Rabbit Model Of Atherosclerosis Research Articles

Ezetimibe inhibe la adhesión y la migración de monocitos a través de la ruta de las proteincinasas activadas extracelularmente (p44/p42 ERK1/2

Introduction Recently, our group has demonstrated that ezetimibe, a specific inhibitor of intestinal absorption, is able to inhibit vascular inflammation in a rabbit model of atherosclerosis. In this study, we investigated the effect of ezetimibe on the adhesion and migration of human THP-1 monocytes in vitro. We also studied the involvement of the MAP kinase signalling pathway, p44/p42 ERK1/2, as a potential mechanism responsible for the observed effect. Material and methods Adhesion of THP-1 monocytes was measured as the ability of cells to bind to plates. Migration was studied using two-compartment chambers. The expression of adhesion molecules was assessed by flow cytometry. Activation of p44/p42 ERK1/2 was measured by Western Blot. Results Preincubation of THP-1 monocytes with ezetimibe prevented PMA-induced adhesion and MCP-1-induced migration in a dose-dependent manner. Preincubation of THP-1 monocytes with ezetimibe also inhibited the expression of the integrins CD11a and CD11b, as well as phosphorylation of p-p44/p42 ERK1/2 (the active form) induced by MCP-1. More than 90% of cells (evaluated through trypan blue) were viable 1 or 2 days after exposure to ezetimibe. Conclusions Our results indicate that, in addition to its lipid lowering activity, ezetimibe is able to inhibit the process of adhesion and migration of monocytes in vitro. Blocking of the p44/p42 ERK1/2 MAPK signalling pathway seems to play a role in this anti-inflammatory effect.

CRP enhances soluble LOX-1 release from macrophages by activating TNF-α converting enzyme

Circulating levels of soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1) play an important role in the development and progression of atherosclerosis. We hypothesized that the inflammatory marker C-reactive protein (CRP) might stimulate sLOX-1 release by activating tumor necrosis factor-α converting enzyme (TACE). Macrophages differentiated from THP-1 cells were stimulated with TNF-α and further treated with CRP in the absence or presence of specific inhibitors or small interfering RNA (siRNA). Our results showed that CRP increased sLOX-1 release from activated macrophages in a dose-dependent manner and that these effects were regulated by Fc γ receptor II (FcγRII)-mediated p47(phox) phosphorylation, reactive oxygen species (ROS) production, and TACE activation. CRP also enhanced sLOX-1 release from macrophages derived from peripheral blood mononuclear cells (PBMC) of patients with acute coronary syndrome (ACS). Pretreatment with antibody against FcγRII or with CD32 siRNA, p47(phox) siRNA, apocynin, N-acetylcysteine, tumor necrosis factor-α protease inhibitor 1 (TAPI-1) or TACE siRNA attenuated sLOX-1 release induced by CRP. CRP also elevated serum sLOX-1 levels in a rabbit model of atherosclerosis. Thus, CRP might stimulate sLOX-1 release, and the underlying mechanisms possibly involved FcγRII-mediated p47(phox) phosphorylation, ROS production, and TACE activation.

Attenuated Combined Action of Cyclosporine A and Hyperlipidemia on Atherogenesis in Rabbits by Thymoquinone

