bluuebunny/crossref_metadata_2025 huggingface dataset:
Allograft-induced arterial wall injury and response in normotensive and spontaneously hypertensive rats.
Authors: Plissonnier D , Levy B I , Salzmann J L , Nochy D , Watelet J , Michel J B
Published: June 2011

The role of genetically determined immune attack and blood pressure in graft rejection-induced arterial wall injury and response was assessed by studying the compliance and changes in wall structure of aortic isografts and allografts in normotensive (Wistar-Kyoto [WKY]) and hypertensive (spontaneously hypertensive [SHR]) rats. Six groups of 8-week-old rats were compared: sham-operated in both strains, isografts, and allografts between the two strains (SHR aortas grafted in WKYs, designated SWs; WKY aortas grafted in SHRs, designated WSs; isografts in SHRs, designated SSs; and isografts in WKYs, designated WWs). Each arterial graft was studied 8 weeks after transplantation for volume and compliance (pressures of 75-175 mm Hg) under basal conditions. The amounts of collagen, elastin, and nuclei in the media and intima of the walls of control and grafted aortas were quantified morphometrically. Isografts and controls had the same mechanical characteristics under basal conditions: the arterial volume and arterial compliance of hypertensive rats were lower than those of normotensive rats (p less than 0.001). Allografts had a greater initial volume (p less than 0.001) and a lower compliance (p less than 0.001) than did isografts. Allografts in SHRs (SSs) were initially dilated, whereas allografted WKYs (WWs) were not. There was intimal proliferation in hypertensive isografts (14 +/- 0.77 microns) and in both types of allografts (WS, 69 +/- 1.55 microns; SW, 44 +/- 1.81 microns); nucleus density was higher in hypertensive allografts (WS) than in normotensive allografts (SW); and collagen density was also higher in SW than in WS allografts. Allografts had decreased medial thickness and decreased smooth muscle cell density.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of corn and coconut oil-containing diets with and without cholesterol on high density lipoprotein apoprotein A-I metabolism and hepatic apoprotein A-I mRNA levels in cebus monkeys.
Authors: Stucchi A F , Hennessy L K , Vespa D B , Weiner E J , Osada J , Ordovas J M , Schaefer E J , Nicolosi R J
Published: June 2011

The mechanism(s) by which diets containing corn or coconut oil (31% of energy as fat) totally free of cholesterol or with 0.1% added cholesterol by weight (0.3 mg/kcal) affect plasma high density lipoprotein cholesterol (HDL-C), apoprotein (apo) A-I levels, apo A-I kinetics, and hepatic apo A-I mRNA concentrations were investigated in 26 cebus monkeys. Coconut oil-fed monkeys had elevated levels of plasma total cholesterol (217%), very low density lipoprotein plus low density lipoprotein cholesterol (331%), HDL-C (159%), and apo A-I (117%) compared with corn oil-fed animals. Although the addition of cholesterol to the corn oil diet significantly increased these parameters, no such effects were seen when cholesterol was added to the coconut-oil diet. Both the type of fat and cholesterol in the diet significantly affected HDL apo A-I metabolism by decreasing apo A-I fractional catabolic rate and increasing apo A-I production rate in the coconut oil-fed groups. The decrease in apo A-I fractional catabolic rate in the coconut oil-fed animals was also associated with an increase in the HDL core lipid to surface ratio. Liver apo A-I mRNA abundance was elevated in the coconut oil-fed groups; however, dietary cholesterol had no affect on these levels. The lack of parallel effects of dietary fat and cholesterol on apo A-I production rate and liver apo A-I mRNA levels suggests that the increase in the apo A-I production rate observed in the coconut oil-fed groups resulted from the fat-induced rise in liver apo A-I mRNA abundance, whereas the cholesterol-induced rise in the apo A-I production rate resulted from a mechanism other than changes in liver apo A-I mRNA levels.
Vascular responses to platelet activation in normal and atherosclerotic primates in vivo.
Authors: Kaul S , Heistad D D , Mügge A , Armstrong M L , Piegors D J , Lopez J A
Published: June 2011

Platelets release vasoactive substances that may contribute to augmented vasoconstriction. In this study, we examined vascular responses to activation of platelets in vivo by infusion of collagen. Purified bovine collagen was infused into the blood-perfused hind limb of normal and atherosclerotic cynomolgus monkeys. Resistance of the total limb and large arteries was measured at constant flow. In normal monkeys, collagen produced a decrease in total limb resistance, with a modest constrictor response of the large arteries. In atherosclerotic monkeys, collagen produced a transient, small decrease in total limb resistance, with pronounced constriction of large arteries. Indomethacin (5 mg/kg i.v.) and the thromboxane A2/prostaglandin H2 receptor antagonist SQ29,548 (2 mg/kg i.v.) virtually abolished the large-artery constrictor response to collagen in atherosclerotic monkeys. The 5-HT2-serotonergic receptor antagonist ketanserin (0.6 mg/kg i.v.) had no effect on the vasoconstrictor response. We conclude that 1) large arteries constrict and small vessels dilate in response to collagen-mediated activation of platelets in vivo in normal and atherosclerotic monkeys, 2) large-artery constriction in response to activation of platelets is augmented in atherosclerotic monkeys, and 3) the augmented large-artery constriction in atherosclerotic monkeys may be mediated primarily by thromboxane. The findings provide evidence that platelets may contribute to augmented constrictor responses of atherosclerotic arteries.
Influx in vivo of low density, intermediate density, and very low density lipoproteins into aortic intimas of genetically hyperlipidemic rabbits. Roles of plasma concentrations, extent of aortic lesion, and lipoprotein particle size as determinants.
Authors: Nordestgaard B G , Tybjaerg-Hansen A , Lewis B
Published: June 2011

