Endothelin and endothelin receptors in the renal and cardiovascular systems. Life Sci. 2012;91:490-500. [PMID: 22480517 DOI: 10.1016/j.lfs.2012.03.026]

Endogenous hydrogen sulfide persulfidates endothelin type A receptor to inhibit pulmonary arterial smooth muscle cell proliferation

BACKGROUND

The binding of endothelin-1 (ET-1) to endothelin type A receptor (ETAR) performs a critical action in pulmonary arterial smooth muscle cell (PASMC) proliferation leading to pulmonary vascular structural remodeling. More evidence showed that cystathionine γ-lyase (CSE)-catalyzed endogenous hydrogen sulfide (H2S) was involved in the pathogenesis of cardiovascular diseases. In this study, we aimed to explore the effect of endogenous H2S/CSE pathway on the ET-1/ETAR binding and its underlying mechanisms in the cellular and animal models of PASMC proliferation.

METHODS AND RESULTS

Both live cell imaging and ligand-receptor assays revealed that H2S donor, NaHS, inhibited the binding of ET-1/ETAR in human PASMCs (HPASMCs) and HEK-293A cells, along with an inhibition of ET-1-activated HPASMC proliferation. While, an upregulated Ki-67 expression by the pulmonary arteries, a marked pulmonary artery structural remodeling, and an increased pulmonary artery pressure were observed in CSE knockout (CSE-KO) mice with a deficient H2S/CSE pathway compared with those in the wild type (WT) mice. Meanwhile, NaHS rescued the enhanced binding of ET-1 with ETAR and cell proliferation in the CSE-knockdowned HPASMCs. Moreover, the ETAR antagonist BQ123 blocked the enhanced proliferation of CSE-knockdowned HPASMCs. Mechanistically, ETAR persulfidation was reduced in the lung tissues of CSE-KO mice compared to that in WT mice, which could be reversed by NaHS treatment. Similarly, NaHS persulfidated ETAR in HPASMCs and HEK-293A cells. Whereas a thiol reductant dithiothreitol (DTT) reversed the H2S-induced ETAR persulfidation and further blocked the H2S-inhibited binding of ET-1/ETAR and HPASMC proliferation. Furthermore, the mutation of ETAR at cysteine (Cys) 69 abolished the persulfidation of ETAR by H2S, and subsequently blocked the H2S-suppressed ET-1/ETAR binding and HPASMC proliferation.

CONCLUSION

Endogenous H2S persulfidated ETAR at Cys69 to inhibit the binding of ET-1 to ETAR, subsequently suppressed PASMC proliferation, and antagonized pulmonary vascular structural remodeling.

Unraveling Sex Differences in Kidney Health and CKD: A Review of the Effect of Sex Hormones

Sexual dimorphism plays an important role in the pathogenesis and progression of CKD. Men with CKD often exhibit faster kidney function decline, leading to higher rates of kidney failure and mortality compared with women. Studies suggest that sex hormones may influence this apparent dimorphism, although the mechanisms underlying these influences remain poorly understood. In this review, we first summarize recent findings on sex differences in the prevalence and progression of CKD. Subsequently, we will focus on ( 1 ) the role of sex hormones in these sex differences, ( 2 ) kidney structural and hemodynamic differences between men and women, ( 3 ) the influence of sex hormones on pathophysiological processes leading to kidney disease, including glomerular hyperfiltration and key pathways involved in kidney inflammation and fibrosis, and finally, focus on the consequences of the underrepresentation of women in clinical trials. Understanding these sex differences is critical for advancing precision medicine and improving outcomes for both men and women with CKD.

[New therapeutic targets in hypertension]

Even though a large number of antihypertensive drugs are suitable for hypertension treatment, some new therapeutic targets are recently under development. Most are focused in the treatment of resistant hypertension, added to the drugs currently available for treating such condition. Others have specific particularities in their duration of action, which allows their use once per month or every six months and could become alternatives to the current antihypertensive treatment. Most interesting therapeutic targets are the renin-angiotensin-aldosterone system, through interference with the RNA of the angiotensinogen, the inhibition of brain aminopeptidase III, the inhibition of aldosterone synthase, and new non-steroidal aldosterone receptor antagonists. In addition, dual endothelin receptor antagonists or agonists of the NPR1 receptor, the main effector of natriuretic peptides are other new interesting therapeutic possibilities. In this paper, we review clinical data on the development of the most interesting molecules acting through these new therapeutic targets.

Screening and evaluation of the hit compound from a DNA-encoded library derived from natural products based on immobilized endothelin receptor A

The enormous growing demand for drug candidates binding to endothelin receptor A (ETA) has made it necessary to continuously pursue new strategies for ligand screening and early evaluation. This work achieved the one-step immobilization of ETA based on the bioorthogonal chemistry between the epidermal growth factor receptor tag (EGFR-tag) and ibrutinib. Comprehensive characterizations including Western blot analysis are performed to realize the morphology, antibody/ligand recognition activity, and specificity of the immobilized ETA. Taking macitentan, ambrisentan, and bosentan as an example, we utilized the immobilized ETA to construct a thermodynamic model for the evaluation of the specific ligands binding to ETA. Using this model, we screened the potential compound NP845 from a DNA-encoded library with 10,686 members derived from natural products and calculated the association constant as (2.24 ± 0.15) × 105 M-1 at 37 °C, thereby demonstrating the good pharmacological activity of NP845. The entropy change (∆Sθ), enthalpy change (∆Hθ), and Gibbs free energy (∆Gθ) were 1.75 J/mol·K, -31.1 kJ/mol, and -31.6 kJ/mol at 37 °C, whereby we recognized the electrostatic force was the driving force of the interaction between NP845 and ETA. In vitro cell tests proved that NP845 can downregulate the expression level of PKA, B-Raf, MEK, and ERK1 in VSMC. Our results indicated that NP845 was a potential lead compound for fighting the ailments mediated by ETA.

Promising Therapeutic Treatments for Cardiac Fibrosis: Herbal Plants and Their Extracts

Cardiac fibrosis is closely associated with multiple heart diseases, which are a prominent health issue in the global world. Neurohormones and cytokines play indispensable roles in cardiac fibrosis. Many signaling pathways participate in cardiac fibrosis as well. Cardiac fibrosis is due to impaired degradation of collagen and impaired fibroblast activation, and collagen accumulation results in increasing heart stiffness and inharmonious activity, leading to structure alterations and finally cardiac function decline. Herbal plants have been applied in traditional medicines for thousands of years. Because of their naturality, they have attracted much attention for use in resisting cardiac fibrosis in recent years. This review sheds light on several extracts from herbal plants, which are promising therapeutics for reversing cardiac fibrosis.

Molecular regulation and therapeutic implications of cell death in pulmonary hypertension

Pulmonary hypertension (PH) is a clinical and pathophysiological syndrome caused by changes in pulmonary vascular structure or function that results in increased pulmonary vascular resistance and pulmonary arterial pressure, and it is characterized by pulmonary endothelial dysfunction, pulmonary artery media thickening, pulmonary vascular remodeling, and right ventricular hypertrophy, all of which are driven by an imbalance between the growth and death of pulmonary vascular cells. Programmed cell death (PCD), different from cell necrosis, is an active cellular death mechanism that is activated in response to both internal and external factors and is precisely regulated by cells. More than a dozen PCD modes have been identified, among which apoptosis, autophagy, pyroptosis, ferroptosis, necroptosis, and cuproptosis have been proven to be involved in the pathophysiology of PH to varying degrees. This article provides a summary of the regulatory patterns of different PCD modes and their potential effects on PH. Additionally, it describes the current understanding of this complex and interconnected process and analyzes the therapeutic potential of targeting specific PCD modes as molecular targets.

