Threshold concentrations of endothelin-1 potentiate contractions to norepinephrine and serotonin in human arteries. A new mechanism of vasospasm?

Bioengineered vascular grafts with a pathogenic TGFBR1 variant model aneurysm formation in vivo and reveal underlying collagen defects

Thoracic aortic aneurysm (TAA) is a life-threatening vascular disease frequently associated with underlying genetic causes. An inadequate understanding of human TAA pathogenesis highlights the need for better disease models. Here, we established a functional human TAA model in an animal host by combining human induced pluripotent stem cells (hiPSCs), bioengineered vascular grafts (BVGs), and gene editing. We generated BVGs from isogenic control hiPSC-derived vascular smooth muscle cells (SMCs) and mutant SMCs gene-edited to carry a Loeys-Dietz syndrome (LDS)-associated pathogenic variant (TGFBR1A230T). We also generated hiPSC-derived BVGs using cells from a patient with LDS (PatientA230T/+) and using genetically corrected cells (Patient+/+). Control and experimental BVGs were then implanted into the common carotid arteries of nude rats. The TGFBR1A230T variant led to impaired mechanical properties of BVGs, resulting in lower burst pressure and suture retention strength. BVGs carrying the variant dilated over time in vivo, resembling human TAA formation. Spatial transcriptomics profiling revealed defective expression of extracellular matrix (ECM) formation genes in PatientA230T/+ BVGs compared with Patient+/+ BVGs. Histological analysis and protein assays validated quantitative and qualitative ECM defects in PatientA230T/+ BVGs and patient tissue, including decreased collagen hydroxylation. SMC organization was also impaired in PatientA230T/+ BVGs as confirmed by vascular contraction testing. Silencing of collagen-modifying enzymes with small interfering RNAs reduced collagen proline hydroxylation in SMC-derived tissue constructs. These studies demonstrated the utility of BVGs to model human TAA formation in an animal host and highlighted the role of reduced collagen modifying enzyme activity in human TAA formation.

Association of plasma endothelin-1 with blood pressure progression among Blacks: The Jackson Heart Study

BACKGROUND

Despite pathophysiological links between endothelin (ET)-1 and hypertension in Black adults, there is no population-based data appraising the association of plasma ET-1 with longitudinal blood pressure (BP) changes in Blacks.

METHODS

We analyzed data from 1197 Jackson Heart Study participants without hypertension (mean age 47.8 years [SD: 12.0]; 64.2% women), with plasma ET-1 available at the baseline examination (2000-2004). Poisson regression with robust variance was used to generate risk ratios (RRs) and 95% confidence intervals (CIs) of BP progression (an increase by ≥1 BP category based on the 2017 American College of Cardiology/American Heart Association classification) and incident hypertension (BP ≥ 130/80 mm Hg or use of antihypertensive medication) at follow-up (2005-2008 or 2009-2013).

RESULTS

Over a median follow-up of 7 years (range: 4-11), 71.2% (n = 854) progressed to a higher BP stage and 64.6% (n = 773) developed hypertension. After adjusting for possible confounders, each unit increment in baseline log (ET-1) was associated with higher risks of BP progression (RR 1.15 [95% CI 1.03-1.29], P = .016) and incident hypertension (RR 1.15 [95% CI 1.01-1.31], P = .032). Compared to those in the lowest ET-1 quartile, participants in the highest quartile had significantly higher risks of BP progression (RR 1.20 [95% CI 1.05-1.37], P = .007) and incident hypertension (RR 1.16 [95% CI 1.00-1.36], P = .052).

CONCLUSIONS

In a large, community-based sample of African Americans, higher plasma ET-1 concentrations were associated with higher risks of BP progression and incident hypertension.

Enzymatic antioxidant system and endothelial function in patients with metabolic syndrome

BACKGROUND

This study examined the relationship between serum glutathione peroxidase 1 (GPx-1) activity and endothelial dysfunction in the subjects with and without metabolic syndrome (MetS).

METHODS

This case-control study was conducted on 76 subjects, 38 were patients with MetS and 38 were without MetS. The demographic, clinical, and laboratory features of the subjects were measured and then compared. The MetS was diagnosed according to the definitions of the National Cholesterol Education Program (NCEP) and International Diabetes Federation (IDF). Serum GPx-1 activity was measured by standard methods. Endothelial dysfunction was assessed with flow-mediated dilation (FMD) technique.

RESULTS

In case-control study of 76 subjects, all of MetS risk factors including abdominal obesity, triglyceride (TG), low serum level of high-density lipoprotein cholesterol (HDL-C), hypertension (HTN), and fasting plasma glucose (FPG) were significantly higher than healthy individuals (P < 0.050). FMD was significantly lower than normal subjects (P < 0.050). Serum GP-1 activity was significantly lower in patients with MetS compared to normal subjects (21.7 ± 13.5 vs. 79.0 ± 38.6, respectively) (P = 0.001). The value of GPx-1 was significantly correlated with diastolic blood pressure (DBP) (r = -0.249, P = 0.040), C-reactive protein (CRP) (r = -0.409, P = 0.014), and FMD (r = 0.293, P = 0.050) in patients with MetS. The results of logistic regression showed that a unite increase in CRP (mg/dl), FMD (%), and endothelin-1 (ET-1) (pg/ml) and a unit decrease in GPx significantly increased the odds ratio (OR) of MetS; after adjusting for age and sex the results remained significant except for FMD (P < 0.050)

CONCLUSION

Endothelial dysfunction is related to serum GPx-1 activity in patients with MetS. GPX-1 activity is associated with risk of cardiovascular diseases (CVDs) and peripheral vascular diseases (PVDs) in patients with MetS.

The Foundational Role of Cardiovascular Imaging in the Characterization of Mental Stress-Induced Myocardial Ischemia in Patients with Coronary Artery Disease

PURPOSE OF REVIEW

Mental stress-provoked myocardial ischemia (MSIMI) is an ischemic phenomenon provoked by the experience of psychologically stressful circumstances. While MSIMI was initially identified 50 years ago during activities of daily living through the use of wearable Holter monitor, subsequent research utilized the technologies of cardiac imaging-ventriculography and myocardial perfusion-under controlled conditions to pursue an understanding of pathophysiology and prognosis. This work revealed that MSIMI occurs in almost half of patients with stable coronary artery disease (CAD) and is associated with cardiac events and early mortality. We provide a focused review of the instrumental role that cardiac imaging has played in elucidating how stress affects cardiac physiology and how emerging diagnostic techniques will allow for further research on stress-mediated changes in the coronary macro- and microvasculature.

RECENT FINDINGS

Observations about the cardiac response to mental stress diverge from underlying cornerstones of the traditional CAD paradigm which is based upon myocardial oxygen demand and the degree of epicardial coronary stenosis. Evidence from studies utilizing non-invasive and invasive studies of coronary perfusion indicates perturbations in the microvascular compartment in response to mental stress. Cardiovascular imaging enjoined with mental stress provocation may be a commanding tool to advance our understanding of non-obstructive CAD and the coronary microvasculature. This further understanding will facilitate incorporation of mental stress testing in the clinical care of patients with discrepant diagnostic work-up of CAD and in patients who experience anginal symptoms due to non-exertional and/or emotional triggers. Such algorithms will be crucial to identify treatment targets to modify the risk associated with mental stress-associated ischemia and adverse prognosis.

