WHHL Rabbits Research Articles

Synthetic Flavonoid 3,7-Dihydroxy-Isoflav-3-Ene (DHIF) Reduces In-Stent Restenosis in an Atherosclerotic Watanabe Heritable Hyperlipidemic Rabbit Stent Model.

Inflammation is a major component of the pathogenesis of atherosclerosis and the formation of in-stent restenosis (ISR). A novel flavonoid, DHIF, attenuates reactive oxygen species and nf-κB signaling and has potential to limit ISR via antioxidant action. While current drug eluting stents (DESs) perform well in clinical practice, new therapies to prevent ISR without dependance on cytotoxic drugs are warranted. Our objective was to test whether DHIF reduces ISR in a hyperlipidemic rabbit aorta model of ISR via attenuated inflammatory responses. WHHL rabbit aortas (n = 24) were denuded. Six weeks after injury, stents were implanted into the denuded aortas. DHIF was dissolved in carboxymethyl cellulose (CMC) and administered orally with two doses. CMC served as a control. The animals were sacrificed six weeks after stenting. ISR was evaluated from stent histomorphometry and immunohistology was used to assess the inflammatory and antiproliferative effects of the treatment. ISR was reduced from 20.9 ± 3.0% in controls to 15.2 ± 2.4% (p = 0.0009) and 16.4 ± 2.1% (p = 0.004) in the low- and high-dose groups, respectively. The neointimal area covered by macrophages was 32 ± 9.3% in the controls, 17.2 ± 5.9% (p = 0.005) in the low-dose group and 19.4 ± 7.9% (p = 0.008) in the high-dose group. DHIF significantly reduces ISR and local inflammation in stented arterial regions and could be used to reduce ISR when bare metal stents are used. Targeting local inflammation in the arterial wall may provide a way to reduce ISR in a clinical setting and further studies are warranted.

Non-Mouse Models of Atherosclerosis: Approaches to Exploring the Translational Potential of New Therapies

Cardiovascular disease is the largest single cause of disease-related mortality worldwide and the major underlying pathology is atherosclerosis. Atherosclerosis develops as a complex process of vascular lipid deposition and retention by modified proteoglycans, endothelial dysfunction and unresolved chronic inflammation. There are a multitude of current therapeutic agents, most based on lowering plasma lipid levels, but, overall, they have a lower than optimum level of efficacy and many deaths continue to arise from cardiovascular disease world-wide. To identify and evaluate potential novel cardiovascular drugs, suitable animal models that reproduce human atherosclerosis with a high degree of fidelity are required as essential pre-clinical research tools. Commonly used animal models of atherosclerosis include mice (ApoE-/-, LDLR-/- mice and others), rabbits (WHHL rabbits and others), rats, pigs, hamster, zebrafish and non-human primates. Models based on various wild-type and genetically modified mice have been extensively reviewed but mice may not always be appropriate. Thus, here, we provide an overview of the advantages and shortcomings of various non-mouse animal models of atherosclerotic plaque formation, and plaque rupture, as well as commonly used interventional strategies. Taken together, the combinatorial selection of suitable animal models readily facilitates reproducible and rigorous translational research in discovering and validating novel anti-atherosclerotic drugs.

Effects of chronic mirabegron treatment on metabolic and cardiovascular parameters as well as on atherosclerotic lesions of WHHL rabbits with high-fructose high-fat diet-induced insulin resistance.

Background and aimMetabolic syndrome (MetS) is a global health and economic burden. Finding a suitable pharmacological approach for managing this syndrome is crucial. We explored the therapeutic potential of mirabegron (MIR), a β3-adrenergic receptor agonist, as a repurposed agent for the treatment of MetS and its cardiovascular consequences. MethodsThirty Watanabe heritable hyperlipidemic rabbits (WHHL) were divided into 3 groups: control, high-fructose high-fat diet (HFFD) and HFFD + MIR that received a chow diet, HFFD and HFFD along with MIR treatment, respectively. The protocol lasted for 12 weeks, during which weight and abdominal circumference were monitored; plasma fasting levels of lipids, glucose and insulin were measured and an intravenous glucose tolerance test (IVGTT) was performed. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Cardiac function was assessed using in-vivo and ex-vivo approaches. Vascular reactivity was estimated via isolated carotid arteries method. Aortic atherosclerosis was evaluated using histological and immuno-histochemical techniques. ResultsIn contrast to the HFFD group, MIR-treated rabbits showed fasting insulin, HOMA-IR and TG levels stabilization and exhibited improved cardiac inotropy and lusitropy, while on the other hand, displayed aggravated atheroma plaque development. ConclusionLong-term treatment with MIR prevented the increase in TG levels and the establishment of IR and enhanced the cardiac function of a rabbit animal model of MetS with combined dyslipidemia and IR.