This descriptive study investigates in a rabbit model of atherosclerosis (i) the extent of atherogenesis induced by cyclosporine A (CsA) or hyperlipidemia alone or in combination and (ii) whether thymoquinone (TQ), a known herbal antioxidant, offers protection against these effects. New Zealand White female rabbits were assigned to five groups of six animals each: Group I, control; Group II, CsA [25 mg kg−1 day−1 orally (PO)]; Group III, 1% cholesterol; Group IV, 1% cholesterol + CsA (25 mg kg−1 day−1 PO); and Group V, 1% cholesterol + CsA (25 mg kg−1 day−1 PO) + TQ (10 mg kg−1 day−1 PO). Lipids and oxidative stress parameters [Malondialdehyde (MDA) and protein carbonyl] and aortic atherosclerosis were compared. CsA alone did not show a significant effect on either serum lipids and did not induce atherosclerosis. High-cholesterol diet induced atherosclerosis (45 ± 11% of the intimal surface of aorta was covered with atherosclerotic plaques). CsA and high-cholesterol diet increased atherosclerosis severity as measured from intimal and media lesions, but did not affect the extent of atherosclerosis. TQ decreased aortic MDA by 83%. It was also associated with reduced aortic atherosclerosis extend by 52% compared with Group IV. We concluded that (i) CsA aggravates hyperlipidemia-induced atherosclerosis and (ii) TQ attenuates the oxidative stress and atherogenesis induced by the combined effect of CsA and hyperlipidemia.

Flat-panel versus 64-channel computed tomography for in vivo quantitative characterization of aortic atherosclerotic plaques

BackgroundFlat-panel computed tomography (FpCT) provides better spatial resolution than 64-channel CT (64-CT) and may improve in vivo quantitative assessment of atherosclerotic plaques. Methods and resultsLesions in 184 aortic histology sections from 6 Watanabe heritable hyperlipidemic rabbits were quantitatively compared with 64-CT (image thickness, 0.625mm) and FpCT (image thickness, 0.150mm) images. Images were re-oriented perpendicular to the vessel centerline. For detecting plaque, FpCT and 64-CT were not significantly different (sensitivity, 76% vs 66%; P=NS). Although FpCT was significantly more sensitive (42% vs 0%; P=<0.001) for detecting eccentric lesions, the area under the curve (AUC) for FpCT (0.6) was not significantly different from that for 64-CT (0.45; P=NS). In detecting plaques with ≤10% lipid (low attenuation foci), FpCT was significantly more sensitive than 64-CT (24% vs 0.7%; P<0.00) and had a significantly greater AUC (0.6 vs 0.5; P<0.006). Additionally, FpCT was more sensitive (65% vs 0%; P<0.00) in detecting plaques with ≤5% calcium (high attenuation foci) but not in detecting branch points. Both FpCT and histology allowed us to detect low-attenuation foci as small as 0.3mm in diameter, whereas 64-CT allowed us to detect only low-attenuation foci ≥1.5mm in diameter. ConclusionsFlat-panel CT seemed to have more potential for quantitatively screening low-risk small atherosclerotic lesions, whereas 64-CT was apparently more useful when imaging established, well-characterized lesions, particularly when measuring the vascular wall thickness in a rabbit model of atherosclerosis.

Multimodal Clinical Imaging To Longitudinally Assess a Nanomedical Anti-Inflammatory Treatment in Experimental Atherosclerosis

Atherosclerosis is an inflammatory disease causing great morbidity and mortality in the Western world. To increase the anti-inflammatory action and decrease adverse effects of glucocorticoids (PLP), a nanomedicinal liposomal formulation of this drug (L-PLP) was developed and intravenously applied at a dose of 15 mg/kg PLP to a rabbit model of atherosclerosis. Since atherosclerosis is a systemic disease, emerging imaging modalities for assessing atherosclerotic plaque are being developed. (18)F-Fluoro-deoxy-glucose positron emission tomography and dynamic contrast enhanced magnetic resonance imaging, methods commonly used in oncology, were applied to longitudinally assess therapeutic efficacy. Significant anti-inflammatory effects were observed as early as 2 days that lasted up to at least 7 days after administration of a single dose of L-PLP. No significant changes were found for the free PLP treated animals. These findings were corroborated by immunohistochemical analysis of macrophage density in the vessel wall. In conclusion, this study evaluates a powerful two-pronged strategy for efficient treatment of atherosclerosis that includes nanomedical therapy of atherosclerotic plaques and the application of noninvasive and clinically approved imaging techniques to monitor delivery and therapeutic responses. Importantly, we demonstrate unprecedented rapid anti-inflammatory effects in atherosclerotic lesions after the nanomedical therapy.