Influence of sex on heightened vasoconstrictor mechanisms in the non-Hispanic black population

Cardiovascular disease (CVD) affects individuals of all races and ethnicities; however, its prevalence is highest in non-Hispanic black individuals (BL) relative to other populations. While previous research has provided valuable insight into elevated CVD risk in the BL population, this work has been almost exclusively conducted in men. This is alarming given that BL women suffer from CVD at an equivalent rate to BL men and each has a greater prevalence when compared to all other ethnicities, regardless of sex. The importance of investigating sex differences in mechanisms of cardiovascular function is highlighted by the National Institute of Health requiring sex to be considered as a biological variable in research studies to better our "understanding of key sex influences on health processes and outcomes." The mechanism(s) responsible for the elevated CVD risk in BL women remains unclear and is likely multifactorial. Limited studies in BL women suggest that, while impaired vasodilator capacity is involved, heightened vasoconstrictor tone and/or responsiveness may also contribute. Within this mini-review, we will discuss potential mechanisms of elevated rates of hypertension and other CVDs in BL individuals with a particular focus on young, otherwise healthy, college-aged women. To stimulate academic thought and future research, we will also discuss potential mechanisms for impaired vascular function in BL women, as well as possible divergent mechanisms between BL men and women based on either preliminary data or plausible speculation extending from findings in the existing literature. Last, we will conclude with potential future research directions aimed at better understanding the elevated risk for hypertension and CVD in BL women.

Cardiovascular Imaging of Biology and Emotion: Considerations Toward a New Paradigm

Central activation in response to emotion and cognitive stress induces perturbations in the heart and the peripheral vasculature that differ in physiology and clinical manifestations when compared with exercise-induced changes. While our conventional framework of epicardial coronary artery disease is foundational in cardiology, an expanded paradigm is required to address the cardiovascular response to mental stress (MS) and its associated risks, thus addressing the intersection of the patient's ecological and psychosocial experience with cardiovascular biology. To advance the field of MS in cardiovascular health, certain core challenges must be addressed. These include differences in the trigger activation between exercise and emotion, identification and interpretation of imaging cues as measures of pathophysiologic changes, characterization of the vascular response, and identification of central and peripheral treatment targets. Sex and psychosocial determinants of health are important in understanding the emerging overlap of MS-induced myocardial ischemia with microvascular dysfunction and symptoms in the absence of obstructive disease. In overcoming these critical knowledge gaps, integration of the field of MS will require implementation studies to guide use of MS testing, to support diagnosis of MS induced cardiac and vascular pathophysiology, to assess prognosis, and understand the role of endotying to direct therapy.

Angiotensin II Induces Increased Myocardial Expression of Receptor for Advanced Glycation End Products, Monocyte/Macrophage Infiltration and Circulating Endothelin-1 in Rats With Experimental Diabetes

OBJECTIVES

It is known that the receptor for advanced glycation end products (RAGE) activation is involved in the pathogenesis of cardiovascular disease in diabetes. Previous studies have shown the presence of angiotensin II (Ang II) in diabetes, suggesting a role for this hormone during the disease. However, the association between RAGE and Ang II during pathologic cardiac remodelling after streptozotocin (STZ)-induced diabetes remains unclear. Because Ang II is capable of inducing pro-inflammatory events, blocking its production (enalapril), and its action on its receptor (losartan) could decrease inflammatory events in the myocardium in this experimental model of diabetes. Thus, the aim of this study was to assess the association between RAGE expression, inflammatory events and Ang II in the myocardium during STZ-induced diabetes.

METHODS

Diabetes was induced by intravenous injection of STZ in Sprague-Dawley rats. Myocardial expressions of RAGE, monocyte/macrophage (ED-1-positive cells) infiltration and the intercellular adhesion molecule-1 were determined by histochemical methods. Levels of circulating endothelin-1 (ET-1) were determined by enzyme-linked immunoassay. Effects of Ang II included blocking using losartan (15 mg/kg body weight per day by gastric gavage) or enalapril (18 mg/kg body weight per day by gastric gavage).

RESULTS

Increased expression of both RAGE and ED-1 was seen in the myocardium, but expression of myocardial vascular intercellular adhesion molecule-1 remained unchanged. Circulating levels of ET-1 in STZ rats were increased. Renin‒angiotensin system inhibition decreased expression of myocardial RAGE, ED-1 and ET-1.

CONCLUSIONS

The present findings suggest a role for Ang II in myocardial inflammation in STZ-induced diabetes mediated by RAGE and ET-1.

Pioglitazone Modulates the Vascular Contractility in Hypertension by Interference with ET-1 Pathway

Endothelin-1 (ET-1) is an important modulator of the vascular tone and a proinflammatory molecule that contributes to the vascular damage observed in hypertension. Peroxisome-proliferator activated receptors-γ (PPARγ) agonists show cardioprotective properties by decreasing inflammatory molecules such as COX-2 and reactive oxygen species (ROS), among others. We investigated the possible modulatory effect of PPARγ activation on the vascular effects of ET-1 in hypertension. In spontaneously hypertensive rats (SHR), but not in normotensive rats, ET-1 enhanced phenylephrine-induced contraction through ET_A by a mechanism dependent on activation of TP receptors by COX-2-derived prostacyclin and reduction in NO bioavailability due to enhanced ROS production. In SHR, the PPARγ agonist pioglitazone (2.5 mg/Kg·day, 28 days) reduced the increased ET_A levels and increased those of ET_B. After pioglitazone treatment of SHR, ET-1 through ET_B decreased ROS levels that resulted in increased NO bioavailability and diminished phenylephrine contraction. In vascular smooth muscle cells from SHR, ET-1 increased ROS production through AP-1 and NFκB activation, leading to enhanced COX-2 expression. These effects were blocked by pioglitazone. In summary, in hypertension, pioglitazone shifts the vascular ET_A/ET_B ratio, reduces ROS/COX-2 activation and increases NO availability; these changes explain the effect of ET-1 decreasing phenylephrine-induced contraction.

Racial disparities in cardiovascular disease risk: mechanisms of vascular dysfunction

Cardiovascular disease (CVD) accounts for a third of all deaths in the United States making it the leading cause of morbidity and mortality. Although CVD affects individuals of all races/ethnicities, the prevalence of CVD is highest in non-Hispanic black (BL) individuals relative to other populations. The mechanism(s) responsible for elevated CVD risk in the BL population remains incompletely understood. However, impaired vascular vasodilator capacity and exaggerated vascular vasoconstrictor responsiveness are likely contributing factors, both of which are present even in young, otherwise healthy BL individuals. Within this review, we highlight some historical and recent data, collected from our laboratories, of impaired vascular function, in terms of reduced vasodilator capacity and heightened vasoconstrictor responsiveness, in the peripheral and cerebral circulations in BL individuals. We provide data that such impairments may be related to elevated oxidative stress and subsequent reduction in nitric oxide bioavailability. In addition, divergent mechanisms of impaired vasodilatory capacity between BL men and women are discussed. Finally, we propose several directions where future research is needed to fill in knowledge gaps, which will allow for better understanding of the mechanisms contributing to impaired vascular function in this population. Ultimately, this information will allow for better lifestyle and therapeutic approaches to be implemented in an effort to minimize the increased CVD burden in the BL population.

Relationship between Resistin, Endothelin-1, and Flow-Mediated Dilation in Patient with and without Metabolic Syndrome

Background:

Resistin is peptides that signal the functional status of adipose tissue to the brain and other target organs. It causes insulin resistance and affects the vascular endothelial dysfunction. However, the function and relation between resistin in endothelin-1 (ET-1), which leads to the endothelial dysfunction in humans are enigmatic.

Materials and Methods:

In a cross-sectional study of 76 participants (38 metabolic syndrome patients and 38 healthy participants), biochemical and clinical parameters, including lipid profile, fasting glucose, resistin, ET-1, C-reactive protein (CRP), flow-mediated dilation (FMD), and hypertension were determined and compared between the two groups.

