The vascular endothelium in hypertension

The effect of endothelin a receptor inhibition and biological sex on cutaneous microvascular function in non-Hispanic Black and White young adults

The purpose of this study was to investigate whether endothelin-A receptor (ETAR) inhibition in non-Hispanic Black (NHB) and White (NHW) young adults depends on biological sex. We recruited females during low hormone (n = 22) and high hormone (n = 22) phases, and males (n = 22). Participants self-identified as NHB (n = 33) or NHW (n = 33). Participants were instrumented with two microdialysis fibers: (1) lactated Ringer's (control) and (2) 500 nM BQ-123 (ETAR antagonist). Local heating was used to elicit cutaneous vasodilation, and an infusion of 20 mM L-NAME to quantify NO-dependent vasodilation. At control sites, NO-dependent vasodilation was lowest in NHB males (46 ± 13 %NO) and NHB females during low hormone phases (47 ± 12 %NO) compared to all NHW groups. Inhibition of ETAR increased NO-dependent vasodilation in NHB males (66 ± 13 %NO), in both groups of females during low hormone phases (NHW, control: 64 ± 12 %NO, BQ-123: 85 ± 11 %NO; NHB, BQ-123: 68 ± 13 %NO), and in NHB females during high hormone phases (control: 61 ± 11 %NO, BQ-123: 83 ± 9 %NO). There was no effect for ETAR inhibition in NHW males or females during high hormone phases. These data suggest the effect of ETAR inhibition on NO-dependent vasodilation is influenced by biological sex and racial identity.

Hypertension and Dyslipidemia: the Two Partners in Endothelium-Related Crime

PURPOSE OF REVIEW

The goal of this article is to characterize the endothelium's role in the development of hypertension and dyslipidemia and to point out promising therapeutic directions.

RECENT FINDINGS

Dyslipidemia may facilitate the development of hypertension, whereas the collaboration of these two silent killers potentiates the risk of atherosclerosis. The common pathophysiological denominator for hypertension and dyslipidemia is endothelial cell dysfunction, which manifests as dysregulation of homeostasis, redox balance, vascular tone, inflammation, and thrombosis. Treatment focused on mediators acting in these processes might be groundbreaking. Metabolomic research on hypertension and dyslipidemia has revealed new therapeutic targets. State-of-the-art solutions integrating interview, clinical examination, innovative imaging, and omics profiles along with artificial intelligence have been already shown to improve patients' risk stratification and treatment. Pathomechanisms underlying hypertension and dyslipidemia take place in the endothelium. Novel approaches involving endothelial biomarkers and bioinformatics advances could open new perspectives in patient management.

Paeonol Promotes Reendothelialization After Vascular Injury Through Activation of c-Myc/VEGFR2 Signaling Pathway

Purpose

Dysfunction of endothelium is associated with multiple pathological vascular diseases. However, how to regulate reendothelialization after vascular injury is not well defined. This study aims to determine whether and how Paeonol controls reendothelialization following artery injury.

Methods

The endothelium of murine carotid artery was denuded by catheter guide wires injury. H&E staining and IF staining were performed to determine whether Paeonol is critical for reendothelialization. BRDU Incorporation Assay, Boyden Chamber Migration Assay, Tube Formation Assay, and Spheroid Sprouting Assay were used to investigate whether Paeonol is involved in regulating proliferation and migration of endothelial cells. The underlying mechanism of how Paeonol regulates reendothelialization was determined by Molecular docking simulation and CO-IP Assay.

Results

Paeonol treatment significantly inhibits neointima formation in carotid artery ligation model by promoting proliferation and migration of endothelial cells. Mechanistically, Paeonol enhances c-Myc expression, consequently interacts with VEGFR2 results in activating VEGF signaling pathway, and eventually promotes reendothelialization after vascular injury.

Conclusion

Our data demonstrated that Paeonol plays a critical role in regulating vascular reendothelialization, which may be therapeutically used for treatment of pathological vascular diseases.

Endothelin A receptor inhibition increases nitric oxide-dependent vasodilation independent of superoxide in non-Hispanic Black young adults

Young non-Hispanic Black adults have reduced microvascular endothelial function compared with non-Hispanic White counterparts, but the mechanisms are not fully elucidated. The purpose of this study was to investigate the effect of endothelin-1 A receptor (ET_AR) and superoxide on cutaneous microvascular function in young non-Hispanic Black (n = 10) and White (n = 10) adults. Participants were instrumented with four intradermal microdialysis fibers: 1) lactated Ringer's (control), 2) 500 nM BQ-123 (ET_AR antagonist), 3) 10 μM tempol (superoxide dismutase mimetic), and 4) BQ-123 + tempol. Skin blood flow was assessed via laser-Doppler flowmetry (LDF), and each site underwent rapid local heating from 33°C to 39°C. At the plateau of local heating, 20 mM l-NAME [nitric oxide (NO) synthase inhibitor] was infused to quantify NO-dependent vasodilation. Data are means ± standard deviation. NO-dependent vasodilation was decreased in non-Hispanic Black compared with non-Hispanic White young adults (P < 0.01). NO-dependent vasodilation was increased at BQ-123 sites (73 ± 10% NO) and at BQ-123 + tempol sites (71 ± 10%NO) in non-Hispanic Black young adults compared with control (53 ± 13%NO, P = 0.01). Tempol alone had no effect on NO-dependent vasodilation in non-Hispanic Black young adults (63 ± 14%NO, P = 0.18). NO-dependent vasodilation at BQ-123 sites was not statistically different between non-Hispanic Black and White (80 ± 7%NO) young adults (P = 0.15). ET_AR contributes to reduced NO-dependent vasodilation in non-Hispanic Black young adults independent of superoxide, suggesting a greater effect on NO synthesis rather than NO scavenging via superoxide.NEW & NOTEWORTHY Endothelin-1 A receptors (ET_ARs) have been shown to reduce endothelial function independently and through increased production of superoxide. We show that independent ET_AR inhibition increases microvascular endothelial function in non-Hispanic Black young adults. However, administration of a superoxide dismutase mimetic alone and in combination with ET_AR inhibition had no effect on microvascular endothelial function suggesting that, in the cutaneous microvasculature, the negative effects of ET_AR in non-Hispanic Black young adults are independent of superoxide production.

Endothelial dysfunction: developmental mechanisms and therapeutic strategies

Introduction: Every year the importance of the normal functioning of the endothelial layer of the vascular wall in maintaining the health of the body becomes more and more obvious.

The physiological role of the endothelium: The endothelium is a metabolically active organ actively involved in the regulation of hemostasis, modulation of inflammation, maintenance of hemovascular homeostasis, regulation of angiogenesis, vascular tone, and permeability.

Risk factors for the development of endothelial dysfunction: Currently, insufficient bioavailability of nitric oxide is considered the most significant risk factor for endothelial dysfunction.

Mechanisms of development of endothelial dysfunction: The genesis of endothelial dysfunction is a multifactorial process. Among various complex mechanisms, this review examines oxidative stress, inflammation, hyperglycemia, vitamin D deficiency, dyslipidemia, excess visceral fat, hyperhomocysteinemia, hyperuricemia, as well as primary genetic defect of endotheliocytes, as the most common causes in the population underlying the development of endothelial dysfunction.

Markers of endothelial dysfunction in various diseases: This article discusses the main biomarkers of endothelial dysfunction currently used, as well as promising biomarkers in the future for laboratory diagnosis of this pathology.

Therapeutic strategies: Therapeutic approaches to the endothelium in order to prevent or reduce a degree of damage to the vascular wall are briefly described.

Conclusion: Endothelial dysfunction is a typical pathological process involved in the pathogenesis of many diseases. Thus, pharmacological agents with endothelioprotective properties can provide more therapeutic benefits than a drug without such an effect.

