Early Feature Of Atherosclerosis Research Articles

S-11-5: CLINICAL IMPLICATION OF FMD

A healthy endothelium maintains vascular tone and structure by regulating the balance between vasodilation and vasoconstriction, growth inhibition and growth promotion, antithrombosis and prothrombosis, anti-inflammation and proinflammation, and also antioxidation and pro-oxidation. The vascular endothelium is involved in the release of various vasodilators, including nitric oxide (NO), prostaglandins, and endothelium-derived hyperpolarizing factor as well as vasoconstrictors. NO plays an important role in the regulation of vascular tone, the inhibition of platelet aggregation, and the suppression of smooth muscle cell proliferation. Cardiovascular diseases are associated with endothelial dysfunction. In addition, endothelial dysfunction is an early feature of atherosclerosis and vascular diseases in humans. Therefore, it is clinically important to estimate the degree of endothelial dysfunction. Several methods have been used to assess endothelial function in humans. Measurement of flow-mediated vasodilation (FMD) using an ultrasound is noninvasive and is an accurate indicator of NO production. Measurement of FMD is widely performed as an index of conduit artery endothelial function. Several investigators have shown that FMD is an independent predictor for cardiovascular outcomes. It is thought that FMD is useful for surrogate endpoint of cardiovascular outcomes and index of atherosclerotic treatment. However, the evaluation technique by the FMD measurement system still requires skills in measurement of the vessel diameter by an ultrasound system, and is difficult to handle. In addition, there is a problem in that the technique requires a large-scale apparatus and lacks in simplicity. In this session, we would like to explain in detail concerning the methods of assessing and clinical importance of endothelial function, especially FMD.

Accurate arterial path length estimation for pulse wave velocity calculation in growing children and adolescents

Background: Most adult cardiovascular disease begins in childhood. Given the burgeoning obesity pandemic in children worldwide, there is a need for precise and scalable surveillance methods to detect subclinical cardiovascular disease in children and adolescents. Early detection allows early intervention and intensified primary prevention strategies in affected individuals. Carotid-femoral pulse wave velocity (PWV) directly measures arterial wall stiffness, an early feature of atherosclerosis. Calculation of PWV in growing children requires an accurate estimation of the true distance travelled by the aorto-femoral pressure wave, using surface anatomy landmarks. However, a variety of methods are used to estimate this distance, and these have not previously been investigated in growing children and adolescents. We sought to investigate this by comparing true arterial path length measured on computerized tomography (CT) scans, with a variety of estimations based on surface anatomy landmarks. Methods: Arterial path lengths were measured using multi-planar reformation (MPR) imaging software. These measurements were then compared with the surface anatomy measurements obtained using the same MPR imaging software. The fidelity of a variety of arterial path length estimation methods was tested. Results: The surface anatomy distance between the suprasternal notch and the angle of the mandible (PWV recording site in the neck), should be adjusted using the formula y=4.791+(1.0534*x). This value subtracted from the unadjusted distance from the suprasternal notch to the umbilicus, through the mid-inguinal crease to the femoral PWV recording site, provides the simplest reliable approximation of true intraluminal distance travelled. Conclusions: There is high correlation between the surface anatomy distances and the arterial path lengths they represent; however, these are not equal. Most surface anatomy measurements require adjustment using the formulae that we have provided, to accurately estimate the true distance travelled by the pulse wave.

Simvastatin inhibited oxLDL-induced proatherogenic effects through calpain-1-PPARγ-CD36 pathway.

We previously reported that simvastatin, an inhibitor of HMG-CoA reductase, inhibits atherosclerosis in rats. The present study was designed to investigate the effect of simvastatin on mouse peritoneal macrophage foam cell formation, the early feature of atherosclerosis, and explore its mechanisms. The results showed that simvastatin decreased cholesterol content and DiI-oxLDL (1,1'-didodecyl 3,3,3',3'-indocarbocyanine perchlorate - oxidized low-density lipoprotein) uptake, reduced the levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the medium, down-regulated the mRNA and protein expression of CD36 (a fatty acid receptor), and reduced the mRNA expressions of peroxisome proliferator-activated receptor gamma (PPARγ), TNF-α, and IL-6 in macrophages treated with oxLDL. However, PPARγ agonist troglitazone partly abolished the effects of simvastatin on foam cells. In addition, simvastatin reduced the protein expression of calpain-1, a Ca2+-sensitive cysteine protease, in oxLDL-treated macrophages. Furthermore, PD150606, a specific calpain inhibitor, reduced mRNA expressions of PPARγ and CD36 in macrophages treated with oxLDL. Combination of simvastatin and PD150606 had no further effect on mRNA expression of PPARγ and CD36 compared with either alone. However, over-expression of calpain-1 in macrophages partly reversed the simvastatin effects, including cell cholesterol content, mRNA expressions of PPARγ, and CD36. The results suggested that simvastatin inhibits foam cell formation of oxLDL-treated macrophages through a calpain-1-PPARγ-CD36 pathway.