EXPERIMENTAL MODELS OF THE ATHEROSCLEROSIS ON RABBITS

Atherosclerosis is the main cause of cardiovascular diseases, which, despite a number of new advances in their diagnosis and treatment, still occupy a leading position. Experimental modeling of atherosclerosis in laboratory animals plays an important role in the study of the fundamental pathophysiological processes and pathology of atherosclerosis. Rabbits are among the most suitable animals for simulating atherosclerosis, as they are widely available, inexpensive to maintain, and easy to manipulate. The key advantage of rabbits over other animals is that their lipid metabolism is practically similar to that of humans. The aim of the study was to analyze literature data on experimental models of atherosclerosis in rabbits. The review shows that the history of the study of atherosclerosis by means of experimental models is very rich and originates from the works of the well-known Russian pathologists A.I. Ignatovsky, N.N. Anichkov, S.S. Khalatov (1908-1915), who developed a cholesterol model of the formation of atherosclerosis in rabbits. The principle of this model is to feed laboratory animals with food containing elevated levels of lipids and cholesterol. The composition of the cholesterol (atherogenic) diet may vary, determining the existence of modifications of this model. Most often, a diet with a cholesterol content of 0.3-0.5% is used, in cases where it is necessary to accelerate the development of atherosclerosis, a short-term use of a diet with a 1% cholesterol content is allowed. In addition to cholesterol, it is recommended to use vegetable oils (soybean, coconut or corn) in the atherogenic diet as they improve the absorption of cholesterol in the intestine. In 1980, Japanese researcher Y. Watanabe deduced a new model of atherosclerosis formation - on hereditarily determined hyperlipidemic rabbits Watanabe (WHHL-rabbits). WHHL rabbits contain a genetic mutation in the gene encoding low-density lipoprotein receptors, which results in these animals having high plasma cholesterol levels with a normal diet. Thanks to modern genetic technologies, various genetic models of atherosclerosis in rabbits have also been created: transgenic and “knocked out” rabbits. The main method for obtaining transgenic rabbits is pronuclear microinjection, which allows the introduction of a transgene (additional DNA fragment) into their genome. To date, using this technology, it has been possible to introduce more than a dozen genes responsible for lipid metabolism. The principle of creating knocked out rabbits consists in specific inactivation using genome editing technologies (ZFN, TALEN, CRISPR / Cas9) of a certain working gene. Experimental models of atherosclerosis in rabbits have not lost their significance and continue to be used to study the fundamental morphological (pathological) and pathological mechanisms underlying atherosclerosis, to search for new diagnostic biomarkers and potential targets for therapeutic effects, as well as to conduct preclinical trials of newly developed drugs.

The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (II) - Contribution to the Development and Validation of the Therapeutics for Hypercholesterolemia and Atherosclerosis.

A number of effective drugs have been developed through animal experiments, contributing to the health of many patients. In particular, the WHHL rabbit family (WHHL rabbits and its advanced strains (coronary atherosclerosis-prone WHHL-CA rabbits and myocardial infarction-prone WHHLMI rabbits) developed at Kobe University (Kobe, Japan) contributed greatly in the development of cholesterol-lowering agents. The WHHL rabbit family is animal models for human familial hypercholesterolemia, coronary atherosclerosis, and coronary heart disease. At the end of breeding of the WHHL rabbit family, this review summarizes the contribution of the WHHL rabbit family to the development of lipid-lowering agents and anti-atherosclerosis agents. Studies using the WHHL rabbit family demonstrated, for the first time in the world, that lowering serum cholesterol levels or preventing LDL oxidation can suppress the progression and destabilization of coronary lesions. In addition, the WHHL rabbit family contributed to the development of various compounds that exhibit lipid-lowering and anti-atherosclerotic effects and has also been used in studies of gene therapeutics. Furthermore, this review also discusses the causes of the increased discrepancy in drug development between the results of animal experiments and clinical studies, which became a problem in recent years, and addresses the importance of the selection of appropriate animal models used in studies in addition to an appropriate study design.

