The interaction between coronary endothelial dysfunction, local oxidative stress, and endogenous nitric oxide in humans

The association between circulating microRNA levels and coronary endothelial function

Human microRNAs (miRs) have been implicated in human diseases presumably through the downregulation and silencing of targeted genes via post-translational modifications. However, their role in the early stage of coronary atherosclerosis is not known. The aim of this study was to test the hypothesis that patients with early atherosclerosis and coronary endothelial dysfunction (CED) have alterations in transcoronary miR gradients. Patients underwent coronary angiography and endothelial function testing in the cardiac catheterization laboratory. Patients were divided into abnormal (n = 26) and normal (n = 22) microvascular coronary endothelial function based on intracoronary response to infused acetylcholine measured as a percent change in coronary blood flow (CBF) and arterial diameter. Blood samples were obtained simultaneously from the aorta and coronary sinus at the time of catheterization for RNA isolation, and miR subsequently assessed. Baseline characteristics were similar in both groups. Patients with microvascular CED displayed transcoronary gradients significantly elevated in miR-92a and miR-133 normalized to C-elegans-39 miR. Percent change in CBF and the transcoronary gradient of miR-133 displayed a significant inverse correlation (r² = 0.11, p = 0.03). Thus, we present novel data whereupon selected miRs demonstrate elevated transcoronary gradients in patients with microvascular CED. The current findings support further studies on the mechanistic role of miRs in coronary atherosclerosis and in humans.

8-Oxo-7,8-dihydro-2'-deoxyguanosine, reactive oxygen species and ambulatory blood pressure in African and Caucasian men: the SABPA study

Various studies indicate a relationship between increased oxidative stress and hypertension, resulting in increased DNA damage and consequent excretion of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG). The aim of this study was to compare urinary 8-oxodG levels in African and Caucasian men and to investigate the association between ambulatory blood pressure (BP) and pulse pressure (PP) with 8-oxodG in these groups. We included 98 African and 92 Caucasian men in the study and determined their ambulatory BP and PP. Biochemical analyses included, urinary 8-oxodG, reactive oxygen species (ROS) (measured as serum peroxides), ferric reducing antioxidant power (FRAP), total glutathione (GSH), glutathione peroxidase (GPx) and glutathione reductase (GR) activity. The African men had significantly higher systolic (SBP) and diastolic blood pressure (DBP) (both p < 0.001). Assessment of the oxidative stress markers indicated significantly lower 8-oxodG levels (p < 0.001) in the African group. The African men also had significantly higher ROS (p = 0.002) with concomitant lower FRAP (p < 0.001), while their GSH levels (p = 0.013) and GR activity (p < 0.001) were significantly higher. Single and partial regression analyses indicated a negative association between urinary 8-oxodG levels with SBP, DBP and PP only in African men. These associations were confirmed in multiple regression analyses (SBP: R(2) = 0.41; β = -0.25; p = 0.002, DBP: R(2) = 0.30; β = -0.21; p = 0.022, PP: R(2) = 0.30; β = -0.19; p = 0.03). Our results revealed significantly lower urinary 8-oxodG in African men, accompanied by a negative association with BP and PP. We propose that this may indicate a dose-response relationship in which increased oxidative stress may play a central role in the up-regulation of antioxidant defence and DNA repair mechanisms.

Hypertension during vascular endothelial growth factor inhibition: focus on nitric oxide, endothelin-1, and oxidative stress

SIGNIFICANCE

Angiogenesis inhibition with humanized antibodies targeting vascular endothelial growth factor (VEGF) or orally active small tyrosine kinase inhibitors targeting VEGF receptors has become an established treatment modality for various forms of cancer. A common side effect of angiogenesis inhibition is the development of sometimes severe hypertension, which simultaneously appears to be predictive for a favorable antitumor response.

RECENT ADVANCES

Since VEGF increases the expression and activity of endothelial nitric oxide synthase, it has been assumed that the mean blood pressure (MAP) rise during angiogenesis inhibition is caused by a decrease in nitric oxide bioavailability. Yet, the results from experimental and clinical studies exploring this possibility are conflicting. Recent studies provided evidence that the MAP rise during angiogenesis inhibition rather is mediated by activation of the endothelin-1 (ET-1) axis, which, among others, induces oxidative stress. Nevertheless, conclusive evidence for the involvement of reactive oxygen species in the MAP rise could not be obtained so far.

CRITICAL ISSUES

The mechanism underlying activation of the ET-1 axis during angiogenesis inhibition is unclear, and this activation was not anticipated in view of studies showing that VEGF stimulates both the expression and production of ET-1 by endothelial cells.

FUTURE DIRECTIONS

In fact, this activation of the ET-1 axis may support the use of ET receptor antagonists for the treatment of angiogenesis inhibition-induced hypertension, especially because ET receptor stimulation in vascular smooth muscle cells results in VEGF production and mitogenesis in a mitogen-activated protein kinase pathway-dependent manner.

Reactive oxygen species, vascular Noxs, and hypertension: focus on translational and clinical research

SIGNIFICANCE

Reactive oxygen species (ROS) are signaling molecules that are important in physiological processes, including host defense, aging, and cellular homeostasis. Increased ROS bioavailability and altered redox signaling (oxidative stress) have been implicated in the onset and/or progression of chronic diseases, including hypertension.

RECENT ADVANCES

Although oxidative stress may not be the only cause of hypertension, it amplifies blood pressure elevation in the presence of other pro-hypertensive factors, such as salt loading, activation of the renin-angiotensin-aldosterone system, and sympathetic hyperactivity, at least in experimental models. A major source for ROS in the cardiovascular-renal system is a family of nicotinamide adenine dinucleotide phosphate oxidases (Noxs), including the prototypic Nox2-based Nox, and Nox family members: Nox1, Nox4, and Nox5.

CRITICAL ISSUES

Although extensive experimental data support a role for increased ROS levels and altered redox signaling in the pathogenesis of hypertension, the role in clinical hypertension is unclear, as a direct causative role of ROS in blood pressure elevation has yet to be demonstrated in humans. Nevertheless, what is becoming increasingly evident is that abnormal ROS regulation and aberrant signaling through redox-sensitive pathways are important in the pathophysiological processes which is associated with vascular injury and target-organ damage in hypertension.

FUTURE DIRECTIONS

There is a paucity of clinical information related to the mechanisms of oxidative stress and blood pressure elevation, and a few assays accurately measure ROS directly in patients. Such further ROS research is needed in humans and in the development of adequately validated analytical methods to accurately assess oxidative stress in the clinic.

Peripheral microvascular dysfunction predicts residual risk in coronary artery disease patients on statin therapy

OBJECTIVE

Although lowering of low-density lipoprotein cholesterol (LDL-C) by statins is essential in treatment of coronary artery disease (CAD) patients, there is considerable residual risk of secondary coronary artery events (CAE). We examined whether microvascular dysfunction (MiD), measured by peripheral artery tonometry (PAT), can predict prognosis of CAD patients previously treated with statins.

METHODS

We measured log-transformed reactive hyperemia index (L_RHI) in 213 CAD patients who had already achieved LDL-C <100 by statin therapy. Patients were followed-up for secondary CAE for a median of 2.7 years. Patients were divided into two groups: L_RHI ≥ 0.54 (n = 99) and L_RHI < 0.54 (n = 114).

