Atherosclerosis and Lipoproteins |
From the Departments of Clinical Renal Regeneration and Internal Medicine (K.H., T.F.), Division of Nephrology and Endocrinology, University of Tokyo, Japan; and the Department of Pharmacology (T.N.), Teikyo University School of Medicine, Japan.
Correspondence to Keiichi Hishikawa, Department of Internal Medicine, Division of Nephrology and Endocrinology, University of Tokyo, Hongo, 7-3-1, Bunkyo-ku, Tokyo, 113-8655, Japan. E-mail hishikawa-tky{at}umin.ac.jp
| Abstract |
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B (NF-
B). We examined the effects of oral CAPE supplementation on atherogenesis in apolipoprotein Edeficient (apoE/) mice.
Methods and Results Ten-week-old male apoE/ mice were supplemented orally with CAPE (30 mg/kg body weight) for 12 weeks. At the end of administration, atherosclerosis progression, NF-
B activity, gene expression profiling by microarray analysis, and oxidative stress were studied. Treatment of apoE/ mice with CAPE significantly reduced aortic atherosclerosis, NF-
B activity, and expression of NF-
Brelated genes in the aorta. Moreover, expression of other gene clusters such as basic transcription factors, growth factors, cytokines, cell adhesion proteins, and extracellular matrix were also significantly reduced by treatment with CAPE. Plasma isoprostane level in apoE/ mice was also significantly reduced by CAPE.
Conclusion In apoE/ mice, oral CAPE supplementation attenuates the atherosclerotic process. This may be attributable to direct inhibition of NF-
B in the lesion and reduction of systemic oxidative stress.
In apoE/ mice, oral caffeic acid phenethyl ester (CAPE) supplementation attenuates the atherosclerotic process and reduces NF-
B activity and expression of NF-
Brelated genes in the aorta. This may be attributable to direct inhibition of NF-
B in the lesion and reduction of systemic oxidative stress.
Key Words: atherosclerosis NF-
B microarray oxidative stress flavonoid
| Introduction |
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B (NF-
B) is a good therapeutic target for cardiovascular disease,1,2 and numerous efforts are being made to develop safe NF-
B inhibitors. Among the candidates are natural flavonoids, which constitute a promising class of dietary antioxidants that are found ubiquitously in fruits, vegetables, and tea. For example, resveratol, which is found in red wine, can inhibit NF-
B activity, the abrogation of which may contribute to the ability of red wine to reduce mortality from coronary heart disease and cancer.3,4 Curcumin, another NF-
B inhibitor, is an effective inhibitor of tumor initiation and promotion in different carcinogen-induced models.5 Among these natural flavonoids, the most promising is caffeic acid phenethyl ester (CAPE), which is structurally related to 3,4-dihydroxycinnamic acid and can be obtained from propolis, a honey constituent.6 CAPE is the only compound that has been shown to inhibit the HIV integrase enzyme needed for integration of HIV DNA into the host genome7 and is a potent and specific NF-
B inhibitor.8 We clarified recently that CAPE induced apoptosis in human breast cancer cells, but not in normal cells, by inhibiting NF-
B, leading to fas aggregation.9 The present studies were designed to examine whether CAPE could prevent atherosclerosis by inhibiting NF-
B activity in vivo. | Methods |
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Quantitation of Aortic Atherosclerosis
The extent of atherosclerosis in the mouse aorta was determined using an en-face method.10 Aortas were fixed in paraformaldehyde and stained with oil red O. Morphometric image analysis of the captured digitalized image of aorta was done using ImagePro Plus image software, and the lesion areas covering the aortic surface were quantitated.
NF-
B Assay
Specimens from mice were fixed at 80°C. The tissue was diced into small pieces with a cooled razor blade and placed in lysis buffer. Nuclear extracts were prepared using a nuclear extract kit (Active Motif). Total protein (20 µg) was loaded in each well, and NF-
B activity was measured using a TransAM NF-
B p65 kit (Active Motif) according to manufacturer directions.
Plasma Lipid and F2-Isoprostane Measurement
Blood samples were collected from animals fasted overnight, and plasma lipid levels were measured using an automated analyzer (Fuji Dri-Chem 3500V). Plasma F2-isoprostane level was measured using a StressXpress 8-Iso PGF2a ELISA kit (StressGen).