Brain and cardiovascular-related changes are associated with aging, hypertension, and atrial fibrillation

PURPOSE

The neural pathways in which the brain regulates the cardiovascular system is via sympathetic and parasympathetic control of the heart and sympathetic control of the systemic vasculature. Various cortical and sub-cortical sites are involved, but how these critical brain regions for cardiovascular control are altered in healthy aging and other risk conditions that may contribute to cardiovascular disease is uncertain.

METHODS

Here we review the functional and structural brain changes in healthy aging, hypertension, and atrial fibrillation - noting their potential influence on the autonomic nervous system and hence on cardiovascular control.

RESULTS

Evidence suggests that aging, hypertension, and atrial fibrillation are each associated with functional and structural changes in specific areas of the central nervous system involved in autonomic control. Increased muscle sympathetic nerve activity (MSNA) and significant alterations in the brain regions involved in the default mode network are commonly reported in aging, hypertension, and atrial fibrillation.

CONCLUSIONS

Further studies using functional and structural magnetic resonance imaging (MRI) coupled with autonomic nerve activity in healthy aging, hypertension, and atrial fibrillation promise to reveal the underlying brain circuitry modulating the abnormal sympathetic nerve activity in these conditions. This understanding will guide future therapies to rectify dysregulation of autonomic and cardiovascular control by the brain.

Role of Chrononutrition in the Antihypertensive Effects of Natural Bioactive Compounds

Hypertension (HTN) is one of the main cardiovascular risk factors and is considered a major public health problem. Numerous approaches have been developed to lower blood pressure (BP) in hypertensive patients, most of them involving pharmacological treatments. Within this context, natural bioactive compounds have emerged as a promising alternative to drugs in HTN prevention. This work reviews not only the mechanisms of BP regulation by these antihypertensive compounds, but also their efficacy depending on consumption time. Although a plethora of studies has investigated food-derived compounds, such as phenolic compounds or peptides and their impact on BP, only a few addressed the relevance of time consumption. However, it is known that BP and its main regulatory mechanisms show a 24-h oscillation. Moreover, evidence shows that phenolic compounds can interact with clock genes, which regulate the biological rhythm followed by many physiological processes. Therefore, further research might be carried out to completely elucidate the interactions along the time–nutrition–hypertension axis within the framework of chrononutrition.

Therapeutic Effects of Traditional Chinese Medicine on Cardiovascular Diseases: the Central Role of Calcium Signaling

Calcium, as a second messenger, plays an important role in the pathogenesis of cardiovascular diseases (CVDs). The malfunction of calcium signaling in endothelial cells and vascular smooth muscle cells promotes hypertension. In cardiomyocytes, calcium overload induces apoptosis, leading to myocardial infarction and arrhythmias. Moreover, the calcium–calcineurin–nuclear factor of activated T cells (NFAT) pathway is essential for expressing the cardiac pro-hypertrophic gene. Heart failure is also characterized by reduced calcium transient amplitude and enhanced sarcoplasmic reticulum (SR) calcium leakage. Traditional Chinese medicine (TCM) has been used to treat CVDs for thousands of years in China. Because of its multicomponent and multitarget characteristics, TCM's unique advantages in CVD treatment are closely related to the modulation of multiple calcium handling proteins and calcium signaling pathways in different types of cells involved in distinct CVDs. Thus, we systematically review the diverse mechanisms of TCM in regulating calcium pathways to treat various types of CVDs, ranging from hypertrophic cardiomyopathy to diabetic heart disease.

Blood Pressure-Lowering Effect of Wine Lees Phenolic Compounds Is Mediated by Endothelial-Derived Factors: Role of Sirtuin 1

The antihypertensive effect of wine lees powder (WLPW) from a Cabernet grape variety was related to its high content in flavanols and anthocyanins compounds. This study investigates the involvement of endothelial-derived factors and SIRT1 in its bioactivity. Spontaneously hypertensive rats (SHR) were orally administered water or WLPW (125 mg/kg bw). Posteriorly, both groups were intraperitoneally administered saline, Nω-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthesis inhibitor, indomethacin, a prostacyclin synthesis inhibitor, or sirtinol, an inhibitor of sirtuins. Blood pressure (BP) was recorded before and 6 h after WLPW administration. In an additional experiment, SHR were administered water or WLPW and endothelial expressions of eNos, Sirt1, Nox4, and Et1 were determined. The BP-lowering properties of WLPW were abolished by L-NAME and partially reduced by indomethacin, demonstrating that WLPW antihypertensive effect was mediated by changes in NO availability, although prostacyclin also contributed to this activity. Moreover, BP-lowering effect was reduced by sirtinol, indicating that WLPW decreased BP in a SIRT1-dependent manner. Furthermore, WLPW upregulated eNos and Sirt1 and downregulated Nox4 and Et1 endothelial gene expression. These results evidence the vasoprotective effect of WLPW and show that its antihypertensive effect in SHR is endothelium dependent and mediated by SIRT1.

Effects of chronic type 5 phosphodiesterase inhibition on penile microvascular reactivity in hypertensive patients with erectile dysfunction: a randomized crossover placebo-controlled trial

This randomized crossover and placebo-controlled trial evaluated the effects of daily use of sildenafil citrate (SIL, 1-month 50 mg twice daily) on penile and systemic endothelial microvascular function in hypertensive patients presenting with erectile dysfunction. The effects of SIL on arterial pressure were evaluated using ambulatory blood pressure monitoring (ABPM). Fifty patients diagnosed with primary arterial hypertension and erectile dysfunction (aged 57.4 ± 5.6 years), recruited in a tertiary public hospital, were treated with SIL (50 mg twice daily) or placebo (PLA) for two 30-day periods with a 30-day washout between them. Laser speckle contrast imaging coupled with acetylcholine skin iontophoresis was used to evaluate penile and systemic (forearm) cutaneous microvascular reactivity. SIL treatment increased penile basal microvascular flow (P = 0.002) and maximal endothelial-dependent peak response to skin iontophoresis of acetylcholine (ACh, P = 0.006). The area under the curve of microvascular vasodilation induced by ACh was also significantly increased (P = 0.02). Lastly, SIL treatment did not modify systemic microvascular reactivity. Twenty-four-hour ABPM (P = 0.0002) and daytime (P = 0.002) and nighttime (P = 0.001) mean diastolic blood pressure values were significantly reduced after SIL treatment. The scores of the Simplified International Index of Erectile Function (P < 0.0001) and the number of patients with positive responses to Sexual Encounter Profile question 3 (P < 0.0001) also increased after SIL treatment. Penile endothelium-dependent microvascular reactivity improved after continuous use of sildenafil in hypertensive patients with erectile dysfunction; the treatment also reduced blood pressure, suggesting that, in addition to improving erectile function, daily use of sildenafil could improve blood pressure control.

Association study of hypertension susceptibility genes ITGA9, MOV10, and CACNB2 with preeclampsia in Chinese Han population

OBJECTIVE

Preeclampsia (PE) is a disorder that occurs during the pregnancy and could affect the maternal and perinatal mortality as well as morbidity. The aim of our study is to investigate the associations between the hypertension susceptibility genes ITGA9, MOV10 and CACNB2 with PE in Chinese Han population.

METHODS

A case-control study including 178 PE patients and 202 healthy controls was conducted to assess the associations between three loci (ITGA9 rs155524, MOV10 rs2932538 and CACNB2 rs4373814) and PE. The TaqMan probe assay was applied for genotyping in our study. Quantitative real-time PCR was performed to detect the mRNA expression levels of ITGA9, MOV10 and CACNB2. ELISA was carried out to detect the concentration of serum sFlt-1 or PLGF.

