Endothelium-independent Dilation Research Articles

Extended-release niacin/laropiprant improves endothelial function in patients after myocardial infarction

Raising high-density lipoprotein cholesterol (HDL-C) is an important strategy for reducing residual cardiovascular risk. In the present study, we sought to assess the effect of extended-release niacin/laropiprant on endothelial function in patients after a myocardial infarction with target low-density lipoprotein cholesterol (LDL-C). In this double-blind, placebo-controlled trial, 63 men (35-60 years of age) after a myocardial infarction were randomized to either niacin/laropiprant (1000/20 mg daily for 4 weeks and 2000/40 mg daily thereafter) or placebo. Flow-mediated dilation (FMD) and nitroglycerin-induced (GTN) dilation of the brachial artery, total cholesterol (TC), LDL-C, HDL-C, triglycerides (TG), lipoprotein(a) [Lp(a)], and apolipoprotein (Apo) A1/B were measured at baseline and after 12 weeks of intervention. FMD significantly increased (from 3.9 ± 5.1 to 9.8 ± 4.4%, p < 0.001) in the niacin/laropiprant group, but not in the placebo group (4.6 ± 4.4 to 6.1 ± 4.4%, p = 0.16) (p = 0.02 for comparison of interventions). GTN dilation also increased in the niacin/laropiprant group (from 12.5 ± 6.1 to 16.7 ± 4.8%, p = 0.02), but not in the placebo group (13.4 ± 5.0 to 15.1 ± 5.2%, p = 0.18), (p = 0.60 for comparison of interventions). Niacin/laropiprant reduced TC and LDL-C (p = 0.05 for both) and increased HDL-C (p < 0.001) without influencing TG, with no changes in the placebo group. Lp(a) (p = 0.026) and ApoB (p = 0.014) were significantly lower in the niacin/laropiprant group, with no difference in the placebo group. ApoA1 did not change in either of the groups (p = 0.13; p = 0.26). FMD and GTN dilation improvements did not correlate with changes in the lipid profile. Niacin/laropiprant improves endothelium-dependent and endothelium-independent dilation of the brachial artery. This improvement does not correlate with changes in lipid parameters.

Non-cancer atherosclerotic effects associated with environmental and therapeutic radiation doses: The Chernobyl thyroid cancer children study

The Chernobyl disaster, which took place on April 26th 1986 at the nuclear plant in northern Ukraine, represents the largest everhappened nuclear accident. About fivemillion people were exposed to radioactive contamination in Belarus, Russian Federation and Ukraine, with an estimated individual radiation dose ranging from few mSv to some hundred mSv [1]. The main health effect observed was an increase in the incidence of thyroid cancer in the young, but a number of non-cancer end points have been reported [2]. Recently, studies on the atomic bomb survivors in Japan demonstrated that moderate doses of ionizing radiations may contribute to excess cardiovascular disease risk [3], as confirmed also by a metaanalysis [4]. However, cardiovascular effects of low–moderate doses are still largely unexplored [5]. The aim of the present study was to assess the proatherosclerotic effects of radiation exposure in survivors of Chernobyl disaster, subsequently diagnosed with papillary thyroid cancer and treated with radioiodine ablation. Forty-six volunteers were enrolled: 23 subjects who were children (≤8 years old) living in the Chernobyl area in Belarus at the time of the nuclear blast in 1986 (group E-exposed), subsequently diagnosed and treated with radioiodine ablation for papillary thyroid cancer; 23 nonexposed (NE) healthy subjects, matched with E for age, gender and cardiovascular risk factors. All subjects underwent carotid intima–media thickness assessment (CIMT), aortic and carotid stiffnessmeasurement, andperipheral blood testing forEPCevaluation. In a subset of 28 subjects (14 subjects from each group), endothelial function was assessed by brachial artery flow-mediated dilation (FMD). A volume of 100 μL peripheral blood was immunostained with the following monoclonal antibodies: PERcP-conjugated human antiCD34, fluorescein-conjugated human anti-kinase insert domain receptor (KDR), human anti-CD133, or isotype control, and then analyzed by flow-cytometry. Carotid–femoral pulse wave velocity (PWV) was performed (SphygmoCor, AtCor Medical, Sydney, Australia) [6]. Common carotid artery ultrasound scans analyzed by means of Carotid Studio (Cardiovascular Suite; Quipu srl, Pisa, Italy), an algorithm for the automatic evaluation of the instantaneous carotid diameter, CIMT, distensibility coefficient and stiffness [7]. Non-invasive ultrasound assessment of brachial endothelial function was performed as previously described [6]. An automated system for real-time detection of brachial artery diameter by analysis of B-mode ultrasound image sequences was used (FMD Studio, Cardiovascular Suite: Quipu srl, Pisa, Italy). Endothelium-dependent dilation was induced by reactive hyperemia following a 5-min forearm cuff occlusion at 300 mm Hg. Endothelium-independent dilation was obtained by sublingual administration of 25 μg glyceryl-trinitrate (GTN). The baseline characteristics of the study participants are given in Table 1. In E mean total radiation dose was 47.3 ± 16.1 mCi (range 30–200 mCi). All E subjects were treated with L-thyroxin: their median TSH was 0.018 μg/mL (25–75 percentile: 0.007–0.462). Subpopulations of putative EPCs (CD34 + KDR+, CD34+ CD133+, CD34 + CD133 + KDR+) expressed as cell numbers per 10 cytometric events, were significantly decreased in E group when compared to NE group (Table 2, Fig. 1). E and NE presented similar carotid diameter, CIMT, distensibility and stiffness, as well as similar carotid–femoral PWV (Table 2). PP amplification from carotid to brachial site was significantly higher in E than in NE even after considering age, height and heart rate as covariates (P = 0.04). Carotid AIx was also higher in E than in NE (Table 2). E and NE showed similar brachial artery diameter, absolute and percent hyperemic change in diameter and shear rate, whereas in E response to GTN was significantly greater than in NE (Table 2). Themain result of this study is that in a group of young survivors of the Chernobyl nuclear disaster, subsequently treated with radioiodine ablation for thyroid cancer, the number of EPCs was significantly reduced in comparison to healthy volunteers, suggesting a reduced endothelial regeneration and repair capacity. This selective alteration, International Journal of Cardiology 168 (2013) 4255–4592