To compare the atherogenic potential of low density lipoprotein (LDL), intermediate density lipoprotein (IDL), and very low density lipoprotein (VLDL) under conditions where plasma levels of these lipoproteins are elevated, the influx of cholesterol in these lipoproteins into the aortic intima was measured in vivo in genetically hyperlipidemic rabbits from the St. Thomas's Hospital strain, an animal model that shares many of the features of the human disorder familial combined hyperlipidemia. Univariate linear regression showed that the arterial influx of LDL cholesterol (n = 25), IDL cholesterol (n = 14), and VLDL cholesterol (n = 10) was positively and linearly associated with plasma concentrations of LDL cholesterol in the range 0.2-6.4 mmol/l, of IDL cholesterol in the range 0.1-7.0 mmol/l, and of VLDL cholesterol in the range 0.7-8.5 mmol/l, respectively, and also with the extent of lesions in the arterial intima in the range 0-100% of the surface area. Multiple linear regression suggested that the arterial influx of LDL, IDL, and VLDL cholesterol was linearly dependent on plasma concentration, independent of lesion size. Furthermore, it appeared that the arterial influx of the three lipoproteins was linearly dependent on the extent of the lesions, independent of lipoprotein concentration. When influx was normalized for plasma concentration (intimal clearance) and for lesion size (compared within the same aorta), the intimal clearance of the larger IDL and VLDL particles was 15-35% less than that of the smaller LDL particles. These findings suggest that the quantitatively most important mechanism for transfer of plasma lipoproteins into the arterial intima involves nonspecific molecular sieving and that at elevated plasma levels, IDL and VLDL share with LDL the potential for causing atherosclerosis.
Impaired vasodilatory response to atrial natriuretic peptide during atherosclerosis progression.
Authors: Hirata K , Akita H , Yokoyama M , Watanabe Y
Published: June 2011

This study was undertaken to examine the alterations in vascular relaxation responsiveness to endothelium-dependent or -independent vasodilators, including atrial natriuretic peptide (ANP) and acetylcholine, in aortas of Watanabe heritable hyperlipidemic (WHHL) rabbits during the progression of the atherosclerotic plaque. WHHL rabbits were divided into two groups according to age: group 1, 6-11 months, and group 2, 12-18 months. The isolated thoracic aortas obtained from both normal (control) and WHHL rabbits were suspended in a bath containing oxygenated Krebs' buffer for recording of isometric force. The endothelium-dependent relaxation evoked by acetylcholine was reduced in group 1 WHHL rabbits and decreased progressively in proportion to the degree of atherosclerosis progression when compared with age-matched control rabbits. ANP-induced relaxation was not significantly decreased in group 1 WHHL rabbits. However, ANP-induced relaxation was markedly impaired in group 2 WHHL rabbits. Thoracic aortas with severe atherosclerosis were less sensitive to ANP, with a significant increase in the median effective dose, although maximum relaxation induced by ANP was not reduced. Accumulation of cyclic GMP induced by ANP and acetylcholine was markedly reduced in atherosclerotic arteries obtained from group 2 WHHL rabbits compared with control rabbits. Vascular relaxation elicited by nitroglycerin or isoproterenol was not significantly impaired in atherosclerotic arteries from either group 1 or group 2 WHHL rabbits. From these results, we suggest that ANP-induced cyclic GMP formation and vascular relaxation via particulate guanylate cyclase in vascular smooth muscle cells are impaired in severely atherosclerotic arteries.
Quantification of atherosclerotic plaque composition in cholesterol-fed rabbits with 50-MHz acoustic microscopy.
Authors: Shepard R K , Miller J G , Wickline S A
Published: June 2011

To determine whether high-frequency ultrasound could distinguish normal from pathological vascular structure and to elucidate the determinants of ultrasonic backscatter in different layers of normal and atherosclerotic arteries, high-resolution acoustic microscopy at 50 MHz was used to characterize aortic plaque in six New Zealand White rabbits fed a 2% cholesterol diet for 3.5 months. Four rabbits were fed a standard diet for 3.5 months to provide normal control data. Segments of aortas were excised, fixed in formalin, opened longitudinally, and mounted flat for insonification. For each specimen, backscattered radio frequency (rf) data were acquired from 30 to 100 independent sites separated by 500 microns. Portions of rf data were gated from discrete layers of the vessel wall for computation of integrated backscatter. Results of histological and immunocytochemical analyses of vessel wall thickness and composition were compared with those of ultrasonic analysis. Normal aortas manifested prominent but homogeneous backscatter (average integrated backscatter, -28.5 +/- 2.9 dB) throughout the vessel wall, with no clear distinction between intimal and medial layers. The atherosclerotic aortas manifested substantially reduced integrated backscatter from the thickened intima (-47.5 +/- 3.2 dB, p < 0.0001) but relatively normal integrated backscatter from the media (-31.2 +/- 1.6 dB; p = NS versus normal aortas). The thickness of the media for both normal and atherosclerotic rabbits was approximately 300 microns. Histological characteristics of atherosclerotic aortas confirmed the presence of substantial intimal thickening, with prominent foam cell and lipid infiltration abutting a more normal medial layer.(ABSTRACT TRUNCATED AT 250 WORDS)
Vascular endothelium responds to fluid shear stress gradients.
Authors: DePaola N , Gimbrone M A , Davies P F , Dewey C F
Published: June 2011

