Endothelial Vasomotor Function Research Articles

Transcardiac adiponectin gradient is independently related to endothelial vasomotor function in large and resistance coronary arteries in humans

Adiponectin, an adipocyte-derived protein, has been shown to have vasculoprotective effects. This study examined the possible relationship between coronary vasomotor function and the transcardiac gradient of adiponectin, reflecting adiponectin utilization and/or accumulation in the coronary vascular bed. The epicardial diameter and blood flow response of the left anterior descending coronary artery to intracoronary infusions of ACh was analyzed in 108 consecutive subjects who had a normal coronary angiogram and left ventriculogram. Adiponectin levels were measured by ELISA in plasma obtained from the aortic root (Ao) and the anterior interventricular vein (AIV). Adiponectin levels in the AIV were lower than levels in the Ao. In multivariate linear regression analysis, the transcardiac gradient of adiponectin (Ao - AIV levels) showed a positive correlation with increases in epicardial coronary diameter and coronary blood flow in response to ACh that was independent of traditional coronary risk factors. The transcardiac gradient of adiponectin was not significantly associated with the coronary dilator response to isosorbide dinitrate and the coronary flow response to sodium nitroprusside. In other groups of patients with coronary spastic angina (n = 41) or microvascular angina (n = 32) who had impaired coronary vasomotor responses, there was no significant gradient of adiponectin between the Ao and AIV. The transcardiac gradient of adiponectin may modulate endothelial vasomotor function in large and resistance coronary arteries and may play a role in the pathogenesis of diseases presenting with coronary vasomotor dysfunction.

Endothelial function in HIV-infected persons.

Several reports have suggested an increased risk of coronary disease in human immunodeficiency virus (HIV)-infected patients receiving protease inhibitors (PIs). Impaired endothelium-dependent vasodilation is a putative surrogate marker of coronary atherosclerotic disease. The present study evaluated the effect of HIV infection and antiretroviral treatment on endothelial vasomotor function, by assessing brachial artery flow-mediated dilation (FMD). A total of 75 HIV-infected patients were compared with 223 control subjects who were presumed to be HIV uninfected. HIV-infected patients had significantly impaired FMD, compared with control subjects (mean +/- SD, 7.3% +/- 4.4% vs. 11.1% +/- 6.3%; P < .0001). When adjustments were made for smoking status, sex, and body mass index, the difference between the 2 groups remained statistically significant (P < .01). In a cross-sectional analysis of the HIV-infected patients, we found significant associations between FMD and current injection drug use, hazardous drinking, HIV load, and alpha-high-density lipoprotein triglyceride levels, but not PI therapy. In a multivariate analysis, only current injection drug use and a lower alpha-high-density lipoprotein triglyceride level were significantly associated with FMD. HIV-infected patients have significant impairment of endothelial function, and this impairment is worse among those with elevated levels of HIV replication, particularly injection drug users.

Coronary Endothelial Vasomotor Function and Vascular Remodeling in Heart Transplant Recipients Randomized for Tacrolimus or Cyclosporine Immunosuppression

This study aimed to compare changes in coronary endothelial function, systemic endothelin-1 (ET-1) levels, and vascular remodeling in heart transplant recipients randomized to cyclosporin A (CyA) or tacrolimus (Tac) immunosuppression. Functional endothelial abnormalities and intimal thickening are sensitive measures of early cardiac allograft vasculopathy (CAV). The randomized, prospective study was performed in two groups of 22 patients, maintained on Tac or CyA and mycophenolate mofetil immunosuppression, 1 and 12 months after heart transplantation. We investigated epicardial luminal diameter, coronary blood flow velocity, and ET-1 plasma levels at 1 and 12 months after transplantation. Structural coronary alterations were determined using intravascular ultrasound. Epicardial vasomotor function at baseline and during follow-up was comparable between the groups. Deterioration of microvascular endothelial function during follow-up was significantly enhanced in the CyA versus Tac group (p < 0.05). Circulating ET-1 concentration increased in the CyA group but significantly decreased over time in the Tac group (CyA +17% vs. Tac -25%; p < 0.05). The time-dependent increase in mean intimal area was significantly enhanced in the CyA versus Tac group, whereas the vessel area significantly increased during follow-up in the Tac compared with the CyA group. Epicardial endothelial function is comparable between CyA- and Tac-treated patients. Microvascular endothelial function deteriorates more in CyA-treated patients, a finding that correlates with enhanced ET-1 concentration and an increased intimal area during follow-up. The mean vessel area in the Tac group increased over time, indicating positive vascular remodeling. Tac is superior to CyA with respect to microvascular endothelial function, intimal thickening, and vascular remodeling.