RESULTS

During follow-up, CAE occurred in 4 (4.0%) patients in the L_RHI ≥ 0.54 group and 18 (15.8%) patients in the L_RHI < 0.54 group (P = 0.006). Cox regression analysis indicated that L_RHI was an independent predictor for CAE even after adjustment by Framingham traditional risk factors (FRF; age, T-C/HDL-C ratio, systolic blood pressure, diabetes, current smoker, and gender) and estimated glomerular filtration rate (eGFR) for secondary CAE (HR 0.79, 95% CI: 0.66-0.95). ROC analysis for CAE prediction showed that the AUC for models including FRF only, FRF + eGFR, and FRF + eGFR + L_RHI were 0.60, 0.71, and 0.77, respectively. Moreover, adding eGFR to FRF only (0.63, P = 0.003) and adding L_RHI to the FRF + eGFR model were associated with significant improvement of net reclassification improvement (0.79, P = 0.007).

CONCLUSION

MiD measured by non-invasive PAT adds incremental predictive ability to traditional risk factors for prognosis of CAD patients successfully treated with statins.

Angiotensin II type 1 receptor blockade restores angiotensin-(1–7)-induced coronary vasodilation in hypertrophic rat hearts

The aim of the present study was to investigate the coronary effects of Ang-(1–7) [angiotensin-(1–7)] in hypertrophic rat hearts. Heart hypertrophy was induced by abdominal aorta CoA (coarctation). Ang-(1–7) and AVE 0991, a non-peptide Mas-receptor agonist, at picomolar concentration, induced a significant vasodilation in hearts from sham-operated rats. These effects were blocked by the Mas receptor antagonist A-779. Pre-treatment with L-NAME (NG-nitro-L-arginine methyl ester) or ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinozalin-1-one) [NOS (NO synthase) and soluble guanylate cyclase inhibitors respectively] also abolished the effect of Ang-(1–7) in control hearts. The coronary vasodilation produced by Ang-(1–7) and AVE 0991 was completely blunted in hypertrophic hearts. Chronic oral administration of losartan in CoA rats restored the coronary vasodilation effect of Ang-(1–7). This effect was blocked by A-779 and AT2 receptor (angiotensin II type 2 receptor) antagonist PD123319. Acute pre-incubation with losartan also restored the Ang-(1–7)-induced, but not BK (bradykinin)-induced, coronary vasodilation in hypertrophic hearts. This effect was inhibited by A-779, PD123319 and L-NAME. Chronic treatment with losartan did not change the protein expression of Mas and AT2 receptor and ACE (angiotensin-converting enzyme) and ACE2 in coronary arteries from CoA rats, but induced a slight increase in AT2 receptor in aorta of these animals. Ang-(1–7)-induced relaxation in aortas from sham-operated rats was absent in aortas from CoA rats. In vitro pre-treatment with losartan restored the Ang-(1–7)-induced relaxation in aortic rings of CoA rats, which was blocked by the Mas antagonist A-779 and L-NAME. These data demonstrate that Mas is strongly involved in coronary vasodilation and that AT1 receptor (angiotensin II type 1 receptor) blockade potentiates the vasodilatory effects of Ang-(1–7) in the coronary beds of pressure-overloaded rat hearts through NO-related AT2- and Mas-receptor-dependent mechanisms. These data suggest the association of Ang-(1–7) and AT1 receptor antagonists as a potential therapeutic avenue for coronary artery diseases.

Chronic oxidative-nitrosative stress impairs coronary vasodilation in metabolic syndrome model rats

Metabolic syndrome (MetS) is a combination of clinical disorders that together increase the risk for cardiovascular disease and diabetes. SHRSP.Z-Lepr(fa)/IzmDmcr (SHRSP.ZF) rats with MetS show impaired nitric oxide-mediated relaxation in coronary and mesenteric arteries, and angiotensin II receptor type 1 blockers protect against dysfunction and oxidative-nitrosative stress independently of metabolic effects. We hypothesize that superoxide contributes to functional deterioration in SHRSP.ZF rats. To test our hypothesis, we studied effects of treatment with tempol, a membrane-permeable radical scavenger, on impaired vasodilation in SHRSP.ZF rats. Tempol did not alter body weight, high blood pressure, or metabolic abnormalities, but prevented impairment of acetylcholine-induced and nitroprusside-induced vasodilation in the coronary and mesenteric arteries. Furthermore, tempol reduced the levels of serum thiobarbituric acid reactive substance (TBARS) and 3-nitrotyrosine content in mesenteric arteries. Systemic administration of tempol elevated the expression of soluble guanylate cyclase (sGC) above basal levels in mesenteric arteries of SHRSP.ZF rats. However, acute treatment with tempol or ebselen, a peroxynitrite scavenger, did not ameliorate impaired relaxation of isolated mesenteric arteries. No nitration of tyrosine residues in sGC was observed; however, sGC mRNA expression levels in the arteries of SHRSP.ZF rats were lower than those in the arteries of Wistar-Kyoto rats. Levels of Thr(496)- and Ser(1177)-phosphorylated endothelial nitric oxide synthase (eNOS) were lower in arteries of SHRSP.ZF rats, and acetylcholine decreased Thr(496)-phosphorylated eNOS levels. These results indicated that prolonged superoxide production, leading to oxidative-nitrosative stress, was associated with impaired vasodilation in SHRSP.ZF rats with MetS. Down-regulated sGC expression may be linked to dysfunction, while reduced NO bioavailability/eNOS activity and modified sGC activity due to superoxide production were excluded as pivotal mechanisms.

Circulating humanin levels are associated with preserved coronary endothelial function

Humanin is a small endogenous antiapoptotic peptide, originally identified as protective against Alzheimer's disease, but subsequently also found on human endothelium as well as carotid artery plaques. Endothelial dysfunction is a precursor to the development of atherosclerotic plaques, which are characterized by a highly proinflammatory, reactive oxygen species, and apoptotic milieu. Previous animal studies demonstrated that humanin administration may improve endothelial function. Thus the aim of this study was to test the hypothesis that patients with coronary endothelial dysfunction have reduced systemic levels of humanin. Forty patients undergoing coronary angiography and endothelial function testing were included and subsequently divided into two groups based on coronary blood flow (CBF) response to intracoronary acetylcholine (normal ≥ 50% increase from baseline, n = 20 each). Aortic plasma samples were obtained at the time of catheterization for the analysis of humanin levels and traditional biomarkers of atherosclerosis including C-reactive protein, Lp-Pla(2), and homocysteine. Baseline characteristics were similar in both groups. Patients with coronary endothelial dysfunction (change in CBF = -33 ± 25%) had significantly lower humanin levels (1.3 ± 1.1 vs. 2.2 ± 1.5 ng/ml, P = 0.03) compared with those with normal coronary endothelial function (change in CBF = 194 ± 157%). There was a significant and positive correlation between improved CBF and humanin levels (P = 0.0091) not seen with changes in coronary flow reserve (P = 0.76). C-reactive protein, Lp-Pla(2), and homocysteine were not associated with humanin levels. Thus we observed that preserved human coronary endothelial function is uniquely associated with higher systemic humanin levels, introducing a potential diagnostic and/or therapeutic target for patients with coronary endothelial function.

