Atherosclerosis In Cholesterol-fed Rabbits Research Articles

Anti-atherosclerotic effects of garlic preparation in freeze injury model of atherosclerosis in cholesterol-fed rabbits

BackgroundGarlic (Allium sativum L.) is one of the most popular substances used to reduce various risks associated with cardiovascular disease. However, little is known on the direct effects of garlic on atherosclerosis. PurposeIn the present study we have examined the effect of per oral administration of the time-released garlic herbal preparation on serum atherogenicity and formation of intimal thickening after freeze injury in cholesterol-fed rabbits. MethodsGroup 1 rabbits maintained on the standard cholesterol-rich diet served as the control. Group 2 rabbits were fed the cholesterol-rich diet and treated with garlic preparation containing 300 mg garlic powder. ResultsLocal thickening of the aortic media (i.e., the neointima formation) in the freeze injury zone was observed in all the rabbits. Regular garlic preparation therapy prevented the neointima formation and the accumulation of free and esterified cholesterol, triglycerides, phospholipids and collagen in the neointima, the effects being statistically significant. Garlic preparation also decreased serum lipid content by 1.5-fold and lowered atherogenic activity of blood serum (ability to induce lipid accumulation in cultured cells) induced by cholesterol-rich diet. ConclusionThe results obtained indicate that garlic preparation prevents the development of cholesterol-induced experimental atherosclerosis and possesses the direct anti-atherogenic activity.

Antihypercholesterolemic and antioxidant efficacies of zerumbone on the formation, development, and establishment of atherosclerosis in cholesterol-fed rabbits.

Owing to the high incidence of cholesterol-induced cardiovascular disease, particularly atherosclerosis, the current study was designed to investigate the preventive and therapeutic efficacies of dietary zerumbone (ZER) supplementation on the formation and development of atherosclerosis in rabbits fed with a high cholesterol diet. A total of 72 New Zealand white rabbits were divided randomly on two experimental studies carried out 8 weeks apart. The first experiment was designed to investigate the prophylactic efficacy of ZER in preventing early developed atheromatous lesion. The second experimental trial was aimed at investigating the therapeutic effect of ZER in reducing the atherosclerotic lesion progression and establishment. Sudanophilia, histopathological, and ultrastructural changes showed pronounced reduction in the plaque size in ZER-medicated aortas. On the other hand, dietary supplementation of ZER for almost 10 weeks as a prophylactic measure indicated substantially decreasing lipid profile values, and similarly, plaque size in comparison with high-cholesterol non-supplemented rabbits. Furthermore, the results of oxidative stress and antioxidant biomarker evaluation indicated that ZER is a potent antioxidant in suppressing the generation of free radicals in terms of atherosclerosis prevention and treatment. ZER significantly reduced the value of malondialdehyde and augmented the value of superoxide dismutase. In conclusion, our data indicated that dietary supplementation of ZER at doses of 8, 16, and 20 mg/kg alone as a prophylactic measure, and as a supplementary treatment with simvastatin, significantly reduced early plague formation, development, and establishment via significant reduction in serum lipid profile, together with suppression of oxidative damage, and therefore alleviated atherosclerosis lesions.

Urotensin II promotes atherosclerosis in cholesterol-fed rabbits.

Urotensin II (UII) is a vasoactive peptide composed of 11 amino acids that has been implicated to contribute to the development of cardiovascular disease. The purpose of this study was to investigate whether UII affects the development of atherosclerosis in cholesterol-fed rabbits. UII was infused for 16 weeks through an osmotic mini-pump into male Japanese White rabbits fed on a high-cholesterol diet. Plasma lipids and body weight were measured every 4 weeks. Aortic atherosclerotic lesions along with cellular components, collagen fibers, matrix metalloproteinase-1 and -9 were examined. Moreover, vulnerability index of atherosclerotic plaques was evaluated. UII infusion significantly increased atherosclerotic lesions within the entire aorta by 21% over the control (P = 0.013). Atherosclerotic lesions were increased by 24% in the aortic arch (P = 0.005), 11% in the thoracic aorta (P = 0.054) and 18% in the abdominal aorta (P = 0.035). These increases occurred without changes in plasma levels of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides or body weight. Immunohistochemical staining revealed that macrophages and matrix metalloproteinase-9 were significantly enhanced by 2.2-fold and 1.6-fold in UII group. In vitro studies demonstrated that UII up-regulated the expression of vascular cell adhesion protein-1 and intercellular adhesion molecule-1 in human umbilical vein endothelial cells, which was inhibited by the UII receptor antagonist urantide. In conclusion, our results showed that UII promotes the development of atherosclerotic lesions and destabilizes atherosclerotic plaques in cholesterol-fed rabbits.