Detection of Macrophages Via Paramagnetic Vesicles Incorporating Oxidatively Tailored Cholesterol Ester: An Approach for Atherosclerosis Imaging

Macrophages play a key role in the initiation, progression and complications of atherosclerosis. In this article we describe the synthesis of biocompatible, paramagnetic, fluorescent phosphatidylserine vesicles containing cholesterol ester with a free carboxylic acid function and its use for targeted imaging of macrophages. We synthesized anionic vesicles containing a combination of phosphatidylserine and a novel synthetic oxidized cholesterol ester derivative (cholesterol-9-carboxynonanoate [9-CCN]). In vitro studies to characterize particle size, MRI relaxation times and stability were performed. Vesicles containing 9-CCN demonstrated enhanced ability to bind human low-density lipoprotein and to be internalized by macrophages. Experiments in cultured macrophages with 9-CCN vesicles, alone and in the presence of low-density lipoprotein, indicated uptake of vesicles through scavenger receptor and integrin-dependent pathways. In vivo MRI using 9-CCN vesicles containing gadolinium in a rabbit model of atherosclerosis revealed protracted enhancement of 9-CCN vesicles and colocalization with arterial macrophages not seen with control vesicles. Pharmacokinetic experiments demonstrated prolonged plasma residence time of 9-CCN vesicles, perhaps due to its capacity to bind to low-density lipoprotein. Vesicles containing 9-CCN demonstrate prolonged plasma and plaque retention in experimental atherosclerosis. Such a strategy may represent a simple yet clinically relevant approach for macrophage imaging.

Effects of immunomodulatory drugs on plasma inflammatory markers in a rabbit model of atherosclerosis

Atherosclerosis is a chronic disease of the arterial wall where both innate and adaptive immuno-inflammatory mechanisms are involved. Inflammatory cytokines are implicated in the development and progression of atherosclerotic lesions. Immunomodulatory therapies have been proposed for the treatment of atherosclerosis. Therefore, the aim of this study was to investigate the systemic anti-inflammatory and immunomodulatory effects of atorvastatin, cyclosporine A (CsA), and tacrolimus (FK506) on plasma inflammatory markers in atherosclerotic rabbits. Male New Zealand rabbits were randomized into five groups each of 12 animals. Standard diet-fed group served as control, and the cholesterol-fed group received a diet supplemented with 1% cholesterol alone, cholesterol + atorvastatin, cholesterol + FK506, and cholesterol + CsA. Serum levels of lipid profile parameters (triglycerides, cholesterol, and high-density lipoprotein) were measured using colorimetric methods. Serum levels of C-reactive protein (CRP), interleukin-6 (Il-6), and interferon-gamma (INF-γ) were measured in all studied groups using ELISA techniques. Our results revealed a significant decrease (p < 0.001) in the serum levels of lipid profile parameters, CRP, Il-6, and INF-γ in atorvastatin-treated group compared with the cholesterol-fed group. On the other hand, a non-significant difference was observed for the same parameters in either FK506- or CsA-treated groups compared with the cholesterol-fed group. In conclusion, atorvastatin has a systemic anti-inflammatory role that far surpassed the cholesterol reduction effect alone. FK506 or CsA failed to suppress elevated plasma inflammatory markers. Thus, low doses of these two immunomodulating drugs could not have generalized systemic anti-inflammatory or immunosuppressive effects.