In vitro investigations of the responses of vascular endothelium to fluid shear stress have typically been conducted under conditions where the time-mean shear stress is uniform. In contrast, the in vitro experiments reported here have re-created the large gradients in surface fluid shear stress found near arterial branches in vivo; specifically, we have produced a disturbed-flow region that includes both flow separation and reattachment. Near reattachment regions, shear stress is small but its gradient is large. Cells migrate away from this region, predominantly in the downstream direction. Those that remain divide at a rate that is high compared with that of cells subjected to uniform shear. We speculate that large shear stress gradients can induce morphological and functional changes in the endothelium in regions of disturbed flow in vivo and thus may contribute to the formation of atherosclerotic lesions.
Cholesterol efflux is defective in macrophages from atherosclerosis-susceptible White Carneau pigeons relative to resistant show racer pigeons.
Authors: Yancey P G , St Clair R W
Published: June 2011

White Carneau (WC) pigeons are susceptible to the development of aortic atherosclerosis, whereas Show Racer (SR) pigeons are resistant, even though there are no differences in the known risk factors, including plasma cholesterol levels, lipoproteins, blood pressure, etc. Although this suggests that the difference in atherosclerosis susceptibility between WC and SR pigeons may be mediated at the level of the arterial wall, we have yet to identify a mechanism that can account for this difference. In pigeons as in other species (including humans), macrophages play a major role in the pathogenesis of atherosclerosis. Pigeon macrophages have multiple mechanisms for the uptake of lipoproteins and the accumulation of cholesteryl esters. To date, however, no differences in lipoprotein uptake between macrophages of WC and SR pigeons have been identified that could explain the difference in atherosclerosis susceptibility. In the present study we explored the alternative hypothesis that there are differences in the rate of cholesteryl ester clearance from peritoneal macrophages isolated from the two breeds of pigeons. Cholesterol efflux studies were conducted with elicited pigeon peritoneal macrophages that were loaded with cholesteryl ester either in vitro by incubation with rabbit beta-very low density lipoprotein or in vivo by isolation of macrophages from birds fed a cholesterol-containing diet. Using these techniques we were able to load WC and SR macrophages consistently with cholesteryl esters to levels typical of arterial foam cells (150-1,150 micrograms/mg cell protein). Under these cholesterol loading conditions there was no net efflux of cholesterol from either WC or SR macrophages when incubated for up to 24 hours in the presence of pigeon or human high density lipoprotein (HDL), fetal bovine serum, or lipoprotein-deficient serum. Under the same conditions, efflux of cholesterol from mouse peritoneal macrophages was stimulated by human and pigeon HDL. Despite the inability of HDL, lipoprotein-deficient serum, or fetal bovine serum to promote net cholesterol efflux, apoprotein (apo) HDL/phosphatidylcholine (PC) vesicles stimulated cholesteryl ester clearance from both WC and SR pigeon macrophages but at a significantly slower rate from WC pigeon macrophages. When incubated in the presence of excess apoHDL/PC (400 micrograms/ml), the rate of depletion of cellular cholesteryl esters was log-linear for at least 48 hours. WC macrophages cleared an average of only 9% of their cholesteryl esters in 24 hours when incubated with excess apoHDL/PC, whereas SR macrophages reduced their cholesteryl ester content by an average of 42%.(ABSTRACT TRUNCATED AT 400 WORDS)
Mitogenic activity of interferon gamma on growth-arrested human vascular smooth muscle cells.
Authors: Yokota T , Shimokado K , Kosaka C , Sasaguri T , Masuda J , Ogata J
Published: June 2011

Interferon gamma (IFN-gamma) is a multifunctional lymphokine secreted by activated T lymphocytes, which are found in atherosclerotic lesions. IFN-gamma has been reported to suppress the proliferation of vascular smooth muscle cells (SMCs). However, as we report in this paper, IFN-gamma is mitogenic for vascular SMCs under certain circumstances. Recombinant human IFN-gamma (1-100 units/ml), in a dose-dependent fashion, stimulated cell multiplication and [3H]thymidine and 5-bromo-2'-deoxyuridine incorporation into DNA by cultured arterial SMCs that had been growth arrested by culturing in 1% plasma-derived serum for 5 days. IFN-gamma also accentuated the mitogenic activity of platelet-derived growth factor (PDGF)-BB. A time-course study revealed that there was a time lag of 4-6 hours between the G1-->S transition of quiescent SMCs stimulated by IFN-gamma and that of SMCs stimulated by PDGF-BB. A synergistic effect of IFN-gamma on the mitogenicity of PDGF became apparent after a similar time lag, suggesting that the IFN-gamma-related mitogenicity is mediated by a substance(s) secreted by IFN-gamma-treated SMCs. In fact, conditioned medium of IFN-gamma-treated SMCs was mitogenic for SMCs. Mitogenic activity in the conditioned medium was also detected by an assay using Swiss 3T3 cells, which originate from mice and, therefore, are not responsive to human IFN-gamma. The production of the mitogenic factor was blocked by anti-IFN-gamma antibody. Mitogenicity of the conditioned medium was not eliminated by addition of neutralizing antibody against PDGF, indicating that any autocrine growth factor(s) secreted by IFN-gamma-treated SMCs was not PDGF.(ABSTRACT TRUNCATED AT 250 WORDS)
LDL particle size distribution. Results from the Framingham Offspring Study.
Authors: Campos H , Blijlevens E , McNamara J R , Ordovas J M , Posner B M , Wilson P W , Castelli W P , Schaefer E J
Published: June 2011