Endothelial Function and Hypoxic–Hyperoxic Preconditioning in Coronary Surgery with a Cardiopulmonary Bypass: Randomized Clinical Trial

A hypoxic–hyperoxic preconditioning (HHP) may be associated with cardioprotection by reducing endothelial damage and a beneficial effect on postoperative outcome in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Patients (n = 120) were randomly assigned to an HHP and a control group. A safe, inhaled oxygen fraction for the hypoxic preconditioning phase (10–14% oxygen for 10 min) was determined by measuring the anaerobic threshold. At the hyperoxic phase, a 75–80% oxygen fraction was used for 30 min. The cumulative frequency of postoperative complications was 14 (23.3%) in the HHP vs. 23 (41.1%), p = 0.041. The nitrate decreased after surgery by up to 20% in the HHP group and up to 38% in the control group. Endothelin-1 and nitric oxide metabolites were stable in HHP but remained low for more than 24 h in the control group. The endothelial damage markers appeared to be predictors of postoperative complications. The HHP with individual parameters based on the anaerobic threshold is a safe procedure, and it can reduce the frequency of postoperative complications. The endothelial damage markers appeared to be predictors of postoperative complications.

Novel Dual Endothelin Inhibitors in the Management of Resistant Hypertension

Resistant hypertension (RH) is defined as the failure to achieve blood pressure control despite using triple combination therapy with a renin-angiotensin system inhibitor (RAS-i), a calcium antagonist, and a diuretic. The endothelin (ET) system is implicated in the regulation of vascular tone, primarily through vasoconstriction, intervenes in cardiac contractility with inotropic effects, and contributes to water and sodium renal reabsorption. ET inhibitors, currently approved for the treatment of pulmonary hypertension, seem to be also useful for essential hypertension and RH as well. Studies into the development of new dual ET inhibitors, which inhibit both type A and B ET (ETA and ETB) receptors, present initial results of managing RH. Aprocitentan (ACT-132577) is a novel, orally active and well tolerated dual ET receptor antagonist, which has been examined in several experimental studies and clinical trials with promising results for RH control. The recent publication of the large PRECISION study in The Lancet journal provides further reassurance regarding the efficacy and safety of aprocitentan for RH, with the aim of overcoming unmet needs in the management of this difficult group of patients.

Endothelin and the Cardiovascular System: The Long Journey and Where We Are Going

Simple Summary

In this review, we describe the basic functions of endothelin and related molecules, including their receptors and enzymes. Furthermore, we discuss the important role of endothelin in several cardiovascular diseases, the relevant clinical evidence for targeting the endothelin pathway, and the scope of endothelin-targeting treatments in the future. We highlight the present uses of endothelin receptor antagonists and the advancements in the development of future treatment options, thereby providing an overview of endothelin research over the years and its future scope.

Abstract

Endothelin was first discovered more than 30 years ago as a potent vasoconstrictor. In subsequent years, three isoforms, two canonical receptors, and two converting enzymes were identified, and their basic functions were elucidated by numerous preclinical and clinical studies. Over the years, the endothelin system has been found to be critical in the pathogenesis of several cardiovascular diseases, including hypertension, pulmonary arterial hypertension, heart failure, and coronary artery disease. In this review, we summarize the current knowledge on endothelin and its role in cardiovascular diseases. Furthermore, we discuss how endothelin-targeting therapies, such as endothelin receptor antagonists, have been employed to treat cardiovascular diseases with varying degrees of success. Lastly, we provide a glimpse of what could be in store for endothelin-targeting treatment options for cardiovascular diseases in the future.

Understanding the Pathobiology of Pulmonary Hypertension Due to Left Heart Disease

The development of pulmonary hypertension (PH) is common and has adverse prognostic implications in patients with heart failure due to left heart disease (LHD), and thus far, there are no known treatments specifically for PH-LHD, also known as group 2 PH. Diagnostic thresholds for PH-LHD, and clinical classification of PH-LHD phenotypes, continue to evolve and, therefore, present a challenge for basic and translational scientists actively investigating PH-LHD in the preclinical setting. Furthermore, the pathobiology of PH-LHD is not well understood, although pulmonary vascular remodeling is thought to result from (1) increased wall stress due to increased left atrial pressures; (2) hemodynamic congestion-induced decreased shear stress in the pulmonary vascular bed; (3) comorbidity-induced endothelial dysfunction with direct injury to the pulmonary microvasculature; and (4) superimposed pulmonary arterial hypertension risk factors. To ultimately be able to modify disease, either by prevention or treatment, a better understanding of the various drivers of PH-LHD, including endothelial dysfunction, abnormalities in vascular tone, platelet aggregation, inflammation, adipocytokines, and systemic complications (including splanchnic congestion and lymphatic dysfunction) must be further investigated. Here, we review the diagnostic criteria and various hemodynamic phenotypes of PH-LHD, the potential biological mechanisms underlying this disorder, and pressing questions yet to be answered about the pathobiology of PH-LHD.

Angiotensin and Endothelin Receptor Structures With Implications for Signaling Regulation and Pharmacological Targeting

In conjunction with the endothelin (ET) type A (ETAR) and type B (ETBR) receptors, angiotensin (AT) type 1 (AT1R) and type 2 (AT2R) receptors, are peptide-binding class A G-protein-coupled receptors (GPCRs) acting in a physiologically overlapping context. Angiotensin receptors (ATRs) are involved in regulating cell proliferation, as well as cardiovascular, renal, neurological, and endothelial functions. They are important therapeutic targets for several diseases or pathological conditions, such as hypertrophy, vascular inflammation, atherosclerosis, angiogenesis, and cancer. Endothelin receptors (ETRs) are expressed primarily in blood vessels, but also in the central nervous system or epithelial cells. They regulate blood pressure and cardiovascular homeostasis. Pathogenic conditions associated with ETR dysfunctions include cancer and pulmonary hypertension. While both receptor groups are activated by their respective peptide agonists, pathogenic autoantibodies (auto-Abs) can also activate the AT1R and ETAR accompanied by respective clinical conditions. To date, the exact mechanisms and differences in binding and receptor-activation mediated by auto-Abs as opposed to endogenous ligands are not well understood. Further, several questions regarding signaling regulation in these receptors remain open. In the last decade, several receptor structures in the apo- and ligand-bound states were determined with protein X-ray crystallography using conventional synchrotrons or X-ray Free-Electron Lasers (XFEL). These inactive and active complexes provide detailed information on ligand binding, signal induction or inhibition, as well as signal transduction, which is fundamental for understanding properties of different activity states. They are also supportive in the development of pharmacological strategies against dysfunctions at the receptors or in the associated signaling axis. Here, we summarize current structural information for the AT1R, AT2R, and ETBR to provide an improved molecular understanding.

The Roles of Cardiac Fibroblasts and Endothelial Cells in Myocarditis

In myocarditis caused by various etiologies, activated immune cells and the immune regulatory factors released by them play important roles. But in this complex microenvironment, non-immune cells and non-cardiomyocytes in the heart, such as cardiomyocytes (CMs), cardiac fibroblasts (CFs) and endothelial cells (ECs), play the role of “sentinel”, amplify inflammation, and interact with the cardiomyocytes. The complex interactions between them are rarely paid attention to. This review will re-examine the functions of CFs and ECs in the pathological conditions of myocarditis and their direct and indirect interactions with CMs, in order to have a more comprehensive understanding of the pathogenesis of myocarditis and better guide the drug development and clinical treatment of myocarditis.