Results:

Multiple linear regression analysis was performed with age- and sex-adjusted plasma resistin levels, FMD, and ET-1 as the dependent variables. Analysis showed that weight, body mass index, triglycerides (TGs), and ET-1 were statistically significant correlated with serum resistin. FMD has negative significantly correlated with weight (r = −0.491, P = 0.001), waist circumference (r = −0.491, P = 0.001), waist-to-hip ratio (r = −0.0444, P = 0.001), and ET-1 (r = −0.075, P = 0.050), but it has significantly correlated with systolic blood pressure (SBP) (r = 0.290, P = 0.016), diastolic blood pressure (DBP) (r = 0.275, P = 0.023), and high-density lipoprotein cholesterol (HDL-C) (r = −0.266, P = 0.050), and ET-1, but it has significantly correlated with SBP, DBP, and HDL-C. ET-1 is significantly correlated with TGs (r = −0.436, P = 0.006), total cholesterol (r = 0.452, P = 0.004), low-density lipoprotein cholesterol (r = 0.454, r = 0.004), and resistin (r = 0.282, P = 0.050), whereas it has negative significantly correlated with HDL-C (r = 0.346, P = 0.034), FMD (r = −0.075, P = 0.050.

Conclusion:

In this study, results shown plasma ET-1 and resistin are suggested as risk factors for the development of endothelial dysfunction and with further study, it is possible that can diagnose the risk of diabetes and cardiovascular disease in the early stages.

Characterisation of preproendothelin-1 derived peptides identifies Endothelin-Like Domain Peptide as a modulator of Endothelin-1

Endothelin-1 (ET-1) is involved in the pathogenesis of cardiac and renal diseases, and in the progression of tumour growth in cancer, but current diagnosis and treatment remain inadequate. Peptides derived from the 212 amino acid precursor preproendothelin-1 (ppET-1) may have utility as biomarkers, or cause biological effects that are unaffected by endothelin receptor antagonists. Here, we used specific immunoassays and LC-MS/MS to identify NT-proET-1 (ppET-1_[18–50]), Endothelin-Like Domain Peptide (ELDP, ppET-1_[93–166]) and CT-proET-1 (ppET-1_[169–212]) in conditioned media from cultured endothelial cells. Synthesis of these peptides correlated with ET-1, and plasma ELDP and CT-proET-1 were elevated in patients with chronic heart failure. Clearance rates of NT-proET-1, ELDP and CT-proET-1 were determined after i.v. injection in anaesthetised rats. CT-proET-1 had the slowest systemic clearance, hence providing a biological basis for it being a better biomarker of ET-1 synthesis. ELDP contains the evolutionary conserved endothelin-like domain sequence, which potentially confers biological activity. On isolated arteries ELDP lacked direct vasoconstrictor effects. However, it enhanced ET-1 vasoconstriction and prolonged the increase in blood pressure in anaesthetised rats. ELDP may therefore contribute to disease pathogenesis by augmenting ET-1 responses.

Endothelial overexpression of endothelin-1 modulates aortic, carotid, iliac and renal arterial responses in obese mice

Endothelin-1 (ET-1) is essential for mammalian development and life, but it has also been implicated in increased cardiovascular risk under pathophysiological conditions. The aim of this study was to determine the impact of endothelial overexpression of the prepro-endothelin-1 gene on endothelium-dependent and endothelium-independent responses in the conduit and renal arteries of lean and obese mice. Obesity was induced by high-fat-diet (HFD) consumption in mice with Tie-1 promoter-driven, endothelium-specific overexpression of the prepro-endothelin-1 gene (TET^het) and in wild-type (WT) littermates on a C57BL/6N background. Isometric tension was measured in rings (with endothelium) of the aorta (A), carotid (CA) and iliac (IA) arteries as well as the main (MRA) and segmental renal (SRA) arteries; all experiments were conducted in the absence or presence of L-NAME and/or the COX inhibitor meclofenamate. The release of prostacyclin and thromboxane A2 was measured by ELISA. In the MRA, TET^het per se increased contractions to endothelin-1, but the response was decreased in SRA in response to serotonin; there were also improved relaxations to acetylcholine but not insulin in the SRA in the presence of L-NAME. HFD per se augmented the contractions to endothelin-1 (MRA) and to the thromboxane prostanoid (TP) receptor agonist U46619 (CA, MRA) as well as facilitated relaxations to isoproterenol (A). The combination of HFD and TET^het overexpression increased the contractions of MRA and SRA to vasoconstrictors but not in the presence of meclofenamate; this combination also augmented further relaxations to isoproterenol in the A. Contractions to endothelin-1 in the IA were prevented by endothelin-A receptor antagonist BQ-123 but only attenuated in obese mice by BQ-788. The COX-1 inhibitor FR122047 abolished the contractions of CA to acetylcholine. The release of prostacyclin during the latter condition was augmented in samples from obese TET^het mice and abolished by FR122047. These findings suggest that endothelial TET^het overexpression in lean animals has minimal effects on vascular responsiveness. However, if comorbid with obesity, endothelin-1-modulated, prostanoid-mediated renal arterial dysfunction becomes apparent.

Body Mass Index and Risk for Mental Stress Induced Ischemia in Coronary Artery Disease

Acute emotionally reactive mental stress (MS) can provoke prognostically relevant deficits in cardiac function and myocardial perfusion, and chronic inflammation increases risk for this ischemic phenomenon. We have described parasympathetic withdrawal and generation of inflammatory factors in MS. Adiposity is also associated with elevated markers of chronic inflammation. High body mass index (BMI) is frequently used as a surrogate for assessment of excess adiposity, and associated with traditional CAD risk factors, and CAD mortality. BMI is also associated with autonomic dysregulation, adipose tissue derived proinflammatory cytokines, which are also attendant to emotion provoked myocardial ischemia. Thus, we sought to determine if body mass index (BMI) contributes to risk of developing myocardial ischemia provoked by mental stress. We performed a prospective interventional study in a cohort of 161 patients with stable CAD. They completed an assessment of myocardial blood flow with single photon emission computed tomography (SPECT) simultaneously during 2 conditions: laboratory mental stress and at rest. Multivariate logistic regression determined the independent contribution of BMI to the occurrence of mental-stress induced ischemia. Mean age was 65.6 ±9.0 years; 87.0% had a history of hypertension, and 28.6% had diabetes. Mean BMI was 30.4 ± 4.7. Prevalence of mental stress ischemia was 39.8%. BMI was an independent predictor of mental stress ischemia, OR=1.10, 95% CI [1.01-1.18] for one-point increase in BMI and OR=1.53, 95% CI [1.06-2.21] for a 4.7 point increase in BMI (one standard deviation beyond the cohort BMI mean), p=0.025 for all. These data suggest that BMI may serve as an independent risk marker for mental stress ischemia. The factors attendant with greater BMI, which include autonomic dysregulation and inflammation, may represent pathways by which high BMI contribute to this risk and serve as a conceptual construct to replicate these findings in larger CAD populations.

Whole body vibration at different exposure frequencies: infrared thermography and physiological effects

The aim of this study was to investigate the effects of whole body vibration (WBV) on physiological parameters, cutaneous temperature, tactile sensitivity, and balance. Twenty-four healthy adults (25.3 ± 2.6 years) participated in four WBV sessions. They spent 15 minutes on a vibration platform in the vertical mode at four different frequencies (31, 35, 40, and 44 Hz) with 1 mm of amplitude. All variables were measured before and after WBV exposure. Pressure sensation in five anatomical regions and both feet was determined using Von Frey monofilaments. Postural sway was measured using a force plate. Cutaneous temperature was obtained with an infrared camera. WBV influences the discharge of the skin touch-pressure receptors, decreasing sensitivity at all measured frequencies and foot regions (P ≤ 0.05). Regarding balance, no differences were found after 20 minutes of WBV at frequencies of 31 and 35 Hz. At 40 and 44 Hz, participants showed higher anterior-posterior center of pressure (COP) velocity and length. The cutaneous temperature of the lower limbs decreased during and 10 minutes after WBV. WBV decreases touch-pressure sensitivity at all measured frequencies 10 min after exposure. This may be related to the impaired balance at higher frequencies since these variables have a role in maintaining postural stability. Vasoconstriction might explain the decreased lower limb temperature.

