Saphenous vein endothelin system expression and activity in African American patients

Aprocitentan for Blood Pressure Reduction in Black Patients

BACKGROUND

Black individuals frequently present with resistant hypertension and disproportionately increased cardiovascular risk. We investigated the blood pressure (BP)-lowering effect of the dual endothelin receptor antagonist aprocitentan in Black individuals enrolled in the PRECISION study (Parallel-Group, Phase 3 Study with Aprocitentan in Subjects with Resistant Hypertension).

METHODS

Patients with confirmed resistant hypertension were randomized to aprocitentan 12.5 mg, 25 mg, or placebo for 4 weeks (part 1). They subsequently received aprocitentan 25 mg for 32 weeks (part 2) before re-randomization to aprocitentan 25 mg or placebo (part 3).

RESULTS

Eighty-two patients randomized in the PRECISION study were Black individuals. At week 4, aprocitentan 12.5 and 25 mg reduced office trough systolic BP (-11.3 and -11.9 mm Hg) to a similar degree as placebo (-12.0 mm Hg). Using 24-hour ambulatory BP monitoring, the placebo effect was minimal (-0.7 mm Hg), and aprocitentan reduced systolic BP by 4.0 and 8.6 mm Hg. During part 2, office BP continued to decrease (-16.4 mm Hg at week 36). In part 3, office and ambulatory systolic BP increased on placebo (+9.9 and +8.1 mm Hg, respectively), whereas the BP-lowering effect was maintained with aprocitentan. Aprocitentan markedly reduced albuminuria during the study. The most frequent adverse event was peripheral edema, occurring in 3 patients (10%) receiving aprocitentan 25 mg versus none receiving aprocitentan 12.5 mg or placebo.

CONCLUSIONS

Aprocitentan reduced BP and albuminuria in Black individuals with resistant hypertension. The BP-lowering efficacy was similar to that of the overall PRECISION population. Aprocitentan may represent an important addition to the often difficult-to-control hypertension in Black individuals.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03541174.

Sex differences in sympathetic transduction in black and white adults: implications for racial disparities in hypertension and cardiovascular disease risk

The prevalence of hypertension in non-Hispanic black (BL) individuals is the greatest of any racial/ethnic group. Whereas women generally display lower rates of hypertension than men of the same background, BL women display a similar if not greater burden of hypertension compared with BL men. The risk for cardiovascular disease and related events is also highest in BL individuals. Given the importance of the sympathetic nervous system for the regulation of the cardiovascular system, a growing body of literature has investigated sympathetic function in BL and non-Hispanic white (WH) individuals. Here, we are focused on emerging evidence indicating that sympathetic function may be altered in BL individuals, with particular emphasis on the process by which bursts of muscle sympathetic nerve activity (MSNA) are transduced into vasoconstriction and increases in blood pressure (sympathetic vascular transduction). To synthesize this growing body of literature we discuss sex and race differences in 1) sympathetic outflow, 2) sympathetic vascular transduction, and 3) adrenergic receptor sensitivity. Sex differences are discussed foremost, to set the stage for new data indicating a sex dimorphism in sympathetic regulation in BL individuals. Specifically, we highlight evidence for a potential neurogenic phenotype including greater adiposity-independent sympathetic outflow and enhanced sympathetic vascular transduction in BL men that is not observed in BL women. The implications of these findings for the greater hypertension and cardiovascular disease risk in BL adults are discussed along with areas that require further investigation.

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.

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.

Dual endothelin antagonist aprocitentan for resistant hypertension (PRECISION): a multicentre, blinded, randomised, parallel-group, phase 3 trial

BACKGROUND

Resistant hypertension is associated with increased cardiovascular risk. The endothelin pathway has been implicated in the pathogenesis of hypertension, but it is currently not targeted therapeutically, thereby leaving this relevant pathophysiological pathway unopposed with currently available drugs. The aim of the study was to assess the blood pressure lowering efficacy of the dual endothelin antagonist aprocitentan in patients with resistant hypertension.

