bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipoprotein(a) impairs generation of plasmin by fibrin-bound tissue-type plasminogen activator. In vitro studies in a plasma milieu.
Authors: Rouy D , Grailhe P , Nigon F , Chapman J , Anglés-Cano E
Published: June 2011

Apoprotein(a), (apo[a]), the specific antigen of lipoprotein(a) (Lp[a]), consists of structural domains (a serine protease unit, kringles 4 and 5) with marked homology to those of the corresponding domains in plasminogen. In this study, we have investigated the impact of this unique structural mimicry on the binding and activation of plasminogen by fibrin-bound tissue-type plasminogen activator at the plasma-fibrin interface. We found that the total amount of plasmin generated on the surface of fibrin was decreased in the presence of high concentrations of Lp(a): 197 +/- 65 fmol in plasmas with greater than 60 mg/dl Lp(a) versus 287 +/- 112 fmol in control plasmas. A similar effect was also apparent in the corresponding euglobulin fractions (554 +/- 169 fmol versus 754 +/- 310 fmol), the latter lacking the plasminogen-binding proteins alpha 2-antiplasmin and histidine-rich glycoprotein, but containing Lp(a). The difference between plasma samples was significant (p less than 0.05) as calculated from the percent decrease in plasmin generated from plasmas with high levels of Lp(a) relative to that generated in the paired controls with low Lp(a) levels. The involvement of Lp(a) was verified in a reconstituted system consisting of normal human plasma supplemented with 100 mg/dl of either purified Lp(a) or low density lipoprotein. Lp(a) produced a decrease of 30% in the generation of plasmin (180 fmol versus 255 fmol in plasma, and 485 fmol versus 705 fmol in the euglobulin fraction). Moreover, using a radiolabeled sheep antibody against human apo(a), we were able to demonstrate the binding of 40 fmol Lp(a) to fibrin during ongoing plasminogen activation. These results indicate that Lp(a) impairs the binding of plasminogen to fibrin and thereby decreases the generation of plasmin by occupying C-terminal lysine residues unveiled on the fibrin surface by plasmin degradation as recently reported (Circulation 1990;82[suppl III]:III-92). In consequence, impairment of fibrinolysis and accumulation of Lp(a) at sites of vascular injury may occur, factors that may be important in the development of atherosclerosis and associated thrombosis.
Chronic rejection in rat aortic allografts. An experimental model for transplant arteriosclerosis.
Authors: Mennander A , Tiisala S , Halttunen J , Yilmaz S , Paavonen T , Häyry P
Published: June 2011

Chronic rejection has several histological appearances, depending on the type of organ graft. Common to all of them is transplant arteriosclerosis associated with an ongoing inflammatory response in the transplanted graft. To the contrary of classical atherosclerosis, in which the manifestations are mostly focal, proximal, and asymmetric, transplant arteriosclerosis is generalized, and the intimal thickening is concentric. In this article, we describe an experimental animal model whereby transplant arteriosclerosis may be investigated in the inbred rat. Aortic allografts were transplanted from DA (RTIa) to major histocompatibility complex-incompatible WF (RTIv) rats or, for control, to rats of the DA strain. Transplantation was followed by an acute inflammation episode in the aortic adventitia of the allograft, largely lacking in the syngeneic graft, with a prominence of lymphoid activation markers (Cd25) in the cells of the inflammatory infiltrate. The inflammation episode peaked at 2 months after transplantation, became attenuated, and was followed by a proliferative response of myocytes in the allograft media. An increase in the migration of myocytes to the subendothelial space (presumably through small breaks generated in the internal elastic lamina) was observed thereafter, and myocyte proliferation continued in the intima with some intermingled macrophages. Finally, necrosis and disappearance of myocytes and their replacement by fibrous tissue were observed in the media. These alterations are virtually identical with the vascular lesion of chronically rejecting parenchymal organ transplants in human subjects. We suggest that aortic allografts exchanged between histoincompatible rat strains may be used as an experimental model for transplant arteriosclerosis.
Atherosclerosis. Chronic effects of fish oil and a therapeutic diet in nonhuman primates.
Authors: Fincham J E , Gouws E , Woodroof C W , van Wyk M J , Kruger M , Smuts C M , van Jaarsveld P J , Taljaard J J , Schall R , Strauss J A
Published: June 2011

Prolonged testing of marine fish oil (FO) as a dietary supplement is necessary because of widespread claims that it is antiatherogenic. The basis for such claims is inadequate because atherogenesis is chronic and may not respond to short-term changes induced by dietary treatments. A proven (vervet) model of atherosclerosis promoted by an atherogenic diet (AD) was used to test dietary supplementation with Atlantic pilchard FO for 20 months in 47 omnivorous nonhuman primates. Responses were controlled against known favorable effects of changing from the AD to a therapeutic diet (TD). Compliance was achieved, and tissue responses to the FO dose were confirmed. Compromise of reflex vasoconstriction by atherosclerosis was demonstrated for the first time in the model. Aortic, peripheral, coronary, and cerebral atherosclerosis were assessed by light microscopy and computerized image analysis. No component of atherosclerosis regressed after dietary FO, and several deteriorated. After a change to the TD, stainable lipid was cleared from aortas and there were few lipophages, but advanced atherosclerosis was not reduced. Male vervets developed more severe atherosclerosis than did females, and the association among aortic, peripheral, and coronary atherosclerosis was positive in males. Females were resistant to coronary atherosclerosis. Only mild cerebral atherosclerosis was detected. In conclusion, the FO used was not antiatherogenic in the model, and there is a need for caution. The TD regresses some components of atherosclerosis, but it was not effective against fibrosis, mineralization, and cholesterol crystals within 20 months.
Probucol treatment affects the cellular composition but not anti-oxidized low density lipoprotein immunoreactivity of plaques from Watanabe heritable hyperlipidemic rabbits.
Authors: O'Brien K , Nagano Y , Gown A , Kita T , Chait A
Published: June 2011