Glucagon-like peptide-1 preserves coronary microvascular endothelial function after cardiac arrest and resuscitation: potential antioxidant effects

Glucagon-like peptide-1 (GLP-1) has protective effects in the heart. We hypothesized that GLP-1 would mitigate coronary microvascular and left ventricular (LV) dysfunction if administered after cardiac arrest and resuscitation (CAR). Eighteen swine were subjected to ventricular fibrillation followed by resuscitation. Swine surviving to return of spontaneous circulation (ROSC) were randomized to receive an intravenous infusion of either human rGLP-1 (10 pmol·kg(-1)·min(-1); n = 8) or 0.9% saline (n = 8) for 4 h, beginning 1 min after ROSC. CAR caused a decline in coronary flow reserve (CFR) in control animals (pre-arrest, 1.86 ± 0.20; 1 h post-ROSC, 1.3 ± 0.05; 4 h post-ROSC, 1.25 ± 0.06; P < 0.05). GLP-1 preserved CFR for up to 4 h after ROSC (pre-arrest, 1.31 ± 0.17; 1 h post-ROSC, 1.5 ± 0.01; 4 h post-ROSC, 1.55 ± 0.22). Although there was a trend toward improvement in LV relaxation in the GLP-1-treated animals, overall LV function was not consistently different between groups. 8-iso-PGF(2α), a measure of reactive oxygen species load, was decreased in post-ROSC GLP-1-treated animals [placebo, control (NS): 38.1 ± 1.54 pg/ml; GLP-1: 26.59 ± 1.56 pg/ml; P < 0.05]. Infusion of GLP-1 after CAR preserved coronary microvascular and LV diastolic function. These effects may be mediated through a reduction in oxidative stress.

Nitric oxide-mediated coronary flow regulation in patients with coronary artery disease: recent advances

Nitric oxide (NO) formed via endothelial NO synthase (eNOS) plays crucial roles in the regulation of coronary blood flow through vasodilatation and decreased vascular resistance, and in inhibition of platelet aggregation and adhesion, leading to the prevention of coronary circulatory failure, thrombosis, and atherosclerosis. Endothelial function is impaired by several pathogenic factors including smoking, chronic alcohol intake, hypercholesterolemia, obesity, hyperglycemia, and hypertension. The mechanisms underlying endothelial dysfunction include reduced NO synthase (NOS) expression and activity, decreased NO bioavailability, and increased production of oxygen radicals and endogenous NOS inhibitors. Atrial fibrillation appears to be a risk factor for endothelial dysfunction. Endothelial dysfunction is an important predictor of coronary artery disease (CAD) in humans. Penile erectile dysfunction, associated with impaired bioavailability of NO produced by eNOS and neuronal NOS, is also considered to be highly predictive of ischemic heart disease. There is evidence suggesting an important role of nitrergic innervation in coronary blood flow regulation. Prophylactic and therapeutic measures to eliminate pathogenic factors inducing endothelial and nitrergic nerve dysfunction would be quite important in preventing the genesis and development of CAD.

Isoprostanes and isofurans as non-traditional risk factors for cardiovascular disease among Canadian Inuit

OBJECTIVES

The aim of the present study was to investigate the potential importance of oxidative stress, measured by isoprostanes-related compounds, as non-traditional risk factor for cardiovascular disease. We planned to examine the relationship between concentrations of plasma F₂-isoprostanes (F₂-IsoPs), isofurans (IsoFs), measures of obesity and various cardiometabolic risk factors.

MATERIALS AND METHODS

Cross-sectional study using a sub-sample from the population of a survey conducted in the summer and fall 2007 and 2008 by Canadian Coastguard Ship Amundsen in 36 Canadian Arctic Inuit communities. Subjects included a subset (n = 233) of a total study population (n = 2595) with a mean age 42.56 ± 15.39 years and body mass index 27.78 ± 5.65 kg/m². Plasma levels of F₂-IsoPs and IsoFs was determined by gas chromatography/negative ion chemical ionization/mass spectrometry (GC/NICI/MS) method; and their relationships to waist circumference (WC), blood pressure C reactive proteins (CRP), blood lipids and fasting glucose were assessed by multivariate analyses.

RESULTS

Plasma F₂-IsoPs correlated positively with CRP (r =.132, P =.048) and systolic blood pressure (SBP) (r =.157, P =.024) after adjustment for age, sex and body mass index. IsoFs correlated with WC (r =.190, P =.005) and SBP (r =.137, P =.048). F2-IsoPs were not found elevated in smokers (P =.034), whereas IsoFs were decreased in smokers (P =.001). WC, SBP and sex were found to be major correlates of oxidative stress in Canadian Inuit.

CONCLUSIONS

Plasma measures of F₂-IsoPs and IsoFs increase with increased obesity and associated cardiometabolic risk factors, including CRP and blood pressure. Simultaneous measurement of IsoFs provides an advantageous mechanistic insight into oxidative stress not captured by F₂-IsoPs alone.

Role of simvastatin and/or antioxidant vitamins in therapeutic angiogenesis in experimental diabetic hindlimb ischemia: effects on capillary density, angiogenesis markers, and oxidative stress

Therapeutic angiogenesis has emerged as an attractive approach for the management of peripheral arterial disease in diabetic patients. Oxidative stress generated and aggravated by prolonged hyperglycemia may interfere with and destroy the newly formed blood vessels. Angiogenic effect of simvastatin has been reported; however, its exact mechanism is yet to be evaluated. In addition, the exact role of antioxidant vitamins in diabetic peripheral arterial disease is still controversial. The present study was undertaken to investigate the therapeutic potential of simvastatin and antioxidant vitamins (E and C) and their combined effects on angiogenesis in diabetic hind-limb ischemia. Streptozotocin diabetic rats were treated for 6 weeks with simvastatin either alone or in combination with vitamin E or vitamin C. Parameters of angiogenesis, nitric oxide, heme oxygenase-1 (HO-1), and oxidative stress markers were evaluated. CD31 immunostaining revealed an increased capillary density in ischemic gastrocnemious tissue of diabetic rats treated with either simvastatin or its combination with vitamin C. This effect was accompanied by up-regulated plasma levels of HO-1, nitric oxide, vascular endothelial growth factor (VEGF) and its intra-muscular receptor type-2 (Flk-1). Tissue reduced glutathione and antioxidant enzymes activities were normalized in groups treated with antioxidant vitamins or their combination with simvastatin with concomitant blunting of lipid peroxidation. Vitamins E and C, through their antioxidant effects, evidently enhanced the angiogenic effect of simvastatin in ischemic diabetic muscle. Hence, the use of antioxidant vitamins combined with statins to induce therapeutic angiogenesis is a promising strategy in the management of diabetes-associated peripheral arterial disease.