Differential effect of Pistacia vera extracts on experimental atherosclerosis in the rabbit animal model: an experimental study

BackgroundLipid-enriched diets and oxidative stress are risk factors for the development of atherosclerosis. The effects of the methanolic (ME) and cyclohexane (CHE) extracts of the Pistacia vera nut, often included in the Mediterranean diet, were studied in the rabbit model of atherosclerosis.Methods and resultsTwenty-four New Zealand White rabbits received atherogenic diet (Control Group), supplemented with ME (Group ME) or CHE (Group CHE) for 3 months. Previously, a GC-MS and a UHPLC LC-DAD-ESI(-)-HRMS/MS method were developed to investigate the extracts' chemical profiles. Blood samples at baseline and monthly determined lipid profile, lipid peroxidation and liver function. The aorta, myocardium and liver were examined histologically at 3 months.Groups ME and CHE had significantly higher HDL- and non-significantly lower LDL-cholesterol median % changes from baseline than the Control Group. Triacylglycerol was significantly higher in Group CHE vs. Control. MDA values were significantly lower in Group ME vs. Control and CHE. ALT and AST were significantly higher in Group CHE vs. Control. γ-GT was lower in Group ME vs. Control. Aortic intimal thickness was significantly less in Groups ME and CHE vs. Control; Group ME atherosclerotic lesions were significantly less extensive vs. Groups Control and CHE. Only Group CHE had significant liver fatty infiltration.ConclusionsDuring short-term administration concomitantly with atherogenic diet, both P. vera extracts were beneficial on HDL-, LDL-cholesterol and aortic intimal thickness. The ME additionally presented an antioxidant effect and significant decrease of aortic surface lesions. These results indicate that P. vera dietary inclusion, in particular its ME, is potentially beneficial in atherosclerosis management.

Effects of Clopidogrel on Vascular Proliferation and Apoptosis in an Atherosclerotic Rabbit Model

Inflammation, vascular proliferation. and apoptosis contribute to the process of atherosclerosis. Clopidogrel has been used to treat atherosclerosis; however, the mechanism is not entirely known. Compared with those of atorvastatin, we determined effects of clopidogrel on inflammatory factors, vascular proliferation, and apoptosis in an atherosclerosis rabbit model. New Zealand white rabbits were fed a normal diet or a high cholesterol diet for 7 weeks. The right iliac artery of animals except those in the negative control group were balloon-injured 1 week after initiation of the diet, and groups of animals were treated with clopidogrel (4 mg/kg per day), atorvastatin (2.5 mg/kg per day), or placebo (positive control group) for 6 weeks. We found that the placebo group had significant progression of atherosclerosis compared with the negative control group. In contrast, clopidogrel- or atorvastatin-treated rabbits showed a significant reduction in progression of atherosclerosis, including a low expression of high sensitivity C-reactive protein and platelet-derived growth factor, a reduced intima thickness, and reduced ratio of bcl-2/bax in the vascular wall. These results suggest that clopidogrel can retard the progression of established lesions that is related to inhibiting inflammation, cell proliferation, and promotion of cell apoptosis.

Anti-atherogenic effect of BHB-TZD having inhibitory activities on cyclooxygenase and 5-lipoxygenase in hyperlipidemic mice

Cyclooxygenase (COX) and 5-lipoxygenase (5-LOX), which play pivotal roles in atherogenesis, have been reported to be involved in plaque stability. Licofelone, a dual COX and 5-LOX inhibitor, has been reported to possess anti-atherogenic effect in rabbit atherosclerosis model. We therefore investigated the anti-atherogenic effect of BHB-TZD [5-(3,5-di-tert-butyl-4-hydroxybenzylidene)thiazolidin-2,4-dione], a dual COX and 5-LOX inhibitor, in low density lipoprotein receptor null (LDLR−/−) mice. Fifteen LDLR−/− mice were fed a western diet (control group), whereas 15 were fed a western diet plus 0.1% (w/w) BHB-TZD (BHB-TZD group). After 8 weeks, the BHB-TZD group had markedly lower serum levels of leukotriene B4 and prostaglandin E2 than the control group. Interestingly, BHB-TZD treatment also reduced plasma triglyceride level without significant changes in total cholesterol and HDL levels. Compared with control mice, BHB-TZD fed mice had 52% fewer fatty streak lesions in the aortic sinus, as well as fewer initial lesions in the aortic arch. Macrophage infiltration into the lesions was 40% lower, and collagen and smooth muscle cells were increased by 102% and 96%, respectively, in the BHB-TZD group compared with the control group. In addition, aortic expression of proatherogenic molecules including TNF-α, IL-1β, IL-6, MCP-1 and VCAM-1, was lower in the BHB-TZD group than the control group. BHB-TZD treatment also reduced MMP-2 and MMP-9 expressions in aorta. In conclusion, BHB-TZD effectively attenuated atherosclerosis in mouse model, suggesting its therapeutic potential for atherosclerosis.