Increased Circulating Endothelin 1 Is Associated With Postoperative Hypoxemia in Infants With Single-Ventricle Heart Disease Undergoing Superior Cavopulmonary Anastomosis

Background Inadequate pulmonary vascular growth results in morbidity for many children with single-ventricle heart disease (SVHD). Endothelin 1 (ET1) is a potent vasoconstrictor and stimulator of pulmonary artery smooth muscle proliferation. Circulating ET1 levels and their association with outcomes have not been studied during early SVHD palliation. We aimed to define circulating levels of ET1 in patients with SVHD undergoing stage 2 palliation and evaluate their relationship to postoperative hypoxemia. We hypothesized that patients with SVHD with higher ET1 concentration would have a greater post-stage 2 hypoxemia. Methods and Results Prospective cohort study of 55 subjects with SVHD undergoing stage 2 palliation and 50 controls. Samples for ET1 analysis were collected at preoperation (systemic and pulmonary vein) and 2, 24, and 48 hours postoperation for cases and a single time point for controls. The primary outcome was percentage of first 48 postoperative hours with clinically significant hypoxemia (saturation, <70%). ET1 concentration was lower in preoperative cases than controls (2.2 versus 2.7 pg/mL; P=0.0015) and in the pulmonary vein than systemic vein (1.7 versus 2.2 pg/mL; P<0.001). ET1 level increased by 2 hours postoperation and trended back to baseline by 48 hours. Higher preoperative pulmonary vein ET1 and 2 hours postoperative ET1 were associated with larger hypoxemia burden (10.6% versus 2.7% [P=0.0081]; and 7.6% versus 3.2% [P=0.01], respectively). Multivariable testing demonstrated ET1 concentration and cardiopulmonary bypass time were associated with hypoxemia, whereas catheterization measurements and clinical variables were not. Conclusions Infants with SVHD with higher perioperative ET1 concentration experience more post-stage 2 hypoxemia. ET1 activity may be a modifiable risk factor of pulmonary vascular inadequacy for stage 2 palliation.

The role of endothelin II type A receptor (ETAR) in transplant injury

PURPOSE OF REVIEW

Antibody-mediated rejection is the leading cause of deterioration of graft function and graft loss after kidney transplantation. Recent studies have reported an increasing role of non-HLA antibodies in the humoral injury after kidney transplantation. We decided to present the influence of non-HLA antibodies - anti-endothelin II type A receptor (ETAR) on a transplanted kidney and characterize the significance of their receptor.

RECENT FINDINGS

The role of non-HLA antibodies is still uncertain. Many studies suggest that the presence of non-HLA antibodies, including anti-ETAR antibodies, is among the risk factors for antibody-mediated rejection, graft injury, and graft loss. The discovery of new antigen targets and antibodies, which participate in the humoral response, has provided a significantly better understanding of the mechanism of antibody-mediated rejection after organ transplantation.

SUMMARY

Endothelin and its receptors play an important role in physiology and pathophysiology after solid organ transplantation. ETAR and antibodies against ETAR may participate in humoral rejection and graft damage. The measurement of anti-ETAR antibodies may identify patients with an increased risk of rejection and even loss of a transplanted organ. Expression of ETAR detected in biopsy of transplant could become an additional tool used to better understand humoral activity. More research is needed to address many questions about non-HLA directed rejection and graft damage.

Prenatal hypoxia induced ETBR activation and abnormal ROS signalling in pulmonary artery cells of rat offspring

Pulmonary arterial hypertension is a progressive disorder characterized by remodeling and increased small pulmonary arteries resistance. Endothelin-1 (ET-1) was related to PAH and ET-1 receptors were up-regulated selectively in the lung when exposed to toxic factor hypoxia. However, the role of ET-1 signaling in the pathogenesis of prenatal hypoxia-induced pulmonary abnormalities remains to be elucidated. Pregnant rats were divided into prenatal hypoxia (10.5 % O2 from gestational day 4-21) and control group. Their three-month-old offspring male rats were tested for vascular functions and molecular analysis, DNA methylation was assessed for cellular hypoxia. Functional testing showed that ET-1-mediated vasoconstriction was enhanced, and the expressions of endothelin A receptor/B receptor (ETAR/ETBR), inositol 1,4,5-trisphosphate receptor, type 1, and the sensitivity of calcium channels were increased in the small pulmonary arteries following prenatal hypoxia. q-PCR and DHE staining showed that the expressions of NADPH oxidase 1/4 (Nox1/4) were up-regulated, along with the increased production of superoxide anion. Furthermore, superoxide anion promoted ET-1-mediated pulmonary artery contraction. In the pulmonary artery smooth muscle cell experiments, q-PCR, Western Blot, CCK8 and DHE staining showed that the expressions of ETBR, Nox1/4, and superoxide anion were increased by hypoxia, along with promoted cell proliferation. 2,2,6,6-Tetramethyl-1-piperidinyloxy reversed hypoxia-induced cell proliferation. ETBR antagonist BQ788 inhibited hypoxia-increased expressions of Nox1/4, superoxide anion production, and proliferation of cells. Moreover, methylation analysis indicated that hypoxia decreased the methylation levels of the ETBR promoter in the pulmonary artery smooth muscle cells. The results indicated that prenatal toxic factor hypoxia resulted in abnormal ETBR activation, which enhanced ET-1-mediated vasoconstriction of pulmonary arteries and pulmonary artery smooth muscle cell proliferation through ETBR/Nox1/4-derived ROS pathway.

Renal biomarkers of acute kidney injury in response to increasing intermittent hypoxia episodes in the neonatal rat

BACKGROUND

We tested the hypotheses that: 1) early exposure to increasing episodes of clinically relevant intermittent hypoxia (IH) is detrimental to the developing kidneys; and 2) there is a critical number of daily IH episodes which will result in irreparable renal damage that may involve angiotensin (Ang) II and endothelin (ET)-1.

METHODS

At birth (P0), neonatal rat pups were exposed to brief IH episodes from the first day of life (P0) to P7 or from P0-P14. Pups were either euthanized immediately or placed in room air (RA) until P21. RA littermates served as controls. Kidneys were harvested at P7, P14, and P21 for histopathology; angiotensin converting enzyme (ACE), ACE-2, ET-1, big ET-1, and malondialdehyde (MDA) levels; immunoreactivity of ACE, ACE-2, ET-1, ET-2, ET receptors (ETAR, ETBR), and hypoxia inducible factor (HIF)1α; and apoptosis (TUNEL stain).

RESULTS

Histopathology showed increased renal damage with 8-12 IH episodes/day, and was associated with Ang II, ACE, HIF1α, and apoptosis. ACE-2 was not expressed at P7, and minimally increased at P14. However, a robust ACE-2 response was seen during recovery with maximum levels noted in the groups recovering from 8 IH episodes/day. ET-1, big ET-1, ETAR, ETBR, and MDA increased with increasing levels of neonatal IH.

CONCLUSIONS

Chronic neonatal IH causes severe damage to the developing kidney with associated elevations in vasoconstrictors, suggesting hypertension, particularly with 8 neonatal IH episodes. ACE-2 is not activated in early postnatal life, and this may contribute to IH-induced vasoconstriction. Therapeutic targeting of ACE and ET-1 may help decrease the risk for kidney injury in the developing neonate to prevent and/or treat neonatal acute kidney injury and/or chronic kidney disease.

Endothelin receptors in renal interstitial cells do not contribute to the development of fibrosis during experimental kidney disease

Renal interstitial fibrosis is characterized by the development of myofibroblasts, originating from resident renal and immigrating cells. Myofibroblast formation and extracellular matrix production during kidney damage are triggered by various factors. Among these, endothelins have been discussed as potential modulators of renal fibrosis. Utilizing mouse models of adenine nephropathy (AN) and unilateral ureter occlusion (UUO), this study aimed to investigate the contribution of endothelin signaling in stromal mesenchymal resident renal interstitial cells. We found in controls that adenine feeding and UUO caused marked upregulations of endothelin-1 (ET-1) gene expression in endothelial and in tubular cells and a strong upregulation of ET_A-receptor (ET_A-R) gene expression in interstitial and mesangial cells, while the gene expression of ET_B-receptor (ET_B-R) did not change. Conditional deletion of ET_A-R and ET_B-R gene expression in the FoxD1 stromal cell compartment which includes interstitial cells significantly reduced renal ET_A-R gene expression and moderately lowered renal ET_B-R gene expression. ET receptor (ET-R) deletion exerted no apparent effects on kidney development nor on kidney function. Adenine feeding and UUO led to similar increases in profibrotic and proinflammatory gene expression in control as well as in ET_A^flflET_B^flfl FoxD1^Cre+ mice (ET-Ko). In summary, our findings suggest that adenine feeding and UUO activate endothelin signaling in interstitial cells which is due to upregulated ET_A-R expression and enhanced renal ET-1 production Our data also suggest that the activation of endothelin signaling in interstitial cells has less impact for the development of experimentally induced fibrosis.