Use of the antioxidant probucol has been associated with a reduction in the development of atherosclerotic lesions in Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of familial hypercholesterolemia. In this study, atheromatous lesions from control or probucol-treated WHHL rabbits were probed with monoclonal antibodies to evaluate whether use of this drug either affected the presence or distribution of epitopes recognized by an antibody against oxidized low density lipoprotein or altered the cellular makeup of lesions. Although probucol-treated animals had much less aortic atherosclerosis than did controls, equivalent immunoreactivity for the anti-oxidized LDL antibody (OXL 41.1) was demonstrated in atherosclerotic lesions of both groups of animals, consistent with a role for oxidative modification of lipoproteins in atherogenesis in this animal model. Use of smooth muscle cell-specific (HHF-35) and macrophage-specific (RAM-11) antibodies demonstrated that lesions from probucol-treated animals were significantly smaller (p less than 0.01) and less cellular (p less than 0.05) than were control lesions. In addition, smooth muscle cells were the predominant cell type in lesions from probucol-treated animals, whereas macrophages predominated in lesions from controls (p less than 0.01). These findings are consistent with a reduction of monocyte/macrophage recruitment into or retention in lesions in probucol-treated animals, or with probucol-induced alterations in the production of growth factors or cytokines that might influence the cellular makeup of atherosclerotic lesions.
Interaction of LpB, LpB:E, LpB:C-III, and LpB:C-III:E lipoproteins with the low density lipoprotein receptor of HeLa cells.
Authors: Agnani G , Bard J M , Candelier L , Delattre S , Fruchart J C , Clavey V
Published: June 2011

In this study we measured the binding parameters of different apolipoprotein (apo) B-containing lipoproteins to the low density lipoprotein (LDL) receptor of HeLa cells. Our goal was to determine the respective roles of the different apolipoproteins of these particles, with particular emphasis on apos B, E, and C-III. Very low density lipoprotein from hypertriglyceridemic subjects (B to E molar ratio = 1:16) bound to HeLa cells with an affinity higher than that of LDL, but the apparent number of binding sites per cell was lower. Because of the heterogeneity of these lipoproteins, which were isolated by ultracentrifugation, we used immunoaffinity chromatography to define these particles on the basis of their apolipoprotein content. Lipoprotein B (LpB) particles that contained apo B as their sole apolipoprotein had lower affinity for the LDL receptor than did total LDL but had an apparently higher number of binding sites. The presence of apo E of phenotype E3/E3 or E4/E4 on one particle increased the affinity of the apo B-containing lipoprotein for the LDL receptor. The apparent number of binding sites decreased, probably due to the fact that a lipoprotein particle containing multiple copies of apo E bound to more than one molecule of LDL receptor. Interaction with several LDL receptors would also explain the higher binding affinity that we observed. The calculated number of binding sites expressed for each apo E molecule is close to the number of binding sites for lipoproteins containing only apo B (LpB or LDL), indicating that each apo E can interact with one LDL receptor. When the apo E phenotype was E2/E2, the LpB:E lipoproteins did not bind to the LDL receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of protein kinase C and cyclic adenosine monophosphate in the regulation of tissue-type plasminogen activator, plasminogen activator inhibitor-1, and platelet-derived growth factor mRNA levels in human endothelial cells. Possible involvement of proto-oncogenes c-jun and c-fos.
Authors: Kooistra T , Bosma P J , Toet K , Cohen L H , Griffioen M , van den Berg E , le Clercq L , van Hinsbergh V W
Published: June 2011

Activation of protein kinase C leads to a strong induction of tissue-type plasminogen activator (t-PA) expression in endothelial cells. Using endothelial cells from human umbilical vein (HUVECs) and human aorta (HAECs), we have studied this regulation of t-PA and its inhibitor, plasminogen activator inhibitor-1 (PAI-1), at the mRNA level and have compared their induction with the expression of platelet-derived growth factors A and B (PDGF-A and PDGF-B) and the proto-oncogenes c-jun and c-fos. Treatment of HUVECs with exogenous bacterial phospholipase C or the synthetic diacylglycerol 1-oleoyl-2-acetylglycerol led to a threefold and a twofold increase, respectively, in t-PA concentrations in 24-hour-conditioned medium. Similarly, the more stable protein kinase C activator 4 beta-phorbol-12-myristate-13-acetate (PMA) caused about a 10-fold increase in t-PA antigen levels. This effect of PMA is maximal between 8 and 16 hours at a concentration of 10 nM and is fully accounted for by parallel increases in t-PA mRNA levels. An increase in intracellular cyclic adenosine monophosphate levels by forskolin (10 microM) slightly diminished t-PA expression but further enhanced the PMA-induced increases in t-PA synthesis and mRNA levels by at least twofold. PMA also enhanced the mRNA levels of two other important endothelium-expressed genes, PDGF-A and PDGF-B, with a time profile similar to that of t-PA, with peak values about fivefold higher than control values. Forskolin did not further stimulate this PMA-induced PDGF expression in HUVECs, which suggests a regulatory mechanism different from that of t-PA. Qualitatively very similar induction patterns of t-PA, PDGF-A, and PDGF-B were seen with HAECs. In contrast to t-PA and PDGF, PAI-1 mRNA and antigen levels increased only slightly after PMA treatment of HUVECs or HAECs; forskolin alone or in combination with PMA diminished the expression of PAI-1. The induction of t-PA mRNA by PMA was dependent on protein synthesis and was preceded by a strong transient increase in c-jun and c-fos mRNA levels; the induction of c-fos but not of c-jun was potentiated by forskolin. Because the products of these two proto-oncogenes form dimeric complexes for which specific binding sites are present in the t-PA promoter region, they may mediate the protein kinase C-dependent increase in t-PA gene expression, including the stimulating action of cyclic adenosine monophosphate.
Relations of body habitus, fitness level, and cardiovascular risk factors including lipoproteins and apolipoproteins in a rural and urban Costa Rican population.
Authors: Campos H , Bailey S M , Gussak L S , Siles X , Ordovas J M , Schaefer E J
Published: June 2011

