应激对兔动脉粥样硬化及外周血黏附分子CD11a的影响和普萘洛尔干预作用

目的研究应激对实验性家兔动脉粥样硬化(AS)斑块的病理形态学和外周血黏附分子CD11a的影响及普萘洛尔的干预作用,以探讨普萘洛尔稳定AS斑块的免疫学机制。方法27只健康雄性中国家兔,随机分为正常空白对照(8只)、模型对照组(8只)和普萘洛尔组(8只),余3只为单纯模型组,用于动脉粥样硬化模型组织形态学观察。正常空白对照,给予普通饮食,其他3组给予高脂饮食,建立动脉粥样硬化模型,给予刺激,建立应激动物模型(除外单纯模型组),取外周血流式细胞术检测应激前后表达CD11a白细胞的阳性百分率。病理切片观察主动脉AS斑块形成情况,检测斑块内巨噬细胞含量。结果应激可导致模型对照组和空白对照组外周血黏附分子CD11a水平升高;但普萘洛尔组外周血CD11a白细胞的阳性百分率和AS斑块内巨噬细胞含量低于模型组(P<0.05)。结论应激可导致黏附分子CD11a水平升高。普萘洛尔可在一定程度上防止应激所导致的外周血黏附分子CD11a水平的升高。     

Anti-inflammatory drugs in experimental atherosclerosis. 7. Spontaneous atherosclerosis in WHHL rabbits and inhibition by cortisone acetate

The Watanabe heritable hyperlipidemic (WHHL) rabbit, an animal model for familial hypercholesterolemia, has a deficiency in low density lipoprotein (LDL) receptor binding and exhibits elevated plasma lipoprotein levels and spontaneous atherosclerosis. Since atherosclerotic plaque formation has a number of features in common with the inflammatory process, we have investigated the effect of dietary supplementation with an anti-inflammatory steroid (cortisone acetate, 5 mg daily for 3 months) on atherosclerosis using the WHHL rabbit as a model. Atherosclerotic plaque formation in cortisone-fed animals was reduced by about 60% compared to control WHHL rabbits. Steroid administration increased circulating cholesterol levels modestly and triglycerides were increased about 6-fold. While very low density lipoprotein (VLDL)-cholesterol was increased, LDL-cholesterol levels were decreased and the particle was more triglyceride-enriched as well as less dense. Steroid-fed animals also exhibited decreased platelet aggregation and increased aortic 15-lipoxygenase activity. The histological observations showed typical fibrous plaques in aortas of both control and cortisone-fed rabbits, with intima thickened by foamy macrophages and subcellular lipoproteinaceous debris covered by a fibrous cap. These findings thus indicate that steroids reduce the rate of plaque initiation or progression but do not significantly change the histological appearance of the lesion.     

普萘洛尔对高脂血症兔外周血白细胞CD11a表达及动脉粥样硬化病变形成的影响

目的探讨普萘洛尔对高脂血症兔外周血白细胞CD11a的表达及动脉粥样硬化病变形成的影响。方法选用21只健康雄性中国家兔随机分为正常组、高脂模型组和普萘洛尔组,普萘洛尔组给予普萘洛尔(每天5mg/kg)灌胃。16周后取外周血流式细胞术检测白细胞CD11a表达的阳性率。观察主动脉粥样斑块形成情况,检测斑块面积与内膜面积百分比和动脉粥样硬化斑块巨噬细胞含量。结果普萘洛尔组动脉粥样硬化斑块病变程度较模型组明显减轻,正常组无动脉粥样硬化斑块形成。普萘洛尔组动脉粥样硬化斑块面积与内膜面积比为59.1%±11.3%,斑块内巨噬细胞含量为56.3%±4.9%,外周血CD11a阳性的白细胞比率为61.9%±4.2%;模型组分别为78.3%±6.7%、70.6%±5.6%和74.3%±3.6%,差异有显著性(P<0.05)。结论普萘洛尔可通过减轻动脉粥样硬化斑块内炎症反应而延缓动脉粥样硬化斑块形成,增加动脉粥样硬化斑块稳定性。     