Impact of Coronary Endothelial Function on the Progression of Cardiac Transplant–associated Arteriosclerosis: Effect of Anti-oxidant Vitamins C and E

Excessive vascular oxidant stress has been implicated in cardiac transplant-associated arteriosclerosis (TxAA). In a recent placebo-controlled study of 40 cardiac transplant recipients, vitamin C 500 mg twice a day and vitamin E 400 IU twice a day for 1 year retarded the progression of TxAA, as assessed by intravascular ultrasound (IVUS). Endothelial dysfunction is a key feature of TxAA and reflects oxidant stress. We hypothesized that coronary endothelial dysfunction portends greater TxAA progression and a larger therapeutic response to anti-oxidant vitamins. In this pre-specified analysis, the 40 cardiac transplant recipients were categorized according to normal or abnormal coronary endothelial vasomotor function at baseline, as assessed by acetylcholine (10(-8) to 10(-6) mol/liter). The effect of anti-oxidant vitamins within these two groups of patients was assessed by the change in intimal index over 1 year using IVUS. With placebo (n = 21), the increase in intimal index was greater in the presence vs absence of endothelial dysfunction (11 +/- 3% vs 5 +/- 1%, p < 0.05). Among patients with endothelial dysfunction (n = 21), the intimal index increased 11 +/- 3% with placebo, but decreased -1 +/- 2% with vitamins (p = 0.002). Among patients with normal endothelial function (n = 14), the intimal index increased 5 +/- 1% with placebo and 1 +/- 1% with vitamins (p < 0.05). Endothelial dysfunction indicates rapid TxAA progression, even in the statin era. Although anti-oxidant vitamins reduce disease progression in patients with normal or abnormal endothelial function, the magnitude of benefit is larger in patients with endothelial dysfunction.

Oxidative Stress and Vascular Disease

There is compelling evidence that oxidative stress plays a key role in the pathophysiology of several major cardiovascular diseases. In atherosclerosis, hypertension, stroke, diabetes, and heart failure, expression of superoxide is increased in blood vessels, and endothelial vasomotor function is impaired, presumably caused in large part by inactivation of nitric oxide by superoxide. Endothelial dysfunction is predictive of cardiovascular risk, and probably plays a key role in the pathophysiology of atherosclerosis and its complications. In preliminary studies in hypercholesterolemic mice and in older humans, we have found high levels of superoxide in the aortic valve, as well as aorta. We speculate that superoxide, in addition to playing a key role in atherogenesis, may play a key role in signaling that leads to calcific aortic valvular stenosis. Antioxidant enzymes, especially the three isoforms of superoxide dismutase (SOD), modulate basal levels of superoxide and protect against vasomotor dysfunction. A common gene variant of extracellular SOD (ecSOD) is associated with increased risk of ischemic heart disease. We have made recombinant adenoviruses to examine cardiovascular effects of ecSOD and its heparin-binding domain. This approach might be used to study the almost 500 other proteins with a heparin-binding domain. Finally, several key unanswered questions in relation to oxidative stress and atherosclerosis are raised, and proposed as fruitful areas of research.

