Rabbit Model Of Atherosclerosis Research Articles

Anti-atherogenic effect of 15-lipoxygenase overexpression in rabbit atherosclerosis models

s / Prostaglandins & other Lipid Mediators 59 (1999) 1-235 145 ANTI-ATHEROGENIC EFFECT OF 15LIPOXYGENASE OVEREXPRESSION IN RABBIT ATHEROSCLEROSIS MODELS Frank Trebus and Hartmut Kuhn Institute of Biochemistry, University Clinics Charite, Humboldt University, Hessische Str. 3-4, 10115 Berlin, F.R.G. Oxidative modification of low density lipoprotein has been implicated as patho-physiological process in early atherogenesis and there is a substantial body of experimental data supporting this hypothesis. 15-lipoxygenases (1%LOX) are lipid peroxidizing enzymes, which are capable of oxidizing LDL to an atherogenic form, and thus, these enzymes were suggested to act proatherogenic in vivo. However, we have two lines of experimental evidente suggesting an-antiatherogenic activity of 15LOXs in rabbit atherosclerosis models. i) Transgenic rabbits, which overexpress the 15-LOX specifically in monocyte/macrophages, appear to be protected from development of atherosclerotic lesions when fed a cholesterol rich diet. A similar protection was observed when these transgenic animals were crossed with LDL receptor deficient Watanabe rabbits. ii) Systemic overexpression of the 15-LOX induced by a transient experimental anemia did also protect cholesterol fed rabbits from lipid deposition in the arterial wall. For these experiments a transient experimental anemia was induced in rabbits by phenylhydracine injection. A single treatrnent was followed by a long lasting (up to 10 weeks) systemic (al1 cells and tissues) overexpression of the 15-LOX. After the animals have recovered from the anemie stress (6 days after the injection) they were put on a lipid rich Western-type diet for 10 weeks and the extent of lipid deposition was quantified in the aorta. When 15-LOX overexpressing rabbits (n=lO) were compare with age and sex-matched controls (n=7) we observed a more than 50% reduction of aortic lipid deposition in the 15LOX overexpressing animal. In contrast, the plasma cholesterol levels, the lipoprotein profile, the gain of weight during cholesterol feeding and most of the serum diagnostic parameters were not different between the two groups. As mechanistic reason for the observed anti-atherogenic effect an involvement of the 15-LOX in intracellular cholesterol ester degradation was assumed. In fact, we found that LOX-oxidized cholesterol ester are much better substrates for the neutral cholesterolester hydrolase than their non-oxidized counterparts. These data indicated that specifically oxidized cholesterol esters are more rapidly hydrolyzed providing free cholesterol, which may enter reverse cholesterol transport. Thus, intracellular oxidation of depot cholesterol esters may counteract accumulation of cytosolic cholesterol esters preventing foam cel1 formation.

C26 A rabbit model of atherosclerosis which mimics human soft, lipid-rich, plaques

C26 A rabbit model of atherosclerosis which mimics human soft, lipid-rich, plaques

Expression of Type VIII Collagen After Cholesterol Diet and Injury in the Rabbit Model of Atherosclerosis

This study presents an analysis of the expression of type VIII collagen mRNA in response to cholesterol diet and balloon injury in the rabbit iliac artery. The design of the animal experiments was as follows: 28 male New Zealand White rabbits were divided into the 3 different treatment groups. Group 1 received regular chow; group 2 was fed with a 1% cholesterol diet for 6 weeks and normal chow for 5 weeks; and group 3 underwent balloon injury, then 6 weeks of a 1% cholesterol diet, which was followed by 5 weeks of normal chow. The expression pattern of type VIII collagen mRNA was compared with that of the fibrillar collagen types I and III, transforming growth factor-beta1, a factor known to exert the most potent stimulatory effect on collagen synthesis in vitro, and matrix metalloproteinase 1, a collagen-degrading enzyme. The cholesterol diet resulted in an upregulation of type VIII collagen, fibrillar collagens, transforming growth factor-beta1, and matrix metalloproteinase I in the adventitia. Although the number of type VIII collagen mRNA-expressing cells in the media increased, no significant difference in overall expression levels was detectable by northern blot analysis. The ratio of medial smooth muscle cells expressing type VIII collagen mRNA to those expressing type I and type III collagen mRNA (CVIII:CI:CIII) changed from 1:1.88:0.03 in the normal media to 1:0.78:0.29. When cholesterol feeding was preceded by balloon injury, type VIII collagen mRNA expression concomitant with the fibrillar collagens was further upregulated over and above that level reported after cholesterol diet alone. In general, low levels of transforming growth factor-beta1 mRNA correlated with high expression of matrix metalloproteinase I. Our study indicates that a cholesterol diet resulted in a balanced reorganization of the collagen composition but did not result in marked collagen accumulation. This may provide an extracellular environment that favors migration and proliferation processes during early atherogenesis. It also demonstrates that type VIII collagen is highly expressed and deposited at later stages, and this may be linked to processes such as tissue reorganization during vascular repair and plaque stabilization.