METHODS

PRECISION was a multicentre, blinded, randomised, parallel-group, phase 3 study, which was done in hospitals or research centres in Europe, North America, Asia, and Australia. Patients were eligible for randomisation if their sitting systolic blood pressure was 140 mm Hg or higher despite taking standardised background therapy consisting of three antihypertensive drugs, including a diuretic. The study consisted of three sequential parts: part 1 was the 4-week double-blind, randomised, and placebo-controlled part, in which patients received aprocitentan 12·5 mg, aprocitentan 25 mg, or placebo in a 1:1:1 ratio; part 2 was a 32-week single (patient)-blind part, in which all patients received aprocitentan 25 mg; and part 3 was a 12-week double-blind, randomised, and placebo-controlled withdrawal part, in which patients were re-randomised to aprocitentan 25 mg or placebo in a 1:1 ratio. The primary and key secondary endpoints were changes in unattended office systolic blood pressure from baseline to week 4 and from withdrawal baseline to week 40, respectively. Secondary endpoints included 24-h ambulatory blood pressure changes. The study is registered on ClinicalTrials.gov, NCT03541174.

FINDINGS

The PRECISION study was done from June 18, 2018, to April 25, 2022. 1965 individuals were screened and 730 were randomly assigned. Of these 730 patients, 704 (96%) completed part 1 of the study; of these, 613 (87%) completed part 2 and, of these, 577 (94%) completed part 3 of the study. The least square mean (SE) change in office systolic blood pressure at 4 weeks was -15·3 (SE 0·9) mm Hg for aprocitentan 12·5 mg, -15·2 (0·9) mm Hg for aprocitentan 25 mg, and -11·5 (0·9) mm Hg for placebo, for a difference versus placebo of -3·8 (1·3) mm Hg (97·5% CI -6·8 to -0·8, p=0·0042) and -3·7 (1·3) mm Hg (-6·7 to -0·8; p=0·0046), respectively. The respective difference for 24 h ambulatory systolic blood pressure was -4·2 mm Hg (95% CI -6·2 to -2·1) and -5·9 mm Hg (-7·9 to -3·8). After 4 weeks of withdrawal, office systolic blood pressure significantly increased with placebo versus aprocitentan (5·8 mm Hg, 95% CI 3·7 to 7·9, p<0·0001). The most frequent adverse event was mild-to-moderate oedema or fluid retention, occurring in 9%, 18%, and 2% for patients receiving aprocitentan 12·5 mg, 25 mg, and placebo, during the 4-week double-blind part, respectively. This event led to discontinuation in seven patients treated with aprocitentan. During the trial, a total of 11 treatment-emergent deaths occurred, none of which were regarded by the investigators to be related to study treatment.

INTERPRETATION

In patients with resistant hypertension, aprocitentan was well tolerated and superior to placebo in lowering blood pressure at week 4 with a sustained effect at week 40.

FUNDING

Idorsia Pharmaceuticals and Janssen Biotech.

Aprocitentan and the endothelin system in resistant hypertension

Endothelin has emerged as a target for therapeutic intervention in systemic hypertension. As a vasoconstrictor, co-mitogenic agent, linking pulse pressure and vascular remodeling, and mediator of aldosterone and catecholamine release, endothelin is a key player in hypertension and end-organ damage. In 10-20% of the hypertensive population, the high blood pressure is resistant to administration of antihypertensive drugs of different classes in combination. Because endothelin is not targeted by the current antihypertensive drugs this may suggest that this resistance is due, in part at least, to a dependence on endothelin. This hypothesis is supported by the observation that this form of hypertension is often salt-sensitive, and that the endothelin system is stimulated by salt. In addition, the endothelin system is activated in subjects at risk of developing resistant hypertension, such as African-Americans or patients with obesity or obstructive sleep apnea. Aprocitentan is a novel, potent, dual endothelin receptor antagonist (ERA) currently in phase 3 development for the treatment of difficult-to-treat hypertension. This article discusses the research which underpinned the discovery of this ERA and the choice of its first clinical indication for patients with forms of hypertension which cannot be well controlled with classical antihypertensive drugs.