Atherosclerotic aortic gangliosides enhance integrin-mediated platelet adhesion to collagen

Gangliosides, sialic acid-containing glycosphingolipids, accumulate in atherosclerotic vessels. Their role in the pathogenesis of atherosclerosis is unknown. Gangliosides isolated from tumor cells promote collagen-stimulated platelet aggregation and ATP secretion and enhance platelet adhesion to immobilized collagen. These activities are all mediated by ganglioside effects on the platelet integrin collagen receptor alpha2beta1. Therefore, we hypothesized that gangliosides isolated from atherosclerotic plaques would enhance platelet adhesion to immobilized collagen, a major component of the subendothelial matrix of blood vessels. Furthermore, we questioned whether this effect of atherosclerotic gangliosides might play a role in the pathogenesis of atherosclerosis. To test this hypothesis, we isolated the gangliosides from postmortem aortas of patients with extensive atherosclerotic disease and examined their effects on platelet adhesion. Samples of aortic tissue taken from areas involved with atherosclerotic plaque demonstrated accumulation of gangliosides (64.9+/-6.5 nmol/g wet weight) compared with gangliosides isolated from control normal aortic tissue taken from children who died of noncardiac causes (NAGs; 21.1+/-6.4 nmol/g wet weight). Interestingly, samples of tissue taken from diseased aortas but from areas not involved with gross plaque formation also demonstrated ganglioside accumulation (47.6+/-12.8 nmol/g wet weight). Next, the activity of each of these gangliosides on platelet adhesion to immobilized type I collagen was studied. Atherosclerotic aortic gangliosides (AAGs) as well as those isolated from grossly unaffected areas of the same aorta (UAGs) both increased platelet adhesion compared with control NAGs (OD570, 0. 37+/-0.11 and 0.29+/-0.14 versus 0.16+/-0.07, respectively; P<0.01 and P<0.05, respectively). These OD570 values corresponded to 9x10(5), 8x10(4), and 6x10(3) platelets per well after preincubation with 5 micromol/L AAG, UAG, and NAG, respectively. Increased adhesion was observed after preincubation with as little as 0.5 micromol/L AAG, and maximal adhesion was seen at 2.5 micromol/L, with a plateau extending to the highest concentration tested, 10 micromol/L. The effect of AAGs on platelet adhesion to collagen was abrogated by incubation of treated platelets with F-17 anti-alpha2 monoclonal antibody (OD570, 0.13+/-0.02). Finally, the effects of the major individual gangliosides isolated from atherosclerotic tissues, GM3 and GD3, were tested. GM3 increased adhesion to collagen (OD570, 0.415+/-0.06) as did GD3 (0.31+/-0.08). Similar to that of AAGs, the effect of both molecules was blocked by F-17 (0. 09+/-0.04 and 0.13+/-0.06, respectively). These experiments demonstrate that accumulated atherosclerotic gangliosides promote platelet adhesion to collagen, the major component of the subendothelial matrix. Furthermore, this activity is mediated by an effect of the gangliosides on the collagen-binding integrin alpha2beta1. This activity may provide a mechanism for the development of platelet thrombi at sites where atherosclerotic gangliosides accumulate and help to explain the role of platelets in the process of atherosclerotic disease progression.     