Oxidative stress, Noxs, and hypertension: experimental evidence and clinical controversies

Reactive oxygen species (ROS) are signaling molecules that influence many physiological processes. Increased ROS bioavailability and altered redox signaling (oxidative stress) have been implicated in chronic diseases including hypertension. Although oxidative stress may not be the sole cause of hypertension, it amplifies blood pressure elevation in the presence of other prohypertensive factors (salt, renin-angiotensin system, sympathetic hyperactivity). A major source for cardiovascular ROS is a family of non-phagocytic NADPH oxidases (Nox1, Nox2, Nox4, Nox5). Other sources of ROS involve mitochondrial electron transport enzymes, xanthine oxidase, and uncoupled nitric oxide synthase. Although evidence from experimental and animal studies supports a role for oxidative stress in the pathogenesis of hypertension, there is still no convincing proof that oxidative stress is a cause of human hypertension. However, what is clear is that oxidative stress is important in the molecular mechanisms associated with cardiovascular and renal injury in hypertension and that hypertension itself can contribute to oxidative stress. The present review addresses the putative function of ROS in the pathogenesis of hypertension and focuses on the role of Noxs in ROS generation in vessels and the kidney. Implications of oxidative stress in human hypertension are discussed, and clinical uncertainties are highlighted.

Regulation of adipose tissue energy availability through blood flow control in the metabolic syndrome

Maintenance of blood flow rate is a critical factor for tissue oxygen and substrate supply. The potentially large mass of adipose tissue deeply influences the body distribution of blood flow. This is due to increased peripheral resistance in obesity and the role of this tissue as the ultimate destination of unused excess of dietary energy. However, adipose tissue cannot grow indefinitely, and the tissue must defend itself against the avalanche of nutrients provoking inordinate growth and inflammation. In the obese, large adipose tissue masses show lower blood flow, limiting the access of excess circulating substrates. Blood flow restriction is achieved by vasoconstriction, despite increased production of nitric oxide, the vasodilatation effects of which are overridden by catecholamines (and probably also by angiotensin II and endothelin). Decreased blood flow reduces the availability of oxygen, provoking massive glycolysis (hyperglycemic conditions), which results in the production of lactate, exported to the liver for processing. However, this produces local acidosis, which elicits the rapid dissociation of oxyhemoglobin, freeing bursts of oxygen in localized zones of the tissue. The excess of oxygen (and of nitric oxide) induces the production of reactive oxygen species, which deeply affect the endothelial, blood, and adipose cells, inducing oxidative and nitrosative damage and eliciting an increased immune response, which translates into inflammation. The result of the defense mechanism for adipose tissue, localized vasoconstriction, may thus help develop a more generalized pathologic response within the metabolic syndrome parameters, extending its effects to the whole body.

Vitamin C prevents hyperoxia-mediated coronary vasoconstriction and impairment of myocardial function in healthy subjects

Supplementary oxygen is commonly administered in current medical practice. Recently it has been suggested that hyperoxia causes acute oxidative stress and produces prompt and substantial changes in coronary resistance in patients with ischemic heart disease. In this report, we examined whether the effects of hyperoxia on coronary blood velocity (CBV) would be associated with a reduction in myocardial function. We were also interested in determining if the postulated changes in left ventricular (LV) function seen with tissue Doppler imaging (TDI) could be reversed with intravenous vitamin C, a potent, acute anti-oxidant. LV function was determined in eight healthy subjects with transthoracic echocardiography and TDI before and after hyperoxia and with and without infusing vitamin C. Hyperoxia compared with room air promptly reduced CBV by 28 ± 3% (from 23.50 ± 2.31 cm/s down to 17.00 ± 1.79 cm/s) and increased relative coronary resistance by 34 ± 5% (from 5.63 ± 0.88 up to 7.32 ± 0.94). Meanwhile, LV myocardial systolic velocity decreased by 11 ± 6% (TDI). These effects on flow and function were eliminated by the infusion of vitamin C, suggesting that these changes are mediated by vitamin C-quenchable substances acting on the coronary microcirculation.

Is the Western diet adequate in copper?

Copper has been known to be essential for health for more than three quarters of a century. Myriad experiments with animals reveal that the cardiovascular, musculoskeletal and nervous systems are most sensitive to deficiency. Copper in the Western diet has been decreasing at least since the 1930s; half of the adult population consumes less than the amount recommended in the European Communities and the United Kingdom. At least one fourth of adults consume less than the estimated average requirement published for the United States and Canada. Hundreds of people have been reported in journals about medicine and neurology rather than nutrition to have impaired copper nutriture based on the criteria of low copper concentrations and low activities of enzymes dependent on copper in various fluids and tissues. In contrast, only 46 people have participated in depletion/repletion experiments needed to define requirements. Almost 1000 people have benefited from supplements containing copper in controlled trials. People deficient in copper are being identified increasingly; it is unknown if unusually high requirements or unusually low diets are causal. Alzheimer's disease, ischemic heart disease and osteoporosis are the most likely human illnesses from low copper intakes.

Role of oxidative stress in disease progression in Stage B, a pre-cursor of heart failure

Oxidative stress represents a persistent imbalance between the production and the compensation of reactive oxygen species. Though predominantly found in advanced heart failure, the most frequent "at-risk" condition has been associated with underlying oxidative stress. It is therefore conceivable that timely detection and early intervention to reduce oxidative stress processes provide an opportunity to prevent disease progression to overt heart failure. This article reviews the current understanding of the current evidence of oxidative stress involvement in the pathophysiology of human heart failure and its potential therapeutic interventions in patients with Stage A and B heart failure.

Purified anthocyanin supplementation improves endothelial function via NO-cGMP activation in hypercholesterolemic individuals

BACKGROUND

Anthocyanins have been shown to improve endothelial function in animal models. However, whether these compounds have similar beneficial effects in humans is largely unknown.

METHODS

In a short-term crossover study, 12 hypercholesterolemic individuals were given oral anthocyanins (320 mg) isolated from berries or placebo. Brachial artery flow-mediated dilation (FMD) was assessed before and after the intervention. In a long-term intervention trial (12 weeks), 150 hypercholesterolemic individuals were given anthocyanins (320 mg/day, n = 75) or placebo (n = 75), after which we measured FMD, plasma cGMP, and other serum biomarkers. Another short-term intervention was conducted in the presence of NO-cGMP inhibitors in 6 people and in a rat aortic ring model (n = 8).

RESULTS

Significant increases of FMD from 8.3% (0.6%) at baseline to 11.0% (0.8%) at 1 h and 10.1% (0.9%) at 2 h were observed after short-term anthocyanin consumption, concomitantly with increases of plasma anthocyanin concentrations (P < 0.05). In the study participants who received long-term anthocyanin intervention, compared with the control group, we observed significant increases in the FMD (28.4% vs 2.2%), cGMP (12.6% vs -1.2%), and HDL-cholesterol concentrations, but decreases in the serum soluble vascular adhesion molecule-1 and LDL cholesterol concentrations (P < 0.05). The changes in the cGMP and HDL cholesterol concentrations positively correlated with FMD in the anthocyanin group (P < 0.05). In the presence of NO-cGMP inhibitors, the effects of anthocyanin on endothelial function were abolished in human participants and in a rat aortic ring model.

CONCLUSIONS

Anthocyanin supplementation improves endothelium-dependent vasodilation in hypercholesterolemic individuals. This effect involves activation of the NO-cGMP signaling pathway, improvements in the serum lipid profile, and decreased inflammation.