Microarray Analysis
DNA microarray hybridization experiments were performed using Mouse 3.8 (Clontech) according to the protocol of the manufacturer. The protocol and the complete list of genes on Mouse 3.8 are available on the web. DNA arrays were scanned with a Gene Pix 4000.11,12
Statistics
Results are shown as mean±SEM. Data were analyzed by ANOVA and subsequently by Student unpaired 2-tailed test. P values <0.05 were considered significant.
| Results |
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Effect of CAPE on Extent of Atherosclerosis
Mice were killed at 22 weeks of age and their aortas were harvested. Morphometric quantitation showed that the lesion area in the thoracic aorta was significantly less in CAPE-treated apoE/ mice than in untreated mice (Figure 2A). When the total aortic surface area was measured, aortic lesion area was also significantly less in the CAPE-treated group than in the untreated group (Figure 2B). We also performed histopathologic analysis, but there was no obvious regression such as unstable plaque lesion in the lesion of CAPE-treated group. These results suggest that CAPE is effective to prevent initiation and progression of new lesion, but its effect is minimal for regression of it.
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Effect of CAPE on NF-
B Activation
Compared with control mice (C57/B6 22 weeks), NF-
B activity (p65) was significantly higher in the aorta of apoE/ mice but not in the left ventricle (LV), right ventricle (RV), and kidney (Kid). Activation of NF-
B in the aorta of apoE/ mice was significantly inhibited by treatment with CAPE, but CAPE showed no effect in the LV, RV, and Kid (Figure 3).
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Gene Expression in Aorta
To evaluate the effect of CAPE, comprehensive gene expression in the aorta was assessed by microarray analysis. Compared with control mice (C57/B6 22 weeks), 88.9% of genes (3343/3758) were highly expressed in the aorta of apoE/ mice (Figure 4A). On the other hand, 63.4% of genes (2384 of 3758) were highly expressed in apoE/ mice treated with CAPE (Figure 4B). Among 3758 genes, expression of NF-
B related genes are shown in Figure 4C. Except for hemeoxygenase 1, these genes were significantly activated in apoE/ compared with control (C57/B6) mice. Moreover, expression of these genes (tumor necrosis factor-
[TNF-
], interleukin-2 [IL-2], platelet-derived growth factor [PDGF]-BB, and E-selectin) in apoE/ mice was significantly reduced by treatment with CAPE (Figure 4C). Gene expression of other NF-
Brelated genes such as vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 (ICAM-1) was evaluated by quantitative polymerase chain reaction, but CAPE had no effect on these 2 genes (data not shown). We further examined the effect of CAPE on expression of several gene clusters such as basic transcription factors (34 genes), growth factor cytokines (53 genes), cell adhesion proteins (29 genes), and extracellular matrix (50 genes; Figure 5). Average expression of all gene clusters was significantly higher compared with control mice (C57/B6 at 22 weeks). Although these gene clusters are not related to NF-
B, treatment with CAPE significantly reduced the expression of all these gene clusters.
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Effect of CAPE on Systemic Oxidative Stress
Because CAPE not only inhibits gene expression of NF-
Brelated genes but also other gene clusters, we evaluated its effect on systemic oxidative stress. Plasma F2-isoprostane level was significantly higher in apoE/ compared with control mice, but this was significantly reduced by treatment with CAPE (Figure 6). We also measured lipid peroxidation marker malondialdehyde-modified LDL by ELISA kit (LPO assay kit; BIOXYTEC LPO, Oxis), but CAPE had no effect on it.