Immunolocalization of apolipoproteins in aortic atherosclerosis in American youths and young adults: findings from the PDAY study

The immunohistochemical distribution of apolipoproteins in the abdominal aortas of 142 men, 15-34 years of age, collected in a cooperative multicenter study group (Pathobiological Determinants of Atherosclerosis in Youth) was examined in relationship to serum VLDL+LDL+HDL cholesterol levels. ApoB deposits were limited to the intima of specimens with intimal fibro cellular thickening or atherosclerotic lesions. Apo A-I, E and J were observed in both the intima and media of the aortas with intimal lesions. The pattern of apoJ distribution was similar to that of apoA-I and E. The distribution patterns of these apolipoproteins in these young adults were very similar to those in adults and old men seen in an earlier study. The extent of apolipoprotein distribution in the intima and media increased with age and the stage of atherosclerosis development, but was not correlated significantly with serum VLDL+LDL or HDL cholesterol levels. The infiltration of lipoprotein particles into the aortic wall seems to be more strongly associated with the progression of intimal lesions rather than with serum cholesterol levels.     

A matrix metalloproteinase inhibitor, ONO-4817, suppresses the development of aortic intimal hyperplasia in experimental hyperlipidemic rabbit

Inhibition of matrix metalloproteinases (MMPs) would be expected to suppress atherosclerotic neointimal proliferation and thus limit atheromatous plaque progression, but this has not yet been demonstrated morphologically in atherosclerotic intimal hyperplasia induced by cholesterol loading in experimental animals. We therefore investigated whether a broad-spectrum MMP inhibitor (MMPi), ONO-4817, could inhibit the development of intimal hyperplasia in male hyperlipidemic rabbits (n = 6) fed laboratory chow supplemented with 1% cholesterol for 2 months followed by a 1% cholesterol diet plus 100 mg/kg ONO-4817 for another month (Chol + ONO group). Control animals (n = 6) received no ONO-4817. When the aortas were studied both histologically and immunohistochemically, intimal hyperplasia was inhibited in Chol + ONO rabbits. The distribution of macrophages and MMP-12 in the hyperplastic tissue of the Chol + ONO rabbits was limited to the luminal side of the lesions. No such limitation in the distribution of macrophages and MMP-12 was observed in the control group. The distribution of smooth muscle cells in the hyperplastic tissue was not different between the Chol + ONO and control groups. However, the distribution of MMP-2 and MMP-12 was limited to the luminal side of lesions in the Chol + ONO group. This is the first reported evidence that an MMPi can suppress the development of intimal hyperplasia in hyperlipidemic rabbits.     

Aging influences development and progression of early aortic atherosclerotic lesions in cholesterol-fed rabbits

The arterial wall in aged animals shows an increased susceptibility to develop atherosclerotic lesions, although the mechanisms by which aging acts are still unclear. We investigated early aortic lesions in aged rabbits (5 to 6 years old, AH group) and young rabbits (2 months old, YH group) after 2 months of 0.2% cholesterol feeding. Fatty streaks or spots mainly in the proximal segments occupied a relative surface area that was greater in AH than in YH rabbits, although plasma cholesterol and lipoprotein levels did not differ. YH lesions showed an irregular endothelial profile mainly from accumulations of large, rounded, RAM 11-positive macrophagic foam cells. There was a higher percentage of myocytic, CD-5-positive, proliferating, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells and larger accumulation of glycosaminoglycans in AH fatty streaks than in YH lesions. Ligation-mediated polymerase chain reaction confirmed differences in apoptosis. Early fibromuscular coats and subendothelial plasma-like insudate were also observed in AH lesions. Aged-matched normocholesterolemic rabbits showed a diffuse aortic intimal thickening composed of myocytic cells with a synthetic phenotype and extracellular matrix rich in glycosaminoglycans. In addition, in aged rabbits, we observed a spontaneous increase of monocytes adhering to the endothelial surface and a reduced expression of endothelial nitric oxide synthase in areas distant from the branches. These plasma cholesterol-independent spontaneous changes in the aortic wall of aged rabbits seem to act as a multiple atherogenic risk factor. Moreover, age-related differences in the distribution, composition, and proliferative and apoptotic rates represent crucial events during the progression of early fatty streaks to advanced plaques.     