RESULTS

Our study detected no significant differences in allelic frequencies of three SNPs between PE patients and healthy controls. In the genetic model, the results showed that the patients with ITGA9 rs155524 GA or AA genotypes had a higher risk of PE development compared to those with GG genotype in codominant model. And PE patients had a higher frequency of GA + AA genotypes based on the dominant model. Subgroup analysis showed ITGA9 rs155524 was associated with early-onset PE but not with late-onset PE. No association was observed between MOV10 and CACNB2 with PE in any genetic model and subgroup analysis. Quantitative real-time PCR results showed that ITGA9 mRNA expression level was apparently increased in the placental tissues of PE patients. In addition, ITGA9 expression levels of GA + AA subjects were apparently higher than that in the genotype GG of placental tissues. sFlt-1/PLGF ratio was higher in GA + AA subjects than that in GG subjects. Regression analysis revealed that ratio of sFlt-1/PLGF was positively correlated with ITGA9 mRNA expression level.

CONCLUSION

This study has identified ITGA9 is a promising candidate susceptibility gene for early-onset PE. Our findings demonstrated that the high expression of ITGA9 might be associated with an increased risk of PE.

Aspirin with or without statin in the treatment of endotheliitis, thrombosis, and ischemia in coronavirus disease

INTRODUCTION

In the genesis of coronavirus disease (COVID-19), there is a process of endotheliitis associated with thrombotic changes, no studies have reported the use of acetylsalicylic acid (ASA) as a possible therapeutic approach. Statins could potentiate the ASA therapy.

METHODS

This is a series of 14 cases with a laboratory-confirmed diagnosis of COVID-19. All patients underwent the ASA therapy. Those who had risk factors for vascular disease also underwent the high-potency statin therapy. When symptoms were totally or practically resolved, patients were discharged and advised to continue medications for a complementary time, according to the clinical evolution of each patient.

RESULTS

The mean age of monitored patients was 48.6 years. A total of 78.6% patients presented with at least one comorbidity, which could have contributed as a risk factor for a poor prognosis in the evolution of COVID-19. Four patients had secondary bacterial infections; three patients needed hospitalization. None of the cases progress to stage III, and all patients had remission of symptoms, with 100% survival.

CONCLUSIONS

the process of endothelial dysfunction in COVID-19 involves disseminated thrombosis, initially microvascular and later expansion into larger vessels. ASA could act as a secondary prophylaxis and prevent thrombosis from developing and reaching stage III of the disease. As this was a case series, we cannot provide definitive conclusions; however, this study allows us to formulate hypotheses and support clinical trials to evaluate benefits of the ASA therapy in the treatment of COVID-19.

Pentacyclic triterpenes: New tools to fight metabolic syndrome

BACKGROUND

Metabolic syndrome is a combination of dysregulated cardiometabolic risk factors characterized by dyslipidemia, impaired glucose tolerance, insulin resistance, inflammation, obesity as well as hypertension. These factors are tied to the increased risk for type-II diabetes and cardiovascular diseases including myocardial infarction in patients with metabolic syndrome.

PURPOSE

To review the proposed molecular mechanisms of pentacyclic triterpenes for their potential use in the metabolic syndrome.

METHODS

PubMed, Science Direct, and Google Scholar database were searched from commencement to April 2018. Following keywords were searched in the databases with varying combinations: "metabolic syndrome", "pentacyclic triterpenes", "transcription factors", "protein kinase", "lipogenesis", "adipogenesis", "lipolysis", "fatty acids", "gluconeogenesis", "cardiovascular", "mitochondria", "oxidative stress", "pancreas", "hepatic cells", "skeletal muscle", "3T3-L1", "C2C12", "obesity", "inflammation", "insulin resistance", "glucose uptake", "clinical studies" and "bioavailability".

RESULTS

Pentacyclic triterpenes, such as asiatic acid, ursolic acid, oleanolic acid, 18β-glycyrrhetinic acid, α,β-amyrin, celastrol, carbenoxolone, corosolic acid, maslinic acid, bardoxolone methyl and lupeol downregulate several metabolic syndrome components by regulating transcription factors, protein kinases and enzyme involved in the adipogenesis, lipolysis, fatty acid oxidation, insulin resistance, mitochondria biogenesis, gluconeogenesis, oxidative stress and inflammation.

CONCLUSION

In vitro and in vivo studies suggests that pentacyclic triterpenes effectively downregulate various factors related to metabolic syndrome. These phytochemicals may serve as promising candidates for clinical trials for the management of metabolic syndrome.

Endothelin A receptor blockade improves endothelium-dependent relaxation in obese woman

Hypertension in obesity is associated with increased insulin resistance, vascular mass and body mass index (BMI). The purpose of the study was to visualize endothelin-1 (ET-1) mediated constriction in arteries isolated from subcutaneous adipose tissue from obese hypertensive women previously operated by gastric bypass. Functional studies were conducted in a microvascular myograph. Expressed as percentage of contraction elicited by 124 mM KCl concentration-response curves for ET-1 were shifted leftward in arteries from obese hypertensive patients compared to healthy normotensive subjects. The vasodilator response to the ET-1 antagonist BQ123 (1 microM) was significantly higher in arteries from obese hypertensive patients (p<0.001). BQ123 induced relaxation was inhibited by NO synthase inhibitor L-NAME (0.1 nM). Preincubation with BQ123 enhanced the relaxation induced by acetylcholine (ACh; 0.1 nM - 0.1 mM) (p<0.001), but not that induced by NO donor sodium nitroprusside (SNP; 0.1 nM - 0.1 mM), in arteries from obese hypertensive patients. The present study show that hypertension yet prevail after gastric bypass surgery and the ET(A) receptor antagonist BQ123 may be a useful tool in reducing blood pressure in obese hypertensive patients.

Hypertension

Systemic arterial hypertension is the most important modifiable risk factor for all-cause morbidity and mortality worldwide and is associated with an increased risk of cardiovascular disease (CVD). Fewer than half of those with hypertension are aware of their condition, and many others are aware but not treated or inadequately treated, although successful treatment of hypertension reduces the global burden of disease and mortality. The aetiology of hypertension involves the complex interplay of environmental and pathophysiological factors that affect multiple systems, as well as genetic predisposition. The evaluation of patients with hypertension includes accurate standardized blood pressure (BP) measurement, assessment of the patients' predicted risk of atherosclerotic CVD and evidence of target-organ damage, and detection of secondary causes of hypertension and presence of comorbidities (such as CVD and kidney disease). Lifestyle changes, including dietary modifications and increased physical activity, are effective in lowering BP and preventing hypertension and its CVD sequelae. Pharmacological therapy is very effective in lowering BP and in preventing CVD outcomes in most patients; first-line antihypertensive medications include angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, dihydropyridine calcium-channel blockers and thiazide diuretics.

Targeting vascular (endothelial) dysfunction

Cardiovascular diseases are major contributors to global deaths and disability-adjusted life years, with hypertension a significant risk factor for all causes of death. The endothelium that lines the inner wall of the vasculature regulates essential haemostatic functions, such as vascular tone, circulation of blood cells, inflammation and platelet activity. Endothelial dysfunction is an early predictor of atherosclerosis and future cardiovascular events. We review the prognostic value of obtaining measurements of endothelial function, the clinical techniques for its determination, the mechanisms leading to endothelial dysfunction and the therapeutic treatment of endothelial dysfunction. Since vascular oxidative stress and inflammation are major determinants of endothelial function, we have also addressed current antioxidant and anti-inflammatory therapies. In the light of recent data that dispute the prognostic value of endothelial function in healthy human cohorts, we also discuss alternative diagnostic parameters such as vascular stiffness index and intima/media thickness ratio. We also suggest that assessing vascular function, including that of smooth muscle and even perivascular adipose tissue, may be an appropriate parameter for clinical investigations.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

The Kidney in Hypertension

Hypertension is the second most common cause of chronic kidney disease (CKD) and is a potentiator of kidney failure when accompanying disease. CKD is a common cause of resistant hypertension. Nephropathy progression has dramatically slowed over the past 3 decades from an average of 8 to between 2-3 mL/min per year regardless of diabetes status. The incidence of very high albuminuria as well as progression from high albuminuria very high albuminuria has substantially decreased over the past 3 decades. This improvement relates to better blood pressure control using agents that slow nephropathy as well as better glycemic and cholesterol control.