Higher circulatory level of endothelin-1 in hypertensive subjects screened through a cross-sectional study of rural Bangladeshi women

Endothelin-1 (ET-1) is a potential marker of the endothelial dysfunction, which has been shown to be elevated in hypertensive subjects. No previous study has investigated the circulatory level of ET-1 and hypertension in a South Asian country. The present study assessed the circulating levels of ET-1 in subjects with or without hypertension and further examined the association of ET-1 with clinical and metabolic parameters. A total of 2543 rural Bangladeshi women with a mean age of 44.5 years were studied using a cross-sectional survey. Multiple regressions were used to examine the association between the circulatory ET-1 levels and hypertension. The prevalence of hypertension was 29.3%. The ET-1 levels were significantly higher in the hypertensive (mean 3.08 pg ml(-1), s.e. (0.19)) than in the non-hypertensive subjects (mean 2.01 pg ml(-1), s.e. (0.03)) (P = 0.001). After adjusting for age, the ET-1 level had significant positive associations with the diastolic blood pressure (P = 0.002), systolic blood pressure (P = 0.001), mean arterial pressure (P = 0.002) and fasting blood glucose (P = 0.002). In a tertile analysis, we found that hypertension in the subjects was significantly increased as the levels of ET-1 increased (P for the trend = 0.001). In a stepwise multiple regression analysis, after adjusting for age and all other potential variables, we found that the mean arterial pressure and the fasting plasma levels have significant associations with the ET-1 level. The present study demonstrates that there is a higher concentration of ET-1 among the hypertensive subjects in an apparently healthy population of Bangladeshi rural women. The relationship between ET-1 and hypertension requires further investigation to define the clinical utility and predictive value of serum ET-1 levels for hypertension for a South Asian population.

Severe depressive symptoms are associated with elevated endothelin-1 in younger patients with acute coronary syndrome

OBJECTIVE

To explore the relationship of depressive symptom severity to circulating endothelin (ET)-1 in younger patients with acute coronary syndrome (ACS). Younger patients report greater depressive symptom severity, which predicts poorer post-ACS prognosis. The pathways linking depression to post-ACS prognosis require further elucidation. ET-1 is a potent endogenous vasoconstrictor which has been previously linked to adverse post-ACS outcomes.

METHODS

The sample (n=153) included males ≤ 50 years of age and females ≤ 55 years of age who participated in a larger study. Blood samples for ET-1 assessment were collected within 2-3h of ACS admission. Depressive symptoms were assessed with the Beck Depression Inventory (BDI) II within 2-5 days of admission. ET-1 was treated as a transformed continuous variable (ET-1T). BDI-II scores were classified into four categories using conventional thresholds demarcating mild, moderate, and severe levels of depressive symptoms. The relationship of classified BDI-II score to ET-1T was examined in simple and multivariable linear regression models.

RESULTS

Classified BDI-II score was related to ET-1T in both unadjusted (χ(2)=9.469, p=0.024) and multivariable (χ(2)=8.430, p=0.038) models, with ET-1T being significantly higher in patients with severe depressive symptoms than in those with mild and moderate depressive symptoms.

CONCLUSIONS

In this sample of younger post-ACS patients, severe depressive symptoms were associated with elevated ET-1. We acknowledge that the observed association could be eliminated by the inclusion of some unmeasured variable(s). Longitudinal research should examine whether ET-1 mediates the relationship of depressive symptoms to long-term post-ACS outcomes.

Confluence of depression and acute psychological stress among patients with stable coronary heart disease: effects on myocardial perfusion

Background

Depression is prevalent in coronary heart disease (CHD) patients and increases risk for acute coronary syndrome (ACS) recurrence and mortality despite optimal medical care. The pathways underlying this risk remain elusive. Psychological stress (PS) can provoke impairment in myocardial perfusion and trigger ACS. A confluence of acute PS with depression might reveal coronary vascular mechanisms of risk. We tested whether depression increased risk for impaired myocardial perfusion during acute PS among patients with stable CHD.

Methods and Results

Patients (N=146) completed the Beck Depression Inventory‐I (BDI‐I), a measure of depression linked to recurrent ACS and post‐ACS mortality, and underwent single‐photon emission computed tomography myocardial perfusion imaging at rest and during acute PS. The likelihood of new/worsening impairment in myocardial perfusion from baseline to PS as a function of depression severity was tested. On the BDI‐I, 41 patients scored in the normal range, 48 in the high normal range, and 57 in the depressed range previously linked to CHD prognosis. A BDI‐I score in the depressed range was associated with a significantly greater likelihood of new/worsening impairment in myocardial perfusion from baseline to PS (odds ratio =2.89, 95% CI: 1.26 to 6.63, P=0.012). This remained significant in models controlling ACS recurrence/mortality risk factors and medications. There was no effect for selective serotonin reuptake inhibitor medications.

Conclusions

Depressed patients with CHD are particularly susceptible to impairment in myocardial perfusion during PS. The confluence of PS with depression may contribute to a better understanding of the depression‐associated risk for ACS recurrence and mortality.

The effect of ethnicity on the vascular responses to cold exposure of the extremities

PURPOSE

Cold injuries are more prevalent in individuals of African descent (AFD). Therefore, we investigated the effect of extremity cooling on skin blood flow (SkBF) and temperature (T sk) between ethnic groups.

METHODS

Thirty males [10 Caucasian (CAU), 10 Asian (ASN), 10 AFD] undertook three tests in 30 °C air whilst digit T sk and SkBF were measured: (i) vasomotor threshold (VT) test--arm immersed in 35 °C water progressively cooled to 10 °C and rewarmed to 35 °C to identify vasoconstriction and vasodilatation; (ii) cold-induced vasodilatation (CIVD) test--hand immersed in 8 °C water for 30 min followed by spontaneous warming; (iii) cold sensitivity (CS) test--foot immersed in 15 °C water for 2 min followed by spontaneous warming. Cold sensory thresholds of the forearm and finger were also assessed.

RESULTS

In the VT test, vasoconstriction and vasodilatation occurred at a warmer finger T sk in AFD during cooling [21.2 (4.4) vs. 17.0 (3.1) °C, P = 0.034] and warming [22.0 (7.9) vs. 12.1 (4.1) °C, P = 0.002] compared with CAU. In the CIVD test, average SkBF during immersion was greater in CAU [42 (24) %] than ASN [25 (8) %, P = 0.036] and AFD [24 (13) %, P = 0.023]. Following immersion, SkBF was higher and rewarming faster in CAU [3.2 (0.4) °C min(-1)] compared with AFD [2.5 (0.7) °C min(-1), P = 0.037], but neither group differed from ASN [3.0 (0.6) °C min(-1)]. Responses to the CS test and cold sensory thresholds were similar between groups.

CONCLUSION

AFD experienced a more intense protracted finger vasoconstriction than CAU during hand immersion, whilst ASN experienced an intermediate response. This greater sensitivity to cold may explain why AFD are more susceptible to cold injuries.

The role of endothelin-1 in the sympathetic nervous system in the heart

Endothelin-1 (ET1) is a peptide that was initially identified as a strong inductor of vascular contraction. In the last 25 years, there have been several biological processes identified in which ET1 seems to play a critical role. In particular, genetic studies have unveiled that ET1 is important for neuronal development, growth and function. Experimental studies identified ET1 as a regulator of the interaction between sympathetic neurons and cardiac myocytes. This might be of clinical importance since patients suffering from heart failure are characterized by disrupted norepinephrine homeostasis in the heart. This review summarizes the important findings on the role of ET1 for sympathetic neurons and norepinephrine homeostasis in the heart.