Endothelial von Willebrand factor recruits platelets to atherosclerosis-prone sites in response to hypercholesterolemia

Platelets are thought to play a causal role during atherogenesis. Platelet-endothelial interactions in vivo and their molecular mechanisms under shear are, however, incompletely characterized. Here, an in vivo platelet homing assay was used in hypercholesterolemic rabbits to track platelet adhesion to plaque predilection sites. The role of platelet versus aortic endothelial cell (EC) activation was studied in an ex vivo flow chamber. Pathways of human platelet immobilization were detailed during in vitro perfusion studies. In rabbits, a 0.125% cholesterol diet induced no lesions within 3 months, but fatty streaks were found after 12 months. ECs at segmental arteries of 3- month rabbits expressed more von Willebrand factor (VWF) and recruited 5-fold more platelets than controls (P <.05, n = 5 and 4, respectively). The 3-month ostia had an increased likelihood to recruit platelets compared to control ostia (56% versus 18%, P <.0001, n = 89 and 63, respectively). Ex vivo, the adhesion of 3-month platelets to 3-month aortas was 8.4-fold increased compared to control studies (P <.01, n = 7 and 5, respectively). In vitro, endothelial VWF-platelet glycoprotein (GP) Ib and platelet P-selectin- endothelial P-selectin glycoprotein ligand 1 interactions accounted in combination for 83% of translocation and 90% of adhesion (P <.01, n = 4) of activated human platelets to activated human ECs. Platelet tethering was mainly mediated by platelet GPIb alpha, whereas platelet GPIIb/IIIa contributed 20% to arrest (P <.05). In conclusion, hypercholesterolemia primes platelets for recruitment via VWF, GPIb alpha, and P-selectin to lesion-prone sites, before lesions are detectable.     

Cholesterol feeding increases plasma and aortic tissue cholesterol oxide levels in parallel: further evidence for the role of cholesterol oxidation in atherosclerosis.

To determine the relationship between plasma and arterial wall oxysterols, plasma and aortic tissue from 7 New Zealand White rabbits fed a high cholesterol (1%) diet for 6 weeks was compared to plasma and aortic tissue from 7 normocholesterolemic rabbits fed standard rabbit chow. Cholesterol and cholesterol oxide fractions were isolated and analyzed by gas chromatography. Normocholesterolemic plasma and aortic tissue contained low levels of cholest-5-ene-3 beta, 7 alpha-diol, cholesta-3,5-dien-7-one, 5,6 alpha-epoxy-5 alpha-cholestan-3 alpha-ol, cholest-5-ene-3 beta, 7 beta-diol, and 5 alpha-cholestane-3 beta, 5,6 beta-triol while hypercholesterolemic plasma and atherosclerotic aorta contained significantly higher levels (P less than 0.05) of these products. Furthermore, 5,6 beta-epoxy-5 alpha-cholestan-3 beta-ol not found in normocholesterolemic plasma or aortic tissue was present in substantial amounts in both hypercholesterolemic plasma and atherosclerotic aortic tissue. Cholest-5-ene-3 beta,25-diol and 3 beta-hydroxycholest-5-ene-7- one not present in normocholesterolemic aorta were present in the atherosclerotic aorta. The oxysterol chromatographic patterns of normocholesterolemic plasma and normocholesterolemic aortic tissue were similar to each other as were the oxysterol chromatographic patterns of hypercholesterolemic plasma and atherosclerotic aortic tissue. The chromatographic patterns between the normocholesterolemic and hypercholesterolemic samples differed however. Possible absorption of the low levels of cholesterol oxides present in the cholesterol feed could account for the elevation of only some of the oxysterols. We conclude that cholesterol oxides exist at some basal level in normocholesterolemia and that these levels are increased by cholesterol-feeding which results in hypercholesterolemia. Our findings demonstrate that there is a strong relationship between plasma and aortic arterial wall levels of cholesterol oxides and suggest that in addition to exogenous sources, formation of cholesterol oxides proceeds via free radical oxidation acting upon elevated cholesterol levels resulting in the accumulation of these potentially cytotoxic and atherogenic products.     

