Aortic pressure-diameter relationship assessed by intravascular ultrasound: experimental validation in dogs.
(25/10763)
Intravascular ultrasound (IVUS) has emerged as an important diagnostic method for evaluating vessel diameter and vessel wall motion. To evaluate the validity of IVUS in assessing changes in the pressure-diameter relationship we compared measurements of abdominal aortic diameters derived from IVUS with those simultaneously obtained at the same site using implanted sonomicrometers in five chronically instrumented conscious dogs and in seven acutely instrumented anesthetized dogs. Five hundred eighty beats were analyzed to obtain peak systolic and end-diastolic diameters and to calculate aortic compliance at different blood pressure levels induced either by an aortic pneumatic cuff or by intravenous injections of nitroglycerin or norepinephrine. IVUS agreed closely with sonomicrometer measurements at different blood pressure levels. However, IVUS slightly but significantly underestimated aortic diameters by 0.6 +/- 0.7 mm for systolic diameters (P < 0.001) and by 0.7 +/- 0.6 mm for diastolic diameters (P < 0.001) compared with the sonomicrometer measurements. We conclude that IVUS is a feasible and reliable method to measure dynamic changes in aortic dimensions and has the potential to provide ready access to assess aortic compliance in humans. (+info)
Identification of phospholipase C beta isoforms and their location in cultured vascular smooth muscle cells of pig, human and rat.
(26/10763)
OBJECTIVES: Four phospholipase C (PLC) beta isoforms have been described in pig aortic vascular smooth muscle. The aim was to determine if all four PLC beta isoforms are commonly expressed in vascular smooth muscle cells (VSMC) of three species, i.e. pig, human and rat, and if the individual isoforms had distinctive intracellular distributions. METHODS: Vascular smooth muscle cell cultures were derived from explants of porcine and rat aorta and a human renal artery cell line. PLC beta isoform content was resolved using Western blotting. Intracellular location was determined by immunocytochemistry and confocal microscopy. RESULTS: All three species expressed PLCs, beta 1, beta 2, beta 3 and beta 4. In all species, PLC beta 1 demonstrated foci of concentration throughout the cytoplasm; PLC beta 2 demonstrated a punctate pattern that was principally at the cell periphery or was in the Golgi, depending upon the antibody used; PLC beta 3 was also cytoplasmic but showed a different pattern from PLC beta 1 and PLC beta 4 was cytoplasmic, except in pig quiescent cells, where it was associated with filamentous structures at the intersection with the plasma membrane. CONCLUSIONS: VSMCs of three different species express all four PLC beta isoforms. Each isoform has a unique and consistent signature of distribution that is generally common to all species. (+info)
Blockade of nitric oxide-induced relaxation of rabbit aorta by cysteine and homocysteine.
(27/10763)
AIM: To examine the inhibition by L-cysteine (Cys) and L-homocysteine (HoCys) of NO-induced relaxation of aorta. METHODS: The tension of rabbit aortic rings in oxygenated Krebs' solution was recorded isometrically. RESULTS: Pretreatment of endothelium-denuded rings with Cys or HoCys inhibited the NO-induced increase in cGMP. The inhibitory effects of Cys or HoCys on relaxation responses to subsequent additions of NO 75 nmol.L-1 gradually diminished with time, which was consistent with the loss of the sulfhydryl concentration of Cys and HoCys. Superoxide dismutase (SOD) 35 kU.L-1 attenuated the inhibition by Cys and HoCys of NO-induced relaxation. Neither boiled SOD nor catalase 100 kU.L-1 antagonized the inhibitory effects of Cys. Preaddition of SOD 35 kU.L-1 inhibited the reduction of cytochrome C by Cys. Increasing concentrations of SOD from 35 to 350 kU.L-1 intensified the cytochrome C reduction. Addition of xanthine 300 mumol.L-1 plus xanthine oxidase 1 U.L-1 to the mixture of cytochrome C 60 mumol.L-1 and Cys 100 mumol.L-1 produced an additional augmentation of SOD-inhibitable reduction of cytochrome C. The rate of the reduction of cytochrome C induced by HoCys 100 mumol.L-1 was much slower than with Cys. Addition of NO reduced the SH concentrations of both the supernatant of aortic homogenate and Cys in Krebs' solution. CONCLUSION: The inhibition by the SH compounds of NO is mediated partly by the superoxide generated by the auto-oxidation of these compounds, and partly by a direct reaction of SH groups with NO. (+info)
Oxidized low-density lipoproteins stimulate adhesion of monocytes to endothelial cells.