Impact of Paraoxonase Polymorphism (Q192R) on Endothelial Function in Intact Coronary Circulation

Paraoxonase-1 (PON1) can protect endothelial function by preventing the oxidation of low-density lipoprotein (LDL) cholesterol and retarding the development of atherosclerosis. We examined whether PON1 polymorphism influences endothelium-dependent coronary vasomotor responses. Sixty-seven patients underwent diagnostic cardiac catheterization, but showed no significant coronary artery stenosis. In all patients, PON1 genotypes (Q/Q, Q/R and R/R) were determined, and provocative testing was performed by the intracoronary administration of graded doses of bradykinin (BK; 0.2, 0.6 and 2.0 mug/min) and acetylcholine (ACh; 3, 10 and 30 mug/min). Coronary blood flow (CBF) was evaluated by a Doppler guide wire. The patients were divided into 2 groups on the basis of ACh testing: one with coronary spastic angina (CSA) and one with non-CSA. The frequencies of the PON1 genotype in the CSA group did not differ significantly from those in the non-CSA group. In the non-CSA group, the patients were subdivided into 2 groups: a group with the Q/Q or Q/R genotypes and a group with the R/R genotype. The vasoconstrictive responses of the epicardial coronary artery to ACh were comparable between the Q/Q + Q/R and R/R groups. Also, the coronary vasodilations induced by BK in the R/R group were similar to those in the QR + QQ group. There were no significant differences in the CBF responses induced by BK or ACh between the Q/Q + Q/R and R/R groups. In conclusion, as estimated by BK and ACh testing, our findings suggest that PON1 genotypes may not play a critical role in the modulation of endothelial vasomotor function in the intact coronary circulation.

Endothelial Vasomotor Function In Women Assessed By Flow-mediated Dilation Before And After A High-fat Meal

Endothelial function is emerging as a surrogate marker for cardiovascular health and may be assessed using a non-invasive technique that employs increased flow and shear stress as a stimulus for brachial artery dilation. Flow-mediated dilation (FMD) is dependent on a healthy endothelium and the production and release of nitric oxide. In the presence of risk factors for CHD, for example chronic hyperlipidemia, FMD is attenuated. Acute hyperlipidemia, elicited by the ingestion of a high-fat meal has also been shown to impair FMD in healthy individuals for several hours. The resultant dysfunction may be due to increased levels of oxidative stress, suggesting that substances with antioxidant properties may protect against postprandial dysfunction. Estrogen has been shown to affect the endothelium causing the rapid release of nitric oxide. Estrogen may also have antioxidant properties. PURPOSE To test the hypothesis that postmenopausal women without hormone therapy would display impaired FMD following a high-fat meal and premenopausal women with endogenous estrogen, along with postmenopausal women with exogenous estrogen, would not display impaired FMD. METHODS Thirty healthy women were studied, 9 premenopausal, 10 postmenopausal with no hormone supplementation and 11 were postmenopausal taking hormone replacement therapy. FMD was measured following 4.5-mins of arterial occlusion including 1-minute of handgrip exercise after a 12-hour fast and again 3-hours after the ingestion of a high-fat meal (1018kcal, 56g of fat). RESULTS Following the high-fat meal FMD remained unaltered (9.39 ± 0.73 vs. 9.75 ± .0.64%, 8.71 ± 0.86 vs. 8.79 ± 0.79%, 9.80 ± 1.16 vs. 9.73 ± 1.06%, p<0.05) despite a significant increase in plasma TG levels (1.11 ± 0.2 vs. 1.91 ± 0.26mmol/L, 1.17 ± 0.15 vs. 1.86 ± 0.28mmol/L, 1.22 ± 0.24 vs. 1.78 ± 0.26mmol/L, p<0.0001 for premenopausal, postmenopausal and hormone replacement groups respectively). The high-fat meal also elicited a significant increase in insulin (9.45 ± 1.34 vs. 39.10 ± 11.32 ± μIU/ml, 8.89 ± 1.17 vs. 32.39 ± 3.17μIU/ml, 7.80 ± 0.81 vs. 32.63 vs. 4.77μIU/ml, p<0.0001). CONCLUSIONS Preserved FMD after a high-fat meal in this study may be explained by the use of healthy active women. Supported by NSERC Canada and the Heart and Stroke Foundation of ON, Canada

Endothelial Vasomotor Function In Women Assessed By Flow-mediated Dilation Before And After A High-fat Meal

