Atherosclerosis In WHHL Rabbits Research Articles

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

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

CRP—Marker or Maker of Cardiovascular Disease?

C-reactive protein (CRP) has emerged as an interesting novel and potentially clinically useful marker for increased cardiovascular risk.1,2 This is an attractive concept because atherosclerosis is a disease characterized by chronic arterial inflammation3,4 and suggests the possibility that subclinical states of atherosclerosis can be identified by an increase in circulating markers of inflammation before acute events occur. Based on data obtained primarily from in vitro studies it has also been proposed that CRP in itself is actively contributing to disease progression and that it should be considered as true risk factor and consequently as a target for intervention. However, in the present issue of Arteriosclerosis, Thrombosis, and Vascular Biology , two independent reports demonstrate that transgenic overexpression of CRP does not affect the development of atherosclerosis in mice, suggesting that this is not the case. See pages 1635 and 1641 The association between moderately elevated CRP levels and an increased risk for development of cardiovascular disease is well established. Although the increase in risk may have been overestimated in initial studies, recent meta-analysis comprising >7000 patients with coronary events shows that subjects with CRP in the upper tertile have a 50% increased risk for development of acute cardiovascular events.2 There are several possible explanations for this association (Figure). (1) The inflammatory process in arterial tissue affected by atherosclerosis results in release of cytokines into the circulation that subsequently activates expression of CRP in the liver. Plasma CRP levels would then reflect the severity of atherosclerosis and, as a consequence, the risk for development of clinical events. If CRP in addition …

Effects of $alpha;-tocopherol and astaxanthin on LDL oxidation and atherosclerosis in WHHL rabbits

Effects of $alpha;-tocopherol and astaxanthin on LDL oxidation and atherosclerosis in WHHL rabbits

N,N'-Diacetyl-L-cystine reduces atherosclerosis in WHHL rabbits

N,N'-Diacetyl-L-cystine reduces atherosclerosis in WHHL rabbits

1.P.114 Aortic and coronary atherosclerosis in WHHL rabbits from 6 to 75 weeks age

1.P.114 Aortic and coronary atherosclerosis in WHHL rabbits from 6 to 75 weeks age

Coronary and aortic atherosclerosis in WHHL rabbits, an animal model of familial hypercholesterolemia

Coronary and aortic atherosclerosis in WHHL rabbits, an animal model of familial hypercholesterolemia

Apolipoprotein E prevents the progression of atherosclerosis in WHHL rabbits and transgenic mice

Apolipoprotein E prevents the progression of atherosclerosis in WHHL rabbits and transgenic mice

Immunohistochemical and quantitative analysis of cellular and extracellular components of aortic atherosclerosis in WHHL rabbits.

To investigate changes in the major components of atherosclerotic lesions during the progression of this disease, we measured the lesional areas of macrophages, smooth muscle cells, collagen fibers, and extracellular lipid deposits in the aortas of WHHL rabbits. Aortic segments with lesions of various stages were stained for histological and immunohistochemical examination, and the area of each lesional component was measured by a color image analyzer. In the early fatty streaks observed in 3-month-old rabbits, macrophages were predominant in the intima and were also observed in the inner layer of the media. In the transitional lesions (fibro-fatty streaks) found in rabbits at 11 to 15 months of age, an increase in the lesional area of macrophages was prominent compared to other lesional components. Thus, macrophages may play an important role in the progression of aortic atherosclerosis at this stage. In advanced complicated lesions observed in rabbits at 20 to 24 months of age, the area of macrophages and smooth muscle cells did not increase, whereas the area of collagen fibers and extracellular lipid deposits increased. Therefore, both the disruption of foam cells and fibrosis may play an important role in the progression of atherosclerosis at this stage.

Role of macrophage colony-stimulating factor in the initial process of atherosclerosis.

The early atherosclerotic lesion is characterized by the presence of macrophage-derived foam cells. Macrophage colony-stimulating factor (M-CSF) specifically stimulates the functions of the monocyte-macrophages. To elucidate the role of M-CSF in the atherogenic process in vitro and in vivo, we studied the effects of M-CSF on enzyme activities of acidic cholesteryl ester (CE) hydrolase, neutral CE hydrolase, and acyl-coenzyme A:cholesterol acyltransferase (ACAT), and 300 micrograms of M-CSF was intravenously injected into WHHL rabbits aged 2.5 months for 8.5 months. M-CSF (100 ng/ml) enhanced acidic and neutral CE hydrolase, and ACAT activities by 3.2-fold, 4-fold, and 2.3-fold, respectively, in the presence of acetyl LDL, and M-CSF increased ratios of both acidic and neutral CE hydrolase activities to ACAT activity. After M-CSF injection into WHHL rabbits, we found very retarded progression of atherosclerosis. The accumulation of cholesterol ester was remarkably decreased in the aortae of M-CSF-treated animals (0.60 +/- 0.32 mg/g tissue), as compared to those of controls (4.21 +/- 0.65 mg/g tissue). The results suggest that M-CSF prevents the progression of atherosclerosis in WHHL rabbits by increasing net hydrolysis of cholesteryl ester in macrophages.