Amelioration by quinapril of myocardial infarction induced by coronary occlusion/reperfusion in a rabbit model of atherosclerosis: possible mechanisms.

The increased severity of the myocardial injury produced by coronary occlusion-reperfusion in models of atherosclerosis is associated with an increase in leukocyte accumulation in the ischemic myocardium. Expression of P-selectin, an adhesion molecule involved in the interaction between leukocytes and endothelium, is increased in atherosclerotic vessels. Long-term angiotensin-converting enzyme (ACE) inhibition has been shown to reduce atherosclerotic vascular change in experimental models. We examined changes in the size of the infarct resulting from coronary occlusion/reperfusion in normally fed and cholesterol-fed rabbits that were chronically treated with quinapril. Infarct size was significantly larger in the cholesterol-fed versus normally fed rabbits. ACE activity in the ischemic and nonischemic myocardium was significantly reduced by quinapril. Chronic quinapril administration significantly ameliorated the increased myocardial injury in cholesterol-fed rabbits. Quinapril administration markedly increased the myocardial cGMP content and reduced the myeloperoxidase activity in the border region of the ischemic myocardium in cholesterol-fed rabbits. The enhanced expression of P-selectin in myocardial tissue of cholesterol-fed rabbits was also effectively reduced by quinapril treatment. The above effects of quinapril were eliminated by blockade of bradykinin B2 receptors or inhibition of nitric oxide synthesis. Chronic quinapril treatment ameliorated the severity of myocardial injury produced by coronary occlusion/reperfusion in cholesterol-fed rabbits, possibly because of reversal of the enhanced interaction between leukocytes and endothelium in the ischemic myocardium via a bradykinin-related pathway.

ACE Inhibitor Quinapril Reduces the Arterial Expression of NF-κB-Dependent Proinflammatory Factors but not of Collagen I in a Rabbit Model of Atherosclerosis

Increasing evidence supports an association between inflammation and plaque rupture. Macrophages and vascular smooth muscle cells are a source of cytokines and growth factors, which contribute to ongoing inflammation during atherogenesis. In a rabbit model of atherosclerosis, we evaluated the effect of the ACE inhibitor quinapril on different parameters implicated in the pathogenesis of the plaque, such as the presence of chemokines (interleukin-8, monocyte chemoattractant protein-1), collagen I, and vascular smooth muscle cell proliferation (PDGF-B). Since nuclear factor kappaB (NF-kappaB) has been implicated in the control of chemokine transcription and cell proliferation, we also investigated its activation and localization in the lesion. Quinapril administration for 28 days caused a down-regulation in arterial expression of interleukin-8 and monocyte chemoattractant protein-1 (mRNA and protein). However, collagen I expression (mRNA and protein) was not modified. PDGF-B expression was reduced in both the intima and the media. Active NF-kappaB, found in both macrophages and vascular smooth muscle cells, was also reduced by quinapril. Nevertheless, no significant changes were noted in the mild neointima formation, although a certain trend toward normalization was found in the quinapril-treated group. In conclusion, our results show that quinapril treatment attenuates several parameters associated with inflammation within the atherosclerotic lesions that are controlled by NF-kappaB, although it has no effect on collagen I expression. Both effects could contribute to the stabilization of the atherosclerotic plaque.

