elastin and Hypercholesterolemia

Understanding variations in size and pattern of development of angiotensin II (Ang II)-induced abdominal aortic aneurysms (AAA) may inform translational research strategies. Thus, we sought insight into the temporal evolution of AAA in apolipoprotein (apo)E(-/-) mice.. A cohort of mice underwent a 4-week pump-mediated infusion of saline (n = 23) or 1500 ng/kg/min of Ang II (n = 85) and AAA development was tracked via in vivo ultrasound imaging. We adjusted for hemodynamic covariates in the regression models for AAA occurrence in relation to time.. The overall effect of time was statistically significant (p<0.001). Compared to day 7 of AngII infusion, there was no decrease in the log odds of AAA occurrence by day 14 (-0.234, p = 0.65), but compared to day 21 and 28, the log odds decreased by 9.07 (p<0.001) and 2.35 (p = 0.04), respectively. Hemodynamic parameters were not predictive of change in aortic diameter (Δ) (SBP, p = 0.66; DBP, p = 0.66). Mean total cholesterol (TC) was higher among mice with large versus small AAA (601 vs. 422 mg/ml, p<0.0001), and the difference was due to LDL. AngII exposure was associated with 0.43 mm (95% CI, 0.27 to 0.61, p<0.0001) increase in aortic diameter; and a 100 mg/dl increase in mean final cholesterol level was associated with a 12% (95% CI, 5.68 to 18.23, p<0.0001) increase in aortic diameter. Baseline cholesterol was not associated with change in aortic diameter (p = 0.86).. These are the first formal estimates of a consistent pattern of Ang II-induced AAA development. The odds of AAA occurrence diminish after the second week of Ang II infusion, and TC is independently associated with AAA size.

Topics: Angiotensin II; Animals; Aortic Aneurysm, Abdominal; Apolipoproteins E; Atherosclerosis; Cholesterol; Elastin; Hypercholesterolemia; Macrophages; Male; Matrix Metalloproteinase 2; Mice; Mice, Inbred C57BL; Muscle, Smooth, Vascular; Time Factors; Ultrasonography

Unique innate immunity-linked γδT cells have been seen in early human artery lesions, but their role in lesion development has received little attention. Here we investigated whether γδT cells modulate atherogenesis in apolipoprotein E-deficient (ApoE KO) mice. We found that γδT cell numbers were markedly increased in the proximal aorta of ApoE-deficient vs. wild-type mice during early atherogenesis, particularly in the aortic root and arch, where they comprised most of the T cells and lesion progression is most rapid. γδT cells infiltrated intimal lesions in ApoE KO mice, but only the adventitia in wild-type mice, and were more prevalent than CD4+ T cells in early nascent lesions, as evaluated by en face confocal microscopy. These aortic γδT cells produced IL-17, but not IFN-γ, analyzed by ex vivo FACS. Furthermore, aortic arch lipid accumulation correlated strongly with abundance of IL-17-expressing splenic γδT cells in individual ApoE KO mice. To investigate the role of these γδT cells in early atherogenesis, we analyzed ApoE/γδT double knockout (DKO) compared to ApoE KO mice. We observed reduced early intimal lipid accumulation at sites of nascent lesion formation, both in chow-fed (by 40%) and Western diet-fed (by 44%) ApoE/γδT DKO mice. In addition, circulating neutrophils were drastically reduced in these DKO mice on Western diet, while expansion of inflammatory monocytes and splenic Th1 or Th17 lymphocytes was not affected. These data reveal, for the first time, a pathogenic role of γδT cells in early atherogenesis in ApoE KO mice, by mechanisms likely to involve their IL-17 production and induction of neutrophilia. Targeting γδT cells thus might offer therapeutic benefit in atherosclerosis or other inflammatory vascular diseases.