Vascular function and endothelin-1: tipping the balance between vasodilation and vasoconstriction

Endothelin-1 (ET-1), a potent vasoconstrictor secreted by vascular endothelial cells, has been implicated in the pathophysiology of numerous cardiovascular diseases, yet the direct impact of ET-1 on vascular function remains unclear. Therefore, in seven young (23 ± 1 yr) healthy subjects, we investigated the effect of an intra-arterial infusion of ET-1 on reactive hyperemia (RH) and flow-mediated dilation (FMD) in the popliteal artery following 5 min of suprasystolic cuff occlusion. ET-1 infusion significantly attenuated basal leg blood flow (control: 62 ± 4 ml/min, ET-1: 47 ± 9 ml/min), RH [area-under-curve (AUC); control: 162 ± 15 ml, ET-1: 104 ± 16 ml], and peak RH (control: 572 ± 51 ml/min, ET-1: 412 ± 32 ml/min) (P < 0.05). Administration of ET-1 also reduced FMD (control: 2.4 ± 0.3%, ET-1: 0.5 ± 0.5%) and FMD normalized for shear rate (control: 10.5 × 10^-4 ± 2.0 × 10^-4%/s^-1, ET-1: 0.9 × 10^-4 ± 2.8 ×10^-4%/s^-1). These findings reveal that elevated levels of ET-1 have a significant impact on vascular function, indicating that studies employing RH and FMD as markers of microvascular function and nitric oxide bioavailability, respectively, should exercise caution, as ET-1 can impact these assessments by tipping the balance between vasodilation and vasoconstriction, in favor of the latter.NEW & NOTEWORTHY Endothelin-1 (ET-1) is recognized as the body's most potent endogenous vasoconstrictor, but the impact of this peptide on vascular function is not well understood. The present study revealed that the intra-arterial administration of ET-1 impaired both microvascular and conduit vessel function of the leg in young, healthy, humans. Studies employing vascular testing in patient cohorts that experience a disease-related increase in ET-1 should thus exercise caution, as ET-1 clearly impairs vascular function.

2-AMINOETHYLDIPHENYLBORINATE MODIFIES THE PULMONARY CIRCULATION IN PULMONARY HYPERTENSIVE NEWBORN LAMBS WITH PARTIAL GESTATION AT HIGH ALTITUDE

Calcium signaling through store operated channels (SOC) is involved in hypoxic pulmonary hypertension. We determined whether a treatment with 2-aminoethyldiphenylborinate (2-APB), a compound with SOC blocker activity, reduces pulmonary hypertension and vascular remodeling. Twelve newborn lambs exposed to perinatal chronic hypoxia were studied, 6 of them received a 2-APB treatment and the other 6 received vehicle treatment, for 10 days in both cases. Throughout this period, we recorded cardiopulmonary variables and on day 11 we evaluated the response to an acute hypoxic challenge. Additionally, we assessed the vasoconstrictor and vasodilator function in isolated pulmonary arteries as well as their remodeling in lung slices. 2-APB reduced pulmonary arterial pressure at the third and tenth days, cardiac output between the fourth and eighth days, and pulmonary vascular resistance at the tenth day of treatment. The pulmonary vasoconstrictor response to acute hypoxia was reduced by the end of treatment. 2-APB also decreased maximal vasoconstrictor response to the thromboxane mimetic U46619 and endothelin-1 and increased maximal relaxation to 8-Br-cGMP. The maximal relaxation and potency to phosphodiesterase-5 and Rho-kinase inhibition with sildenafil and fasudil respectively, were also increased. Finally, 2-APB reduced the medial and adventitial layers' thickness, the expression of α-actin and the percentage of Ki67+ nuclei of small pulmonary arteries. Taken together, our results indicate that 2-APB reduces pulmonary hypertension, vasoconstrictor responses and pathological remodeling in pulmonary hypertensive lambs. We conclude that SOC targeting may be a useful strategy for the treatment of neonatal pulmonary hypertension, however, further testing of specific blockers is needed.

Cilostazol suppresses angiotensin II-induced apoptosis in endothelial cells

Patients with essential hypertension undergo endothelial dysfunction, particularly in the conduit arteries. Cilostazol, a type III phosphodiesterase inhibitor, serves a role in the inhibition of platelet aggregation and it is widely used in the treatment of peripheral vascular diseases. Previous studies have suggested that cilostazol suppresses endothelial dysfunction; however, it remains unknown whether cilostazol protects the endothelial function in essential hypertension. The aim of the present study was to investigate whether, and how, cilostazol suppresses angiotensin II (angII)-induced endothelial dysfunction. Human umbilical vein endothelial cells (HUVECs) and Sprague Dawley rats were exposed to angII and treated with cilostazol. Endothelial cell apoptosis and function, nitric oxide and superoxide production, phosphorylation (p) of Akt, and caspase-3 protein expression levels were investigated. AngII exposure resulted in the apoptosis of endothelial cells in vitro and in vivo. In vitro, cilostazol significantly suppressed the angII-induced apoptosis of HUVECs; however, this effect was reduced in the presence of LY294002, a phosphoinositide 3 kinase (PI3K) inhibitor. Furthermore, cilostazol suppressed the angII-induced p-Akt downregulation and cleaved caspase-3 upregulation. These effects were also alleviated by LY294002. In vivo, cilostazol suppressed the angII-induced endothelial cell apoptosis and dysfunction. Cilostazol was also demonstrated to partially reduced the angII-induced increase in superoxide production. The results of the present study suggested that cilostazol suppresses endothelial apoptosis and dysfunction by modulating the PI3K/Akt pathway.

Chronic arterial hypertension impedes glioma growth: a multiparametric MRI study in the rat

Glioblastoma is the most aggressive brain tumor and is almost always fatal. These tumors are highly vascularized and angiogenesis is one of the pre-eminent mechanisms underlying their growth. Chronic arterial hypertension (CAH) is a common and worldwide pathology that markedlly alters the structure and function of the vasculature. Yet, essential hypertension is associated in the brain with potential locally impaired vasoreactivity, disturbed perfusion supply and hypoxia phenomena. Even though CAH is a global burden and has an important impact on brain function, nothing is known about the way this frequent pathology would interact with the evolution of glioma. We sought to determine if arterial hypertension influences gliobastoma growth. In the present study, rat glioma C6 tumor cells were implanted in the caudate-putamen of spontaneously hypertensive rats (SHR) or their normotensive controls, the Wistar-Kyoto (WKY) rats. The evolution of the tumor was sequentially analyzed by multiparametric magnetic resonance imaging and the inflammatory response was examined by histochemistry. We found that CAH significantly attenuates the growth of the tumor as, at 21 days, the volume of the tumor was 85.4±34.7 and 126.1±28.8 mm(3), respectively, in hypertensive and normotensive rats (P<0.02). Moreover, cerebral blood volume and cerebral blood flow were greater in the tumors of hypertensive rats (P<0.05). The lesser growth of the tumor observed in normotensive animals was not due to an enhanced rejection of the tumor cells in WKY rats, the inflammatory response being similar in both groups. For the first time, these results show that CAH impedes the growth of glioblastoma and illustrate the need to further study the impact of hypertension on the evolution of brain tumors.

Norepinephrine deficiency with normal blood pressure control in congenital insensitivity to pain with anhidrosis

OBJECTIVE

Congenital insensitivity to pain with anhidrosis (CIPA) is caused by mutations in the NKTR1 gene. This affects the development of nerve growth factor (NGF)-dependent neurons including sympathetic cholinergic neurons in the skin, causing anhidrosis. Cardiovascular and blood pressure regulation appears normal, but the integrity of sympathetic adrenergic neurons has not been tested.