Dipyridamole reverses peripheral ischemia and induces angiogenesis in the Db/Db diabetic mouse hind-limb model by decreasing oxidative stress

Dipyridamole anti-platelet therapy has previously been suggested to ameliorate chronic tissue ischemia in healthy animals. However, it is not known if dipyridamole therapy represents a viable approach to alleviating chronic peripheral tissue ischemia associated with type 2 diabetes. Here we examine the hypothesis that dipyridamole treatment restores reperfusion of chronic hind-limb ischemia in the murine B6.BKS-Lepr(db/db) diabetic model. Dipyridamole therapy quickly rectified ischemic hind-limb blood flow to near preligation levels within 3 days of the start of therapy. Restoration of ischemic tissue blood flow was associated with increased vascular density and endothelial cell proliferation observed only in ischemic limbs. Dipyridamole significantly increased total nitric oxide metabolite levels in tissue, which were not associated with changes in endothelial NO synthase expression or phosphorylation. Interestingly, dipyridamole therapy significantly decreased ischemic tissue superoxide and protein carbonyl levels, identifying a dominant antioxidant mechanistic response. Dipyridamole therapy also moderately reduced diabetic hyperglycemia and attenuated development of dyslipidemia over time. Together, these data reveal that dipyridamole therapy is an effective modality for the treatment of chronic tissue ischemia during diabetes and highlights the importance of dipyridamole antioxidant activity in restoring tissue NO bioavailability during diabetes.

ACE2-angiotensin-(1-7)-Mas axis and oxidative stress in cardiovascular disease

The renin-angiotensin-aldosterone system (RAAS) is a pivotal regulator of physiological homeostasis and diseases of the cardiovascular system. Recently, new factors have been discovered, such as angiotensin-converting enzyme 2 (ACE2), angiotensin-(1-7) and Mas. This newly defined ACE2-angiotensin-(1-7)-Mas axis was shown to have a critical role in the vasculature and in the heart, exerting mainly protective effects. One important mechanism of the classic and the new RAAS regulate vascular function is through the regulation of redox signaling. Angiotensin II is a classic prooxidant peptide that increases superoxide production through the activation of NAD(P)H oxidases. This review summarizes the current knowledge about the ACE2-angiotensin-(1-7)-Mas axis and redox signaling in the context of cardiovascular regulation and disease. By interacting with its receptor Mas, angiotensin-(1-7) induces the release of nitric oxide from endothelial cells and thereby counteracts the effects of angiotensin II. ACE2 converts angiotensin II to angiotensin-(1-7) and, thus, is a pivotal regulator of the local effects of the RAAS on the vessel wall. Taken together, the ACE2-angiotensin-(1-7)-Mas axis emerges as a novel therapeutic target in the context of cardiovascular and metabolic diseases.

Reactive oxygen species and vascular biology: implications in human hypertension

Increased vascular production of reactive oxygen species (ROS; termed oxidative stress) has been implicated in various chronic diseases, including hypertension. Oxidative stress is both a cause and a consequence of hypertension. Although oxidative injury may not be the sole etiology, it amplifies blood pressure elevation in the presence of other pro-hypertensive factors. Oxidative stress is a multisystem phenomenon in hypertension and involves the heart, kidneys, nervous system, vessels and possibly the immune system. Compelling experimental and clinical evidence indicates the importance of the vasculature in the pathophysiology of hypertension and as such much emphasis has been placed on the (patho)biology of ROS in the vascular system. A major source for cardiovascular, renal and neural ROS is a family of non-phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox), including the prototypic Nox2 homolog-based NADPH oxidase, as well as other Noxes, such as Nox1 and Nox4. Nox-derived ROS is important in regulating endothelial function and vascular tone. Oxidative stress is implicated in endothelial dysfunction, inflammation, hypertrophy, apoptosis, migration, fibrosis, angiogenesis and rarefaction, important processes involved in vascular remodeling in hypertension. Despite a plethora of data implicating oxidative stress as a causative factor in experimental hypertension, findings in human hypertension are less conclusive. This review highlights the importance of ROS in vascular biology and focuses on the potential role of oxidative stress in human hypertension.

Coronary endothelial dysfunction in humans is associated with coronary retention of osteogenic endothelial progenitor cells

AIMS

Endothelial progenitor cells (EPC) may participate in the repair of injured coronary endothelium. We have recently identified EPC co-expressing the osteoblastic marker osteocalcin [OCN (+) EPC] and found that their numbers are increased in patients with early and late coronary atherosclerosis. The current study was designed to test the hypothesis that early coronary atherosclerosis is associated with the retention of osteogenic EPC within the coronary circulation.

METHODS AND RESULTS

Blood samples were taken simultaneously from the proximal aorta and the coronary sinus from 31 patients undergoing invasive coronary endothelial function testing. Using flow cytometry, peripheral blood mononuclear cells were analysed for EPC markers (CD133, CD34, KDR) and OCN. The net gradient of EPC was calculated by multiplying the coronary blood flow by the arteriovenous EPC gradient (a negative net gradient indicating retention of EPC). Similarly, serum samples were analysed for stromal cell-derived factor-1 alpha (SDF-1 alpha) and interleukin-8 (IL-8) and their net production calculated. Compared with controls (n = 17) patients with endothelial dysfunction (ED, n = 14) had a significant net retention of CD34+/CD133-/KDR+/OCN+ EPC [118.38 (0.00, 267.04) vs. -112.03 (838.36, 0.00), P = 0.004]. The retention of OCN (+) EPC correlated with the degree of ED. Patients with ED also showed a net retention of CD34+/CD133-/KDR+ EPC (P = 0.010). Net production of IL-8 was positive in ED [1540.80 (-300.40, 21744.10)pg/mL] but negative in controls [-3428.50 (-11225.00, 647.48), P = 0.025].

CONCLUSION

Our study demonstrates that patients with early coronary atherosclerosis are characterized by retention of OCN (+) EPC within the coronary circulation, potentially leading to progressive coronary calcification rather than normal repair.

Endothelial function as a functional expression of cardiovascular risk factors

Traditional cardiovascular risk (CV) factors based on the Framingham study have been used to estimate the risk of CV events and determine target cholesterol levels for primary prevention. Recently published systematic reviews have, however, demonstrated that the Framingham risk score is limited in certain cohorts and requires adjustment. Indeed, traditional CV risk factors fail to predict the development of coronary heart disease in 25-50% of cases. This underscores the complex interplay between traditional CV risk factors, genetic predisposition and other atheroprotective factors present in individuals of different populations in predicting CV events. Endothelial dysfunction, a functional expression of the inherent atherosclerotic risk representing an integrated index of both the overall CV risk-factor burden and the sum of all vasculoprotective factors in an individual, may serve as the missing link between CV risk factors and atherosclerotic disease. Endothelial function measurements may aid in future prediction of CV events and help identify high-risk patients for targeted therapy as well as provide a primary therapeutic end point for clinical follow-up of these patients. Recently introduced reactive hyperemia peripheral arterial tonometry is emerging as a promising tool in endothelial function measurement and CV risk stratification.

Long-term administration of endothelin receptor antagonist improves coronary endothelial function in patients with early atherosclerosis

BACKGROUND

Endothelin (ET-1) is one of the most potent vasoconstrictors and plays a seminal role in the pathogenesis of atherosclerosis. The present study was designed to test the hypothesis that long-term treatment with an endothelin-A (ET(A)) receptor antagonist improves coronary endothelial function in patients with early coronary atherosclerosis.