Topics: Animals; Antigens, CD; Antigens, Differentiation, Myelomonocytic; Aorta; Aorta, Thoracic; Apolipoproteins E; Atherosclerosis; Diet, High-Fat; Disease Models, Animal; Disease Progression; Elastin; Hypercholesterolemia; Interleukin-17; Leukocyte Disorders; Lipids; Male; Mice; Mice, Knockout; Receptors, Antigen, T-Cell, gamma-delta; Spleen; T-Lymphocytes; Th17 Cells

Bipolar energy ligation of vessels in surgery is common. Although rare, serious failures occur. Atherosclerosis may contribute to seal failures by altering vascular compressibility and collagen content; however, no data exist.. Femoral and iliac arteries of six Yucatan swine with an identified genetic locus predisposing them to atherosclerosis were denuded with a Fogarty catheter. Animals were fed a high-fat diet for 28 wk. A Yorkshire pig was used as a normal control and fed a standard diet. At 28 wk, arteries were measured for their diameters, sealed, and divided in vivo with LigaSure. The sealed artery sections were excised and subjected to burst pressure testing. Half of the seal distal to the aorta was kept intact for histology and collagen and elastin quantification. A multiple linear regression model was used to assess variables contributing to burst pressure. Covariates included were vessel diameter, degree of atherosclerosis, and collagen content.. Experimental animals were hypercholesterolemic. Atherosclerosis occurred in 90% of seals in induced animals, with severe atherosclerosis in 62% of seals. There was site-selective deposition of atherosclerotic plaques in larger diameter iliac vessels. A model including collagen and size best predicted burst pressure. Every 10-U increase in collagen resulted in 15% increase in burst pressure (95% confidence interval = 0.2%-32%, P = 0.047, R(2) = 0.36). Atherosclerosis was unrelated to burst pressure controlling for collagen and size.. Collagen and size provide the best model fit for predicting burst pressure. Quantitative research in human vasculature is warranted to better understand the influence of atherosclerosis and collagen content on seal failures.

Topics: Animals; Atherosclerosis; Balloon Embolectomy; Collagen; Disease Models, Animal; Elastin; Female; Femoral Artery; Hemostatic Techniques; Hypercholesterolemia; Iliac Artery; Plaque, Atherosclerotic; Swine; Swine, Miniature; Vascular Surgical Procedures

To determine if treatment with hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) can influence the development of experimental abdominal aortic aneurysms (AAAs).. AAAs are associated with atherosclerosis, chronic inflammation, and matrix metalloproteinase (MMP)-mediated connective tissue destruction. Because statins exert antiinflammatory activities independent of their lipid-lowering effects, these agents may help suppress aneurysmal degeneration.. C57Bl/6 wild-type and hypercholesterolemic apoE-deficient mice underwent transient perfusion of the aorta with elastase followed by subcutaneous treatment with either 2 mg/kg simvastatin per day or vehicle. Aortic diameter (AD) was measured before and 14 days after elastase perfusion. The extent of aortic dilatation (DeltaAD) was determined with AAAs defined as DeltaAD >100%.. Wild-type mice treated with simvastatin exhibited a 21% reduction in DeltaAD and a 33% reduction in AAAs compared with vehicle-treated controls. Suppression of AAAs in simvastatin-treated mice was associated with preservation of medial elastin and vascular smooth muscle cells, as well as a relative reduction in aortic wall expression of MMP-9 and a relative increase in expression of TIMP-1. In hypercholesterolemic apoE-deficient mice, treatment with simvastatin was associated with a 26% reduction in DeltaAD and a 30% reduction in AAAs. Treatment with simvastatin had no effect on serum cholesterol levels in either normal or hypercholesterolemic mice.. Treatment with simvastatin suppresses the development of experimental AAAs in both normal and hypercholesterolemic mice. The mechanisms of this effect are independent of lipid-lowering and include preservation of medial elastin and smooth muscle cells, as well as altered aortic wall expression of MMPs and their inhibitors.

Topics: Animals; Aortic Aneurysm, Abdominal; Elastin; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypercholesterolemia; Male; Matrix Metalloproteinases; Mice; Mice, Inbred C57BL; Models, Animal; Myocytes, Smooth Muscle; Simvastatin; Tissue Inhibitor of Metalloproteinases; Tunica Media