Endothelial function is emerging as a surrogate marker for cardiovascular health and may be assessed using a non-invasive technique that employs increased flow and shear stress as a stimulus for brachial artery dilation. Flow-mediated dilation (FMD) is dependent on a healthy endothelium and the production and release of nitric oxide. In the presence of risk factors for CHD, for example chronic hyperlipidemia, FMD is attenuated. Acute hyperlipidemia, elicited by the ingestion of a high-fat meal has also been shown to impair FMD in healthy individuals for several hours. The resultant dysfunction may be due to increased levels of oxidative stress, suggesting that substances with antioxidant properties may protect against postprandial dysfunction. Estrogen has been shown to affect the endothelium causing the rapid release of nitric oxide. Estrogen may also have antioxidant properties. PURPOSE To test the hypothesis that postmenopausal women without hormone therapy would display impaired FMD following a high-fat meal and premenopausal women with endogenous estrogen, along with postmenopausal women with exogenous estrogen, would not display impaired FMD. METHODS Thirty healthy women were studied, 9 premenopausal, 10 postmenopausal with no hormone supplementation and 11 were postmenopausal taking hormone replacement therapy. FMD was measured following 4.5-mins of arterial occlusion including 1-minute of handgrip exercise after a 12-hour fast and again 3-hours after the ingestion of a high-fat meal (1018kcal, 56g of fat). RESULTS Following the high-fat meal FMD remained unaltered (9.39 ± 0.73 vs. 9.75 ± .0.64%, 8.71 ± 0.86 vs. 8.79 ± 0.79%, 9.80 ± 1.16 vs. 9.73 ± 1.06%, p<0.05) despite a significant increase in plasma TG levels (1.11 ± 0.2 vs. 1.91 ± 0.26mmol/L, 1.17 ± 0.15 vs. 1.86 ± 0.28mmol/L, 1.22 ± 0.24 vs. 1.78 ± 0.26mmol/L, p<0.0001 for premenopausal, postmenopausal and hormone replacement groups respectively). The high-fat meal also elicited a significant increase in insulin (9.45 ± 1.34 vs. 39.10 ± 11.32 ± μIU/ml, 8.89 ± 1.17 vs. 32.39 ± 3.17μIU/ml, 7.80 ± 0.81 vs. 32.63 vs. 4.77μIU/ml, p<0.0001). CONCLUSIONS Preserved FMD after a high-fat meal in this study may be explained by the use of healthy active women. Supported by NSERC Canada and the Heart and Stroke Foundation of ON, Canada

Effect of medical and surgical weight loss on endothelial vasomotor function in obese patients

We prospectively examined brachial artery endothelial function using vascular ultrasound in 41 obese subjects treated with medical or surgical (gastric bypass) weight loss interventions. Surgical intervention produced greater weight loss and more pronounced improvement in endothelial function than medical treatment alone. Improved endothelial function with weight loss correlated strongly with fasting glucose but not with alteration in blood pressure, lipids, degree of weight loss, or plasma resistin concentrations. These data demonstrate that weight loss in markedly obese patients improves endothelial function and glycemic control that may represent important mechanisms of the cardiovascular benefit associated with weight reduction.

Hemolysis-Endothelial Dysfunction Syndrome: A Novel Paradigm of Disease Mechanism.