Inhibition of endothelin A receptor by a novel, selective receptor antagonist enhances morphine-induced analgesia: Possible functional interaction of dimerized endothelin A and μ-opioid receptors

BACKGROUND

The misuse of opioids has led to an epidemic in recent times. The endothelin A receptor (ETAR) has recently attracted attention as a novel therapeutic target to enhance opioid analgesia. We hypothesized that endothelin A receptors may affect pain mechanisms by heterodimerization with μ opioid receptors. We examined the mechanisms of ETAR-mediated pain and the potential therapeutic effects of an ETAR antagonist, Compound-E, as an agent for analgesia.

METHODS

Real-time in vitro effect of Compound-E on morphine response was assessed in HEK293 cells expressing both endothelin A and μ opioid receptors through CellKey™ and cADDis cAMP assays. Endothelin A/μ opioid receptor dimerization was assessed by immunoprecipitation and live cell imaging. The in vivo effect of Compound-E was evaluated using a morphine analgesia mouse model that observed escape response behavior, body temperature, and locomotor activity.

RESULTS

In CellKey™ and cAMP assays, pretreatment of cells with endothelin-1 attenuated morphine-induced responses. These responses were improved by Compound-E, but not by BQ-123 nor by bosentan, an ETAR and endothelin B receptor antagonist. Dimerization of ETARs and μ opioid receptors was confirmed by Western blot and total internal reflection fluorescence microscopy in live cells. In vivo, Compound-E potentiated and prolonged the analgesic effects of morphine, enhanced hypothermia, and increased locomotor activity compared to morphine alone.

CONCLUSION

The results suggest that attenuation by endothelin-1 of morphine analgesia may be caused by dimerization of Endothelin A/μ opioid receptors. The novel ETAR antagonist Compound-E could be an effective adjunct to reduce opioid use.

Caloric restriction inhibits renal artery ageing by reducing endothelin-1 expression

Background

The renal artery plays a central role in renal perfusion and is critical for proper renal function. Ageing is an independent risk factor for both impaired renal function and vascular disorders, and associated with an increase in the expression of the vasoconstrictor endothelin-1 (ET-1), and caloric restriction (CR) without malnutrition has been shown to be an effective inhibitor of renal dysfunction induced by ageing. The objective of this study was to determine whether CR-mediated alleviation of renal dysfunction is mediated by ET-1 expression.

Methods

The young (2 months, 2 M) and old (12 months, 12 M) Sprague-Dawley male rats were used and fed ad libitum. The 12-month-old rats were further divided into 12 M and 12 M-caloric restriction (CR) (30% calorie restriction). After 8 weeks, the renal tissues were showed by PAS staining, and age-related metabolic parameters and renal functions were detected in each group of rats. The inflammatory cytokines of interleukin (IL)-6, IL-1β, tumor necrosis factor alpha (TNF-α), and transforming growth factor beta 1 (TGF-β1) were analyzed using ELISA. The mRNA and protein expression in the renal artery were analysis by qRT-PCR and Immunoblot analysis.

Results

Ageing was associated with significant increases in 24 h urine protein content and serum triglyceride and cholesterol in 12 M rats, both of which were significantly inhibited in 12 M-CR. The mRNA expression and the secretion of IL-6, IL-1β, TNF-α, and TGF-β1 in the renal artery was significantly increased with ageing and inhibited by CR. CR also inhibited ageing-induced Edn1 (encoding ET-1) mRNA and protein expression in the renal artery. In addition, CR could regulate ET-1 expression by inhibiting the activation of NF-κB signaling and activation and induction in the expression of NF-E2-related factor 2 (Nrf2) and histone deacetylase and gene repressor sirtuin 1 (SIRT1), both of which play a central role in mitigating oxidative stress in young rats.

Conclusions

Moderate CR can reverse the ageing related kidney dysfunction by reducing the ET-1 expression. CR might be used as an alternative to prevent the ageing induced renal artery dysfunction.

Update on pediatric pulmonary arterial hypertension

PURPOSE OF REVIEW

Pulmonary arterial hypertension (PAH) causes high morbidity and mortality in children. In this review, we discuss advances in diagnosis and treatment of this disorder.

RECENT FINDINGS

Proceedings published from the 2018 World Symposium updated the definition of pulmonary hypertension to include all adults and children with mean pulmonary artery pressure more than 20 mmHg. Targeted PAH therapy is increasingly used off-label, but in 2017, bosentan became the first Food and Drug Administration-targeted PAH therapy approved for use in children.

SUMMARY

In recent years, advanced imaging and clinical monitoring have allowed improved risk stratification of pulmonary hypertension patients. New therapies, approved in adults and used off-label in pediatric patients, have led to improved outcomes for affected children.

An Outline of Renal Artery Stenosis Pathophysiology-A Narrative Review

Renal artery stenosis (RAS) is conditioned mainly by two disturbances: fibromuscular dysplasia or atherosclerosis of the renal artery. RAS is an example of renovascular disease, with complex pathophysiology and consequences. There are multiple pathophysiological mechanisms triggered in response to significant renal artery stenosis, including disturbances within endothelin, kinin-kallikrein and sympathetic nervous systems, with angiotensin II and the renin-angiotensin-aldosterone system (RAAS) playing a central and key role in the pathogenesis of RAS. The increased oxidative stress and the release of pro-inflammatory mediators contributing to pathological tissue remodelling and renal fibrosis are also important pathogenetic elements of RAS. This review briefly summarises these pathophysiological issues, focusing on renovascular hypertension and ischemic nephropathy as major clinical manifestations of RAS. The activation of RAAS and its haemodynamic consequences is the primary and key element in the pathophysiological cascade triggered in response to renal artery stenosis. However, the pathomechanism of RAS is more complex and also includes other disturbances that ultimately contribute to the development of the diseases mentioned above. To sum up, RAS is characterised by different clinical pictures, including asymptomatic disorders diagnosed in kidney imaging, renovascular hypertension, usually characterised by severe course, and chronic ischemic nephropathy, described by pathological remodelling of kidney tissue, ultimately leading to kidney injury and chronic kidney disease.

Blood pressure and albuminuria in a female mouse model of systemic lupus erythematosus: impact of long-term high salt consumption

Hypertension and kidney involvement are common in patients with autoimmune disease. Sodium intake is linked to hypertension in both human and animal studies. Evidence suggests that dietary salt may be an important environmental factor that promotes autoimmune activity. Therefore, we hypothesized that a long-term high-salt diet would accelerate the progression of autoimmunity, hypertension, and albuminuria during systemic lupus erythematosus (SLE), an autoimmune disease that predominantly affects young women and has a high prevalence of hypertension and renal disease. To test this hypothesis, an established experimental model of SLE (female NZBWF1 mice) that develops hypertension and renal disease was used. SLE mice were fed a high-salt (4% NaCl) or normal (0.4% NaCl) diet for 24 wk beginning at 10 wk of age and ending at 34 wk of age, a time by which female NZBWF1 mice typically have hypertension and exhibit signs of renal disease. Plasma anti-dsDNA autoantibodies were measured as an indicator of active SLE disease, and urinary albumin was monitored longitudinally as a marker of renal disease. Arterial pressure was measured in conscious, freely moving mice at 34 wk of age. Urinary endothelin-1 (ET-1) excretion, renal endothelin A and B receptor protein expression, and renal mRNA expression of NOS1, NOS2, NOX2, MCP-1, TNF-α, serum- and glucocorticoid-regulated kinase 1, and interleukin-2 (IL-2) were assessed to determine the impact on gene products commonly altered by a high-salt diet. SLE mice fed a high-salt diet had increased circulating autoantibodies, but the high-salt diet did not significantly affect albuminuria or arterial pressure. Urinary ET-1 excretion was increased, whereas renal endothelin A receptor and IL-2 expression were decreased in response to a high-salt diet. These data suggest that a chronic high-salt diet may not accelerate cardiovascular and renal consequences commonly associated with SLE.