Probucol inhibits the initiation of atherosclerosis in cholesterol-fed rabbits.

BackgroundProbucol and statin are often prescribed for treating atherosclerosis. These two drugs exhibit different mechanisms but it is unknown whether they have the same anti-atherogenic properties. In the current study, we examined whether these two drugs at optimal doses could inhibit the initiation of atherosclerosis in cholesterol-fed rabbits in the same way.MethodsNew Zealand White rabbits were fed a cholesterol-rich diet for 5 weeks to produce the early-stage lesions of atherosclerosis. Drug-treated rabbits were administered either probucol or atorvastatin and serum lipids and aortic atherosclerotic lesions were compared with those in a control group.ResultsAtorvastatin treatment significantly reduced serum total cholesterol levels while probucol treatment led to significant reduction of high-density lipoprotein cholesterol levels without changing total cholesterol levels compared with those in the control group. Compared with the control, probucol treatment led to 65% (p < 0.01) reduction while atorvastatin treatment led to 23% (p = 0.426) reduction of the aortic lesion area. Histological and immunohistochemical analyses revealed that the lesions of the probucol-treated group were characterized by remarkable reduction of monocyte adherence to endothelial cells and macrophage accumulation in the intima compared with those of both atorvastatin and control groups. Furthermore, low-density lipoprotein (LDL) isolated from the probucol group exhibited prominent anti-oxidative reaction, which was not present in LDL isolated from either the atorvastatin-treated or the control group.ConclusionsThis study suggests that probucol inhibits the initiation of atherosclerosis by reducing monocyte adherence and infiltration into the subintima. Anti-oxidization of LDL by probucol protects more effectively against early-stage lesion formation than statin-mediated lipid-lowering effects.

Mulberry Leaf Extract Inhibits the Development of Atherosclerosis in Cholesterol-Fed Rabbits and in Cultured Aortic Vascular Smooth Muscle Cells

This study used high-cholesterol-fed New Zealand white rabbits and aortic vascular smooth muscle cells (VSMCs) to investigate the impact of mulberry leaf extract (MLE) on the development of atherosclerosis. The results show that the major components of MLE are polyphenols, flavonoids, carbohydrates, proteins, and lipids, and the major contituents of mulberry leaf polyphenol extract (MLPE) are polyphenols and flavonoids. In addition to improvement of liver function, the atheroma burden and levels of serum cholesterol, triglycerides, and low-density lipoprotein (LDL) are also significantly reduced after MLE treatment. MLE and MLPE improved endothelial function, inhibited proliferation and migration of aortic VSMCs, and reduced atheromas in the vascular wall. In conclusion, this study demonstrates that, in addition to exerting hypolipidemic effects, MLE and MLPE can effectively inhibit proliferation and migration of aortic VSMCs, improve vascular endothelial function, and reduce atheroma burden, thereby preventing atherosclerosis.

Protective effects of propolis and thymoquinone on development of atherosclerosis in cholesterol-fed rabbits