Pulmonary Cerium Dioxide Nanoparticle Exposure Differentially Impairs Coronary and Mesenteric Arteriolar Reactivity

Cerium dioxide nanoparticles (CeO2 NPs) are an engineered nanomaterial (ENM) that possesses unique catalytic, oxidative, and reductive properties. Currently, CeO2 NPs are being used as a fuel catalyst but these properties are also utilized in the development of potential drug treatments for radiation and stroke protection. These uses of CeO2 NPs present a risk for human exposure; however, to date, no studies have investigated the effects of CeO2 NPs on the microcirculation following pulmonary exposure. Previous studies in our laboratory with other nanomaterials have shown impairments in normal microvascular function after pulmonary exposures. Therefore, we predicted that CeO2 NP exposure would cause microvascular dysfunction that is dependent on the tissue bed and dose. Twenty-four-hour post-exposure to CeO2 NPs (0-400μg), mesenteric, and coronary arterioles was isolated and microvascular function was assessed. Our results provided evidence that pulmonary CeO2 NP exposure impairs endothelium-dependent and endothelium-independent arteriolar dilation in a dose-dependent manner. The CeO2 NP exposure dose which causes a 50% impairment in arteriolar function (EC50) was calculated and ranged from 15 to 100μg depending on the chemical agonist and microvascular bed. Microvascular assessments with acetylcholine revealed a 33-75% reduction in function following exposure. Additionally, there was a greater sensitivity to CeO2 NP exposure in the mesenteric microvasculature due to the 40% decrease in the calculated EC50 compared to the coronary microvasculature EC50. CeO2 NP exposure increased mean arterial pressure in some groups. Taken together, these observed microvascular changes may likely have detrimental effects on local blood flow regulation and contribute to cardiovascular dysfunction associated with particle exposure.

Abstract 72: Vascular and Cardiac Effects of Inducible Nitric Oxide Synthase in Hyperhomocysteinemic Mice

Background Diet-induced hyperhomocysteinemia (HHcy) produces endothelial and cardiac dysfunction and promotes thrombosis through a mechanism proposed to involve oxidative stress. Inducible nitric oxide synthase (iNOS) is upregulated in HHcy and can generate oxidants such as superoxide. We tested the hypothesis that iNOS mediates the adverse oxidative vascular, thrombotic, and cardiac effects of HHcy. Methods Mice deficient in iNOS ( Nos2-/ -) and their wild-type (WT) littermates were fed either a control (C) diet or a high methionine/low folate (HM/LF) diet for 3-6 months. Vasomotor function was assessed in cerebral arterioles in response to the endothelium-dependent dilator acetylcholine or the endothelium-independent dilator nitroprusside. Thrombotic occlusion of the carotid artery was measured in response to photochemical injury (rose bengal). Regional myocardial injury was measured after 30 minutes of ischemia and 2 hours of reperfusion of the left coronary artery. Results Nos2 -/- and WT mice fed the HM/LF diet developed similar levels of HHcy, with a 2-fold increase in plasma total homocysteine (P&lt;0.001 vs. C diet). As expected, WT mice with HHcy exhibited endothelial dysfunction, with impaired dilatation to acetylcholine but not nitroprusside, and enhanced susceptibility to thrombosis, with shortened times to occlusion of the carotid artery (P&lt;0.05 vs. C diet). Interestingly, deficiency of iNOS resulted in decreased, rather than increased dilatation responses to acetylcholine (P&lt;0.05 vs. WT mice). Nos2 -/- mice also exhibited shortened times to thrombotic occlusion in mice fed the C diet (P&lt;0.05 vs. WT mice) and failed to protect from endothelial dysfunction or accelerated thrombosis in mice fed the HM/LF diet. Deficiency of iNOS did not alter myocardial infarct size in mice fed the C diet but significantly increased infarct size and cardiac superoxide production in mice fed the HM/LF diet (P&lt;0.05 vs. WT mice). Conclusions These findings suggest that endogenous iNOS protects from, rather than exacerbates, endothelial dysfunction, thrombosis, and myocardial ischemia-reperfusion injury. In the setting of HHcy, iNOS appears to function to blunt cardiac oxidative stress rather than as a source of superoxide.

