Lesions In Cholesterol-fed Rabbits Research Articles

The effect of per os colchicine administration in combination with fenofibrate and N-acetylcysteine on triglyceride levels and the development of atherosclerotic lesions in cholesterol-fed rabbits.

Atherosclerosis is a chronic inflammatory disease promoted by pro-inflammatory cytokines produced by NOD-, LRR- and pyrin domain-containing protein 3 (NLRP 3) inflammasome. Colchicine is an anti-inflammatory agent that inhibits inflammasome's action and stabilizes atherosclerotic lesions. N-acetylcysteine (NAC) reduces low-density lipoprotein (LDL) oxidation, metalloproteinase levels, and foam cell count and volume. Fenofibrate also has antioxidant, anti-inflammatory, and anticoagulant properties while also having a beneficial effect on the vasomotor function of the endothelium. The purpose of this study is to investigate the effect of per os colchicine administration in combination with fenofibrate and NAC on triglyceride levels and the development of atherosclerotic lesions in cholesterol-fed rabbits. Twenty-eight male, 2 months old New Zealand White rabbits were separated into four groups and were fed with different types of diet for 7 weeks: standard, cholesterol 1% w/w, cholesterol 1% w/w plus colchicine 2 mg/kg body weight plus 250 mg/kg body weight/day fenofibrate, and cholesterol 1% w/w plus colchicine 2 mg/kg body weight plus 15 mg/kg body weight/day NAC. Blood samples were drawn from all animals. Lipid profiles were assessed, and interleukin 6 (IL-6) measurements were performed using an enzyme-linked immunosorbent assay (ELISA) kit. Histologic examination was performed on aorta specimens stained with eosin and hematoxylin. Aortic intimal thickness was evaluated using image analysis. Colchicine administration in combination with fenofibrate or NAC statistically significantly reduced the extent of atherosclerotic lesions in aortic preparations. Co-administration of colchicine with NAC has a stronger anti-atherogenic effect than the colchicine plus fenofibrate regimen. Triglerycide levels were decreased in the colchicine plus fenofibrate group and the colchicine plus NAC group at the end of the experiment (p < 0.05), whereas the Cholesterol group had increased levels. A favorable significant lower concentration of IL-6 was detected in the colchicine plus NAC group vs. the other groups. In an experimental rabbit model, it appears that colchicine statistically significantly reduces the development of atherosclerosis of the aorta, especially in combination with NAC. Colchicine, as an NLRP3 inflammasome inhibitor, and NAC, as an agent that directly targets IL-6 signaling, can reduce the inflammatory risk. Fenofibrate enhances the attenuating role of colchicine on triglyceride levels. Clinical studies should investigate whether similar effects can be observed in humans.

Cholesteryl ester transfer protein: ace of spades, queen of hearts, or the joker?

Cholesteryl ester transfer protein: ace of spades, queen of hearts, or the joker?

Abstract 360: Reduction of Atherosclerotic Lesions by the Chemotherapeutic Agent Carmustine Associated to a Lipid Nanoemulsion

After injection in bloodstream, a lipid nanoemulsion (LDE) resembling low-density lipoprotein (LDL) concentrate in atherosclerotic lesions of cholesterol-fed rabbits. Here, rabbits with atherosclerosis were treated with carmustine, an antiproliferative agent used in cancer chemotherapy, associated to LDE to investigate the effects on the lesions. Eighteen male New Zealand rabbits were fed a 1% cholesterol diet for 8 weeks. After 4 weeks nine animals were treated intravenous saline solution and nine with intravenous LDE-carmustine (4 mg/kg, weekly for 4 weeks). LDE-carmustine inhibited atherosclerotic lesions by 90%, compared to controls. LDE-carmustine reduced presence of macrophages, smooth muscle cells, and regulatory T-cells in the arterial intima as well as the expression of matrix metallopeptidase-9, interleukin-1β and TNF-α and lipoprotein receptors (LDL receptor, LDL-related protein-1 and scavenger receptor class B member 1). In conclusion, LDE-carmustine treatment resulted in marked reduction of lesion area, invasion by macrophages and intimal smooth muscle cells and pro-inflammatory factors. Therefore, this new formulation shows great potential for therapy of atherosclerotic cardiovascular disease.

