ABSTRACT
A variety of benzylidenethiazole analogs have been demonstrated to inhibit 5-lipoxygenase (5-LOX). Here we report the anti-atherogenic potential of 5-(4-hydroxy-2,3,5-trimethylbenzylidene) thiazolidin-2,4-dione (HMB-TZD), a benzylidenethiazole analog, and its potential mechanism of action in LDL receptor-deficient (Ldlr-/-) mice. HMB-TZD Treatment reduced leukotriene B4 (LTB4) production significantly in RAW264.7 macrophages and SVEC4-10 endothelial cells. Macrophages or endothelial cells pre-incubated with HMB-TZD for 2 h and then stimulated with lipopolysaccharide or tumor necrosis factor-alpha (TNF-alpha) displayed reduced cytokine production. Also, HMB-TZD reduced cell migration and adhesion in accordance with decreased proinflammatory molecule production in vitro and ex vivo. HMB-TZD treatment of 8-week-old male Ldlr-/- mice resulted in significantly reduced atherosclerotic lesions without a change to plasma lipid profiles. Moreover, aortic expression of pro-atherogenic molecules involved in the recruitment of monocytes to the aortic wall, including TNF-alpha , MCP-1, and VCAM-1, was downregulated. HMB-TZD also reduced macrophage infiltration into atherosclerotic lesions. In conclusion, HMB-TZD ameliorates atherosclerotic lesion formation possibly by reducing the expression of proinflammatory molecules and monocyte/macrophage recruitment to the lesion. These results suggest that HMB-TZD, and benzylidenethiazole analogs in general, may have therapeutic potential as treatments for atherosclerosis.
Subject(s)
Animals , Humans , Male , Mice , Atherosclerosis/drug therapy , Cell Adhesion/drug effects , Cell Line , Cell Movement/drug effects , Chemokine CCL2/metabolism , Dinoprostone/metabolism , Enzyme-Linked Immunosorbent Assay , Leukotriene B4/metabolism , Macrophages/cytology , Monocytes/cytology , Random Allocation , Receptors, LDL/deficiency , Thiazolidinediones/therapeutic use , Tumor Necrosis Factor-alpha/pharmacologyABSTRACT
We investigated the mechanism of spontaneous cholesterol efflux induced by acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibition, and how an alteration of cholesterol metabolism in macrophages impacts on that in HepG2 cells. Oleic acid anilide (OAA), a known ACAT inhibitor reduced lipid storage substantially by promotion of cholesterol catabolism and repression of cholesteryl ester accumulation without further increase of cytotoxicity in acetylated low-density lipoprotein-loaded THP-1 macrophages. Analysis of expressed mRNA and protein revealed that cholesterol 7alpha-hydroxylase (CYP7A1), oxysterol 7alpha- hydroxylase (CYP7B1), and cholesterol 27-hydroxylase (CYP27) were highly induced by ACAT inhibition. The presence of a functional cytochrome P450 pathway was confirmed by quantification of the biliary cholesterol mass in cell monolayers and extracelluar medium. Notably, massively secreted biliary cholesterol from macrophages suppressed the expression of CYP7 proteins in a farnesoid X receptor (FXR)-dependent manner in HepG2 cells. The findings reported here provide new insight into mechanisms of spontaneous cholesterol efflux, and suggest that ACAT inhibition may stimulate cholesterol-catabolic (cytochrome P450) pathway in lesion-macrophages, in contrast, suppress it in hepatocyte via FXR induced by biliary cholesterol (BC).
Subject(s)
Humans , Anilides/pharmacology , Bile/metabolism , Cells, Cultured , Cholesterol/metabolism , Cholesterol Esters/metabolism , DNA-Binding Proteins/agonists , Enzyme Inhibitors/pharmacology , Gene Expression Regulation, Enzymologic/drug effects , Hepatocytes/drug effects , Lipid Metabolism/drug effects , Macrophages/drug effects , Models, Biological , Oleic Acids/pharmacology , Receptors, Cytoplasmic and Nuclear/agonists , Sterol O-Acyltransferase/antagonists & inhibitors , Transcription Factors/agonistsABSTRACT
BACKGROUND: Naringin, one of the flavonoids in citrus fruit peels, is known to have antioxidant and hepatotonic effects in animal studies. We evaluated the effect of naringin on 1) blood lipid profiles, 2) regression of fatty streak of aorta, and 3) liver toxicity in diet-induced hypercholesterolemic rabbits. METHODS: New Zealand White Rabbits (2.0 - 2.5 Kg) were divided to three groups; group without treatment, group treated with 100 mg/kg/d or 500 mg/kg/d naringin, and group treated with 1 mg/kg/d or 20 mg/kg/d lovastatin. They were fed on 0.25% or 1.0% cholesterol-containing diet for 8 weeks and then sacrificed. Blood samples were collected for measurement of total cholesterol, HDL-cholesterol, triglyceride, serum GOT and GPT. Aortas and livers were harvested for evaluation of fatty streak and pathologic examination. RESULTS: 1)Feeding of 1% cholesterol diet for eight weeks significantly increased the cholesterol level upto 20 folds. Neither lovastatin nor naringin did lower these marked hypercholesterolemia. But both naringin (500 mg/kg/d) and lovastatin (1 mg/kg/d) significantly reduced the area of fatty streak by 75% and 58%, respectively. Naringin was more effective in inhibition of fat infiltration into liver than lovastatin which showed hepatotoxicity as increase of serum GPT level (p=0.01). 2)Feeding of 0.25% cholesterol diet for eight weeks significantly increased the cholesterol level upto 17 folds. Total cholesterol and triglyceride levels tended to decrease by treatment with naringin (500 mg/kg/d) and lovastatin (20 mg/kg/d), but this decreases were not statistically significant. However, areas of fatty streak significantly decreased by treatment with naringin and lovastatin by 64 and 82%, respectively (p<0.05). Microscopic analysis revealed that foam cell infiltration into intima was significantly reduced by naringin and lovastatin. In contrast to lovastatin, naringin significantly reduced the level of serum GPT (p<0.05). CONCLUSION: Like lovastatin, naringin has strong antiatherogenic action which may not be associated with its very mild lipid lowering action. In contrast to lovastatin, naringin does have hepatoprotective effect.