HMG-CoA reductase inhibition by atorvastatin reduces neointimal inflammation in a rabbit model of atherosclerosis.

To study the effect of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA)-reductase inhibitor atorvastatin on the potential mechanisms involved in the recruitment of monocytic cells into the vessel wall. Inhibitors of HMG-CoA-reductase reduce cardiovascular mortality though the mechanisms yet elucidated. Most ischemic events are secondary to disruption of atherosclerotic plaques highly infiltrated by macrophages. Atherosclerosis was induced in the femoral arteries of rabbits by endothelial damage and atherogenic diet for 4 weeks. Then, animals were switched to standard chow and randomized to receive either no treatment or atorvastatin (5 mg/kg/d) and killed after 4 weeks. Atorvastatin induced a significant reduction in serum lipids and in lesion size. Arterial macrophage infiltration was abolished by the treatment, and monocyte chemoattractant protein-1 (MCP-1) was significantly diminished in the neointima and in the media. Nuclear factor kappa-B (NF-kappaB) was activated in the 60% of the lesions, both in macrophages and vascular smooth muscle cells (VSMC), of the untreated group while only in 30% of the atorvastatin group. NF-kappaB activity was also lower in the uninjured aorta and liver of treated compared with untreated rabbits. In cultured VSMC, MCP-1 expression and NF-kappaB activity induced by tumor necrosis factor alpha were downregulated by atorvastatin. In a rabbit atherosclerosis model, atorvastatin diminishes the neointimal inflammation, and this could contribute to the stabilization of the atherosclerotic plaque. This may be an additional explanation for the reduction of acute ischemic events in patients treated with statins.

N-acetyl-cysteine decreases the matrix-degrading capacity of macrophage-derived foam cells: new target for antioxidant therapy?

Atherosclerotic plaque destabilization triggers clinical cardiovascular disease and thus represents an attractive therapeutic target. Weakening of tissue through the action of matrix-degrading enzymes, called matrix metalloproteinases (MMPs), released by resident macrophages was previously implicated in unstable vascular syndromes. We used a hypercholesterolemic rabbit model of atherosclerosis to investigate the gelatinolytic activity associated with macrophage-derived foam cells (FCs). Gelatinolytic activity and expression of MMP-9 but not of MMP-2 cosegregated with macrophage FCs in aortic lesions. Macrophage-derived gelatinases were further investigated in vitro. MMP-9 was identified as the main macrophage-derived gelatinase in cells isolated from aortic lesions and from granuloma induced in the same rabbits to increase cell yield. Importantly, detection of activated MMP-9 in the FC culture medium supports the notion that these cells can independently initiate processing of secreted MMP zymogens to active enzymes. We further examined whether FC gelatinolytic activity is dependent on the presence of reactive oxygen species (ROS). We found that treatment (1 to 5 days) with 1 to 10 mmol/L N-acetyl-L-cysteine (NAC), an ROS scavenger, decreased not only gelatinolytic activity but also gelatinase expression by FCs. Similarly, NAC treatment of explanted lesions abolished in situ gelatinolytic activity and MMP-9 expression. Macrophage FCs are an abundant source of gelatinolytic activity that can be inhibited in vitro and in situ by NAC. This newly described action of antioxidant therapy might prove useful to inhibit matrix degradation and to improve vascular stability.

Virtualized angioscopy of the thoracic aorta in a rabbit model of atherosclerosis.

The purpose of this study was to apply virtual reality technology to spiral computed tomographic (CT) angiogram images in a rabbit model of atherosclerosis and to correlate the images with histopathologic evaluation of the aorta. Image data were transferred to the virtual endoscope system in a graphics workstation. "Virtualized angioscopy" includes an interactive graphic user interface, which controls the viewpoint, the direction of the observation, and rendering and navigation functions. The virtual angioscopy system demonstrated irregularities of the luminal surface of the ascending aorta and a smooth luminal surface in the descending aorta. These observations were correlated with histopathologic findings. The results of this study indicate that the potential and real benefits of virtualized angioscopy far outweigh several technical limitations.