Molecular interactions of serotonin (5-HT) and endothelin-1 in vascular smooth muscle cells: in vitro and ex vivo analyses

Elevated levels of serotonin (5-HT) and endothelin-1 (ET-1) may be involved in cardiovascular complications of diabetes mellitus. Data suggest supraphysiological concentrations of 5-HT (10(-6) M) potentiate the ability of ET-1 to stimulate DNA synthesis and vascular smooth muscle cell (VSMC) proliferation in vitro via activation of mitogen-activated protein kinase (p42/44 MAPK) and Janus kinase 2 (JAK2) pathways. Additionally, 5-HT enhances agonist-induced contractions via p42/44 MAPK and an unknown tyrosine kinase. However, the exact mechanisms of the 5-HT/ET-1 interactions and whether these effects occur at physiological levels (10(-9) M) are unknown. Therefore, we hypothesized that interactions between 5-HT and ET-1 at physiological concentrations in VSMC enhanced activation of both p42/44 MAPK and JAK2 pathways contributing to vascular growth and contractile responses. With the use of rat VSMC and Western blot analysis, our data suggest no effect of acute (30 min) preincubation with 5-HT (10(-9) M) and/or ET-1 (10(-9) M) on the activation of either pathway in normal or high glucose conditions. To determine if there was altered vascular reactivity in intact vessels we tested the effects of 5-HT and ET-1 interaction using myographs to measure isometric contractions of rat thoracic aortic rings. 5-HT (10(-9) M) and ET-1 (10(-12) M) stimulate enhanced contractile responses to each other that were inhibited by JAK2 and p42/44 MAPK antagonists. Our findings demonstrate that both 5-HT and ET-1 at physiological concentrations could interact with each other and activate p42/44 MAPK and JAK2 signaling pathways to cause an increase in smooth muscle contraction that could lead to altered vascular function.

Obesity and heterozygous endothelial overexpression of prepro-endothelin-1 modulate responsiveness of mouse main and segmental renal arteries to vasoconstrictor agents

AIMS

Levels of the endothelium-derived peptide endothelin-1 (ET-1) are elevated in obese humans, and ET-1 mediated vascular tone is increased. Renal arterial smooth muscle is highly responsive to ET-1. Whether or not endothelium-derived ET-1 affects contractions of the renal artery under normal conditions or in obesity is unknown. The present study was designed to investigate whether or not overexpression of endogenous ET-1 in the endothelium affects the responsiveness of the main and segmental renal arteries differently in obesity.

MAIN METHODS

Mice with tie-1 promoter-driven endothelium-restricted heterozygous overexpression of preproendothelin-1 were used (TET(het)). Obesity was induced in TET(het) mice and wild-type (WT) littermates by feeding a high fat diet for 30 weeks; lean controls were kept on standard chow. The renal arteries were studied in wire myographs testing contractions (in the presence of l-NAME) to ET-1, serotonin, and U46619.

KEY FINDINGS

Contractions to ET-1 were comparable between groups in main renal arteries, but augmented in segmental preparations from obese mice. Serotonin-induced responses were enhanced in obese TET(het) mice renal arteries compared to lean controls. Concentration-contraction curves to U46619 were shifted significantly to the left in main renal arteries of obese animals, and the maximal response was significantly increased between lean and obese TET(het) mice.

SIGNIFICANCE

These results indicate an augmented responsiveness of main renal arteries in obesity particularly to TP receptor activation. When combined with endothelial ET-1 overexpression this effect is even more pronounced, which may help to gain further insights into the mechanisms of hypertension in obesity.

Blood pressure regulation II: what happens when one system must serve two masters--oxygen delivery and pressure regulation?

During high-intensity dynamic exercise, O2 delivery to active skeletal muscles is enhanced through marked increases in both cardiac output and skeletal muscle blood flow. When the musculature is vigorously engaged in exercise, the human heart lacks the pumping capacity to meet the blood flow demands of both the skeletal muscles and other organs such as the brain. Vasoconstriction must therefore be induced through activation of sympathetic nervous activity to maintain blood flow to the brain and to produce the added driving pressure needed to increase flow to the skeletal muscles. In this review, we first briefly summarize the local vascular and neural control mechanisms operating during high-intensity exercise. This is followed by a review of the major neural mechanisms regulating blood pressure during high-intensity exercise, focusing mainly on the integrated activities of the arterial baroreflex and muscle metaboreflex. In high cardiac output situations, such as during high-intensity dynamic exercise, small changes in total peripheral resistance can induce large changes in blood pressure, which means that rapid and fine regulation is necessary to avoid unacceptable drops in blood pressure. To accomplish this rapid regulation, arterial baroreflex function may be modulated in various ways through activation of the muscle metaboreflex and/or other neural mechanisms. Moreover, this modulation of the arterial baroreflex may change over the time course of an exercise bout, or to accommodate changes in exercise intensity. Within this model, integration of arterial baroreflex modulation with other neural mechanisms plays an important role in cardiovascular control during high-intensity exercise.

Vascular lesions induced by renal nerve ablation as assessed by optical coherence tomography: pre- and post-procedural comparison with the Simplicity catheter system and the EnligHTN multi-electrode renal denervation catheter

Aims

Catheter-based renal nerve ablation (RNA) using radiofrequency energy is a novel treatment for drug-resistant essential hypertension. However, the local endothelial and vascular injury induced by RNA has not been characterized, although this importantly determines the long-term safety of the procedure. Optical coherence tomography (OCT) enables in vivo visualization of morphologic features with a high resolution of 10–15 µm. The objective of this study was to assess the morphological features of the endothelial and vascular injury induced by RNA using OCT.

Methods and results

In a prospective observational study, 32 renal arteries of patients with treatment-resistant hypertension underwent OCT before and after RNA. All pre- and post-procedural OCT pullbacks were evaluated regarding vascular changes such as vasospasm, oedema (notches), dissection, and thrombus formation. Thirty-two renal arteries were evaluated, in which automatic pullbacks were obtained before and after RNA. Vasospasm was observed more often after RNA then before the procedure (0 vs. 42%, P < 0.001). A significant decrease in mean renal artery diameter after RNA was documented both with the EnligHTN™ (4.69 ± 0.73 vs. 4.21 ± 0.87 mm; P < 0.001) and with the Simplicity® catheter (5.04 ± 0.66 vs. 4.57 ± 0.88 mm; P < 0.001). Endothelial-intimal oedema was noted in 96% of cases after RNA. The presence of thrombus formations was significantly higher after the RNA then before ablation (67 vs. 18%, P < 0.001). There was one evidence of arterial dissection after RNA with the Simplicity® catheter, while endothelial and intimal disruptions were noted in two patients with the EnligHTN™ catheter.

Conclusion

Here we show that diffuse renal artery constriction and local tissue damage at the ablation site with oedema and thrombus formation occur after RNA and that OCT visualizes vascular lesions not apparent on angiography. This suggests that dual antiplatelet therapy may be required during RNA.

Prunellae Spica Extract Contains Antagonists for Human Endothelin Receptors

Endothelin-1 (ET-1) is a powerful vasoconstrictor that contributes to blood pressure elevation. The biological effects of ETs are mediated by two receptors, namely, endothelin type A receptor (ETAR) and endothelin type B receptor (ETBR). Chinese herbal medicines (CHM) with antagonist activity for these two receptors were screened by establishing stable clones of CHO-K1 cells expressing high levels of human ETAR and ETBR, namely CHO-ETAR and CHO-ETBR.The aqueous extract of Prunellae Spica (P1) inhibited the binding of 125I-ET-1 to ETAR and ETBR in CHO-ETAR and CHO-ETBR cells, respectively. P1 suppressed the ET-1-induced mobilization of intracellular Ca2+ . Through the alcohol fractionation of P1, the antagonists of human ETAR and ETBR were found to belong to different, separable ingredients and the antagonist of ETAR is more soluble in alcohol. The two antagonists were also effective in the test on human primary cells, HASMC and HUVEC. P1 successfully prevented the development of ET-1-associated hypertension in rats without further purification. These results indicate the presence of anti-hypertensive ingredients in P. Spica extract, at least through the inactivation of ETAR and/or ETBR.