The antiatherogenic effect of bixin in hypercholesterolemic rabbits is associated to the improvement of lipid profile and to its antioxidant and anti-inflammatory effects.

Hypercholesterolemia and oxidative stress have been implicated in the pathophysiology of atherosclerosis and coronary artery disease. We investigated whether the carotenoid bixin (BIX) may reduce oxidative damage, inflammatory response, and the atherosclerotic lesion induced by hypercholesterolemia in rabbits. Rabbits received regular chow (control) or a hypercholesterolemic diet (0.5% cholesterol) alone or supplemented with BIX (10, 30 or 100 mg/kg body weight, b.w.) or simvastatin (15 mg/kg b.w.) for 60 days. Treatment with BIX or simvastatin reduced the atherosclerotic lesions in cholesterol-fed rabbits (up to 55 and 96% reduction, respectively). This protective effect of BIX was accompanied by decrease in the levels of tumor necrosis factor alpha by 15%, interleukin 6 by 19%, lipid peroxidation by 60%, non-high-density lipoprotein cholesterol (non-HDL-C) by 37%, and triglycerides by 41%. BIX increased by 160% the HDL-C levels and decreased by 67% the atherogenic index of hypercholesterolemic rabbits. In atherosclerotic rabbits, the non-protein thiol groups content and the activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione reductase, and thioredoxin reductase were increased in the aortic tissue, whereas paraoxonase activity was reduced in the serum. All these changes were completely prevented by BIX or simvastatin treatment. These results demonstrate that BIX reduces the extent of atherosclerotic lesions and this effect was associated with the decrease in oxidative stress, inflammatory response, and improvement of dyslipidemia, which were most effectively controlled after treatment with 10-30 mg BIX/kg b.w. BIX consumption may, therefore, be an adjuvant to prevent atherosclerosis reducing risk factors for coronary diseases.

Influence of Zerumbone Supplementation a Natural Dietary Product from on Early-Developed Atherosclerotic Lesions in Cholesterol-Fed Rabbits

Influence of Zerumbone Supplementation a Natural Dietary Product from on Early-Developed Atherosclerotic Lesions in Cholesterol-Fed Rabbits

Influence of Zerumbone Supplementation a Natural Dietary Product from Zingiber zerumbet smith on Early-Developed Atherosclerotic Lesions in Cholesterol-Fed Rabbits

Atherosclerosis is a condition of the arterial wall to 'injury', which is prominently driven by inflammatory and proliferative responses. The objective of this investigation is to evaluate the impact of Zerumbone (ZER), a natural cyclic sesquiterpene isolated from Zingiber zerumbet Smith against early-developed atherosclerotic lesion in the aorta of New Zealand white rabbits fed a cholesterol-rich diet. Forty two male rabbits used in the present study were randomly assigned into seven experimental groups as follows: EG-I (CN) considered as control group was fed a standard rabbit pellet diet, EG-II (CP) given a cholesterol-rich diet (1%), EG- III (Z+CP) given ZER (0.4%) two weeks before day 0 as preventive measure and thereafter with the course of cholesterol- rich diet, EG-IV (Z1+CP) given ZER (0.8%), EG-V (Z2+CP) given ZER (1%), EG-VI (S+CP) given Simvastatin (SIM) (20 mg/Kg) and EG-VII (S+Z+CP) given ZER (0.8%) together with SIM (20mg/Kg). Experimental groups from EG-IV to VII believed to represent the therapeutic measure of ZER against early-developed atherosclerosis. Tissue samples were collected from the thoracic aorta and aortic arch at 12 weeks post-feeding for gross, histopathological and ultrastructural (scanning electron microscopy) examination. Morphological analysis (both microscopic and ultrastratural) revealed that endothelial damage and atheromas plague built up were notably diminished in ZER treated groups in a dose dependent manner where it is more prominent in EG-III and EG-VII compared to EGs-VI, V, and VI. However, most of the ZER treated groups showed obvious reduction in plague development in contrast to cholesterol-rich diet group EG-II. Our data indicate that dietary intake of ZER considerably averts and decreases early plague formation and development via significant lessening in smooth muscle cells proliferation and reduction of inflammatory progression.