Atherosclerosis induced by chronic inhibition of the synthesis of nitric oxide in moderately hypercholesterolaemic rabbits is suppressed by pitavastatin

It is not clear if the new 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor pitavastatin prevents atherogenesis by a direct effect. Statins have a cholesterol-lowering effect, so an accessible animal model of atherosclerosis showing only moderate hypercholesterolaemia as in humans, is needed. The effects of pitavastatin were evaluated on atherosclerotic lesions accumulating foam cells derived from macrophages, produced in rabbits with moderate hypercholesterolaemia by chronic inhibition of nitric oxide synthase (NOS). White New Zealand rabbits were fed a 0.2% cholesterol diet with the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) in the same diet. Pitavastatin (0.1 and 0.3 mg x kg(-1)) was given orally once a day for 8 weeks. The aortic arch and thoracic aorta were analysed by histochemistry and atherosclerotic lesions were quantified. The effect of pitavastatin on adhesion of THP-1 cells to endothelial cells, and cholesterol content in RAW264.7 cells incubated with oxidized or acetylated LDL were also investigated. Atherosclerotic lesions containing foam cells were induced in a model of atherosclerosis in rabbits with moderate hypercholesterolaemia by chronic inhibition of NOS. The area of atherosclerotic lesions was diminished by pitavastatin administration. The adhesion of THP-1 cells and cholesteryl ester content in RAW macrophages were decreased by pitavastatin treatment. Atherosclerosis induced by chronic inhibition of NOS in moderately hypercholesterolaemic rabbits was suppressed by pitavastatin via inhibition of macrophage accumulation and macrophage foam cell formation.

The changes in the endothelial expression of cell adhesion molecules and iNOS in the vessel wall after the short-term administration of simvastatin in rabbit model of atherosclerosis

Cell adhesion molecules P-selectin, VCAM-1 and ICAM-1 play an important role in the pathogenesis of atherosclerosis. High levels of nitric oxide (NO) produced by inducible NO synthase (iNOS) have been associated with atherosclerotic processes. Simvastatin is an HMG-CoA reductase inhibitor responsible for many clinical benefits. The aim of this study was to detect and quantify changes in endothelial expression of P-selectin, VCAM-1, ICAM-1 and iNOS in the vessel wall after the shortterm administration of simvastatin in a rabbit model of atherosclerosis. Eighteen New Zealand White rabbits were randomly divided into three groups (n=6). In the cholesterol group, rabbits consumed an atherogenic diet (0.4% cholesterol) for eight weeks. In the simvastatin group, rabbits consumed an atherogenic diet for six weeks and then consumed an atherogenic diet supplemented with simvastatin (10 mg kg(-1)) for two weeks. Biochemical analysis showed that administration of simvastatin led to an almost two-fold lowering of the total serum cholesterol, VLDL, LDL and HDL, but not triglycerides, compared with the cholesterol-fed rabbits only. Stereological analysis of the immunohistochemical staining revealed that administration of simvastatin (10 mg kg(-1) daily) in an atherogenic diet decreased the endothelial expression of P-selectin, ICAM-1 and iNOS in both aortic arch and carotid artery compared with the cholesterol fed-rabbits only. We conclude that simvastatin has beneficial effects on endothelial function by decreasing expression of P-selectin, ICAM-1 and iNOS in endothelial cells in the very early stages of atherogenesis.