Hypercholesterolemia, cholesterol-enriched diet and oxidative stress have been shown to increase serum total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C) levels resulting in development of atherosclerosis. Antioxidants play an important role in inhibiting and scavenging free radicals, thus providing protection to humans against infectious and degenerative diseases. The present study was undertaken to examine the possible protective effects of propolis (a resinous hive product collected by honeybees from various plant sources) and thymoquinone (TQ, active constituent of Nigella. Sativa seeds oil) on serum lipid levels and early atherosclerotic lesions in hypercholestrolemic rabbits. New Zealand rabbits were fed on either standard chow or atherogenic diet during four weeks and concomitantly received either propolis or TQ. At the end of experiment period, serum samples were collected to determine lipid profile, kidney functions and antioxidant status. Tissues from aorta, pulmonary artery and kidney were taken for histopathological examination. The cholesterol-enriched diet induced a significant increase in serum TC, triglycerides, LDL-C, thiobarbituric acid-reactive substances concentrations and a significant decrease in high density lipoprotein-cholesterol and in reduced glutathione levels compared to control group. Administration of propolis or TQ with cholesterol-enriched diet significantly (p < 0.05) reduced TC, LDL-C, triglycerides and thiobarbituric acid-reactive substances concentrations, while increased high density lipoprotein-cholesterol concentration, as well as glutathione content compared to high cholesterol (HC) control group. Kidney function parameters were significantly affected by cholesterol diet and both propolis and TQ counterregulated the cholesterol-induced changes. Histopathologically, early atherosclerotic changes were observed in HC control group represented by endothelial damage and thickened foam cells while propolis or TQ provided protection against the HC-induced damage. In conclusion, the present study suggests the potential beneficial effects of both propolis and TQ in diminishing the risk of atherosclerosis via antioxidant mechanism.

The diameter of liver sinusoidal fenestrae is not a major determinant of lipoprotein levels and atherosclerosis in cholesterol-fed rabbits

The liver is a key organ in lipid and lipoprotein metabolism. It has been postulated that a small diameter of sinusoidal fenestrae retards clearance of chylomicron remnants, resulting in hypercholesterolemia and atherosclerosis. However, this hypothesis has not been rigorously tested hitherto. In the current study, we compared plasma levels of proatherogenic lipoproteins and assessed the development of atherosclerosis at distinct locations throughout the arterial tree in heterozygous New Zealand White and Dutch Belt rabbits that are deficient in low-density lipoprotein receptor and with an average fenestrae size of 103 and 124 nm, respectively. Feeding of a 0.15% cholesterol diet for 4 months resulted in similar total plasma cholesterol levels in New Zealand White (420±20 mg/dl) and Dutch Belt (380±30 mg/dl) rabbits. Following isolation of lipoproteins by ultracentrifugation, no biologically significant differences in very-low-density lipoprotein, intermediate-density lipoprotein, and low-density lipoprotein cholesterol levels were observed between cholesterol-fed New Zealand White and Dutch Belt rabbits. Furthermore, the relative amount of intestinally derived apolipoprotein-B48-containing lipoproteins did not differ significantly between both strains (7.3±0.42% vs. 8.0±0.54%). Atherosclerosis was more pronounced in the thoracic aorta in New Zealand White rabbits than in Dutch Belt rabbits, but the reverse was observed with the abdominal aorta. These topographic differences cannot be explained by circulating lipoprotein levels. The data presented in this study do not support the hypothesis that the diameter of fenestrae is an important determinant of chylomicron remnant levels, diet-induced hypercholesterolemia, and atherosclerosis in cholesterol-fed rabbits.

Extract from the leaf of nucifera reduced the development of atherosclerosis via inhibition of vascular smooth muscle cell proliferation and migration

Nelumbo nucifera GAERTN, a perennial aquatic plant, has been used as a medicinal herb in China and India. We have previously reported that consumption of nucifera leaf extract (NLE) reduced the development of atherosclerosis in cholesterol-fed rabbits; however, the molecular mechanisms involved were unclear. Atherosclerotic plaque is generated partly by proliferation and migration of vascular smooth muscle cells (VSMC). Herein, we demonstrated that VSMC treated with NLE-triggered apoptosis and affected the JNK and p38 Mitogen-Activated Protein Kinase (MAPK) pathways. Pre-treating VSMC with inhibitors of JNK, p38, and p53 reduced NLE-induced apoptosis. Non-cytotoxic doses of NLE also abolished secretion of MMP-2/9 and inhibited cell migration via restraining the FAK/PI 3-kinase/small G protein pathway. Histopathological examination showed that 1.0% of NLE reduced neointima formation conspicuously and inhibited smooth muscle cell proliferation and MMP-2 secretion in the blood vessel of rabbits fed with a high cholesterol diet (HCD). We also verified that the extract’s total phenolic acids and the total flavonoids were approximately about 70%. In conclusion, our results shed light on the molecular mechanisms whereby the polyphenol-rich water extract of nucifera leaves could inhibit both proliferation and migration of VSMC, and it might serve as a potential anti-atherogenic agent.