Synthetic dimyristoylphosphatidylcholine liposomes assimilating into high-density lipoprotein promote regression of atherosclerotic lesions in cholesterol-fed rabbits

We have reported recently that enrichment of high-density lipoprotein (HDL) with phosphatidylcholine (PC) liposomes is effective in solubilizing cholesterol from isolated human atherosclerotic plaques. In the present study, we investigated the in vivo effect of enrichment of HDL with PC on regression of diet-induced atherosclerosis in rabbits. As part of the study, a preliminary in vitro study on blood collected from the cholesterol-fed rabbits was performed to assess the capacity of the HDL density (d > 1.063 g/mL) plasma fraction from cholesterol-fed rabbits to assimilate multilamellar liposomes of synthetic dimyristoylphosphatidylcholine (DMPC). This was compared with the capacities of egg- and soy-PC liposomes to be assimilated into the HDL density plasma fraction. The capacity of the HDL density fraction to absorb PC from DMPC liposomes (11.5 mg/mL) was more than 10 times greater than egg or soy liposomes. Therefore, DMPC liposomes were chosen to infuse into cholesterol-fed rabbits. Cholesterol-fed rabbits infused weekly with DMPC liposomes (300 mg/kg body weight) for five weeks had significantly decreased aortic cholesterol contents (P < 0.05) compared with saline-infused cholesterol-fed controls. Atherosclerotic plaque volume, as measured by a type of new magnetic resonance imaging analysis, also decreased significantly (P < 0.05) after DMPC treatment. The present findings suggest that the enrichment of HDL with PC via intravenous infusion of synthetic DMPC liposomes could be a potential therapeutic approach for atherosclerotic plaque regression.

Promotion of atherogenesis by copper or iron—Which is more likely?

Iron levels increase in atherosclerotic lesions in cholesterol fed-rabbits and play a role in atherosclerosis. We investigated whether copper also rises. Male New Zealand White rabbits were fed high-cholesterol diets for 8 weeks. After sacrifice, lesion sizes were determined, and elemental analyses of the lesion and unaffected artery wall performed using nuclear microscopy. Unlike iron, lesion copper is decreased by about half compared with the unaffected artery wall, and much less copper than iron is present. Our data suggest that iron may be more likely to play a role in the promotion of atherosclerosis than copper.

Effect of dietary copper supplementation on cell composition and apoptosis in atherosclerotic lesions of cholesterol-fed rabbits

We have previously shown that dietary copper supplementation modulates the formation of atherosclerotic lesions in the cholesterol-fed rabbit. In the present study, we have investigated the effects of copper supplementation on the cellular composition and characteristics of atherosclerotic lesions in cholesterol-fed NZW rabbits. Rabbits received a 1% cholesterol diet with or without 0.02% copper acetate (containing 12 and 0.3 mg copper per 100 g diet, respectively) for 12 weeks. The tunica intima was significantly smaller in the animals receiving copper supplements (0.016±0.005 vs. 0.068±0.019 mm 2, P<0.05) and this was accompanied by a significant increase in aortic copper content (4.0±0.8 vs. 1.8±0.2 μg/g tissue, P<0.05). The percentage area staining for smooth muscle cells (HHF-35 positive) was significantly lower in the intima of animals receiving copper supplements (7.13±1.02 vs. 9.72±0.82%, P<0.05). However, there were no significant differences in area staining for macrophages (RAM-11 positive) between groups (22.6±7.9 vs. 23.3±4.9%). There were also significantly fewer apoptotic cells (0.96±0.33 vs. 2.54±0.56%, P<0.005) in the aortic intima from animals supplemented with copper, but no difference in the number of proliferating cells. However, there was a reduction in intimal collagen staining (Sirius red positivity) in the animals receiving a copper supplement. Taken together, these data show that dietary copper can significantly affect the composition and progression of atherosclerotic lesions.