Peak radial and circumferential strain measured by velocity vector imaging is a novel index for detecting vulnerable plaques in a rabbit model of atherosclerosis

AimsTo evaluate the reliability of velocity vector imaging (VVI) for detecting vulnerable plaques. Methods and ResultsAfter aortic balloon injury, 60 rabbits were fed a 1% cholesterol diet for 10 weeks and normal chow for another 6 weeks. Adenovirus containing p53 or lac Z was then injected into the aortic plaques and rabbits were divided into p53-treated group (n=20), lac Z-treated group (n=20) and blank control group (n=20). Peak longitudinal (LSp), radial (RSp) and circumferential (CSp) strain of plaques was measured using VVI at the end of week 18 before pharmacological triggering. Higher RSp and CSp and lower LSp were found in ruptured than those in non-ruptured plaques, and RSp, CSp and LSp correlated well with the fibrous cap thickness and plaque content of macrophages, smooth muscle cells and collagen (all p<0.01). A logistic regression model showed that both RSp (RR: 8.96, 95% CI: 5.3575–10.4857, p<0.001) and CSp (RR: 8.45, 95% CI: 5.9043–9.1043, p<0.001) were significant predictors of plaque rupture. RSp and CSp had a sensitivity of 88.0% and 88.6% and a specificity of 88.6% and 92.0% to predict plaque disruption, respectively. ConclusionVVI offers a new and noninvasive technique for measuring the peak strain of atherosclerotic plaques and RSp and CSp are a novel index with a high sensitivity and specificity for detecting plaques vulnerable to rupture.

7-Difluoromethyl-5,4′-dimethoxygenistein, a Novel Genistein Derivative, Has Therapeutic Effects on Atherosclerosis in a Rabbit Model

Genistein is a phytoestrogen that is known to have a protective effect on the vascular endothelial wall. However, it exhibits poor bioavailability, which limits the use of genistein to treat cardiovascular and cerebrovascular diseases. A novel genistein derivative, 7-difluoromethyl-5,4'-dimethoxygenistein (dFMGEN), has shown a better protective effect on vascular endothelial damage in vitro than genistein. In this study, we further evaluated therapeutic effects of dFMGEN on the vascular endothelial wall and atherosclerosis in a rabbit model in vivo. There were 5 groups: the GEN group (genistein 5 mg/kg per day), lovastatin group (lovastatin 5 mg/kg per day), dFMGEN group (dFMGEN 5 mg/kg per day), model control group (the same amount of vehicle solvent), and the normal control group; all feedings administered via intragastric administration. We demonstrated that dFMGEN (1) attenuated the development of atherosclerosis, (2) reduced serum total cholesterol and low-density lipoprotein cholesterol concentrations, (3) decreased lipid peroxidation in the rabbit atherosclerosis model, and (4) increased smooth muscle cell and collagen content in atheroma of thoracic aortas. These results provide an experimental foundation for dFMGEN's potential effects in preventing and treating atherosclerosis, acute coronary syndromes, and potentially ischemia-reperfusion injury during acute myocardial infarction and cerebral infarction.

FDG–PET can distinguish inflamed from non-inflamed plaque in an animal model of atherosclerosis

The presence of activated macrophages is an important predictor of atherosclerotic plaque rupture. In this study, our aim was to determine the accuracy of (18)F- fluorodeoxyglucose (FDG) microPET imaging for quantifying aortic wall macrophage content in a rabbit model of atherosclerosis. Rabbits were divided into a control group and two groups post aortic balloon injury: 6 months high-cholesterol diet (HC); and 3 months HC followed by 3 months low-cholesterol diet plus statin (LCS). In vivo and ex vivo microPET, ex vivo well counting and histological quantification of the atherosclerotic aortas were performed for all groups. Macrophage density was greater in the HC group than the LCS group (5.1 +/- 1.4% vs. 0.6 +/- 0.7%, P < 0.001) with a trend towards greater macrophage density in LCS compared to controls (P = 0.08). There was a strong correlation across all groups between macrophage density and standardized uptake value (SUV) derived from ex vivo microPET (r = 0.95, P < 0.001) and well counting (r = 0.96, P < 0.001). Ex vivo FDG SUV was significantly different between the three groups (P < 0.001). However, the correlation between in vivo microPET FDG SUV and macrophage density was insignificant (r = 0.16, P = 0.57) with no statistical differences in FDG SUV seen between the three groups. This study confirms that in an animal model of inflamed and non-inflamed atherosclerosis, significant differences in FDG SUV allow differentiation of highly inflamed atherosclerotic aortas from those stabilized by statin therapy and low cholesterol diet and controls.