Using 2-16% gradient gel electrophoresis, we examined low density lipoprotein (LDL) particle size in relation to plasma lipoproteins in 1,168 women and 1,172 men from the Framingham Offspring Study. In addition, we studied the effect of dietary intake on LDL size in a subset of the population. Seven LDL size peaks were identified, with the largest, LDL 1, being found in the density range 1.019-1.033 g/ml; LDL 2 and LDL 3 in d = 1.033-1.038 g/ml; LDL 4 and LDL5 in d = 1.038-1.050 g/ml; and the smallest, LDL 6 and 7, in d = 1.050-1.063 g/ml. Seventy-seven percent of the population had one major and at least one minor LDL peak. Secondary LDL peaks accounted for 23% of the total LDL relative area, based on laser scanning densitometry. LDL size distribution was skewed toward larger LDL particles in women (prevalence of LDL 1, 30% and of LDL 2, 31%), whereas men exhibited a more symmetric distribution (prevalence of LDL 3, 42%). The prevalence of small (< 255 A), dense (d > 1.038 g/ml) LDL particles 4-7 was 33% in men, 5% in premenopausal women, and 14% in postmenopausal women. In agreement with previous reports, small, dense LDL particles were significantly (p < 0.0001) associated with increased triglyceride and apolipoprotein (apo) B levels and decreased HDL cholesterol and apo A-I levels. In addition, we found a significant (p < 0.0001) association between LDL cholesterol and LDL size. The highest LDL cholesterol levels were found among women with LDL 4 (148 mg/dl) and men with LDL 3-5 (138 mg/dl). In addition, the presence of LDL 3 or 4 as secondary peaks was significantly associated with higher LDL cholesterol levels, while smaller secondary LDL peaks were associated with higher triglyceride levels. We also found that compared with subjects with optimal LDL cholesterol levels (< 130 mg/dl), individuals with high-risk LDL cholesterol levels (> or = 160 mg/dl) had 1) a higher prevalence of LDL 3 and 4 (women only) and a lower prevalence of LDL 1 and 2 (women only) and 2) 11% higher LDL cholesterol to apo B ratios, even when matched for LDL particle size. Furthermore, low saturated fat and cholesterol intakes were significantly associated (p < 0.01) with smaller LDL particles. Therefore, the identification of small, dense LDL particles per se may not be a good indicator of coronary artery disease risk in population studies.(ABSTRACT TRUNCATED AT 400 WORDS)
Augmented arterial wall expression of type-1 plasminogen activator inhibitor induced by thrombosis.
Authors: Sawa H , Fujii S , Sobel B E
Published: June 2011

Type-1 plasminogen activator inhibitor (PAI-1), the primary physiological inhibitor of endogenous plasminogen activators, modulates fibrinolysis, cell migration, and tissue repair. To determine whether genetic expression of PAI-1 is augmented in the walls of vessels exposed to thrombi but not to a direct physical insult such as electrical injury, we induced arterial thrombosis in rabbit carotid arteries with intraluminal surgical silk sutures and performed in situ hybridization for PAI-1 messenger RNA (mRNA) and immunohistochemistry for PAI-1 antigen at selected intervals. PAI-1 activity in plasma remained virtually constant. In contrast, PAI-1 mRNA increased in endothelial cells juxtaposed to thrombi, in smooth muscle cells adjacent to the neointima, and in macrophages surrounding the suture material. PAI-1 protein was detected in regions in which PAI-1 mRNA was expressed. The increased expression of PAI-1 mRNA colocalized with PAI-1 protein in the endothelium juxtaposed to thrombi may potentiate thrombosis by shifting the local balance between fibrinolysis and thrombosis toward thrombosis. Furthermore, it may alter vascular remodeling and predispose to stenosis after interventions such as angioplasty, in which local thrombosis cannot be avoided.
Effect of pressure on aortic hydraulic conductance.
Authors: Baldwin A L , Wilson L M , Simon B R
Published: June 2011

This study was performed to determine whether the transmural hydraulic conductance (Lp) of the rabbit aortic wall depends on its distension. In 19 rabbits, the aorta was cannulated in situ and perfused at a given pressure with a physiologically buffered solution containing 4% bovine serum albumin. The output cannula was then occluded to limit fluid flow to that traversing the artery wall. External diameter and transmural fluid flow were measured at three pressures (eight rabbits, group 1) or at four pressures (12 rabbits, group 2) in each vessel. Transmural fluid flow was determined by monitoring the velocity of an air bubble within a buffer-filled tube leading to the input cannula. From group 1 measurements, Lp values (mean +/- SD) at 50, 100, and 150 mm Hg were calculated to be 3.8 +/- 2.8, 3.5 +/- 1.3, and 4.1 +/- 1.2 x 10(-8) cm/sec/mm Hg, respectively. Group 2 measurements gave values of 4.2 +/- 1.6, 3.8 +/- 1.1, 3.8 +/- 1.1, and 4.2 +/- 1.1 x 10(-8) cm/sec/mm Hg at 75, 100, 125, and 150 mm Hg, respectively. Paired Student's t tests indicated no significant change in Lp with pressure. However, linear regression analysis demonstrated a weak correlation between Lp values obtained at 50 and 100 mm Hg (r2 = 0.30) and at 75 and 100 mm Hg (r2 = 0.36). Values of Lp at 100 and 150 mm Hg and at 125 and 150 mm Hg were closely correlated in each case. These results suggest that between 50 and 100 mm Hg the structural properties of the aortic wall change so as to alter Lp but not in the same way in each vessel. Lp may increase or decrease depending on which structural change predominates in a particular vessel.
Low density lipoprotein particle size and coronary artery disease.
Authors: Campos H , Genest J J , Blijlevens E , McNamara J R , Jenner J L , Ordovas J M , Wilson P W , Schaefer E J
Published: June 2011