METHODS

We examined the effect of posture on blood pressure, heart rate, plasma concentration of catecholamines, vasopressin, endothelin, and renin activity in 14 patients with CIPA, 10 patients with chronically deficient sympathetic activity (pure autonomic failure), and 15 normal age-matched controls.

RESULTS

In all 14 patients with CIPA, plasma norepinephrine levels were very low or undetectable and failed to increase when the patient was upright, yet upright blood pressure was well maintained. Plasma epinephrine levels were normal and increased when the patient was upright. Plasma renin activity also increased appropriately when the patient was upright and after furosemide-induced volume depletion. Nitric oxide-mediated endothelial function was intact. Patients with pure autonomic failure also had very low levels of plasma norepinephrine both supine and upright, but in contrast to patients with CIPA failed to maintain blood pressure upright.

INTERPRETATION

The results indicate that postganglionic sympathetic neurons are severely depleted in CIPA, but chromaffin cells of the adrenal medulla are spared. This confirms the differential effect of NGF signaling for sympathetic neural and chromaffin cell development. The finding that patients with CIPA maintain blood pressure well on standing challenges current concepts of the role of norepinephrine in the regulation of arterial pressure.

Q192R Paraoxonase (PON)1 Polymorphism, Insulin Sensitivity, and Endothelial Function in Essential Hypertensive Men

AIMS

Essential hypertension is characterized by increased reactive oxygen species (ROS) generation harmful for insulin sensitivity and nitric oxide (NO)-mediated vasomotor function, a noxious effect that paraoxonase (PON)1, an antioxidant circulating high-density lipoprotein (HDL)-bound esterase, may counteract. The PON1 gene contains several polymorphisms including a glutamine (Q) to arginine (R) transition at position 192 encoding circulating allozymes with higher antioxidant activity that might influence both parameters.

METHODS

Q192R was determined by polymerase chain reaction in 72 never-treated, glucose-tolerant, uncomplicated essential hypertensive men. Insulin sensitivity was assessed by homeostasis model assessment (HOMA) and endothelial function by forearm vasodilation (strain-gage venous plethysmography) to intra-arterial acetylcholine (ACH) with sodium nitroprusside (NIP) as a NO-independent control. Additional evaluation variables included 24-hour blood pressure (BP), lipids, BMI, smoking status, and metabolic syndrome (MetS) by Adult Treatment Panel (ATP)-III criteria. R192 was considered as the rare allele, and its associations analyzed by dominant models (Q/Q vs. Q/R + R/R).

RESULTS

Genotype frequencies were consistent with the Hardy–Weinberg equilibrium. HOMA was lower and insulin resistance (the upper fourth of HOMA values distribution) less prevalent in Q/R + R/R carriers in whom ACH-mediated vasodilatation was greater and endothelial dysfunction (the bottom fourth of ACH^AUC values distribution) less frequent than in Q/Q homozygotes. Q192R polymorphism and MetS were unrelated parameters despite their common association with insulin resistance. 24-hour BP, BMI, lipids, and smoking habits were homogeneously distributed across genotypes.

CONCLUSIONS

Q192R polymorphism associates differentially with insulin sensitivity and endothelial function in essential hypertensive men.

New evidence for vascular interactions between aldosterone, angiotensin II and antioxidants in isolated smooth muscle cells of rats

Accumulating evidence suggests that the nongenomic cardiovascular actions of aldosterone are produced by varied cellular pathways and mediated by a multitude of messenger systems including the reactive oxygen and nitrogen species. Considering the involvement of the oxidative and nitrosative stress in the pathways leading to the activation of the angiotensin — aldosterone system, in the current study we tried to evaluate the functional interactions between aldosterone, angiotensin II and antioxidants in isolated vascular smooth muscle of aortic rings from rats. Our data provide additional arguments that the nongenomic actions of aldosterone on aortic smooth muscle cells of rats are a question of cross-talk and balance between its rapid vasoconstrictor and vasodilator effects, as result of the activation of reactive oxygen species in the first case and of nitrogen species in the second. In this way, it seems that at low ambient oxidative stress, aldosterone promotes nitric oxide (NO) production and vasodilatation, while in situations with increased oxidative stress the endothelial dysfunction and detrimental effects induced by vasoconstriction will prevail. Thus, aldosterone could be considered both “friend and foe”. This could be relevant for the ways in which aldosterone damages cardiovascular functions and could lead to significant therapeutic improvements.

Nitric oxide: orchestrator of endothelium-dependent responses

The present review first summarizes the complex chain of events, in endothelial and vascular smooth muscle cells, that leads to endothelium-dependent relaxations (vasodilatations) due to the generation of nitric oxide (NO) by endothelial nitric oxide synthase (eNOS) and how therapeutic interventions may improve the bioavailability of NO and thus prevent/cure endothelial dysfunction. Then, the role of other endothelium-derived mediators (endothelium-derived hyperpolarizing (EDHF) and contracting (EDCF) factors, endothelin-1) and signals (myoendothelial coupling) is summarized also, with special emphasis on their interaction(s) with the NO pathway, which make the latter not only a major mediator but also a key regulator of endothelium-dependent responses.

Impaired vasodilation in the pathogenesis of hypertension: focus on nitric oxide, endothelial-derived hyperpolarizing factors, and prostaglandins

Under resting conditions the arterial vasculature exists in a vasoconstricted state referred to as vascular tone. Physiological dilatation in response to increased flow, a function of normal endothelium is necessary to maintain normal blood pressure. Endothelial dysfunction in vascular smooth muscle cells thus results in loss of normal vasorelaxant function and the inability of arteries to appropriately dilate in response to increased blood flow in either a systemic or regional vascular bed, resulting in increased blood pressure, a sequence that may represent a common pathway to hypertension. Normal vasorelaxation is mediated by a number of endothelial systems including nitric oxide (NO), prostaglandins (PGI2 and PGE2), and a family of endothelial-derived hyperpolarizing factors (EDHF). In response to hemodynamic shear stress, endothelium continuously releases NO, EDHF, and PGI2 to provide vasodilatation. EDHF, not a single molecule but rather a group of molecules that includes epoxyeicosatrienoic acids, hydrogen peroxide, carbon monoxide, hydrogen sulfide, C-natriuretic peptide, and K+ itself, causes vasodilatation by activation of vascular smooth muscle cell K+ channels, resulting in hyperpolarization and thus vasorelaxation. The understanding and effective management of blood pressure requires an understanding of both physiologic and pathophysiologic regulation of vascular tone. This review describes molecular mechanisms underlying normal endothelial regulation and pathological states, such as increased oxidative stress, which cause loss of vasorelaxation. Possible pharmacological interventions to restore normal function are suggested.

Effect of carvedilol and nebivolol on oxidative stress-related parameters and endothelial function in patients with essential hypertension

Oxidative stress and endothelial dysfunction have been associated with essential hypertension (EH) mechanisms. The purpose of this study was to evaluate the effect of carvedilol and nebivolol on the oxidative stress-related parameters and endothelial function in patients with EH. The studied population included 57 patients, either sex, between 30 and 75 years of age, with mild-to-moderate EH complications. Participants were randomized to receive either carvedilol (12.5 mg) (n = 23) or nebivolol (5 mg) (n = 21) for 12 weeks. Measurements included; 24-hr ambulatory blood pressure (BP), flow-mediated dilatation, levels of nitric oxide estimated as nitrite - a nitric oxide metabolite ( NO₂) - in plasma, and oxidative stress-related parameters in plasma and erythrocyte. EH patients who were treated with nebivolol or carvedilol showed systolic BP reductions of 17.4 and 19.9 mmHg, respectively, compared with baseline values (p < 0.01). Diastolic BP was reduced by 13.7 and 12.8 mmHg after the treatment with ebivolol and carvedilol, respectively (p < 0.01) (fig. 2B). Nebivolol and carvedilol showed 7.3% and 8.1% higher endothelium-dependent dilatation in relation to baseline values (p < 0.05). Ferric-reducing ability of plasma (FRAP) and reduced glutathione/oxidized glutathione (GSSH) ratio showed 31.5% and 29.6% higher levels in the carvedilol group compared with basal values; however, nebivolol-treated patients did not show significant differences after treatment. On the other hand, the NO₂ plasma concentration was not modified by the administration of carvedilol. However, nebivolol enhanced these levels in 62.1% after the treatment. In conclusion, this study demonstrated the antihypertensive effect of both beta-blockers. However, carvedilol could mediate these effects by an increase in antioxidant capacity and nebivolol through the raise in NO₂ concentration. Further studies are needed to determine the molecular mechanism of these effects.