23 Atorvastatin reduces lesion size and macrophage content in a rabbit model of atherosclerosis, and atenuates NFκB activation and MCP-1 expression in cultured VSMC

23 Atorvastatin reduces lesion size and macrophage content in a rabbit model of atherosclerosis, and atenuates NFκB activation and MCP-1 expression in cultured VSMC

MR Microscopy of the Arterial Wall in an Experimental Model of Atherosclerosis: Preliminary Results

To obtain images of the arterial lumen and wall in a rabbit model of atherosclerosis with use of high-resolution magnetic resonance (MR) imaging to follow morphologic changes during the induction of atherosclerosis and, hence, develop a non-invasive tool to investigate restenosis. In vivo microscopic MR images of rabbit aorta were acquired after balloon injury. Measurements of wall and lumen diameter from MR images area were compared with measurements obtained from histologic and angiographic examination. Injured rabbits exhibited an obvious thickening of the arterial wall, accompanied by an increased wall conspicuity, probably due to increases in T2. Quantitative MR morphometry corresponded well with morphologic measurements based on angiographic and histologic study. MR implanted coil technology affords imaging of the arterial lumen and wall, allowing temporal assessment of the morphologic changes due to intimal hyperplasia after balloon dilation and may enable the evaluation of novel techniques to eliminate restenosis.

Macrophage-mediated 15-lipoxygenase expression protects against atherosclerosis development.

Oxidative modification of LDL increases its atherogenicity, and 15-lipoxygenase (15-LO) has been implicated in the process. To address this issue, we generated transgenic rabbits that expressed 15-LO in a macrophage-specific manner and studied their susceptibility to atherosclerosis development when they were fed a high-fat, high-cholesterol (HFHC) diet (Teklad 0533 rabbit diet 7009 with 10% corn oil and 0.25% cholesterol) for 13.5 wk. Transgenic and nontransgenic rabbits developed similar degrees of hypercholesterolemia and had similar levels of triglyceride, VLDL, LDL, and HDL. Quantitative morphometric analysis of the aortic atherosclerosis indicated that the transgenic animals (n = 19) had significantly smaller lesion areas (9.8+/-6.5%, mean+/-SD) than their littermate controls (n = 14, 17.8+/-15.0%) (P < 0.05). In a subgroup (n = 9) of transgenic rabbits that received the HFHC diet plus the antioxidant N',N '-diphenyl-phenylenediamine (1%), the extent of lesion involvement (9.8+/-7.5%) did not differ from the subgroup (n = 10) that received the regular HFHC diet (9.7+/-5.9%). Since the results were unexpected, we repeated the experiments. Again, we found that the nontransgenic littermates (n = 12) had more extensive lesions (11.6+/-10.6%) than the transgenic rabbits (n = 13; 9.5+/-7.8%), although the difference was not significant. In a third set of experiments, we crossed 15-LO transgenic rabbits with Watanabe heritable hyperlipidemic (WHHL) rabbits and found that the lesion area in the 15-LO transgenic/heterozygous WHHL rabbits (n = 14) was only about one third (7.7+/-5.7%) that found in nontransgenic heterozygous WHHL littermate controls (n = 11, 20.7+/-19.4%) (P < 0.05). These data suggest that overexpression of 15-LO in monocytes/macrophages protects against lipid deposition in the vessel wall during early atherogenesis in these rabbit models of atherosclerosis.

Effect of thrombin inhibition with desulfatohirudin on early kinetics of cellular proliferation after balloon angioplasty in atherosclerotic rabbits.