Decreased plasma low density lipoprotein (LDL) particle size has been associated with premature coronary artery disease (CAD). We examined LDL particle size by 2-16% gradient gel electrophoresis in 275 men with CAD (greater than 75% cross-sectional-area stenosis) and 822 controls. Seven major LDL size bands (with LDL-1 [d = 1.025-1.033 g/ml] being the largest and LDL-7 [d = 1.050-1.063 g/ml, the smallest]) were identified. Because most subjects had two or more adjacent LDL bands, an LDL score was calculated for each subject, with the relative area in each band taken into consideration. Four major LDL particle size groups were classified in the present studies: large LDL, intermediate LDL, small LDL, and very small LDL. The use of beta-blockers was significantly associated with smaller LDL particles. After adjusting for use of this medication, small LDL particles were still more prevalent in CAD patients (39%) compared with controls (27%). The prevalence of large LDL particles was lower in CAD patients (3%) than in controls (24%). Intermediate LDL particles were the most prevalent in both groups, 49% in CAD patients and 46% in controls. The difference in LDL particle size between CAD patients and controls was not independent but was highly associated (p less than 0.0001) with elevated triglyceride levels and decreased high density lipoprotein (HDL) cholesterol levels. Significantly higher LDL cholesterol levels were found in subjects with intermediate and small LDL particles than in those with large or very small LDL particles.(ABSTRACT TRUNCATED AT 250 WORDS)
Platelet function and composition in heart transplant recipients compared with nontransplanted coronary patients.
Authors: de Lorgeril M , Dureau G , Boissonnat P , Guidollet J , Juhan-Vague I , Bizollon C , Renaud S
Published: June 2011

Accelerated coronary artery disease seems to be the main condition limiting long-term survival after heart transplantation. Ninety-one heart transplant recipients were compared with 94 nontransplanted coronary artery disease patients in an attempt to identify the factors responsible for the accelerated form of coronary artery disease occurring after heart transplantation. Among the parameters examined, heart transplant recipients exhibited a higher plasma level of insulin (8.5 +/- 0.5 versus 6.2 +/- 0.3 mIU/l, p = 0.002), a lower plasma level of vitamin E (14.8 +/- 0.4 versus 16.9 +/- 0.7 mg/l, p = 0.03), a higher platelet cholesterol-to-phospholipid ratio (8.9 +/- 0.3 versus 7.6 +/- 0.3, p = 0.007), and an increased response to ADP-induced platelet aggregation (for the first wave, 29.1 +/- 0.9% of maximal aggregation versus 25.1 +/- 1.0%, p = 0.002; for the second wave, 21.4 +/- 1.4% versus 15.9 +/- 1.1%, p = 0.002, after adjustment for hematocrit), but no untoward changes in the level of fibrinogen, plasminogen activator inhibitor-1, antithrombin III, or lipoprotein(a). In addition, platelet aggregation in patients who required retransplantation as a result of severe coronary artery disease was similar before and after retransplantation. This suggests that severe coronary artery disease is not the cause of platelet hyperaggregability. In multiple-regression analysis, ADP-induced platelet aggregation in heart transplant recipients was significantly positively related to blood glucose (r = 0.50, p less than 0.001) and inversely related to n-3 fatty acids from platelet phospholipids (r = 0.40, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Lipoprotein-proteoglycan complexes from atherosclerotic lesions promote cholesteryl ester accumulation in human monocytes/macrophages.
Authors: Vijayagopal P , Srinivasan S R , Radhakrishnamurthy B , Berenson G S
Published: June 2011

Lipoprotein-proteoglycan complexes from human atherosclerotic lesions were studied to determine their ability to stimulate cholesteryl ester accumulation in human monocytes/macrophages. Complexes containing apolipoprotein (apo) B lipoproteins and proteoglycans were extracted from fatty streaks and fibrous plaque lesions of human aortas by extraction with 0.15 M NaCl. Fractionation of the complex with Bio-Gel A-50m yielded a single fraction from fatty streaks and two fractions from fibrous plaques. The complexes were further purified by anti-apo B affinity chromatography and analyzed for apolipoproteins, lipids, and glycosaminoglycans Apo B was the only apolipoprotein present in the complexes. Although the complexes from fatty streaks and fibrous plaques contained varying proportions of hyaluronic acid, chondroitin 6-sulfate, and dermatan sulfate, heparin was present in only the fibrous plaque complexes. All three lipoprotein-proteoglycan complexes increased the rate of incorporation of [14C]oleate into cholesteryl [14C]oleate and stimulated cholesteryl ester accumulation in monocytes/macrophages. However, the complexes from fibrous plaques were more potent than those from fatty streaks in this regard. Cholesteryl ester synthesis that is mediated by the uptake of the complexes was dose dependent and showed apparent saturation, suggesting that cell surface binding may be required. Chloroquine, a lysosomotropic agent, inhibited cholesteryl ester synthesis that is induced by the complexes, indicating that lysosomal hydrolysis was essential. Cholesteryl ester synthesis that is mediated by the complexes was inhibited 70-79% by polyinosinic acid. Furthermore, excess unlabeled fibrous plaque complexes significantly inhibited the binding and internalization of in vitro 125I-low density lipoprotein (LDL)-proteoglycan complexes and 125I-acetylated-LDL and not 125I-LDL. These results suggest the involvement of the scavenger receptor in the uptake of the complexes. Phagocytosis played a minor role in the metabolism of these ligands because cytochalasin D inhibited cholesteryl ester synthesis, which is mediated by fibrous plaque complexes, by 7.5-25%. Cholesteryl ester synthesis increased linearly over 32 hours in macrophages incubated with the complexes, indicating an apparent lack of downregulation of binding sites. This resulted in the appearance of intracellular oil red O-positive lipid droplets. These studies show for the first time that apo B lipoprotein-proteoglycan complexes isolated from human atherosclerotic lesions can induce cholesteryl ester accumulation in monocytes/macrophages.
Correlation of factor VII activity and antigen with cholesterol and triglycerides in healthy young adults.
Authors: Hoffman C J , Miller R H , Hultin M B
Published: June 2011

