Endothelial dysfunction in coronary artery disease

Plasma detection of NO by a catheter

Nitric oxide (NO) released by endothelial cells in response to hemodynamic shear stress is a key controller molecule of the vascular functions and antiatherogenic mechanisms. Endothelial dysfunction is associated with increased cardiovascular events. Therefore, several indirect techniques have been employed to evaluate endothelial function or NO bioavailability. However, a growing body of evidences suggests limitations of the indirect methods for evaluation of NO bioavailability. In years, it has been considered that NO is immediately oxidized or inactivated in blood stream. However, recent studies suggest that NO remain active in blood stream, causing remote biological response. Therefore, measuring plasma NO concentration directly in the circulation will contribute to clarify the kinetics and physiological roles of NO and to evaluate endothelial function. In this article, the measurement of plasma NO concentration using a newly developed catheter-type NO sensor will be described.

Hypergravity induces ATP release and actin reorganization via tyrosine phosphorylation and RhoA activation in bovine endothelial cells

Mechanical stresses regulate physiological and pathological functions of vascular endothelial cells. We examined, in this study, the effects of hypergravity on endothelial functions. Hypergravity (3 G) applied by low speed centrifuge immediately induced a membrane translocation of small G-protein RhoA and tyrosine phosphorylation of 125 kDa FAK in bovine aortic endothelial cells (BAECs). Hypergravity also induced a transient reorganization of actin fibers in 3 min, which was inhibited by Rho-kinase inhibitor (Y27632) and tyrosine kinase inhibitors (herbimycin A and tyrphostin 46). Furthermore, the extracellular ATP concentration ([ATP]o) was increased by 2 G and 3 G hypergravity in 5 min, and the inhibitors of Rho-kinase, tyrosine kinase, and volume-regulated anion channels (VRAC; verapamil, tamoxifen and fluoxetine) significantly suppressed [ATP]o elevation. Application of 3 G hypergravity for 1 h increased the nuclear uptake of BrdU, which was inhibited by Rho-kinase inhibitor and VARC inhibitors. Furthermore, intermittent application of 3 G hypergravity for 1 or 2 h/day stimulated endothelial migration in 5 days, and this was inhibited by suramin, a P2 antagonist. Collectively, these results indicate that hypergravity induces ATP release and actin reorganization via RhoA activation and FAK phosphorylation, thereby activating cell proliferation and migration in BAECs. These also suggest that gravity can be regarded as an extracorporeal signal that could significantly affect endothelial functions.

Hyperinsulinemia and impaired leptin-adiponectin ratio associate with endothelial nitric oxide synthase polymorphisms in subjects with in-stent restenosis

Little is known about the association of endothelial nitric oxide synthase (NOS3) gene polymorphisms and the presence of insulin resistance and the early evolution of atherosclerosis in nondiabetic subjects with cardiovascular disease (CAD) and stent implantation. The present study was performed in an attempt to better understand whether metabolic, endothelial, and angiographic findings characteristic of subjects with cardiovascular disease and in-stent restenosis are related to NOS3 variants. This is a case-control study performed from 2002 to 2006. All subjects admitted to the study were recruited in the Nord-Centre of Italy, most from Milan and its surrounding towns. Measures of glucose tolerance, insulin sensitivity, markers of endothelial dysfunction, forearm vasodilation, and adipokine levels were determined and associated to the frequency of two single-nucleotide polymorphisms of NOS3, i.e., Glu298Asp (rs1799983, G/T) and rs753482 (intron 18 A/C). A total of 747 subjects, not known to have diabetes, were evaluated: 333 subjects had asymptomatic CAD, 106 subjects had unstable angina and were evaluated for in-stent restenosis 6 mo after stent placement, and 308 were control subjects. The presence of TT and CC minor alleles was significantly greater in case groups compared with control subjects. At phenotypic level, subjects with the polymorphisms were characterized by hyperinsulinemia and reduced reactive hyperemia, whereas increased leptin and decreased adiponectin levels were present in subjects with restenosis in the presence of reduced minimal lumen diameter and length of stenosis almost doubled. Hyperinsulinemia, endothelial dysfunction, and a more atherogenic profile seem to be peculiar features of subjects with asymptomatic CAD and restenosis carrying NOS3 gene variants.

Endothelial dysfunction in diabetes mellitus

Diabetes mellitus is associated with an increased risk of cardiovascular disease, even in the presence of intensive glycemic control. Substantial clinical and experimental evidence suggest that both diabetes and insulin resistance cause a combination of endothelial dysfunctions, which may diminish the anti-atherogenic role of the vascular endothelium. Both insulin resistance and endothelial dysfunction appear to precede the development of overt hyperglycemia in patients with type 2 diabetes. Therefore, in patients with diabetes or insulin resistance, endothelial dysfunction may be a critical early target for preventing atherosclerosis and cardiovascular disease. Microalbuminuria is now considered to be an atherosclerotic risk factor and predicts future cardiovascular disease risk in diabetic patients, in elderly patients, as well as in the general population. It has been implicated as an independent risk factor for cardiovascular disease and premature cardiovascular mortality for patients with type 1 and type 2 diabetes mellitus, as well as for patients with essential hypertension. A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. The role of chronic hyperglycemia in the development of diabetic microvascular complications and in neuropathy has been clearly established. However, the biochemical or cellular links between elevated blood glucose levels, and the vascular lesions remain incompletely understood. A number of trials have demonstrated that statins therapy as well as angiotensin converting enzyme inhibitors is associated with improvements in endothelial function in diabetes. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes. In the present review we provide the up to date details on this subject.

Endothelial cell migration on RGD-peptide-containing PEG hydrogels in the presence of sphingosine 1-phosphate

Sphingosine 1-phosphate (S1P) is a potent chemokinetic agent for endothelial cells that is released by activated platelets. We previously developed Arg-Gly-Asp (RGD)-containing polyethylene glycol biomaterials for the controlled delivery of S1P to promote endothelialization. Here, we studied the effects of cell adhesion strength on S1P-stimulated endothelial cell migration in the presence of arterial levels of fluid shear stress, since an upward shift in optimal cell adhesion strengths may be beneficial for promoting long-term cell adhesion to materials. Two RGD peptides with different integrin-binding specificities were added to the polyethylene glycol hydrogels. A linear RGD bound primarily to beta(3) integrins, whereas a cyclic RGD bound through both beta(1) and beta(3) integrins. We observed increased focal adhesion formation and better long-term adhesion in flow with endothelial cells on linear RGD peptide, versus cyclic RGD, even though initial adhesion strengths were higher for cells on cyclic RGD. Addition of 100 nM S1P increased cell speed and random motility coefficients on both RGD peptides, with the largest increases found on cyclic RGD. For both peptides, much of the increase in cell migration speed was found for smaller cells (<1522 microm(2) projected area), although the large increases on cyclic RGD were also due to medium-sized cells (2288-3519 microm(2)). Overall, a compromise between high cell migration rates and long-term adhesion will be important in the design of materials that endothelialize after implantation.

The influence of obesity on calf blood flow and vascular reactivity in older adults

OBJECTIVE

To determine whether differences in vascular reactivity existed among normal weight, overweight, and obese older men and women, and to examine the association between abdominal fat distribution and vascular reactivity.

METHODS

Eighty-seven individuals who were 60 years of age or older (age = 69 +/- 7 yrs; mean +/- SD) were grouped into normal weight (BMI < 25; n = 30), overweight (BMI > or = 25 and < 30; n = 28), or obese (BMI > or = 30; n = 29) categories. Calf blood flow (BF) was assessed by venous occlusion strain-gauge plethysmography at rest and post-occlusive reactive hyperemia.

