bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of CI-976, an ACAT inhibitor, and selected lipid-lowering agents for antiatherosclerotic activity in iliac-femoral and thoracic aortic lesions. A biochemical, morphological, and morphometric evaluation.
Authors: Bocan T M , Mueller S B , Uhlendorf P D , Newton R S , Krause B R
Published: June 2011

Due to the potential importance of acyl-coenzyme A:cholesterol O-acyltransferase (ACAT) in the generation of lipid-filled monocytes-macrophages, the ACAT inhibitor CI-976 (2,2-dimethyl-N-(2,4,6-trimethoxyphenyl)dodecanamide) was evaluated relative to selected lipid-lowering agents for their effect on atherosclerotic lesion regression and progression. Atherosclerotic lesions comparable in composition to human fatty streaks were induced by chronic endothelial denudation in the iliac-femoral artery of hypercholesterolemic New Zealand White rabbits before intervention, while naturally occurring fatty streaks developed in the thoracic aorta. CI-976 administered in a hypercholesterolemic diet at a dose that did not lower plasma cholesterol prevented the accumulation of monocytes-macrophages within the preestablished iliac-femoral lesion and reduced the foam cell area by 27-29% relative to the initiation of intervention. CI-976 also blunted the development of thoracic aortic fatty streak-like lesions and decreased the cholesteryl ester enrichment by 46%. CI-976 had no effect on plasma triglycerides and, more importantly, had no effect or decreased liver, iliac-femoral, and thoracic aortic free cholesterol content. Dietary intervention alone increased monocyte-macrophage involvement in the iliac-femoral lesion despite reductions in plasma, liver, and thoracic aortic cholesterol content. Conventional lipid-lowering therapy such as cholestyramine or cholestyramine/niacin required substantial decreases in plasma cholesterol levels to achieve comparable vascular changes. We conclude that inhibition of ACAT within the arterial wall by the potent and specific ACAT inhibitor CI-976, even in the absence of plasma cholesterol lowering, can result in the inhibition of atherosclerotic lesion progression and can enhance regression.
Shear stress regulates smooth muscle proliferation and neointimal thickening in porous polytetrafluoroethylene grafts.
Authors: Kraiss L W , Kirkman T R , Kohler T R , Zierler B , Clowes A W
Published: June 2011

High shear stress appears to decrease wall thickening in diseased arteries and vascular grafts. To determine if increased shear stress diminishes smooth muscle (SMC) proliferation, we studied the effect of increased blood flow on neointimal thickening in porous polytetrafluoroethylene grafts implanted in baboons. An aorto-aortic 5-mm graft was placed in tandem with a pair of aorto-iliac 5-mm grafts, so that the proximal graft supplied all flow to both distal grafts. At 12 weeks, calculated luminal shear stress in proximal grafts was twice that in distal grafts (24 +/- 8 versus 11 +/- 5 dynes/cm2; p less than 0.05). All grafts were completely endothelialized. The neointimal cross-sectional area in proximal grafts was about half as large as in distal grafts (3.36 +/- 1.61 versus 5.93 +/- 0.61 mm2; p less than 0.05). Proximal grafts also had significantly less SMC proliferation (0.14 +/- 0.05% versus 0.24 +/- 0.10%; p less than 0.05) and SMC volume (6.1 +/- 4.0 versus 12.4 +/- 2.6 mm3/cm graft; p less than 0.01) when compared with distal grafts. We conclude that the elevation in shear stress in the proximal graft, which remained within the physiological range, inhibits SMC proliferation and neointimal thickening in these grafts.
Cholesterol and triglyceride fatty acid synthesis in apolipoprotein E2-associated hyperlipidemia.
Authors: Jones P J , Dendy S M , Frohlich J J , Leitch C A , Schoeller D A
Published: June 2011

To investigate whether increased endogenous lipogenesis contributes to elevated plasma lipid levels in individuals with apolipoprotein (apo) E2-associated hyperlipidemia (E2-HL), plasma pool cholesterol and triglyceride fatty acid syntheses were measured in subjects with E2-HL and in those with normal lipid levels. Subjects were given a priming dose of deuterium oxide (D2O) followed by maintenance doses over 48 hours. During the first 24 hours, subjects consumed prepared meals, whereas during the 24-48 hour interval, they consumed water only. Blood samples were drawn every 12 hours, and cholesterol and triglyceride fatty acid formation rates were determined from the change in deuterium enrichment. The free cholesterol fractional synthesis rate over 0-24 hours of E2-HL subjects (0.057 +/- 0.010 day-1, mean +/- SEM) was not significantly different from that of normolipidemics (0.075 +/- 0.005 day-1). Calculated cholesterol net synthesis was not different between the two groups (0.56 +/- 0.07 and 0.75 +/- 0.05 g/day, respectively). Mean free cholesterol synthesis for all subjects was higher in the fed (0-24 hour) compared with the fasted (24-48-hour) condition. Initial 12-hour triglyceride fatty acid fractional synthesis was significantly (p less than 0.01) increased in E2-HL subjects (0.143 +/- 0.012 day-1) compared with controls (0.082 +/- 0.0013 day-1). These findings suggest that in E2-HL, elevated plasma cholesterol levels are due to factors other than increased sterol synthesis, while higher de novo fatty acid synthesis contributes to the observed hypertriglyceridemia.
Lipoproteins and their genetic variation in subjects with and without angiographically verified coronary artery disease.
Authors: Nieminen M S , Mattila K J , Aalto-Setälä K , Kuusi T , Kontula K , Kauppinen-Mäkelin R , Ehnholm C , Jauhiainen M , Valle M , Taskinen M R
Published: June 2011