Thrombin may have a pivotal role in restenosis after angioplasty. Hirudin, a potent thrombin inhibitor, reduces luminal narrowing by plaque after angioplasty in a rabbit model of atherosclerosis. Because cellular proliferation is believed to be an important mechanism for restenosis and thrombin has been shown to be a potent smooth muscle cell mitogen in vitro, we hypothesized that the mechanism of the effect of hirudin on limiting luminal narrowing by plaque occurs via inhibition of cellular proliferation. Femoral atherosclerosis was induced in 108 rabbits, and balloon angioplasty was performed. At angioplasty, group 1 rabbits (n=38) were treated with a 2-hour infusion of hirudin, and group 2 rabbits (n=41) were treated with heparin. Group 3 rabbits (n=29) were treated with hirudin (n=15) or heparin (n=14) and killed at 7 or 28 days to determine cross-sectional area narrowing by plaque and cellular proliferation with the use of bromodeoxyuridine labeling. At 29, 71, or 167 hours after angioplasty, group 1 and 2 rabbits were injected with 3H-thymidine and killed 1 hour later, and labeling indexes were determined. A significant increase in the index of 3H-thymidine-labeled nuclei was observed in the intima of "ballooned" arteries compared with "nonballooned" atherosclerotic arteries at both 30 hours (0.06+/-0.05 versus 0.01+/-0.01, P<.01) and 72 hours (0.10+/-0.06 versus 0.004+/-0.004, P<.01). By 7 days, the index of labeled cells was similar to baseline (0.04+/-0.03 versus 0.01+/-0.01, P=.12). Hirudin had no effect on the 3H-thymidine labeling indexes at any of the time points studied despite the fact that hirudin treatment in group 3 rabbits resulted in less cross-sectional area narrowing by plaque at both 7 and 28 days after angioplasty (41+/-16 versus 24+/-12 at 7 days and 60+/-21 versus 44+/-17 at 28 days, heparin versus hirudin; P<.03). Balloon angioplasty resulted in a marked increase in cellular proliferation that peaked at 72 hours. A 2-hour infusion of hirudin failed to reduce early 3H-thymidine labeling, suggesting that inhibition of cell proliferation within the first 7 days after angioplasty is not the predominant mechanism by which hirudin exerts its effect on limiting luminal narrowing by plaque 28 days after balloon angioplasty in this animal model.

Heterocyclic amides: inhibitors of acyl-CoA:cholesterol O-acyl transferase with hypocholesterolemic activity in several species and antiatherosclerotic activity in the rabbit.

A series of heterocyclic amides were synthesized and evaluated as inhibitors of acyl-CoA: cholesterol O-acyltransferase (ACAT) in vitro and for cholesterol lowering in cholesterol-fed rats. Compounds were evaluated for cell-based macrophage ACAT inhibition, bioactivity, and adrenal toxicity. Candidates were selected for evaluation in cholesterol-fed dogs and, ultimately, the injured cholesterol-fed rabbit model of atherosclerosis. The heterocyclic amides potently inhibited rabbit liver ACAT (IC50's = 0.014-0.11 microM), and the majority of compounds significantly lowered plasma cholesterol (42-68%) in an acute cholesterol-fed rat model at 3 mg/kg. The most efficacious compounds in the rat were evaluated for bioactivity in vivo and arterial ACAT inhibition in a cell-based macrophage ACAT assay. Two highly bioactive analogs, (+/-)-2-(3-dodecylisoxazol-5-yl)-2-phenyl-N-(2,4,6-trimethoxypheny l) acetamide (13a) and (+/-)-2-(5-dodecylisoxazol-3-yl)-2-phenyl-N-(2,4,6-trimethoxypheny l) acetamide (16a), were selected for further study and were found to be nontoxic in a guinea pig model of adrenal toxicity. Compounds 13a and 16a lowered total cholesterol in the cholesterol-fed rat, rabbit, and dog models of pre-established hypercholesterolemia. Compound 13a in the injured cholesterol-fed rabbit model of atherosclerosis was effective in slowing the development of cholesteryl ester-rich thoracic aortic lesions, reducing lesion coverage by 53% at a dose of 1 mg/kg.

914-71 High Efficiency Gene Transfer into Atherosclerotic Lesions in Hypercholesterolemic Rabbit Carotid Arteries