The Effect Of Soluble Guanylate Cyclase (Sgc) And Beta3-Adrenoceptor Activation On The Circulatory Function Of Watanabe Heritable Hyperlipidemic (Whhl) Rabbits

Background and Aims: Our hypothesis is that modulating the cellular level of cyclic guanosine monophosphate pathway could restore the circulatory function and decrease the Metabolic Syndrome-induced adverse effects. Our objective is to evaluate the effect of a long-term treatment with a direct activator of the sGC (BAY-412272) and a β3-adrenoceptor agonist (Mirabegron) on the metabolic and circulatory parameters of the WHHL rabbit, an animal model of dyslipidemia.

Macrophage-targeted, enzyme-triggered fluorescence switch-on system for detection of embolism-vulnerable atherosclerotic plaques

The development of atherosclerotic plaques is a critical step that can result in an arterial embolism. Therefore, detection of these vulnerable plaques is of clinical significance for the diagnosis of atherosclerosis. However, there are few imaging systems able to detect such plaques easily. In this study, we designed a new platform for near-infrared fluorescence (NIRF) imaging of macrophages in atherosclerotic plaques, one using both a liposomal DDS and an activatable fluorescent probe, and evaluated the utility of this imaging for the diagnosis of atherosclerosis. We first synthesized a fluorescent switch-on probe, Peptide-ICG2, which is optically silent under normal conditions but activated in the presence of the lysosomal enzyme, cathepsin B. To achieve macrophage-specific fluorescence activation, we encapsulated Peptide-ICG2 into phosphatidylserine-containing liposome (P-ICG2-PS-Lip), since the accumulation of phosphatidylserine receptor-bearing macrophages is characteristic of embolism-vulnerable plaques. The experiments using macrophage-like RAW264 cells in culture showed that P-ICG2-PS-Lip was selectively taken up into the cells and that significant fluorescence of the probe was observed. For NIRF imaging of the atherosclerotic plaques, P-ICG2-PS-Lip was intravenously injected into ApoE-knockout atherosclerotic model mice or WHHL rabbits, and the fluorescence at the aortae was imaged. The results indicated that ICG fluorescence could be successfully observed at the plaques on the artery walls. The results of the present study thus suggest that NIRF imaging using P-ICG2-PS-Lip would be useful for detecting embolism-vulnerable atherosclerotic plaques.

In Vivo Translation of the CIRPI System: Revealing Molecular Pathology of Rabbit Aortic Atherosclerotic Plaques.