Small Multifunctional Nanoclusters (Nanoroses) for Targeted Cellular Imaging and Therapy

The ability of 20-50 nm nanoparticles to target and modulate the biology of specific types of cells will enable major advancements in cellular imaging and therapy in cancer and atherosclerosis. A key challenge is to load an extremely high degree of targeting, imaging, and therapeutic functionality into small, yet stable particles. Herein we report approximately 30 nm stable uniformly sized near-infrared (NIR) active, superparamagnetic nanoclusters formed by kinetically controlled self-assembly of gold-coated iron oxide nanoparticles. The controlled assembly of nanocomposite particles into clusters with small primary particle spacings produces collective responses of the electrons that shift the absorbance into the NIR region. The nanoclusters of approximately 70 iron oxide primary particles with thin gold coatings display intense NIR (700-850 nm) absorbance with a cross section of approximately 10(-14) m(2). Because of the thin gold shells with an average thickness of only 2 nm, the r(2) spin-spin magnetic relaxivity is 219 mM(-1) s(-1), an order of magnitude larger than observed for typical iron oxide particles with thicker gold shells. Despite only 12% by weight polymeric stabilizer, the particle size and NIR absorbance change very little in deionized water over 8 months. High uptake of the nanoclusters by macrophages is facilitated by the dextran coating, producing intense NIR contrast in dark field and hyperspectral microscopy, both in cell culture and an in vivo rabbit model of atherosclerosis. Small nanoclusters with optical, magnetic, and therapeutic functionality, designed by assembly of nanoparticle building blocks, offer broad opportunities for targeted cellular imaging, therapy, and combined imaging and therapy.

Validation of in vivo plaque characterisation by virtual histology in a rabbit model of atherosclerosis

Most acute coronary syndromes are caused by plaque rupture. The risk of plaque rupture is related to plaque composition. The purpose of this study was to validate VH-IVUS for in vivo plaque characterisation. Six rabbits were fed a cholesterol-supplemented diet for 12 to 18 months. Thereafter, VH-IVUS imaging of the aorta was performed. After sacrifice, the VH-IVUS images were matched to the corresponding histological cross sections. A total of 260 atherosclerotic plaques were analysed. VH-IVUS had a high sensitivity, specificity and positive predictive value for the detection of non-calcified thin cap fibroatheroma (88%, 96%, 87%, respectively) and calcified thin cap fibroatheroma (95%, 99%, 93%, respectively). These values were respectively 82%, 94%, 85% for non-calcified fibroatheroma and 78%, 98%, 84% for calcified fibroatheroma. The lowest values were obtained for pathological intimal thickening (74%, 92%, 70%, respectively). For all plaque types, VH-IVUS had a kappa-value of 0.79. Linear regression analysis and Bland-Altman plots showed a strong correlation between VH-IVUS and histology for fibrous tissue, fibrofatty tissue, necrotic calcified tissue and confluent necrotic core. VH-IVUS showed a good accuracy for in vivo plaque characterisation and is a promising technique for the detection of the vulnerable plaque.

Ezetimibe – new anti‐atherogenic properties?