Propionyl-L-carnitine reduces intimal hyperplasia after injury in normocholesterolemic rabbit carotid artery by modulating proliferation and caspase 3-dependent apoptosis of vascular smooth muscle cells.

Previously we documented that propionyl-L-carnitine (PLC) reduces the growth of atherosclerotic lesions in cholesterol-fed aged rabbits in association with a decrease of plaque smooth muscle cell (SMC) proliferation and plasma triglycerides. To clarify whether PLC might influence SMC growth through mechanisms other than triglyceride lowering, we investigated the effect of a daily treatment per os with PLC on carotid intimal hyperplasia after ballooning in normocholesterolemic rabbits. PLC did not induce variations of plasma triglyceride and cholesterol. One week later, the number of proliferating SMCs was reduced in PLC as compared with controls. After 3 weeks, morphometric analysis demonstrated a reduced neointimal relative volume and percentage of stenosis but not vessel area in PLC as compared with controls. This associated with an intimal reduced SMC number and an increased apoptotic rate as detected by nick-end labelling (TUNEL) and ligation-mediated polymerase chain reaction (PCR). Western blotting also demonstrated an increase of caspase-3 cleavage in PLC carotids. Antiproliferative and pro-apoptotic effects of PLC were confirmed in vitro on actively proliferating and serum deprived SMCs, respectively. Molecules with an additional cell-specific, pro-apoptotic action may represent a new therapeutic tool in reducing intimal SMC hyperplasia following angioplasty or stenting procedures.     

动脉粥样硬化脂质过氧化损伤机制的实验研究

喂饲高胆固醇诱发的实验性动脉粥样硬化（ＡＳ）兔血清总胆固醇（ＴＣ）及丙二醛（ＭＤＡ）水平明显升高，血小板膜流动性明显降低。停喂胆固醇后，尽管血清ＴＣ渐趋恢复正常，但血清ＭＤＡ并无明显降低，血小板膜流动性仍未恢复，动脉粥样硬化斑块面积及动脉壁胆固醇含量继续增加。结果表明，脂质过氧化损伤是促使ＡＳ发生发展的重要因素之一。这提示在降脂治疗的同时还需抗脂质过氧化。     

Induction of IG9 monocyte adhesion molecule expression in smooth muscle and endothelial cells after balloon arterial injury in cholesterol-fed rabbits

The expression of monocyte-specific adhesion molecules and chemokines by cell types within the vessel wall plays an important role in foam cell accumulation during atherosclerotic plaque development. We previously identified IG9, a novel monocyte adhesion protein that is expressed on endothelial cells (ECs) overlying human and rabbit advanced atherosclerotic plaques. The present study was designed to determine the temporal and spatial expression of IG9 and the chemokine, monocyte chemoattractant protein-1 (MCP-1), after balloon injury with (double injury) or without (single injury) prior air desiccation EC injury in the femoral arteries of rabbits fed a high-cholesterol diet. By immunohistochemical analyses, intense reactivity with monoclonal antibodies to IG9 and MCP-1 was detected 24 hours after single injury in medial smooth muscle cells (SMCs) and in SMCs of adventitial microvessels. However, monocyte infiltration of the tunica media was minimal or not detected in these sections. IG9 and MCP-1 antibody reactivity in vessel sections 28 days after single injury and 24 hours, 7 days, and 28 days after double injury was localized to medial and neointimal SMCs, foam cells, and luminal ECs overlying the plaques. Uninjured rabbit (cholesterol or normal diet) vessel sections exhibited minimal IG9 and MCP-1 immunostaining. In vitro studies using human aortic SMCs demonstrated IG9 protein induction after 24 hours of treatment with platelet-derived growth factor-BB and interferon-gamma or epidermal growth factor. IG9 expression was further increased by pretreatment of SMCs with the proatherogenic lipid, minimally oxidized low density lipoprotein. After balloon injury (24 hours), IG9 is induced in vascular SMCs before the detectable accumulation of monocytes within the vessel wall. Thus, the expression of IG9 by SMCs as well as by ECs may be an important factor in the accumulation of foam cells in atherosclerotic plaque development after arterial injury.     