Thin-cap fibroatheroma (TCFA) are the unstable lesions in coronary artery disease that are prone to rupture, resulting in substantial morbidity and mortality worldwide. However, their small size and complex morphologic and biologic features make early detection and risk assessment difficult. We tested our newly developed catheter-based Circumferential-Intravascular-Radioluminescence-Photoacoustic-Imaging (CIRPI) system in vivo to enable detection and characterization of vulnerable plaque structure and biology in rabbit abdominal aorta. Methods: The CIRPI system includes a novel optical probe combining circumferential radioluminescence imaging and photoacoustic tomography (PAT). The probe's CaF2:Eu-based scintillating imaging window captures radioluminescence images (360° view) of plaques by detecting β-particles during 18F-FDG decay. A tunable laser-based PAT characterizes tissue constituents of plaque at 7 different wavelengths-540 and 560 nm (calcification), 920 nm (cholesteryl ester), 1040 nm (phospholipids), 1180 nm (elastin/collagen), 1210 nm (cholesterol), and 1235 nm (triglyceride). A single B-scan is concatenated from 330 A-lines captured during a 360° rotation. The abdominal aorta was imaged in vivo in both atherosclerotic rabbits (Watanabe Heritable Hyper Lipidemic [WHHL], 13-mo-old male, n = 5) and controls (New Zealand White, n = 2). Rabbits were fasted for 6 h before 5.55 × 107 Bq (1.5 mCi) of 18F-FDG were injected 1 h before the imaging procedure. Rabbits were anesthetized, and the right or left common carotid artery was surgically exposed. An 8 French catheter sheath was inserted into the common carotid artery, and a 0.035-cm (0.014-in) guidewire was advanced to the iliac artery, guided by x-ray fluoroscopy. A bare metal stent was implanted in the dorsal abdominal aorta as a landmark, followed by the 7 French imaging catheters that were advanced up to the proximal stent edge. Our CIRPI and clinical optical coherence tomography (OCT) were performed using pullback and nonocclusive flushing techniques. After imaging with the CIRPI system, the descending aorta was flushed with contrast agent, and OCT images were obtained with a pullback speed of 20 mm/s, providing images at 100 frames/s. Results were verified with histochemical analysis. Results: Our CIRPI system successfully detected the locations and characterized both stable and vulnerable aortic plaques in vivo among all WHHL rabbits. Calcification was detected from the stable plaque (540 and 560 nm), whereas TCFA exhibited phospholipids/cholesterol (1040 nm, 1210 nm). These findings were further verified with the clinical OCT system showing an area of low attenuation filled with lipids within TCFA. PAT images illustrated broken elastic fiber/collagen that could be verified with the histochemical analysis. All WHHL rabbits exhibited sparse to severe macrophages. Only 4 rabbits showed both moderate-to-severe level of calcifications and cholesterol clefts. However, all rabbits exhibited broken elastic fibers and collagen deposition. Control rabbits showed normal wall thickness with no presence of plaque tissue compositions. These findings were verified with OCT and histochemical analysis. Conclusion: Our novel multimodality hybrid system has been successfully translated to in vivo evaluation of atherosclerotic plaque structure and biology in a preclinical rabbit model. This system proposed a paradigm shift that unites molecular and pathologic imaging technologies. Therefore, the system may enhance the clinical evaluation of TCFA, as well as expand our understanding of coronary artery disease.

Local adventitial anti-angiogenic gene therapy reduces growth of vasa-vasorum and in-stent restenosis in WHHL rabbits

BackgroundAntiproliferative drugs in drug eluting stents (DES) are associated with complications due to impaired re-endothelialization. Additionally, adventitial neovascularization has been suggested to contribute to in-stent restenosis (ISR). Since Vascular Endothelial Growth Factors (VEGFs) are the key mediators of angiogenesis, we investigated feasibility and efficacy of local gene therapy for ISR utilizing soluble decoy VEGF receptors to reduce biological activity of adventitial VEGFs. MethodSixty-nine adult WHHL rabbit aortas were subjected to endothelial denudation. Six weeks later catheter-mediated local intramural infusion of 1.5x10e10 pfu adenoviruses encoding soluble VEGF Receptor-1 (sVEGFR1), sVEGFR2, sVEGFR3 or control LacZ and bare metal stent implantation were performed in the same aortic segment. Marker protein expression was assessed at 6d in LacZ cohort. Immunohistochemistry, morphometrical analyses and angiography were performed at d14, d42 and d90. ResultsTransgene expression was localized to adventitia. All decoy receptors reduced the size of vasa-vasorum at 14d, AdsVEGFR2 animals also had reduced density of adventitial vasa-vasorum, whereas AdsVEGFR3 increased the density of vasa-vasorum. At d42, AdsVEGFR1 and AdsVEGFR2 reduced ISR (15.7 ± 6.9% stenosis, P < 0.01 and 16.5 ± 2.7%, P < 0.05, respectively) vs. controls (28.3 ± 7.6%). Moreover, AdsVEGFR-3 treatment led to a non-significant trend in the reduction of adventitial lymphatics at all time points and these animals had significantly more advanced neointimal atherosclerosis at 14d and 42d vs. control animals. ConclusionsTargeting adventitial neovascularization using sVEGFR1 and sVEGFR2 is a novel strategy to reduce ISR. The therapeutic effects dissipate at late follow up following short expression profile of adenoviral vectors. However, inhibition of VEGFR3 signaling accelerates neoatherosclerosis.