Effects of probiotic bacteria, isoflavones and simvastatin on lipid profile and atherosclerosis in cholesterol-fed rabbits: a randomized double-blind study

BackgroundMuch attention has been drawn to different alternative strategies for cardiovascular disease prevention. Objective: The aim of the present study was to observe and compare the effects of Enterococcus faecium CRL183 (probiotic microorganism), an isoflavones mixture and simvastatin (drug used to treat hypercholesterolemia) on lipid parameters and atherosclerosis development in rabbits with induced hypercholesterolemia.MethodsThe animals were randomly allocated to 5 experimental groups (n = 6) for 60 days: control (C) that did not consume cholesterol, hypercholesterolemic (H) that consumed an atherogenic diet (1.0% cholesterol wt/wt), hypercholesterolemic plus E. faecium (HE), hypercholesterolemic plus isoflavone (HI) and hypercholesterolemic plus simvastatin (HS). Total and HDL-cholesterol and triglycerides were determined by enzymatic methods; non-HDL-C was calculated by subtracting HDL-C from total cholesterol; and atherosclerosis was presented as the percentage of lesion area, relative to the total area from the aorta segment analyzed.ResultsSimvastatin significantly reduced the tot cholesterol (16%) and non-HDL-C level (17%) and increased the HDL-C (98%), compared to group H. E. faecium raised the HDL-C level by 43.3% (P < 0.05). Isoflavone decreased the total cholesterol and non-HDL-C concentrations (9%), but this effect was not statistically significant. At the end of the treatments, groups HE and HS had significantly lower levels of triglycerides in relation to H and HI. The atherosclerotic lesion area in the aortic arch was not different between groups. The extent of atherosclerosis in the thoracic and abdominal aorta was reduced in the groups HI and HS by 22.7% and 26.7% respectively, but this effect was not significant (P > 0.05).ConclusionThe results indicated that probiotic microorganism E. faecium CRL 183 could be used to improve the lipid profile as an alternative or an adjuvant for drug therapy. The effectiveness of simvastatin in the management of blood lipid was confirmed. There were no effects of soy isoflavones, E. faecium and simvastatin on atherosclerosis development.

Nanoparticle pharmacokinetic profiling in vivo using magnetic resonance imaging

Contrast agents targeted to molecular markers of disease are currently being developed with the goal of identifying disease early and evaluating treatment effectiveness using noninvasive imaging modalities such as MRI. Pharmacokinetic profiling of the binding of targeted contrast agents, while theoretically possible with MRI, has thus far only been demonstrated with more sensitive imaging techniques. Paramagnetic liquid perfluorocarbon nanoparticles were formulated to target alpha(v)beta(3)-integrins associated with early atherosclerosis in cholesterol-fed rabbits to produce a measurable signal increase on magnetic resonance images after binding. In this work, we combine quantitative information of the in vivo binding of this agent over time obtained by means of MRI with blood sampling to derive pharmacokinetic parameters using simultaneous and individual fitting of the data to a three compartment model. A doubling of tissue exposure (or area under the curve) is obtained with targeted as compared to control nanoparticles, and key parameter differences are discovered that may aid in development of models for targeted drug delivery.