To examine the concentration of serum lipoproteins and the association of their genetic variation with the occurrence of coronary artery disease (CAD), composite serum lipoprotein profiles including lipoprotein(a) (Lp[a]), apolipoprotein (apo) E phenotypes, and apo B Xba I genotypes were determined in patients with angiographically verified CAD (CAD+ group, n = 111) and in subjects with no angiographic evidence of CAD (CAD- group, n = 46). In addition, we determined the concentrations of serum lipids, lipoproteins, and apolipoproteins in 96 healthy controls. Both CAD- and CAD+ groups had lower concentrations of apos A-I and A-II but higher concentrations of serum total and very low density lipoprotein triglyceride and very low density lipoprotein cholesterol than did healthy controls. The mean concentrations of serum total and low density lipoprotein cholesterol and the median values of Lp(a) were similar in the CAD+ and CAD- groups, both having higher concentrations of low density lipoprotein cholesterol and apo B than the healthy controls. Irrespective of gender, patients with CAD had significantly lower serum high density lipoprotein cholesterol than did those without CAD (1.48 +/- 0.40 versus 1.16 +/- 0.29 mmol/l, p less than 0.001). In women, the mean serum total and very low density lipoprotein triglyceride concentration was also higher in the CAD+ than in the CAD- group. The frequency of the apo E4 allele (epsilon 4) was significantly higher in the CAD+ group (0.293) than in the CAD- group (0.174; p less than 0.001). The frequencies of the two apo B alleles, X1 (Xba I restriction site absent) and X2 (Xba I restriction site present), were similar in the two groups. Stepwise discriminant analysis revealed that in men, serum high density lipoprotein cholesterol had the highest power to discriminate for CAD. In addition, the concentration of plasma apo B levels and the occurrence of apo E phenotypes were independently associated with CAD in men. In women, the only independent factor associated with CAD after adjustment for beta-blocker and diuretics usage was the concentration of serum triglycerides.
Arterial wall thickness in familial hypercholesterolemia. Ultrasound measurement of intima-media thickness in the common carotid artery.
Authors: Wendelhag I , Wiklund O , Wikstrand J
Published: June 2011

B-mode ultrasound was used to noninvasively determine wall thickness and lumen diameter in the common carotid artery in patients with familial hypercholesterolemia (n = 53) and in a control group (n = 53). The controls were matched for sex, age, height, and weight, and all had a serum cholesterol level below 6.5 mmol/l. The study was performed to evaluate whether the patients had a thicker arterial wall compared with that of the control group. Wall thickness was determined as the combined intima-media thickness of the far wall and is presented as the mean and maximum thickness of a 10-mm-long section of the common carotid artery. The difference between the groups was 0.13 mm in mean wall thickness (p less than 0.001; 95% confidence interval, 0.07-0.18 mm) and 0.20 mm in maximum wall thickness (p less than 0.001; 95% confidence interval, 0.09-0.23 mm). Fifty of the subjects were examined twice to estimate the interobserver variability. The coefficients of variation for mean and maximum wall thickness were 10.2% and 8.9%, respectively. The two study groups were well matched and differed only in lipid levels. Thus, there is reason to believe that the difference in wall thickness can be explained by the background of familial hypercholesterolemia and the increased cholesterol levels.
Glutathione-related enzyme activities and lipoperoxide levels in human internal mammary artery and ascending aorta. Relations with serum lipids.
Authors: Mezzetti A , Lapenna D , Calafiore A M , Proietti-Franceschilli G , Porreca E , De Cesare D , Neri M , Di Ilio C , Cuccurullo F
Published: June 2011

The relation among glutathione-related enzyme activities, thiobarbituric acid-reactive substances of the human aorta and internal mammary artery, and serum lipids was studied in 40 male patients undergoing coronary revascularization. Glutathione peroxidase and glutathione reductase activities were significantly higher in the internal mammary artery, whereas glutathione transferase activity was elevated in the aortic wall. Moreover, non-selenium-dependent glutathione peroxidase activity was detectable only in the aorta. The levels of thiobarbituric acid-reactive substances were significantly higher in the aorta. A positive correlation was found among the activity of glutathione peroxidase, glutathione reductase, and thiobarbituric acid-reactive substances in the internal mammary artery and total cholesterol, low density lipoprotein cholesterol, and triglycerides. In the aortic wall, a positive correlation among the activity of glutathione peroxidase, glutathione transferase, thiobarbituric acid-reactive substances, and the previously mentioned serum lipids was evident. In contrast, high density lipoprotein cholesterol was inversely related to enzymatic activities and thiobarbituric acid-reactive substances in both the internal mammary artery and aorta. In conclusion, significant differences in the levels of glutathione-related enzyme activities and thiobarbituric acid-reactive substances in the internal mammary artery and aorta were found, suggesting a different ability of the two tissues to counteract oxidative stress: the glutathione-related antioxidant properties and the level of lipid peroxidation in the arterial tissue seem to be specifically influenced by serum lipids.
Redirected targeting of LDL to human monocyte Fc gamma receptors with bispecific antibodies.
Authors: Morganelli P M , Kitzmiller T J , Hemmer R , Fanger M W
Published: June 2011