Systematic identification of rabbit LncRNAs reveals functional roles in atherosclerosis

Long noncoding RNAs (lncRNAs) have been gradually emerging as important regulators in various biological processes and diseases, while the contributions of lncRNAs to atherosclerosis remain largely unknown. Our previous work has discovered atherosclerosis associated protein-coding genes by transcriptome sequencing of rabbit models. Here we investigated the roles of lncRNAs in atherosclerosis. We defined a stringent set of 3736 multi-exonic lncRNA transcripts in rabbits. All lncRNAs are firstly reported and 609 (16.3%) of them are conserved in 13 species. Rabbit lncRNAs have similar characteristics to lncRNAs in other mammals, such as relatively short length, low expression, and highly tissue-specificity. The integrative analysis of lncRNAs and co-expressed genes characterize diverse functions of lncRNAs. Comparing two kinds of atherosclerosis models (LDLR-deficient WHHL rabbits and cholesterol-fed NZW rabbits) with their corresponding controls, we found the expression changes of two rabbit models were similar in aorta in but different in liver. The shared change in aorta revealed a subset of lncRNAs involved in immune response, while the cholesterol-fed NZW rabbits showed broader lncRNA expression changes in skeletal muscle system compared to WHHL rabbits. These atherosclerosis-associated lncRNAs and genes provide hits for the experimental validation of lncRNA functions. In summary, our study systematically identified rabbit lncRNAs for the first time and provides new insights for understanding the functions of lncRNAs in atherosclerosis. This article is part of a Special Issue entitled: Accelerating Precision Medicine through Genetic and Genomic Big Data Analysis edited by Yudong Cai & Tao Huang.

Structural Remodeling of Sympathetic Innervation in Atherosclerotic Blood Vessels: Role of Atherosclerotic Disease Progression and Chronic Social Stress.

The sympathetic nervous system (SNS) can undergo dramatic structural plasticity in response to behavioral factors and/or the presence of disease, leading to SNS hyperinnervation of peripheral tissues. The SNS has been proposed as an important mediator between stressful behavior and the progression of atherosclerosis in the vasculature. The present study examined whether structural remodeling of the SNS occurs in the vasculature in a genetically hyperlipidemic animal model of atherosclerosis, the Watanabe heritable hyperlipidemic rabbit (WHHL; relative to normolipidemic New Zealand white rabbits [NZW]), and whether SNS plasticity is driven by the progression of disease and/or by stressful social behavior. WHHL and NZW rabbits were assigned to an unstable or stable social environment for 4 months. Aortic atherosclerosis was assessed and SNS aortic innervation quantified using immunofluorescent microscopy. Numerous SNS varicosities were observed throughout the aorta in WHHLs and NZWs, extending into the vascular media and intima, an innervation pattern not previously reported. WHHLs exhibited significantly greater innervation than NZWs (F(1,41) = 55.3, p < .001), with extensive innervation of the atherosclerotic neointima. The innervation density was highly correlated with the extent of disease in the WHHLs (r(21) = 0.855, p < .001). Social environment did not influence innervation in NZWs (aortic arch: p = .078, thoracic aorta: p = .34) or WHHLs (arch: p = .97, thoracic: p = .61). The findings suggest that hyperinnervation is driven largely by the progression of disease rather than social environment. SNS innervation patterns observed in atherosclerotic human and mouse aortas were consistent with the rabbit, suggesting that SNS hyperinnervation of the diseased vessel wall is a general feature across mammalian species.