Contributions of endothelin-1 and l-arginine to blunted cutaneous microvascular function in young, black women

Non-Hispanic black (BL) individuals have the greatest prevalence of cardiovascular disease (CVD), relative to other racial/ethnic groups (e.g., non-Hispanic white population; WH), which may be secondary to blunted vascular function. Although women typically present with reduced CVD relative to men of the same racial/ethnic group, the prevalence is similar between BL women and men though the mechanisms differ. This study hypothesized that reduced microvascular function in young, BL women is associated with endothelin-1 (ET-1) overactivity or insufficient l-arginine bioavailability. Nine BL and nine WH women participated (age: 20 ± 2 vs. 22 ± 2 yr). Cutaneous microvascular function was assessed during 39°C local heating, whereas lactated Ringer's (control), BQ-123 (ET-1 receptor type A antagonist), BQ-788 (ET-1 receptor type B antagonist), or l-arginine were infused via intradermal microdialysis to modify cutaneous vascular conductance (CVC). Subsequent infusion of N^ω-nitro-l-arginine methyl ester allowed for quantification of the nitric oxide (NO) contribution to vasodilation, whereas combined sodium nitroprusside and 43°C heating allowed for normalization to maximal CVC (%CVC_max). BL women had blunted %CVC_max and NO contribution to dilation during the 39°C plateau (P < 0.027 for both). BQ-123 improved this response through augmented NO-mediated dilation (P < 0.048 for both). BQ-788 and l-arginine did not alter the CVC responses (P > 0.835 for both) or the NO contribution (P > 0.371 for both). Cutaneous microvascular function is reduced in BL women, and ET-1 receptor type A may contribute to this reduced function. Further research is needed to better characterize these mechanisms in young, BL women.NEW & NOTEWORTHY Cardiovascular disease remains a burden in the United States non-Hispanic black (BL) population, although its manifestation through blunted vasodilation in this population is different between men and women. Accordingly, this study determined that reduced microvascular function in young, BL women may be partially controlled by endothelin-1 (ET-1) type A receptors, although neither type B receptors nor insufficient l-arginine bioavailability seems to contribute to this response. Accordingly, further research is needed to better characterize these ET-1 related mechanisms and illuminate other pathways that may contribute to this disparate vascular function in young, BL women.

Dysregulation of Endothelin-1: Implications for Health Disparities in Alzheimer's Disease

Alzheimer's disease (AD) and related dementias disproportionately impact racial and ethnic minorities. The racial and ethnic disparities in AD could be explained by differences in cerebral vascular disease pathology. Endothelin-1 (ET-1) is a potent vasoconstrictive peptide that regulates smooth muscle, endothelial cell, and pericyte contractions that may result in cerebral vascular constriction, leading to cerebral hypoperfusion; over time, ET-1 may result in neuronal injury contributing to the pathology of AD. Upregulation of the ET-1 system has been observed in African Americans when compared with non-Hispanic Whites. The role of the ET-1 system as a driver of ethnic disparities in AD requires further investigation. Targeting of the ET-1 system as a therapeutic intervention that could impact AD progression also needs further study. Dysregulation of ET-1 in Hispanic/Latino populations largely have been unexplored. Genetics linking ET-1 dysregulation and racial disparities in AD also needs further investigation. In this review, I examine how AD effects underserved minority populations and how dysregulation of the ET-1 system specifically predisposes ethnic minorities to AD. In addition, I examine the molecular interactions of the ET-1 system and amyloid beta, the role the ET-1 system in neurodegeneration, potential therapeutics for ET-1 dysregulation, and the impact on AD progression.

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.

Disparities in vascular surgery: is it biology or environment?

Disparities in health care are well documented for several racial, ethnic, and gender groups. In peripheral arterial disease, differences in prevalence, treatment selection, treatment outcomes, and resulting quality of life have negative effects on some minority groups and women. It may be easy to document disparities, but it is harder to understand their underlying causes. Are there biologic differences between members of racial and ethnic groups that influence disease presentation and outcomes? Or is the socioeconomic environment that surrounds them the true driver of observed differences? This article reviews the evidence for racial and gender disparities in vascular surgery and presents some potential mechanisms that may explain the disparities.

Adaptive changes in autogenous vein grafts for arterial reconstruction: clinical implications

For patients with the most severe manifestations of lower extremity arterial occlusive disease, bypass surgery using autogenous vein has been the most durable reconstruction. However, the incidence of bypass graft stenosis and graft failure remains substantial and wholesale improvements in patency are lacking. One potential explanation is that stenosis arises not only from over exuberant intimal hyperplasia, but also due to insufficient adaptation or remodeling of the vein to the arterial environment. Although in vivo human studies are difficult to conduct, recent advances in imaging technology have made possible a more comprehensive structural examination of vein bypass maturation. This review summarizes recent translational efforts to understand the structural and functional properties of human vein grafts and places it within the context of the rich existing literature of vein graft failure.