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| Discussion |
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B inhibitor, CAPE, prevents atherosclerosis even in the presence of a high level of plasma cholesterol without serious adverse effects. We confirmed that CAPE inhibits NF-
B activity in the aorta, the target organ of hypercholesterolemia, and have also shown that CAPE reduced the expression of NF-
Brelated genes such as TNF-
, IL-2, PDGF-BB, and E-selectin in the aorta, demonstrating that treatment with CAPE actually inhibited molecular events downstream of NF-
B activation in vivo. NF-
B is a good target for treating atherosclerosis, but there is no specific and potent inhibitor that can be applied to clinical therapy. CAPE, a structural derivative of flavonoids, has been shown to be a safe pharmacological compound with known anti-inflammatory, immunomodulatory, anticarcinogenic, and antioxidant properties. CAPE completely blocked activation of NF-
B induced by a wide variety of inflammatory agents, including TNF-
, phorbol ester, ceramide, okadaic acid, and H2O2 in vitro.8
NF-
B inhibition by CAPE has been examined extensively in many in vitro studies. In human coronary artery endothelial cells, CAPE inhibited oxidized LDLmediated degradation of I
B
and NF-
B activation and inhibited oxidized LDLinduced upregulation of angiotensin II type 1 receptor expression.16 CAPE inhibited oxidized LDLinduced apoptosis in human aortic endothelial cells mediated by the action of the lectin-like endothelial receptor for oxidized LDL.17 CAPE concentration-dependently inhibited chlamydophila pneumoniaeinduced ICAM-1 upregulation in human aortic endothelial cells by inhibiting NF-
B.18 Moreover, CAPE specifically inhibited IL-2 gene transcription and IL-2 synthesis in stimulated T-cells and inhibited NF-
Bdependent transcriptional activity without affecting degradation of the cytoplasmic NF-
B inhibitory protein I
B
.19 Compounds that have potent NF-
B inhibition frequently show a limited effect in vivo. On the other hand, CAPE shows a potent effect in vivo.2025 Concerning vascular disease, CAPE also inhibited NF-
B activation in rat carotid arteries induced by balloon injury in vivo.13 As Ceschel et al reported that CAPE has good permeability across mucosa in vitro,26 CAPE may also have good bioavailability pharmacologically in vivo.
Compared with control mice (C57/B6), microarray analysis of the aorta clarified that many genes were activated in apoE/ mice, and CAPE normalized 40% of them. The precise mechanism is unclear, but several pathways could be involved, except NF-
B inhibition. In smooth muscle cells from porcine coronary artery, CAPE arrested angiotensin IIdependent DNA synthesis and migration. CAPE prevented phosphorylation of cyclin-dependent kinase 2 and retinoblastoma protein.27 CAPE also modulates ion channels. CAPE increased the Ca2+-activated K+ current and slightly suppressed the voltage-dependent L-type Ca2+ current. CAPE-stimulated channel activity was dependent on membrane potential.28 CAPE inhibited the increase in cytosolic Ca2+ concentration triggered by stimulation of aortic smooth muscle cells with phenylephrine or KCl.29 Considering the structure of CAPE, we are not able to explain these effects, but these pathways could contribute to the protective effect of CAPE on atherosclerosis.
CAPE is well known to have a free radicalscavenging effect and also inhibits xanthine oxidase activity.30 Recently, the structureactivity relationships of synthetic caffeic acid amide and ester analogs as potential antioxidants and free radical scavengers have been investigated. The 2,2-diphenyl-1-picrylhydrazyl radicalscavenging activity of the test compounds was N-trans-caffeoyl-L-cysteine methyl ester > N-trans-caffeoyldopamine > N-trans-caffeoyltyramine > N-trans-caffeoyl-ß-phenethylamine > Trolox C > CAPE > caffeic acid > ferulic acid. On the other hand, antioxidative activity order was CAPE > N-trans-caffeoyl-ß-phenethylamine > N-trans-caffeoyldopamine > N-trans-caffeoyltyramine > N-trans-caffeoyl-L-cysteine methyl ester > caffeic acid > Trolox C > ferulic acid. These results suggested that the antioxidative activity of CAPE depends not only on the hydroxyl groups or catechol rings but also on the partition coefficient or hydrophobicity of the compounds.31 In rat bleomycin-induced pulmonary fibrosis models, an increase in catalase and superoxide dismutase activities and a decrease in myeloperoxidase activity were seen after CAPE application.32 CAPE was more effective in decreasing the tissue levels of NO, hydroxyproline, and malondialdehyde than vitamin E.32 Pratico et al reported that oxidative stress is increased in the apoE/ mouse, is of functional importance in the evolution of atherosclerosis, and can be suppressed by oral administration of the antioxidant vitamin E.33 In our studies, treatment with CAPE reduced the plasma F2-isoprostane level and inhibited not only NF-
B related genes but also several gene clusters such as basic transcription factors, growth factor cytokines, cell adhesion proteins, and extracellular matrix. Because oxidative stress is well known to activate these genes, the antioxidant property of CAPE may play a key role to reduce atherosclerosis in apoE/ mice. In conclusion, our results suggest that CAPE is a promising compound for treatment of atherosclerosis by inhibiting NF-
B and by reducing oxidative stress.
| Acknowledgments |
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Received August 5, 2004; accepted October 5, 2004.
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