Background: Normal vasomotor tone is maintained by the production of nitric oxide (NO) from endothelial-derived nitric oxide synthase in excess of consumption of NO within the vasculature by intra-erythrocytic hemoglobin. NO reacts up to 600-fold less rapidly when hemoglobin is compartmentalized within the erythrocyte rather than in a cell free form (i.e. cell-free plasma hemoglobin). This implies that during intravascular hemolysis, NO consumption by hemoglobin would be greatly increased. We have proposed that NO consumption and loss of normal vasomotor tone contributes to the pathogenesis of sickle cell disease. However, the increased reactivity of cell-free plasma hemoglobin, released during hemolysis, compared to intra-erythrocytic hemoglobin and the physiologic consequences of hemolysis on nitric oxide consumption have not been definitively proven in vivo.Methods: We have developed a canine model of free water induced intravascular hemolysis to test this mechanism and to examine whether inhaled NO can selectively oxidize the cell free plasma hemoglobin and thus attenuate any associated physiologic changes. Paired experiments were performed in each animal which included a 6-hour control infusion of 5% Dextrose (D5W) followed one week later by a 6-hour infusion of either D5W or free water with or without 80 ppm inhaled NO (full factorial design). Based on pilot experiments, infusions of free water or D5W (control) were administered at a rate of 16 ml/kg/hr. At the end of each experiment, an escalating sodium nitroprusside infusion, a direct NO donor (1 to 27 mcg/kg/min), was administered to evaluate the vascular responsiveness to NO in the presence and absence of hemolysis. In this model, total intravascular hemoglobin concentration remains constant, whereas the ratio of plasma to intracellular hemoglobin concentration increases with hemolysis.Results: In comparison to D5W, free water infusion caused linear increases in plasma hemoglobin (25–50 mM/h) which remained ferrous (FeII) and correlated with increased plasma nitric oxide consumption (R = 0.95; p<0.001). This free water induced intravascular hemolysis caused significant increases in mean systemic arterial pressure (MAP; p=0.0003) and systemic vascular resistance index (SVRI; p=0.0003) and a significant decrease in cardiac index (CI; p=0.02) compared to an equivalent infusion of D5W. In the setting of hemolysis, concurrent inhalation of nitric oxide gas converted the cell free plasma hemoglobin to methemoglobin (50–90% of total plasma hemoglobin), inhibited NO consumption by plasma (methemoglobin does not oxidize NO to nitrate), and normalized hemodynamic parameters. Furthermore, free water induced hemolysis led to blunted hemodynamic effects of sodium nitroprusside on MAP, CI, and SVRI, which were restored with inhaled nitric oxide therapy (p=0.01, p=0.09, and p=0.003 respectively). This further supports the thesis that cell-free plasma hemoglobin consumes NO in the vasculature.Conclusion: These data support the hypothesis that NO scavenging by cell-free plasma hemoglobin disrupts endothelial NO-dependent vasomotor function producing systemic physiologic changes which are attenuated by inhaled nitric oxide therapy. These biochemical and physiological studies support the existence of a hemolysis-endothelial dysfunction syndrome, which may contribute to the vasculopathy of hereditary, acquired and iatrogenic hemolytic states.

Flow-mediated vasodilation and the risk of developing hypertension in healthy postmenopausal women

This study provided the opportunity to assess the relationship between endothelial vasomotor function and incidence of hypertension in a cohort of postmenopausal women. Both menopause and hypertension are associated with endothelial dysfunction and are well-known risk factors for atherosclerotic-related disease. We conducted a prospective cohort study that began in 1996 on 952 apparently healthy postmenopausal women, age 53 +/- 5 years (range 44 to 60 years), with initially normal levels of blood pressure and no history of hypertension. All participants were followed up for a mean period of 3.6 +/- 0.7 years (range 0.5 to 6.9 years). Endothelial function was measured as flow-mediated dilation of the brachial artery using high-resolution ultrasound. During follow-up 112 women developed hypertension. The adjusted relative risk for women with flow-mediated dilation of 3.5 or less (lowest quartile) was 5.77 (95% confidence interval 4.34 to 8.10) versus women with flow-mediated dilation of 5.5 or greater (highest quartile, referent). Each one-unit decrease of flow-mediated dilation was associated with a significant 16% (95% confidence interval 12% to 33%) increase in the multiple-adjusted relative risk of incident hypertension. These prospective data indicate a significant increase in the relative risk of hypertension with each unit decrease of flow-mediated dilation that is independent of age and baseline systolic and diastolic pressure values. This could suggest that an impaired endothelial vasomotor function precedes and predicts the future development of hypertension in postmenopausal women.

Cytomegalovirus infection in heart transplant recipients is associated with impaired endothelial function.