Recent studies indicate that low density lipoprotein (LDL)-immune complexes consisting of anti-LDL antibodies bound to LDL may contribute to macrophage foam cell development by uptake through immunoglobulin G (IgG) Fc receptors. As human mononuclear phagocytes possess three structurally and functionally distinct classes of IgG Fc receptors, we developed a system whereby the effects of LDL-immune complexes could be studied with respect to each type of IgG Fc receptor. Novel bispecific antibodies consisting of anti-Fc gamma receptor antibodies linked to anti-LDL antibodies were used to prepare bispecific LDL-immune complexes for targeting to specific Fc gamma receptors. In this report, the effects of bispecific LDL-immune complexes directed to Fc gamma receptor types I, II, and III were studied primarily with monocytes and were compared with the effects of similarly prepared bispecific complexes that targeted LDL to human leukocyte antigen (HLA) class I antigens. Each type of bispecific antibody was effective in targeting 125I-LDL to its respective site on the cell surface. Using fluorophore-labeled LDL and flow cytometry, bispecific complexes directed to Fc gamma receptor types I or II but not to HLA class I antigens caused a two- to sevenfold increase in cell-associated fluorescence relative to control cells treated with LDL in the absence of bispecific antibody. Uptake occurred in the presence of excess unlabeled LDL, acetylated LDL, and antioxidants. That the bispecific complexes triggered metabolic uptake was supported by studies of kinetics and temperature dependence. Using 125I-labeled complexes, metabolic degradation of LDL was demonstrated in association with each of the three types of Fc gamma receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
A monogalactosylated cholesterol derivative that specifically induces uptake of LDL by the liver.
Authors: Bijsterbosch M K , Bakkeren H F , Kempen H J , Roelen H C , van Boom J H , van Berkel T J
Published: June 2011

We described earlier the effect of tris-gal-chol (a triantennary galactose structure coupled to cholesterol) on the fate of low density lipoprotein (LDL) and high density lipoprotein (HDL). Tris-gal-chol-loaded LDL and HDL are both efficiently cleared from blood by hepatic galactose-specific receptors. Thus, tris-gal-chol combines a beneficial LDL-reducing effect with an equally effective but undesirable HDL-lowering effect. We recently synthesized a cholesterol derivative with a single terminal galactose residue, denoted mono-gal-chol. In the present study we show that this compound, which incorporates readily into both LDL and HDL, induces rapid association of LDL and HDL to the liver. The mono-gal-chol-stimulated hepatic association of HDL, however, was about fivefold lower than that of LDL. In the liver, Kupffer cells were mainly (90%) responsible for the liver uptake of mono-gal-chol-loaded LDL, whereas the complex of mono-gal-chol with HDL was predominantly (95%) taken up by parenchymal cells. Uptake by both cell types proceeded via galactose-specific receptors and was followed by degradation of the apolipoproteins in the lysosomes. Thus, compared with tris-gal-chol, mono-gal-chol is equally effective in the induction of galactose-specific uptake of LDL by Kupffer cells. However, the galactose-specific receptor on parenchymal cells recognizes mono-gal-chol-loaded HDL less efficiently than tris-gal-chol-containing HDL. These results indicate that mono-gal-chol might be used to specifically lower LDL levels in patients with a high LDL cholesterol level.
Further characterization of the acetyl LDL (scavenger) receptor expressed by rabbit smooth muscle cells and fibroblasts.
Authors: Pitas R E , Friera A , McGuire J , Dejager S
Published: June 2011

We have previously demonstrated that the acetyl low density lipoprotein (LDL), or scavenger, receptor is expressed by rabbit smooth muscle cells (SMCs) and fibroblasts. Moreover, receptor activity in rabbit fibroblasts was regulated over a wide range by preincubating the cells with secretion products from human platelets or with phorbol esters. The current studies were undertaken to examine the regulation of receptor expression in rabbit SMCs, to characterize further the receptor expressed by rabbit SMCs and fibroblasts, and to determine whether incubating these cells with chemically modified lipoproteins would lead to foam cell formation. Receptor activity was increased fivefold in rabbit SMCs by preincubation with platelet secretion products and nine- to 20-fold by preincubation with phorbol esters or mezerein, a non-phorbol activator of protein kinase C. The phorbol ester-induced increase in receptor activity was due to an increased mass of scavenger receptor as determined by both ligand blots and immunoblots of membrane proteins from these cells. The immunoblotting studies suggest that the SMC scavenger receptor activity is due to type I or type II scavenger receptors. The scavenger receptor expressed by phorbol ester-treated rabbit SMCs and fibroblasts bound chemically modified LDL with an order-of-magnitude higher affinity (Kd 5.1 x 10(-10) M) than did the scavenger receptor expressed by mouse peritoneal macrophages (Kd 4.1 x 10(-9) M), whereas rabbit macrophages bound chemically modified LDL with intermediate affinity (Kd 1.0 x 10(-9) M). Both the phorbol ester-stimulated rabbit fibroblasts and SMCs expressed 10-30% as many receptors per cell as did mouse peritoneal macrophages. Consistent with the difference in the number of receptors, uptake of the chemically modified LDL at 37 degrees C by SMCs led to approximately 25% as much lysosomal degradation and stimulation of cholesterol esterification as in mouse peritoneal macrophages. Incubation of phorbol ester-treated rabbit fibroblasts or SMCs with chemically modified LDL (50 micrograms/ml) for 24 or 48 hours, respectively, resulted in a threefold increase in total cholesterol and a 15-fold increase in cholesteryl ester within the cells. These studies suggest that the scavenger receptor-mediated uptake of modified lipoproteins may contribute to the formation of SMC foam cells in atherosclerotic lesions.
Time course and cellular characteristics of the iliac artery response to acute balloon injury. An angiographic, morphometric, and immunocytochemical analysis in the cholesterol-fed New Zealand white rabbit.
Authors: Stadius M L , Rowan R , Fleischhauer J F , Kernoff R , Billingham M , Gown A M
Published: June 2011