Ezetimibe, a Niemann Pick C1-like1 inhibitor, inhibits cholesterol absorption. The drug has been shown to affect lipid raft function in monocytes and therefore may inhibit lipid accumulation in the atheromatous plaque with a mechanism that is unrelated to its effect in reducing cholesterol absorption. In this issue of the British journal of pharmacology, Gómez-Garre et al. demonstrate that ezetimibe and simvastatin both have a beneficial effect on the atheromatous plaque, which may be due to their effect on both monocyte/macrophage function and reduction in nuclear factor-kappaB activity. Whether these results in a rabbit model of atherosclerosis can be translated into human atherosclerosis awaits further studies.

Ezetimibe reduces plaque inflammation in a rabbit model of atherosclerosis and inhibits monocyte migration in addition to its lipid‐lowering effect

Ezetimibe, a selective inhibitor of intestinal cholesterol absorption, might also suppress inflammatory components of atherogenesis. We have studied the effects of ezetimibe on two characteristics of atherosclerotic plaques (infiltrate and fibrosis) and on expression of inflammatory genes in a rabbit model of accelerated atherosclerosis. Femoral atherosclerosis was induced by a combination of endothelial desiccation and atherogenic diet. Animals were randomized to ezetimibe (0.6 mg x kg(-1) x day(-1)), simvastatin (5 mg x kg(-1) x day(-1)), ezetimibe plus simvastatin or no treatment, still on atherogenic diet. A control group of rabbits received normolipidemic diet. Rabbits fed the normolipidemic diet showed normal plasma lipid levels. Either the normolipidemic diet or drug treatment reduced the intima/media ratio (normolipidemic diet: 22%, ezetimibe: 13%, simvastatin: 27%, ezetimibe + simvastatin: 28%), compared with rabbits with atherosclerosis. Ezetimibe also decreased macrophage content and monocyte chemoattractant protein-1 expression in atherosclerotic lesions. Furthermore, ezetimibe reduced the increased activity of nuclear factor kappaB in peripheral blood leucocytes and plasma C-reactive protein levels in rabbits with atherosclerosis. In THP-1 cells, ezetimibe decreased monocyte chemoattractant protein-1-induced monocyte migration. Importantly, the combination of ezetimibe with simvastatin was associated with a more significant reduction in plaque monocyte/macrophage content and some proinflammatory markers than observed with each drug alone. Ezetimibe had beneficial effects both on atherosclerosis progression and plaque stabilization and showed additional anti-atherogenic benefits when combined with simvastatin. Its effect on monocyte migration provides a potentially beneficial action, in addition to its effects on lipids.

Simple Rabbit Model of Vulnerable Atherosclerotic Plaque

The present study investigated the appropriate conditions for induction of lesions in the rabbit atherosclerosis model. Four-week-old male Japanese white rabbits (n = 19) were fed the high cholesterol diet (HCD). This group was classified as the early start (ES) group. The animals were divided into three groups: (i) 1% HCD group (n = 8), (ii) 2% HCD group (n = 8), and (iii) normal diet group (control, n = 3). The HCD groups were divided into two subgroups: (a) balloon injury (BI) group (1% HCD, n = 5; 2% HCD, n = 4), and (b) non-BI group (1% HCD, n = 3; 2% HCD, n = 4). Survival period, histological characteristics, area of plaque, and effects of BI and diet cholesterol content were analyzed. Twelve-week-old male Japanese white rabbits (n = 8) were fed the 1% HCD. This group was classified as the late start (LS) group, and underwent BI in the aorta. The histological characteristics and area of plaque were investigated. The plaque satisfied the three requirements of vulnerable plaque: Lipid rich core, accumulation of macrophages, and thin fibrous cap. The plaque area was significantly greater in the ES group compared to the LS group (p = 0.0037). Survival analysis found no statistical correlation with BI or diet cholesterol content. This study indicates that the simplest conditions for inducing the rabbit atherosclerosis model are 1% HCD, non-BI, and early start of HCD. This model is suitable for experiments with new therapeutic devices.