Effect of Viscum articulatum Burm. (Loranthaceae) in Nω-nitro-L-arginine methyl ester induced hypertension and renal dysfunction

ETHNOPHARMACOLOGICAL RELEVANCE

Viscum articulatum Burm. is used traditionally in Chinese medicine for treating hypertension.

AIM OF THE STUDY

The present study was designed to evaluate the antihypertensive activity of the methanolic extract of Viscum articulatum (MVA) against N(ω)-nitro-L-arginine methyl ester (L-NAME) induced hypertension in rats.

MATERIALS AND METHODS

Six groups of rats were investigated for 4 weeks as normal control, L-NAME (40 mg/kg/day), L-NAME+enalapril (15 mg/kg/day), L-NAME+L-arginine (100 mg/kg/day), L-NAME+MVA (200 mg/kg/day) and L-NAME+MVA (400 mg/kg/day) for four weeks. The systolic blood pressure (SBP) and heart rate (HR) were measured weekly throughout the experimental period. The urine electrolytes concentration, cardiac mass index, serum nitrate/nitrite (NO(x)) level, serum creatinine level and lipid profile were determined.

RESULTS

Treatment with MVA (200 and 400 mg/kg) or enalapril delayed the rise in SBP produced by administration of L-NAME. None of the treatments had a significant effect on the depression of the serum NO(x) level caused by L-NAME. The serum creatinine and total cholesterol concentrations were elevated upon administration of L-NAME, and this elevation was prevented by MVA co-administration. The urine volume and urine potassium ion level were depressed by L-NAME administration and this effect being inhibited in MVA and enalapril groups. There was no cardiac hypertrophy and HR change after 28 day of L-NAME administration.

CONCLUSION

We conclude that MVA may have an antihypertensive effect in the NO deficient type of hypertension, which may be attributed to its diuretic, nephroprotective and hypolipidemic actions.

Elevated endothelin-1 vasoconstrictor tone in prehypertensive adults

BACKGROUND

Prehypertension (blood pressure [BP] 120-139/80-89 mm Hg) is an independent risk factor for hypertension and cardiovascular disease. Currently, it is unknown whether endothelin (ET)-1-mediated vasoconstrictor tone is elevated with BP in the prehypertensive range. The aims of this study were to determine whether ET-1 vasoconstrictor tone is elevated in prehypertensive adults and, if so, whether ET-1-mediated vasoconstriction contributes to endothelial vasodilator dysfunction in this population.

METHODS

Forearm blood flow responses to selective ET(A) receptor blockade (BQ-123; 100 nmol/min) were determined in 26 normotensive adults (age 55 ± 1 years; BP 112 ± 1/72 ± 1 mm Hg) and 30 prehypertensive adults (57 ± 1 years; BP 130 ± 1/80 ± 1 mm Hg). In a subset of participants, forearm blood flow responses to nonselective ET-1 receptor blockade (BQ-123 + BQ-788) were determined. Endothelium-dependent vasodilation to acetylcholine (8.0-32.0 μg/100 mL tissue/min) was measured in the absence and presence of selective ET(A) receptor blockade.

RESULTS

BQ-123 elicited a significantly greater increase in forearm blood flow in prehypertensive (approximately 20%) than in normotensive (approximately 5%) adults. Addition of BQ-788 resulted in a further increase (P < 0.05) in forearm blood flow in prehypertensive but not in normotensive adults. Forearm blood flow responses to acetylcholine were lower (P < 0.05) in prehypertensive (4.6 ± 0.3 to 12.6 ± 0.5 mL/100 mL tissue/min) than in normotensive (4.9 ± 0.3 to 14.7 ± 0.8 mL/100 mL tissue/min) adults. Co-infusion of BQ-123 did not affect acetylcholine-induced vasodilation in normotensive adults but resulted in an approximately 20% increase (P < 0.05) in prehypertensive adults.

CONCLUSIONS

ET-1-mediated vasoconstrictor tone is elevated with prehypertension, contributing to impaired endothelium-dependent vasodilation. ET-1 vasoconstriction may underlie the increased risk of hypertension and cardiovascular disease in prehypertensive adults.

Effects of Pycnogenol on endothelial function in patients with stable coronary artery disease: a double-blind, randomized, placebo-controlled, cross-over study

AIMS

Extracts from pine tree bark containing a variety of flavonoids have been used in traditional medicine. Pycnogenol is a proprietary bark extract of the French maritime pine tree (Pinus pinaster ssp. atlantica) that exerts antioxidative, anti-inflammatory, and anti-platelet effects. However, the effects of Pycnogenol on endothelial dysfunction, a precursor of atherosclerosis and cardiovascular events, remain still elusive.

METHODS AND RESULTS

Twenty-three patients with coronary artery disease (CAD) completed this randomized, double-blind, placebo-controlled cross-over study. Patients received Pycnogenol (200 mg/day) for 8 weeks followed by placebo or vice versa on top of standard cardiovascular therapy. Between the two treatment periods, a 2-week washout period was scheduled. At baseline and after each treatment period, endothelial function, non-invasively assessed by flow-mediated dilatation (FMD) of the brachial artery using high-resolution ultrasound, biomarkers of oxidative stress and inflammation, platelet adhesion, and 24 h blood pressure monitoring were evaluated. In CAD patients, Pycnogenol treatment was associated with an improvement of FMD from 5.3 ± 2.6 to 7.0 ± 3.1 (P < 0.0001), while no change was observed with placebo (5.4 ± 2.4 to 4.7 ± 2.0; P = 0.051). This difference between study groups was significant [estimated treatment effect 2.75; 95% confidence interval (CI): 1.75, 3.75, P < 0.0001]. 15-F(2t)-Isoprostane, an index of oxidative stress, significantly decreased from 0.71 ± 0.09 to 0.66 ± 0.13 after Pycnogenol treatment, while no change was observed in the placebo group (mean difference 0.06 pg/mL with an associated 95% CI (0.01, 0.11), P = 0.012]. Inflammation markers, platelet adhesion, and blood pressure did not change after treatment with Pycnogenol or placebo.

CONCLUSION

This study provides the first evidence that the antioxidant Pycnogenol improves endothelial function in patients with CAD by reducing oxidative stress.

Vascular effects of glycoprotein130 ligands--part I: pathophysiological role

The vessel wall is no longer considered as only an anatomical barrier for blood cells but is recognized as an active endocrine organ. Dysfunction of the vessel wall occurs in various disease processes including atherosclerosis, hypertension, peripheral artery disease, aneurysms, and transplant and diabetic vasculopathies. Different cytokines were shown to modulate the behavior of the cells, which constitute the vessel wall such as immune cells, endothelial cells and smooth muscle cells. Glycoprotein 130 (gp130) is a common cytokine receptor that controls the activity of a group of cytokines, namely, interleukin (IL)-6, oncostatin M (OSM), IL-11, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), cardiotrophin-like cytokine (CLC), IL-27, and neuropoietin (NP). Gp130 and associated cytokines have abundantly diverse functions. Part I of this review focuses on the pathophysiological functions of gp130 ligands. We specifically describe vascular effects of these molecules and discuss the respective underlying molecular and cellular mechanisms.