Increased general and abdominal obesity has been independently associated with diabetes, increased risk of stroke, and coronary artery disease (CAD). It is more prevalent in developed countries and in urban areas of nonindustrialized nations than in less developed and rural areas. To evaluate the associations between general and abdominal obesity (as determined by total body fat, waist to hip ratio, umbilical to triceps ratio, and umbilical to subscapular ratio) with glucose, plasma lipoproteins, apolipoprotein (apo) A-I and B concentrations, and low density lipoprotein (LDL) particle size (LDL 1-7), we randomly selected 222 men and 243 women from rural and urban areas of Puriscal, Costa Rica. Abdominal obesity, as assessed by the waist to hip ratio, was independently and significantly associated with higher triglyceride levels (p less than 0.01) and with lower high density lipoprotein cholesterol levels (p less than 0.05) in men and women and with higher glucose levels (p less than 0.05) and smaller LDL particle size (p less than 0.01) in women. Abdominal obesity, as assessed by the umbilical to subscapular ratio, was independently and significantly associated with higher total cholesterol (p less than 0.005) and apo B (p less than 0.01) levels. Umbilical to triceps ratio was positively associated with blood pressure in men. Urban men had increased general and abdominal obesity (p less than 0.0001), number of cigarettes smoked per day (p less than 0.0001), and diastolic blood pressure (p less than 0.05) and had a decreased fitness level (p less than 0.0001) as well as higher (p less than 0.05) plasma glucose, triglyceride, and total cholesterol concentrations and lower (p less than 0.05) apo A-I and HDL cholesterol levels compared with rural men. The differences between rural and urban women were not as striking. Urban women had increased general and abdominal obesity, glucose, and apo B levels (p less than 0.05) and a decreased fitness level (p less than 0.0001). Our data indicate that general and abdominal obesity, increased cigarette smoking, diastolic blood pressure, and decreased fitness level are more prevalent in an urban than in a rural area in Costa Rica, particularly in men. The higher prevalence of such risk factors in the urban area is associated with a more atherogenic plasma lipoprotein profile.
Modulation of extracellular matrix proteins by endothelial cells undergoing angiogenesis in vitro.
Authors: Iruela-Arispe M L , Diglio C A , Sage E H
Published: June 2011

Angiogenesis results in part from the response of endothelial cells to the integrated action of morphogenic factors and extracellular matrix proteins. In this study we identified specific components of the extracellular matrix that were modulated in endothelial cells derived from bovine aorta and rat cerebral microvessels, both of which spontaneously form cords and tubes under standard culture conditions. SPARC (secreted protein, acidic and rich in cysteine) was upregulated 4.2-fold in aortic and 10-fold in microvascular cultures that had organized into cords and/or tubes. This Ca(2+)-binding glycoprotein was synthesized primarily by endothelial cells in the process of cord formation. Transcription of type I collagen was initiated in aortic endothelial cells undergoing angiogenesis in vitro and showed a 12-fold increase in similar cultures of microvascular cells. Type VIII collagen protein was upregulated to a lesser degree (4.3-fold in aortic and 1.8-fold in microvascular cells). Dense cytoplasmic staining for these two collagen types was seen in cells directly participating in the organization of cords. In contrast, the disparate levels of fibronectin observed in both types of endothelium indicated an indirect or secondary role for this glycoprotein in cord/tube formation in vitro. These results identify SPARC, type I collagen, and type VIII collagen as extracellular matrix components that are actively synthesized by endothelial cells undergoing angiogenesis in vitro. Moreover, expression of these proteins during the formation of tubes and cords appears to follow a biosynthetic program that is common to endothelial cells from both the macrovasculature and microvasculature.
Genetic and environmental contributions to cholesterol and its subfractions in 11-year-old twins. The Medical College of Virginia Twin Study.
Authors: Bodurtha J N , Chen C W , Mosteller M , Nance W E , Schieken R M , Segrest J
Published: June 2011