A non-hypocholesterolemic atorvastatin treatment improves vessel elasticity by acting on elastin composition in WHHL rabbits

Background and aimsStatins are prescribed for their preventative effects within atherosclerosis development. To our knowledge, no study focusing on very low-dose (non-hypolipidemic effect) and long-term atorvastatin treatment in vivo was available. Our aim was to assess the effect of such atorvastatin treatment on the mechanical and functional characteristics of arteries in the context of primary prevention. MethodsAn atorvastatin treatment (2.5 mg/kg/day) was tested against controls on 34 male 3 to 12 month-old WHHL rabbits. No effect on total cholesterol, triglycerides, HDL or LDL was observed. The arterial stiffness was evaluated on vigil animals by pulse wave velocity (PWV) measurement. Then, in vitro measurements were made to evaluate (1) the endothelial and vascular smooth muscle function, (2) the elasticity of the arterial wall and (3) the composition in collagen and elastin in the aorta. ResultsThe PWV increasing observed with age in control group was canceled by treatment, creating a significance difference between groups at 12 months (5.17 ± 0.50 vs 2.14 ± 0.34 m s−1 in control and treated groups respectively). Vasoreactivity modifications can’t explain this result but maintain of elasticity with treatment in large arteries was confirm by a static tensile test. A first possible explanation is the change of wall composition with treatment, validated by the percentage of elastin at 12 months, 4.4% lower in the control group compared to the treated group (p < 0.05). ConclusionsThis study shows that a non-hypocholesterolemic statin treatment could improve vessel elasticity in the atherosclerotic WHHL model. The great novelty of this work is the vessel wall composition changing associated. This first approach in animal opens the reflection on the use of these low doses in humans. This could be interesting in the context of arterial stiffening with aging, non-hyperlipidemic atherosclerosis or with cholesterol reduce by another therapy or lifestyle modification.

Abstract 591: Development of Near-infrared Fluorescent Probe for Targeted Uptake by Atherosclerotic Plaque Macrophages

Macrophages are a pivotal element in the development of atherosclerotic plaques and their polarization strongly affects plaque stability. Development of molecular imaging techniques to identify vulnerable plaques in atherosclerotic vessel walls will be a valuable diagnostic tool to assess patients` risk of myocardial infarction or stroke and to adjust therapy. Imaging of unstable plaques has so far been performed by using PET imaging agent [ 18 F] FDG. Fluorescence imaging using near-infrared fluorescent agents offers several advantages, as they are simple to use and minimally invasive. We have developed an activable near-infrared fluorescent probe using either peptide-linked ICG dye (indocyanine green) or free ICG as cargo in liposomes. The liposomes were labeled with phosphatidyl serine in order to trigger phagocytic uptake by macrophages. We have investigated the properties of our liposome probes in order to assess their suitability for screening of atherosclerosis risk patients in a wide array of different experimental models including cell culture and various animals (apoE -/- mice, WHHL rabbits and macaca fascicularis monkeys). Cell culture experiments using the human monocytic cell line THP-1 after differentiation into macrophages using the phorbol ester PMA and polarization of the macrophages by either LPS/IFNγ for M1 polarization or IL-4/ IL-13 for M2 polarization have shown considerable differences in uptake efficiency for the liposomes. M2 macrophages were found to show highest phagocytic activity while not polarized M0 were intermediate and M1 macrophages were least active. Polarization was confirmed by measuring known marker genes (TNFA, CCL3, MRC1) of macrophage polarization by RT-qPCR. In the animal studies we observed enrichment of ICG-labeled liposomes in atherosclerotic plaques of apoE -/- mice as well as WHHL rabbits. Macaca fascicularis experiments attempted to simulate final application in human subjects by detecting atherosclerotic plaques within the carotid aorta. Preliminary results indicate promising potential for liposome probes.

0300 : Mechanical and functional vascular impact of a low dose atorvastatin treatment in WHHL rabbits

This study is a new contribution to the analysis of the effects of a low dose of statin used at concentrations below its lipid-lowering effect. an atorvastatin treatment (2.5 mg/kg/day) was tested against controls on 34 male 3 to 12 month-old rabbits. The Arterial stiffness was evaluated on vigil animals by pulse wave velocity (PWV) measurement. In addition, i n vitro measurements were performed to evaluate (1) the endothelial and vascular smooth muscle function, (2) the elasticity of the arterial wall (with a static tensile test) and (3) the composition in collagen and elastin in the aorta (with two-photon and second harmonic generation microscopy). The level of triglycerides, Height Density Lipoprotein and Low Density Lipoprotein remain similar over the time between the control and statin groups. However, an increase in PWV was observed during the time in the group without statin, while it was not in the group with statin (5.17 ±0.50 vs. 2.14 ±0.34 m.s-1; p<0.05; at 12 month, respectively, Figure). In addition, at 12 month, the percentage of elastin was lower in the control group (32.4±1.5) compared to the treated group (33.9±1,4). The observed change in PWV was due to the modification in structural component of the vessel. Chronic low dose of atorvastatin prevents the loss of elasticity in the aorta in the WHHL rabbits. This study shows a beneficial effect of our treatment on the vascular system of the atherosclerotic WHHL rabbit. The author hereby declares no conflict of interest Figure Evolution of pulse wave velocity over the time