RESULTS

Post-occlusive reactive hyperemia BF was lower (p = 0.038) in the obese group (5.55 +/- 4.67%/min) than in the normal weight group (8.34 +/- 3.89%/min). Additionally, change in BF from rest to post-occlusion in the obese group (1.93 +/- 2.58%/min) was lower (p = 0.001) than in the normal weight group (5.21 +/- 3.59%/min), as well as the percentage change (75 +/- 98% vs. 202 +/- 190%, p = 0.006, respectively). After adjusting for age, prevalence in hypertension and calf skinfold thickness, change in BF values remained lower (p < 0.05) in obese subjects compared to the normal weight subjects. Lastly, the absolute and percentage change in BF were significantly related to BMI (r = -0.44, p < 0.001, and r = -0.37, p < 0.001, respectively) and to waist circumference (r = -0.36, p = 0.001, and r = -0.32, p = 0.002).

CONCLUSION

Obesity and abdominal adiposity impair vascular reactivity in older men and women, and these deleterious effects on vascular reactivity are independent of conventional risk factors.

Arterial endothelial function in a porcine model of early stage atherosclerotic vascular disease

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the United States and is projected to become the leading cause of mortality in the world. Atherosclerosis is the most important single factor contributing to this disease burden. In this study, we characterize relationships between endothelial dysfunction and vascular disease in an animal model of diet-induced, early-stage atherosclerotic vascular disease. We tested the hypothesis that hypercholesterolaemia induces vascular disease and impairs endothelium-dependent relaxation (EDR) in conduit arteries of adult male Yucatan pigs. Pigs were fed a normal fat (NF) or high fat cholesterol (HFC) diet for 20-24 weeks. Results indicate that, while the HFC diet did not alter EDR in femoral or brachial arteries, EDR was significantly decreased in both carotid and coronary arteries. Sudanophilic fatty streaks were significantly present in the abdominal aorta and common carotid artery. Histopathology revealed increased intima-media thickness (IMT) and foam cell accumulation in Stary Stage I-III lesions in the abdominal aorta, common carotid artery and femoral arteries. In the coronary arteries, the accumulation of foam cells in Stary Stage I and II lesions resulted in a trend for increased IMT. There was no evidence of vascular disease in the brachial arteries. These results indicate that early stages of CVD (Stary Stage I-III) precede decreases in EDR induced by HFC diet, because femoral arteries exhibited foam cell accumulation and an increased IMT but no change in endothelial function.

Tissue kallikrein gene polymorphisms induce no change in endothelium-dependent or independent vasodilation in hypertensive and normotensive subjects

BACKGROUND

Tissue kallikrein (TK) generates Lys-bradykinin, which is then converted to bradykinin and releases nitric oxide (NO) from endothelial cells via B2 receptors. TK gene inactivation in mice causes severe endothelial dysfunction, which is also a hallmark of human primary hypertension (PH). Healthy carriers of a loss-of-function Arg to His substitution at position 53 (R53H) of the TK gene exhibit paradoxical arterial eutrophic remodeling. We therefore investigated the impact of this and other TK gene single nucleotide polymorphisms (SNPs) on endothelium-dependent vasodilatation (EDV) and endothelium-independent vasodilatation (EIV) in PH patients and normotensive (NT) subjects.

METHODS

The TK gene SNPs were genotyped blind to the phenotype by sequencing. We compared EDV and EIV vasodilatation across TK genotypes in 131 uncomplicated PH patients and 51 healthy NT subjects. EDV and EIV were assessed as the forearm blood flow response to a graded infusion of acetylcholine and sodium nitroprusside, respectively. We also evaluated the impact of the SNPs on NO-mediated EDV and on reactive oxygen species (ROS)-induced NO breakdown with the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine or vitamin C, respectively.

RESULTS

Genotypes and allele frequencies were in Hardy-Weinberg equilibrium and similar in PH and NT. EDV was lower in PH patients than in NT subjects. No TK genotype affected either EDV or EIV per se, or via interaction with gender and age. NO inhibition and scavenging of ROS showed no TK genotype effect on EDV. Similar conclusions were obtained with haplotype analysis.

CONCLUSIONS

These results do not support the contention that TK gene SNPs have a major impact in determining NO-mediated responses to acetylcholine.

The T(-786)C endothelial nitric oxide synthase genotype predicts cardiovascular mortality in high-risk patients

OBJECTIVES

This study sought to investigate the impact of a common T(-786)C single-nucleotide polymorphism (SNP) in the promoter of the endothelial nitric oxide synthase (eNOS, NOS3) gene on cardiovascular (CV) death in a prospective cohort study.

BACKGROUND

The T(-786)C SNP eNOS gene implies a blunted endothelium-dependent vasodilation in hypertensive patients and was associated with multivessel coronary artery disease in cross-sectional studies, but it remained unsettled whether it carried prognostic information.

METHODS

In consecutive white patients of the GENICA (Genetic and Environmental Factors in Coronary Atherosclerosis) study, who underwent coronary angiography between 1999 and 2001, we determined the incidence of CV death at follow-up. The eNOS T(-786)C and the exon 7 G(894)T SNPs were determined by melting curve analysis of amplicons from allele-specific fluorescence resonance energy transfer probes. Plasma levels of nitrate/nitrite, nitrotyrosine, and myeloperoxidase were also measured. The Kaplan-Meier and Cox regression analyses were used to assess the impact of SNPs on event-free survival.

RESULTS

Complete follow-up data were obtained in 1,086 (98%) patients. After a median follow-up of 1,296 days (range 4 to 2,057 days), we observed 85 (8.2%) CV deaths. There was a significant impact of the T(-786)C eNOS genotype on CV death-free (p = 0.0102) survival, but no differences in CV death rates across G(894)T genotypes. The TT individuals, who showed a lower survival, exhibited higher plasma myeloperoxidase (p < 0.0001) and lower levels of nitrotyrosine (p < 0.0001) than CC patients.

CONCLUSIONS

The T(-786)C SNP in the promoter of eNOS bears independent prognostic information and is associated with changes in markers of oxidant stress in high-risk white patients referred for coronary angiography.

Role of protein O-linked N-acetyl-glucosamine in mediating cell function and survival in the cardiovascular system

There is growing recognition that the O-linked attachment of N-acetyl-glucosamine (O-GlcNAc) on serine and threonine residues of nuclear and cytoplasmic proteins is a highly dynamic post-translational modification that plays a key role in signal transduction pathways. Numerous proteins have been identified as targets of O-GlcNAc modifications including kinases, phosphatases, transcription factors, metabolic enzymes, chaperons, and cytoskeletal proteins. Modulation of O-GlcNAc levels has been shown to modify DNA binding, enzyme activity, protein-protein interactions, the half-life of proteins, and subcellular localization. The level of O-GlcNAc is regulated in part by the metabolism of glucose via the hexosamine biosynthesis pathway (HBP), and the metabolic abnormalities associated with insulin resistance and diabetes, such as hyperglycemia, hyperlipidemia, and hyperinsulinemia, are all associated with increased flux through the HBP and elevated O-GlcNAc levels. Increased HBP flux and O-GlcNAc levels have been implicated in the impaired relaxation of isolated cardiomyocytes, blunted response to angiotensin II and phenylephrine, hyperglycemia-induced cardiomyocyte apoptosis, and endothelial and vascular cell dysfunction. In contrast to these adverse effects, recent studies have also shown that O-GlcNAc levels increase in response to acute stress and that this is associated with increased cell survival. Thus, while the relationship between O-GlcNAc levels and cellular function is complex and not well-understood, it is clear that these pathways play a critical role in the regulation of cell function and survival in the cardiovascular system and may be implicated in the adverse effects of metabolic disease on the heart.