Atherosclerosis in Watanabe heritable hyperlipidaemic rabbits

The spontaneous development of atherosclerotic disease in 38 homozygous and 34 heterozygous Watanabe heritable hyperlipidaemic rabbits was evaluated by qualitative and quantitative light microscopy in aorta, coronary, pulmonary and renal arteries, by naked eye and macroscopic morphometric estimation of aortic atherosclerosis extent and by biochemical analysis of aortic cholesterol content. No noteworthy atherosclerosis was demonstrated within 19 months in heterozygous rabbits. In homozygous rabbits, atherosclerotic lesions were seen from the age of 4 months and progressed with age. All 19-month-old rabbits had severe atherosclerotic disease. As much as 64% of the variation in atherosclerosis extent/severity could be explained by serum cholesterol and age. A highly significant correlation between the various methods for quantitation of atherosclerosis extent and/or severity was demonstrated, suggesting that quantitative microscopy, macroscopic morphometry and determination of aortic cholesterol content may be equally valid as a measure of atherosclerosis in WHHL rabbits and are therefore interchangeable.

The effect of cholesterol reduction on the endothelial function and progression of atherosclerosis in WHHL rabbits

In 3-month-old homozygous Watanabe heritable hyperlipidemic (WHHL[ rabbits the effect of treatment with the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA[ reductase inhibitor pravastatin was studied for 9 months and related to the endothelial function of the coronary arteries of isolated hearts and rings of the distal abdominal aorta. Oral administration of pravastatin in doses up to 40 mg/kg per day significantly decreased plasma cholesterol by 51% in comparison to untreated WHHL rabbits. Basal coronary flow and bradykinin-induced increase in coronary flow in Langendorff hearts of the pravastatin-treated animals were significantly greater than the flow in the control animals, whereas the metacholine-induced relaxation of abdominal aortic rings was not different and attenuated in comparison to New Zealand white rabbits. The incidence of atherosclerotic lesions in four main coronary arteries and the aorta was significantly lower in the pravastatin treated animals (25.0% and 52.8% respectively[ than in untreated WHHL rabbits (34.1% and 80.0% respectively). The mean percentage of narrowing in the aorta was also significantly lower in the pravastatin-treated group (12.0%) than in the controls (25.2%). Significant correlations were found between the extent of atherosclerotic lesions and the bradykinin-induced increase in coronary flow versus plasma total cholesterol levels. Thus, in this model, long term cholesterol lowering treatment with pravastatin starting at an early age retards the progression of plaque formation and preserves the endothelium-dependent relaxation of the coronary arteries.

粥状動脈硬化の退縮における抗酸化剤の作用

It has been demonstrated by several lines of studies that oxidized LDL plays an important role in early stage of atherogenesis. The antioxidant, probucol, inhibits oxidative modification of LDL and prevents progression of atherosclerosis in WHHL rabbits. Probucol also has been reported to stimulate regression of atheromatous lesions. In this study, we tried to elucidate the mechanism which probucol stimulates regression of atherosclerosis.HDL has been reported to stimulate efflux of cholesterol from foam cells by making direct contact with them in subendothelial space, and this is the very place where oxidative modification of LDL is considered to occur. Therefore, it can be strongly speculated that oxidative modification of HDL occurs in vivo. When HDL was incubated with 5 μM cupric ion, the amount of lipid peroxide increased significantly, and he band of apolipoprotein Al on SDS-PAGE disappeared (Fig. 2). Next, we compared native HDL and oxidized HDL concerning their effect to stimulate efflux of cholesterol from foam cells. The results revealed that oxidized HDL stimulated significantly less amount of cholesterol efflux (Fig. 3). These data suggest that oxidative modification of HDL reduces its antiatherogenic property, and probucol might possibly inhibit oxidative modification of HDL in vivo. Thus, the antioxidative effect of probucol on HDL could be an explanation for stimulating regression of atheromatous plaque.When atheromatous plaques of probucol-treated and non-treated rabbits were compared, the former contained much less number of macrophages. In order to clarify the mechanism of this phenomenon, we prepared mouse peritoneal macrophages pretreated with or without probucol and compared their chemotactic activity using modified Boyden chamber system. As shown in Fig. 4, probucol-treated macrophages showed increased chamotaxis towards LDL compared with control macrophages, and this couldbe an explanation for macrophage-poor-lesions in probucol-treated rabbits. Our current study demonstrated that an antioxidant, probucol, contributed to the regression of atheromatous plaques by at least two different mechanisms.