芝麻素对动脉粥样硬化斑块及主动脉壁VCAM-1表达的影响

目的观察比较芝麻素和阿托伐他汀对兔实验性动脉粥样硬化（AS）斑块形成及主动脉壁细胞黏附分子1（VCAM-1）表达的影响,探讨芝麻素在预防和治疗AS中的作用。方法将日本大耳白兔18只随机分为芝麻素组、阿托伐他汀组和阳性对照组,基础饲料喂养。给药8周后测定各组0、5和8周末LDL-C水平;实验结束时取主动脉,常规HE染色及免疫组织化学染色,观察主动脉形态学变化和血管壁斑块组织的变化,定量分析血管VCAM-1表达强度变化。结果与阳性对照组相比,芝麻素组和阿托伐他汀组LDL-C水平显著降低（P〈0.01）,主动脉病理改变和血管壁斑块组织免疫着色明显减轻（P〈0.01）,主动脉壁VCAM-1表达水平分别下调27.59%和45.97%。与阿托伐他汀比较,芝麻素明显减轻主动脉中膜的厚度（P〈0.01）。结论芝麻素具有降低血脂、防治AS的作用。     

Impact of glycoprotein VI and platelet adhesion on atherosclerosis—A possible role of fibronectin

Glycoprotein VI (GPVI) mediates binding of platelets to subendothelial collagen during acute arterial thrombosis. GPVI interactions with the activated atherosclerotic vascular endothelium during early atherosclerosis, however, are not well understood. In ApoE−/− mice, platelet adhesion to atherosclerotic arteries was increased, as measured by intravital microscopy. This platelet adhesion was significantly inhibited by IV injection of GPVI-Fc (1 mg/kg body weight). Atherosclerosis in ApoE−/− mice was attenuated both after 7 and 10 weeks of treatment with the anti-GPVI antibody JAQ1 (2 mg/kg body weight i.p. twice weekly). Binding of GPVI-Fc (1 mg/kg IV) occurred to deeper layers, but also to the luminal site of plaques in atherosclerotic rabbits, but not to the vessel wall of healthy littermates. Gene transfer of GPVI-Fc to the carotid vascular wall significantly attenuated athero-progression and endothelial dysfunction in atherosclerotic rabbits in vivo. Specific binding of the soluble GPVI receptor (GPVI-Fc) to fibronectin was found in vitro to coated ELISA plates. Platelet adhesion to fibronectin was significantly inhibited both by GPVI-Fc and by the anti-GPVI antibody 5C4 ex vivo in flow chamber experiments. GPVI plays a role in platelet adhesion to atherosclerotic endothelium in the absence of plaque rupture. Inhibition of GPVI both via GPVI-Fc and anti-GPVI-antibodies results in protection against atherosclerosis in both cholesterol-fed rabbits and ApoE−/− mice. This novel mechanism of GPVI-mediated platelet adhesion-possibly via fibronectin-could relevantly contribute to platelet-triggered atheroprogression.     