We conducted a cross-sectional analysis of the genetic and environmental contributions to the variance of lipoprotein cholesterol and its subfractions in children during early adolescence. Univariate path analysis was used to determine the relative contributions of genes, individual environment, and family environment to these measures in 233 11-year-old Caucasian twin pairs. For high density lipoprotein, high density lipoprotein2, low density lipoprotein, very low density lipoprotein, and triglycerides, a model that incorporated genes and individual environmental variation but not common environment was sufficient to explain the variation. Different magnitudes of genetic effects were seen for total cholesterol in boys and girls. High density lipoprotein3 showed different magnitudes by sex for genetic and individual environmental effect. Intermediate density lipoprotein was the only cholesterol subfraction in which shared, or common, environment was found to make a statistically significant contribution to the variation.
Fish oil supplementation reduces beta-very low density lipoprotein in type III dysbetalipoproteinemia.
Authors: Dallongeville J , Boulet L , Davignon J , Lussier-Cacan S
Published: June 2011

beta-Very low density lipoproteins (beta-VLDLs) are atherogenic, cholesterol-rich chylomicron and VLDL remnants that accumulate in the plasma of type III dysbetalipoproteinemic subjects. To evaluate the effect of fish oil supplementation on plasma beta-VLDL concentrations, we compared the lipid and lipoprotein responses in nine type III and nine type IV hyperlipidemic subjects. Each individual received 6 g/day omega-3 fatty acids for 12 weeks. Before treatment, the mean total cholesterol, total triglyceride, VLDL triglyceride, low density lipoprotein (LDL) cholesterol, and high density lipoprotein (HDL) cholesterol levels were not different between groups. Conversely, VLDL cholesterol, intermediate density lipoprotein (IDL) cholesterol, and IDL triglycerides were higher in type III than in type IV subjects. Fish oil supplementation was associated with significantly lower levels of cholesterol (-50%), triglycerides (-50%), and apolipoprotein B (-50%) in the d less than 1.006 g/ml ultracentrifugation plasma fraction in both groups, compatible with a reduction in VLDL in type III and type IV subjects, and in beta-VLDL in type III subjects. This finding was confirmed by analysis of the plasma zonal ultracentrifugation profile and the agarose gel electrophoretic pattern of lipoproteins, which showed a reduction in but not a disappearance of remnant particles, suggesting that not all beta-VLDL had been cleared after treatment. The levels of IDL cholesterol and IDL triglycerides (1.006 less than d less than 1.019 g/ml) were not affected in either group. Initially low LDL cholesterol (1.019 less than d less than 1.063 g/ml) and HDL cholesterol levels rose significantly in both groups. In type III hyperlipidemics, all LDL cholesterol values remained below 120 mg/dl, whereas they were higher than 150 mg/dl after treatment in two individuals with type IV hyperlipidemia.(ABSTRACT TRUNCATED AT 250 WORDS)
Activation of calpain I and hydrolysis of calpain substrates (actin-binding protein, glycoprotein Ib, and talin) are not a function of thrombin-induced platelet aggregation.
Authors: Wencel-Drake J D , Okita J R , Annis D S , Kunicki T J
Published: June 2011

Calcium-activated neutral proteinase (calpain) has been shown to cleave proteins involved in the maintenance of cell structure. In human platelets, substrates of calpain include glycoprotein Ib (GPIb), actin-binding protein (ABP), and talin. GPIb-ABP complexes can be isolated in detergent extracts and are thought to represent membrane-cytoskeleton attachment sites. It has been hypothesized that the hydrolysis of GPIb-ABP by calpain is regulated by the extent of binding of this proteinase to the plasma membrane-cytoskeleton interface with platelet activation. Recently, another calpain substrate (talin) has been shown to redistribute from the cytoplasm to the plasma membrane-cytoskeleton interface as the result of thrombin stimulation. To investigate the intracellular distribution of calpain I, we employed the monoclonal antibody B27D8, specific for the heavy chain (catalytic subunit) of calpain I. Indirect immunofluorescent staining of resting human platelets revealed undetectable surface antigen. Permeabilization with Triton X-100, however, revealed a diffuse intracellular antigen consistent with a cytosolic distribution. To determine whether this antigen distribution reflected the proenzyme or the activated form of calpain I and to assess the degree of hydrolysis of ABP, GPIb, and talin, we employed B27D8 and murine monoclonal antibodies against ABP (1B3 and 3D1), GPIb (LJIb10), and rabbit polyclonal antibodies against talin (A2 and B11) in a quantitative immunotransblot assay. Examination of resting platelets revealed that calpain I existed as the 85-kd proenzyme form and that ABP, GPIb, and talin existed in their native intact forms. When platelets were aggregated with thrombin, autoproteolysis of calpain I occurred within the 30 seconds required to completely solubilize platelet aggregates in sodium dodecyl sulfate-containing buffer and not as a direct result of thrombin-induced activation.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of exercise training on cardiovascular function and plasma lipid, lipoprotein, and apolipoprotein concentrations in premenopausal and postmenopausal women.
Authors: Blumenthal J A , Matthews K , Fredrikson M , Rifai N , Schniebolk S , German D , Steege J , Rodin J
Published: June 2011