Reduced angiotensin II levels cause generalized vascular dysfunction via oxidant stress in hamster cheek pouch arterioles

ObjectivesWe investigated the effect of suppressing plasma angiotensin II (ANG II) levels on arteriolar relaxation in the hamster cheek pouch. MethodsArteriolar diameters were measured via television microscopy during short-term (3–6days) high salt (HS; 4% NaCl) diet and angiotensin converting enzyme (ACE) inhibition with captopril (100mg/kg/day). ResultsACE inhibition and/or HS diet eliminated endothelium-dependent arteriolar dilation to acetylcholine, endothelium-independent dilation to the NO donor sodium nitroprusside, the prostacyclin analogs carbacyclin and iloprost, and the KATP channel opener cromakalim; and eliminated arteriolar constriction during KATP channel blockade with glibenclamide. Scavenging of superoxide radicals and low dose ANG II infusion (25ng/kg/min, subcutaneous) reduced oxidant stress and restored arteriolar dilation in arterioles of HS-fed hamsters. Vasoconstriction to topically-applied ANG II was unaffected by HS diet while arteriolar responses to elevation of superfusion solution PO2 were unaffected (5% O2, 10% O2) or reduced (21% O2) by HS diet. ConclusionsThese findings indicate that sustained exposure to low levels of circulating ANG II leads to widespread dysfunction in endothelium-dependent and independent vascular relaxation mechanisms in cheek pouch arterioles by increasing vascular oxidant stress, but does not potentiate O2- or ANG II-induced constriction of arterioles in the distal microcirculation of normotensive hamsters.

The Relationship Between Artery Stiffness and Left Ventricular Diastolic Function in Patients With Multiple Cardiovascular Risks

To evaluate the relationship between artery stiffness and left ventricular diastolic function. A total of 79 patients with multiple cardiovascular risks were recruited and divided into two groups according to the value of E/Em: diastolic dysfunctional group (E/Em≧10, n=25) and control group (E/Em<10, n=54). The arterial stiffness parameters of carotid artery and endothelium-independent dilation (EID) of brachial artery were evaluated by ET for two groups. The arterial stiffness parameters of carotid artery and EID of brachial artery in diastolic dysfunctional group were higher than that in controls (p > 0.05), and were associated to diastolic function parameters of left ventricular (p < 0.05). The arterial stiffness is closely related to the diastolic function of left ventricular, and maybe an important factor to impact on it. The increased arterial stiffness is useful in predicting left ventricular diastolic dysfunction in patients with multiple cardiovascular risks.

Aging impairs PI3K/Akt signaling and NO-mediated dilation in soleus muscle feed arteries

We tested the hypothesis that impaired nitric oxide (NO)-mediated, endothelium-dependent dilation in aged soleus muscle feed arteries (SFA) is due to an age-related decline in the potential for PI3-kinase (PI3K)/protein kinase B (Akt)-dependent phosphorylation of endothelial NO synthase (eNOS) on serine residue 1177 (p-eNOS(ser1177)). SFA from young (4 months) and old (24 months) Fischer 344 rats were cannulated for examination of endothelium-dependent [flow or acetylcholine (ACh)] and endothelium-independent [sodium nitroprusside (SNP)] vasodilator function. To determine the mechanism by which aging affected vasodilation to flow and ACh, vasodilator responses were assessed in the presence of N (ω)-nitro-L-arginine (L-NNA, to inhibit NOS), LY-294002 (to inhibit PI3K), or 1L6-hydroxymethyl-chiro-inositol-2-(R)-2-O-methyl-3-O-octadecyl-sn-glycerocarbonate (AktI, to inhibit Akt). Flow- and ACh-induced vasodilator responses were significantly impaired in old SFA, whereas endothelium-independent dilation to SNP was not compromised. Age-group differences in flow- and ACh-induced dilations were abolished in the presence of L-NNA, LY-294002, or AktI. In a separate experiment, SFA were cannulated and stimulated with ACh (10(-4) M, 3 min), flow (60 μl/min, 5 min), or remained unstimulated (3 min). SFA were removed from the pipettes and immunoblot analysis was used to assess ACh- and flow-stimulated phosphorylation of eNOS on ser(1177). Stimulation with ACh or flow increased phosphorylation of eNOS on ser(1177) in young (not old) SFA. Preincubation of young SFA with LY-294002, abolished the ACh-induced phosphorylation of eNOS in young SFA. Collectively, these results indicate that impaired NO-mediated, endothelium-dependent dilation in old SFA is due, in part, to an impaired potential for PI3K/Akt-dependent phosphorylation of eNOS on ser(1177).