Therapeutic dose of nebivolol, a nitric oxide-releasing β-blocker, reduces atherosclerosis in cholesterol-fed rabbits

Nitric oxide (NO) exerts a plethora of vascular beneficial effects. The NO-releasing β-blocker nebivolol is a racemic mixture of d/l-enantiomers that displays negative inotropic as well as direct vasodilating activity. The in vivo antiatherogenic activity of therapeutic doses of the β-blocker with antioxidant properties carvedilol (12.5 mg/day) or nebivolol (5 mg/day) was tested in cholesterol-fed rabbits. Animals received a 1% cholesterol-rich diet alone (controls) or mixed with drugs (treated animals) for 8 weeks. While it did not affect hyperlipidemia, nebivolol inhibited the development of atherosclerosis, expressed as computer-assisted imaging analysis of aortic area covered by lesions (23.3 ± 4.1% in treated vs 38.2 ± 6.4% in control animals, p < 0.01). Differently, in our experimental condition of therapeutic drug doses, this antiatherogenic effect did not reach statistical significance in rabbits treated with carvedilol (32.5 ± 5.1% aortic area covered by lesions, p = NS vs controls). Plasma nitrates increased in rabbits treated with nebivolol while both β-blockers reduced LDL oxidation. Moreover, nebivolol induced a consistent increase of endothelial reactivity and aortic eNOS expression compared with control animals ( p < 0.05) and those receiving carvedilol ( p < 0.05). Since NO may exert beneficial effects in atherosclerosis, a NO-dependent mechanism could explain this data. These observations suggest that the NO-releasing β-blocker, nebivolol, might represent an effective pharmacological approach for preventing atherosclerotic lesion progression.

A Novel Role for the Glucocorticoid Receptor in the Regulation of Monocyte Chemoattractant Protein-1 mRNA Stability

Monocyte chemoattractant protein-1 (MCP-1) plays an important role in attracting monocytes to sites of inflammation and is the dominant mediator of macrophage accumulation in atherosclerotic plaques. We have previously shown that glucocorticoids inhibit the secretion of MCP-1 in arterial smooth muscle cells (SMC) by markedly decreasing MCP-1 mRNA stability. We now report that the destabilization of MCP-1 mRNA is mediated by the glucocorticoid receptor (GR). The GR antagonist, RU486, blocked the effect of the glucocorticoid dexamethasone (Dex) on MCP-1 mRNA stability in SMC culture. Using a previously reported in vitro mRNA gel shift and stability assay, antibodies to the GR blocked the ability of cytoplasmic extracts from Dex-treated SMC to decay MCP-1 mRNA. Recombinant human GR (rhGR) bound in a concentration-dependent manner to in vitro transcribed MCP-1 mRNA, whereas other members of the steroid hormone receptor family did not. Binding of GR to MCP-1 mRNA was specific as it was not found to bind other mRNAs. Immunoprecipitation of GR in extracts from Dex-treated SMC followed by real-time reverse transcription-PCR demonstrated that endogenous GR was bound specifically to MCP-1 mRNA. The addition of exogenous rhGR blocked the ability of extracts from Dex-treated SMC to degrade MCP-1 mRNA, suggesting that exogenous rhGR can compete with an endogenous GR-containing degradative complex. These data suggest a novel role for the GR in binding to and facilitating mRNA degradation. These results provide novel insights into GR function and may provide a new approach to attenuate the inflammatory response mediated by MCP-1.

Roads to Dysfunction

See related article, pages 951–960 Oxidized low-density lipoprotein (oxLDL) is considered to be the strongest proatherogenic lipoprotein. OxLDL is rapidly taken up by endothelial cells and macrophages and via the steps of foam cell formation and cell death, oxLDL eventually accumulates in the lipid core of atherosclerotic plaques.1 The interaction of oxLDL with cells is mediated by several receptors.2 Members of the scavenger receptor family predominate in macrophages,3 whereas endothelial cells mainly take up oxLDL by the lectin-like ox-LDL receptor-1 (LOX-1).4 On binding to LOX-1, oxLDL activates a multitude of signaling cascades involving MAP kinases,5,6 protein kinase C (PKC),7,8 and protein kinase B9 in endothelial cells. The consequence of this cellular activation, is apoptosis and superoxide anion production, the latter originating from the NADPH oxidase and uncoupling of the endothelial NO synthase (eNOS). OxLDL therefore is a strong inducer of endothelial dysfunction, a state in which the endothelium, instead of generating NO, produces superoxide anions. OxLDL also modulates the specific activity of NOS. It increases caveolin I expression and the interaction of NOS with this protein impairs NO production.10 Furthermore, oxLDL modulates PKC activity and expression and this family of kinases has been shown to acutely attenuate eNOS-dependent NO production and to promote eNOS uncoupling during prolonged exposure times.11 Several observations suggest that the supply of eNOS with the substrate l-arginine is impaired in the presence of oxLDL: In hypercholesterolemia, supplementation of l-arginine improves endothelium-dependent relaxation and NO production;12,13 l-arginine also attenuates the development of atherosclerosis,14 and normalizes leukocyte adhesion …