This study examined the effects of aerobic exercise on lipid levels in premenopausal and postmenopausal women. Fifty healthy middle-aged women (mean age, 50 years) were randomly assigned to 12 weeks of either aerobic exercise (walking and jogging) or nonaerobic strength exercise (circuit Nautilus training). Concentrations of total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, and very low density lipoprotein cholesterol were assessed, along with apolipoprotein (apo) A-I, apo A-II, apo B, and triglycerides. To document changes in aerobic capacity, maximum treadmill testing was performed with expired-gas analysis before and after the exercise program. Aerobic exercise was associated with an 18% improvement in peak VO2. Women in the aerobic group had an increased VO2, from 26.7 to 31.4 ml/kg/min (p less than 0.0001), while the VO2 of the women in the strength training group did not change (25.8 ml/kg/min before and after). There were no differential changes in lipid levels because all subjects experienced slight reductions in high density lipoprotein cholesterol and total cholesterol and increases in apo A-I and the apo A-I to apo B ratio. There was a tendency for the aerobic group to exhibit lower levels of apo A-II and a greater apo A-I to apo A-II ratio, however. We conclude that premenopausal and postmenopausal women experience similar changes in aerobic capacity and lipid levels with exercise and that the short-term effects of aerobic and nonaerobic exercise on lipid profiles are generally comparable.
Mechanisms of hypertriglyceridemia in the coconut oil/cholesterol-fed rabbit. Increased secretion and decreased catabolism of very low density lipoprotein.
Authors: Van Heek M , Zilversmit D B
Published: June 2011

Rabbits fed a 14% coconut oil/0.5% cholesterol (CNO/Chol) diet develop mild to severe hypertriglyceridemia compared with rabbits fed a 14% olive oil/0.5% cholesterol (OO/Chol) diet. Lipids and apolipoprotein (apo) B were significantly higher in the very low density lipoprotein (VLDL) and intermediate density lipoprotein fractions from CNO/Chol than from OO/Chol rabbits. Yet, the particle diameters of these lipoproteins were similar in both diet groups, indicating that CNO/Chol rabbits had a much larger number of VLDL and intermediate density lipoprotein particles in plasma. Although the composition of CNO/Chol VLDL differed from that of OO/Chol VLDL, the rates of triglyceride hydrolysis of CNO/Chol VLDL and OO/Chol VLDL by postheparin lipoprotein lipase in vitro were the same, suggesting that VLDLs from the two diet groups were equally good substrates for lipoprotein lipase. To determine the mechanisms of hypertriglyceridemia in the CNO/Chol rabbit, triglyceride and apo B of CNO/Chol VLDL and OO/Chol VLDL were labeled with tritium-containing triolein and iodine-131 and injected intravenously into CNO/Chol and OO/Chol rabbits. The fractional clearance rate for triglyceride in OO/Chol rabbits was twice that of CNO/Chol rabbits, which parallels the previously observed differences in postheparin lipoprotein lipase activity. Although the average fractional removal of apo B did not differ between diet groups, there was a significant inverse relation between plasma cholesterol and apo B fractional clearance rate. We conclude that the hypertriglyceridemia and the enhanced hypercholesterolemia in the CNO/Chol rabbit results primarily from increased hepatic secretion of VLDL and a modest decrease in VLDL triglyceride clearance capacity.
Prevalence of familial hyperhomocyst(e)inemia in men with premature coronary artery disease.
Authors: Genest J J , McNamara J R , Upson B , Salem D N , Ordovas J M , Schaefer E J , Malinow M R
Published: June 2011

Elevated plasma levels of homocyst(e)ine have been reported to be more prevalent in patients with coronary artery disease (CAD) than in controls. The purpose of this study was to determine whether this elevation was genetic. We determined homocyst(e)ine levels in 176 men with premature CAD (greater than 50% stenosis of a major epicardial coronary artery occurring before the age of 60 years) and in 255 controls free of cardiovascular disease. Homocyst(e)ine levels were higher in the CAD group compared with controls (13.9 +/- 6.7 versus 10.9 +/- 4.9 nmol/ml, p less than 0.001); in addition, 28% of CAD patients had homocyst(e)ine levels above the 90th percentile of controls. Statistical analysis revealed that homocyst(e)ine levels were not related to the presence of hypertension or diabetes, smoking, or plasma levels of lipoprotein cholesterol and apolipoproteins A-I and B. The families of 71 CAD patients were sampled (selected on the basis of availability of relatives) and included 60 spouses and 239 first-degree relatives; 370 subjects were thus sampled. Spearman correlations between probands and spouses (r = 0.264, p = 0.041) and between mean values for parent and offspring (r = 0.356, p = 0.002) for homocyst(e)ine levels indicated that homocyst(e)ine levels are in part genetically determined. In 20 families (28.2%), the proband had homocyst(e)ine levels greater than the 90th percentile; familial segregation was observed in 10 of these kindreds. Therefore, 14% of CAD patients had familial hyperhomocyst(e)inemia. In conclusion, our data suggest that plasma homocyst(e)ine is a risk factor for the development of CAD, independent of other cardiovascular risk factors, and that this elevation is in part genetically determined.
Changes in vasoconstrictor and vasodilator responses of the basilar artery during maturation in the Watanabe heritable hyperlipidemic rabbit differ from those in the New Zealand White rabbit.
Authors: Stewart-Lee A L , Burnstock G
Published: June 2011