It has been suggested that aortic valve sclerosis (AVS) is an atherosclerotic disease process that can proceed to aortic stenosis. The absence of reports studying an animal model of the early stages of this disease has precluded the development of preventive therapeutic strategies. A cholesterol-fed (0.25% cholesterol in chow) rabbit model of atherosclerosis that is characterized by a moderate level of hypercholesterolemia was studied to determine its efficacy as a model of early AVS. Cellular, structural and morphological changes in the aortic valves of these rabbits were studied.. Twenty rabbits were assigned randomly to four experimental groups: Group 1 received normal chow for 40 weeks; group 2 received 0.25% cholesterol-supplemented chow for 20 weeks; group 3 received 0.25% cholesterol-supplemented chow for 40 weeks; and group 4 received 0.25% cholesterol-supplemented chow for 20 weeks followed by normal chow for an additional 20 weeks. The aortas and aortic valves were analyzed using immunohistochemical and histological methods to detect cellular and structural components of the developing lesions.. All rabbits in groups 2, 3 and 4 developed atherosclerotic lesions in their aortas. Aortic valves from these animals demonstrated thickening, lipid deposition, a change in collagen content and organization, a reorganization of elastin, and the presence of both macrophage infiltrate and osteopontin.. These findings were consistent with the suggestion of a link between atherosclerosis and AVS. Results were also similar to changes reported in human sclerotic aortic valves, suggesting the suitability of this rabbit model of atherosclerosis as a model for AVS.

Topics: Animals; Aorta; Aortic Valve; Arteriosclerosis; Cholesterol, Dietary; Collagen; Diet, Atherogenic; Disease Models, Animal; Elastin; Humans; Hypercholesterolemia; Immunohistochemistry; Lipids; Macrophages; Male; Osteopontin; Phosphoproteins; Rabbits; Random Allocation; Sclerosis; Sialoglycoproteins

Epidemiological and histological evidence implicates proteinases of the matrix metalloproteinase (MMP) family in atherosclerosis and aneurysm formation. We previously indicated a role for urokinase-type plasminogen activator in atherosclerotic media destruction by proteolytic activation of MMPs. However, the role of specific MMPs, such as MMP-9 and MMP-12, in atherosclerosis remains undefined.. MMP-9- or MMP-12-deficient mice were crossed in the atherosclerosis-prone apolipoprotein E-deficient background and fed a cholesterol-rich diet. Mice were killed at 15 or 25 weeks of diet to study intermediate and advanced lesions, respectively. Loss of MMP-9 reduced atherosclerotic burden throughout the aorta and impaired macrophage infiltration and collagen deposition, while MMP-12 deficiency did not affect lesion growth. MMP-9 or MMP-12 deficiency conferred significant protection against transmedial elastin degradation and ectasia in the atherosclerotic media.. This study is the first to provide direct genetic evidence for a significant involvement of MMP-9, but not of MMP-12, in atherosclerotic plaque growth. In addition, deficiency of MMP-9 or MMP-12 protected apolipoprotein E-deficient mice against atherosclerotic media destruction and ectasia, mechanisms that implicate the involvement of these MMPs in aneurysm formation.

Topics: Animals; Aortic Diseases; Apolipoproteins E; Arteriosclerosis; Collagen; Diet, Atherogenic; Dilatation, Pathologic; Elastin; Extracellular Matrix; Female; Hypercholesterolemia; Macrophages; Matrix Metalloproteinase 12; Matrix Metalloproteinase 9; Metalloendopeptidases; Mice; Mice, Inbred C57BL; Tunica Media

Aortic elastin turnover is significantly accelerated in atherosclerosis, partly because of activation of the renin-angiotensin-aldosterone system caused by hypercholesterolaemia. We postulated that angiotensin-converting enzyme inhibitors (ACE-I) prevent the aortic elastin loss in experimental hypercholesterolaemia. Two doses of ACE-I (captopril, enalapril and quinapril) were used: a dose equivalent to that applied to human subjects and a dose 10 times higher. We found that the increase in serum and aortic elastolytic activity in cholesterol-fed rabbits was prevented by high-dose captopril. The elastin content in aorta homogenates from cholesterol-fed rabbits was significantly decreased. The higher dose of captopril, but no other ACE-I, prevented this decrease in aortic elastin content. In cholesterol-fed rabbits the elastin-bound calcium content was significantly elevated. The higher doses of captopril and enalapril lowered the elastin-bound calcium content. In serum and aortic homogenates of cholesterol-fed rabbits, ACE activity was elevated by 15% and 77%, respectively. Both doses of captopril, enalapril and quinapril prevented this cholesterol-induced increase in serum and aortic ACE activity. We conclude that: 1) administration of captopril at doses 10 times higher than those used in humans prevents hypercholesterolaemia increased aortic elastin loss. 2) higher doses of captopril and enalapril prevent the hypercholesterolaemia-induced increase in aortic elastin-bound calcium.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Aorta; Calcium; Captopril; Cholesterol, Dietary; Dose-Response Relationship, Drug; Elastin; Enalapril; Hypercholesterolemia; Isoquinolines; Male; Quinapril; Rabbits; Tetrahydroisoquinolines