(28/10763)
AIM: To study the effects of oxidized low-density lipoproteins (ox-LDL) on the adhesiveness of monocytes to endothelial cells. METHODS: LDL was obtained from healthy human plasma by ultracentrifugation, and oxidized by CuSO4 10 mumol.L-1. The assay of adhesion was performed using cultured bovine aortic endothelial cells (BAEC) and human peripheral blood monocytes. RESULTS: Pretreatment BAEC with ox-LDL enhanced monocyte adhesion to BAEC in time- and dose-dependent manner. ox-LDL as little as 10 mg.L-1 and 30 min of preincubation stimulated monocyte adhesion. Cycloheximide (Cyc, a protein synthesis inhibitor) 1 mg.L-1 and staurosporine (Sta, a PKC inhibitor) 20 nmol.L-1 abolished the effect of ox-LDL (60 mg.L-1), but dextran sulfate 20 mg.L-1 had no effect on monocyte adhesion. Phorbol 12-myristate 13-acetate (PMA) 1 nmol.L-1 and lysophosphatidylcholine (Lys) 6 mumol.L-1 mimicked the effects of ox-LDL and potentiated monocyte adhesion. Sta also suppressed the augmentative effects of Lys and PMA. CONCLUSION: ox-LDL enhances the adhesion of monocytes to BAEC through the activation of PKC. (+info)
Analysis of macrophage scavenger receptor (SR-A) expression in human aortic atherosclerotic lesions.
(29/10763)
The class A scavenger receptors (SR-As) are trimeric, integral membrane glycoproteins that exhibit unusually broad ligand-binding properties. A number of studies have suggested that these receptors may play an important role in host defense and in many macrophage-associated pathological processes, including atherosclerosis and Alzheimer's disease. The study of the expression and function of these receptors in human disease has been hampered by the lack of suitable antibodies recognizing human SR-A. This has generated questions regarding the nature of receptors responsible for scavenger receptor activity detected in a variety of cell types, including monocytes, macrophages, smooth muscle cells, and endothelial cells. To address these questions, we have produced high-titer antisera recognizing human SR-A by using mice deficient for SR-A (SR-A -/-). We show that SR-A -/- mice produce a significantly higher-titer immune response than do wild-type (SR-A +/+) littermates, with antisera of the former having a broad species reactivity and recognizing SR-A from humans, mice, and rabbits. The antisera recognize both type I and II SR-A in a wide range of immunological techniques. Using these antisera we show that the expression of SR-A protein is induced during monocyte to macrophage differentiation and that SR-A mediates 80% of the uptake of acetylated low density lipoprotein by human monocyte-derived macrophages. We also establish that human SR-A is expressed by tissue macrophages in liver and lung and by macrophage-derived foam cells within aortic atherosclerotic lesions, with little detectable expression by smooth muscle cells or aortic endothelium. (+info)
Atherosclerotic aortic gangliosides enhance integrin-mediated platelet adhesion to collagen.
(30/10763)
Gangliosides, sialic acid-containing glycosphingolipids, accumulate in atherosclerotic vessels. Their role in the pathogenesis of atherosclerosis is unknown. Gangliosides isolated from tumor cells promote collagen-stimulated platelet aggregation and ATP secretion and enhance platelet adhesion to immobilized collagen. These activities are all mediated by ganglioside effects on the platelet integrin collagen receptor alpha2beta1. Therefore, we hypothesized that gangliosides isolated from atherosclerotic plaques would enhance platelet adhesion to immobilized collagen, a major component of the subendothelial matrix of blood vessels. Furthermore, we questioned whether this effect of atherosclerotic gangliosides might play a role in the pathogenesis of atherosclerosis. To test this hypothesis, we isolated the gangliosides from postmortem aortas of patients with extensive atherosclerotic disease and examined their effects on platelet adhesion. Samples of aortic tissue taken from areas involved with atherosclerotic plaque demonstrated accumulation of gangliosides (64.9+/-6.5 nmol/g wet weight) compared with gangliosides isolated from control normal aortic tissue taken from children who died of noncardiac causes (NAGs; 21.1+/-6.4 nmol/g wet weight). Interestingly, samples of tissue taken from diseased aortas but from areas not involved with gross plaque formation also demonstrated ganglioside accumulation (47.6+/-12.8 nmol/g wet weight). Next, the activity of each of these gangliosides on platelet adhesion to immobilized type I collagen was studied. Atherosclerotic aortic gangliosides (AAGs) as well as those isolated from grossly unaffected areas of the same aorta (UAGs) both increased platelet adhesion compared with control NAGs (OD570, 0. 37+/-0.11 and 0.29+/-0.14 versus 0.16+/-0.07, respectively; P<0.01 and P<0.05, respectively). These OD570 values corresponded to 9x10(5), 8x10(4), and 6x10(3) platelets per well after preincubation with 5 micromol/L AAG, UAG, and NAG, respectively. Increased adhesion was observed after preincubation with as little as 0.5 micromol/L AAG, and maximal adhesion was seen at 2.5 micromol/L, with a plateau extending to the highest concentration tested, 10 micromol/L. The effect of AAGs on platelet adhesion to collagen was abrogated by incubation of treated platelets with F-17 anti-alpha2 monoclonal antibody (OD570, 0.13+/-0.02). Finally, the effects of the major individual gangliosides isolated from atherosclerotic tissues, GM3 and GD3, were tested. GM3 increased adhesion to collagen (OD570, 0.415+/-0.06) as did GD3 (0.31+/-0.08). Similar to that of AAGs, the effect of both molecules was blocked by F-17 (0. 09+/-0.04 and 0.13+/-0.06, respectively). These experiments demonstrate that accumulated atherosclerotic gangliosides promote platelet adhesion to collagen, the major component of the subendothelial matrix. Furthermore, this activity is mediated by an effect of the gangliosides on the collagen-binding integrin alpha2beta1. This activity may provide a mechanism for the development of platelet thrombi at sites where atherosclerotic gangliosides accumulate and help to explain the role of platelets in the process of atherosclerotic disease progression. (+info)
ApoA1 reduces free cholesterol accumulation in atherosclerotic lesions of ApoE-deficient mice transplanted with ApoE-expressing macrophages.