Effects of feeding various tocotrienol sources on plasma lipids and aortic atherosclerotic lesions in cholesterol-fed rabbits

Tocotrienols exert hypocholesterolaemic and antioxidant effects, and may hence have anti-atherogenic properties. Therefore, the aim of this study was to investigate the cholesterol-lowering and anti-atherogenic effects of tocotrienols in cholesterol-fed rabbits. Rabbits were fed a basal diet (control) supplemented with γ-tocotrienol, γ-tocotrienyl acetate, mixed tocotrienols or α-tocotrienol for 12 weeks. All treatments resulted in significant increases in plasma tocotrienols. None of the treatments, however, had significant effects on serum lipids or size of atherosclerotic lesions. A trend towards a decrease in plasma cholesterol was observed following γ-tocotrienol treatment (−22%) after 6 weeks. The decrease was mainly attributable to a reduction in LDL cholesterol (23%), whereas HDL cholesterol increased (14%). This trend was mirrored in a non-significant reduction in lesion area (20%). Our results demonstrate that tocotrienols are absorbed, but have little effect on plasma lipids and atherosclerosis in cholesterol-fed rabbits.

On the anti-atherogenic effect of the antioxidant BHT in cholesterol-fed rabbits: inverse relation between serum triglycerides and atheromatous lesions

We have shown that inclusion of the antioxidant butylated hydroxytoluene (BHT) in the diet protects against development of atherosclerotic lesions in cholesterol-fed rabbits. In parallel, BHT treatment results in increased plasma triglyceride levels. The present study explores the relationship between the triglyceride-inducing and protective effects of BHT in two different studies. The combined material contains 22 rabbits fed cholesterol and 18 rabbits fed cholesterol in combination with 1% BHT. In the BHT group there was an inverse relationship between triglyceride exposure/cholesterol exposure and extent of lesions with r=0.74 ( P=0.0005). Our results show that increased triglyceride exposure parallels the anti-atherogenic effect of BHT. There was no significant correlation between atheromatosis and serum BHT levels. β-Very low density lipoprotein (β-VLDL) from cholesterol and BHT animals was triglyceride-enriched and smaller compared to β-VLDL from cholesterol-fed animals, but there was no significant association between the anti-atherogenic effect of BHT and particle size or apolipoprotein pattern of LDL or β-VLDL. LDL isolated from rabbits treated with cholesterol and BHT was less sensitive to oxidative modification than LDL isolated from rabbits treated with cholesterol only. In conclusion, our results demonstrate that the degree of triglyceride exposure may be an important modulator of the anti-atherogenic effect of an antioxidant.

Suppressive effect of simvastatin on intramural small coronary arterial lesions in cholesterol-fed rabbits.

The aim of this study was to examine the suppressive effect of simvastatin on intramural coronary arterial lesions in cholesterol-fed rabbits. In one experiment, six groups of rabbits were fed laboratory chow alone or with added 0.1%, 0.2%, 0.3%, 0.5% or 1.0% cholesterol for 16 weeks. In another experiment, four groups of rabbits were fed a 0.5% cholesterol diet and treated with simvastatin at 1, 3, or 5 mg/kg/day or placebo. In each rabbit, the levels of serum total cholesterol (TC) were determined at 1-week intervals to calculate the integrated values. The lesion induction ratio was defined as the ratio of intramural coronary arteries 50-150 microm in diameter with arterial lipoidosis to the total number of arteries of the same diameter. In the two experiments, there were positive correlations between the lesion induction ratio and integrated TC (r=0.785, P<0.0001 and r=0.763, P<0.0001, respectively). The slopes of the regression lines for integrated TC obtained in the two experiments were similar, but the lesion induction ratio in the simvastatin-treated group was always lower, by about 14%, in comparison with that in the non-simvastatin-treated group. These findings suggest that simvastatin induces lesion reduction not only by reducing the levels of circulating cholesterol but also by directly suppressing the development of lipoidosis.