Chronic Depressive Symptoms and Gender: Impact on Conduit Vascular Outcomes

Chronic depressive symptoms have become recognized as independent risk factors for vascular disease, we investigated the impact of chronic stress/depressive symptoms on vascular outcomes between genders using an establish model from behavioral research. Male and female mice were exposed to 8 weeks of unpredictable chronic mild stress (UCMS; e.g., wet bedding, predator sound/smell, random disruption of light/dark cycle) and indexes of depressive behavior (e.g., coat status, grooming, mobility) were exacerbated in females vs. males. However, dilator responses to methacholine were more strongly impaired in aortic rings of UCMS males than females (p&lt;0.05). NOS inhibition was without effect in UCMS males, while blunting reactivity in UCMS females (p&lt;0.05). COX inhibition impaired dilator responses of UCMS males, but only affected UCMS females at higher concentrations of methacholine. Combined NOS/COX blockade abolished methacholine reactivity. Endothelium‐independent dilator responses were not different across all groups. These results suggest that UCMS impairs vascular function, the severity of which is gender‐dependent. The severity of induced depressive symptoms was not indicative of poorer vascular outcomes. In conclusion, while female mice exhibited increased susceptibility to UCMS‐induced depressive symptoms, they maintained superior vascular function versus male counterparts.

Air Pollution Particulate Matter Collected from an Appalachian Mountaintop Mining Site Induces Microvascular Dysfunction

Air pollution PM is associated with cardiovascular morbidity and mortality. In Appalachia, PM from mining may represent a health burden to this sensitive population that leads the nation in cardiovascular disease, among others. Cardiovascular consequences following inhalation of PM(MTM) are unclear, but must be identified to establish causal effects. PM was collected within 1 mile of an active MTM site in southern WV. The PM was extracted and was primarily <10 μm in diameter (PM10), consisting largely of sulfur (38%) and silica (24%). Adult male rats were IT with 300 μg PM(MTM) . Twenty-four hours following exposure, rats were prepared for intravital microscopy, or isolated arteriole experiments. PM(MTM) exposure blunted endothelium-dependent dilation in mesenteric and coronary arterioles by 26%, and 25%, respectively, as well as endothelium-independent dilation. In vivo, PM(MTM) exposure inhibited endothelium-dependent arteriolar dilation (60% reduction). α-adrenergic receptor blockade inhibited PVNS-induced vasoconstriction in exposed animals compared with sham. These data suggest that PM(MTM) exposure impairs microvascular function in disparate microvascular beds, through alterations in NO-mediated dilation and sympathetic nerve influences. Microvascular dysfunction may contribute to cardiovascular disease in regions with MTM sites.

Impaired endothelial function in lone atrial fibrillation

Impaired endothelial function has been previously documented in patients with atrial fibrillation (AF) and underlying comorbidities or older patients with idiopathic AF. The aim of this study was to evaluate systemic endothelial function in younger AF patients (less than < 60 years old) with lone AF (that is, without associated cardiopulmonary comorbidities, including arterial hypertension), by comparing brachial artery flow-mediated dilation (FMD) in lone AF patients with FMD of healthy subjects in sinus rhythm. Two groups of participants were prospectively enrolled. The first group comprised of 38 AF patients (the mean age 45 +/- 11 years, 68% male) with persistent (> 7 days) lone AF. The second group comprised of 28 healthy controls in sinus rhythm (the mean age 43 +/- 13, 53% male), matched by age, gender and atherosclerotic risk factors. All the participants underwent physical examination, laboratory analysis [including determination of C-reactive protein (CRP)], standard echocardiography and exercise-stress testing. Brachial artery FMD and endothelium independent dilation (NMD) were assessed with a high-resolution ultrasound probe and arterial diameters taken from 5 consecutive cardiac cycles were averaged for each measurement to accommodate to beat-to-beat flow variations in AF. There were no differences between the 2 groups regarding age, gender and most clinical, laboratory and echocardiographic characteristics (all p > 0.05), apart from the increased heart rate (p = 0.018), body mass index (p = 0.027), CRP levels (p = 0.007) and left atrial anteroposterior dimension (p < 0.001) in AF patients. FMD of AF patients [median value 5.0%, interquartile range (IQR) 2.87%-7.50%] was significantly lower (p < 0.001) than FMD of healthy controls (median value 8.85%, IQR 5.80%-12.50%), whereas there were no differences in median NMD values (p > 0.05). In the multivariate analysis, the independent FMD determinants in our study population were the presence of AF, smoking and total cholesterol levels (all p < 0.001). In patients with AF, the strongest independent FMD determinant was arrhythmia duration (p < 0.001), followed by smoking (p = 0.013) and total cholesterol levels (p = 0.045). Our findings confirm that sustained AF is associated with systemic endothelial dysfunction even in relatively young patients with no cardiovascular disorders or risk factors. AF is an independent contributor to lower FMD and a prolonged arrhythmia duration may confer the risk for more profound endothelial damage.