Disparity in outcomes of surgical revascularization for limb salvage: race and gender are synergistic determinants of vein graft failure and limb loss

BACKGROUND

Vein bypass surgery is an effective therapy for atherosclerotic occlusive disease in the coronary and peripheral circulations; however, long-term results are limited by progressive attrition of graft patency. Failure of vein bypass grafts in patients with critical limb ischemia results in morbidity, limb loss, and additional resource use. Although technical factors are known to be critical to the success of surgical revascularization, patient-specific risk factors are not well defined. In particular, the relationship of race/ethnicity and gender to the outcomes of peripheral bypass surgery has been controversial.

METHODS AND RESULTS

We analyzed the Project of Ex Vivo Vein Graft Engineering via Transfection III (PREVENT III) randomized trial database, which included 1404 lower extremity vein graft operations performed exclusively for critical limb ischemia at 83 North American centers. Trial design included intensive ultrasound surveillance of the bypass graft and clinical follow-up to 1 year. Multivariable modeling (Cox proportional hazards and propensity score) was used to examine the relationships of demographic variables to clinical end points, including perioperative (30-day) events and 1-year outcomes (vein graft patency, limb salvage, and patient survival). Final propensity score models adjusted for 16 covariates (including type of institution, technical factors, selected comorbidities, and adjunctive medications) to examine the associations between race, gender, and outcomes. Among the 249 black patients enrolled in PREVENT III, 118 were women and 131 were men. Black men were at increased risk for early graft failure (hazard ratio [HR], 2.832 for 30-day failure; 95% confidence interval [CI], 1.393 to 5.759; P=0.0004), even when the analysis was restricted to exclude high-risk venous conduits. Black patients experienced reduced secondary patency (HR, 1.49; 95% CI, 1.08 to 2.06; P=0.016) and limb salvage (HR, 2.02; 95% CI, 1.27 to 3.20; P=0.003) at 1 year. Propensity score models demonstrate that black women were the most disadvantaged, with an increased risk for loss of graft patency (HR, 2.02 for secondary patency; 95% CI, 1.27 to 3.20; P=0.003) and major amputation (HR, 2.38; 95% CI, 1.18 to 4.83; P=0.016) at 1 year. Perioperative mortality and 1-year mortality were similar across race/gender groups.

CONCLUSIONS

Black race and female gender are risk factors for adverse outcomes after vein bypass surgery for limb salvage. Graft failure and limb loss are more common events in black patients, with black women being a particularly high-risk group. These data suggest the possibility of an altered biological response to vein grafting in this population; however, further studies are needed to determine the mechanisms underlying these observed disparities in outcome.

Aminaftone, a derivative of 4-aminobenzoic acid, downregulates endothelin-1 production in ECV304 Cells: an in vitro Study

BACKGROUND AND OBJECTIVE

Endothelin-1 (ET-1) plays a central role in the pathogenesis of several vascular diseases. Aminaftone is a drug used for the treatment of capillary disorders but which has a mechanism of action that is not fully understood. We investigated whether aminaftone may exert its effect by interfering with the production of ET-1.

METHODS

Human ECV304 endothelial cells were incubated with interleukin-1beta (IL-1beta) 100 IU/mL with or without the addition of increasing concentrations of aminaftone (2, 4 or 6 microg/mL). ET-1 concentrations in surnatants were quantified by enzyme immunoassay kit at 3, 6 and 12 hours. Pre-pro-endothelin-1 (PPET-1) gene expressions were also analysed by real-time polymerase chain reaction (RT-PCR) at the same time points. Endothelin-converting enzyme (ECE) activity was also determined.

RESULTS

Incubation with IL-1beta increased concentrations of ET-1 and PPET-1 relative gene expression. Incubation with aminaftone significantly reduced production of ET-1 in a concentration-dependent manner. A strong direct correlation was found between ET-1 concentrations and PPET-1 relative gene expression, but aminaftone did not influence ECE activity.

CONCLUSION

Aminaftone inhibits ET-1 production in cell cultures by interfering with transcription of the PPET-1 gene. These findings may account for the clinical efficacy of aminaftone in the treatment of capillary disorders and may encourage conduct of further clinical trials.