CV-159, a Unique Dihydropyridine Derivative, Prevents TNF-Induced Inflammatory Responses in Human Umbilical Vein Endothelial Cells

CV-159, a 1,4-dihydropyridine derivative, has Ca2+antagonistic and anti-calmodulin actions. An early feature of atherosclerosis is vascular endothelial inflammatory change. We examined whether CV-159 has protective effects against endothelial inflammatory responses. After pretreatment of human umbilical vein endothelial cells (ECs) with CV-159 (10 μM, 30 min), TNF-α (10 ng/ml) was applied for 20 min or 24 h. Expressions of inflammatory markers and activation of inflammatory signal molecules were examined by Western blotting. Reactive oxygen species (ROS) generation was examined by using 2′,7′-dichlorodihydrofluorescein diacetate. CV-159 inhibited TNF (24 h)–induced expression of e-selectin but not vascular cell adhesion molecule-1 and intercellular adhesion molecule-1. CV-159 inhibited TNF (20 min)–induced phosphorylation of JNK, p38, and NF-κ B p65 (Ser536). A JNK inhibitor, SP600125, and a p38 inhibitor, SB203580, inhibited TNF-induced e-selectin expression. An antioxidant drug, N-acetyl-l-cysteine (NAC), inhibited TNF-induced e-selectin expression. NAC inhibited TNF-induced phosphorylation of JNK and p38 but not NF-κB. CV-159 inhibited TNF-induced ROS generation. Our results indicate that in ECs CV-159 specifically inhibits TNF-induced e-selectin expression through inhibition of JNK, p38, and NF-κB phosphorylation. It is suggested that CV-159 prevents activation of JNK and p38 through inhibition of ROS, while it prevents activation of NF-κB via a ROS-independent manner.

Lack of Significant Association between Intima-Media Thickness in the Carotid Artery and Serum TSH Level. The Tromsø Study

Increased arterial wall intima-media thickness (IMT) is an early feature of atherosclerosis and has been reported to be altered in patients with thyroid dysfunction. The present study was performed to examine the relation between carotid artery intima-media thickness and possible variations in thyroid function in normal subjects using serum TSH as a surrogate index of thyroid function. A total of 2034 subjects (974 males) were studied, 1856 or whom were non-users of thyroxine. The subjects not taking thyroxine were classified into three groups, those with a low serum TSH (0.48 mIU/L (2.5 percentile, those with serum TSH from 0.48 to 4.16 mIU/L, and those with high serum TSH of >4.16 mIU/L (97.5 percentile). Carotid ultrasound was performed in each all 2034 subjects to determine IMT. Among those not taking thyroxine, subjects in the low serum TSH group had a higher mean IMT as compared to those in the normal and high serum TSH groups but the differences were not significant when adjusted for gender, age, smoking status, body mass index, systolic blood pressure and serum cholesterol (0.88 +/- 0.15 mm, 0.84 +/- 0.16 mm, and 0.84 +/- 0.24 mm respectively). Subjects taking thyroxine had significantly higher IMT than those not taking thyroxine (0.89 + 0.20 mm versus 0.84 + 0.17 mm, p<0.01). No significant relationship between carotid IMT and serum TSH levels was observed in normal, non thyroxine taking, subjects. Carotid IMT was increased in subjects taking thyroxine. Whether the increase in carotid IMT is due to thyroxine ingestion or underlying thyroid disease cannot be answered from the study.

Insulin resistance increases circulating malondialdehyde-modified LDL and impairs endothelial function in healthy young men