Prospective epidemiological studies found that the plasma level of factor VII activity was a risk factor for ischemic heart disease (IHD). Our laboratory previously demonstrated that young adults (mean age, 35 years) at high risk of IHD had significantly higher plasma factor VII activity and antigen levels than did comparable young adults at low risk. To study the relation of factor VII with lipid metabolism in even younger adults (less than 30 years), using standard techniques we measured plasma factor VII activity and antigen, plasma fibrinogen, and fasting serum lipid fractions in healthy male and female subjects who were at low risk of IHD and who were not on medication. Factor VII antigen correlated significantly with total serum cholesterol, fasting serum triglycerides, and high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol (p less than 0.01), and factor VII activity correlated with total and HDL cholesterol (p less than 0.05) in the men (n = 132); however, fibrinogen level did not correlate significantly with any lipid level in this group. We found no significant correlation of factor VII activity or antigen with any lipid levels in the women (n = 65). Our data support the hypothesis that control of plasma factor VII level is linked to lipid metabolism in normal physiology in men. Thus, factor VII level may reflect the mechanism by which male gender imparts added risk for IHD, independent of other established risk factors. This study also supports the use of the factor VII antigen assay, a highly reproducible method, in studies of the relation of factor VII to the risk of IHD.
Oxidized low density lipoproteins stimulate phosphoinositide turnover in cultured vascular smooth muscle cells.
Authors: Resink T J , Tkachuk V A , Bernhardt J , Bühler F R
Published: June 2011

Atherogenesis is associated with alterations in the properties of different cell types, including monocytes/macrophages (foam cell formation), platelets (increased aggregation), endothelial cells (injury), and smooth muscle cells (SMCs) (lipid accumulation or foam cell formation). Oxidized low density lipoproteins (ox-LDL) play a key role in this vascular pathology. This study investigated the ability of ox-LDL to elicit chemical signaling events in cultured human vascular smooth muscle cells (VSMCs). Ox-LDL was found to stimulate phospholipase C-mediated phosphoinositide turnover in human VSMCs. This response occurred rapidly (within 1 minute) and at low concentrations of ox-LDL (half-maximal effective concentration, approximately 5 micrograms/ml). Ox-LDL-stimulated inositol phosphate accumulation in human VSMCs was inhibited by pretreatment of cells with phorbol 12-myristate 13-acetate and with compounds that elevate cyclic AMP or cyclic GMP. Ca2+ antagonists also blocked the effects of ox-LDL on phosphoinositide turnover. Inhibitors of receptor-endocytotic processes (including receptor clustering, cross-linking, and cytoskeleton-dependent internalization) effectively prevented ox-LDL-induced inositol phosphate generation. The data suggest that ox-LDL promotes phospholipase C-mediated phosphoinositide turnover in a manner analogous to that for other Ca(2+)-mobilizing hormones. The results also support an association between phosphoinositide turnover and receptor-mediated endocytosis. Prevention of the direct effects of ox-LDL on SMCs could prove an interesting therapeutic avenue for the prevention of atherosclerosis.
Tissue and species differences in bile salt-dependent neutral cholesteryl ester hydrolase activity and gene expression.
Authors: Zolfaghari R , Harrison E H , Han J H , Rutter W J , Fisher E A
Published: June 2011

Enzymatic activity and mRNA abundance for neutral bile salt-dependent cholesteryl ester hydrolase (CEH) were determined in rat and rabbit tissues. In rat liver and intestine, enzyme activity and mRNA levels varied independently. Particularly striking in most tissue samples was the absence of detectable CEH mRNA in the presence of enzymatic activity, suggesting that there was an exogenous source of enzyme. Rabbits differed from rats in four ways. First, neither CEH activity nor mRNA was present in any liver sample. Second, CEH mRNA was present in nearly all intestinal samples, and its abundance tended to correlate with enzymatic activity. Third, rabbit CEH mRNA was approximately 250 bases shorter than the rat message. Fourth, we have previously shown that rat plasma contains CEH activity, whereas in the present studies, rabbit plasma did not contain such activity. Overall, our studies indicate that CEH activity in rat liver, intestine, and plasma can be derived exogenously, most likely from the uptake and transport of pancreatic enzyme. In contrast, in rabbit the lack of CEH activity in plasma and liver and the capacity of the intestine for in situ synthesis of CEH suggest that this animal does not have the same ability to distribute pancreatic CEH. These species differences in CEH metabolism may partly explain the greater susceptibility of rabbit tissues to accumulate cholesteryl esters.
Associations of lipoproteins and apolipoproteins with gradient gel electrophoresis estimates of high density lipoprotein subfractions in men and women.
Authors: Williams P T , Krauss R M , Vranizan K M , Stefanick M L , Wood P D , Lindgren F T
Published: June 2011