Expression of human endothelin-converting enzyme isoforms: role of angiotensin II

A key step in endothelin-1 (ET-1) synthesis is the proteolytic cleavage of big ET-1 by the endothelin-converting enzyme-1 (ECE-1). Four alternatively spliced isoforms, ECE-1a to ECE-1d, have been discovered; however, regulation of the expression of specific ECE-1 isoforms is not well understood. Therefore, we stimulated primary human umbilical vein endothelial cells (HUVECs) with angiotensin II (Ang II). Furthermore, expression of ECE-1 isoforms was determined in internal mammary arteries of patients undergoing coronary artery bypass grafting surgery. Patients had received one of 4 therapies: angiotensin-converting enzyme inhibitors (ACE-I), Ang II type 1 receptor blockers (ARB), HMG-CoA reductase inhibitors (statins), and a control group that had received neither ACE-I, ARB (that is, treatment not interfering in the renin-angiotensin system), nor statins. Under control conditions, ECE-1a is the dominant isoform in HUVECs (4.5+/-2.8 amol/microg RNA), followed by ECE-1c (2.7+/-1.0 amol/microg), ECE-1d (0.49+/-0.17 amol/microg), and ECE-1b (0.17+/-0.04 amol/microg). Stimulation with Ang II did not change the ECE-1 expression pattern or the ET-1 release. We found that ECE-1 mRNA expression was higher in patients treated with statins than in patients treated with ARB therapy (5.8+/-0.76 RU versus 3.0+/-0.4 RU), mainly attributed to ECE-1a. In addition, ECE-1a mRNA expression was higher in patients receiving ACE-I therapy than in patients receiving ARB therapy (1.68+/-0.27 RU versus 0.83+/-0.07 RU). We conclude that ECE-1a is the major ECE-1 isoform in primary human endothelial cells. Its expression in internal mammary arteries can be regulated by statin therapy and differs between patients with ACE-I and ARB therapy.

Interethnic differences at the thermometric response to cold test: functional disorders of blood circulation in hand fingers and exposure to hand–arm vibration

OBJECTIVES

To report some notable aspects regarding thermometric response to cold test in black African subjects compared with Caucasians: both groups comprised persons exposed to hand-arm vibration and controls.

METHODS

An overall sample of 48 workers was examined in order to study their blood circulation in hand fingers: a control group of 12 healthy Caucasian workers never exposed before to hand-arm vibration; 12 Caucasian workers exposed for several years to vibrating tools and affected by occupational Raynaud's phenomenon; 12 healthy black African workers exposed to hand-arm vibration for almost 3 years; and 12 healthy black African workers never exposed to hand-arm vibration. Computerized skin thermometry was performed and thermometric curves were analyzed according to thermometric interpretation criteria such as the area-over-curve (AOC), the fifth minute of recovery/baseline temperature ratio (5REC/BT) and the temperature at the tenth minute of recovery (10REC) after cold test.

RESULTS

Thermometric parameters in Caucasian subjects confirmed the basis of the existing literature in controls (basal finger temperature higher than 32 degrees C and complete recovery to the initial temperature after the cold test) and also in patients with Raynaud's phenomenon (basal temperature often lower than control subjects and slow recovery of finger temperature after cold test). Statistically significant difference was found between healthy Caucasians and healthy black subjects in all the parameters tested: healthy black subjects showed values of AOC and 10REC suggesting almost constantly lower finger temperatures during the thermometry test. Black people, both exposed and non-exposed to hand-arm vibration showed thermometric parameters suggesting poor blood microcirculation, which seems even poorer than in Caucasian people complaining Raynaud's phenomenon.

CONCLUSIONS

Our chronothermometric tests suggest some significant interethnic differences in peripheral microcirculation, which seems rather poor in black African subjects in comparison with Caucasians.