Evaluation of the response of the arterial vessel wall to acute arterial injury in experimental models has taken on substantial importance because of an increasing interest in angioplasty treatment of human atherosclerotic lesions. In this study, the response of normal arterial vessels to acute balloon injury was studied in 45 iliac artery segments from 24 New Zealand White rabbits fed a 2% cholesterol diet. At specified time points between 1 and 41 days after the initial balloon pullback injury, the iliac arteries were analyzed by angiographic, morphometric, and immunocytochemical techniques. Angiographic measurements indicated progressive compromise of the iliac artery lumen with increasing duration of time from injury. Morphometric measurements showed that intimal area increased from 0.004 +/- 0.01 mm2 3 days after injury to 1.15 +/- 0.30 mm2 34-41 days after injury. Cell line-specific immunocytochemical analysis identified the macrophage as a prominent component of the earliest intimal cellular infiltrate. Smooth muscle cells appeared within the intima 7-9 days after injury. As the intima increased in area, macrophages predominated along the internal elastic lamina aspect of the intimal lesion while smooth muscle cells occupied the portion of the intima adjacent to the lumen. In summary, retrograde balloon pullback injury followed by cholesterol feeding results in progressive arterial luminal narrowing due to a progressively enlarging intimal cellular infiltrate. The temporal and spatial contributions of smooth muscle cell and macrophage components of the developing intimal cellular infiltrate have been characterized.
Change in LDL particle size is associated with change in plasma triglyceride concentration.
Authors: McNamara J R , Jenner J L , Li Z , Wilson P W , Schaefer E J
Published: June 2011

Low density lipoprotein (LDL) particle size is inversely associated with plasma triglyceride concentration in cross-sectional analyses. In the present study, changes in the LDL particle size of 227 participants of the Framingham Offspring Study were analyzed longitudinally by nondenaturing gradient gel electrophoresis at two examinations that were separated by 3-4 years. All subjects had triglyceride concentrations < 400 mg/dl at both exams. Using laser scanning densitometry to assess mean LDL particle size, 56% of samples displayed a change in size: 41% had a one-band size change, 13% had a two-band change, and 2% had a three-band change. These changes in size corresponded to a 15% change in pattern type, based on pattern A and B terminology. There was a significant inverse association between change in LDL size and change in triglyceride (p < 0.0001) and glucose (p < 0.004) concentrations, body weight (p < 0.02), and age (p < 0.03). There was also a significant positive association with change in high density lipoprotein (HDL) cholesterol concentration (p < 0.0001). Change in LDL cholesterol concentration, as calculated by use of the Friedewald formula, however, showed no significant association with change in LDL size (p < 0.9). There was also no significant association with change in smoking or blood pressure, but there was a nonsignificant inverse trend associated with alcohol intake (p < 0.08).(ABSTRACT TRUNCATED AT 250 WORDS)
LDL binding sites on platelets differ from the "classical" receptor of nucleated cells.
Authors: Pedreño J , de Castellarnau C , Cullaré C , Sánchez J , Gómez-Gerique J , Ordóñez-Llanos J , González-Sastre F
Published: June 2011

Washed human platelets bound radioiodinated low density lipoprotein (125I-LDL) to a class of saturable binding sites; they numbered 1,348 +/- 126 per platelet, and the dissociation constant (KD) was 50.7 +/- 9 nM. 125I-LDL binding to platelets was reversible, and apparent equilibrium was attained within 25 minutes at 22 degrees C and was characterized by forward and reverse rate constants of 1.47 x 10(4) x sec-1 x M-1 and 8 x 10(-4) x sec-1 x M-1, respectively. Such binding was largely unaltered by temperature, divalent ions, and chelating agents. In addition, neither did receptor regulation (up or down) occur when platelets were loaded with cholesterol, nor did prostaglandin E1 (PGE1) increase the binding of 125I-LDL to platelets. On the other hand, the specificity of LDL binding was not typical of the LDL receptor of nucleated cells. Lipoproteins competed for the occupancy of LDL binding sites in platelets with the following order of potency: very low density > intermediate density > high density subfraction 2. High density lipoprotein subfraction 3, heparin, and PGE1 had no effect on this binding. 125I-LDL binding to lymphocytes and fibroblasts and proteolytic degradation of 125I-LDL by lymphocytes was inhibited by the monoclonal antibody IgG-C7 directed against the LDL receptor to 88%, 85%, and 85% (p < 0.001), respectively. However, with this monoclonal antibody, a blocking effect on neither 125I-LDL binding to platelets nor on LDL-enhanced platelet aggregation induced by ADP and collagen was found. Moreover, we confirmed the existence of LDL binding in platelets from patients with familial hypercholesterolemia. Our results indicate that human platelets bind LDL by saturable sites, which clearly differ from the "classical" LDL receptor in their binding properties, absence of receptor regulation, presence in platelets of familial hypercholesterolemia patients, and the lack of a blocking effect of IgG-C7 on LDL binding and LDL biological activity.
Thrombogenicity and procoagulant activity of human mesothelial cells.
Authors: Pronk A , de Groot P G , Hoynck van Papendrecht A A , Verbrugh H A , Leguit P , van Vroonhoven T J , Sixma J J
Published: June 2011

Cell seeding may decrease the thrombogenicity of implanted vascular grafts, but its application is hampered by the limited availability of autologous endothelial cells. We studied the interaction of alternate cells, human peritoneal mesothelial cells, with whole blood in a flow chamber. When citrated blood was perfused over mesothelial cells, platelet adhesion was seen on the intercellular matrix but not on the cells themselves. Perfusions with blood anticoagulated with low-molecular-weight heparin resulted in fibrin formation at the surface of mesothelial cells but not at the surface of human umbilical venous endothelial cells. At shear rates of 200 sec-1 fibrin deposition on the mesothelial cell surface increased during the first 5 minutes to 5.7 +/- 1.06 micrograms fibrin per square centimeter, whereafter these values stabilized. The procoagulant activity of cultured mesothelial cells was higher than that of peritoneal membrane studied ex vivo. However, cultured mesothelial cells incubated with polyclonal antibodies against tissue factor showed a significant decrease in procoagulant activity. We conclude that human peritoneal mesothelial cells may be used for cell seeding procedures, provided that their tissue factor expression can be controlled.
Activation of platelets in blood perfusing angioplasty-damaged coronary arteries. Flow cytometric detection.
Authors: Scharf R E , Tomer A , Marzec U M , Teirstein P S , Ruggeri Z M , Harker L A
Published: June 2011