Pediatric Pulmonary Arterial Hypertension

Pulmonary hypertension (PH), the syndrome of increased pressure in the pulmonary arteries, is associated with significant morbidity and mortality for affected children and is associated with a variety of potential underlying causes. Several pulmonary arterial hypertension-targeted therapies have become available to reduce pulmonary artery pressure and improve outcome, but there is still no cure for most patients. This review provides a description of select causes of PH encountered in pediatrics and an update on the most recent data pertaining to evaluation and management of children with PH. Available evidence for specific classes of PH-targeted therapies in pediatrics is discussed.

Predictive model of bosentan-induced liver toxicity in Japanese patients with pulmonary arterial hypertension

Bosentan, an endothelin receptor antagonist, has been widely used as a first-line medication for the treatment of pulmonary arterial hypertension (PAH). It has been shown to improve symptoms of hypertension, exercise capacity, and hemodynamics and prolong time to clinical worsening. However, liver dysfunction is a major side effect of bosentan treatment that could hamper the optimal management of patients with PAH. Previously, we demonstrated, using drug metabolism enzymes and transporters analysis, that the carbohydrate sulfotransferase 3 (CHST3) and CHST13 alleles are significantly more frequent in patients with elevated aminotransferases during therapy with bosentan than they are in patients without liver toxicity. In addition, we constructed a pharmacogenomics model to predict bosentan-induced liver injury in patients with PAH using two single-nucleotide polymorphisms and two nongenetic factors. The purpose of the present study was to externally validate the predictive model of bosentan-induced liver toxicity in Japanese patients. We evaluated five cases of patients treated with bosentan, and one presented with liver dysfunction. We applied mutation alleles of CHST3 and CHST13, serum creatinine, and age to our model to predict liver dysfunction. The sensitivity and specificity were calculated as 100% and 50%, respectively. Considering that PAH is a rare disease, multicenter collaboration would be necessary to validate our model.

Endothelin converting enzyme-1 (ECE-1) deletion in association with Endothelin-1 downregulation ameliorates kidney fibrosis in mice

Kidney fibrosis is a common final pathway of chronic kidney diseases, which are characterized by renal architecture damage, inflammation, fibroblast expansion and myofibroblast formation. Endothelin converting enzyme-1 (ECE-1) contributes to activation of Endothelin-1 (ET-1), a potent vasoconstrictor and pro-fibrotic substance. This study elucidated the effect of ECE-1 knockout in kidney fibrosis model in mice in association of ET-1 downregulation. Kidney fibrosis was performed in ECE-1 knockout (ECE-1 KO) and vascular endothelial derived ET-1 KO (VEETKO) mice (2 months, 20-30 g, n = 30) and their wild type (WT) littermates using unilateral ureteral obstruction (UUO) procedure. Mice were euthanized on day-7 and day-14 after UUO. Histopathological analysis was conducted for fibrosis and tubular injury. Immunostainings were done to quantify macrophages (F4/80), fibroblasts (FSP-1) and myofibroblasts (α-SMA). Monocyte Chemoattractant Protein-1 (MCP-1), ECE-1 and preproET-1 (ppET-1) mRNA expression were quantified with qRT-PCR, while Transforming Growth Factor-β1 (TGF-β1) and α-SMA protein level were quantified with Western blot. ECE-1 KO mice demonstrated reduction of ECE-1 and ppET-1 mRNA expression, attenuation of kidney fibrosis, tubular injury, MCP-1 mRNA expression and macrophage number compared to WT. Double immunostaining revealed fibroblast to myofibroblast formation after UUO, while ECE-1 KO mice had significantly lower fibroblast number and myofibroblast formation compared to WT, which were associated with significantly lower TGF-β1 and α-SMA protein levels in day-14 of UUO. VEETKO mice also demonstrated attenuation of ET-1 protein level, fibrosis and myofibroblast formation. In conclusion, ECE-1 knockout and ET-1 downregulation attenuated kidney fibrosis.

Influence of Hypoxic and Hyperoxic Preconditioning on Endothelial Function in a Model of Myocardial Ischemia-Reperfusion Injury with Cardiopulmonary Bypass (Experimental Study)

The aim of the experiment was to evaluate the effect of preconditioning based on changes in inspiratory oxygen fraction on endothelial function in the model of ischemia-reperfusion injury of the myocardium in the condition of cardiopulmonary bypass. The prospective randomized study included 32 rabbits divided into four groups: hypoxic preconditioning, hyperoxic preconditioning, hypoxic-hyperoxic preconditioning, and control group. All animals were anesthetized and mechanically ventilated. We provided preconditioning, then started cardiopulmonary bypass, followed by induced acute myocardial infarction (ischemia 45 min, reperfusion 120 min). We investigated endothelin-1, nitric oxide metabolites, asymmetric dimethylarginine during cardiopulmonary bypass: before ischemia, after ischemia, and after reperfusion. We performed light microscopy of myocardium, kidney, lungs, and gut mucosa. The endothelin-1 level was much higher in the control group than in all preconditioning groups after ischemia. The endothelin-1 even further increased after reperfusion. The total concentration of nitric oxide metabolites was significantly higher after all types of preconditioning compared with the control group. The light microscopy of the myocardium and other organs revealed a diminished damage extent in the hypoxic-hyperoxic preconditioning group as compared to the control group. Hypoxic-hyperoxic preconditioning helps to maintain the balance of nitric oxide metabolites, reduces endothelin-1 hyperproduction, and enforces organ protection.

An update on the diagnosis and treatment of pediatric pulmonary hypertension

INTRODUCTION

Pulmonary hypertension (PH) is a heterogeneous disease that mainly affects the pulmonary arterioles, leading to significant morbidity and mortality. Pulmonary hypertension in children from birth to adolescence presents important differences from that of adults. The majority of pediatric pulmonary arterial hypertension (PAH) cases are idiopathic or associated with congenital heart disease. However, the management of pediatric PAH mainly depends on the results of evidence-based adult studies and the clinical experiences of pediatric experts.

AREAS COVERED

This article briefly reviews the recent updates on the definition, classification, and diagnostic evaluation of pediatric PAH and their impact on treatment strategies. The main purpose of this review is to discuss the current pediatric therapies, as well as the prospective therapies, in terms of therapeutic targets, actions, side effects, and dosages.

EXPERT OPINION

Although there is no cure for PAH, recent advances in the form of new treatment options have improved the quality of life and survival rates of PAH patients. PAH-targeted drugs and treatment strategies for adult PAH have not been sufficiently studied in children. However, the growing scientific activity in that field will surely change the treatment option recommendations in pediatric PH from experience-based to evidence-based in the near future.

Effects of coal-fired PM2.5 on the expression levels of atherosclerosis-related proteins and the phosphorylation level of MAPK in ApoE-/- mice

Background

Air pollution increases the morbidity and mortality of cardiovascular disease (CVD). Atherosclerosis (AS) is the pathological basis of most CVD, and the progression of atherosclerosis and the increase of fragile plaque rupture are the mechanism basis of the relationship between atmospheric particulate pollution and CVD. The aim of the present study was to investigate the effects of coal-fired fine particulate matter (PM_2.5) on the expression levels of atherosclerosis-related proteins (von Willebrand factor (vWF), Endothelin-1 (ET-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin, and to explore the role and mechanism of the progression of atherosclerosis induced by coal-fired PM_2.5 via the mitogen-activated protein kinase (MAPK) signaling pathways.

Methods

Different concentrations of PM_2.5 were given to apolipoprotein-E knockout (ApoE^−/−) mice via intratracheal instillation for 8 weeks. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of vWF, ET-1 in serum of mice. Immunohistochemistry was used to observe the expression and distribution of ICAM-1 and E-selectin in the aorta of mice. Western blot was used to investigate the phosphoylation of proteins relevant to MAPK signaling pathways.