Effect of green tea on angiogenesis and severity of atherosclerosis in cholesterol-fed rabbit

Background and Aims Since the development of the atherosclerotic plaque requires the growth of new microvessels in the plaque itself (vasa vasorum), we postulated that green tea may exert an anti-atherogenic effect. Methods and results Thirteen male New Zealand white rabbits were studied for 17 weeks. All rabbits were fed an hypecholesterolemic diet. After 2 weeks of adaptation rabbits were randomly assigned into two groups. Animals in Group A were fed the hypercholesterolemic diet and received plain tap water ad libitum. Animals in Group B were fed with the same diet and furthermore received 2.5% (g/g) green tea for 17 weeks. Conclusion According to our results the atherosclerotic lesions were more severe in Group B than in Group A specimens. Also, the number of VEGF positively stained foam cells and smooth muscle cells of Group B were significantly greater than in Group A. About 30% less plaque was found in Group A than in the control group (Group B). So, our study showed that the consumption of green tea leads to a reduction of atherosclerosis as well as a significant decrease of VEGF expression in the atherosclerotic plaque of rabbit aorta. The hypothesis that probably green tea may produce its anti-atherogenetic effect through an anti-angiogenetic mechanism needs more investigation.

Aqueous extract ofIlex paraguariensisattenuates the progression of atherosclerosis in cholesterol-fed rabbits

Ilex paraguariensis aqueous extract (mate) is an antioxidant-rich beverage widely consumed in South American countries. Here we questioned whether mate could reduce the progression of atherosclerosis in 1% cholesterol-fed rabbits. New Zealand White male rabbits (n = 32) were divided into four groups: control (C, n = 5), control-mate (CM, n = 5), hypercholesterolemic (HC, n = 11) and hypercholesterolemic-mate (HCM, n = 11). The daily water and mate extract consumption was approximately 400 ml. After 2 months of treatment, mate intake did not change the lipid profile or hepatic cholesterol content of control or hypercholesterolemic rabbits (p < 0.05). However, the atherosclerotic lesion area was considerably smaller in the hypercholesterolemic-mate group (HCM, 35.4% vs. HC, 60.1%; p < 0.05). In addition, the aortic cholesterol content was around half that of the HC group (HCM, 36.8 vs. HC, 73.9 microg/mg of protein, p < 0.05). In spite of this, the thiobarbituric acid-reactive substances (TBARS) in the atherosclerotic aorta, liver and serum, and the activity of the antioxidant enzymes in liver and aorta did not differ among groups (p > 0.05). The results showed that Ilex paraguariensis extract can inhibit the progression of atherosclerosis in cholesterol-fed rabbits, although it did not decrease the serum cholesterol or aortic TBARS and antioxidant enzymes.

Impact of Short-Term Administration of High-Density Lipoproteins and Atorvastatin on Atherosclerosis in Rabbits

This study investigates effects of short-term administration of high-density lipoproteins (HDL) and a statin on atherosclerosis in cholesterol-fed rabbits. Effects of HDL apolipoprotein and phospholipid composition have also been investigated. Aortic atherosclerosis was established over 17 weeks in 46 rabbits by balloon denudation and cholesterol feeding. During the past 5 days of the cholesterol-feeding period, animals received: (1) no treatment; (2) oral atorvastatin 5 mg/kg on each of the 5 days; or (3) infusions of HDL (8 mg/kg apolipoprotein A-I) on days 1 and 3 of the treatment phase. After euthanization, lesion size and composition were assessed by histological and immunohistochemical analysis. HDL (but not atorvastatin) reduced lesion size by 36% (P<0.05). The ratio of smooth muscle cells to macrophages in the lesions increased 2.6-fold in animals infused with HDL (P<0.05) and 4-fold in those receiving atorvastatin (P<0.01). HDL and atorvastatin reduced matrix metalloproteinase (MMP)-9 expression by 42% (P<0.05) and 45% (P<0.03), respectively. HDL increased thrombomodulin expression 2-fold (P<0.03). The beneficial effects on lesion area and plaque cellular composition were influenced by HDL phospholipid and apolipoprotein composition. Infusing small amounts of HDL rapidly reduces lesion size and is comparable to atorvastatin in promoting a stable plaque phenotype.