This investigation involved alterations in the local control of vascular tone in the isolated rabbit basilar artery in atherosclerosis, with Watanabe heritable hyperlipidemic (WHHL) rabbits as a model and New Zealand White (NZW) rabbits as controls. Vasoconstrictor responses to KCl in isolated preparations of the basilar artery at basal tone showed no differences at 4, 6, and 12 months of age in either WHHL or NZW rabbits. Contractile responses to both histamine and neuropeptide Y were significantly greater in 12-month-old WHHL rabbit preparations when compared with responses measured at 4 and 6 months. In NZW rabbit preparations, there was no change in maximum contractile responses to both histamine and neuropeptide Y over the same age range. Endothelium-dependent relaxations to acetylcholine in raised-tone preparations from WHHL rabbits were significantly greater at 6 months in comparison with responses measured at both 4 and 12 months of age. In contrast, endothelium-independent relaxations to calcitonin gene-related peptide and vasoactive intestinal polypeptide showed no change over the age range studied. In NZW rabbit preparations, both endothelium-dependent and endothelium-independent relaxations declined significantly between 4 and 12 months. The significance of these changes in the rabbit basilar artery in atherosclerosis is discussed in relation to the "protection" of intracranial arteries from atherosclerosis and their subsequent susceptibility to cerebral ischemia and stroke.
Native low density lipoprotein. Endothelial cell recruitment of mononuclear cells.
Authors: Pritchard K A , Tota R R , Lin J H , Danishefsky K J , Kurilla B A , Holland J A , Stemerman M B
Published: June 2011

The effect of native low density lipoprotein (LDL) on human umbilical vein endothelial cell (EC) recruitment of mononuclear cells (Monos) was investigated. ECs were exposed to LDL at atherogenic concentrations (240 mg cholesterol [Chol]/dl) for as long as 4 days (LDL-treated ECs). LDL-treated ECs bound substantially greater amounts of freshly isolated human monocytes and U937 cells than did control ECs. The enhanced Mono binding was time and LDL concentration dependent. LDL-induced binding was reduced to control levels when cycloheximide was added together with LDL, indicating that de novo protein synthesis was required. Furthermore, this LDL effect was not a general feature of apolipoproteins, as high density lipoprotein in physiologically relevant concentrations (45 mg Chol/dl, 4 days) had no effect on EC-Mono binding. Conditioned media from LDL-treated EC cultures did not increase EC binding of Monos. In contrast, minimally modified LDL increased EC-Mono binding more than eightfold. In conclusion, LDL in concentrations associated with the premature development of atherosclerosis increased EC affinity for Monos. Such LDL-induced alterations in EC physiology likely represent a proinflammatory response and an early step in atherogenesis.
Effect of aspirin and epinephrine on experimentally induced thrombogenesis in dogs. A parallelism between in vivo and ex vivo thrombosis models.
Authors: Roux S P , Sakariassen K S , Turitto V T , Baumgartner H R
Published: June 2011

Thrombosis on the damaged or ruptured vascular wall in a stenotic coronary artery is believed to be the precipitating factor leading to unstable angina. Little is known about the nature of the interactions among platelets, fluid dynamic factors, and vessel wall properties under such conditions. In the present investigation we have compared two experimental models of thrombosis simultaneously in anesthetized dogs. The first was an in vivo model of unstable angina, in which a fixed circumflex coronary artery stenosis was produced and the resultant cyclic blood flow reductions (CFRs) through the vessel were investigated after infusion of aspirin and a combination of aspirin and epinephrine. As previously reported, aspirin inhibited the CFRs, but the continuous infusion of epinephrine reestablished the appearance of CFRs. The second was an ex vivo model, in which thrombus formation on a type III collagen surface was investigated in a parallel-plate perfusion system under controlled conditions of exposure time and flow; morphological evaluation of thrombus volume, platelet adhesion, and fibrin deposition was performed. The chamber was positioned in an extracorporeal shunt between the carotid artery and the jugular vein of anesthetized dogs and exposed to nonanticoagulated blood at a shear rate of 1,600 sec-1. Thirty minutes after establishment of the CFRs, a blood sample for platelet aggregation was collected and a bleeding time and a first ex vivo perfusion were performed. At the end of this perfusion, animals were subjected either to no treatment (n = 10) or to an intravenous bolus of 10 mg/kg aspirin (n = 7), and a second perfusion was conducted 30 minutes later. Additional untreated animals (n = 6) were given aspirin followed by a continuous intravenous infusion of 10 micrograms/ml epinephrine, and a third perfusion was conducted. Results with respect to platelet adhesion, thrombus volume, and fibrin deposition were similar in the two perfusions in untreated animals. Treatment with aspirin abolished the CFRs in all dogs and concomitantly reduced the ex vivo thrombus volume by 84% (p less than 0.01) without affecting platelet adhesion and fibrin deposition. Bleeding time increased by 40% (p less than 0.05), and collagen-induced platelet aggregation was virtually abolished (p less than 0.01). However, infusion of epinephrine in dogs after aspirin treatment restored the CFRs, and the ex vivo thrombus volumes were not statistically different from predrug values. Thus, the ex vivo model satisfactorily reflects the more complicated in vivo model events with respect to intracoronary thrombosis and substantiates the view that aspirin interrupts coronary thrombogenesis in the dog by interfering with platelet cohesion.
Local modulation of intracellular calcium levels near a single-cell wound in human endothelial monolayers.
Authors: Drumheller P D , Hubbell J A
Published: June 2011