The antiatherogenic effect of nifedipine on intramural small coronary arterial lesions in cholesterol-fed rabbits.

The objective of this study was to examine the suppressive effect of nifedipine on intramural coronary arterial lesions in cholesterol-fed rabbits. Each rabbit in Groups A (n=6) and B (n=5) was fed a 0.3% cholesterol diet and was orally administered nifedipine (40 mg/day) or placebo. Each rabbit in Groups C (n=5) and D (n=6) was fed a 0.5% cholesterol diet and was orally administered nifedipine (40 mg/day) or placebo. The serum concentrations of total cholesterol (TC) were determined at 1-week intervals to calculate the integrated values. The lesion induction ratio was defined as the ratio of intramural coronary arteries 50-150 microm in diameter with arterial lipoidosis to the total number of arteries of the same diameter. There were no significant differences between the nifedipine-treated and placebo groups in either the integrated TC or lesion induction ratio in either the 0.3% and 0.5% cholesterol-fed rabbits. This study demonstrates that nifedipine does not suppress atherogenesis in the intramural small coronary arteries of cholesterol-fed rabbits.

Macroscopic distribution of coronary atherosclerotic lesions in cholesterol-fed rabbits.

In the present study we macroscopically examined a change in the distribution of coronary atherosclerosis in cholesterol-fed rabbits. Rabbits were fed a cholesterol-enriched diet for 15 weeks, then replaced by a normal diet, and were sacrificed at 15, 24, 32 and 42 weeks after the start of the experiment. The coronary atherosclerosis in the cholesterol-fed rabbits was distributed more densely in the proximal portion than in the middle and distal portions, and the lesions were severe at 24 and 32 weeks after the start of the experiment. comparison of lesions in the three portions at these time points showed that the percentages of lesion areas in the proximal portion, the middle portion and the distal portion were approximately 51%, 21 to 25% and 0.2 to 3.7%, respectively. Macroscopic observation of the coronary atherosclerotic lesions showed that the lesions formed over the vessel lumen in the proximal portion within the range of approximately 5 mm from the orifice of the left coronary artery. In the middle portion, the lesions formed predominantly around the orifices of branches as small patchy lesions from 1 to 3 mm in diameter. These findings support previous histopathological reports that suggested that the incidence of stenosis in the proximal portion was high, and the incidence of lesion occurrence in the middle and the distal portions varied. The method, macroscopical investigation of the coronary artery, is useful for analyzing coronary atherosclerosis in the rabbit.

T helper cell infiltration and foam cell proliferation are early events in the development of atherosclerosis in cholesterol-fed rabbits.

The involvement of T cells in the early cellular events in atherosclerosis was studied in rabbits fed a 1% cholesterol diet by use of specific monoclonal anti-rabbit CD5 and CD4 antibodies. T cells were not seen in the aortic intimas of rabbits not fed cholesterol but were seen in intimal lesions in cholesterol-fed rabbits. Accumulation of T cells in plaques occurred between 2 and 4 weeks after commencement of cholesterol feeding, and the greatest density of CD5-positive T cells were observed after 4 weeks (11.2 +/- 6.0 cells/mm2 [mean +/- SEM]; P < .02 compared with normal control rabbits, P < .03 compared with 2-week plaques). Staining for CD4 indicated that the majority of these T cells were T helper cells (9.9 +/- 4.9 cells/mm2). At this time, plaques showed a dense cellular infiltrate of macrophages (3623 +/- 467 cells/mm2) and macrophage proliferation was evident (2.1 +/- 1.1% of total plaque cells). As the cross-sectional area of intimal lesions increased progressively in subsequent weeks, their cellularity declined (8 weeks, 2239 +/- 271 cells/mm2; 12 weeks, 1535 +/- 55 cells/mm2; 16 weeks, 1747 +/- 242 cells/mm2, P < .05 for all groups compared with the 4-week group). The density of the T cell infiltrate (8 weeks, 6.7 +/- 3.0 cells/mm2; 12 weeks, 0.6 +/- 0.2 cells/mm2; 16 weeks, 1.0 +/- 0.4 cells/mm2) and the proliferative index of cells within plaques (8 weeks, 0.6 +/- 0.2%; 12 weeks, 0.8 +/- 0.3%; 16 weeks, 0.2 +/- 0.2%) also declined.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced development of atherosclerosis in cholesterol-fed rabbits by suppression of cell-mediated immunity.