Adventures in vascular biology: a tale of two mediators

I would like to thank the Royal Society for inviting me to deliver the Croonian Lecture. In so doing, the Society is adding my name to a list of very distinguished scientists who, since 1738, have preceded me in this task. This is, indeed, a great honour. For most of my research career my main interest has been the understanding of the normal functioning of the blood vessel wall and the way this is affected in pathology. During this time, our knowledge of these subjects has grown to such an extent that many people now believe that the conquering of vascular disease is a real possibility in the foreseeable future. My lecture concerns the discovery of two substances, prostacyclin and nitric oxide. I would like to describe the moments of insight and some of the critical experiments that contributed significantly to the uncovering of their roles in vascular biology. The process was often adventurous, hence the title of this lecture. It is the excitement of the adventure that I would like to convey in the text that follows.

Vitamin K1 (phylloquinone) induces vascular endothelial dysfunction: Role of oxidative stress

We aimed to investigate the mechanisms underlying the vascular effects induced by phylloquinone (Vitamin K1; VK1). Vascular reactivity experiments, using standard muscle bath procedures, showed that VK1 (5 and 50 microM) enhances the contractile response of endothelium-intact, but not denuded, rat carotid rings to phenylephrine. Similarly, maximal contraction induced by phenylephrine was enhanced in the presence of the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). The combination of L-NAME and VK1 did not produce any further additional effect. Pre-incubation of intact-rings with VK1 reduced both acetylcholine- and bradykinin-induced relaxation. VK1 induced an increment in tension on carotid rings submaximally pre-contracted with phenylephrine. VK1-induced increment in tension was completely abolished by endothelial removal or incubation of intact rings with L-NAME and L-NNA. Conversely, 7-nitroindazole, 1400 W, or indomethacin did not affect VK1-induced contraction. Moreover, VK1 reduced L-arginine-induced relaxation in endothelium-intact rings. Lucigenin-amplified chemiluminescence assays showed that VK1 induced an increase in the level of superoxide anions in endothelium-intact but not denuded rings. Measurement of nitrite and nitrate generation showed that VK1 did not alter nitrate formation but strongly inhibited the generation of nitrite. Finally, the superoxide anions scavenger tiron prevented the endothelial vasomotor dysfunction caused by VK1 on phenyleprine-induced contraction and acetylcholine or bradykinin-induced relaxation. In conclusion, our data show that VK1 disrupts the vasomotor function of rat carotid. Our results suggest that VK1-induced oxidative stress through production of superoxide anion is interfering with the NO pathway, which in turn is responsible for the altered vascular reactivity induced by VK1.

The role of vessel wall physiology in predicting coronary bypass graft patency

Not applicable.

Effect of hypercholesterolemia on experimental colonic anastomotic wound healing in rats

AIM: To evaluate the mechanical and biochemical parameters of colonic anastomotic healing in hypercholesterolemic rats.

METHODS: Sixty rats were divided into two groups of 30 each according to their dietary regimens. The test group was fed with a high cholesterol-containing diet for two months while the control group had standard diet. These two groups were further divided into three subgroups consisting of ten rats each. After hypercholesterolemia was established, left colon resection and anastomosis were performed in both groups and samples from liver and abdominal aorta were taken to evaluate the systemic effects of hypercholesterolemia. Anastomotic wound healing, blow-out pressures and tissue hydroxyproline levels were evaluated.

RESULTS: The test group had a significant weight gain in two months. Microscopic examination of the abdominal aorta revealed no atherosclerotic change in none of the groups, but liver tissue specimens showed significant steatosis in the test group. Tissue hydroxyproline levels and anastomotic blow-out pressures were significantly lower in the test group than in the controls.

CONCLUSION: Hypercholesterolemia not only increases hydroxyproline levels and blow-out pressures but also worsens anastomotic wound healing.

Nitric oxide and the vascular endothelium

The vascular endothelium synthesises the vasodilator and anti-aggregatory mediator nitric oxide (NO) from L-arginine. This action is catalysed by the action of NO synthases, of which two forms are present in the endothelium. Endothelial (e)NOS is highly regulated, constitutively active and generates NO in response to shear stress and other physiological stimuli. Inducible (i)NOS is expressed in response to immunological stimuli, is transcriptionally regulated and, once activated, generates large amounts of NO that contribute to pathological conditions. The physiological actions of NO include the regulation of vascular tone and blood pressure, prevention of platelet aggregation and inhibition of vascular smooth muscle proliferation. Many of these actions are a result of the activation by NO of the soluble guanylate cyclase and consequent generation of cyclic guanosine monophosphate (cGMP). An additional target of NO is the cytochrome c oxidase, the terminal enzyme in the electron transport chain, which is inhibited by NO in a manner that is reversible and competitive with oxygen. The consequent reduction of cytochrome c oxidase leads to the release of superoxide anion. This may be an NO-regulated cell signalling system which, under certain circumstances, may lead to the formation of the powerful oxidant species, peroxynitrite, that is associated with a variety of vascular diseases.

Basal endothelial nitric oxide release is preserved in overweight and obese adults

OBJECTIVE

Impaired basal nitric oxide release is associated with a number of cardiovascular disorders including hypertension, arterial spasm, and myocardial infarction. We determined whether basal endothelial nitric oxide release is reduced in otherwise healthy overweight and obese adult humans.

RESEARCH METHODS AND PROCEDURES

Seventy sedentary adults were studied: 32 normal weight (BMI <25 kg/m(2)), 24 overweight (BMI > or = 25 < 30 kg/m(2)), and 14 obese (BMI > or = 30 kg/m(2)). Forearm blood flow (FBF) responses to intra-arterial infusions of N(g)-monomethyl-L-arginine (5 mg/min), a nitric oxide synthase inhibitor, were used as an index of basal nitric oxide release.

RESULTS

N(g)-monomethyl-L-arginine elicited significant reductions in FBF in the normal weight (from 4.1 +/- 0.2 to 2.7 +/- 0.2 mL/100 mL tissue/min), overweight (4.1 +/- 0.1 to 2.8 +/- 0.2 mL/100 mL tissue/min), and obese (3.9 +/- 0.3 to 2.7 +/- 0.2 mL/100 mL tissue/min) subjects. Importantly, the magnitude of reduction in FBF (approximately 30%) was similar among the groups.

DISCUSSION

These results indicate that the capacity of the endothelium to release nitric oxide under basal conditions is not compromised in overweight and obese adults.

Reactive oxygen species production via NADPH oxidase mediates TGF-beta-induced cytoskeletal alterations in endothelial cells

Cytoskeletal alterations in endothelial cells have been linked to nitric oxide generation and cell-cell interactions. Transforming growth factor (TGF)-beta has been described to affect cytoskeletal rearrangement in numerous cell types; however, the underlying pathway is unclear. In the present study, we found that human umbilical vein endothelial cells (HUVEC) have marked cytoskeletal alterations with short-term TGF-beta treatment resulting in filipodia formation and F-actin assembly. The cytoskeletal alterations were blocked by the novel TGF-beta type I receptor/ALK5 kinase inhibitor (SB-505124) but not by the p38 kinase inhibitor (SB-203580). TGF-beta also induced marked stimulation of reactive oxygen species (ROS) within 5 min of TGF-beta exposure. TGF-beta stimulation of ROS was mediated by the NAPDH oxidase homolog Nox4 as DPI, an inhibitor of NADPH oxidase, and dominant-negative Nox4 adenovirus blocked ROS production. Finally, inhibition of ROS with ROS scavengers or dominant-negative Nox4 blocked the TGF-beta effect on cytoskeleton changes in endothelial cells. In conclusion, our studies show for the first time that TGF-beta-induced ROS production in human endothelial cells is via Nox4 and that TGF-beta alteration of cytoskeleton in HUVEC is mediated via a Nox4-dependent pathway.