An endothelial cell monolayer with a single mechanically lysed cell was used as a model to examine the extent, kinetics, and nature of local calcium mobilization in the neighborhood of a wound. Individual endothelial cells from confluent monolayers were mechanically lysed with a minutien needle coupled to a micromanipulator while producing no observable mechanical trauma to the neighboring cells. Changes in calcium levels in individual cells surrounding the wound site were monitored by epifluorescence microphotometry with the calcium-sensitive fluorophore indo-1. Individual cells adjacent to the wound site showed a substantial increase in their intracellular calcium levels, almost as high as the calcium levels attained by ionophore controls. The magnitude of intracellular calcium mobilization in confluent monolayers decreased with distance from the wound site, and those cells located at a radius greater than seven cells from the wound site showed no change in their calcium levels. Thus, lysis of a single cell resulted in calcium mobilization in approximately 200 neighboring cells. The time necessary for intracellular calcium to reach maximum levels also increased with distance from the wound site. Calcium mobilization was partly intracellular and was inhibited by disrupting cell-cell coupling or by increasing gap junction resistance by heptanol. This mobilization was greatly attenuated in subconfluent endothelial monolayers, and it was not observed in fibroblasts or smooth muscle cells; furthermore, the effect was defective in monolayers intentionally contaminated with smooth muscle cells. This study examines the extent and possible mechanisms of local endothelial activation near a microscopic endothelial wound.
Effects of three genetic loci in a pedigree with multiple lipoprotein phenotypes.
Authors: Emi M , Hegele R M , Hopkins P N , Wu L L , Plaetke R , Williams R R , Lalouel J M
Published: June 2011

In the course of familial investigations of coronary artery disease, we identified an extended kinship in which several members were affected with type IIa hyperlipoproteinemia (HLPIIa), type III dyslipoproteinemia (DLPIII), or hypobetalipoproteinemia (HBLP). To study the genetic defects responsible for plasma lipoprotein abnormalities in this pedigree and to investigate the phenotypic effect of different genotypic combinations, we used molecular markers for apolipoprotein (apo) B, apo E, and the low density lipoprotein (LDL) receptor to characterize segregation at each locus. Linkage analysis showed that elevated LDL cholesterol levels and the HBLP phenotype were due to defects at the LDL receptor and the apo B loci, respectively. One pedigree member, who inherited both an LDL receptor allele linked with elevated LDL cholesterol levels and an apo B allele linked with HBLP, had a normal lipoprotein phenotype. Seven patients who simultaneously inherited the defective LDL receptor allele and one or two apo E2 alleles manifested DLPIII. The E2 alleles in this pedigree were shown by DNA sequence analysis to be the common E2 158 (arginine----cysteine) allele. These findings suggested a possible interaction between the abnormal LDL receptor and apo E2 alleles, resulting in the expression of DLPIII in the presence of a single copy of ago E2.
Serum low density lipoprotein cholesterol level and cholesterol absorption efficiency are influenced by apolipoprotein B and E polymorphism and by the FH-Helsinki mutation of the low density lipoprotein receptor gene in familial hypercholesterolemia.
Authors: Gylling H , Aalto-Setälä K , Kontula K , Miettinen T A
Published: June 2011

The aim of the present study was to evaluate the effect of variation of different gene loci separately and in concert on lipid metabolism in heterozygous familial hypercholesterolemia (FH). We assayed a unique low density lipoprotein (LDL) receptor gene defect (designated as FH-Helsinki), the XbaI polymorphism of the apolipoprotein (apo) B, phenotypes of the apo E, and determined the levels of serum lipoproteins, the efficiency of cholesterol absorption, and the values for several parameters of cholesterol metabolism in 51 unrelated patients with heterozygous FH. The genetic parameters were distributed independently of each other. Gender distribution and the prevalence of coronary artery disease were similar in the different apo E phenotypes, in the apo B genotypes, and in patients with and without the FH-Helsinki mutation. However, the FH-Helsinki mutation was associated with an increased body mass index. Serum LDL cholesterol was significantly elevated in patients with the FH-Helsinki mutation and the apo B X2 allele. Apo E phenotypes were not related to serum lipids per se, but the highest serum LDL cholesterol levels were measured in patients with the FH-Helsinki gene, apo E4 phenotype, and at least one X2 allele. Patients with the FH-Helsinki mutation and apo E4 phenotype had the highest cholesterol absorption efficiency. Cholesterol absorption was not related to serum lipids or lipoproteins, but LDL cholesterol was most elevated in patients with the most efficient cholesterol absorption. We conclude that in FH, diverse genetic factors exert individual and additive influences on serum LDL cholesterol levels.
George Lyman Duff Memorial Lecture. Multifactorial etiology of hypercholesterolemia. Implications for prevention of coronary heart disease.
Authors: Grundy S M
Published: June 2011

This review underlines the concept that multiple factors are responsible for hypercholesterolemia in the American public. Dietary factors (cholesterol, saturated fatty acids, and obesity) clearly raise the cholesterol level, and they are important causes of borderline-high cholesterol. Still, the unexplained decline of LDL receptor activity with aging contributes importantly to borderline-high levels and cannot be ignored. The loss of estrogen-stimulated LDL receptor synthesis after menopause is an important contributor to elevated cholesterol in postmenopausal women. In addition, several genetic defects inherited singly appear to be responsible for moderate hypercholesterolemia. Some of these defects may represent genetic hypersensitivity to diet, and dietary therapy alone may provide adequate cholesterol lowering. Other defects impart resistance to dietary control, and use of a single cholesterol-lowering drug may be required. With the exception of heterozygous FH, most cases of severe hypercholesterolemia appear to be the result of the coexistence of at least two defects in LDL metabolism, and as a rule, they can be treated successfully only by using cholesterol-lowering drugs in combination.
Phagocytosis of lipase-aggregated low density lipoprotein promotes macrophage foam cell formation. Sequential morphological and biochemical events.
Authors: Heinecke J W , Suits A G , Aviram M , Chait A
Published: June 2011