Results

Coal-fired PM_2.5 exacerbated atherosclerosis induced by a high-fat diet. Fibrous cap formation, foam cells accumulation, and atherosclerotic lesions were observed in the aortas of PM_2.5-treated mice. Coal-fired PM_2.5 increased the protein levels of ET-1, ICAM-1, and E-selectin, but there was no significant difference in the vWF levels between the PM_2.5-treatment mice and the HFD control mice. Coal-fired PM_2.5 promoted the phosphorylation of p38, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) in aortic tissues of mice.

Conclusion

Coal-derived PM_2.5 exacerbated the formation of atherosclerosis in mice, increased the expression levels of atherosclerosis-related proteins in mice serum, and promoted the phosphorylation of proteins relevant to MAPK signaling pathway. Thus, MAPK signaling pathway may play a role in the atherosclerosis pathogenesis induced by Coal-derived PM_2.5.

Aggravated endothelial endocrine dysfunction and intimal thickening of renal artery in high-fat diet-induced obese pigs following renal denervation

Background

Renal denervation (RDN) targeting the sympathetic nerves in the renal arterial adventitia as a treatment of resistant hypertension can cause endothelial injury and vascular wall injury. This study aims to evaluate the risk of atherosclerosis induced by RDN in renal arteries.

Methods

A total of 15 minipigs were randomly assigned to 3 groups: (1) control group, (2) sham group, and (3) RDN group (n = 5 per group). All pigs were fed a high-fat diet (HFD) for 6 months after appropriate treatment. The degree of intimal thickening of renal artery and the conversion of endothelin 1 (ET-1) receptors were evaluated by histological staining. Western blot was used to assess the expression of nitric oxide (NO) synthesis signaling pathway, ET-1 and its receptors, NADPH oxidase 2 (NOX2) and 4-hydroxynonenal (4-HNE) proteins, and the activation of NF-kappa B (NF-κB).

Results

The histological staining results suggested that compared to the sham treatment, RDN led to significant intimal thickening and significantly promoted the production of endothelin B receptor (ET_BR) in vascular smooth muscle cells (VSMCs). Western blotting analysis indicated that RDN significantly suppressed the expression of AMPK/Akt/eNOS signaling pathway proteins, and decreased the production of NO, and increased the expression of endothelin system proteins including endothelin-1 (ET-1), endothelin converting enzyme 1 (ECE1), endothelin A receptor (ET_AR) and ET_BR; and upregulated the expression of NOX2 and 4-HNE proteins and enhanced the activation of NF-kappa B (NF-κB) when compared with the sham treatment (all p < 0.05). There were no significant differences between the control and sham groups (all p > 0.05).

Conclusions

RDN aggravated endothelial endocrine dysfunction and intimal thickening, and increased the risk of atherosclerosis in renal arteries of HFD-fed pigs.

Endothelins and their receptors in embryo implantation

As a critical stage of pregnancy, the implantation of blastocysts into the endometrium is a progressive, excessively regulated local tissue remodeling step involving a complex sequence of genetic and cellular interplay executed within an optimal time frame. For better understanding the causes of infertility and, more importantly, for developing powerful strategies for successful implantations and combating infertility, an increasing number of recent studies have been focused on the identification and study of newly described substances in the reproductive tree. The endothelins (ET), a 21-aminoacidic family of genes, have been reported to be responsible for the contraction of vascular and nonvascular smooth muscles, including the smooth muscles of the uterus. Therefore, this review aims to comprehensively discuss the physiological role of endothelins and signaling through their receptors, as well as their probable involvement in the implantation process.

[Evaluation of endothelial dysfunction and the possibility of its correction at the present stage in patients with cardiovascular diseases]

The review describes the current understanding of endothelial dysfunction, methods of its evaluation, and highlights the advantages and disadvantages of various techniques. The role of nitric oxide and endothelin as important markers of endothelial dysfunction is shown, and the methods of their determination in clinical practice are described. The authors conclude that in order to improve the life expectancy and quality of life of patients with cardiovascular diseases, reduce the risk and frequency of complications and mortality rates, it is necessary to study the function of endothelium in more detail and to look for ways of drug correction, taking into account the pathogenetic mechanisms of its formation.

Diagnosis and treatment of pediatric pulmonary arterial hypertension

INTRODUCTION

Pediatric pulmonary arterial hypertension (PAH) remains a rare and severe disease with a poor prognosis. PAH may be idiopathic, heritable or associated with systemic conditions in particular associated with congenital heart disease. Areas covered: A thorough and extensive diagnostic approach is required for a correct diagnosis. The outcome has improved over the last decade with a better diagnostic approach and with the initiation of new targeted therapies. However, there is still significant progress to achieve as there is still no cure for this devastating disease. Expert opinion: Adapted clinical studies to define the best therapeutic approach are needed. Even if the treatment approach is still mainly derived from adult data and expert consensus, several studies and registries are currently underway and should deliver important information in the next future. This review aims to give an overview of the current diagnosis and treatment strategies of PAH.

H2S mediates the vasodilator effect of endothelin-1 in the cerebral circulation

H₂S is an endogenous gasotransmitter that increases cerebral blood flow. In the cerebral vascular endothelium, H₂S is produced by cystathionine δ-lyase (CSE). Endothelin-1 (ET-1) has constrictor and dilator influences on the cerebral circulation. The mechanism of the vasodilation caused by ET-1 may involve endothelium-derived factors. We hypothesize that ET-1-elicited dilation of pial arterioles requires an elevation of H₂S production in the cerebral vascular endothelium. We investigated the effects of ET-1 on CSE-catalyzed brain H₂S production and pial arteriolar diameter using cranial windows in newborn pigs in vivo. H₂S was measured in periarachnoid cerebrospinal fluid. ET-1 (10^-12-10^-8 M) caused an elevation of H₂S that was reduced by the CSE inhibitors propargylglycine (PPG) and β-cyano-l-alanine (BCA). Low doses of ET-1 (10^-12-10^-11 M) produced vasodilation of pial arterioles that was blocked PPG and BCA, suggesting the importance of H₂S influences. The vasodilator effects of H₂S may require activation of smooth muscle cell membrane ATP-sensitive K⁺ (K_ATP) channels and large-conductance Ca²⁺-activated K⁺ (BK) channels. The K_ATP inhibitor glibenclamide and the BK inhibitor paxilline blocked CSE/H₂S-dependent dilation of pial arterioles to ET-1. In contrast, the vasoconstrictor response of pial arterioles to 10^-8 M ET-1 was not modulated by PPG, BCA, glibenclamide, or paxilline and, therefore, was independent of CSE/H₂S influences. Pial arteriolar constriction response to higher levels of ET-1 was independent of CSE/H₂S and K_ATP/BK_Ca channel activation. These data suggest that H₂S is an endothelium-derived factor that mediates the vasodilator effects of ET-1 in the cerebral circulation via a mechanism that involves activation of K_ATP and BK channels in vascular smooth muscle. NEW & NOTEWORTHY Disorders of the cerebral circulation in newborn infants may lead to lifelong neurological disabilities. We report that vasoactive peptide endothelin-1 exhibits vasodilator properties in the neonatal cerebral circulation by stimulating production of H₂S, an endothelium-derived messenger with vasodilator properties. The ability of endothelin-1 to stimulate brain production of H₂S may counteract the reduction in cerebral blood flow and prevent the cerebral vascular dysfunction caused by stroke, asphyxia, cerebral hypoxia, ischemia, and vasospasm.