Evaluation of bioavailability of nitric oxide in coronary circulation by direct measurement of plasma nitric oxide concentration

Although bioavailability of NO in the coronary circulation is commonly evaluated by acetylcholine (ACh)-induced vasodilation, a change in plasma NO concentration and its relation to the flow response after injection of ACh are still unknown. Thus, we directly measured the concentration of NO in the coronary sinus by using a catheter-type NO sensor for coronary sinus. An NO-sensitive sensor was located and fixed in a 4-Fr catheter with a soft tip for protection of vascular wall. After calibration with an NO-saturated pure water, the catheter-type NO sensor was located in the coronary sinus in anesthetized dogs. The coronary flow velocity (CFV) was measured with a Doppler guide wire. Intracoronary injection of ACh (0.4 and 1.0 microg/kg) increased plasma NO concentration in a dose-dependent manner (3-10 nM). Although ACh increased CFV by 95%, there was no significant difference between the two ACh doses. After ACh, the peak value of plasma NO concentration was observed significantly later than CFV. N(G)-methyl-L-arginine (NO synthase inhibitor) decreased basal NO concentration by 3 nM and suppressed the ACh-induced NO synthesis with no significant change in average peak velocity. We conclude that production of NO in the coronary circulation can be evaluated in the coronary sinus. Although ACh increases both CFV and NO concentration, CFV dose not reflect NO concentration in terms of magnitude and time course. Direct measurement of plasma NO concentration by the catheter-type NO sensor is useful to evaluate bioavailability of NO in the coronary circulation.

Low Frequency Regular Exercise Improves Flow-Mediated Dilatation of Subjects with Mild Hypertension

Although exercise is recommended for the primary prevention of hypertension, and although it is generally known to have a beneficial effect on endothelial function, working individuals often find it difficult to maintain a consistent exercise regimen. In the present study, therefore, we examined the effects of infrequently performed exercise on flow-mediated dilatation (FMD), which is an index of endothelial function, in 15 subjects with hypertension (mild hypertensives) and 10 normotensive subjects (normotensives). All subjects performed mild bicycle exercise twice a week for 12 weeks. To assess the FMD, the diameter of the brachial artery was measured using ultrasound at baseline, during reactive hyperemia, and following sublingual administration of nitroglycerin. Measurement of these parameters was performed twice, at the beginning and the end of the exercise program. At the baseline, FMD was significantly lower in the mild hypertensives than in the normotensives. Nitroglycerin-mediated dilatation (NTG-D) was similar in the two groups. The exercise decreased blood pressure in the mild hypertensives, and increased high-density lipoprotein (HDL) cholesterol in both groups. The exercise improved FMD without altering NTG-D in the mild hypertensives, but did not result in any change in the normotensives. Multiple regression analysis revealed that the elevation in FMD was positively associated with changes in HDL cholesterol, and negatively associated with changes in plasma norepinephrine and systolic blood pressure. These findings suggest that regular exercise at a low frequency improves FMD, and thereby endothelial function, and lowers blood pressure in mild hypertensives.

Improved Endothelium Dependent Vasodilation in Endurance Athletes and Its Relation With ACE I/D Polymorphism

BACKGROUND

Aerobic exercise enhances endothelium-dependent vasodilation in healthy individuals. It is thought that exercise increases nitric oxide (NO) production and decreases NO inactivation, leading to an increase in NO bioavailability. Angiotensin II and NO have important roles in maintaining vascular tone. There are polymorphisms of the angiotensin converting enzyme (ACE) gene and the presence of the deletion (D) allele has been associated with higher concentrations of circulating and tissue ACE. In this study, the relationship between endothelial function and ACE gene polymorphisms was investigated in athletes and sedentary subjects.

METHODS AND RESULTS

The study group comprised 56 endurance athletes and 46 sedentary subjects who underwent brachial artery ultrasonographic examination. ACE insertion (I) and D allele frequencies were analyzed in all patients. Baseline brachial artery diameter and resting blood flow were similar in athletes and controls (p > 0.05). The flow-mediated dilation (FMD) was 8.48+/-3.65% in athletes and 5.16+/-2.5% in controls (p = 0.0001). FMD was significantly different between ACE genotypes in the athletes (p < 0.0001): it was higher in ACE II (10.5+/-1.6%) subjects than in the DI (8.4+/-2.3%) or DD (7+/-1.2%) subgroups.

CONCLUSION

Regular isotonic exercise can improve endothelium-dependent vasodilation especially in those with the ACE II genotype.

A high-fat, refined-carbohydrate diet induces endothelial dysfunction and oxidant/antioxidant imbalance and depresses NOS protein expression

We tested whether consumption of a high-fat, high-sucrose (HFS) diet can affect endothelium-dependent relaxation, whether this precedes the development of diet-induced hypertension previously noted in this model, and whether it is mediated, in part, by changes in nitric oxide synthase (NOS) and/or NOS regulatory proteins. Female Fischer rats were fed either a HFS diet or standard low-fat, complex-carbohydrate chow starting at 2 mo of age for 7 mo. Vasoconstrictive response to KCl and phenylephrine was similar in both groups. Vasorelaxation to acetylcholine was significantly impaired in the HFS animals, and there were no differences in relaxation to sodium nitroprusside, suggesting that the endothelial dysfunction is due, at least in part, to nitric oxide deficiency. HFS consumption decreased protein expression of endothelial NOS in aorta, renal, and heart tissues, neuronal NOS in kidney, heart, aorta, and brain, and inducible NOS in heart and aorta. Caveolin-1 and soluble guanylate cyclase protein expression did not change, but AKT protein expression decreased in heart and aorta and increased in kidney tissue. Consumption of HFS diet raised brain carbonyl content and plasma hydrogen peroxide concentration and diminished plasma total antioxidant capacity. Because blood pressure, which is known to eventually rise in this model, was not as yet significantly elevated, the present data suggest that endothelial dysfunction precedes the onset of diet-induced hypertension. The lack of a quantitative change in caveolin-1 and soluble guanylate cyclase protein content indicates that alteration in these proteins is not responsible for the endothelial dysfunction. Thus nitric oxide deficiency combined with antioxidant/oxidant imbalance, appears to be a primary factor in the development of endothelial dysfunction in this model.

Vascular Endothelial Growth Factor Regulates Reendothelialization and Neointima Formation in a Mouse Model of Arterial Injury

Background— The rate of reendothelialization is critical in neointima formation after arterial injury. Vascular endothelial growth factor (VEGF), a potent endothelial mitogen, has been advocated for accelerating endothelial repair and preventing intimal hyperplasia after percutaneous coronary interventions. However, the precise mechanism of action of VEGF treatment and the physiologic role of endogenous VEGF after arterial injury are not well described. To better understand the role of VEGF in arterial repair, we overexpressed both VEGF and a soluble, chimeric VEGF receptor (VEGF-trap), which binds free VEGF with high affinity, in a mouse model of arterial injury.