Molecular Imaging of αvβ3-Integrin: An Opportune Biochemical Signature For Oncologic and Cardiovascular Diseases

v 3-Integrin is a well-recognized biomarker of angiogenesis expressed on activated endothelial cells. It is a critical element in vascular restenosis where its upregulation by balloon overstretch injury promotes cell adhesion to the damaged extracellular matrix, induces extracellular metalloproteinase expression, and facilitates smooth muscle cell migration. We have conducted a series of in vivo studies in which v 3-integrin was detected by MRI (1.5T) as an early biomarker of nascent tumor growth (Vx-2 in rabbit and melanoma mice), early atherosclerosis in cholesterol-fed rabbits, and balloon overstretch-injury patterns in pigs. Paramagnetic nanoparticles covalentlycomplexed to a peptidomimetic v 3-integrin ligand were produced by microfluidization. Nontargeted paramagnetic nanoparticles and v 3-targeted nonparamagnetic nanoparticles were produced identically for control and competition studies. New Zealand White (NZW) rabbits implanted with nascent Vx-2 tumors and mice implanted with C-32 melanoma were treated systemically with v 3-integrin targeted paramagnetic nanoparticles that specifically bound and significantly enhanced (p 0.05) the MRI signal in the developing neovasculature after 2 hours (125% and 177%, respectively). Competitive blockage of v 3-integrin sites with v 3 targeted nonparamagnetic nanoparticles greatly ( 50%) diminished contrast signal enhancement (p 0.05) in both model systems. In cholesterol-fed NZW rabbits, black-blood MRI of the abdominal aorta v 3-targeted nanoparticles localized to angiogenic vessels in the expanding vaso-vasorum and produced enhanced signal (p 0.05) compared with nontargeted nanoparticles or control diet animals. In competition studies MRI enhancement was blunted, which confirmed the specificity of v 3-targeted nanoparticles. Furthermore, delayed enhancement (20 min) after injection of Gd-DTPA could not identify these early atherosclerotic changes. Finally, carotid arteries of pigs subjected to balloonoverstretch injury were treated locally with v 3 targeted, paramagnetic nanoparticles, saline or the nontargeted control. Contrast enhancement with v 3-targeted paramagnetic nanoparticles was dramatic and revealed asymmetrical patterns of balloon injury that were 50% greater than the actual balloon length and allowed the volume of vascular injury to be computed (955 234 mm2). No enhancement was discernible for the injured control vessels. v 3-Targeted paramagnetic nanoparticles provide a versatile molecular imaging platform useful for delineating vascular injury, diagnosing early atherosclerosis, and detecting nascent cancers with clinically relevant MRI systems (1.5 T). Early detection, effective therapy and sensitive longitudinal follow-up of these major disease processes with new molecular techniques could serve to noninvasively characterize and ameliorate their morbidity and mortality.

Glimepiride exhibits prophylactic effect on atherosclerosis in cholesterol-fed rabbits