METHODS AND RESULTS

Forty-seven patients with multiple cardiovascular risk factors, nonobstructive coronary artery disease, and coronary endothelial dysfunction were randomized in a double-blind manner to either the ET(A) receptor antagonist atrasentan (10 mg) or placebo for 6 months. Coronary endothelium-dependent vasodilation was examined by infusing acetylcholine (10(-6) to 10(-4) mol/L) in the left anterior descending coronary artery. N(G)-monomethyl-l-arginine was administered to a subgroup of patients. Endothelium-independent coronary flow reserve was examined by use of intracoronary adenosine and nitroglycerin. Baseline characteristics and incidence of adverse effects were similar between the 2 groups. There was a significant improvement in percent change of coronary blood flow in response to acetylcholine at 6 months from baseline in the atrasentan group compared with the placebo group (39.67%, 95% confidence interval 23.23% to 68.21%, versus -2.22%, 95% confidence interval -27.37% to 15.28%; P<0.001). No significant difference in the percent change of coronary artery diameter or change in coronary flow reserve was demonstrated. Coronary blood flow, coronary artery diameter, and the effect of N(G)-monomethyl-l-arginine were similar between the groups at baseline and at 6 months.

CONCLUSIONS

This study demonstrates that 6-month treatment with atrasentan improves coronary microvascular endothelial function and supports the role of the endogenous endothelin system in the regulation of endothelial function in early atherosclerosis in humans. Clinical Trial Registration Information- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00271492.

Increased blood flow induces oxidative stress through an endothelium- and nitric oxide-independent mechanism

Bradykinin, a potent vasodilator, stimulates the formation of reactive oxygen species and F(2)-isoprostanes in vitro. The effect of bradykinin on oxidative stress in humans is not known. This study tested the hypothesis that bradykinin induces oxidative stress through a nitric oxide (NO)-dependent mechanism in the human vasculature. We measured forearm blood flow (FBF) and net F(2)-isoprostane release in response to intraarterial bradykinin (50-200 ng/min), nitroprusside (1.6-6.4 microg/min), or diltiazem (3.6-14.4 microg/min) in the absence and presence of the NO synthase inhibitor N(omega)-monomethyl-L-arginine (L-NMMA) in normotensive and hypertensive subjects pretreated with aspirin. L-NMMA significantly decreased basal FBF and basal net F(2)-isoprostane release (from 28.7+/-5.2 to 13.4+/-3.5 pg/min/100ml, P=0.01) in all subjects. Bradykinin caused a significant increase in FBF and net F(2)-isoprostane release in both normotensive and hypertensive subjects. During NO synthase inhibition, bradykinin significantly increased net F(2)-isoprostane release in both groups (P=0.001) and there was no effect of L-NMMA on bradykinin-stimulated F(2)-isoprostane release (P=0.46). Nitroprusside also significantly increased net F(2)-isoprostane release in hypertensive subjects (P=0.01) and this response was not affected by L-NMMA (P=0.50). Diltiazem increased FBF as well as net F(2)-isoprostane release (from 44.5+/-12.5 to 61.2+/-14.7 pg/min/100ml at the highest dose, P=0.05). Increasing blood flow induces oxidative stress through a NO- and endothelium-independent mechanism.

The ALDH2 Glu504Lys polymorphism is associated with coronary artery disease in Han Chinese: Relation with endothelial ADMA levels

OBJECTIVES

We studied the association between mitochondrial aldehyde dehydrogenase (ALDH2) Glu504Lys (rs671 or ALDH2*2) polymorphism and coronary artery disease (CAD), and sought to clarify the mechanisms underlying this association.

METHODS

The ALDH2 rs671 polymorphism was genotyped in 417 CAD patients and 448 age- and gender-matched controls. All participants were Han Chinese. Human umbilical vein endothelial cells (HUVECs) isolated from 11 human umbilical cords were genotyped, cultured, and exposed to angiotensin II (Ang II, 10(-7)-10(-5)mol/L). Dimethylarginine dimethylaminohydrolase 1 (DDAH1) mRNA expression levels were determined by real-time PCR. Levels of asymmetric dimethylarginine (ADMA) in culture media and cell lysates were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS).

RESULTS

The frequency of carriers of the ALDH2 rs671 A allele (GA+AA) was significantly higher in patients with CAD (47.5%) than in controls (35.0%, p=0.0002). After adjustment for potential confounders, the odds ratio (OR) for CAD for carriers of the rs671 A allele was 1.85 (95% confidence interval [CI]: 1.38-2.49, p=0.00005) in the entire study cohort, and 1.95 (95% CI: 1.40-2.70, p=0.00007) in non-drinkers. In non-drinking controls, the homozygous rs671 AA genotype was associated with significantly lower high-density lipoprotein cholesterol (HDL-C) concentrations compared with rs671 GG homozygotes (p=0.015). HUVEC cells homozygous for the G allele of rs671 showed a significantly higher DDAH1 mRNA expression and lower intracellular ADMA levels compared with heterozygous GA cells (p<0.05, respectively). In homozygous GG cells, high concentrations of Ang II (10(-5)mol/L) decreased DDAH1 mRNA expression and increased intracellular ADMA concentrations.

CONCLUSIONS

The rs671 polymorphism of ALDH2 is associated with CAD in Han Chinese, possibly by influencing HDL-C levels and endothelial ADMA levels.

Antioxidative defense and mitochondrial thermogenic response in brown adipose tissue

Cold-exposure activates interscapular brown adipose tissue (IBAT) non-shivering thermogenesis that relies primarily on intensification of metabolic rate and uncoupling. During cold-acclimation, uncoupling in IBAT decreases superoxide (O(2) (·-)) production and as an adaptive response the activities of manganese and copper, zinc superoxide dismutase (Mn- and CuZn-SOD, respectively) are decreased, as well. However, molecular mechanisms governing this SODs adaptive response are still unsolved. Besides, knowing that NO reinforces IBAT uncoupling, we wondered whether nitric oxide (NO) is taking part in SODs regulation? Mn- and CuZn-SOD mRNA and protein expression, uncoupling protein 1 (UCP1), nitrotyrosine and nuclear factor-kappa B (NF-κB) immunolabeling, as well as total SOD (tSOD) activity in IBAT of rats subjected to cold (4 ± 1°C) for 1, 3, 7, 12, 21 and 45 days and treated by l-arginine or N(ω)-nitro-l-arginine-methyl ester (l-NAME) were examined. Cold increased UCP1 immunopositivity and decreased tSOD activity during entire cold-acclimation and transiently, (day 3), activated NF-κB and increased Mn and CuZn-SOD mRNA expression and nitrotyrosine labeling, suggesting NO involvement in this signaling. However, SODs mRNA expression was decreasing from day 12 till the end of cold-acclimation. l-arginine augmented and prolonged cold-induced UCP1 and nitrotyrosine immunopositivity, NF-κB activation and SODs mRNA expression increase, while l-NAME expressed an opposite effect. Related to cold, l-arginine decreased, while l-NAME increased Mn-SOD protein expression. In contrast, neither low temperature nor both treatments applied affected CuZn-SOD protein expression. The results showed that adaptive decrease in SODs activity on uncoupling-decreased O(2) (·-) production was achieved already at the level of gene transcription and that NO takes part in the regulation of IBAT SOD isoforms.