Exercise pressor response and arterial baroreflex unloading during exercise in chronic kidney disease

Patients with chronic kidney disease (CKD) have poor exercise capacity, which contributes to cardiovascular risk. We sought to determine whether patients with stage 2 or stage 3 CKD have an augmented blood pressure (BP) response during exercise, and if so, whether overactivation of the sympathetic nervous system (SNS) during exercise might play a role. In 13 patients with CKD and hypertension and 13 controls with hypertension, we measured hemodynamics and muscle sympathetic nerve activity (MSNA) during the following maneuvers: low-level rhythmic handgrip (RHG 20%), which primarily stimulates mechanoreceptors, and moderate static handgrip exercise (SHG 30%) followed by posthandgrip circulatory arrest (PHGCA), which isolates metaboreceptors. During baseline studies, patients with CKD had significantly greater increases in mean arterial pressure (MAP) during SHG 30% (P = 0.045), RHG 20% (P = 0.031), and PHGCA (P = 0.043); however, the MSNA response was not augmented in patients with CKD compared with controls. We hypothesized that an augmented SNS response during exercise might be revealed in CKD if arterial baroreflex constraint was equalized using nitroprusside (NTP). These exercise maneuvers were repeated in patients with CKD during NTP infusion to equalize the BP response between groups, thereby relieving baroreflex-mediated suppression of SNS activity. With NTP infusion, patients with CKD had significantly increased MSNA responses during SHG 30% (P = 0.0044), and RHG 20% (P = 0.0064), but not during PHGCA (P > 0.05), suggesting increased reflex activation of the SNS during exercise, which may be mediated by mechanoreceptors but not metaboreceptors. Patients with CKD have an exaggerated BP response during rhythmic and static exercise with underlying SNS overactivation that is revealed during arterial baroreflex unloading during exercise.

Differential effects of Selexipag [corrected] and prostacyclin analogs in rat pulmonary artery

{4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic acid (ACT-333679) is the main metabolite of the selective prostacyclin (PGI(2)) receptor (IP receptor) agonist selexipag. The goal of this study was to determine the influence of IP receptor selectivity on the vasorelaxant efficacy of ACT-333679 and the PGI(2) analog treprostinil in pulmonary artery under conditions associated with pulmonary arterial hypertension (PAH). Selexipag and ACT-333679 evoked full relaxation of pulmonary artery from control and monocrotaline (MCT)-PAH rats, and ACT-333679 relaxed normal pulmonary artery contracted with either endothelin-1 (ET-1) or phenylephrine. In contrast, treprostinil evoked weaker relaxation than ACT-333679 of control pulmonary artery and failed to induce relaxation of pulmonary artery from MCT-PAH rats. Treprostinil did not evoke relaxation of normal pulmonary artery contracted with either ET-1 or phenylephrine. Expression of prostaglandin E(3) (EP(3)) receptor mRNA was increased in pulmonary artery from MCT-PAH rats. In contraction experiments, the selective EP(3) receptor agonist sulprostone evoked significantly greater contraction of pulmonary artery from MCT-PAH rats compared with control rats. The presence of a threshold concentration of ET-1 significantly augmented the contractile response to sulprostone in normal pulmonary artery. ACT-333679 did not evoke direct contraction of rat pulmonary artery, whereas treprostinil evoked concentration-dependent contraction that was inhibited by the EP(3) receptor antagonist (2E)-3-(3',4'-dichlorobiphenyl-2-yl)-N-(2-thienylsulfonyl)acrylamide. Antagonism of EP(3) receptors also revealed a relaxant response to treprostinil in normal pulmonary artery contracted with ET-1. These data demonstrate that the relaxant efficacy of the selective IP receptor agonist selexipag and its metabolite ACT-333679 is not modified under conditions associated with PAH, whereas relaxation to treprostinil may be limited in the presence of mediators of disease.

Autonomic contribution to endothelin-1 increase during laboratory anger-recall stress in patients with coronary artery disease

In coronary artery disease (CAD), endothelin-1 (ET-1) is released by activated macrophages and thereby contributes to coronary plaque rupture and triggered cardiac events. The multifactorial regulation of ET-1 includes stimulated release by cytokines and autonomic factors. Laboratory stress provokes alteration in autonomic tone and prolonged ET-1 mediated endothelial dysfunction. The objective of the study is to determine the autonomic contribution to an increase in ET-1 in response to laboratory stress in patients with CAD. Patients (n = 88) with chronic stable CAD instrumented with hemodynamic monitor, digital electrocardiogram (ECG) monitor and indwelling catheter for blood sampling completed a laboratory protocol that included initial rest (30 min), baseline (BL: 10 min), and anger recall stress (AR: 8 min). Change from BL to AR was determined for (a) parasympathetic activity (by spectral analysis of ECG); (b) sympathetic activity (by circulating catecholamines); and (c) ET-1. AR provoked increases from BL in catecholamines, and a decrease in parasympathetic activity. Multivariate analysis with change in parasympathetic activity and catecholamines, while controlling for age and use of β-blockers, revealed a significant odds ratio (OR = 3.27, 95% CI 1.03, 10.41 P = 0.04) for an increase in ET-1 associated with parasympathetic withdrawal; no other variables were significant. The predominant influence of parasympathetic activity on anger/stress-provoked increase in ET-1 is consistent with the cholinergic antiinflammatory pathway. Future examination of autonomic influences on atherosclerotic leukocytes, endothelial cell function and the dynamics of ET-1 are warranted.

Depression predicts elevated endothelin-1 in patients with coronary artery disease

OBJECTIVE

To examine the relationship of depression severity to circulating endothelin-1 (ET-1), which has previously been linked to plaque rupture and postacute coronary syndrome (ACS) survival. Depression carries an independent two- to four-fold increased risk of early morbidity and mortality after ACS. The pathway(s) linking depression to event-free survival remains to be determined.

METHODS

Patients with documented history of coronary artery disease (n = 101) provided a resting morning blood sample that was assayed for ET-1, and they completed the Beck Depression Inventory (BDI). ET-1 was treated as a log-transformed continuous variable (logET-1), and as a dichotomous variable using a post-ACS risk threshold previously reported (≥1.16 fmol/mL).

RESULTS

BDI score was related to logET-1 in both unadjusted and adjusted models. In addition, unadjusted and adjusted logistic regression models with dichotomous ET-1 revealed that, for each point increase in BDI score, there was approximately a 14% increased likelihood of being at or above ET-1 risk threshold. Secondary logistic regression models demonstrated a >3.5-fold likelihood of being at or above this risk threshold in association with a BDI score of ≥10.

CONCLUSIONS

Depression symptom severity predicts ET-1 elevation that has previously been linked to post-ACS survival, with the greatest risk of elevation among those patients with worse depression symptoms. This link may identify a vulnerability to triggered ACS and poorer survival associated with depression. Future research should establish whether the observed relationship of depressive symptoms to ET-1 level mediates the link between depression and survival.

Tendency to angry rumination predicts stress-provoked endothelin-1 increase in patients with coronary artery disease

OBJECTIVE

To determine whether a tendency to angry rumination predicts anger recall (AR) stress-provoked increase in endothelin (ET)-1 among patients with coronary heart disease (CHD).

METHODS

Patients with chronic stable CHD (n = 105) completed a five-item measure of tendency to angry rumination (DAB-VR) and underwent a laboratory AR stress protocol (15-minute resting baseline [BL], 8-minute AR). Blood samples drawn at end of BL and AR were assayed for ET-1. Change in ET-1 from BL to AR (increase versus decrease/no change) was treated dichotomously in multivariate logistic regression models, including DAB-VR score and potential confounders, to evaluate the contribution of DAB-VR to the prediction of change in ET-1.