Background: Endothelial dysfunction is regarded as an early feature of atherosclerosis. Both LDL oxidation and insulin resistance play important roles in the pathogenesis of atherosclerosis. Recent studies have demonstrated a significant association between oxidized LDL and insulin resistance. Methods: We investigated relationships between insulin resistance, circulating malondialdehyde-modified (MDA)-LDL, and endothelial function in 36 healthy young men. Insulin sensitivity was estimated according to homeostasis model assessment of insulin resistance (HOMA-IR); we defined subjects with values of at least 2.5 as an insulin resistant ( n=12) and those with values below 2.5 as insulin sensitive ( n=24). We evaluated endothelial function by flow-mediated vasodilation (FMD) of brachial artery during reactive hyperemia, using high-resolution ultrasound. We also measured serum MDA-LDL by a sandwich enzyme-linked immunosorbent assay. Results: MDA-LDL was significantly higher (146±46 vs. 101±32 IU/l, P=0.002) and FMD was significantly lower (3.94±1.53 vs. 5.59±1.62 %, P=0.002) in the insulin-resistant group than in the insulin-sensitive group. The resistant group showed a significant inverse correlation between MDA-LDL and FMD ( r=−0.675, P=0.016), while the sensitive group did not ( r=0.163, NS). By multivariate regression analysis, MDA-LDL and age were determinants of FMD ( R 2=0.766) in the insulin-resistant group, while no variable determined FMD in the sensitive group. Nitroglycerin-induced endotheliumindependent dilation was similar in both groups. Conclusions: These results suggest that the production of circulating MDA-LDL may be accelerated by insulin resistance, thus impairing endothelial function even in healthy young men.

Statins enhance postischemic hyperemia in the skin circulation of hypercholesterolemic patients: A monitoring test of endothelial dysfunction for clinical practice?

ObjectivesThe present study aims to investigate whether laser Doppler flowmetry can be used to monitor improvements in vascular function during statin therapy. BackgroundEndothelial dysfunction is an early feature of atherosclerosis in hypercholesterolemic patients and can be improved by statins. There are several methods to assess endothelial function in vivo, none of them being feasible in everyday practice. MethodsSkin perfusion, measured by laser Doppler flowmetry, was assessed at rest and during reactive hyperemia. Nineteen hypercholesterolemic patients (age 42 to 73 years, total cholesterol 5.4 to 9.6 mmol/l) were studied before and during statin therapy. To further investigate the mechanisms, postischemic skin hyperemia was measured before and after intradermal injection of the nitric oxide synthase inhibitor L-NAME and its inactive isoform D-NAME (0.5 μmol/10 μl each). On a separate day, the healthy volunteers were reexamined before and 2 h after 1,000 mg aspirin. ResultsPostischemic skin blood flow was markedly reduced in hypercholesterolemic patients (45 ± 11%) compared with healthy controls (238 ± 20%, p < 0.0001) and improved after statin therapy (113 ± 15%, p = 0.0005 vs. pre-treatment). In the healthy volunteers, the hyperemic responses were not significantly different after L-NAME and D-NAME. Aspirin reduced hyperemia from 274 ± 49% to 197 ± 40% (p = 0.025). ConclusionsReactive hyperemia of the skin microcirculation can be easily and reproducibly assessed by laser Doppler flowmetry. Vasodilator prostaglandins are the major mediators of postischemic skin hyperemia, which is impaired in hypercholesterolemic patients and can be enhanced by cholesterol-lowering therapy. Thus, laser Doppler flowmetry may represent a tool to assess and monitor vascular function during therapy in everyday practice.

New methods to evaluate endothelial function: method for assessing endothelial function in humans using a strain-gauge plethysmography: nitric oxide-dependent and -independent vasodilation.

The vascular endothelium is involved in the release of various vasodilators, including nitric oxide (NO), prostaglandins, and endothelium-derived hyperpolarizing factor as well as vasoconstrictors. NO plays an important role in the regulation of vascular tone, the inhibition of platelet aggregation, and the suppression of smooth muscle cell proliferation. Several diseases are associated with changes in endothelial function mediated through reduced NO bioavailability. In addition, endothelial dysfunction is an early feature of atherosclerosis and vascular diseases in humans. Therefore, it is clinically important to estimate the degree of endothelial dysfunction. Several methods have been used to assess endothelial function in humans. Recently, we have evaluated the effects of intra-arterial infusion of infusion of NO agonists, such as acetylcholine, methacholine, and bradykinin, and NO antagonists on forearm blood flow using mercury-filled Silastic strain-gauge plethysmography. The response to the intra-arterial infusion of vasoactive agents should be considered the gold standard in assessing endothelial function, because the use of agonists to stimulate NO release allow us to draw more specific conclusions concerning the role of basal and stimulated NO release. However, the invasive method is time-consuming and is a burden for patients. A noninvasive method of measuring forearm blood flow response to reactive hyperemia also is useful in assessing endothelial function. In this review we would like to explain in detail the methods of assessing endothelial function in humans using strain-gauge plethysmography.