Extracellular but not cytosolic superoxide dismutase protects against oxidant-mediated endothelial dysfunction

Superoxide (O2•−) contributes to the development of cardiovascular disease. Generation of O2•− occurs in both the intracellular and extracellular compartments. We hypothesized that the gene transfer of cytosolic superoxide dismutase (SOD1) or extracellular SOD (SOD3) to blood vessels would differentially protect against O2•−-mediated endothelial-dependent dysfunction. Aortic ring segments from New Zealand rabbits were incubated with adenovirus (Ad) containing the gene for Escherichia coli β-galactosidase, SOD1, or SOD3. Activity assays confirmed functional overexpression of both SOD3 and SOD1 isoforms in aorta 24h following gene transfer. Histochemical staining for β-galactosidase showed gene transfer occurred in the endothelium and adventitia. Next, vessels were prepared for measurement of isometric tension in Kreb's buffer containing xanthine. After precontraction with phenylephrine, xanthine oxidase impaired relaxation to the endothelium-dependent dilator acetylcholine (ACh, max relaxation 33±4% with XO vs. 64±3% without XO, p<0.05), whereas relaxation to the endothelium-independent dilator sodium nitroprusside was unaffected. In the presence of XO, maximal relaxation to ACh was improved in vessels incubated with AdSOD3 (55±2%, p<0.05 vs. control) but not AdSOD1 (34±4%). We conclude that adenoviral-mediated gene transfer of SOD3, but not SOD1, protects the aorta from xanthine/XO-mediated endothelial dysfunction. These data provide important insight into the location and enzymatic source of O2•− production in vascular disease.

Endothelial function in women using levonorgestrel-releasing intrauterine system (LNG-IUS)

BackgroundOral levonorgestrel has been linked to increased cardiovascular risk, but currently, no information is available on the effect of the levonorgestrel-releasing intrauterine system (LNG-IUS) on endothelial dysfunction. The objective of this study was to assess endothelial function in LNG-IUS users. Study DesignSixty women underwent insertion of either an LNG-IUS (n=30) as study group or Copper-T intrauterine contraceptive device (TCu 380A intrauterine device) as control group (n=30). In the midluteal phase of menstrual cycle, endothelium-dependent flow-mediated dilatation (FMD) and endothelium-independent dilatation of brachial artery were studied before and after 3, 6 and 12 months of device insertion. We also assessed the correlation of FMD and serum concentrations of estradiol (E2), progesterone (P) and LNG. ResultsWith LNG-IUS, there was a nonsignificant decrease in mean FMD of brachial artery (p>.05) compared with the control group at different time points of the study. Before LNG-IUS, reactive hyperemia caused an 8.3%±1.3% increase in brachial artery diameter compared with 7.1%±1.1%, 7.4%±0.9% and 7.5%±0.9% after 3, 6 and 12 months of LNG-IUS (p>.05). The mean±SD LNG plasma levels at 3, 6 and 12 months of LNG-IUS application were 228±87, 204±94 and 191±79 pg/mL, respectively. E2 levels were comparable in women of both studied groups. Mean P levels were significantly lower after LNG-IUS insertion compared with before device insertion and with the control group (p<.05) at all study visits. No correlation was found between LNG levels and FMD. ConclusionsA nonsignificant change detected in endothelial function in LNG-IUS indicates that it has no increased cardiovascular risk.

Simvastatin reduces sympathetic outflow and augments endothelium-independent dilation in non-hyperlipidaemic primary hypertension

ObjectivesPrevious reports, involving hypercholesterolaemic hypertensive subjects, that statins reduce muscle sympathetic nerve activity (MSNA) did not investigate potential neural sites of such sympathoinhibition or determine its consequences for endothelial function...