Aims/hypothesis: The purpose of this study was to examine the potential prophylactic effect of glimepiride on experimental atherosclerosis in rabbits and to elucidate the mechanism of action. Methods: Rabbits were fed an atherogenic diet containing 1% cholesterol and glimepiride 0.1 mg/kg/day for 10 weeks. Plasma lipid levels were determined every 2 weeks. The percentage of atherogenic lesions of thoracic aorta stained with oil red O was calculated and histological examination of the lesions was performed. Lipid and lipid peroxide contents in thoracic aorta and liver were also determined. In addition, the inhibitory effect of glimepiride on human coronary arterial endothelial cell-mediated LDL oxidation was evaluated. Results: Accumulation of lipid-laden foam cells in the focal areas of arterial intima was observed in oil red O-positive atherosclerotic lesions. Glimepiride treatment produced significant reduction of atherosclerotic lesions (control, 57.5 ± 7.1% versus glimepiride, 20.6 ± 4.8%; P < 0.01) with no significant change observed in levels of plasma lipids. There were marked decreases in lipid and lipid peroxide contents in the thoracic aorta in glimepiride-treated rabbits with no significant change in levels of liver lipids. In cultured human coronary arterial endothelial cells, glimepiride inhibited oxidative modification of LDL in a dose-dependent manner (IC 50 = 8.8 × 10 −7 M) without cytotoxicity. Conclusions/interpretation: These findings suggest that glimepiride prevents the development of aortic atherosclerosis in fat-fed rabbits. The underlying mechanism may be inhibition of endothelial cell-mediated LDL oxidation.

Reduction of Atherosclerosis in Cholesterol-Fed Rabbits and Decrease of Expressions of Intracellular Adhesion Molecule-1 and Vascular Endothelial Growth Factor in Foam Cells by a Water-Soluble Fraction of Polygonum multiflorum

Polygonum multiflorum stilbeneglycoside (PMS) is a water-soluble fraction of Polygonum multiflorum Thunb., one of the most famous tonic traditional Chinese medicines, that has protective effects on the cardiovascular system. The purpose of the present study is to elucidate the effects of PMS on macrophage-derived foam cell functions and the reduction of severity of atherosclerosis in hypercholesterolemic New Zealand White (NZW) rabbits. NZW rabbits were fed for 12 weeks with a normal diet, a high cholesterol diet, or a high cholesterol diet associated with irrigation with different doses of PMS (25, 50, or 100 mg/kg). Treatment of NZW rabbits fed with high cholesterol diet with 100 mg/kg PMS attenuated the increase in plasma cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, and plasma triglyceride. Treatment with 50 and 100 mg/kg PMS caused 43% and 60% decrease in atherosclerotic lesioned area ratio to total surface area, respectively. In U937 foam cells, PMS could decrease the high expression of intercellular adhesion molecule (ICAM)-1 protein and the vascular endothelial growth factor (VEGF) protein levels in the medium induced by oxidized lipoprotein when analyzed by flow cytometry. The results proved that PMS is a powerful agent against atherosclerosis and that PMS action could possibly be through the inhibition of the expression of ICAM-1 and VEGF in foam cells.

Oren-gedoku-to and Keishi-bukuryo-gan-ryo Inhibit the Progression of Atherosclerosis in Diet-Induced Hypercholesterolemic Rabbits

In this study, we examined whether the Kampo formulas Oren-gedoku-to (OGT, Huanglian-jie-du-tang in Chinese) and Keishi-bukuryo-gan-ryo (KBG, Gui-zhi-fu-ling-wan in Chinese) could prevent the progression of atherosclerosis in cholesterol-fed rabbit, an animal model for hypercholesterolemia in vivo. Twenty-four male Japanese white rabbits (2 kg body weight) were divided into four groups. The control group was fed standard rabbit chow containing 1% cholesterol, the OGT group was fed standard rabbit chow containing 1% cholesterol and 1% OGT, the KBG group was fed standard rabbit chow containing 1% cholesterol and 1% KBG, and the vitamin E group was fed standard rabbit chow containing 1% cholesterol and vitamin E (450 mg/1000 g). All four groups were kept on these diets for 8 weeks. At the end of the experiments, the percentage of surface area of the total thoracic aorta with visible plaque was significantly reduced in the OGT and KBG groups. The serum thiobarbituric acid reactive substances of the vitamin E group showed a significantly low value compared with the control group, whereas the serum lipid peroxide levels of the OGT and KBG groups were considerably lower than that of the control groups as well as that of the vitamin E group. Furthermore, the urinary 8-hydroxydeoxyguanosine levels of the OGT and KBG groups were considerably lower than that of the vitamin E group. These results suggest that OGT and KBG prevent the progression of atheromatous plaque by creating a sounder antioxidant defense system than vitamin E.