Angiotensin type 1 receptor antagonism reverses abnormal coronary vasomotion in atherosclerosis

OBJECTIVESThis study was performed to determine whether angiotensin type 1 (AT1) receptor inhibition improves abnormal coronary vasomotion and endothelial dysfunction in patients with atherosclerosis or its risk factors.BACKGROUNDEndothelial dysfunction, an early feature of atherosclerosis, contributes to abnormal vasomotion during stress. Angiotensin II may contribute to endothelial dysfunction in atherosclerosis.METHODSIn 25 patients, mean age 59 ± 2 years, with atherosclerosis or its risk factors, we measured coronary vasomotion during flow-mediated dilation (FMD) in response to adenosine, cold pressor test (CPT) and exercise before and after AT1 receptor blockade with intracoronary losartan (5 mg).RESULTSLosartan did not alter resting coronary vascular tone, but epicardial FMD improved from 5.6 ± 1.5% to 8.9 ± 1.8% (p = 0.02). Abnormal epicardial vasomotion during CPT and exercise also improved with losartan from −1.7 ± 0.8% to 1.5 ± 0.1% (p = 0.02) and −0.6 ± 0.9% to 3.4 ± 1.2% (p = 0.009), respectively. Improvement in epicardial vasomotion was most prominent in segments with baseline endothelial dysfunction evidenced as constriction during stress. Microvascular dilation during adenosine, an endothelium-independent response, was unchanged with losartan.CONCLUSIONSInhibition of the coronary vascular AT1 receptors in patients with atherosclerosis improves epicardial vasomotion during stress, probably by improving endothelial dysfunction. Whether AT1 receptor blockade will provide long-term therapeutic benefits in atherosclerosis needs further investigation.

Lipophilic statins induce apoptosis of human vascular smooth muscle cells

The accumulation of vascular smooth muscle cells (VSMC) in the intima is an early feature of atherosclerosis that results from a balance of migration from the media, proliferation, and eventual death (including programmed cell death) of VSMC. Several reports have described that HMG-CoA reductase inhibitors (statins) attenuate both the migration and proliferation of VSMC. However, the potential effect of statins on VSMC programmed cell death has received little attention. Human and rat VSMC were incubated with different concentration of statins in the presence of fetal bovine serum as a survival factor. The presence of apoptosis was evaluated by morphological criteria, flow cytometry and DNA electrophoresis. Lipophilic statins induced, in a dose-dependent manner the appearance of VSMC apoptosis. The effect of statins was fully reversed by mevalonate, farnesylpyrophosphate, and geranylgeranypyrophosphate, but not by cholesterol or other mevalonate metabolites, suggesting a role for isoprenoids in VSMC apoptosis. In addition, the induction of apoptosis by statins was associated with the inhibition of prenylation of Rho B. The present results suggest that protein prenylation inhibition by statins may be involved in statin-induced VSMC apoptosis. These data provide a new potential mechanism by which statins may modulate the evolution of atherosclerotic lesions.

Brachial artery ultrasound: a noninvasive tool in the assessment of triglyceride-rich lipoproteins.

In recent years, endothelial dysfunction has been identified as an early feature of atherosclerosis. Endothelial function can be measured noninvasively by using brachial artery ultrasound. A variety of factors associated with atherosclerosis also impair endothelial function. Some of these factors are lipoproteins such as various forms of low-density lipoproteins, postprandial chylomicron remnants, fasting triglyceride-rich particles, and free fatty acids. A high-fat diet also has an adverse effect on endothelial function. Several interventions can improve endothelial function and, at the same time, reduce cardiovascular events. Measuring endothelial function may eventually serve as a useful index to determine an individual's risk for coronary artery disease.

Intimal proliferation in an organ culture of human internal mammary artery.

Intimal smooth muscle cell proliferation is an early feature of atherosclerosis. Its progression is difficult to monitor in humans and previous studies have mostly relied on necropsy material. The aim of this study was therefore to establish whether intimal proliferation occurred in an organ culture of human internal mammary artery. Segments of freshly isolated internal mammary artery were maintained din standard tissue culture medium containing 30% calf serum for 14 d. Tissue viability (measured by ATP concentration) was maintained during processing and throughout the culture period [211(SEM 28) nmol ATP.g-1 wet weight on d 1 v 208(27) on d 14]. Histological transverse sections of cultured internal mammary artery showed the development of a neointima containing smooth muscle cells identified by immunocytochemistry for alpha actin. Pulse labelling of cultures with [3H]-thymidine showed proliferating cells predominantly in a neointimal layer with few dividing cells in the media. Cultured de-endothelialized vessels showed less neointimal thickening than cultured freshly isolated vessels [16(3) v 36(5) microns, p < 0.0025] as well as a reduced number of dividing cells per mm of neointimal length [3.1(0.6) v 5.5(1.1), p < 0.05]. Intimal proliferation occurred in organ culture of internal mammary artery. There is evidence for a factor derived from the endothelium, which may be important in the development of intimal proliferation.