T lymphocytes are present in atherosclerotic lesions, but the role of this cell type in the disease process has not been determined. To determine whether cell-mediated immunity influences atherogenesis, New Zealand White rabbits fed a cholesterol-supplemented diet (0.5% wt/wt) were treated with cyclosporin A (n = 20) or vehicle alone (n = 16) for 12 wk. The dose of cyclosporin A was adjusted so that a blood concentration between 100 and 200 ng/ml was maintained to achieve a selective action T-lymphocytes. Effectiveness of immunosuppression in cyclosporin A-treated rabbits was confirmed by allogeneic skin graft survival. Cyclosporin A administration did not affect total plasma lipid concentrations, body weight, or renal function. Percentage of aortic intimal area covered with atherosclerotic lesions was increased significantly by immunosuppression in both the arch region (75 +/- 3% [mean +/- SEM] compared with 60 +/- 5% in controls; P < 0.01) and the thoracic region (47 +/- 7% vs 27 +/- 6%; P = 0.04). Enhanced atherogenesis was not associated with diminished numbers of T lymphocytes in lesions, changes in T lymphocyte subtype, or any discernible change in cellular composition. Humoral immune responses to oxidized LDL were similar in the two groups: serum titres of autoantibodies against malondialdehyde-modified LDL were equivalent. These data demonstrate that cyclosporin A-induced suppression of cell-mediated immunity increased the development of macrophage-rich atherosclerotic lesions in cholesterol-fed rabbits.

A new probability mapping method to describe the development of atherosclerotic lesions in cholesterol-fed rabbits

A new probability mapping method was developed to quantify the size and location of lesions near aortic orifices. The precise location of any part of the lesion could be compared between rabbits. Colour photographs of lesions were projected onto a digitizing tablet, and coded as lesion or non-lesion. Next the orifices were warped onto a standard orifice, and then the lesion mapped to maintain the original length and angular location of the lesion from the edge of the orifice. This method, unlike the previously used polar mapping method, excludes neither absent lesions nor ones which surround more than one orifice. In contrast to other probability mapping methods it warps the orifice rather than the artery wall containing the lesion, and so is easier to use for correlation with histological studies. The eventual aim is to use the probability maps as a tool to estimate the age of various positions of the lesion and to identify areas for histological sampling. The method was used to describe the distribution of lesions in 21 rabbits fed a diet with cholesterol levels declining from 0.5% during the first week, to 0.25% during the next two weeks, to 0.125% for weeks 3–10, to 0.1% for weeks 11–24. This feeding protocol produces fatty lesions which are transformed into fibro-fatty and fibrous lesions with time.

The relationship between pre-existing subendothelial smooth muscle cell accumulations and foam cell lesions in cholesterol-fed rabbits.