Fenofibrate Improves Vascular Endothelial Function by Reducing Oxidative Stress While Increasing Endothelial Nitric Oxide Synthase in Healthy Normolipidemic Older Adults

Vascular endothelial dysfunction develops with aging, as indicated by impaired endothelium-dependent dilation, and is related to increased cardiovascular disease risk. We hypothesized that short-term treatment with fenofibrate, a lipid-lowering agent with potential pleiotropic effects, would improve endothelium-dependent dilation in middle-aged and older normolipidemic adults by reducing oxidative stress. Brachial artery flow-mediated dilation, a measure of endothelium-dependent dilation, was assessed in 22 healthy adults aged 50 to 77 years before and after 7 days of fenofibrate (145 mg/d; n=12) or placebo (n=10). Brachial flow-mediated dilation was unchanged with placebo, but improved after 2 and 7 days of fenofibrate (5.1±0.7 versus 2 days: 6.0±0.7 and 7 days: 6.4±0.6%δ; both P &lt;0.005). The improvements in flow-mediated dilation after 7 days remained significant ( P &lt;0.05) after accounting for modest changes in plasma total and low-density lipoprotein cholesterol. Endothelium-independent dilation was not affected by fenofibrate or placebo ( P &gt;0.05). Intravenous infusion of the antioxidant vitamin C improved brachial flow-mediated dilation at baseline in both groups and during placebo treatment ( P &lt;0.05), but not after 2 and 7 days of fenofibrate ( P &gt;0.05). Fenofibrate treatment also reduced plasma-oxidized low-density lipoprotein, a systemic marker of oxidative stress, compared with placebo ( P &lt;0.05). In vascular endothelial cells sampled from peripheral veins of the subjects, endothelial nitric oxide synthase protein expression was unchanged with placebo and after 2 days of fenofibrate, but was increased after 7 days of fenofibrate (0.54±0.03 versus 2 days: 0.52±0.04 and 7 days: 0.76±0.11 intensity/human umbilical vein endothelial cell control; P &lt;0.05, 7 days). Short-term treatment with fenofibrate improves vascular endothelial function in healthy normolipidemic middle-aged and older adults by reducing oxidative stress and induces an increase in endothelial nitric oxide synthase.

Regular aerobic exercise protects against impaired fasting plasma glucose-associated vascular endothelial dysfunction with aging

In the present study, we tested the hypothesis that age-associated vascular endothelial dysfunction is exacerbated by IFG (impaired fasting plasma glucose) and that regular aerobic exercise prevents this effect. Data were analysed from a cohort of 131 non-smoking men and women without overt clinical disease. Compared with young adult controls (age=24±1 years, n=29; values are means±S.E.M.), brachial artery FMD (flow-mediated dilation), a measure of conduit artery EDD (endothelium-dependent dilation), was 33% lower [7.93±0.33 against 5.27±0.37%Δ (% change), P<0.05] in MA/O (middle-aged/older) adults with NFG (normal fasting plasma glucose) (≤99 mg/dl, 62±1 years, n=35). In MA/O adults with IFG (100-125 mg/dl, 64±1 years, n=28), FMD was 30% lower (3.37±0.35%Δ) than in their peers with NFG and 58% lower than young controls (P<0.05). Brachial artery FMD was greater (6.38±0.35%Δ) in MA/O adults with NFG who regularly performed aerobic exercise (>45 min/day for ≥5 days/week, 62±1 years, n=23) compared with their non-exercising peers and only slightly less than young controls (P<0.05). Most importantly, FMD was completely preserved in MA/O adults with IFG who regularly performed aerobic exercise (6.99±0.69%Δ, 65±1 years, n=16). In the pooled sample, fasting plasma glucose was inversely related to FMD (r=-0.42, P<0.01) and was the strongest independent predictor of FMD (R(2)=0.32). Group differences in FMD were not affected by other subject characteristics or brachial artery properties, including brachial artery dilation to sublingual NTG (nitroglycerine, i.e. endothelium-independent dilation). IFG exacerbates age-associated vascular endothelial dysfunction and this adverse effect is completely prevented in MA/O adults who regularly perform aerobic exercise.

Dietary Sodium Restriction Reverses Vascular Endothelial Dysfunction in Middle-Aged/Older Adults With Moderately Elevated Systolic Blood Pressure