The feasibility of using in vivo gene transfer to induce the regression of atherosclerotic lesions remains to be defined. Accordingly, we have developed a rabbit model of atherosclerosis that consists of (i) a high cholesterol diet beginning 2 weeks prior to vascular injury (cholesterol levels: 1,000-2,000 mg/dl), (ii) balloon-injury (2 F Fogarty catheter) to the common carotid artery via the internal carotid artery, and (iii) gene transfer into the vessel wall 2 weeks after balloon injury by a second interventional procedure. Balloon injury resulted in consistent formation of neointimal lesions (intima/media ratio: 1.0–1.4; n = 3) throughout the injured vessel segment. Immunohistochemical staining against macrophages (RAM-11) showed a broad distribution of macrophages throughout the neointima and media. Transfection efficiency into the injured vessel wall was determined using a fJgalactosidase ( β -gal) reporter gene (SV40-promoter) and the highly efficient Sendai virus (HVJ)-mediated gene delivery method in which plasmid vectors are complexed with Iiposomes, nuclear protein and UV-inactivated viral protein coat. Histochemical analysis after transfection revealed strong β -gal activity (@ 30–50% of cells transfected) within the neointima and media, whereas controls (control vector transfected and/or balloon injured vessel) showed no staining. Double staining with the macrophage antibody showed that not only smooth muscle cells and fibroblasts, but also macrophages were genetically modified. We conclude that the rabbit atherosclerotic carotid artery is a suitable model for studying gene transfer as a therapeutic approach to vascular disease.

ACAT Inhibitors: Potential Anti-atherosclerotic Agents

Abstract: The evolution of ACAT inhibitors •from purely hypocholestero­ lemic agents to potential anti-atherosclerdtic agents has occurred only recently.A large number of structurally diverse ACAT inhibitors were initially developed as hypocholesterolemic agets whose prime mechanism of action was inhibition of dietary cholesterol absorption in the intestine, however, efficacy for such non-absorbable agents, in humans, has remained elusive. Esterification of cholesterol within the hepatocyte has been shown to be required for VLDL synthesis and secretion, and inhibition of ACAT within the artery wall may prove to be the "ultimate" anti-atherosclerotic mechanism by preventing the formation of cholesterol ester loaded macrophages (foam cells), the precursors of the fatty streak, an early lesion in the atherosclerotic process. Thus, more recently, there has been a concerted effort to design more bioavailable inhibitors capable of inhibiting the enzyme in the liver and artery wall. Displaying direct efficacy at the artery wall for an ACAT inhibitor has been complicated by the fact that in pre-clinical animal models, it has been difficult to dissociate the effects of lipid lowering from a true direct effect at the artery wall. Recently, a novel ACAT inhibitor, Cl-976, has been disclosed which displays anti-atherosclerotic activity in an injured cholesterol fed rabbit model of atherosclerosis without exhibiting a cholesterol lowering effect.The SAR around Cl-976 and related series will be discussed and placed in context with other novel structural types of ACAT inhibitors appearing in the recent literature.

A new rabbit model of atherosclerosis

A new rabbit model of atherosclerosis

Cholesterol-fed and casein-fed rabbit models of atherosclerosis. Part 2: Differing morphological severity of atherogenesis despite matched plasma cholesterol levels.

One-month-old male New Zealand White rabbits were fed either a cholesterol-free casein diet (n = 10) or low-level cholesterol-supplemented chow (n = 10) for 24 weeks, during which total plasma cholesterol levels were matched. After perfusion fixation, aortic tissue samples were taken from six predetermined locations and embedded in epoxy resin for examination by light and electron microscopy. Frozen sections were also obtained for histochemical demonstration of collagen and elastin. Lesion morphology was classified in toluidine blue-stained, semithin epoxy sections as early fatty streaks (round foam cells with little intervening extracellular matrix); advanced fatty streaks (foam cells with extracellular lipid); fibrous plaques (spindle-shaped cells within extracellular matrix); or atheromatous lesions (presence of an atheromatous core). In representative specimens, electron microscopy showed that the ultrastructure of round foam cells was consistent with macrophage derivation, whereas most spindle-shaped cells were clearly smooth muscle cells. Fibrous plaques were more common in the distal than the proximal aorta. Lesions in the casein-fed animals were essentially equally distributed among the four morphological categories, whereas lesions in the cholesterol-fed rabbits were predominantly of the atheromatous type. Thus, cholesterol-fed rabbits had, in general, more advanced lesions than casein-fed rabbits with matched total plasma cholesterol levels. Moreover, the feeding of a low-level cholesterol diet (0.125% to 0.5% by weight) to rabbits for a relatively short time (6 months) led to the development of advanced lesions similar to those seen in humans.