We examined the relations of gender and lipoproteins to subclasses of high density lipoproteins (HDLs) in a cross-sectional sample of moderately overweight men (n = 116) and women (n = 78). The absorbance of protein-stained polyacrylamide gradient gels was used as an index of mass concentrations of HDL at intervals of 0.01 nm across the entire HDL particle size range (7.2-12 nm). At least five HDL subclasses have been identified by their particle sizes: HDL3c (7.2-7.8 nm), HDL3b (7.8-8.2 nm), HDL3a (8.2-8.8 nm), HDL2a (8.8-9.7 nm), and HDL2b (9.7-12 nm). Men had significantly higher HDL3b and significantly lower HDL2a and HDL2b than did women. Correlations of HDL subclasses with concentrations of other lipoprotein variables were generally as strong for gradient gel electrophoresis as for analytical ultracentrifugation measurements of HDL particle distributions. In both sexes, high levels of HDL3b were associated with coronary heart disease risk factors, including high concentrations of triglycerides, apolipoprotein B, small low density lipoproteins, intermediate density lipoproteins, and very low density lipoproteins and low concentrations of HDL2 cholesterol and HDL2 mass. Plasma concentrations of HDL3 cholesterol were unrelated to protein-stained HDL3b levels. HDL3 cholesterol concentrations also did not exhibit the sex difference or the relations with lipoprotein concentrations that characterized HDL3b. Thus, low HDL3b levels may contribute in part to the low heart disease risk in men and women who have high HDL cholesterol. Measurements of HDL3 cholesterol may not identify clinically important relations involving HDL3b.
Immunolocalization of native antioxidant scavenger enzymes in early hypertensive and atherosclerotic arteries. Role of oxygen free radicals.
Authors: Sharma R C , Crawford D W , Kramsch D M , Sevanian A , Jiao Q
Published: June 2011

To elucidate the role of oxygen free radicals and lipid peroxidation in the pathogenesis of early hypertension and atherosclerosis, we studied the native distribution of three primary arterial antioxidant enzymes (AEs). Specific immunohistochemical localization of superoxide dismutase (Cu-Zn SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) was examined in the arterial wall of New Zealand White rabbits: six sham-operated normotensive/normolipidemics (NT/NL), seven coarctation-induced hypertensive/normolipidemics (HT/NL), eight normotensive diet-induced hyperlipidemics (NT/HL), and six hypertensive/hyperlipidemics (HT/HL). All three AEs were confined primarily to the endothelium in NT/NL rabbit aortas. However, in HT and HL rabbits a greater proportion of the arterial wall, including the endothelium, inner media, and middle media, displayed immunolocalization of three AEs. Multiple linear-regression analysis revealed that more than 70% of the total variability in the depth of immunolocalization of arterial AEs could be explained by changes in blood pressure and/or total cholesterol. Also, levels of plasma and arterial cholesterol oxides were significantly different (p less than 0.05) in HT and HL rabbits compared with controls, with twofold increases in NT/HLs, threefold increases in HT/NLs, and fourfold increases in HT/HLs. We conclude that intense free-radical activity in the arterial wall of HT and HL animals is one possibility and that this occurs despite the presence of abundant AEs.
Polymyxin B enhances low density lipoprotein catabolism in hepatic and extrahepatic cells.
Authors: Liao W , Florén C H
Published: June 2011

We investigated the effects of polymyxin B (PMB), an antibiotic that binds to endotoxins, on the uptake and degradation of low density lipoproteins (LDLs) in HepG2 cells, a highly differentiated human hepatoma cell line. The results showed that PMB very effectively enhanced the binding, internalization, and degradation of LDL in HepG2 cells. The PMB-mediated enhancement of LDL uptake was not dependent on the LDL receptor-mediated pathway, as blockage of the LDL receptor by use of a monoclonal anti-LDL receptor antibody had no effect on the PMB-mediated cellular processing of LDL and PMB-mediated enhancement of LDL uptake did not cause an increase in cholesterol esterification. In addition, chloroquine and colchicine, which inhibit lysosomal degradation and cellular endocytosis, respectively, diminished PMB-enhanced degradation of LDL, indicating that PMB mediates uptake through a pathway similar to the LDL receptor-mediated pathway. The PMB-mediated uptake of LDL was sensitive to treatment with phospholipase C and pronase and was dependent on the presence of Ca2+. PMB caused similar changes in human skin fibroblasts, bovine smooth muscle cells, and bovine endothelial cells, which suggests that PMB-enhanced LDL uptake is a general cellular phenomenon. Our results thus indicate that PMB increases cellular catabolism of LDL through an endocytotic pathway not involving the LDL receptors.
Persistent generation of thrombin after acute myocardial infarction.
Authors: Szczeklik A , Dropinski J , Radwan J , Krzanowski M
Published: June 2011

During the acute phase of myocardial infarction, the generation of thrombin is reflected in the sudden rise of fibrinopeptide A (FPA) and the thrombin-antithrombin III (TAT) complex in blood. We have systematically determined the FPA and TAT plasma concentrations over a period of 14 days after acute myocardial infarction in 100 patients. Mean levels of both thrombin markers were the highest on admission, remained elevated over the following few days, and then gradually declined after day 5. Still, by the end of the first week two thirds of the patients had distinctly elevated TAT and FPA levels, and by the end of the second week such an abnormality was present in half of them. Continuous intravenous heparin infusion at a dose of 20,000 units/day, administered for 1 week to patients who had either received (n = 21) or not received (n = 17) streptokinase, led to a significant depression (p less than 0.05) of thrombin markers over the first 48 hours, an effect that did not persist over the subsequent days of treatment. In patients not assigned to heparin treatment, those in heart failure had significantly (p less than 0.05) higher mean TAT and FPA values on days 3, 5, and 7 compared with patients in whom heart failure was absent. Infarct extension, pulmonary embolism, and death were also associated with a rise in one or both thrombin markers, often preceding the onset of clinical symptoms. Thrombinogenesis was not accompanied by changes in mean plasma concentrations of prothrombin, antithrombin III, or alpha 2-macroglobulin.(ABSTRACT TRUNCATED AT 250 WORDS)
Supplementation with vitamin E but not beta-carotene in vivo protects low density lipoprotein from lipid peroxidation in vitro. Effect of cigarette smoking.
Authors: Princen H M , van Poppel G , Vogelezang C , Buytenhek R , Kok F J
Published: June 2011