Macrophages internalize aggregated low density lipoprotein (LDL) by LDL receptor-dependent phagocytosis. To investigate this model of foam cell formation, we have used human and mouse macrophages to characterize biochemically and morphologically the fate of ingested phospholipase C-modified low density lipoprotein (PLC-LDL). When LDL was digested with phospholipase C, it lost phospholipid and aggregated. Human monocyte-derived macrophages rapidly ingested and degraded 125I-PLC-LDL. The degraded PLC-LDL released free cholesterol, measured either as free sterol mass or by the stimulation of [14C]oleate incorporation into cellular cholesteryl ester. Esterification was blocked by chloroquine, a weak base that inhibits lysosomal degradation. Macrophages exposed to PLC-LDL exhibited a 30-fold to a 50-fold increase in esterified sterol: by light microscopy, cytoplasmic inclusions were abundant. The inclusions were stained with oil red O, indicating that they were neutral lipid droplets. By electron microscopy, mouse peritoneal macrophages incubated with PLC-LDL contained numerous membrane-bounded vacuoles and cytoplasmic inclusions that were not surrounded by a limiting membrane. Pulse-chase experiments demonstrated that vacuoles filled with particulate material appeared first. Subsequently, the macrophages exhibited vacuoles containing multivesicular bodies. Last, inclusions that were homogeneously electron-dense and that lacked a tripartite membrane accumulated in the cytoplasm of the cells. These results are consonant with the following model of foam cell formation. Cultured macrophages rapidly ingest PLC-LDL that is initially localized in phagosomes. The aggregated lipoprotein subsequently is digested in secondary lysosomes, thus releasing free cholesterol that is reesterified, forming cytoplasmic cholesteryl ester droplets lacking a tripartite membrane.
The effect of fasting triacylglyceride concentration and apolipoprotein E polymorphism on postprandial lipemia.
Authors: Brown A J , Roberts D C
Published: June 2011

To determine if apolipoprotein (apo) E polymorphism influences postprandial lipemia and hence can help explain the wide range of lipemic responses to a standardized fat meal observed previously, blood samples were collected from 25 healthy men whose postprandial responses to a standardized fat meal had been measured. Venous blood samples had been obtained before the fat meal (0.73 g fat/kg containing vitamin A) and hourly thereafter for 8 hours, plasma and chylomicron triacylglyceride (TAG) concentrations had been determined, and retinyl esters (REs) in the chylomicron and nonchylomicron fractions had been measured. The original results were reanalyzed by apo E phenotype (six E2/3; 14 E3/3; four E3/4 and one E4/4, grouped as E4). Contrary to what is known about the epsilon 4 allele, the apo E4 group displayed a significantly greater response curve than did either the apo E2/3 or E3/3 groups for both plasma TAG and chylomicron RE concentrations (p less than 0.01), as reflected in a later chylomicron RE peak for the apo E4 group (p less than 0.05). The E4 group tended (p = 0.18) to have a 40% higher fasting TAG than did either of the other groups, which may reflect bias in the selection of subjects. As fasting TAG is an important determinant in postprandial lipemia, results were normalized for this variable. After adjustment, the E4 group had the lowest TAG response relative to the E3/3 group (p less than 0.01). Our findings suggest that controlling for apo E phenotype may help to reduce interindividual variation in the postprandial response to a standard fat meal.(ABSTRACT TRUNCATED AT 250 WORDS)
Lipid accumulation in rabbit aortic intima 2 hours after bolus infusion of low density lipoprotein. A deep-etch and immunolocalization study of ultrarapidly frozen tissue.
Authors: Nievelstein P F , Fogelman A M , Mottino G , Frank J S
Published: June 2011

The intima from aortas of normal New Zealand White rabbits was studied 2 hours after infusion of 320 mg human low density lipoprotein (LDL), resulting in a plasma concentration of at least five times and maximally 20 times the values found in normal rabbit serum. The following techniques were used: 1) ultrarapid freezing without chemical fixation, followed by freeze-etching; 2) immunofluorescence microscopy; and 3) postembedding immunogold-labeling electron microscopy. In the latter two methods MB47, a murine monoclonal antibody against human apolipoprotein B, was used as the primary antibody. Control rabbits were infused with the same volume of buffer only. Rotary-shadowed replicas of samples from the LDL-injected rabbits showed the deposition of lipidlike particles in the subendothelial-intimal space that were the size of the injected LDL (23 nm). In focal areas of the intima, groups of 23-nm-sized lipidlike particles and larger lipidlike structures were found enmeshed in the extracellular matrix. Control replicas were essentially free of lipid deposition. Immunofluorescence microscopy of frozen aortic cross sections showed an overall increase in apolipoprotein B in the intima of the LDL-injected rabbits. The presence of apolipoprotein B in the intima was also confirmed by immunoelectron microscopy. These in vivo results show that clustering of LDL-sized particles occurs in the intima within 2 hours of excessive LDL uptake. It also demonstrates the interaction of these LDL-sized particles with the filaments of the extracellular matrix. The clustering of the LDL-sized particles supports the possibility that LDL self-aggregation may occur in vivo and that components of the extracellular matrix are involved in this process.