Cardiac allograft vasculopathy (CAV) is initiated by allograft endothelial injury. We hypothesized that a major mechanism by which cytomegalovirus (CMV) could contribute to CAV is by dysregulation of the endothelial vasomotor response. Coronary endothelial vasomotor function was determined in 183 consecutive patients (24+/-33 months after transplantation), and was correlated with recipient and donor CMV serological status before transplantation and with documented CMV infection episodes (CMVpp65Ag+). Serial endothelial function measurements were performed in a subgroup of 53 transplant recipients (1 month and 12 months after transplantation). The composite endpoint of cardiovascular related events and death during a follow-up of 66+/-41 months was analyzed based on the CMV serological status before transplantation. The medium event-free time for CMV-negative recipients of CMV-positive hearts was 8.1 years compared with 13.3 years for the other groups (P<0.05). Distal epicardial but not microvascular endothelial function was significantly impaired in CMV seronegative recipients of seropositive donor hearts (n=48) compared with all other groups (P<0.01 versus seronegative recipient/seronegative donor; P<0.05 versus seropositive recipient/seronegative donor; P<0.05 versus seropositive recipient/seropositive donor). Distal epicardial endothelial dysfunction was more pronounced in heart transplant recipients with a history of documented CMV infection compared with patients without any documented CMV infection (P<0.01). In a longitudinal subgroup analysis, distal epicardial and microcirculatory endothelial vasomotor response deteriorated significantly in recipients with documented CMV infection (P<0.05 versus baseline) but not in patients without previous CMV infection. Documented CMV infection episodes in heart transplant recipients are associated with impaired coronary endothelial function. CMV-negative recipients of CMV-positive donor hearts have an impaired distal epicardial endothelial function and an increased incidence of cardiovascular-related events and death during follow-up. CMV infection may contribute to allograft failure by accelerating coronary endothelial dysfunction.

Transplantation of circulating endothelial progenitor cells restores endothelial function of denuded rabbit carotid arteries.

Circulating endothelial progenitor cells (EPCs) play an important role in repair of injured vascular endothelium and neovascularization. The present study was designed to determine the effect of EPCs transplantation on the regeneration of endothelium and recovery of endothelial function in denuded carotid arteries. Isolated mononuclear cells from rabbit peripheral blood were cultured in endothelial growth medium for 7 days, yielding EPCs. A rabbit model of common carotid artery denudation by passage of a deflated balloon catheter was used to evaluate the effects of EPCs on endothelial regeneration and vasomotor function. Immediately after denudation, autologous EPCs (10(5) cells in 200 microL saline) or 200 microL saline alone (control) were administered into the lumen of injured artery. Four weeks after transplantation, fluorescence-labeled colonies of EPCs were found in the vessel wall. Local transplantation of EPCs as compared with saline administration accelerated endothelialization and significantly improved endothelium-dependent relaxation when assessed 4 weeks after denudation (n=4 to 5, P<0.05). Transplantation of EPCs did not affect vasomotor function of arterial smooth muscle cells. Protein array analysis of conditioned media obtained from cultured EPCs demonstrated the ability of these cells to produce and release a number of proangiogenic cytokines. We conclude that local delivery of cultured circulating EPCs into the lumen of denuded carotid arteries accelerates endothelialization and improves endothelial function. Paracrine effects of EPCs may contribute to regenerative properties of EPCs.

Nitric oxide and the regulation of large artery stiffness: from physiology to pharmacology.

The association between arterial stiffening and aging is well described and can be observed in almost all populations worldwide. A number of other cardiovascular risk factors including diabetes and cigarette smoking are also associated with increased large artery stiffness, often referred to as “premature arterial stiffening.” It is now apparent that the aortic pulse wave velocity (PWV), a measure of arterial distensibility, predicts outcome in a variety of different populations, including hypertensives,1 diabetics,2 individuals with end-stage renal disease (ESRD),3 and even in older adults.4 Indeed, in some populations, aortic PWV is a better predictor of future events than peripheral blood pressure.4 Moreover, arterial stiffening may be more than just a marker of cardiovascular risk; stiffening may also play a more direct role in the development of atherosclerotic plaques. Thus, arterial stiffness would appear to be a novel therapeutic target for the prevention of excess cardiovascular morbidity and mortality. To exploit such an exciting prospect fully, it is necessary to understand the factors regulating arterial stiffness. Traditionally, the stiffness of a vessel was viewed as simply a function of the structural elements of the vessel wall and distending (mean arterial) pressure. However, the large arteries also have a generous coat of smooth muscle, which can alter the distribution of stresses between the elastic and collagenous fibers of the vessel wall and thus alter arterial stiffness. Because smooth muscle tone is influenced by a number of circulating and local vasoactive mediators, arterial stiffness may be actively regulated, and indeed modifiable, at least in the short-term. The muscular arteries have a rich sympathetic innervation, and catecholamines are known to alter smooth muscle tone. Moreover, removal of the vascular endothelium in animals alters large artery stiffness,5,6 suggesting that endothelial-derived substances regulate arterial stiffness in vivo. However, the endothelium …

