrophages/MPM-derived foam cells. Cholesterol transport assays revealed that treatment with Dgn alone or together with miR-19b inhibitor notably enhanced ABCA1-dependent cholesterol efflux, resulting in the reduced levels of total cholesterol, free cholesterol and cholesterol ester as determined by high-performance liquid chromatography. The fecal 3H-sterol originating from cholesterol-laden MPMs was increased in apolipoprotein E knockout mice treated with Dgn or both Dgn and antagomiR-19b. Treatment with Dgn alone or together with antagomiR-19b elevated plasma high-density lipoprotein levels, but reduced plasma low-density lipoprotein levels. Accordingly, aortic lipid deposition and plaque area were reduced, and collagen content and ABCA1 expression were increased in mice treated with Dgn alone or together with antagomiR-19b. However, miR-19b overexpression abrogated the lipid-lowering and atheroprotective effects induced by Dgn. The present study demonstrates that Dgn enhances ABCA1-dependent cholesterol efflux and inhibits aortic atherosclerosis progression by suppressing macrophage miR-19b expression.

Lv YC ，Yang J ，Yao F ，Xie W ，Tang YY ，Ouyang XP ，He PP ，Tan YL ，Li L ，Zhang M ，Liu D ，Cayabyab FS ，Zheng XL ，Tang CK ... -  《-》

Probucol-Oxidized Products, Spiroquinone and Diphenoquinone, Promote Reverse Cholesterol Transport in Mice.

Oxidized products of probucol, spiroquinone and diphenoquinone, were shown to increase cell cholesterol release and plasma high-density lipoprotein (HDL) by inhibiting degradation of ATP-binding cassette transporter A1. We investigated whether these compounds enhance reverse cholesterol transport in mice. Spiroquinone and diphenoquinone increased ATP-binding cassette transporter A1 protein (2.8- and 2.6-fold, respectively, P<0.01) and apolipoprotein A-I-mediated cholesterol release (1.4- and 1.4-fold, P<0.01 and P<0.05, respectively) in RAW264.7 cells. However, diphenoquinone, but not spiroquinone, enhanced cholesterol efflux to HDL (+12%, P<0.05), whereas both increased ATP-binding cassette transporter G1 protein, by 1.8- and 1.6-fold, respectively. When given orally to mice, both compounds significantly increased plasma HDL-cholesterol, by 19% and 20%, respectively (P<0.05), accompanied by an increase in hepatic and macrophage ATP-binding cassette transporter A1 but not ATP-binding cassette transporter G1. We next evaluated in vivo reverse cholesterol transport by injecting RAW264.7 cells labeled with (3)H-cholesterol intraperitoneally into mice. Both spiroquinone and diphenoquinone increased fecal excretion of the macrophage-derived (3)H-tracer, by 25% and 28% (P<0.01 and P<0.05), respectively. spiroquinone/diphenoquinone did not affect fecal excretion of HDL-derived (3)H-cholesterol, implying that macrophage-to-plasma was the most important step in spiroquinone/diphenoquinone-mediated promotion of in vivo reverse cholesterol transport. Finally, spiroquinone significantly reduced aortic atherosclerosis in apolipoprotein E null mice when compared with the vehicle. Spiroquinone and diphenoquinone increase functional ATP-binding cassette transporter A1 in both the macrophages and the liver, elevate plasma HDL-cholesterol, and promote overall reverse cholesterol transport in vivo. These compounds are promising as therapeutic reagents against atherosclerosis.

Yakushiji E ，Ayaori M ，Nishida T ，Shiotani K ，Takiguchi S ，Nakaya K ，Uto-Kondo H ，Ogura M ，Sasaki M ，Yogo M ，Komatsu T ，Lu R ，Yokoyama S ，Ikewaki K ... -  《-》