Meconium aspiration delays normal decline of pulmonary vascular resistance shortly after birth through lung parenchymal injury

BACKGROUND

Persistent pulmonary hypertension of the newborn is often associated with meconium aspiration syndrome (MAS) or perinatal asphyxia.

OBJECTIVE

To determine the effect of meconium or asphyxia on pulmonary arterial pressure and circulating levels of vasoactive substances, we conducted a prospective study of 54 term infants, including infants with meconium-stained amniotic fluid with normal (MSAF) or abnormal (MAS) chest X-ray findings, infants with perinatal asphyxia, and controls. The purpose of this study was to determine the group most likely to have elevated pulmonary arterial pressure and a disturbed balance between vasoactive substances.

METHODS

To estimate the pulmonary arterial pressure by echocardiography, we used the ratio of the right to left systolic ventricular pressure (RVP/LVP ratio). We measured the plasma concentrations of endothelin-1 (ET-1), cyclic guanosine monophosphate (cGMP) as an indicator of nitric oxide (NO) production, and 6-keto-prostaglandin F(1)α (6-keto-PGF(1)α) for the estimation of prostacyclin concentration. We also measured KL-6 as a marker of lung injury.

RESULTS

The RVP/LVP ratio was significantly higher in the MAS group than the other groups on day 0. Although ET-1 and 6-keto-PGF(1)α levels were comparable among all groups, the cGMP level on days 3-5 and the KL-6 level throughout the first postnatal week were significantly higher in the MAS group.

CONCLUSIONS

It is possible that meconium aspiration delays normal decline of pulmonary vascular resistance shortly after birth through lung parenchymal injury. The subsequent increase of cGMP in MAS may be an adaptive response to prevent further elevation of pulmonary arterial pressure by inducing NO.

Effects of chronic treatment with honokiol in spontaneously hypertensive rats

The present study was performed to evaluate the antihypertensive effects of honokiol in vivo in spontaneously hypertensive rats (SHR). The effects of honokiol were investigated by determination of the blood pressure, vascular reactivity, oxidative parameters, and histologic change in the aorta. Long-term administration of honokiol (400 mg/kg/d) to SHR decreased systolic blood pressure significantly. Honokiol (200, 400 mg/kg/d) enhanced the aortic relaxation in response to acetylcholine after 49-d treatment, but had no significant effects on the relaxation to sodium nitroprusside. The oral administration of honokiol significantly increased the plasma level of NO(2(-))/NO(3(-)), but decreased the level of malondialdehyde in liver of SHR compared with the control vehicle. In addition, SHR administered honokiol showed significant reductions in the elastin bands and media thickness in the aorta. These results suggest that chronic treatment with honokiol exerts an antihypertensive effect in SHR, and its vasorelaxant action and antioxidant properties may contribute to reducing the elevated blood pressure.

Endothelium-derived vasoactive factors and hypertension: possible roles in pathogenesis and as treatment targets

Endothelial cells regulate vascular tone by releasing various contracting and relaxing factors including nitric oxide (NO), arachidonic acid metabolites (derived from cyclooxygenases, lipoxygenases, and cytochrome P450 monooxygenases), reactive oxygen species, and vasoactive peptides. Additionally, another pathway associated with the hyperpolarization of the underlying smooth muscle cells plays a predominant role in resistance arteries. Endothelial dysfunction is a multifaceted disorder, which has been associated with hypertension of diverse etiologies, involving not only alterations of the L-arginine NO-synthase-soluble guanylyl cyclase pathway but also reduced endothelium-dependent hyperpolarizations and enhanced production of contracting factors, particularly vasoconstrictor prostanoids. This brief review highlights these different endothelial pathways as potential drug targets for novel treatments in hypertension and the associated endothelial dysfunction and end-organ damage.

Hormonal modulation of endothelial NO production

Since the discovery of endothelium-derived relaxing factor and the subsequent identification of nitric oxide (NO) as the primary mediator of endothelium-dependent relaxations, research has focused on chemical and physical stimuli that modulate NO levels. Hormones represent a class of soluble, widely circulating chemical factors that impact production of NO both by rapid effects on the activity of endothelial nitric oxide synthase (eNOS) through phosphorylation of the enzyme and longer term modulation through changes in amount of eNOS protein. Hormones that increase NO production including estrogen, progesterone, insulin, and growth hormone do so through both of these common mechanisms. In contrast, some hormones, including glucocorticoids, progesterone, and prolactin, decrease NO bioavailability. Mechanisms involved include binding to repressor response elements on the eNOS gene, competing for co-regulators common to hormones with positive genomic actions, regulating eNOS co-factors, decreasing substrate for eNOS, and increasing production of oxygen-derived free radicals. Feedback regulation by the hormones themselves as well as the ability of NO to regulate hormonal release provides a second level of complexity that can also contribute to changes in NO levels. These effects on eNOS and changes in NO production may contribute to variability in risk factors, presentation of and treatment for cardiovascular disease associated with aging, pregnancy, stress, and metabolic disorders in men and women.

Vascular KCa-channels as therapeutic targets in hypertension and restenosis disease

IMPORTANCE OF THE FIELD

Cardiovascular disease is a leading cause of death in modern societies. Hyperpolarizing Ca(2+)-activated K(+) channels (K(Ca)) are important membrane proteins in the control of arterial tone and pathological vascular remodelling and thus could serve as new drug targets.

AREAS COVERED IN THIS REVIEW

We summarize recent advances in the field of vascular K(Ca) and their roles in cardiovascular pathologies such as hypertension and restenosis disease and draw attention to novel small-molecule channel modulators and their possible therapeutic utility. This review focuses on literature from the last four to five years.

WHAT THE READER WILL GAIN

Pharmacological opening of endothelial KCa3.1/KCa2.3 channels stimulates endothelium-derived-hyperpolarizing-factor-mediated arteriolar dilation and lowers blood pressure. Inhibition of smooth muscle KCa3.1 channels has beneficial effects in restenosis disease and atherosclerosis. We consider the therapeutic potential of KCa3.1/KCa2.3 openers as novel endothelium-specific antihypertensive drugs as well as of KCa3.1-blockers for the treatment of pathological vascular remodelling and discuss advantages and disadvantages of the pharmacotherapeutic approaches.

TAKE HOME MESSAGE

Pharmacological manipulation of vascular K(Ca) channels by novel small-molecule modulators offers new venues for alternative treatments of hypertension, restenosis and atherosclerosis. Additional efforts are required to optimize these compounds and to validate them as cardiovascular-protective drugs.

Relationship between upper limb peripheral artery stiffness using the radial artery and atherosclerotic parameters

PURPOSE

A new method has been developed for evaluating arterial stiffness using transcutaneous and high-frequency ultrasound. There may be a difference in the clinical significance of peripheral arteries, such as the radial artery (a muscular property), and other medium/large-sized arteries (an elastic property). The aim of this study was to determine the relationship between upper limb peripheral arterial stiffness (ULPAS) using the new method for the radial artery and atherosclerotic parameters in comparison with carotid intima-media thickness (IMT) and cardio-ankle vascular index (CAVI) in a healthy population and a diseased population with hypertension (HT) and diabetes mellitus (DM).

METHODS

Forty-four apparently healthy individuals (mean age = 26.3 years, men/women = 14/30), 45 patients with drug-treated HT (mean age = 55.3 years, men/women = 17/28), and 37 patients with drug-treated DM (mean age = 55.2 years, men/women = 21/16) were investigated. Body mass index, systolic blood pressure (SBP), diastolic blood pressure (DBP), CAVI, IMT, ultrasonographically measured ULPAS, blood lipid/glucose-related parameters, and C-reactive protein (CRP) were all determined.