Fluorescence-activated flow cytometry has been used to investigate platelet activation in blood flowing through atherosclerotic coronary arteries after sustaining mechanical damage induced by percutaneous transluminal angioplasty (PTCA). For flow cytometry, platelets and platelet-derived microparticles were identified by biotinylated anti-glycoprotein (GP) Ib monoclonal antibody (mAb) and a fluorophore, phycoerythrin-streptavidin. Activated platelets were detected by using a panel of fluoresceinated mAbs specific for activation-dependent platelet epitopes, including 1) activated GPIIb-IIIa complex (PAC1); 2) fibrinogen bound to platelet GPIIb-IIIa (9F9); 3) ligand-induced binding sites on GPIIIa (anti-LIBS1); and 4) P-selectin, an alpha-granule membrane protein expressed on the platelet surface after secretion (S12). The binding of antibodies to platelets was determined in blood that was sampled continuously via heparin-coated catheters from the coronary sinus in 1) patients before, during, and for 30 minutes after PTCA and 2) control patients undergoing coronary angiography without PTCA. Platelets in coronary sinus blood showed significant binding of mAbs that specifically detect activation epitopes associated with the GPIIb-IIIa complex (PAC1, anti-LIBS1, and 9F9) during and for 30 minutes after angioplasty in four of the five patients. The relative proportion of platelets positive for PAC1 and anti-LIBS1 increased from baseline values of 2.0 +/- 0.3% (mean +/- SD) and 2.0 +/- 0.5% to 18 +/- 14% and 28 +/- 14%, respectively, during PTCA or 30 minutes after PTCA (p < 0.01 in both cases). Binding with 9F9 was less prominent. The expression of P-selectin was detected in one of the five patients. By contrast, activation-specific mAbs failed to bind detectably with platelets obtained from 1) the peripheral blood during coronary angiography in eight patients or 2) coronary sinus blood obtained via catheter throughout control catheterization procedures in three patients or before PTCA in five. We conclude that circulating platelets become activated while flowing through PTCA-damaged stenotic coronary arteries and that this process of platelet activation is readily demonstrated by measuring the expression of activation-specific membrane GP epitopes by flow cytometric analysis.
Pituitary factors in blood plasma are necessary for smooth muscle cell proliferation in response to injury in vivo.
Authors: Fingerle J , Faulmüller A , Müller G , Bowen-Pope D F , Clowes M M , Reidy M A , Clowes A W
Published: June 2011

Intimal thickening in response to vascular injury is inhibited in animals previously subjected to hypophysectomy. We have investigated the nature and cell kinetics of this effect in a balloon catheter model of injury to the rat carotid artery. The ability of injury to stimulate [3H]thymidine labeling 48 hours after injury was almost completely eliminated in hypophysectomized (hypox) compared with control animals (0.1% versus 32.1%). Total DNA content of the developing neointima 14 days after injury was only 30% of the values found in ballooned carotid arteries of normal rats. If hypox rats were treated with recombinant human growth hormone, the proliferative response was not restored. There are two possible general explanations for the reduction of proliferative response in hypox animals: 1) that smooth muscle cells in the hypox animals have lost the ability to respond to the stimulus of injury or 2) that the ability of the smooth muscle cells to respond has not been reduced by prior hypophysectomy, but that the response itself requires the presence of pituitary-dependent factors. Transplantation experiments were performed in vivo to distinguish between these possibilities. Carotid arteries in inbred Lewis rats were excised 1 hour after balloon injury to give platelets the opportunity to adhere. These vessels were then transplanted from hypox into control animals and vice versa. At 48 hours, proliferation of smooth muscle cells in "control-to-hypox" transplants was 0.3% compared with 14.3% in "control-to-control" transplants, whereas vessels from hypox rats increased their indices to 4.8% if transplanted into control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Hedgehog lipoprotein(a) is a modulator of activation of plasminogen at the fibrin surface. An in vitro study.
Authors: Rouy D , Laplaud P M , Saboureau M , Anglés-Cano E
Published: June 2011

Lipoprotein(a) (Lp[a]), a highly atherogenic lipoprotein particle, is the prominent apolipoprotein B-containing lipoprotein in the hedgehog (Laplaud PM et al, J Lipid Res 1988;29:1157-1170). In the present work, we studied the consequences of the structural homology between the specific Lp(a) glycoprotein, apoprotein(a), and plasminogen on the generation of plasmin by fibrin-bound tissue-type plasminogen activator. The activation of plasminogen was initiated by adding either native plasma or Lp(a)-free plasma supplemented with the equivalent of 0.25 mg/ml of either purified Lp(a) or albumin to a surface of fibrin prepared on micortitration plates and to which human tissue-type plasminogen activator was specifically bound. With the Lp(a)-free plasma, an increase in the binding and activation of plasminogen as a function of time was observed. In contrast, in the presence of Lp(a) (i.e., native plasma or the reconstituted system), a significant decrease in the binding of plasmin(ogen) (approximately 60%) was obtained. These data indicate that hedgehog Lp(a) interferes with the binding and activation of plasminogen at the fibrin surface and may thereby behave as a factor regulating the extent of fibrin deposition. These results support our previous data indicating that high levels of Lp(a) may have antifibrinolytic effects in humans (Rouy D et al, Arterioscler Thromb 1991;11:629-638), are in agreement with the observation that Lp(a) is a risk factor for atherosclerotic disease, and provide further support to the view of Lp(a) as a link between atherosclerosis and thrombosis.
Inhibition of cyclic AMP- and cyclic GMP-mediated dilations in isolated arteries by oxidized low density lipoproteins.
Authors: Galle J , Bauersachs J , Busse R , Bassenge E
Published: June 2011