VCAM-1 expression precedes macrophage infiltration into subendothelium of vein grafts interposed into carotid arteries in hypercholesterolemic rabbits--a potential role in vein graft atherosclerosis

Intimal hyperplasia and atherosclerosis are major causes of late vein graft failure after coronary artery bypass surgery. Hypercholesterolemia appears to be a key risk factor for atherosclerosis in vein grafts as well as in native arteries. We used a rabbit model of interposition jugular vein graft to the carotid artery and compared intimal thickening, macrophage accumulation, and VCAM-1 expression between hypercholesterolemic (H group) and normocholesterolemic (N group) rabbits. Fifty-nine rabbits were divided into H and N groups. Intimal thickening in vein grafts was approximately three times more prominent in the H group than in the N group. Macrophage accumulation progressively increased with time in H group vein grafts, although it was negligible in the N group. In the H group, moreover, macrophages were initially more abundant in deep intima, and subsequently accumulated in subendothelium of the grafted vein. VCAM-1 expression in luminal endothelial cells of the grafted veins was time-dependently increased after the vein graft surgery in both the H and N groups, and was more prominent in the H group. Comparison of the time-courses between macrophage accumulation and VCAM-1 expression revealed that VCAM-1 expression in luminal endothelium preceded subendothelial accumulation of macrophages. VCAM-1 expression and macrophage accumulation may be key factors which regulate progression of vein graft atherosclerosis.     

Aortic pulse wave velocity, elasticity, and composition in a nonhuman primate model of atherosclerosis.

Aortic pulse wave velocity was determined in Macaca fascicularis monkeys fed either atherogenic or control diets for 36 months. The foot-to-foot velocity and apparent phase velocities of the second through seventh Fourier harmonics at a given diastolic pressure in the atherosclerotic monkeys were 1.5 to 2.0 times the values for the control animals. More than 80% of the aortic intimal surface of the atherosclerotic monkeys was covered with fibrous or fatty plaque, which approximately doubled wall thickness and wall thickness to radius ratio. Angiochemical evaluations showed no difference in collagen or elastin concentration (as a fraction of lipid and mineral-free dried aorta), but the atherosclerotic aortas were 1.5 to 2.0 times that of control in collagen and elastin content (defined as the absolute quantity beneath a square centimeter of intimal surface). Total cholesterol and calcium concentrations in the atherosclerotic aortas were more than 10 times the values for the control aortas. The static circumferential distensibility of the excised atherosclerotic aortas was significantly less than control, but there was no difference in incremental (Young's) modulus of elasticity. The in vitro pressure-strain elastic modulus of the atherosclerotic aortas was more than twice that of control, which was predicted from the enhanced wave velocity. The significantly increased stiffness of the atherosclerotic arteries appeared to be due mainly to the increased wall thickness caused by the atherosclerotic plaques rather than to material changes described by Young's modulus. Extensive medial damage, however, also was present and could have had a major influence on stiffness. Atherosclerosis therefore can result in increased aortic stiffening, detectable by pulse wave velocity, even if there is no change in the overall Young's modulus of elasticity.     

Plaque Rupture and Thrombosis: the Value of the Atherosclerotic Rabbit Model in Defining the Mechanism

Persistent inflammation and mechanical injury associated with cholesterol crystal accretion within atherosclerotic plaques typically precedes plaque disruption (rupture and/or erosion) and thrombosis—often the terminal events of atherosclerotic cardiovascular disease. To elucidate the mechanisms of these events, the atherosclerotic rabbit model provides a unique and powerful tool that facilitates studies of atherogenesis starting with plaque buildup to eventual disruption. Examination of human coronary arteries obtained from patients who died with myocardial infarction demonstrates evidence of cholesterol crystals perforating the plaque cap and intimal surface of the arterial wall that can lead to rupture. These observations were made possible by omitting ethanol, an avid lipid solvent, from the tissue processing steps. Importantly, the atherosclerotic rabbit model exhibits a similar pathology of cholesterol crystals perforating the intimal surface as seen in ruptured human plaques. Local and systemic inflammatory responses in the model are also similar to those observed in humans. The strong parallel between the rabbit and human pathology validates the atherosclerotic rabbit model as a predictor of human pathophysiology of atherosclerosis. Thus, the atherosclerotic rabbit model can be used with confidence to evaluate diagnostic imaging and efficacy of novel anti-atherosclerotic therapy.     