RESULTS

Among the healthy subjects, ULPAS showed a significantly positive correlation with SBP and CRP. ULPAS showed a different correlation pattern with atherosclerotic parameters from that of IMT and CAVI. The HT subjects had significantly higher ULPAS levels than those with DM. In this diseased population, ULPAS showed a significant positive correlation with SBP and DBP, as well as a significant negative correlation with glucose.

CONCLUSION

These results suggest that ULPAS may provide new information in association with some atherosclerotic conditions as a unique index different from IMT and CAVI.

Using basic science to design a clinical trial: baseline characteristics of women enrolled in the Kronos Early Estrogen Prevention Study (KEEPS)

Observational and epidemiological studies suggest that menopausal hormone therapy (MHT) reduces cardiovascular disease (CVD) risk. However, results from prospective trials showed neutral or adverse effects most likely due to differences in participant demographics, such as age, timing of initiation of treatment, and preexisting cardiovascular disease, which reflected in part the lack of basic science information on mechanisms of action of hormones on the vasculature at the time clinical trials were designed. The Kronos Early Estrogen Replacement Study (KEEPS) is a prospective, randomized, controlled trial designed, using findings from basic science studies, to test the hypothesis that MHT when initiated early in menopause reduces progression of atherosclerosis. KEEPS participants are younger, healthier, and within 3 years of menopause thus matching more closely demographics of women in prior observational and epidemiological studies than women in the Women's Health Initiative hormone trials. KEEPS will provide information relevant to the critical timing hypothesis for MHT use in reducing risk for CVD.

Endothelial Ca+-activated K+ channels in normal and impaired EDHF-dilator responses--relevance to cardiovascular pathologies and drug discovery

The arterial endothelium critically contributes to blood pressure control by releasing vasodilating autacoids such as nitric oxide, prostacyclin and a third factor or pathway termed 'endothelium-derived hyperpolarizing factor' (EDHF). The nature of EDHF and EDHF-signalling pathways is not fully understood yet. However, endothelial hyperpolarization mediated by the Ca(2+)-activated K(+) channels (K(Ca)) has been suggested to play a critical role in initializing EDHF-dilator responses in conduit and resistance-sized arteries of many species including humans. Endothelial K(Ca) currents are mediated by the two K(Ca) subtypes, intermediate-conductance K(Ca) (KCa3.1) (also known as, a.k.a. IK(Ca)) and small-conductance K(Ca) type 3 (KCa2.3) (a.k.a. SK(Ca)). In this review, we summarize current knowledge about endothelial KCa3.1 and KCa2.3 channels, their molecular and pharmacological properties and their specific roles in endothelial function and, particularly, in the EDHF-dilator response. In addition we focus on recent experimental evidences derived from KCa3.1- and/or KCa2.3-deficient mice that exhibit severe defects in EDHF signalling and elevated blood pressures, thus highlighting the importance of the KCa3.1/KCa2.3-EDHF-dilator system for blood pressure control. Moreover, we outline differential and overlapping roles of KCa3.1 and KCa2.3 for EDHF signalling as well as for nitric oxide synthesis and discuss recent evidence for a heterogeneous (sub) cellular distribution of KCa3.1 (at endothelial projections towards the smooth muscle) and KCa2.3 (at inter-endothelial borders and caveolae), which may explain their distinct roles for endothelial function. Finally, we summarize the interrelations of altered KCa3.1/KCa2.3 and EDHF system impairments with cardiovascular disease states such as hypertension, diabetes, dyslipidemia and atherosclerosis and discuss the therapeutic potential of KCa3.1/KCa2.3 openers as novel types of blood pressure-lowering drugs.

Hypertension in mice lacking the CXCR3 chemokine receptor

The CXC chemokine receptor 3 (CXCR3) has been linked to autoimmune and inflammatory disease, allograft rejection, and ischemic nephropathy. CXCR3 is expressed on endothelial and smooth muscle cells. Although a recent study posited that antagonizing of CXCR3 function may reduce atherosclerosis, the role of CXCR3 in controlling physiological vascular functions remains unclear. This study demonstrates that disruption of CXCR3 leads to elevated mean arterial pressures in anesthetized and conscious mice, respectively. Stimulation of isolated resistance vessels with various vasoconstrictors showed increased contractibility in CXCR3-/- mice in response to angiotensin II (ANG II) and a decreased vasodilatation in response to acetylcholine (ACh). The increased contractibility was related to higher ANG II type 1 receptor (AT1R) expression, whereas the decreased vasodilatation was related to lower M3-ACh receptor expression in the mesenteric arteries of CXCR3-/- mice compared with wild-type mice. The vasodilatatory response to ACh could be antagonized by the nonselective ACh receptor antagonist atropine and the selective M3 receptor antagonist 4-DAMP, but not by M1, M2, and M4 receptor antagonists. Additionally, EMSA studies revealed that transcription factors SP-1 and EGR-1 interact as a complex with the murine AT1R promoter region. Furthermore, we could show increased expression of SP-1 in CXCR3-/- mice indicating an imbalanced SP-1 and EGR-1 complex formation which causes increased AT1R expression and hypertension. The data indicate that CXCR3 receptor is important in vascular contractility and hypertension, possibly through upregulated AT1R expression.

In vivo imaging of renal redox status during azelnidipine treatment

The effect of the calcium channel blocker azelnidipine on the redox status of a murine hypertension model was analyzed and imaged using in vivo low frequency electron paramagnetic resonance (EPR). A murine two kidney-one clip (2K1C) hypertension model was produced by a clipping of the right renal artery. The resulting hypertensive mice were treated with low-dose azelnidipine (1 mg/kg/d), with high-dose azelnidipine (3 mg/kg/d) or without azelnidipine (HT group). An EPR system equipped with a loop-gap resonator and an imaging system was employed. Redox status was evaluated as organ reducing activity measured by means of the decay rate (half-lives) of the spin probe 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (Carbamoyl-PROXYL). Four weeks after clipping the mice demonstrated hypertension as expected. After the additional 2 weeks of azelnidipine treatments, the Carbamoyl-PROXYL half-lives of the Low and High azelnidipine groups measured in the upper abdominal area were significantly shorter than those of the HT group, suggesting improvements in the reducing activity. The blood pressures of the three groups showed no significant differences at this time, and there was no correlation between the renal reducing activity and either blood pressure or serum creatinine values. EPR imaging studies revealed that the improvement in abdominal reducing activity was mainly recognized in the kidney but not in the liver. These results indicate that azelnidipine ameliorates renal redox status through an improvement in reducing activity independent of blood pressure control.

S-nitrosylation of beta-arrestin regulates beta-adrenergic receptor trafficking

Signal transduction through G protein-coupled receptors (GPCRs) is regulated by receptor desensitization and internalization that follow agonist stimulation. Nitric oxide (NO) can influence these processes, but the cellular source of NO bioactivity and the effects of NO on GPCR-mediated signal transduction are incompletely understood. Here, we show in cells and mice that beta-arrestin 2, a central element in GPCR trafficking, interacts with and is S-nitrosylated at a single cysteine by endothelial NO synthase (eNOS), and that S-nitrosylation of beta-arrestin 2 is promoted by endogenous S-nitrosogluthathione. S-nitrosylation after agonist stimulation of the beta-adrenergic receptor, a prototypical GPCR, dissociates eNOS from beta-arrestin 2 and promotes binding of beta-arrestin 2 to clathrin heavy chain/beta-adaptin, thereby accelerating receptor internalization. The agonist- and NO-dependent shift in the affiliations of beta-arrestin 2 is followed by denitrosylation. Thus, beta-arrestin subserves the functional coupling of eNOS and GPCRs, and dynamic S-nitrosylation/denitrosylation of beta-arrestin 2 regulates stimulus-induced GPCR trafficking.