Methods and Results— Four groups of C57BL/6 mice underwent denuding endothelial injury 1 day after systemic injection of recombinant adenovirus expressing (1) VEGF, (2) VEGF-trap, (3) VEGF plus VEGF-trap, or (4) control adenovirus. Circulating levels of adenovirus-encoded proteins were significantly elevated after gene transfer. VEGF overexpression accelerated reendothelialization and increased luminal endothelial cell proliferation 2 weeks after arterial injury ( P <0.05), resulting in decreased neointima formation at 4 weeks compared with control ( P <0.01). Cotreatment with VEGF-trap completely sequestered free VEGF and abrogated the beneficial effect of VEGF overexpression. Interestingly, sequestration of endogenous VEGF by VEGF-trap overexpression alone also led to delayed reendothelialization at 2 weeks ( P <0.01) and increased neointima formation at 4 weeks ( P <0.01).

Conclusions— VEGF overexpression accelerated endothelial repair and inhibited neointima formation after arterial injury. Conversely, sequestration of exogenous and/or endogenous VEGF by VEGF-trap delayed reendothelialization and significantly increased neointima size. This demonstrates the therapeutic potential of VEGF but also emphasizes the important physiologic role of endogenous VEGF in vascular repair.

Endothelial progenitor cells for postnatal vasculogenesis

In the past decade, researchers have defined committed stem or progenitor cells from various tissues, including bone marrow, peripheral blood, brain, liver, and reproductive organs, in both adult animals and humans. Whereas most cells in adult organs are composed of differentiated cells, which express a variety of specific phenotypic genes adapted to each organ's environment, quiescent stem or progenitor cells are maintained locally or in the systemic circulation and are activated by environmental stimuli for physiological and pathological tissue regeneration. Recently, endothelial progenitor cells (EPCs) were isolated from peripheral blood CD34, Flk-1, or AC133 antigen-positive cells, which are considered to include a hematopoietic stem cell population, and were shown to be incorporated into foci of neovascularization. This finding, that circulating EPCs may home to sites of neovascularization and differentiate into endothelial cells in situ, is consistent with "vasculogenesis," a critical paradigm for embryonic neovascularization, and suggests that vasculogenesis and angiogenesis may constitute complementary mechanisms for postnatal neovascularization. Previous reports demonstrating therapeutic potential of EPC transplantation in animal models of hindlimb and myocardial ischemia opened the way to the clinical application of cell therapy: the replacement of diseased or degenerating cell populations, tissues, and organs. In this review, we summarize biological features of EPCs and speculate on the utility of EPCs for vascular and general medicine.

Medical therapy for pulmonary arterial hypertension: ACCP evidence-based clinical practice guidelines

Pulmonary arterial hypertension (PAH) is often difficult to diagnose and challenging to treat. Untreated, it is characterized by a progressive increase in pulmonary vascular resistance leading to right ventricular failure and death. The past decade has seen remarkable improvements in therapy, driven largely by the conduct of randomized controlled trials. Still, the selection of most appropriate therapy is complex, and requires familiarity with the disease process, evidence from treatment trials, complicated drug delivery systems, dosing regimens, side effects, and complications. This chapter will provide evidence-based treatment recommendations for physicians involved in the care of these complex patients. Due to the complexity of the diagnostic evaluation required, and the treatment options available, it is strongly recommended that consideration be given to referral of patients with PAH to a specialized center.

Endothelial function in coronary arterioles from pigs with early-stage coronary disease induced by high-fat, high-cholesterol diet: effect of exercise

Because hypercholesterolemia can attenuate endothelial function and exercise training can augment endothelial function, we hypothesized that exercise training would improve endothelial function of coronary arterioles from pigs in the early stages of cardiovascular disease induced by a high-fat, high-cholesterol (HF) diet. Yucatan miniature swine were fed a normal-fat (NF) diet or HF diet (2% cholesterol) for 20 wk in which 8 and 46% of their calories were derived from fat, respectively. Both groups were subdivided into sedentary (Sed) or exercise-trained (Ex) groups. This resulted in four experimental groups: NFSed, NFEx, HFSed, and HFEx. Endothelial function was assessed in coronary arterioles 75-100 microm in diameter dissected from the left ventricular apex. Responses to endothelial-dependent dilation induced by bradykinin (BK), ADP, and flow were similar in all four groups, whereas dilation to aggregating platelets in the presence of indomethacin and ketanserin was attenuated in HFSed arterioles (P = 0.01). The attenuated response to aggregating platelets was prevented or reversed in HFEx arterioles (P = 0.03). In HFSed arterioles, BK induced release of an indomethacin-sensitive prostanoid constrictor. In contrast, after exercise training, there was no evidence of this constrictor and BK-induced release of an indomethacin-sensitive prostanoid dilator in HFEx arterioles (P = 0.04). Endothelial nitric oxide synthase protein in arterioles was significantly reduced in HF groups (P < 0.05) and increased in Ex groups (P < 0.05). Interestingly, the relative contribution of nitric oxide to BK-induced dilation, as assessed with nitro-L-arginine methyl ester, was similar in arterioles in the NF, HF, Sed, and Ex groups. These results suggest that, in the early stages of cardiovascular disease, a high-fat, high-cholesterol diet has modest effects on endothelial-dependent dilation in coronary arterioles; nonetheless, these effects are prevented or reversed with exercise training.

The effect of estrogen on serum nitric oxide concentrations in normotensive and DOCA Salt hypertensive ovariectomized rats

BACKGROUND

Cardiovascular disease (CVD) is less prevalent in premenopausal women and women receiving estrogen replacement therapy (ERT) than in postmenopausal women or men. It proposed that the cardiovascular effects of estrogen are mediated, at least in part, through the ability of estrogen to increase nitric oxide (NO) synthesis. This study investigated the effect of estrogen on serum NO concentrations in normotensive and deoxycorticostrone acetate (DOCA) Salt hypertensive ovariectomized rats.

METHODS

Forty-eight female rats were ovariectomized and randomly divided into six groups. Hypertension was induced by DOCA Salt method. DOCA was injected 30 mg/kg of body weight subcutaneously, twice a week with NaCl 1% instead of tap water for drinking throughout the treatment period. Estradiol valerate (Es) was injected i.m. once a week. The groups were as follows: (2) DOCA (4 weeks) and DOCA+Es (6 weeks), (22) DOCA (10 weeks), (222) normal saline (N/S) (4 weeks)+Es (6 weeks), (2V) N/S (10 weeks), (V) DOCA (4 weeks), and (V2) N/S (4 weeks). Serum NO concentrations were measured in groups 1, 3 and 4 before and after treatment. Other groups were used as control.

RESULTS

Results showed that in normotensive animals, serum NO concentrations were increased after estrogen treatment significantly (90.20 +/- 18.67 vs. 19.11 +/- 1.78 micromol/l) (p < 0.05). Also, estrogen increased serum NO concentrations in DOCA Salt hypertensive rats (73.54 +/- 22.55 vs. 36.94 +/- 10.73 micromol/l) (p = 0.06).

CONCLUSION

Estrogen can increase serum NO concentrations in normotensive and DOCA Salt hypertensive animals and it may be important in cardiovascular effects of estrogen.

Repeated epicardial coronary artery endothelial injuries lead to a global spontaneous coronary artery spasm

OBJECTIVES

This study was conducted to develop a spontaneous coronary spasm model.

MATERIALS AND METHODS

Balloon endothelial denudation was carried out in the epicardial left anterior descending coronary artery (LAD) every 2 weeks, for a total of four times, in 12 pigs. Changes in the denuded site diameter and LAD blood flow caused by acetylcholine or serotonin were assessed before each denudation and at week 8. Blood pressure, electrocardiogram (ECG) from the LAD area and LAD blood flow were monitored continuously in conscious and unrestrained pigs.