18F]FDG Uptake in the Aortic Wall Smooth Muscle of Atherosclerotic Plaques in the Simian Atherosclerosis Model.

Atherosclerosis is a self-sustaining inflammatory fibroproliferative disease that progresses in discrete stages and involves a number of cell types and effector molecules. Recently, [18F]fluoro-2-deoxy-D-glucose- ([18F]FDG-) positron emission tomography (PET) has been suggested as a tool to evaluate atherosclerotic plaques by detecting accumulated macrophages associated with inflammation progress. However, at the cellular level, it remains unknown whether only macrophages exhibit high uptake of [18F]FDG. To identify the cellular origin of [18F]FDG uptake in atherosclerotic plaques, we developed a simian atherosclerosis model and performed PET and ex vivo macro- and micro-autoradiography (ARG). Increased [18F]FDG uptake in the aortic wall was observed in high-cholesterol diet-treated monkeys and WHHL rabbits. Macro-ARG of [18F]FDG in aortic sections showed that [18F]FDG was accumulated in the media and intima in the simian model as similar to that in WHHL rabbits. Combined analysis of micro-ARG with immunohistochemistry in the simian atherosclerosis model revealed that most cellular [18F]FDG uptake observed in the media was derived not only from the infiltrated macrophages in atherosclerotic plaques but also from the smooth muscle cells (SMCs) of the aortic wall in atherosclerotic lesions.

Bisphenol A exposure induces metabolic disorders and enhances atherosclerosis in hyperlipidemic rabbits

Bisphenol A (BPA) is an artificial environmental endocrine disrupter. Excess exposure to BPA may induce many disorders in the metabolism and cardiovascular system. However, the underlying toxicological mechanisms remain largely unknown. In this study, we administered genetically hyperlipidemic Watanabe heritable hyperlipidemic (WHHL-MI) rabbits (male, 14 week old), which have more common features with humans than the mouse and rat especially in the metabolism and cardiovascular system, with BPA at 40 mg kg(-1) day(-1) for 8 weeks by gavage and compared their plasma lipids, glucose and insulin response with those of the vehicle group. All of the rabbits were sacrificed, and their pancreas, liver, adipose tissue, heart and aorta were analyzed using histological and morphometric methods. Furthermore, we treated human hepatoma HepG2 cells and human umbilical cord vein endothelial cells (HUVECs), with different doses of BPA based on the serum BPA levels in the WHHL rabbits for 6 h to investigate the possible molecular mechanisms. Our results showed that BPA-treated rabbits showed insulin resistance, prominent adipose accumulation and hepatic steatosis. Additionally, BPA exposure also caused myocardial injury and enhanced the development of atherosclerosis in the aortic arch with increased macrophage number (86%) and advanced lesion areas (69%). Increased expression of inflammatory genes found in the liver of BPA-treated rabbits along with the up-regulation of ER stress, lipid and glucose homeostasis and inflammatory genes in the cultured HepG2 cells and HUVECs suggest that BPA may induce metabolic disorders and enhance atherosclerosis through regulating above molecular pathways in the liver and endothelium.