Inheritability of atherosclerosis and the role of lipoproteins as risk factors in the development of atherosclerosis in WHHL rabbits: Risk factors related to coronary atherosclerosis are different from those related to aortic atherosclerosis

Inheritability of atherosclerosis and the influences of serum lipids on atherosclerosis were examined by following its progression in selectively bred WHHL rabbits. Our studies indicate (1) coronary atherosclerosis is clearly inherited from parents by offspring whereas inheritability of aortic atherosclerosis is uncertain; (2) coronary stenosis is positively correlated to serum cholesterol level, although the correlation coefficient is markedly low: in contrast, no relationship between serum lipid levels and aortic atherosclerosis was observed; (3) cholesterol-rich VLDL showed atherogenicity in aorta, but not in coronary arteries; (4) an unknown lipoprotein detected by 3.6% polyacrylamide gel electrophoresis was related to coronary atherosclerosis, although no relationship between the unknown lipoprotein and aortic atherosclerosis was observed. These findings suggest that there are two types of genetic factors involved in atherosclerosis, one of which is unique to coronary atherosclerosis whereas the other is related to only aortic atherosclerosis.

Development of atherosclerosis in genetically hyperlipidemic rabbits during chronic fish-oil ingestion.

The evidence for a reduction in cardiovascular mortality from fish oil is based on epidemiologic observations. To test whether fish-oil supplementation influences the development of atherosclerosis, we treated Watanabe heritable hyperlipidemic rabbits (WHHL), an inbred strain that spontaneously develops atherosclerosis, with 2.5 ml of MaxEPA fish-oil concentrate daily and compared them to a control group fed unsupplemented rabbit chow. Serial cholesterol and triglyceride levels were monitored as were plasma lipid hydroperoxides. The animals were given fish oil from the time of weaning until 1 year of age, when they were sacrificed and their aortas were compared for the extent of atherosclerosis. No significant differences in the cholesterol or triglyceride levels were noted between the two groups. Fatty acid hydroperoxide levels were also similar and were noted to increase from weaning (1.0 +/- 0.7 microM) to the time of sacrifice (1.8 +/- 1.5 microM, p less than 0.01). Fish oil had no influence on the extent of aortic atherosclerosis (25% +/- 14% surface area for controls vs. 28% +/- 19% for treated, p = NS), plaque thickness, or plaque volume after 1 year. We conclude that fish oil does not reduce the levels of serum cholesterol, lipid hydroperoxides, or aortic atherosclerosis in WHHL rabbits. The hypothesis that fish oil protects against atherosclerosis was not supported by this study.

Partial ileal bypass inhibits atherosclerosis in WHHL rabbits

The effectiveness of partial ileal bypass (PIB) as a counter-measure against atherosclerosis was evaluated in WHHL rabbits. The effects of PIB and sham operation, each performed in five animals, on serum lipids, lipoproteins and plaque formation were investigated. PIB resulted in an immediate and sustained decrease of 52% (range 29–67%) in serum cholesterol, while sham operation had no effect. The main reduction was in LDL cholesterol; VLDL-cholesterol was lowered to a lesser extent. PIB also appeared to change the electrophoretic behaviour of total serum, very low density and low density lipoproteins. Plaque formation, measured 30 weeks after operation in various aortic segments and arteries, was significantly reduced after PIB. It is concluded that an induced lowering of serum cholesterol can prevent atherosclerosis in WHHL rabbits. Also, these animals must be considered as a model for the receptor-defective cellular phenotype of homozygous familial hypercholesterolemia, not for the receptor-negative type, which is the only truly genetically homozygous form.

The effect of oxygen on the development of atherosclerosis in WHHL rabbits

The effect of hyperoxic or hypoxic inhalation on blood lipid levels and on the development of atherosclerosis was studied in young male WHHL rabbits. They were exposed to ordinary room air containing different concentrations of oxygen: 6 animals were exposed to 40% oxygen (hyperoxia group) or 5–10% oxygen (hypoxia group) for 5 h a day, 5 days a week for 8 weeks. Four control rabbits inhaled ordinary room air. The following results were obtained. 1. (1) The severity of aortic lesions significantly decreased in the hyperoxia group and increased in the hypoxia group, when these two groups were compared. However, both hypoxic and hyperoxic groups did not statistically differ from the control. 2. (2) Plasma cholesterol levels were not changed either by hyperoxic or hypoxic inhalation. 3. (3) Plasma triglyceride levels were elevated only in the hypoxia group, with significant differences from the values in both control and hyperoxia groups. 4. (4) There was no significant correlation between mean plasma lipid level and severity of aortic lesions. From these results, we conclude that hyperoxic or hypoxic inhalation respectively regresses or aggravates the development of atherosclerotic lesions, not by an indirect action on blood lipid concentrations but by a direct action on the vascular wall.