Low-density lipoprotein modification and arterial wall accumulation in a rabbit model of atherosclerosis

Chemically or enzymatically modified low-density lipoproteins (LDL), with and without changes in surface charge, were studied in vivo in the healing, balloon catheter-deendothelialized rabbit aorta to determine the effect of LDL modification on its accumulation in arterial lesions. In this model, in which healing (reendothelialization) proceeds radially outward from individual aortic branch arteries, it was previously shown by autoradiography that two kinetically distinct compartments accumulated 125I-labeled LDL. In aortic regions which were still deendothelialized, accumulation was diffuse and labile. In contrast, at the edges of the islands of regenerating endothelium, LDL accumulation was intensely focal, as it is in human atherosclerotic lesions, and persisted for at least 40 h after injection in spite of falling levels of radiolabeled LDL in plasma [Chang, M. Y., et al. (1992) Arterioscler. Thromb. 12, 1088-1098]. In the present study, modified LDLs with gradations in charge change were prepared to clarify the role of changes in surface charge on focal aortic LDL accumulation. Oxidized LDL (weakly anionized), desialated LDL (weakly cationized), and reductively methylated LDL (no change in net charge) all accumulated focally. Focal accumulation of native LDL also occurred in ballooned rabbits fed probucol to inhibit LDL oxidation. Strongly anionized succinylated and diazobenzenearsonylated LDL and strongly cationized dimethylpropanediamine LDL did not accumulate focally. The results support the concept that focal sequestration of LDL in arterial lesions is mediated by specific, oxidation-independent patterns of charge and polarity on LDL which are disrupted by major changes in LDL surface charge.

Inhibition of smooth muscle cell proliferation and experimental angioplasty restenosis by beta-cyclodextrin tetradecasulfate.

Heparin inhibits smooth muscle cell proliferation in vitro, a property that makes it potentially useful in preventing restenosis after angioplasty. Its utility in this setting is limited by the inability to use high doses (secondary to anticoagulant effects) and the need for subcutaneous administration. We tested the ability of beta-cyclodextrin tetradecasulfate (CDT), a nonanticoagulant synthetic heparin mimic, to inhibit smooth muscle cell proliferation in vitro and tested its efficacy when orally administered for the prevention of angioplasty restenosis in a rabbit atherosclerosis model. Vascular smooth muscle cells were cultured from rabbit aortas by the explant technique. Passaged cells were plated at low density in microtiter plates in the presence or absence of varying concentrations of heparin or CDT in culture medium containing 10% fetal calf serum. Using both 3H-thymidine incorporation and total protein assays, both heparin and CDT caused a similar dose-dependent inhibition of proliferation. We next tested the effect of orally administered CDT in the prevention of restenosis in focal femoral artery arteriosclerotic lesions created in hypercholesterolemic New Zealand White rabbits by air-dessication endothelial injury and subsequent peripheral angioplasty. Animals were followed up for 1 month and were fed normal chow supplemented by tap water with or without CDT. In animals receiving the highest concentration of CDT (2 mg/mL drinking water), the percentage of arterial cross-sectional area with intimal hyperplasia decreased from 50.5 +/- 1.7% (control) to 26.9 +/- 2.2% (p < 0.001), with the intimal/medial ratio being decreased from 1.4 +/- 0.4 to 0.5 +/- 0.2 (p = 0.056).(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelial Expression of a Mononuclear Leukocyte Adhesion Molecule During Atherogenesis

An inducible rabbit endothelial adhesion molecule that is selective for mononuclear leukocytes has been identified. This adhesion protein was expressed on the surface of activated cultured endothelium in two forms, 118 and 98 kilodaltons, the amino-terminal sequence of each being highly homologous to human VCAM-1. In dietary hypercholesterolemic and Watanabe heritable hyperlipidemic rabbit models of atherosclerosis, this adhesion molecule was found to be expressed in a localized fashion by aortic endothelium that overlies early foam cell lesions. This lesion-localized expression suggests a potential endothelium-dependent mechanism for mononuclear leukocyte recruitment during atherogenesis and may provide a molecular marker for early atherosclerosis.