RESULTS

Spontaneous ECG ST depression with a decrease in LAD blood flow appeared at around 2 weeks. In accordance with this, 0.5 microg/kg acetylcholine induced similar ECG and LAD blood flow changes without denuded site narrowing, suggesting microvascular spasm. Thereafter, ECG ST depression or elevation by serotonin via a denuded site spasm was found after 6 weeks and spontaneous ECG ST changes due to epicardial coronary artery spasm were observed.

CONCLUSION

Epicardial coronary artery endothelial injury may induce spontaneous vasospasticity in the downstream coronary microvessels as well as in the denuded portion, suggesting functional abnormality through the entire coronary arterial tree.

Exercise preserves endothelium-dependent relaxation in coronary arteries of hypercholesterolemic male pigs

We tested the hypothesis that exercise training (Ex) attenuates hypercholesterolemia-induced impairment of endothelium-dependent relaxation (EDR) in male porcine coronary arteries [left anterior descending coronary arteries (LAD)] by increasing nitric oxide (NO) release [due to increased endothelial NO synthase (NOS) expression] and/or increased bioactivity of NO. Adult male pigs were fed a normal-fat (NF) or high-fat (HF) diet for 20–24 wk. Pigs were Ex or remained sedentary (Sed) for 16–20 wk, beginning after 4 wk on diet. Four groups of pigs were used: NF-Sed, NF-Ex, HF-Sed, and HF-Ex. HF enhanced LAD contractions induced by KCl, aggregating platelets (AP), and serotonin (5-HT). AP and 5-HT produced EDR after blockade of cyclooxygenase with indomethacin (Indo) and smooth-muscle 5-HT2 receptors with ketanserin. HF impaired EDR induced by AP, 5-HT, and bradykinin. Results indicate a decreased contribution of NO to EDR in HF-Sed LADs, because the percentage of bradykinin-induced EDR inhibited by NG-nitro-l-arginine methyl ester was 27% in NF-Sed and 34% in NF-Ex but only 17% in HF-Sed. Also, NG-nitro-l-arginine methyl ester + Indo results indicate that release of an Indo-sensitive vasoconstrictor contributes to blunted EDR in HF-Sed LAD. Immunoblot and immunohistochemistry results indicate the following: 1) LAD endothelial NOS protein content was similar among groups; 2) HF decreased LAD superoxide dismutase (SOD) but increased caveolin-1 content; and 3) Ex increased SOD content of HF LADs. We conclude that HF impairs EDR by impairing the contribution of NO released from NOS (due to decreased SOD and increased caveolin-1 protein content) and by production of an Indo-sensitive vasoconstrictor. Ex preserves EDR in HF LADs by decreasing the production of the constrictor and increasing NO-release by NOS and/or NO bioactivity and bioavailability.

Role of Corticotropin-Releasing Factor Receptor Type 2β in Urocortin-Induced Vasodilation of Rat Aortas

Urocortin has a high affinity for the corticotropin-releasing factor receptor type 2beta (CRF-R2beta). This study was conducted to reveal the role of CRF-R2beta in blood vessels. CRF-R2beta expressions were detected both in smooth muscle and endothelium from Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) aortas, and there was no significant difference between them. Urocortin reduced phenylephrine-induced contraction of aorta with endothelium dose-dependently in both rats. However, deendothelialization significantly but not completely (about 50%) reduced the vasodilation. The reduction of vasodilatory action of urocortin by deendothelialization was age-dependent in SHR. An adenylyl cyclase inhibitor, SQ22536, significantly inhibited urocortin-induced relaxation in denuded WKY and SHR aortas, while in preparations with endothelium, neither SQ22536 nor L-NMMA reduced the relaxation. However, simultaneous addition of both drugs significantly reduced the relaxation. In contrast to young rats (7-week-old), in aged rats (19-week-old), L-NMMA successfully reduced urocortin-induced relaxation of aorta with endothelium. These results suggest that urocortin relaxes aorta at least partly via two signal pathways, that is, an increase in intracellular cAMP by binding to CRF-R2beta expressed in smooth muscle cells and NO production from endothelium evoked by binding to the receptors expressed in endothelium and that aging increases the role of the latter system.

The T-786C endothelial nitric oxide synthase genotype is a novel risk factor for coronary artery disease in Caucasian patients of the GENICA study

OBJECTIVES

We investigated the association of polymorphisms in the promoter region and exon 7 endothelial nitric oxide synthase (eNOS) gene with coronary artery disease (CAD).

BACKGROUND

Endothelial dysfunction foretells cardiovascular events and can be genetically determined.

METHODS

We genotyped for the promoter (T(-786)C) and exon 7 (Glu298Asp, G(894)T) polymorphisms in 1,225 subjects; 1,106 were consecutive patients undergoing coronary angiography and 119 control subjects without any cardiovascular risk factors. Genotyping was performed with melting curve analysis of polymerase chain reaction products from allele-specific acceptor and donor probes that were 5'- and 3'-end labeled with LCRed640 and fluorescein, respectively; CAD was assessed by quantitative coronary angiography. We performed multiple logistic regression analysis for the effect of the T(-786)C, the missense Glu298Asp variant, and other coronary risk factors on two- and three-vessel CAD.

RESULTS

The overall genotype distribution of T(-786)C (CC = 17.7%, CT = 40.4%, and TT = 41.9%) and Glu298Asp (GG = 43.3%, GT = 37.0%, and TT = 19.7%) was consistent with the Hardy-Weinberg equilibrium. The regression analysis showed that the T(-786)C, but not the missense Glu298Asp variant, significantly predicted CAD, independent of other risk factors. Compared with TT homozygous, subjects carrying the C allele had a significant (p = 0.002) increase in the odds ratio of harboring two- or three-vessel CAD of 1.672 (95% confidence interval, 1.062 to 2.527). A subgroup analysis confirmed this effect of the T(-786)C polymorphism in men (p = 0.007), cigarette smokers (p = 0.001), subjects older than 60 years of age (p = 0.007), with hypercholesterolemia (p = 0.011), low high-density lipoprotein cholesterol (p = 0.006), and overweight or with obesity (p = 0.041).

CONCLUSIONS

The C allele at the T(-786)C endothelial nitric oxide synthase polymorphism is associated with a higher risk of multivessel CAD in Caucasians.

Type 2 diabetes, cardiovascular risk, and the link to insulin resistance

BACKGROUND

Patients with type 2 diabetes mellitus frequently have coexistent dyslipidemia, hypertension, and obesity, and are at risk for microvascular and macrovascular disease complications such as myocardial infarction, stroke, retinopathy, and microalbuminuria. To optimize cardiovascular health outcomes for patients with type 2 diabetes, strategies to reduce the risks of microvascular and macrovascular disease are needed in clinical practice.

OBJECTIVE

This article provides an overview of the cardiovascular risk profile of patients with type 2 diabetes and discusses the cardiovascular consequences of use of the thiazolidinediones (insulin-sensitizing agents) in the treatment of type 2 diabetes.

METHODS

A literature search of MEDLINE/PubMed was performed to identify relevant articles published from 1966 to April 2003. Search terms used were diabetes, cardiovascular disease, atherosclerosis, dyslipidemia, obesity, hypertension, blood pressure, hyperglycemia, inflammation, C-reactive protein, fibrinolysis, plasminogen activator inhibitor type-1, microalbuminuria, thiazolidinediones, safety, hepatotoxicity, and edema. Bibliographies within the identified articles were also evaluated for additional relevant articles and information.