We studied the effects of native (N) and oxidized (Ox) low density lipoproteins (LDLs) on adenosine 3',5'-cyclic monophosphate (cAMP)-mediated and on guanosine 3',5'-cyclic monophosphate (cGMP)-mediated dilator mechanisms in isolated, perfused human mammary and rabbit femoral arteries. Dilations were induced in preconstricted, deendothelialized segments by either forskolin (Fo) or sodium nitroprusside (SNP) (intraluminal or adventitial application). Lipoproteins (0.5 mg/ml) were administered to the segments from the intraluminal side. N-LDL had no effect on Fo-induced dilation and caused a weak attenuation of SNP-induced dilation only when SNP was also administered into the intraluminal perfusate. In contrast, Ox-LDL inhibited both Fo- and SNP-induced dilation, independent of the route of dilator application. The effects of Ox-LDL were specific for dilation mediated by cyclic nucleotides. Dilation elicited by the Ca2+ antagonist nitrendipine was inhibited neither by N-LDL nor by Ox-LDL. Determination of basal and stimulated (SNP, Fo) cGMP and cAMP content in rabbit femoral segments after preincubation with N-LDL and Ox-LDL revealed a significant decrease of stimulated vascular cGMP and cAMP content by Ox-LDL, whereas N-LDL had no effect. These data indicate that Ox-LDL selectively inhibits vascular smooth muscle relaxation elicited by increases in cyclic nucleotides. This inhibition might contribute to the attenuation of vasodilation in hypercholesterolemia and atherosclerosis.
T lymphocytes in human atherosclerotic plaques are memory cells expressing CD45RO and the integrin VLA-1.
Authors: Stemme S , Holm J , Hansson G K
Published: June 2011

The cellular composition of human atherosclerotic plaques has been analyzed in several immunohistochemical studies in recent years. These studies have shown that the main cell types of the plaque are macrophages, smooth muscle cells, and T lymphocytes. To further characterize the T-lymphocyte population in atherosclerotic plaques, human plaque tissue was digested enzymatically and the released cells were labeled with fluorescent antibodies and analyzed by flow cytometry. Fifteen patients undergoing carotid endarterectomy were studied. Sixty-four percent of plaque T cells expressed the low-molecular-weight form (CD45RO) of the leukocyte common antigen (CD45). Many of these cells expressed the integrin very late activation antigen-1 (VLA-1), which suggests that they are in a state of late activation. In contrast, only 1% of peripheral blood T cells from the same patients expressed VLA-1. Other markers of T cell activation, such as Ta1 (CD26) and HLA-DR, were also increased on plaque T cells. The interleukin-2 receptor (CD25), which is transiently expressed after activation, was present on only a small proportion of the cells. Taken together, this analysis of plaque lymphocytes shows that the majority of plaque T cells are memory cells, many of which are in a state of late or chronic activation. This T-cell phenotype may be the result of a preferential recruitment and/or retention of activated peripheral blood T cells or local antigenic stimulation of resting T cells.
Antithrombotic efficacy of low-molecular-weight heparin in deep arterial injury.
Authors: Heras M , Chesebro J H , Webster M W , Mruk J S , Grill D E , Fuster V
Published: June 2011

Low-molecular-weight heparin subfractions more specifically inhibit factor Xa than thrombin, and they may have advantages over unfractionated heparin in arterial thrombosis. The antithrombotic efficacy of four dosages of a low-molecular-weight heparin (CY216 at 100, 200, 400, or 500 Institute Choay units/kg) was compared with unfractionated calcium heparin (100 US Pharmacopeia units/kg) and placebo during deep arterial injury produced by balloon dilatation of the carotid artery in the pig. The acute thrombotic end points were 111In-labeled platelet and 125I-labeled fibrinogen/fibrin deposition and macroscopic mural thrombosis; these were related to the anti-factor Xa and antithrombin effects of the heparin preparations. Platelet deposition in segments with deep arterial injury was 42 +/- 28, 22 +/- 5, 29 +/- 12, 9 +/- 2, 9 +/- 2, and 11 +/- 3 x 10(6)/cm2 (mean +/- SEM) for pigs treated with placebo, with 100, 200, 400, and 500 units/kg CY216, and with 100 units/kg unfractionated heparin, respectively. Fibrinogen/fibrin deposition was 35 +/- 8, 19 +/- 2, 19 +/- 4, 21 +/- 3, 14 +/- 4, and 12 +/- 3 molecules x 10(12)/cm2, respectively; deposition was significantly reduced in pigs given 100 units/kg unfractionated heparin compared with placebo (p less than 0.05). Mural thrombosis was present in 74%, 45%, 30%, 14%, 5%, and 9% of deeply injured arterial segments, respectively (p = 0.02). Plasma anti-factor Xa activity and prolongation of the activated partial thromboplastin time (aPTT) with 100 units/kg unfractionated heparin were similar to that produced by 200 units/kg and 500 units/kg CY216, respectively. Thus, low-molecular-weight heparin, which predominantly inhibits factor Xa activity, was only moderately effective at reducing platelet thrombus deposition. It was less effective than 100 units/kg unfractionated heparin, except at high dosages, producing similar prolongation of the aPTT and the thrombin time.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of probucol dosage on plasma lipid and lipoprotein levels and on protection of low density lipoprotein against in vitro oxidation in humans.
Authors: Reaven P D , Parthasarathy S , Beltz W F , Witztum J L
Published: June 2011