This study sought to determine the efficacy of dietary sodium restriction (DSR) for improving vascular endothelial dysfunction in middle-aged/older adults with moderately elevated systolic blood pressure (SBP) (130-159 mm Hg) and the associated physiological mechanisms. Vascular endothelial dysfunction develops with advancing age and elevated SBP, contributing to increased cardiovascular risk. DSR lowers BP, but its effect on vascular endothelial function and mechanisms involved are unknown. Seventeen subjects (11 men and 6 women; mean age, 62 ± 7 years) completed a, randomized crossover study of 4 weeks of both low (DSR) and normal sodium intake. Vascular endothelial function (endothelium-dependent dilation; EDD), nitric oxide (NO)/tetrahydrobiopterin (BH(4)) bioavailability, and oxidative stress-associated mechanisms were assessed following each condition. Urinary sodium excretion was reduced by ≈ 50% (to 70 ± 30 mmol/day), and conduit (brachial artery flow-mediated dilation [FMD(BA)]) and resistance (forearm blood flow responses to acetylcholine [FBF(ACh)]) artery EDD were 68% and 42% (peak FBF(ACh)) higher following DSR (p < 0.005). Low sodium markedly enhanced NO-mediated EDD (greater ΔFBF(ACh) with endothelial NO synthase inhibition) without changing endothelial NO synthase expression/activation (Ser 1177 phosphorylation), restored BH(4) bioactivity (less ΔFMD(BA) with acute BH(4)), abolished tonic superoxide suppression of EDD (less ΔFMD(BA) and ΔFBF(ACh) with ascorbic acid infusion), and increased circulating superoxide dismutase activity (all p < 0.05). These effects were independent of ΔSBP. Other subject characteristics/dietary factors and endothelium-independent dilation were unchanged. DSR largely reversed both macro- and microvascular endothelial dysfunction by enhancing NO and BH(4) bioavailability and reducing oxidative stress. Our findings support the emerging concept that DSR induces "vascular protection" beyond that attributable to its BP-lowering effects.

Impaired Role of Epoxyeicosatrienoic Acids in the Regulation of Basal Conduit Artery Diameter During Essential Hypertension

In young healthy subjects, epoxyeicosatrienoic acids synthesized by endothelial cytochrome P450 epoxygenases maintain basal conduit artery diameter during altered NO availability. Whether this compensatory mechanism is effective during essential hypertension is unknown. Radial artery diameter, blood flow, and mean wall shear stress were determined in 14 nontreated essential hypertensive patients and 14 normotensive control subjects during 8 minutes of brachial infusion for inhibitors of cytochrome P450 epoxygenases (fluconazole, 0.4 µmol/min) and NO synthase (N(G)-monomethyl-L-arginine, 8 µmol/min) alone and in combination. In controls, the radial artery diameter was reduced by fluconazole (-0.034 ± 0.012 mm) and N(G)-monomethyl-L-arginine (-0.037 ± 0.010 mm) and to a larger extent by their combination (-0.137 ± 0.011 mm), demonstrating a synergic effect. In contrast, the radial diameter in hypertensive patients was not affected by fluconazole (0.010 ± 0.014 mm) but was reduced by N(G)-monomethyl-L-arginine (-0.091 ± 0.008 mm) to a larger extent than in controls. In parallel, N(G)-monomethyl-L-arginine decreased local plasma nitrite to a lesser extent in hypertensive patients (-14 ± 5 nmol/L) than in controls (-50 ± 10 nmol/L). Moreover, the addition of fluconazole to N(G)-monomethyl-L-arginine did not further decrease radial diameter in patients (-0.086 ± 0.011 mm). Accordingly, fluconazole significantly decreased local epoxyeicosatrienoic acid plasma level in controls (-2.0 ± 0.6 ng/mL) but not in patients (-0.9 ± 0.4 ng/mL). Inhibitors effects on blood flow and endothelium-independent dilatation to sodium nitroprusside were similar between groups. These results show that, in contrast to normotensive subjects, epoxyeicosatrienoic acids did not contribute to the regulation of basal conduit artery diameter and did not compensate for altered NO availability to maintain this diameter in essential hypertensive patients.

Effect of unilateral forearm inactivity on endothelium-dependent vasodilator function in humans

Exercise training is associated with rapid changes in endothelium-dependent vasodilation, which occur within days of training. Whilst long-term physical inactivity has potent effects on vascular structure, little is known about the immediate impact of inactivity on vascular function. Aim of this study was to measure vascular function before, during (day 4) and after 8 days of unilateral forearm inactivity. Thirteen healthy male subjects (22 ± 1 years) were instructed to wear a sling on the non-dominant arm to induce local inactivity. Before, during (at 4 days) and after the 8-day intervention, we used echo Doppler to measure bilateral brachial artery dilator response to 5-min ischaemia [i.e. flow-mediated dilation (FMD)], ischaemic handgrip exercise (iEX) and endothelium-independent dilation to a NO donor [i.e. glyceryl trinitrate (GTN)]. Maximal handgrip strength of the inactive forearm significantly decreased after 8 days (t tests P = 0.03 for Day 0 vs. Day 8), confirming physical deconditioning in the inactive forearm. A significant decrease in peak blood flow was found in the intervention arm (sling: 539 ± 236, 528 ± 184, 384 ± 142 ml/min) relative to the control arm (559 ± 181, 591 ± 219, 613 ± 169 ml/min; 2-way ANOVA interaction: P = 0.05). Analysis revealed no significant change in brachial artery baseline diameter, FMD %, iEX or GTN across the 8 days in either arm (P > 0.05). Eight days of forearm physical inactivity induced a significant decrease in post-ischaemic limb blood flow, suggestive of remodelling of forearm resistance vessels. However, measures of conduit artery endothelium-dependent vasodilation were not altered across an 8-day period of inactivity, suggesting that initial remodelling occurs at distal ends of the vascular tree.