Adiponectin directly improves endothelial dysfunction in obese rats through the AMPK-eNOS Pathway

OBJECTIVE

Hypoadiponectinemia has been proved to be closely related to endothelial dysfunction in peripheral arteries and is thought to be an independent risk factor for cardiovascular disease. The objective of this study was to investigate whether adiponectin might independently improve endothelial dysfunction in aorta isolated from high-fat-diet-induced obese. Sprague-Dawley rat and to study the mechanism involved.

RESEARCH DESIGN AND SUBJECTS

Male Sprague-Dawley rats were fed with a regular or a high-fat diet for 6 weeks. The aorta was isolated, and vascular segments were incubated with vehicle or the globular adiponectin (globular domain (gAD); 2 mg ml(-1)) for 2 h. The effect of gAD on endothelial function and nitric oxide (NO) production was determined. Human aortic endothelial cells in primary culture were treated with vehicle or gAD (4 mg ml(-1)). The effect of gAD on the level of phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser1177, AMPK at Thr176 and Akt at Ser473 in endothelial cells were determined.

RESULTS

Severe endothelial dysfunction was observed in high-fat diet fed rat aortic segments. After gAd incubation, the endothelium-dependent relaxation was partly improved and total production of nitric oxide as result of enhanced eNOS activity was also increased. In the cultured endothelial cell line HUVEC, globular adiponectin increased the activity of eNOS through activating AMPK by stimulating its phosphorylation at Thr176 but not Akt.

CONCLUSION

The demonstration in the current study that adiponectin reverses endothelial dysfunction through increasing NO production by eNOS phosphorylation, and decreasing NO inactivation by blocking superoxide production provides a new direction in the prevention of vascular injury in the obesity population.

Nitric oxide and pathogenic mechanisms involved in the development of vascular diseases

Nitric oxide (NO) is a pivotal signaling messenger in the cardiovascular system. NO participates in regulatory functions including control of hemostasis, fibrinolysis, platelet and leukocyte interactions with the arterial wall, regulation of vascular tone, proliferation of vascular smooth muscle cells, and homeostasis of blood pressure. Diminished NO bioavailability and abnormalities in NO-dependent signaling are among central factors of vascular disease, although it is unclear whether this is a cause of, or result of endothelial dysfunction or both pathogenic events. Disturbances in NO bioavailability have been linked to cause endothelial dysfunction, leading to increased susceptibility to atherosclerotic lesion progression, hypertension, hypercholesterolemia, diabetes mellitus, thrombosis and stroke.

Segmental coronary endothelial dysfunction in patients with minimal atherosclerosis is associated with necrotic core plaques

BACKGROUND/OBJECTIVE

Endothelial dysfunction and atherosclerosis are systemic disorders, but are often characterised by segmental involvement and complications. A potential mechanism for local involvement early in the disease process may be related to plaque composition. This study was designed to test the hypothesis that in patients with minimal coronary atherosclerosis, coronary artery segments with abnormal endothelial function have specific plaque characteristics.

METHODS

Intravascular ultrasound (IVUS) images were obtained from 30 patients who underwent coronary endothelial function assessment. Spectral analysis of the IVUS radiofrequency data was used for assessment of plaque composition. IVUS findings of the coronary sections were compared according to the corresponding endothelial response to acetylcholine.

RESULTS

Sections with a decrease epicardial coronary arterial diameter in response to acetylcholine had smaller baseline lumen (7.5 (2.4) mm(2) vs 8.8 (3.3) mm(2), p = 0.006) but larger plaque burden (37.1% (9.4%) vs 31% (7%), p = 0.003) than sections with normal endothelial response. Sections with endothelial dysfunction had larger necrotic core plaques: 0.13 (0.03-0.33) mm(2) vs 0.0 (0.0-0.07), p<0.001 and more dense calcium: 0.03 (IQR 0.0-0.13) mm(2) vs 0.0 (0.0-0.10) mm(2), p<0.01), than those with normal endothelial response. Only necrotic core area was associated with endothelial dysfunction (p<0.001) after adjusting for other measures.

CONCLUSIONS

This study suggests that local coronary endothelial dysfunction in patients with minimal coronary atherosclerosis is associated with plaque characteristics that are typical of vulnerable plaques.

Endothelial dysfunction in aged humans is related with oxidative stress and vascular inflammation

Vascular endothelial dysfunction occurs during the human aging process, and it is considered as a crucial event in the development of many vasculopathies. We investigated the underlying mechanisms of this process, particularly those related with oxidative stress and inflammation, in the vasculature of subjects aged 18-91 years without cardiovascular disease or risk factors. In isolated mesenteric microvessels from these subjects, an age-dependent impairment of the endothelium-dependent relaxations to bradykinin was observed. Similar results were observed by plethysmography in the forearm blood flow in response to acetylcholine. In microvessels from subjects aged less than 60 years, most of the bradykinin-induced relaxation was due to nitric oxide release while the rest was sensitive to cyclooxygenase (COX) blockade. In microvessels from subjects older than 60 years, this COX-derived vasodilatation was lost but a COX-derived vasoconstriction occurred. Evidence for age-related vascular oxidant and inflammatory environment was observed, which could be related to the development of endothelial dysfunction. Indeed, aged microvessels showed superoxide anions (O(2)(-)) and peroxynitrite (ONOO(-)) formation, enhancement of NADPH oxidase and inducible NO synthase expression. Pharmacological interference of COX, thromboxane A(2)/prostaglandin H(2) receptor, O(2)(-), ONOO(-), inducible NO synthase, and NADPH oxidase improved the age-related endothelial dysfunction. In situ vascular nuclear factor-kappaB activation was enhanced with age, which correlated with endothelial dysfunction. We conclude that the age-dependent endothelial dysfunction in human vessels is due to the combined effect of oxidative stress and vascular wall inflammation.

Endothelial dysfunction and vascular disease

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO). The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDHF-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive G(i) (e.g. responses to serotonin and thrombin) and pertussis toxin-insensitive G(q) (e.g. adenosine diphosphate and bradykinin) coupling proteins. The release of NO by the endothelial cell can be up-regulated (e.g. by oestrogens, exercise and dietary factors) and down-regulated (e.g. oxidative stress, smoking and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively loose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and causing endothelium-dependent hyperpolarizations), endothelial cells also can evoke contraction (constriction) of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factor (EDCF). Most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells. EDCF-mediated responses are exacerbated when the production of NO is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients.

Cyclic GMP signaling in cardiovascular pathophysiology and therapeutics

Cyclic guanosine 3',5'-monophosphate (cGMP) mediates a wide spectrum of physiologic processes in multiple cell types within the cardiovascular system. Dysfunctional signaling at any step of the cascade - cGMP synthesis, effector activation, or catabolism - have been implicated in numerous cardiovascular diseases, ranging from hypertension to atherosclerosis to cardiac hypertrophy and heart failure. In this review, we outline each step of the cGMP signaling cascade and discuss its regulation and physiologic effects within the cardiovascular system. In addition, we illustrate how cGMP signaling becomes dysregulated in specific cardiovascular disease states. The ubiquitous role cGMP plays in cardiac physiology and pathophysiology presents great opportunities for pharmacologic modulation of the cGMP signal in the treatment of cardiovascular diseases. We detail the various therapeutic interventional strategies that have been developed or are in development, summarizing relevant preclinical and clinical studies.