This study focuses on the fortuitous discovery of an atypical atherosclerotic lesion in four of 49 male adult cynomolgus monkeys (macacus fascicularis) which were maintained for a long time at a high level of hypercholesterolemia, and in seven of 19 female cynomolgus monkeys examined from the second to the 24th week of hypercholesterolemic diet: this lesion was in formation or already mature during this period of diet. This atypical lesion was formed by a collagen and elastic network surrounding synthetic smooth muscle cells without fibrofatty or fibrous plaques. Lipids were occasionally seen in the inner intima. The lesion appeared early (from the third week of diet). Once established, its morphology did not change. It became more extensive, but was not complicated by lipid overload in spite of prolonged, permanent hypercholesterolemia. This response to hypercholesterolemia is interesting because the activity of the smooth muscle cells differs from that observed in the classic lesion: they intervene earlier, their replication is very marked and rapid, their elastin secretion is greater and remains constant over time, and their phagocytic properties are reduced. This experimental study examines the installation and the maintenance of this lesion and raises the problem of its origin.

Topics: Animals; Aorta, Abdominal; Aorta, Thoracic; Aortic Diseases; Arteriosclerosis; Cell Division; Collagen; Coronary Vessels; Diet, Atherogenic; Elastin; Female; Hypercholesterolemia; Lipids; Macaca fascicularis; Macrophages; Male; Muscle, Smooth, Vascular

To test the hypothesis that atherosclerosis may be initiated by hypoperfusion or thrombotic occlusion of the adventitial vasa vasonum.. In a new model of atherogenesis, an early atherosclerotic lesion may be initiated by removal of the adventitia from the carotid artery of the New Zealand White rabbit, wherein lie the vasa vasorum.. Animal laboratory, University Department of Surgery and Medicine.. Immunocytochemistry was undertaken to demonstrate the presence of smooth muscle cells and macrophages within the intimal lesions. Smooth muscle cells were labelled with a monoclonal antibody designated HHF35 and macrophages were labelled with a rabbit specific, macrophage specific antibody, RAM11. CHIEF RESULTS: In rabbits fed a normal diet, at day 14, the intimal lesion was composed exclusively of smooth muscle cells. By day 28, such lesions had regressed. In rabbits fed a high cholesterol diet, at day 14, the intimal lesion was composed of a mixture of macrophages and smooth muscle cells. By day 42, the pattern of cellular distribution was such that macrophages (present as foam cells) were predominant. In the presence of persistent hypercholesterolaemia these lesions did not regress.. This new model can produce two different cellular responses that may mimic the intimal lesions seen with re-stenosis after angioplasty or in hypercholesterolaemic man and as such, might be useful in separating out these two different pathophysiologies.

Topics: Animals; Arteriosclerosis; Carotid Arteries; Carotid Artery Diseases; Collagen; Elastic Tissue; Elastin; Endothelium, Vascular; Foam Cells; Hypercholesterolemia; Immunohistochemistry; Ischemia; Macrophages; Male; Microscopy, Electron; Muscle, Smooth, Vascular; Rabbits; Thrombosis; Tunica Intima

To elucidate whether tissue fibronectin increases in the early stages of atherogenesis induced by hypercholesterolemia without mechanical trauma, we investigated sequential changes in the distribution of tissue fibronectin during fatty streak initiation and maturation in the aortas of hypercholesterolemic fat-fed rabbits. The presence of fibronectin was examined on immunoperoxidase stained tissue specimens with the aid of a microscope-photometric technique. Twenty male albino rabbits were used. Cholesterol supplemented chow (1%) was given for 4 weeks (n = 6), 8 (n = 5) or 14 weeks (n = 5). A membrane-like layer positive for fibronectin was observed along the endothelium in the normal aorta. After 4 weeks of the cholesterol-feeding, fatty streaks were initiated in the intima, where fibronectin was more densely accumulated than the normal intima. After 8 weeks of the cholesterol-feeding, fatty streaks were expanding, associated with the dense staining for fibronectin. After 14 weeks, fibronectin was still concentrated in the endothelial layer and also in the superficial areas of the thickened intima, but decreased in the deep areas of the thickened intima where collagen and elastin appeared as bundles. The photometric data of fibronectin supported these visual observations. Thus, fibronectin appeared early and disappeared later in the intima during the process of fatty streak initiation and maturation. These findings suggest that in hypercholesterolemia without mechanical endothelial injury, fibronectin may play an important role in an early process of atherogenesis.