Several lines of evidence suggest that oxidatively modified low density lipoprotein (LDL) is atherogenic and that antioxidants may protect LDL against oxidation. In addition, cigarette smoking is known to induce oxidant stress. We have examined the effect of ingestion of the antioxidants D,L-alpha-tocopherol (vitamin E) and beta-carotene and of smoking on the resistance of LDL against copper-mediated oxidation. Six healthy nonsmoking volunteers ingested 1,000 IU/day D,L-alpha-tocopherol acetate for 7 days. After vitamin E ingestion concentrations of alpha-tocopherol in plasma and LDL increased 3.0- and 2.4-fold, respectively. Simultaneously, the oxidation resistance of LDL was elevated significantly (+41%), and the rate of oxidation was decreased significantly (-19%). The increase in alpha-tocopherol content of LDL and the increase in resistance time were highly correlated (rs = 0.89, p = 0.014). Eight weeks after termination of the vitamin E intake, alpha-tocopherol concentrations in plasma and LDL and oxidation resistance of LDL had returned to baseline values. In smokers (n = 46), plasma levels of vitamin C (-26%) and concentrations of beta-carotene (-44%, -43%) and total carotenoids (-23%, -29%) in plasma and LDL, respectively, were significantly lower compared with nonsmokers (n = 23). No differences were found in alpha-tocopherol content of LDL and the susceptibility of LDL to lipid peroxidation in both groups. Supplementation of a group of smokers in a 14-week randomized, double-blind, placebo-controlled intervention trial with beta-carotene resulted in a 16.6- and 5.0-fold increase of LDL beta-carotene and total carotenoid content, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Increased sitosterol absorption is offset by rapid elimination to prevent accumulation in heterozygotes with sitosterolemia.
Authors: Salen G , Tint G S , Shefer S , Shore V , Nguyen L
Published: June 2011

Using plasma isotope-kinetic methods, we measured the absorption and turnover rates of cholesterol and sitosterol (24-ethylcholesterol) in two obligate heterozygotes (parents) and their homozygous daughter with sitosterolemia with xanthomatosis. Diets contained approximately 500 mg/day cholesterol and 100 mg/day sitosterol. In the homozygote, plasma cholesterol and apolipoprotein B concentrations were slightly higher, but sitosterol levels were 22 and 58 times higher than in her heterozygous parents. Cholesterol absorption was at the high end of the normal range in both heterozygotes (59% and 84%) and in the homozygote (62%) (value in the control subject 48%). In contrast, cholesterol synthesis was severely depressed in the homozygote (28% and 26% as great as in the heterozygotes and the control, respectively). Sitosterol absorption in the homozygote (34%) was 2.3 and 2.0 times greater than in the heterozygotes and 6.8 times greater than in the control. The sitosterol turnover rate, calculated independently by mathematical analysis of specific-activity decay curves, amounted to 15 and 24 mg/day in the heterozygotes compared with 27 mg/day in the homozygote and 7.9 +/- 2.3 mg/day in five control subjects. However, the total body sitosterol pool was 15 and 10.3 times larger in the homozygote (4,080 mg) than in her heterozygous parents because of extremely slow removal. The average sitosterol elimination constant in the heterozygotes (KA = 0.11 day-1) was 10 times that in the homozygote (KA = 0.01 day-1) but 35% less than that in the controls (KA = 0.17 day-1).(ABSTRACT TRUNCATED AT 250 WORDS)
The role of cholesteryl ester transfer protein in primate apolipoprotein A-I metabolism. Insights from studies with transgenic mice.
Authors: Marotti K R , Castle C K , Murray R W , Rehberg E F , Polites H G , Melchior G W
Published: June 2011

To assess the effects of cholesteryl ester transfer protein (CETP) on the primate lipoprotein profile, a transgenic mouse expressing cynomolgus monkey CETP was developed. The C57BL/6 mouse was used, and four lines expressing the primate CETP were established. The level of CETP activity in the plasma of the transgenic mice ranged from values similar to those obtained for the monkey to levels approximately sixfold higher than that in the normal monkey. When all of the lines were taken into consideration, there was a strong (r = -0.81 or higher, p less than 0.01) negative correlation between plasma CETP activity and total plasma cholesterol, plasma apolipoprotein (apo) A-I levels, and plasma apo A-I to apo B ratio. There was a strong positive correlation (r = 0.77) between plasma CETP activity and plasma apo B levels. The size of the apo A-I-containing lipoproteins was significantly reduced in mice with high plasma CETP activity, and that reduction in size was due to the absence of the larger (HDL1 and HDL2) apo A-I-containing particles in the plasma. When the transgenic mice were fed a high-fat, high-cholesterol diet, the effects of the diet on lipoprotein profile were more prominent in the CETP transgenic mice than the controls. The CETP transgenic mice had, for example, substantially higher plasma cholesterol and plasma apo B levels (p less than 0.01), and the apo B-containing lipoproteins were generally larger than those in the nontransgenic C57BL/6 mice consuming the same diet.(ABSTRACT TRUNCATED AT 250 WORDS)