Fixed combination isosorbide dinitrate–hydralazine for nitric-oxide-enhancing therapy in heart failure

The major advances in our understanding and management of heart failure (HF) in recent decades have not fully benefited all segments of our population. HF still represents a growing epidemic, especially for African-Americans, in whom the burden of HF is even greater. The recently reported beneficial effects of the fixed combination of isosorbide dinitrate and hydralazine (ISDN+HYD) in the African-American Heart Failure Trial (A-HeFT), has led to both the FDA approval of this agent and its endorsement by the latest HF guidelines. The properties of ISDN+HYD are well known as its components are mature agents, readily available in generic formulations that have been used for decades in other indications. However, fixed-dose ISDN+HYD represents the first drug to undergo targeted clinical development and to be approved for use in a specific ethnic group. As such, A-HeFT and the approval of ISDN+HYD represent landmark events that merit further scrutiny.

Racial disparities in outcomes following coronary artery bypass grafting

More than 12 million people in the United States have coronary heart disease, the second leading cause of hospitalization in the United States. It is known that persons within racial minorities, specifically African Americans, have a higher prevalence of coronary heart disease, yet are much less likely to undergo invasive cardiac treatment interventions. An invasive intervention commonly used to treat coronary heart disease is coronary artery bypass grafting, with over 140,000 operations performed annually in the United States. However, blacks are known to experience higher post-coronary artery bypass graft morbidity and mortality. The causes for racial disparities in post-coronary artery bypass graft outcomes are not well known but may include factors related to the individual, provider, system, and society/environment, either alone or in combination. The purpose of this article is to provide an overview of the literature regarding disparities in the health and healthcare of black patients with coronary heart disease with respect to CABG, and examine potential hypotheses for variant outcomes after surgery.

Vascular endothelin in hypertension

Endothelins are powerful vasoconstrictor peptides that also play numerous other functions in many different organs. Endothelin-1 (ET-1) is the most abundant and important of this family of peptides in blood vessels. Production of ET-1 is increased in the endothelium and the kidney in salt-dependent models of hypertension (e.g.: DOCA-salt rats and Dahl salt-sensitive rats, in salt-loaded SHR-SP, in angiotensin II-infused and in diabetic rats). ET-1 elicits an inflammatory response by increasing oxidant stress in the vascular wall, which induces vascular remodeling and endothelial dysfunction found in the hypertensive models that exhibit an endothelin-mediated component. Endothelin receptor antagonism reduces blood pressure and vascular hypertrophic remodeling present in these hypertensive models. Patients with stage 2 hypertension have enhanced vascular expression of ET-1. Endothelin receptor antagonists lower blood pressure in hypertensive patients. They could become therapeutic agents for prevention of target organ damage in hypertension and in type 2 diabetes, chronic renal failure and congestive heart failure. Side effects of endothelin receptor blockers have prevented up to the present their development for these indications. New endothelin antagonists devoid of these side effects, or alternatively inhibitors of the endothelin converting enzymes that generate ET-1 may in the future become available to block the endothelin system. However, to date endothelin antagonists have been approved only for the treatment of primary pulmonary hypertension, a rapidly fatal condition in which the endothelin system plays an important role and endothelin antagonists exert favorable effects.

Etiology and management of hypertension in chronic kidney disease

The kidneys are vital in the pathogenesis of hypertension and are also pathologically affected by the presence of hypertension. The prevalence of hypertension in chronic kidney disease (CKD) depends on age, the severity of renal failure, and proteinuria. The intricate and inextricable relationship between CKD and hypertension seems to cause cardiovascular disease that has assumed epidemic proportions. This article discusses the etiology and treatment of hypertension in CKD so that it can be better controlled.

Ethnic differences in the vasoconstrictor activity of endogenous endothelin-1 in hypertensive patients

BACKGROUND

The pathogenesis of essential hypertension in blacks may differ from that in whites. In particular, black patients usually present with a salt-sensitive, low-renin form, which in animal models is associated with enhanced activity of endothelin-1 (ET-1). This study aimed to assess whether ethnic differences exist in the vascular activity of ET-1 in normotensive and hypertensive blacks and whites.