Topics: Animals; Aorta; Arteriosclerosis; Collagen; Diet, Atherogenic; Disease Models, Animal; Elastin; Endothelium, Vascular; Fibronectins; Hypercholesterolemia; Immunohistochemistry; Male; Rabbits

These experiments were designed to determine if male New Zealand white rabbits made mildly hypertensive (20-30 mm Hg increase) with bilateral renal artery clips developed more or less sudanophilic lesions than controls, and if the animals responded differently if hypercholesterolemia was produced soon (one week) or late (eight weeks) after the animals were operated on. Both groups received the diet of 2% cholesterol and 6% corn oil for six weeks. We also studied the distensibility of the carotid artery to determine if altered elastic behaviour played a role in lesion development. The experiments showed that the acute hypertensive group developed most lesions (by area), but that the lesions in all groups had the same shape and location. The carotid arteries from the chronic hypertensives were least distensible, and most of the changes appeared to be in the elastance of collagen. The blood pressure actually dropped slightly in the chronic shams after the diet was started. These experiments suggest that, at least, in the rabbit, the duration of the hypertension may determine how the arterial wall responds to hypercholesterolemia. They show that mild hypertension, like hypercholesterolemia, alters the rate at which lesions develop, rather than altering their distribution. The changes do not appear to be related to altered distensibility.

Topics: Analysis of Variance; Animals; Arteriosclerosis; Azo Compounds; Carotid Arteries; Collagen; Elasticity; Elastin; Hypercholesterolemia; Hypertension; Male; Rabbits; Stress, Mechanical

The overall three-dimensional architecture of elastic tissue in early atherosclerotic lesions of the rat aorta was studied using scanning electron microscopy (SEM) after hot-formic acid extraction followed by a freeze-drying method. These lesions were induced by feeding the rats a diet containing 2% cholesterol, 0.5% cholic acid and 0.2% methylthiouracil. SEM revealed two types of alterations in the elastic tissue; one was an increase in the dome-like elastic lamina with few fenestrations that might be due to the reduplication of the internal elastic lamina (IEL), and the other was an increase in fibrous elastin, generally oriented longitudinally in the intima. The former was discussed with respect to its barrier function to such macromolecules as fibrinogen and low density lipoprotein (LDL), and was assumed to be a structure related to prevention of early atherosclerotic lesions.

Topics: Animals; Aorta, Thoracic; Arteriosclerosis; Elastic Tissue; Elastin; Hypercholesterolemia; Male; Microscopy, Electron, Scanning; Rats; Rats, Inbred Strains; Time Factors

The turnover and degradation of mature elastin from the aortae of Japanese quail were estimated following injection with L-[U-14C]lysine by measuring the changes in specific activity of L-[U-14C]lysine and 14C-labelled desmosine and isodesmosine (crosslinking amino acids derived from lysyl residues) in elastin over a 39-week period. Only 5% of the variation in radioactivity could be attributed to changes in time. Therefore, it was concluded that the best estimates of mature elastin turnover are only quantifiable in years. Dietary cholesterol in amounts sufficient to induce plaque formatioin and fragmentation of the elastic lamina in the aorta did not significantly influence turnover time. It would appear that once the total pool of elastin in aorta is stabilized as mature fibers it is not subject to proteolysis or resynthesis of sufficient magnitude to result in measurable turnover.

Topics: Animals; Aorta; Carbon Radioisotopes; Cholesterol, Dietary; Coturnix; Desmosine; Elastin; Female; Hypercholesterolemia; Lysine; Male

Topics: Animals; Aorta, Thoracic; Aortic Diseases; Arteriosclerosis; Collagen; Coronary Disease; Coronary Vessels; Diet, Atherogenic; Disease Models, Animal; Eggs; Elastin; Endothelium; Female; Femoral Artery; Hypercholesterolemia; Iliac Artery; Inclusion Bodies; Male; Marsupialia; Meat; Microscopy, Electron