Significant accumulation of oxLDL/beta2-glycoprotein i complexes in arterial lesions of whhl rabbits: PET/CT imaging using an auto antibody's scFv variant

Significant accumulation of oxLDL/beta2-glycoprotein i complexes in arterial lesions of whhl rabbits: PET/CT imaging using an auto antibody's scFv variant

Abstract 588: Optimization of Radiolabeled Liposomes for in vivo Atherosclerosis Imaging by SPECT

Objectives: Molecular imaging enables non-invasive in vivo detection of vulnerable plaques. Last year, we reported an atherosclerosis imaging agent, 111 In-labeled liposome. The liposome was modified with phosphatidylserine (PS), since macrophages recognize PS to phagocytize apoptotic cells in the plaque. PS modification was successful and we could visualize atherosclerotic plaques by SPECT. However, the too quick blood clearance seemed to have reduced PS-liposome accumulation to the plaque. Therefore, in this study, we PEGylated the liposome to retard the blood clearance. Methods: PS liposomes were prepared by lipid-film hydration method. The liposomes, sizes in 100 or 200 nm, were PEGylated with PEG2000 or PEG5000 in 1 or 5% w/w. The liposomes were radiolabeled by encapsulating 111 In-NTA using active-loading method. For in vitro uptake study, the liposomes were incubated with mouse peritoneum macrophages. The in vivo biodistribution studies were done in ddY mice. En face autoradiograms were obtained with ApoE-/- mice 2 hr after the liposome injection. For SPECT imaging, WHHL rabbits were used. Results: The in vitro uptake levels to macrophages were decreased by PEGylation. 5% PEG5000 decreased the uptake to the half of non-PEGylated one, but 1% PEG2000 affected less than 5%. In vivo results showed slower blood clearance in PEGylated liposomes (12 %dose/g for 5%PEG5000, 2.0 %dose/g for 1%PEG2000, and 1.0 %dose/g for non-PEGylated liposome at 60 min after the injection). PS modification improved target-to-nontarget ratios, and 5%PEG2000 added 200 nm liposome showed the highest uptake to the region. The aorta was successfully visualized by SPECT at 48hr after the 111 In-labeled 5%PEG2000-PS200 liposome injection. Conclusions: PEGlylation prolonged the blood clearance, but decreased the uptake to macrophages. However, the effect was larger for blood clearance and decrease in macrophage uptake was acceptable for in vivo imaging.

Effects of Antisense Oligonucleotides against C-Reactive Protein on the Development of Atherosclerosis in WHHL Rabbits

Increased plasma levels of C-reactive protein (CRP) are closely associated with cardiovascular diseases, but whether CRP is directly involved in the pathogenesis of atherosclerosis is still under debate. Many controversial and contradictory results using transgenic mice and rabbits have been published but it is also unclear whether CRP lowering can be used for the treatment of atherosclerosis. In the current study, we examined the effects of the rabbit CRP antisense oligonucleotides (ASO) on the development of atherosclerosis in WHHL rabbits. CRP ASO treatment led to a significant reduction of plasma CRP levels; however, both aortic and coronary atherosclerotic lesions were not significantly changed compared to those of control WHHL rabbits. These results suggest that inhibition of plasma CRP does not affect the development of atherosclerosis in WHHL rabbits.

Probucol Suppresses Macrophage Infiltration and MMP Expression in Atherosclerotic Plaques of WHHL Rabbits

Probucol is a lipid-lowering drug that is often prescribed for the treatment of familial hypercholesterolemia. However, it is not known whether probucol can change the lesion quality of atherosclerosis. We examined this possibility using WHHL rabbits, a model of human familial hypercholesterolemia. Three-month-old male WHHL rabbits were treated with either probucol(85 mg/kg/day) or atorvastatin(6 mg/kg/day) for 16 weeks, and their plasma lipid levels and atherosclerotic lesions were compared with those of a control group. We found that probucol treatment reduced the plasma cholesterol levels, but less remarkably than atorvastatin treatment. In spite of this, probucol treatment led to a prominent reduction of aortic en face lesions by 39%(P＜0.01), whereas atorvastatin reduced these by 16%(P＞0.05), compared with those in the control. Histological examinations revealed that the aortic lesions of probucol-treated rabbits were characterized by reduced macrophages and increased smooth muscle cells compared with those from both the control and atorvastatin groups. Furthermore, probucol treatment reduced the coronary artery stenosis and increased the plaque stability. These results suggest that probucol treatment may have beneficial effects on the plaque stability of hypercholesterolemic patients.