Reduced basal nitric oxide bioavailability and platelet activation in young spontaneously hypertensive rats

Objective: To investigate the role of basal nitric oxide (NO) bioavailability for platelet activation in young spontaneously hypertensive rats before onset of hypertension. Phosphorylation of the vasodilator-stimulated phosphoprotein (VASP) in platelets was used as a sensitive monitor of in vivo NO bioavailability. Methods and results: Whole blood samples were taken from 10-week-old Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). In vivo surface-expression of P-selectin and platelet-binding of fibrinogen were assessed by flow cytometry. Platelet VASP-phosphorylation at its serine 239 (Ser 239) and serine 157 (Ser 157) residues was assessed using specific antibodies to determine NO bioavailability in vivo, and compared with endothelial vasomotor function. The increment in vascular tone following inhibition of NO-synthase in slightly preconstricted aortic rings was reduced indicating less NO formation under physiological stimulation (WKY 71.1±4.1%; SHR 57.8±2.4%, P<0.05). In vivo platelet VASP-phosphorylation was significantly reduced at both phosphorylation sites in SHR (mean fluorescence for Ser 239: WKY: 15.2±0.6; SHR: 11.7±0.5, P<0.01; Ser 157: WKY: 53.0±3.0; SHR: 35.0±3.5, P<0.05). Surface-expression of P-selectin and membrane-bound fibrinogen were significantly enhanced in SHR compared with WKY (P-selectin: WKY: 23.2±3.4; SHR 58.3±7.9, P<0.001; platelet-bound fibrinogen: WKY: 8.6±0.5; SHR: 13.5±1.1, P<0.001). In vitro preincubation of platelets with the NO donor sodium nitroprusside normalized platelet surface-expression of P-selectin in SHR. Conclusion: Using VASP-phosphorylation as a sensitive monitor of in vivo NO bioavailability, these data provide evidence that reduced vascular NO formation in vivo contributes to increased platelet activation in young SHR.

Hyperhomocysteinemia, Oxidative Stress, and Cerebral Vascular Dysfunction

An elevated circulating concentration of the sulfur-containing amino acid homocysteine, hyperhomocysteinemia, produces complex changes within the blood vessel wall. In the peripheral circulation, these changes include oxidative stress, proinflammatory effects such as expression of tumor necrosis factor-α and inducible nitric oxide (NO) synthase (iNOS), and endothelial dysfunction.1–6 Hyperhomocysteinemia-induced oxidative stress may occur as a result of decreased expression and/or activity of key antioxidant enzymes as well as increased enzymatic generation of superoxide anion (the precursor for multiple reactive oxygen and reactive nitrogen species).2,4 Do hyperhomocysteinemia-induced changes occur in the cerebral circulation and why are they potentially important? Hyperhomocysteinemia is a an emerging risk factor for carotid artery disease (atherosclerosis) and stroke and is associated with Alzheimer’s disease and vascular dementia.7–11 It was not until relatively recently, however, that experimental studies began to define the impact of hyperhomocysteinemia on cerebral vascular biology and the molecular mechanisms that account for these changes. This work has been facilitated by the development of mouse models with genetic alterations in different components of the homocysteine metabolic pathway (see below). Early work in the cerebral microcirculation observed that acute local administration of a very high concentration of homocysteine (1 mmol/L) in the presence of exogenous Cu2+ produced superoxide-mediated reductions in resting cerebral blood flow (CBF) as well as attenuation of endothelium-dependent and NO-mediated responses.12 Our group was among the first to show that mild chronic hyperhomocysteinemia produces endothelial dysfunction in the carotid artery.1,13 Moderate hyperhomocysteinemia, induced by acute methionine loading, …