RESULTS

Recommendations for cardiovascular risk reduction through preventive and therapeutic strategies that target the symptoms of insulin resistance may reduce the microvascular and macrovascular sequelae of diabetes and ameliorate the impact of other components of the metabolic syndrome, including hypertension, hyperglycemia, and obesity. In this regard, thiazolidinediones are promising therapies.

CONCLUSIONS

Early data suggest that, in addition to reducing hyperglycemia, pioglitazone and rosiglitazone effect changes in the dyslipidemic profile, hemodynamics, vascular inflammation, and endothelial functioning of patients with type 2 diabetes. Additional research is needed to further distinguish the cardiovascular benefits of these drugs.

Influence of oral contraceptive use on endothelial t-PA release in healthy premenopausal women

We determined the influence of oral contraceptives (OC) on the capacity of the endothelium to release tissue-type plasminogen activator (t-PA). Twenty-three healthy premenopausal women were studied: 12 nonusers and 11 users of OC. Net endothelial release rates of t-PA were calculated as the product of the arteriovenous concentration gradient and forearm plasma flow in response to intra-arterial bradykinin (BK: 12.5-50 ng. 100 ml tissue(-1) x min(-1)) and sodium nitroprusside (SNP: 1.0-4.0 microg x 100 ml tissue(-1) x min(-1)). Net release of t-PA antigen and increment in t-PA activity across the forearm to BK increased (P < 0.01) in a dose-dependent fashion and to similar extents in the nonusers and users of OC. At the highest BK dose, net release of t-PA antigen was 64.5 +/- 8.2 and 66.2 +/- 15.4 ng x 100 ml tissue(-1) x min(-1) in the nonusers and users of OC, whereas the net increment in t-PA activity was 18.6 +/- 3.0 and 16.0 +/- 2.0 IU. 100 ml tissue(-1) x min(-1), respectively. There was no effect of SNP on t-PA release in either group. These results indicate that endothelial t-PA release is not altered in premenopausal women who use oral contraception.

Age- and hypertension-induced changes in abnormal contractions in rat aorta

The current investigation explored the potential age-dependant modulation of abnormal spontaneous constrictions (thromboxane-like) in the spontaneously hypertensive rat (SHR) aorta, observed only after the inhibition of endogenous production of nitric oxide (NO). Aortic rings from SHR and Wistar-Kyoto (WKY) control rats of varying ages (4, 8, 12, and 18 months) were mounted in organ baths, and changes in tension were monitored. Inhibition of NO with Nomega-nitro-L-arginine (NOLA) unmasked a slow contraction, which appeared to be age dependent (p < 0.05). This contraction was found in SHRs of all age groups and in older WKY rats. Denuding the endothelium in young SHRs did not influence the constriction, confirming a nonendothelial cell origin, while in the older groups this led to a 30-40% reduction in contraction. Comparable attenuation of the constrictor response was observed after incubation of endothelium intact rings with superoxide dismutase (100 U/ml) or 3-amino-1,2,4-triazole. Of the residual activity that was unaffected by free radical scavengers or de-endothelialization, 60-70% was sensitive to cyclooxygenase inhibition by indomethacin and/or ibuprofen. The thromboxane (TxA ) receptor antagonist SQ29548 induced a complete reversal of the abnormal constriction. In contrast, thromboxane synthetase inhibition had no effect, ruling out any involvement of TxA in mediating this abnormality. Collectively, these observations support the view that as compared with the normotensive setting, contraction induced by NO inhibition in the SHR develops prematurely and deteriorates more rapidly during the aging process. In aged rats, prostaglandin endoperoxide intermediates PGG /H and endothelium-derived free radicals rather than TxA per se appear to contribute to the NOLA-dependent TxA -like vasoconstriction.

The vulnerable plaque and acute coronary syndromes

The interaction between the vulnerable atherosclerotic plaque and thrombus formation, a process referred to as atherothrombosis, is the cornerstone of acute coronary syndromes. Advances in noninvasive imaging have helped to identify novel approaches to plaque stabilization, with the potential to prevent plaque rupture, including lifestyle modification and dietary adjustments, as well as pharmacologic interventions such as statins. Following an acute coronary event, strategies combining mechanical and pharmacologic therapies provide considerable advances in prevention of subsequent cardiac events. Pharmacologic strategies to prevent and treat thrombotic complications related to acute coronary syndromes have been developed to dissolve preformed thrombi and to inhibit thrombogenesis. These regimens focus on inhibiting thrombin, preventing thrombi generation, blocking the initiation of coagulation, inhibiting platelet activation, and increasing fibrinolysis.

Atherosclerosis in type 2 diabetes mellitus and insulin resistance: mechanistic links and therapeutic targets

The ongoing heavy burden of cardiovascular disease associated with diabetes mellitus highlights the failure of current treatment strategies to address effectively the cardiovascular risk profile in such patients. Insulin resistance is not only an underlying feature in most cases of type 2 diabetes, but is also associated, through the Insulin Resistance Syndrome, with cardiovascular risk factors that promote atherothrombosis through diverse mechanisms. Growing evidence suggests that treatment with anti-diabetic agents that improve insulin sensitivity, such as the thiazolidinediones, improve multiple components of the Insulin Resistance Syndrome, have beneficial effects on various atherothrombotic mechanisms, and reduce atherosclerosis in animal models and perhaps humans as well. Given data implicating chronic inflammation as a central feature of atherosclerosis, the anti-inflammatory activity of the thiazolidinediones may contribute to their potential anti-atherosclerotic effects. An improved understanding of the mechanisms linking diabetes, atherosclerosis, and cardiovascular disease is needed in order to understand how these and other current and emerging therapies might reduce diabetes-associated cardiovascular disease.

Cardiovascular toxicities of immunosuppressive agents

Cardiovascular disease is one of the major causes of morbidity and mortality following solid organ transplantation. Many of the current immunosuppressive drugs are associated with an increase of one or more risk factors for the development of atherosclerosis. This review compares the mechanism by which individual immunosuppressive agents may impact on these risk factors and the differential contribution of cyclosporine, tacrolimus, mycophenolate, azathioprine, and Rapamycin to these individual risk factors. Attention to the potential cardiovascular toxicities of individual immunosuppressive agents may help design strategies for maintenance of immunosuppression tailored to individual patients.

Atherosclerosis and cancer: common pathways on the vascular endothelium

This article reviews experimental and clinical data on atherosclerosis and cancer showing common pathogenic mechanisms. It is suggested that common pathways follow dysfunction of the vascular endothelium. The activation of the haemostatic system and the overexpression of cytokines and adhesion molecules by the endothelial cells represent important features of this dysfunction. These mechanisms can be responsible for progression of both diseases and explain the higher incidence of thromboembolic events in cancer patients, the occurrence of similar laboratory findings and the effect of many drugs on the course of the two diseases. Our article confirms that atherosclerosis and cancer share common mechanisms, and we hope it will stimulate further clinical trials on the use of drugs active on the haemostatic system in cancer patients.

Is there a role for endothelin-blockade early after coronary artery bypass grafting?

BACKGROUND

Diverse results exist regarding myocardial release of endothelin after coronary artery bypass grafting. Because endothelin may be involved in regulation of coronary blood flow, postoperative endothelin-blockade could influence the surgical outcome. In this study, we have evaluated the cardiac outflow of endothelin and effects on coronary flow by endothelin-blockade immediately after completion of the coronary bypass grafting.

METHODS

Thirty patients were subjected to infusions of endothelinA blocker (BQ-123, 260 nmoL/min for up to 30 minutes) or endothelinA blocker and endothelinB blocker (BQ-123 and BQ-788, 260 and 250 nmol/min, respectively, for up to 30 minutes) into a veingraft anastomosed to a coronary vessel, and the coronary blood flow was measured. Plasma levels of endothelin from the coronary sinus and the periphery were determined.