RESULTS

In the multivariate model, DAB-VR score significantly predicted ET-1 increase (odds ratio, 1.34; 95% confidence interval, 1.10-1.1.63; p = .004), controlling for age, history of diabetes, hypercholesterolemia, rate pressure product, use of beta blockers, and statins.

CONCLUSIONS

A tendency to angry rumination independently predicted AR stress-provoked ET-1 increase among patients with CHD. Given the involvement of ET-1 in plaque rupture, anger rumination tendency may identify vulnerability to anger-triggered acute coronary syndrome through prolongation of initial anger mobilization. The contribution of ruminative thinking to sustained poststress ET-1 elevation and the synergistic relationship of ET-1 during emotional stress with norepinephrine and nitric oxide remain to be explored.

Heart-brain interactions in mental stress-induced myocardial ischemia

Myocardial ischemia that results from emotional provocation occurs in as many as 30% to 50% of patients with coronary artery disease during the discourse of their lives. This emotionally provoked or mental stress ischemia is associated with poor prognosis, with emerging treatment strategies. This article outlines the conceptual constructs that support the pathophysiologic underpinnings, and biobehavioral aspects associated with this mental stress ischemia. We review a biobehavioral model in which cognitive stress is transduced in the brain. The response of the brain to psychosocial stress is a highly sophisticated and integrated process by which sensory inputs are evaluated and appraised for their importance in relation to previous experience and current goals. The biologic consequences of such stress transduced in the central nervous system has its effect on cardiovascular flow and function through changes in autonomic balance, which result in various biologic processes that culminate in the perturbation of flow and function of the heart.

Effects of endothelin-1 on the relaxation of rat coronary arteries

To analyze the effects of endothelin-1 on the b-adrenergic response of the coronary circulation, 2-mm-long segments of coronary arteries from rats were prepared for isometric tension recording in organ baths. The relaxation to isoproterenol (3 x 10(-8) M), field electrical stimulation (4 Hz, 0.1-millisecond duration, 10 seconds), acetylcholine (3 x 10(-8) M), and sodium nitroprusside (10(-9) M) was recorded in arteries precontracted with U46619 (10(-7) to 5 x 10(-7) M) before and after treatment with endothelin-1 (3 3 10210 and 1029 M). The relaxation to isoproterenol was increased by treatment with endothelin-1 and with the endothelin ET(B) antagonist BQ788 (10(-6) M) but not with the endothelin ET(A) antagonist BQ123 (10(-6) M) or with the blocker of protein kinase C chelerythrine (10(-5) M). In the presence of BQ788, BQ123, or chelerythrine, endothelin-1 did not modify the relaxation to isoproterenol. Treatment with endothelin-1 did not modify the relaxation to electrical stimulation, acetylcholine, or sodium nitroprusside. These results suggest that endothelin-1 may potentiate coronary beta-adrenergic vasodilatation, at least in part due to stimulation of endothelin ET(A) receptors and activation of protein kinase C.

Low-intensity resistance exercise with slow lifting and lowering does not increase noradrenalin and cardiovascular responses

The aim of this study was to investigate the effect of low-intensity resistance exercise with slow lifting and lowering (LSL) on plasma endothelin-1 (ET-1) and noradrenalin concentrations in young healthy adults. Eight healthy males participated in this study (age 19.0 +/- 0.5 years, mean +/- SD). The LSL performed the 10 repetitions with 3 s eccentric (lowering phase) and 3 s concentric (lifting phase) muscle actions. The high-intensity resistance exercise with normal lifting and lowering (HNL) performed the 10 repetitions with 1 s eccentric (lowering phase) and 1 s concentric (lifting phase) muscle actions. The load was set to 40% of one repetition maximal (1RM) for LSL and 80% of 1RM for HNL. Plasma ET-1 and noradrenalin concentrations were measured before and after each type of exercise. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP) and heart rate (HR) during LSL and HNL were measured. The rate-pressure product (RPP) was calculated from SBP and HR. There were no significant differences in the plasma ET-1 concentration between LSL and HNL. However, the plasma noradrenalin concentration was significantly increased after HNL, compared with LSL (P<0.001). SBP, DBP, PP, MAP, HR and RPP during LSL were significantly lower compared with HNL (P<0.05: PP and HR; P<0.01: RPP; P<0.001: SBP, DBP and MAP). These results suggested that LSL may suppress the increase in plasma noradrenalin concentrations and cardiovascular responses.

Vaso-active factors in pregnancy

Pregnancy results in profound physiological changes in the cardiovascular system, yet these changes are completely reversible. It is apparent that vaso-active factors, some as yet probably unidentified, which act as humoral or local autocrine or paracrine regulators of vasular resistance, play a major role in these cardio-vascular changes. This role may be heightened in pregnancy when there has to be a large increase in blood flow to the uterus and placenta while maintaining adequate flow to other vascular beds. Our knowledge of the mechanisms of action of these vaso-active factors and their interactions with each other still remains incomplete. Alterations in synthesis and action of these vaso-active factors may occur in pregnancies associated with pregnancy-induced hypertension, pre-eclampsia or intra-uterine growth retardation. Investigation of such alterations may help to elucidate the roles of vaso-active factors in both normal and pathological situations. The gestational hormones oestrogen and progesterone, are obviously prime candidates as overall regulators of the cardiovascular changes of pregnancy and as agents which alter the synthesis or action of other vaso-active factors. Currently, much attention is being focused on the role of local autocrine or paracrine vaso-active factors which may be produced by the endothelium or by the underlying vascular smooth muscle cells and alterations in their production or action in the hyptertensive disorders of pregnancy. The endothelium forms the largest endocrine organ within the body and so its importance in the mediation of vascular events should not be under-estimated. The principal objective of this review is to examine the roles of these many autocrine and paracrine vaso-active factors during pregnancy and their relation with the overall regulation of the vascular system. Changes which may occur and be involved in the aetiology of pre-eclampsia and growth retardation will also be examined.

An endothelin type A receptor-expressing cell to characterize endothelin-1 binding and screen antagonist

Endothelin-1 (ET-1) induces contraction of vascular smooth muscle through binding to endothelin type A receptor (ET(A)R). COS-7 cells stably expressing high levels of the ET(A)R were established (designated COS-7(ET(A)R)). The COS-7(ET(A)R) cell bound [(125)I]ET-1 with a K(d) of 932+/-161 pM and a B(max) of 74+/-13 fmol/2x10(5) cells. [(125)I]ET-1 binding was inhibited by ET-1 and the ET(A)R antagonist BQ-610, but not by the endothelin type B receptor (ET(B)R) antagonist BQ-788. In clones expressing two ET(A)R mutants containing D46N or R53Q substitutions in the first extracellular domain of the receptor, [(125)I]ET-1 binding activity was dramatically reduced. This suggests that these single amino acid substitutions alter the three-dimensional structure of the ligand-binding domain of the ET(A)R. Using COS-7(ET(A)R) cell, we showed that Ca(2+) or Mg(2+) was essential for ET-1 binding to the ET(A)R and that ET-1 treatment induced postreceptor signaling, that is, intracellular accumulation of cyclic AMP (cAMP) and Ca(2+) mobilization. The COS-7(ET(A)R) established in this study will be a useful tool for screening ET-1 antagonists for treating hypertension.