To determine whether probucol's ability to confer antioxidant protection to low density lipoprotein (LDL) could be dissociated from its ability to lower high density lipoprotein (HDL) cholesterol, 17 hypercholesterolemic patients were treated with either a standard dose, 1 g/day (4 tablets), or a low dose, 250 mg/day (1 tablet), of probucol for a 6-month period. Effects of therapy on lipoprotein levels and on susceptibility of LDL to in vitro oxidation were measured at frequent intervals. Probucol levels in plasma LDL rose less rapidly in the 1-tablet group but were nearly 50% of levels in the 4-tablet group after 6 months. HDL cholesterol and apolipoprotein A-1 decreased 17.6% and 27.9%, respectively, in the 1-tablet group compared with 28.0% and 38.3%, respectively, in the 4-tablet group (p = 0.07 and p = 0.06). In the 4-tablet group, LDL was protected from copper and endothelial cell-mediated oxidation after 2 months of therapy. In the 1-tablet group, equal degrees of protection occurred, but only after 6 months of therapy. In the whole study group, the decrease in LDL susceptibility to copper or endothelial cell-mediated oxidative modification was correlated with the content of probucol in LDL (r = 0.73, r = 0.65, p less than 0.005). Additionally, the decrease in HDL cholesterol level was correlated with the increase in protection to LDL from oxidative modification (r = 0.67 for copper, r = 0.58 for endothelial cells, p less than 0.05 for both) and also with the content of probucol in LDL (r = 0.6, p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Plasma lipids and lipoproteins and the incidence of cardiovascular disease in the very elderly. The Bronx Aging Study.
Authors: Zimetbaum P , Frishman W H , Ooi W L , Derman M P , Aronson M , Gidez L I , Eder H A
Published: June 2011

The Bronx Aging Study is a 10-year prospective investigation of very elderly volunteers (mean age at study entry, 79 years; range, 75-85 years) designed to assess risk factors for dementia and coronary and cerebrovascular (stroke) diseases. Entry criteria included the absence of terminal illness and dementia. All subjects (n = 350) included in this report had at least two lipid and lipoprotein determinations. Overall, more than one third of subjects showed at least a 10% change in lipid and lipoprotein levels between the initial and final measurements. Moreover, mean levels for women were consistently different than those for men, and because of this finding subjects were classified into potential-risk categories based on the changes observed by using their sex-specific lipid and lipoprotein distributions. The incidences of cardiovascular disease, dementia, and death were compared between risk groups. Proportional-hazards analysis showed that in men a consistently low high density lipoprotein cholesterol level (less than or equal to 30 mg/dl) was independently associated with the development of myocardial infarction (p = 0.006), cardiovascular disease (p = 0.002), or death (p = 0.002). For women, however, a consistently elevated low density lipoprotein cholesterol level (greater than or equal to 171 mg/dl) was associated with myocardial infarction (p = 0.032). Thus, low high density lipoprotein cholesterol remains a powerful predictor of coronary heart disease risk for men even into old age, while elevated low density lipoprotein cholesterol continues to play a role in the development of myocardial infarction in women. The findings suggest that an unfavorable lipoprotein profile increases the risk of cardiovascular morbidity and mortality even at advanced ages for both men and women.
Clopidogrel inhibits the binding of ADP analogues to the receptor mediating inhibition of platelet adenylate cyclase.
Authors: Mills D C , Puri R , Hu C J , Minniti C , Grana G , Freedman M D , Colman R F , Colman R W
Published: June 2011

Clopidogrel, like the homologous thienopyridine derivative ticlopidine, selectively inhibits platelet aggregation induced by ADP. We have previously described two nucleotide-binding sites on platelets related to ADP-mediated platelet responses. The first is a high-affinity binding site for 2-methylthio-ADP (2-MeSADP) that is linked to the inhibition of stimulated adenylate cyclase. The second is the 100-kd exofacial membrane protein aggregin, which is labeled by the reactive ADP analogue 5'-p-fluorosulfonylbenzoyl adenosine (FSBA) that is related to shape change and aggregation. We set out to determine if either of these sites is blocked in vivo by clopidogrel or its active metabolite. Six subjects were given clopidogrel (75 mg/day for 10 days) in a double-blind crossover experiment. All of the subjects developed prolonged bleeding times while taking the drug. The rate of onset of the effect on bleeding time varied among subjects. Platelet aggregation induced by ADP or thrombin was significantly impaired by the drug treatment, but no effect was detected on shape change. The incorporation of [3H]FSBA into aggregin was also unaffected. Inhibition of adenylate cyclase by ADP or by 2-MeSADP was greatly reduced in all subjects, and in the case of 2-MeSADP, there was evidence for a noncompetitive effect. Inhibition of adenylate cyclase by epinephrine was unaffected. In the three subjects for whom binding measurements were made, the number of binding sites for [32P]2-MeSADP was reduced from 534 +/- 44 molecules per platelet during control and placebo periods (11 determinations) to 199 +/- 78 molecules per platelet during drug treatment (three determinations). There was no consistent change in the binding affinity.(ABSTRACT TRUNCATED AT 250 WORDS)
Induction of T-cell activation by oxidized low density lipoprotein.
Authors: Frostegård J , Wu R , Giscombe R , Holm G , Lefvert A K , Nilsson J
Published: June 2011