Impact of hypertension on coronary artery spasm as assessed with intracoronary acetylcholine provocation test

Both hypertension and coronary artery spasm (CAS) are associated with endothelial dysfunction. Thus, a higher incidence of CAS is expected in hypertensive patients. We evaluated the impact of hypertension on CAS with intracoronary acetylcholine (ACh) provocation test. A total of 986 patients (685 hypertensive patients vs 301 normotensive patients) who underwent coronary angiography with ACh provocation test were enrolled. ACh was injected into the left coronary artery in incremental doses of 20, 50 and 100 microg min(-1). Significant CAS was defined as a transient >70% luminal narrowing with concurrent chest pain and/or ST-segment changes. Although the incidences of significant ACh-induced CAS were similar between hypertensive and normotensive patients (35.8 vs 39.2%, P=0.303), multivariate logistic analysis showed that hypertension was negatively associated with ACh-induced CAS (odds ratio: 0.70, 95% confidence interval: 0.51-0.94, P=0.020). The angiographic characteristics of ACh-induced CAS were similar between these two groups. Subgroup analysis regarding the impact of the status of blood pressure control on CAS showed that hypertensive patients with controlled blood pressure had a significantly higher incidence of CAS than those with uncontrolled blood pressure (45.2 vs 27.9%, P<0.001), and that uncontrolled blood pressure was negatively associated with ACh-induced CAS (odds ratio: 0.56, 95% confidence interval: 0.40-0.79, P=0.001). In conclusion, despite the expected endothelial dysfunction, hypertension and uncontrolled blood pressure are negatively associated with CAS, suggesting that the mechanisms and risk factors of CAS may be significantly different from those of coronary artery disease.

Coronary artery endothelial dysfunction is positively correlated with low density lipoprotein and inversely correlated with high density lipoprotein subclass particles measured by nuclear magnetic resonance spectroscopy

OBJECTIVE

The association between cholesterol and endothelial dysfunction remains controversial. We tested the hypothesis that lipoprotein subclasses are associated with coronary endothelial dysfunction.

METHODS AND RESULTS

Coronary endothelial function was assessed in 490 patients between November 1993 and February 2007. Fasting lipids and nuclear magnetic resonance (NMR) lipoprotein particle subclasses were measured. There were 325 females and 165 males with a mean age of 49.8+/-11.6 years. Coronary endothelial dysfunction (epicardial constriction>20% or increase in coronary blood flow<50% in response to intracoronary acetylcholine) was diagnosed in 273 patients, the majority of whom (64.5%) had microvascular dysfunction. Total cholesterol and LDL-C (low density lipoprotein cholesterol) were not associated with endothelial dysfunction. One-way analysis and multivariate methods adjusting for age, gender, diabetes, hypertension and lipid-lowering agent use were used to determine the correlation between lipoprotein subclasses and coronary endothelial dysfunction. Epicardial endothelial dysfunction was significantly correlated with total (p=0.03) and small LDLp (LDL particles) (p<0.01) and inversely correlated with total and large HDLp (high density lipoprotein particles) (p<0.01).

CONCLUSIONS

Epicardial, but not microvascular, coronary endothelial dysfunction was associated directly with LDL particles and inversely with HDL particles, suggesting location-dependent impact of lipoprotein particles on the coronary circulation.

Pomegranate juice: a heart-healthy fruit juice

Pomegranate juice is a polyphenol-rich fruit juice with high antioxidant capacity. In limited studies in human and murine models, pomegranate juice has been shown to exert significant antiatherogenic, antioxidant, antihypertensive, and anti-inflammatory effects. Pomegranate juice significantly reduced atherosclerotic lesion areas in immune-deficient mice and intima media thickness in cardiac patients on medications. It also decreased lipid peroxidation in patients with type 2 diabetes, and systolic blood pressure and serum angiotensin converting enzyme activity in hypertensive patients. Thus, the potential cardioprotective benefits of pomegranate juice deserve further clinical investigation, and evidence to date suggests it may be prudent to include this fruit juice in a heart-healthy diet.

Atorvastatin restores endothelial function in offspring of protein-restricted rats in a cholesterol-independent manner

Maternal protein restriction in rats leads to endothelial dysfunction and decreased NO bioavailability in the offspring. Statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) are recognized to have pleiotropic actions including increasing NO bioavailability and reducing inflammation and oxidative damage. This study assessed statin treatment on vascular function in a model of endothelial dysfunction, which is independent of dyslipidemia. Wistar rats were fed a control (18% casein) or protein-restricted (9% casein) diet throughout pregnancy. At weaning, a subset of the protein-restricted group was given atorvastatin (10 mg/kg per day) in the drinking water. At 145 days of age, offspring were euthanized by CO(2) inhalation. Plasma samples were collected for markers of inflammation, vascular reactivity of the thoracic aorta, and small mesenteric arteries were assessed on the wire myograph, and tissues were snap frozen for molecular biology analysis. Thoracic aorta endothelial-dependent vasodilatation was attenuated in the male offspring from both protein-restricted groups compared with controls (P<0.05) but was similar in females (P value not significant). Endothelial-dependent dilatation of mesenteric arteries was attenuated in male and female protein-restricted offspring (P<0.05) and was corrected by atorvastatin. Maternal protein restriction increased plasma inflammatory markers granulocyte chemotactic protein, lipocalin-2, and beta(2)-microglobulin in male and C-reactive protein in female offspring (P<0.05). Atorvastatin had no effect on inflammatory markers in the males but restored C-reactive protein to control levels in the females (P<0.05). Aortic and mesenteric artery mRNA levels of endothelial NO synthase, superoxide dismutase 1, and tumor necrosis factor-alpha were unchanged. These data suggest that atorvastatin can restore endothelial function in this model, but its effects are gender specific and dependent on the vascular bed.

Chemistry and antihypertensive effects of tempol and other nitroxides

Nitroxides can undergo one- or two-electron reduction reactions to hydroxylamines or oxammonium cations, respectively, which themselves are interconvertible, thereby providing redox metabolic actions. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide. It is a cell membrane-permeable amphilite that dismutates superoxide catalytically, facilitates hydrogen peroxide metabolism by catalase-like actions, and limits formation of toxic hydroxyl radicals produced by Fenton reactions. It is broadly effective in detoxifying these reactive oxygen species in cell and animal studies. When administered intravenously to hypertensive rodent models, tempol caused rapid and reversible dose-dependent reductions in blood pressure in 22 of 26 studies. This was accompanied by vasodilation, increased nitric oxide activity, reduced sympathetic nervous system activity at central and peripheral sites, and enhanced potassium channel conductance in blood vessels and neurons. When administered orally or by infusion over days or weeks to hypertensive rodent models, it reduced blood pressure in 59 of 68 studies. This was accompanied by correction of salt sensitivity and endothelial dysfunction and reduced agonist-evoked oxidative stress and contractility of blood vessels, reduced renal vascular resistance, and increased renal tissue oxygen tension. Thus, tempol is broadly effective in reducing blood pressure, whether given by acute intravenous injection or by prolonged administration, in a wide range of rodent models of hypertension.