Endothelin-1 and serotonin are involved in activation of RhoA/Rho kinase signaling in the chronically hypoxic hypertensive rat pulmonary circulation

We have previously reported that vasoconstrictor sensitivity to KCl (a receptor-independent and voltage-gated Ca influx-mediated vasoconstrictor) is augmented in the chronically hypoxic hypertensive rat pulmonary circulation probably through increased Rho kinase-mediated Ca sensitization. However, the upstream mechanism by which the RhoA/Rho kinase signaling pathway is activated is unknown. This study examined if endogenous endothelin-1 (ET-1) and serotonin (5-HT) play roles in the Rho kinase-mediated augmented vasoconstrictor response to KCl and the activation of RhoA in chronically hypoxic hypertensive rat pulmonary arteries. The augmented KCl vasoconstriction in hypertensive lungs was reduced by the ETA receptor antagonist BQ123, while a dual ETA/B antagonist had no further effects. A combination of BQ123 and a 5-HT1B/1D receptor antagonist, GR127935, was more effective than either agent alone. The combined antagonists also reduced augmented contractile sensitivity to KCl in hypertensive intrapulmonary arteries. Membrane-to-cytosol ratio of RhoA expression in hypertensive arteries was greater than that in normotensive arteries and was reduced by BQ123 and GR127935. These results suggest that stimulation of ETA and 5-HT1B/1D receptors by endogenous ET-1 and 5-HT, respectively, is involved in RhoA/Rho kinase-mediated increased Ca sensitization in the chronically hypoxic hypertensive rat pulmonary circulation.

Relationship between plasma endothelin-1 concentration and cardiovascular responses during high-intensity eccentric and concentric exercise

The present study investigates the relationship between plasma endothelin-1 (ET-1) concentrations and cardiovascular responses during eccentric (ECC) and concentric (CON) resistance exercises. Eight healthy males (aged 24.3 +/- 1.2 years) performed dynamic forearm exercises for 60 s at an angular velocity of 60 masculine s(-1). Each test comprised 60-s high-intensity (80% of peak torque) bouts of randomly selected ECC and CON contractions, and the plasma ET-1 concentrations were measured before and after each type of contraction. Systolic pressure (SBP), diastolic pressure (DBP), pulse pressure and heart rate (HR) during ECC and CON contraction were also measured. Mean arterial pressure (MAP) was calculated from SBP and DBP. The rate-pressure product (RPP) was calculated from SBP and HR. The plasma ET-1 concentration was significantly increased after CON, compared with ECC contraction (P<0.01). Moreover, SBP, DBP, MAP and RPP were significantly increased (P<0.05, P<0.01, P<0.001, respectively) during CON, compared with ECC contraction. Correlations between plasma ET-1 concentration and MAP were not significant during ECC contraction, but significantly positive during CON contraction (P<0.05). These results showed that CON contraction is associated with ET-1 production and a greater increase in blood pressure compared with ECC contraction.

Endothelin-1-mediated vasoconstriction at rest and during dynamic exercise in healthy humans

It is now generally accepted that alpha-adrenoreceptor-mediated vasoconstriction is attenuated during exercise, but the efficacy of nonadrenergic vasoconstrictor pathways during exercise remains unclear. Thus, in eight young (23 +/- 1 yr), healthy volunteers, we contrasted changes in leg blood flow (ultrasound Doppler) before and during intra-arterial infusion of the alpha(1)-adrenoreceptor agonist phenylephrine (PE) with that of the nonadrenergic endothelin A (ET(A))/ET(B) receptor agonist ET-1. Heart rate, arterial blood pressure, common femoral artery diameter, and mean blood velocity were measured at rest and during knee-extensor exercise at 20%, 40%, and 60% of maximal work rate (WR(max)). Drug infusion rates were adjusted for blood flow to maintain comparable doses across all subjects and conditions. At rest, PE infusion (8 ng x ml(-1) x min(-1)) provoked a rapid and significant decrease in leg blood flow (-51 +/- 3%) within 2.5 min. Resting ET-1 infusion (40 pg x ml(-1) x min(-1)) significantly decreased leg blood flow within 5 min, reaching a maximal vasoconstriction (-34 +/- 3%) after 25-30 min of continuous infusion. Compared with rest, an exercise intensity-dependent attenuation to PE-mediated vasoconstriction was observed (-18 +/- 5%, -7 +/- 2%, and -1 +/- 3% change in leg blood flow at 20%, 40%, and 60% of WR(max), respectively). Vasoconstriction in response to ET-1 was also blunted in an exercise intensity-dependent manner (-13 +/- 3%, -7 +/- 4%, and 2 +/- 3% change in leg blood flow at 20%, 40%, and 60% of WR(max), respectively). These findings support a significant contribution of ET-1 and alpha-adrenergic receptors in the regulation of skeletal muscle blood flow in the human leg at rest and suggest a similar, intensity-dependent "lysis" of peripheral ET and alpha-adrenergic vasoconstriction during dynamic exercise.

Endothelins in health and disease

Endothelins are powerful vasoconstrictor peptides that also play numerous other roles. The endothelin (ET) family consists of three peptides produced by a variety of tissues. Endothelin-1 (ET-1) is the principal isoform produced by the endothelium in the human cardiovascular system, and it exerts its actions through binding to specific receptors, the so-called type A (ET(A)) and type B (ET(B)) receptors. ET-1 is primarily a locally acting paracrine substance that appears to contribute to the maintenance of basal vascular tone. It is also activated in several diseases, including congestive heart failure, arterial hypertension, atherosclerosis, endothelial dysfunction, coronary artery diseases, renal failure, cerebrovascular disease, pulmonary arterial hypertension, and sepsis. Thus, ET-1 antagonists are promising new agents. They have been shown to be effective in the management of primary pulmonary hypertension, but disappointing in heart failure. Clinical trials are needed to determine whether manipulation of the ET system will be beneficial in other diseases.

Selective Endothelin-A Receptor Inhibition After Cardiac Surgery: A Safety and Feasibility Study

BACKGROUND

Increased synthesis and release of the bioactive peptide endothelin has been shown to change hemodynamics and postoperative recovery after cardiac surgery. However, the clinical effects of selective interruption of endothelin signaling have not been studied. Because the endothelin-A (ET-A) receptor subtype is the primary cardiovascular effector for endothelin, this study used the ET-A receptor antagonist sitaxsentan sodium (TBC11251Na) to evaluate: (1) dose-dependent changes in pulmonary artery pressure (PAP) and pulmonary (PVRI) and systemic (SVRI) vascular resistance index in patients undergoing on-pump coronary revascularization; and (2) whether ET-RA administration was associated with increased adverse events.

METHODS

Patients (n = 44, age, 62 +/- 1 years) were randomized to receive vehicle (n = 9) or different bolus infusions of ET-A receptor antagonist: 0.1 (n = 9), 0.5 (n = 9) 1.0 (n = 9), and 2.0 mg/kg (n = 8) at separation from cardiopulmonary bypass (CPB). Adverse events were tabulated until hospital discharge. Results were expressed as changes from a composite baseline value, or from time 0 due to a high degree of intrapatient measurement variability in the postoperative period.

RESULTS

PAP increased by 27% +/- 13% from baseline (19 +/- 1 mm Hg) in the vehicle group at 6 hours post-CPB (p < 0.05). PAP fell from this post-CPB vehicle value in a dose-dependent manner with the ET-A receptor antagonist; with a significant reduction observed at 2 mg/kg (7% +/- 8% increase from baseline, p < 0.05). PVRI was reduced by 28.6% +/- 16% from baseline (249 +/- 22 dyn x s x cm(-5) x m(-2)) in the 2 mg/kg ET-A receptor antagonist group at 30 minutes post-CPB and remained reduced up to 6 hours post-CPB (p < 0.05). SVRI was reduced from baseline (2770 +/- 106 dyn x s x cm(-5) x m(-2)) by 51% +/- 6% in the 2.0 mg/kg ET-A receptor antagonist group at 30 minutes post-CPB (p < 0.05) and remained reduced up to 6 hours post-CPB. A total of 203 adverse events were tabulated in the postoperative period and were equally distributed across the five treatment groups, with no direct attributions to ET-A receptor antagonist treatment.

CONCLUSIONS

This unique study demonstrates that heightened endothelin-A receptor activation contributes to hemodynamic changes in patients after CPB. Selective inhibition of the endothelin receptor system can be successfully and safely performed in patients undergoing cardiac surgery and thereby reveals a potential, and clinically relevant therapeutic target.