Oxidation and scavenger receptor-mediated uptake of low density lipoprotein (LDL) in intimal macrophages are believed to be key events in the development of atherosclerosis. We report here that oxidized LDL increases DNA synthesis, expression of HLA-DR, and interleukin-2 receptors in T cells. The stimulatory effect of oxidized LDL was not due to a direct effect on T cells but required the presence of monocytes. Oxidized LDL also stimulated the release of interleukin-1 beta from monocytes. The maximal effect of oxidized LDL on T-cell activation and interleukin-1 beta release occurred at a concentration of 1 micrograms/ml. Native LDL also had the capacity to activate T cells, although only at higher concentrations. The stimulatory effect of both native and oxidized LDL was inhibited by superoxide dismutase. Monocytes as well as T cells were found to have the ability to oxidize LDL, suggesting that the stimulatory effect of native LDL may arise as a result of LDL oxidation during incubation with monocytes and T cells. The results suggest that oxidized LDL may activate T cells in atherosclerotic lesions.
Functional implications of cAMP and Ca2+ on prostaglandin I2 and thromboxane A2 synthesis by human endothelial cells.
Authors: Griesmacher A , Weigel G , David M , Horvath G , Mueller M M
Published: June 2011

Human umbilical vein endothelial cells were incubated with ATP, ADP, thrombin, or ionophore A23187 for as long as 600 seconds. A statistically significant rise in the prostaglandin I2 (prostacyclin; PGI2) and thromboxane A2 (TxA2) release was observed after 45 seconds. The maximum amount of cytosolic free Ca2+ was reached between 20 and 30 seconds. A statistically significant elevation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels was observed only in response to ATP and ADP after 120 seconds. Furthermore, adenosine, caffeine, phorbol 12-myristate 13-acetate (PMA), and adenosine 5'-(alpha, beta-methylene)triphosphate were tested alone or in combination with ATP or thrombin. PMA inhibited ATP-stimulated eicosanoid biosynthesis but had no effect on thrombin. Of the agents used to increase cytosolic free Ca2+ concentrations, only PMA failed to provoke eicosanoid release. Similarly, only PMA failed to induce a Ca2+ flux in the absence of extracellular Ca2+. The data presented show that PGI2 and TxA2 release from human umbilical cord endothelial cells is closely associated with Ca2+ mobilized from intracellular sources. Extracellular Ca2+, as well as changes in intracellular cAMP levels, has no influence on endothelial eicosanoid synthesis, at least for short-term regulation (less than or equal to 600 seconds).
Diagnosis of heterozygous familial hypercholesterolemia. DNA analysis complements clinical examination and analysis of serum lipid levels.
Authors: Koivisto P V , Koivisto U M , Miettinen T A , Kontula K
Published: June 2011

The concordance of clinical and molecular genetic diagnoses of heterozygous familial hypercholesterolemia (FH) was studied in 65 subjects (10 propositi and 55 first-degree relatives) from 10 families with FH. Nine propositi were carriers of the FH-Helsinki deletion of the low density lipoprotein (LDL) receptor gene, prevalent in the Finnish population, while a new deletion, extending from intron 14 to intron 15 of the LDL receptor gene, was identified in one family. Serum LDL cholesterol levels used in the clinical diagnosis (less than 5.0 mmol/l, not FH; 5.0-5.9 mmol/l, possible FH; greater than or equal to 6.0 mmol/l, FH; limits are 1 mmol/l lower for those less than 18 years) were derived from an authoritative recommendation. Tendon xanthomas constituted an additional criterion. With the DNA analysis as the reference, 55 (85%) subjects could be correctly classified clinically as FH patients or subjects without FH. The remaining 10 subjects were misclassified or were in the "possible FH" category. When the age- and sex-specific 95th percentile LDL cholesterol levels were used instead of the rigid values for both adults and children, the percentage of correct diagnoses rose to 95%. Common genetic polymorphisms of apolipoproteins E and B did not markedly affect LDL cholesterol levels in FH patients, whereas increasing age and obesity were associated with elevated LDL levels. In conclusion, DNA analysis is a valuable adjunct to the diagnosis of FH that is applicable to families with a known mutation of the LDL receptor gene. If DNA methods are not available, age- and sex-specific LDL levels should be used as an aid in the clinical diagnosis of FH.
Early abnormalities in coronary heart disease risk factors in relatives of subjects with non-insulin-dependent diabetes.
Authors: Sarlund H , Pyörälä K , Penttilä I , Laakso M
Published: June 2011

Coronary heart disease risk factor levels were studied in 184 first-degree relatives (sisters and brothers) of non-insulin-dependent diabetic subjects (124 relatives with normoglycemia, 34 relatives with impaired glucose tolerance [IGT], and 26 relatives with non-insulin-dependent diabetes mellitus [NIDDM]) and in 215 relatives of nondiabetic subjects (194 relatives with normoglycemia and 21 relatives with IGT). Subjects with IGT exhibited the highest insulin responses to an oral glucose load. Systolic blood pressure was significantly higher; serum high density lipoprotein cholesterol level was significantly lower; and total, low density lipoprotein, and very low density lipoprotein triglyceride levels were higher in the relatives with a family history of diabetes who had IGT or NIDDM than in the normoglycemic relatives without a family history of diabetes. These abnormal changes were not seen in normoglycemic relatives or relatives with IGT who had no family history of NIDDM. Thus, in relatives of diabetics, abnormal glucose tolerance seems to induce changes in cardiovascular heart disease risk factor levels that are similar to those observed in NIDDM. Therefore, a family history of diabetes adds substantially to the risk for atherosclerosis, particularly in subjects with IGT.