Long-term effect of combined vitamins e and c on coronary and peripheral endothelial function

ObjectivesWe tested whether long-term administration of antioxidant vitamins C and E improves coronary and brachial artery endothelial function in patients with coronary artery disease (CAD). BackgroundEndothelial function is a sensitive indicator of vascular health. Oxidant stress and oxidized low-density lipoprotein (LDL) impair endothelial function by reducing nitric oxide bioavailability in the artery wall. MethodsWe randomly assigned 30 subjects with CAD to combined vitamin E (800 IU per day) and C (1,000 mg per day) or to placebos in a double-blind trial. Coronary artery endothelial function was measured as the change in coronary artery diameter to acetylcholine infusions (n = 18 patients), and brachial artery endothelial function was assessed by flow-mediated dilation (n = 25 patients) at baseline and six months. Plasma markers of oxidant stress (oxidized LDL and autoantibodies) were also measured. ResultsPlasma alpha-tocopherol (p < 0.001) and ascorbic acid (p < 0.02) increased with active therapy. Compared to placebo, there was no improvement in coronary and brachial endothelial vasomotor function over six months. Although vitamins C and E tended to reduce F2-isoprostanes (p = 0.065), they failed to alter oxidized LDL or autoantibodies to oxidized LDL. ConclusionsLong-term oral vitamins C and E do not improve key mechanisms in the biology of atherosclerosis or endothelial dysfunction, or reduce LDL oxidation in vivo.

Testing endothelial vasomotor function: nitric oxide, a multipotent molecule.

The initial description in 1980 by Furchgott and Zawadzki1 of endothelium-derived vasodilator factor has stimulated more than 2 decades of intense research to delineate the basic biology of the endothelium and its importance in the clinical setting.2 Endothelium-derived vasodilator factor has been identified as nitric oxide (NO).2 It is formed in endothelial cells from the amino acid l-arginine by endothelial isoform of NO synthase (eNOS), which is the product of the NOS3 gene.2,3 In addition to producing NO constitutively, the enzyme may be stimulated to increase NO synthesis by a variety of physiological agonists, shear stress, and pharmacological agents. Although discovered as a vasodilator, NO mediates many of the protective functions of the endothelium.4 It limits vascular recruitment of leukocytes by inhibiting the expression of proinflammatory cytokines, chemokines, and leukocyte adhesion molecules.2,4 It inhibits vascular smooth muscle proliferation and platelet adhesion and aggregation.2,4 NO also inhibits the production of tissue factor, a molecule that plays a critical role in the propensity of disrupted atherosclerotic plaques to cause intravascular thrombosis.5 In the setting of risk factors and experimental atherosclerosis, loss of the biological activity of endothelium-derived NO is accompanied by other alterations in endothelial phenotype that further increase the propensity for vasoconstriction, thrombosis, inflammation, and cellular proliferation in the vascular wall.6 Thus, endothelial dysfunction has the potential to contribute to key events in the course of human atherosclerosis. The experimental observations of Furchgott and others have stimulated translational research to elucidate the importance of endothelium-dependent vasodilation in human coronary atherosclerosis. Accordingly, Ludmer and colleagues7 administered the endothelium-dependent dilator acetylcholine into the coronary arteries of subjects undergoing cardiac catheterization. Acetylcholine induced dilation of normal epicardial coronary arteries but induced abnormal vasoconstriction, indicative of endothelial dysfunction, in patients with angiographic evidence of …

Impact of peripheral endothelial vasomotor function on exercise capacity and adhesion molecules in idiopathic dilated cardiomyopathy

Impact of peripheral endothelial vasomotor function on exercise capacity and adhesion molecules in idiopathic dilated cardiomyopathy

726 Impaired endothelial vasomotor function in angiographically normal artery after acute coronary syndrom: a transient phenomenon influence by hs-C-reactive protein and high-density lipoprotein cholesterol levels

726 Impaired endothelial vasomotor function in angiographically normal artery after acute coronary syndrom: a transient phenomenon influence by hs-C-reactive protein and high-density lipoprotein cholesterol levels