METHODS AND RESULTS

Forearm blood flow (FBF) responses to intraarterial infusion of an ET(A) receptor blocker (BQ-123) were analyzed by plethysmography in 37 normotensive patients and 27 hypertensive patients according to race. BQ-123 did not affect FBF in normotensive subjects (P=0.30), whereas it produced significant vasodilation in hypertensive subjects (P<0.001). In normotensives, FBF response to BQ-123 was similar in white (n =22) and black (n =15) patients (P=0.85). In contrast, in hypertensive patients, the vasodilator effect of ET(A) receptor blockade was significantly higher in blacks (n =13) than in whites (n =14) (P=0.01). To rule out differences in smooth muscle reactivity, the effects of race on FBF responses to exogenous ET-1 were analyzed in the hypertensive subgroups. Endothelin-1 induced a significant vasoconstriction in both white (n =7) and black patients (n =5) (both P<0.001), without differences between them (P=0.46). In 8 black hypertensives, the response to selective ET(A) blockade was not modified by nonselective blockade of ET-1 receptors by co-infusion of BQ-123 and BQ-788 (P=0.66).

CONCLUSIONS

Hypertensive blacks have enhanced ET(A)-dependent vasoconstrictor tone, probably related to increased production of ET-1. Given the negative vascular effects of ET-1, this abnormality may contribute to the pathogenesis of hypertension and its complications in black patients.

Regulation of the major isoform of human endothelin-converting enzyme-1 by a strong housekeeping promoter modulated by polymorphic microsatellites

BACKGROUND

Human endothelin-converting enzyme (ECE)-1, the key enzyme in endothelin biosynthesis, shows broad cell and tissue expression within the cardiovascular system. Expression of ECE-1c, which represents the major ECE-1 isoform, is directed by an alternative promoter, but the mechanisms of ECE-1c promoter regulation are largely unknown. As ECE-1c transcription is initiated from several start sites, we hypothesized that the ECE-1c promoter functions as a housekeeping promoter.

OBJECTIVE

To investigate the putative housekeeping function of the ECE-1c promoter in vascular endothelial cells, which represent a main site of its expression.

RESULTS

Using promoter reporter assays, gel shift and supershift assays, we have demonstrated, in human endothelial EA.hy926 cells, functionality of cis-acting elements for binding of the CAAT-box binding protein NF-YB, GATA-2) E2F-2, and a GC-box binding factor, which are spatially associated with transcriptional start sites of ECE-1c. In the more upstream promoter region we have identified three highly polymorphic dinucleotide repeats, 5'-(CA)n, (CG)n and 3'-(CA)n, which strongly affected promoter function in endothelial EA.hy926 cells (2.7-fold activation comparing the most active to the least active allele) and, in a similar manner, in human neuronal KELLY cells. Finally, by in-vitro methylation, we were able to achieve strong suppression of the ECE-1c promoter activity in endothelial cells.

CONCLUSION

Our results provide a molecular explanation for constitutive expression of ECE-1c mRNA. Modulation by genetic and epigenetic mechanisms as revealed in our study may account for interindividual variation of the constitutive endothelin system activity in humans and thus influence individual predisposition to cardiovascular disease.

Unique endothelin receptor binding in kidneys of ETB receptor deficient rats

Gariepy and colleagues (Gariepy CE, Williams SC, Richardson JA, Hammer RE, and Yanagisawa M. J Clin Invest 102: 1092-1101, 1998.) developed rescued spotting-lethal rats that carry a naturally occurring deletion of the endothelin (ET) type B receptor gene resulting in a lack of functional renal ETB receptor expression. It has been shown that rats homozygous (sl/sl) for the deletion have elevated plasma ET-1 levels; thus, the purpose of this study was to determine whether this deletion would result in a downregulation of ETA receptors in renal tissue. ET-1 and ET-3 binding experiments were performed with cortex, outer medullary, and inner medullary membranes of heterozygous (sl/+) and sl/sl ETB receptor-deficient rats. 125I-labeled ET-1 binding in sl/sl cortex and outer medulla was significantly lower than cortex and outer medulla from sl/+ rats. In contrast to sl/+ rats, [125I]ET-3 binding was not detected in the cortex and outer medulla of sl/sl rats, indicating a lack of ETB receptor expression. The inner medulla of sl/+ rats also demonstrated an abundance of ETB receptors. Surprisingly, however, we also observed significant [125I]ET-3 binding in the sl/sl inner medulla. Furthermore, ET-3 binding in the inner medulla could be blocked with an ETA receptor antagonist in sl/sl rats but not in tissue from sl/+ rats. These studies indicate that rats deficient in ETB receptors have decreased renal cortical and outer medullary ETA receptor number, most likely in response to elevated plasma ET-1 levels. In addition, homozygous ETB-deficient rats express a novel inner medullary ET-3 binding site.