CHST3 and CHST13 polymorphisms as predictors of bosentan-induced liver toxicity in Japanese patients with pulmonary arterial hypertension

Bosentan, an endothelin receptor antagonist, has been widely used as a first-line drug for the treatment of pulmonary arterial hypertension (PAH). In addition, bosentan is approved for patients with digital ulcers related to systemic sclerosis. Liver dysfunction is a major adverse effect of bosentan and may lead to discontinuation of therapy. The purpose of this study was to identify genomic biomarkers to predict bosentan-induced liver injury. A total of 69 PAH patients were recruited into the study. An exploratory analysis of 1936 single-nucleotide polymorphisms (SNPs) in 231 genes involved in absorption, distribution, metabolism, and elimination of multiple medications using Affimetrix DMET™ (Drug Metabolism Enzymes and Transporters) chips was performed. We extracted 16 SNPs (P <  0.05) using the Jonckheere-Terpstra trend test and multiplex logistic analysis; we identified two SNPs in two genes, CHST3 and CHST13, which are responsible for proteoglycan sulfation and were significantly associated with bosentan-induced liver injury. We constructed a predictive model for bosentan-induced liver injury (area under the curve [AUC]: 0.89, sensitivity: 82.61%, specificity: 86.05%) via receiver operating curve (ROC) analysis using 2 SNPs and 2 non-genetic factors. Two SNPs were identified as potential predictive markers for bosentan-induced liver injury in Japanese patients with pulmonary arterial hypertension. This is the first pharmacogenomics study linking proteoglycan sulfating genes to drug-induced liver dysfunction, a frequently observed clinical adverse effect of bosentan therapy. These results may provide a way to personalize PAH medicine as well as provide novel mechanistic insights to drug-induced liver dysfunction.

Vitamin D Upregulates Endothelin-1, ETBR, eNOS mRNA Expression and Attenuates Vascular Remodelling and Ischemia in Kidney Fibrosis Model in Mice Vitamin D Upregulates Endothelin-1, ETBR, eNOS mRNA Expression and Attenuates Vascular Remodelling and Ischemia in Kidney Fibrosis Model in Mice

We examined the upregulation of ET-1/ETBR/eNOS signaling in renoprotective effect of vitamin D in kidney fibrosis model in mice using unilateral ureteral obstruction (UUO). One group was treated with intraperitoneal injection of 0.125 mg/kg of Calcitriol (UUO+VD). Vascular remodeling was quantified based on lumen area and lumen/wall area ratio (LWAR) of intrarenal arteries using Sirius Red staining. ET-1, ETBR, eNOS, CD31 and VEGF mRNA expressions were quantified using qRT-PCR. Focusing on endothelin-1 (ET-1) signaling in endothelial cells (EC), siRNA of ET-1 was performed in human umbilical vein endothelial cells (HUVEC) for reducing ET-1 expression. Then HUVECs were treated with and without 100 nM Calcitriol treatment in hypoxic and normoxic conditions to elucidate ET-1/eNOS signaling. Our in vivo study revealed vascular remodeling and renal ischemia attenuation after Calcitriol treatment. Vascular remodeling was attenuated in the UUO+VD group as shown by increasing lumen areas and LWAR in intrarenal arteries. These findings were associated with significant higher CD31 and VEGF mRNA expression compared to the UUO group. Vitamin D treatment also increased ET-1, ETBR and eNOS mRNA expressions. Our in vitro study demonstrated Calcitriol induced ET-1 and eNOS mRNA expressions upregulation in HUVEC under normoxic and hypoxic condition. Meanwhile, siRNA for ET-1 inhibited the upregulation of eNOS mRNA expression after Calcitriol treatment. Vitamin D ameliorates kidney fibrosis through attenuating vascular remodeling and ischemia with upregulating ET-1/ETBR and eNOS expression.

Diagnosis, Evaluation and Treatment of Pulmonary Arterial Hypertension in Children

Pulmonary Hypertension (PH), the syndrome of elevated pressure in the pulmonary arteries, is associated with significant morbidity and mortality for affected children. PH is associated with a wide variety of potential underlying causes, including cardiac, pulmonary, hematologic and rheumatologic abnormalities. Regardless of the cause, for many patients the natural history of PH involves progressive elevation in pulmonary arterial resistance and pressure, right ventricular dysfunction, and eventually heart failure. In recent years, a number of pulmonary arterial hypertension (PAH)-targeted therapies have become available to reduce pulmonary artery pressure and improve outcome. A growing body of evidence in both the adult and pediatric literature demonstrates enhanced quality of life, functional status, and survival among treated patients. This review provides a description of select etiologies of PH seen in pediatrics and an update on the most recent data pertaining to evaluation and management of children with PH/PAH. The available evidence for specific classes of PAH-targeted therapies in pediatrics is additionally discussed.

The joint effect of the endothelin receptor B gene (EDNRB) polymorphism rs10507875 and nitric oxide synthase 3 gene (NOS3) polymorphism rs869109213 in Slovenian patients with type 2 diabetes mellitus and diabetic retinopathy

Increasing evidence suggests that endothelin and nitric oxide synthase genes and their products exert biological effects on the vasculature via the nitric oxide or endothelin pathway. The aim of the study was to evaluate the association of rs10507875 and rs869109213 (alone or in interaction) with diabetic retinopathy (DR) in subjects with type 2 diabetes mellitus (T2DM). We genotyped the single nucleotide polymorphism rs10507875 of the endothelin receptor B gene (EDNRB) and variable number tandem repeats rs869109213 of the nitric oxide synthase 3 gene (NOS3) in 270 Slovenian patients with DR and T2DM and 256 controls with T2DM without clinical signs of DR. The genotyping was performed using either real-time polymerase chain reaction (PCR) or standard PCR. We found a significant association between the genotypes of NOS3 rs869109213 polymorphism and the risk of DR in the co-dominant model (4a4b genotype; 1.99-fold increased risk [1.09-3.65]; 95% confidence interval [CI]; p = 0.02), co-dominant model (4a4a genotype; 4.16-fold increased risk [1.03-16.74]; 95% CI; p = 0.04), and dominant model (4a4a and 4a4b genotypes; 2.22-fold increased risk [1.26-3.92]; 95% CI; p = 0.01) compared to the 4b4b genotype. Moreover, the joint effect of the two polymorphisms on DR risk was greater than the individual effect of each polymorphism in the analyzed genetic models. Additionally, adjusted odds ratio showed an increased risk in dominant × dominant (4.15-fold [1.40-12.26]; 95% CI; p = 0.01) and recessive × dominant (2.24-fold [1.25-4.01]; 95% CI; p = 0.02) genotype combinations of the two polymorphisms. In conclusion, our results indicate that NOS3 rs869109213 polymorphism alone or in a combination with EDNRB rs10507875 polymorphism may be associated with DR in Slovenian patients with T2DM.

Origins, Technological Development, and Applications of Peptidomics

Peptidomics is the comprehensive characterization of peptides from biological sources mainly by HPLC and mass spectrometry. Mass spectrometry allows the detection of a multitude of single peptides in complex mixtures. The term first appeared in full papers in the year 2001, after over 100 years of peptide research with a main focus on one or a few specific peptides. Within the last 15 years, this new field has grown to over 1200 publications. Mass spectrometry techniques, in combination with other analytical methods, were developed for the fast and comprehensive analysis of peptides in proteomics and specifically adjusted to implement peptidomics technologies. Although peptidomics is closely linked to proteomics, there are fundamental differences with conventional bottom-up proteomics. The development of peptidomics is described, including the most important implementations for its technological basis. Different strategies are covered which are applied to several important applications, such as neuropeptidomics and discovery of bioactive peptides or biomarkers. This overview includes links to all other chapters in the book as well as recent developments of separation, mass spectrometric, and data processing technologies. Additionally, some new applications in food and plant peptidomics as well as immunopeptidomics are introduced.

Endothelin-1 activation in pediatric patients undergoing surgical coarctation of the aorta repair

AIM

To determine endothelin-1 (ET-1) concentration before and after surgical coarctectomy and evaluate its association with left ventricular geometric change.

METHODS

A prospective, cohort study of 24 patients aged 2 d to 10 years with coarctation of the aorta undergoing surgical repair. A sub-cohort of patients with age < 1 mo was classified as “neonates”. Echocardiograms were performed just prior to surgery and in the immediate post-op period to assess left ventricle mass index and relative wall thickness (RWT). Plasma ET-1 levels were assessed at both time points. Association between ET-1 levels and ventricular remodeling was assessed.