(31/10763)
Along with apolipoprotein (apo) E, which promotes cholesterol efflux from foam cells, apoA1-containing high density lipoprotein (HDL) is thought to facilitate the transport of cholesterol from lesions. This role for apoA1 was tested in vivo by lethally irradiating apoE-deficient and apoE- plus apoA1-deficient mice and reconstituting them with bone marrow cells isolated from wild-type (WT) mice. ApoE, but not apoA1, was synthesized by the transplanted bone marrow-derived cells. Therefore, this transplantation procedure generated apoE-deficient animals with atherosclerotic lesions that contained both apoE and apoA1 (E/A1 mice) and apoE-deficient animals with lesions that contained apoE but no apoA1 (E/A1o mice). As shown previously, the transplanted WT macrophage-derived apoE dramatically lowered the plasma hypercholesterolemia in both groups. On feeding with an atherogenic diet after transplantation, plasma cholesterol levels were raised in both groups of mice, but the levels in the E/A1 mice at 20 weeks were 2- to 3-fold higher than in E/A1o mice. Immunohistochemical staining verified that apoE was abundant in lesions of both groups, whereas apoA1 was detected in the lesions of E/A1 mice only. Despite a 2- to 3-fold lower total plasma cholesterol in the E/A1o mice, the free cholesterol recovered from isolated aortas was approximately 60% higher and the mean lesion area in serial sections of the aortic valves 45% larger. Therefore, apoA1 reduces free cholesterol accumulation in vivo in atherosclerotic lesions. (+info)
Generation and characterization of human smooth muscle cell lines derived from atherosclerotic plaque.
(32/10763)
The study of atherogenesis in humans has been restricted by the limited availability and brief in vitro life span of plaque smooth muscle cells (SMCs). We describe plaque SMC lines with extended life spans generated by the expression of the human papillomavirus (HPV)-16 E6 and E7 genes, which has been shown to extend the life span of normal adult human aortic SMCs. Resulting cell lines (pdSMC1A and 2) demonstrated at least 10-fold increases in life span; pdSMC1A became immortal. The SMC identity of both pdSMC lines was confirmed by SM22 mRNA expression. pdSMC2 were generally diploid but with various structural and numerical alterations; pdSMC1A demonstrated several chromosomal abnormalities, most commonly -Y, +7, -13, anomalies previously reported in both primary pdSMCs and atherosclerotic tissue. Confluent pdSMC2 appeared grossly similar to HPV-16 E6/E7-expressing normal adult aortic SMCs (AASMCs), exhibiting typical SMC morphology/growth patterns; pdSMC1A displayed irregular cell shape/organization with numerous mitotic figures. Dedifferentiation to a synthetic/proliferative phenotype has been hypothesized as a critical step in atherogenesis, because rat neonatal SMCs and adult intimal SMCs exhibit similar gene expression patterns. To confirm that our pdSMC lines likewise express this apparent plaque phenotype, osteopontin, platelet-derived growth factor B, and elastin mRNA levels were determined in pdSMC1A, pdSMC2, and AASMCs. However, no significant increases in osteopontin or platelet-derived growth factor B expression levels were observed in either pdSMC compared with AASMCs. pdSMC2 alone expressed high levels of elastin mRNA. Lower levels of SM22 mRNA in pdSMC1A suggested greater dedifferentiation and/or additional population doublings in pdSMC1A relative to pdSMC2. Both pdSMC lines (particularly 1A) demonstrated high message levels for matrix Gla protein, previously reported to be highly expressed by human neointimal SMCs in vitro. These results describe 2 novel plaque cell lines exhibiting various features of plaque SMC biology; pdSMC2 may represent an earlier plaque SMC phenotype, whereas pdSMC1A may be representative of cells comprising an advanced atherosclerotic lesion. (+info)