Oral sarpogrelate can improve endothelial dysfunction as effectively as oral cilostazol, with fewer headaches, in active young male smokers

Sarpogrelate and cilostazol are two commonly used adjunctive antiplatelet agents that also can be used to improve endothelial dysfunction. We compared the effects of sarpogrelate and cilostazol on endothelial dysfunction in active male smokers with flow-mediated dilatation (FMD). We enrolled and compared baseline and follow-up FMD in 20 young male smokers without any known cardiovascular diseases. Two participants who were initially medicated with cilostazol dropped out because of severe headache after taking medication. However, they continued the other experiment with sarpogrelate medication. Baseline endothelium-dependent dilatation (EDD) after reactive hyperemia was 7.5 % ± 1.9 % and endothelium-independent dilatation (EID) after sublingual administration of nitroglycerin was 13.3 % ± 3.4 %. After a 2-week treatment of cilostazol, follow-up EDD significantly increased (7.7 % ± 1.9 to 8.8 ± 2.0 %, P = 0.016), but follow-up EID changed insignificantly (13.2 % ± 3.5 to 12.5 % ± 3.9 %, P = 0.350). With the sarpogrelate treatment, follow-up EDD was significantly increased (7.4 % ± 1.9 % to 8.8 % ± 1.9 %, P = 0.021), but follow-up EID was similar (13.5 % ± 3.5 to 14.0 % ± 3.2 %, P = 0.427). There was no clinical significance between the two groups on follow-up EDD and EID (P = 0.984 and 0.212, respectively). However, the mean score of intensity of headache was significantly higher in the cilostazol group than in the sarpogrelate group (3.8 % ± 2.5 % vs 1.4 % ± 2.2 %, P = 0.005). EDD showed a similar significant increase with 2-week treatment of cilostazol and sarpogrelate. However, intensity of headaches was significantly higher in the cilostazol group.

Abstract 33: Participation of Prostaglandin E2 and EP4 Receptors in Connecting Tubule Glomerular Feedback (CTGF).

The afferent arteriole (Af-Art) accounts for most of renal vasculature resistance, thus controlling glomerular filtration rate. The connecting tubule (CNT) is in close contact with the Af-Art. Connecting tubule glomerular feedback (CTGF) is a mechanism in which Na reabsorption in the CNT causes Af-Art dilation. We have shown that CTGF is mediated by eicosanoids, including prostaglandins and epoxyeicosatrienoic acids (EETs), however their exact source and nature remain unknown. Here we tested the hypothesis that during CTGF the CNT releases prostaglandin E 2 (PGE 2 ), which binds EP4 receptors and dilates the Af-Art. Rabbit Af-Arts with the adherent CNT intact were microdissected and perfused. The Af-Arts were preconstricted with norepinephrine. CTGF was elicited by increasing luminal NaCl in the CNT from 10 to 80 mM. To identify the source of the vasodilator prostaglandins we first disrupted the vascular endothelium by adding anti-Factor-VIII antibody to the Af-Art lumen. This did not affect CTGF (control: 7.9±0.9, endothelium disrupted: 8.6±0.6 μm, n=7). We then added arachidonic acid (AA) to the lumen of the CNT while maintaining zero NaCl in the perfusate, and found that AA caused dose-dependent dilation of the attached Af-Art (from 7.9±2.2 to 15.5±1.3 μm, P &lt;0.01, n=4). This cannot be explained by AA diffusing to the Af-Art because AA is a vasoconstrictor for the Af-Art. Taken together, these data indicate that CTGF-induced vasorelaxation is endothelium-independent, and that prostaglandins originate from the CNT. To study which specific prostaglandin and receptor mediate CTGF, we added the EP4 receptor blocker L161982 (10 μM) to the bath in the presence of the EET synthesis inhibitor MS-PPOH. EP4 receptor blockade abolished CTGF (control: 8.5±0.9, MS-PPOH+L161982: 0.8±0.4μm, P &lt;0.001, n=6). To confirm these results we used a different, specific EP4 blocker, ONO-AE-208 (100 nM), which also abolished CTGF (control: 9.4±0.5, MS-PPOH+ONO-AE-208: -0.6±0.2 μm, P &lt;0.001, n=6). We conclude that increasing luminal Na stimulates release of prostaglandin E 2 from the CNT, which acts on EP4 on the Af-Art inducing endothelium-independent dilation during CTGF. Our studies provide a better understanding of the mechanisms by which CTGF controls Af-Art resistance.