RESULTS

There were no significant changes in flow caused by endothelinA blockade alone or in combination with endothelinB blockade. There were no immediately increased levels of endothelin after surgery or after infusions of the endothelin blockers.

CONCLUSIONS

Endothelin blockade does not influence the immediate perioperative myocardial blood flow after coronary bypass grafting. There is no significantly increased myocardial outflow of endothelin, and endothelin does not have any influence on the basal tone of the coronary vessels in the early phase after coronary bypass grafting.

Endothelial and neuronal functions in cerebral and temporal arteries from monkeys fed a high-cholesterol diet

Modifications by hyperlipidemia of endothelium-dependent and -independent relaxations were evaluated in cerebral and temporal arteries from control and hyperlipidemic (high cholesterol-fed) monkeys. Histologically atherosclerotic lesions were not observed in either group. Relaxations induced by histamine, abolished by N(G)-nitro->L-arginine (>L-NA), were significantly potentiated in the hyperlipidemic monkey cerebral arteries, compared with those in the arteries from control monkeys. Treatment with superoxide dismutase did not affect the histamine-induced relaxation. Conversely, endothelium-dependent relaxations induced by A23187, Ca2+ ionophore, in cerebral arteries did not differ between control and hyperlipidemic monkeys. In temporal arteries, relaxations by acetylcholine and A23187 did not differ between control and hyperlipidemic monkeys. Endothelium-dependent and -independent relaxations by adenosine diphosphate in cerebral and temporal arteries were not affected by hyperlipidemia. Endothelium-independent relaxations by exogenously applied nitric oxide did not differ in the arteries from control and hyperlipidemic monkeys. Nicotine-induced relaxations in cerebral arteries, which were mediated with nitric oxide released from nitroxidergic (nitrergic) nerves, and the contractions caused by nicotine in temporal and mesenteric arteries treated with >L-NA did not differ between control and hyperlipidemic monkeys. It is concluded that long exposure to hyperlipidemia did not affect endothelial functions of monkey middle cerebral and temporal arteries but enhanced nitric oxide-mediated relaxations caused by histamine, possibly due to upregulation of endothelial histamine receptor-mediated functions in the cerebral arteries. The nitroxidergic (nitrergic) and adrenergic nerve functions do not seem to be affected by hyperlipidemia.

An attempt to promote neo-vascularization by employing a newly synthesized inhibitor of protein tyrosine phosphatase

Vascular endothelial growth factor (VEGF) and its receptors play a key role in angiogenesis. VEGF receptor-2 (VEGFR-2) has a tyrosine kinase domain, and, once activated, induces the phosphorylation of cytoplasmic signaling proteins. The phosphorylated VEGFR-2 may be a substrate for intracellular protein tyrosine phosphatases (PTPs) which prevent VEGF signaling. We synthesized a series of alpha,alpha-difluoro(phenyl)methylphosphonic acids (DFPMPAs) which inhibit the action of PTP. In this study, we test their effects on VEGF-induced angiogenesis. DFPMPA-3, the most effective inhibitor of human PTP-1B, promoted tube formation by human umbilical vein endothelial cells (HUVEC) on Matrigel more effectively than any other DFPMPAs. The inhibitor promoted the VEGF-induced proliferation and migration of HUVEC by inhibiting the dephosphorylation of VEGFR-2. Its effectiveness was proven through neo-vascularization in mice. The present findings suggest that targeting PTP to promote therapeutic neo-vascularization may be a potential strategy.

Cardiovascular protection by alcohol and polyphenols: role of nitric oxide

Cardiovascular disease, and in particular coronary heart disease (CHD), remains the leading cause of death in both men and women in the United States. Much epidemiologic evidence indicates that alcoholic beverages, and in particular red wine, results in a reduction in cardiovascular risk factors and decreases mortality; however, the mechanisms of this cardiovascular protection remains elusive. This review discusses evidence to suggest that *NO plays a critical role in cardiovascular protection and that nitric oxide synthase (NOS) is the responsible cardioprotective protein (see Bolli et al. 1998. Basic Res. Cardiol. 93: 325-338).

Endothelial progenitor cells for vascular regeneration

The basis for native as well as therapeutic neovascularization is not restricted to angiogenesis but includes postnatal vasculogenesis. Our laboratory and others' have established that bone marrow-derived endothelial progenitor cells (EPCs) are present in the systemic circulation, are augmented in response to certain cytokines and/or tissue ischemia, and home to as well as incorporate into sites of neovascularization. Given the background, EPCs have been investigated as therapeutic agents in these studies of supply-side angiogenesis under pathological as well as physiological conditions. This review discusses the therapeutic potential of EPCs for cardiovascular ischemic diseases.

Robotically assisted versus conventional freehand technique during beating heart anastomoses of left internal thoracic artery to left anterior descending artery

BACKGROUND

Although robotically assisted coronary arterial anastomoses are being performed clinically, the short-term and long-term quality and integrity of the left internal thoracic artery (LITA) to left anterior descending artery (LAD) anastomosis remains unknown. The goal of this study was to perform a histologic and angiographic assessment of porcine beating heart LITA to LAD anastomoses using either robotic assistance or a conventional freehand technique.

METHODS

Twelve pigs underwent beating heart LITA to LAD anastomoses using either the robotically assisted (n = 6) or conventional freehand techniques (n = 6). Quantitative histologic analysis was performed in all animals in order to determine the degree of vascular wall damage. Selective coronary arteriography was performed in all animals immediately after the procedure in order to evaluate anastomotic patency. The unpaired Student's t test was used for all comparisons between groups.

RESULTS

There were no differences in vascular wall damage between the robotically assisted and freehand techniques. Postoperative angiography revealed no stenoses in either group.

CONCLUSIONS

Use of the robotically assisted technique for creation of a LITA to LAD anastomosis was not associated with increased histologic damage when compared with the freehand technique in a beating heart porcine model. Furthermore, there was no difference between the two techniques in postoperative patency rate. These results support further clinical investigation of robotically assisted coronary bypass surgery.

Endothelial progenitor cell vascular endothelial growth factor gene transfer for vascular regeneration

BACKGROUND

Previous studies have established that bone marrow-derived endothelial progenitor cells (EPCs) are present in the systemic circulation. In the current study, we investigated the hypothesis that gene transfer can be used to achieve phenotypic modulation of EPCs.

METHODS AND RESULTS

In vitro, ex vivo murine vascular endothelial growth factor (VEGF) 164 gene transfer augmented EPC proliferative activity and enhanced adhesion and incorporation of EPCs into quiescent as well as activated endothelial cell monolayers. To determine if such phenotypic modulation may facilitate therapeutic neovascularization, heterologous EPCs transduced with adenovirus encoding VEGF were administered to athymic nude mice with hindlimb ischemia; neovascularization and blood flow recovery were both improved, and limb necrosis/autoamputation were reduced by 63.7% in comparison with control animals. The dose of EPCs used for the in vivo experiments was 30 times less than that required in previous trials of EPC transplantation to improve ischemic limb salvage. Necropsy analysis of animals that received DiI-labeled VEGF-transduced EPCs confirmed that enhanced EPC incorporation demonstrated in vitro contributed to in vivo neovascularization as well.

CONCLUSIONS

In vitro, VEGF EPC gene transfer enhances EPC proliferation, adhesion, and incorporation into endothelial cell monolayers. In vivo, gene-modified EPCs facilitate the strategy of cell transplantation to augment naturally impaired neovascularization in an animal model of experimentally induced limb ischemia.