We investigated whether pre-existing subendothelial smooth muscle cell (SMC) accumulations in cholesterol-fed rabbits are transformed into foam cell plaques. Twenty-four rabbits received a standard diet supplemented with 2% cholesterol for 4 or 8 weeks. Six rabbits received a supplement of 0.3% cholesterol for 35 weeks. The aorta and other systemic and pulmonary vessels were studied by immunohistochemistry for smooth muscle cells SMC (alpha-SMC actin), macrophages (RAM11), cell replication (proliferating cell nuclear antigen) and endothelial cells (von Willebrand factor; vWF). Initially the foam cell plaques were composed exclusively of foam cells of macrophage origin (MFC). In more advanced lesions SMC and collagen fibres were also present, leading to a fibrous transformation of the plaque. Cell replication was mainly located in the MFC. The endothelial cells covering the plaques showed an increased immunoreactivity for vWF which was also deposited in the interstitium between the FC. Pre-existing subendothelial SMC did not transform into FC. The newly formed FC plaques remained clearly separated from the pre-existing subendothelial SMC. The development of the plaques can be attributed not only to monocyte recruitment but also to macrophage multiplication.

The effect of concurrent administration of isradipine on the development of fatty streaks in the cholesterol-fed rabbit: a morphometric study

Calcium antagonists attenuate the development of aortic lesions in cholesterol-fed rabbits. This study was undertaken to examine the influence of isradipine (dose: 0.3 mg/kg per day orally) on the histological components of these lesions in New Zealand White rabbits (age: 12 weeks, weight: 2–2.5 kg). Five groups of animals were fed standard chow with the following supplements for 3 weeks: Group 1, no supplements; Group 2, 40 g cholesterol; Group 3, 60 g cholesterol; Group 4, 40 g cholesterol + isradipine; Group 5, 60 g cholesterol + isradipine. After 3 weeks, the animals were killed and the aorta prepared for morphometry. The volume of intima/cm aorta was estimated and the volume fraction ( V V) of the intima occupied by components of the lesions was estimated by point counting. By integrating these two measurements the volume/unit length (mm 3/cm) of the following components of the aorta were estimated: intima, noncellular components, endothelial cells, myointimal cells, lipid accumulating myointimal cells and foam cells. Cholesterol feeding for 3 weeks was associated with significant increases in the volume of non-cellular components of the intima, endothelial cells, myointimal cells, lipid accumulating myointimal cells and foam cells. Administration of isradipine significantly reduced all these parameters. It is concluded that isradipine attenuates cellular hyperplasia and accumulation of non-cellular components of lesions in cholesterol fed rabbits.

Increased levels of monohydroxy metabolites of arachidonic acid and linoleic acid in LDL and aorta from atherosclerotic rabbits

Lipid peroxidation results in the formation of peroxy and hydroperoxy metabolites of polyunsaturated fatty acids which can directly or indirectly affect many cellular processes. Lipid hydroperoxides are rapidly metabolized to the corresponding monohydroxy products by various cellular peroxidases. We have measured the amounts of monohydroxy metabolites of linoleic acid (18:2) and arachidonic acid (20:4) in lipids derived from aorta and LDL from rabbits fed a diet enriched in cholesterol and peanut oil for either 8 or 15 weeks. Increased amounts of the 9-hydroxy, and, to a lesser extent, the 13-hydroxy metabolite of 18:2 were observed in aorta and LDL from cholesterol-fed rabbits at both 8 and 15 weeks. The amounts of esterified 11-, 12- and 15-hydroxy metabolites of 20:4 in aortae from cholesterol-fed rabbits were similar to controls after 8 weeks, but about 3-fold higher after 15 weeks. These monohydroxy metabolites of 20:4 were also detected in LDL lipids in cholesterol-fed rabbits. The greater amounts of hydroxy-18:2 in the cholesterol-fed group could be explained by an approx. 2-4-fold increase in 18:2 in aorta and LDL. In contrast, the amounts of 20:4 in aortic lipids were lower in cholesterol-fed rabbits than in controls. Thus, the percentage of esterified 20:4 which had been oxidized to its 11, 12, and 15-hydroxylated metabolites was about 5-times higher in the cholesterol-fed group. Our results would be consistent with the hypothesis that increased amounts of peroxidized 18:2 and 20:4 in lipids could be involved in the development of atherosclerotic lesions in cholesterol-fed rabbits.