Increased advanced glycation end products in atherosclerotic lesions of patients with end-stage renal disease

Although advanced glycation end products (AGEs) are increased in the serum and tissues of patients with end-stage renal disease, little is known about the role of AGEs in atherogenesis. We therefore carried out an immunohistochemical study on the accumulation of AGEs and apolipoprotein B in the human aortas of diabetic and nondiabetic subjects with end-stage renal disease. The atherosclerotic lesions included diffuse intimal thickening, fatty streaks and atherosclerotic plaque. We used antibodies against two different epitopes of AGE structures, i.e. an N^ε-(carboxymethyl)lysine-protein adduct (CML) and a structure(s) other than CML (nonCML). The area that was positive for an antigen as a percentage of the total area (%Ar) was determined morphometrically, using an NIH-image program. In diffuse intimal thickening, atherosclerotic plaque and tunica media, the %Ar of CML and nonCML was significantly greater in diabetic or nondiabetic subjects with end-stage renal disease than in control subjects without end-stage renal disease. In fatty streaks, the %Ar of nonCML was significantly greater in nondiabetic subjects with end-stage renal disease than in control subjects, while no difference in the %Ar of CML was found between the subjects with or without end-stage renal disease. Nondiabetic subjects with end-stage renal disease showed a significantly increased %Ar of apolipoprotein B in fatty streaks and atherosclerotic plaque than the control subjects. The %Ar of CML and nonCML significantly correlated with the duration of hemodialysis in diffuse intimal thickening and atherosclerotic plaque of subjects with end-stage renal disease, but not in fatty streaks. On the other hand, the %Ar was not related to the duration of diabetes in any of the lesions in the diabetic subjects with end-stage renal disease. In diffuse intimal thickening and atherosclerotic plaque, subjects with end-stage renal disease showed a significant correlation between the %Ar of apolipoprotein B and AGEs (CML and nonCML), as well as their immunohistochemical colocalization. These results suggest that impaired AGE clearance may cause the increased accumulation of AGEs in the aortic wall of subjects with end-stage renal disease, thus resulting in the rapid progression of atherosclerosis. The accumulation of AGEs may be related to an enhanced LDL deposition in atherosclerotic lesions of subjects with end-stage renal disease.     

Patterns of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 expression in rabbit and mouse atherosclerotic lesions and at sites predisposed to lesion formation.

The recruitment of mononuclear leukocytes and formation of intimal macrophage-rich lesions at specific sites of the arterial tree are key events in atherogenesis. Inducible endothelial cell adhesion molecules may participate in this process. In aortas of normal chow-fed wild-type mice and rabbits, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), but not E-selectin, were expressed by endothelial cells in regions predisposed to atherosclerotic lesion formation. En face confocal microscopy of the mouse ascending aorta and proximal arch demonstrated that VCAM-1 expression was increased on the endothelial cell surface in lesion-prone areas. ICAM-1 expression extended into areas protected from lesion formation. Hypercholesterolemia induced atherosclerotic lesion formation in rabbits, LDL receptor and apolipoprotein E knockout mice, and Northern blot analysis demonstrated increased steady-state mRNA levels of VCAM-1 and ICAM-1, but not of E-selectin. Immunohistochemical staining revealed that VCAM-1 and ICAM-1 were expressed predominantly by endothelium in early lesions and by intimal cells in more advanced lesions. In early and advanced lesions, staining was most intense in endothelial cells at and adjacent to lesion borders. ICAM-1 staining extended into the uninvolved aorta. These expression patterns were highly reproducible in both species. The only difference was that VCAM-1 expression in endothelium over the central portions of lesions was found frequently in rabbits and rarely in mice. The expression of VCAM-1 by arterial endothelium in normal animals may represent a pathogenic mechanism or a phenotypic marker of predisposition to atherogenesis.