RESULTS

Patients < 1 year demonstrated higher pre-op ET-1 than post-op (2.8 pg/mL vs 1.9 pg/mL, P = 0.02). Conversely, patients > 1 year had no change in ET-1 concentration before and after surgery (1.1 vs 1.4, NS). Pre-op, patients < 1 year demonstrated significantly higher ET-1 than older children (2.8 vs 1.1, P = 0.001). Post-op there was no difference between the age groups (1.9 vs 1.4, NS). Neither RWT nor left ventricle mass index (LVMI) varied from pre-op to post-op. The subset of neonates showed a strong positive correlation between pre-op ET-1 and RWT (r = 0.92, P = 0.001). Patients with ET-1 > 2 pg/mL pre-op demonstrated higher LVMI (65.7 g/m^2.7vs 38.5 g/m^2.7, P = 0.004) and a trend towards higher RWT (45% vs 39%, P = 0.07) prior to repair than those with lower ET-1 concentration.

CONCLUSION

ET-1 concentration is significantly variable in the peri-operative period surrounding coarctectomy. Older children and infants have different responses to surgical repair suggesting different mechanisms of activation.

Intrarenal activation of endothelin type B receptors improves kidney oxygenation in type 1 diabetic rats

About one-third of patients with type 1 diabetes develops kidney disease. The mechanism is largely unknown, but intrarenal hypoxia has been proposed as a unifying mechanism for chronic kidney disease, including diabetic nephropathy. The endothelin system has recently been demonstrated to regulate oxygen availability in the diabetic kidney via a pathway involving endothelin type A receptors (ETA-R). These receptors mainly mediate vasoconstriction and tubular sodium retention, and inhibition of ETA-R improves intrarenal oxygenation in the diabetic kidney. Endothelin type B receptors (ETB-R) can induce vasodilation of the renal vasculature and also regulate tubular sodium handling. However, the role of ETB-R in kidney oxygen homeostasis is unknown. The effects of acute intrarenal ETB-R activation (sarafotoxin 6c for 30-40 min; 0.78 pmol/h directly into the renal artery) on kidney function and oxygen metabolism were investigated in normoglycemic controls and insulinopenic male Sprague-Dawley rats administered streptozotocin (55 mg/kg) 2 wk before the acute experiments. Intrarenal activation of ETB-R improved oxygenation in the hypoxic diabetic kidney. However, the effects on diabetes-induced increased kidney oxygen consumption could not explain the improved oxygenation. Rather, the improved kidney oxygenation was due to hemodynamic effects increasing oxygen delivery without increasing glomerular filtration or tubular sodium load. In conclusion, increased ETB-R signaling in the diabetic kidney improves intrarenal tissue oxygenation due to increased oxygen delivery secondary to increased renal blood flow.

Endothelin A receptor blocker and calcimimetic in the adenine rat model of chronic renal insufficiency

BACKGROUND

We studied whether endothelin receptor antagonist and calcimimetic treatments influence renal damage and kidney renin-angiotensin (RA) components in adenine-induced chronic renal insufficiency (CRI).

METHODS

Male Wistar rats (n = 80) were divided into 5 groups for 12 weeks: control (n = 12), 0.3% adenine (Ade; n = 20), Ade + 50 mg/kg/day sitaxentan (n = 16), Ade + 20 mg/kg/day cinacalcet (n = 16), and Ade + sitaxentan + cinacalcet (n = 16). Blood pressure (BP) was measured using tail-cuff, kidney histology was examined, and RA components measured using RT-qPCR.

RESULTS

Adenine caused tubulointerstitial damage with severe CRI, anemia, hyperphosphatemia, 1.8-fold increase in urinary calcium excretion, and 3.5-fold and 18-fold increases in plasma creatinine and PTH, respectively. Sitaxentan alleviated tubular atrophy, while sitaxentan + cinacalcet combination reduced interstitial inflammation, tubular dilatation and atrophy in adenine-rats. Adenine diet did not influence kidney angiotensin converting enzyme (ACE) and AT₄ receptor mRNA, but reduced mRNA of renin, AT_1a, AT₂, (pro)renin receptor and Mas to 40-60%, and suppressed ACE2 to 6% of that in controls. Sitaxentan reduced BP by 8 mmHg, creatinine, urea, and phosphate concentrations by 16-24%, and PTH by 42%. Cinacalcet did not influence BP or creatinine, but reduced PTH by 84%, and increased hemoglobin by 28% in adenine-rats. The treatments further reduced renin mRNA by 40%, while combined treatment normalized plasma PTH, urinary calcium, and increased ACE2 mRNA 2.5-fold versus the Ade group (p < 0.001).

CONCLUSIONS

In adenine-induced interstitial nephritis, sitaxentan improved renal function and tubular atrophy. Sitaxentan and cinacalcet reduced kidney renin mRNA by 40%, while their combination alleviated tubulointerstitial damage and urinary calcium loss, and increased kidney tissue ACE2 mRNA.

Bevacizumab-induced hypertension: Clinical presentation and molecular understanding

Bevacizumab is a vascular endothelial growth factor-A-specific angiogenesis inhibitor indicated as an adjunct to chemotherapy for the treatment of several types of cancer. Hypertension is commonly observed during bevacizumab treatment, and high-grade toxicity can limit therapy and lead to other cardiovascular complications. The factors that contribute to interindividual variability in blood pressure response to bevacizumab treatment are not well understood. In this review, we outline research efforts to understand the mechanisms and pathophysiology of hypertension resulting from bevacizumab treatment. Moreover, we highlight current knowledge of the pharmacogenetics of bevacizumab-induced hypertension, which may be used to develop strategies to prevent or minimize this toxicity.

Expression and functional implications of the renal apelinergic system in rodents

Apelin binds to the G protein-coupled apelin receptor (APJ; gene name aplnr) to modulate diverse physiological systems including cardiovascular function, and hydromineral and metabolic balance. Recently a second endogenous ligand for APJ, named apela, has been discovered. We confirm that apela activates signal transduction pathways (ERK activation) in cells expressing the cloned rat APJ. Previous studies suggest that exogenous apela is diuretic, attributable wholly or in part to an action on renal APJ. Thus far the cellular distribution of apela in the kidney has not been reported. We have utilized in situ hybridization histochemistry to reveal strong apela labelling in the inner medulla (IM), with lower levels observed in the inner stripe of the outer medulla (ISOM), of rat and mouse kidneys. This contrasts with renal aplnr expression where the converse is apparent, with intense labelling in the ISOM (consistent with vasa recta labelling) and low-moderate hybridization in the IM, in addition to labelling of glomeruli. Apelin is found in sparsely distributed cells amongst more prevalent aplnr-labelled cells in extra-tubular regions of the medulla. This expression profile is supported by RNA-Seq data that shows that apela, but not apelin or aplnr, is highly expressed in microdissected rat kidney tubules. If endogenous tubular apela promotes diuresis in the kidney it could conceivably do this by interacting with APJ in vasculature, or via an unknown receptor in the tubules. The comparative distribution of apela, apelin and aplnr in the rodent kidney lays the foundation for future work on how the renal apelinergic system interacts.

Association between Endothelin-1 Levels and Kidney Disease among Blacks

Endothelin-1, a marker of endothelial dysfunction, is a potent vasoconstrictor released by endothelial cells and an important regulator of renal physiology. It is not known whether elevated serum levels of endothelin-1 indicate future risk of kidney disease in the general population. In participants in the Jackson Heart Study, a community-based observational study of cardiovascular risk in black adults, we measured serum endothelin-1 level at baseline (2000-2004; n=3538). We defined incident CKD as eGFR<60 ml/min per 1.73 m² and ≥30% eGFR decline at the third visit (2009-2013) relative to baseline among those participants with baseline eGFR ≥60 ml/min per 1.73 m² At baseline, mean age was 55 years old, 37% of participants were men, and mean eGFR was 94 ml/min per 1.73 m² Over a median follow-up of 8 years, 228 (6.4%) cases of incident CKD occurred in participants. Participants with baseline endothelin-1 levels in higher quartiles had a greater incidence of CKD in the fully adjusted model (odds ratio for fourth versus first quartile, 1.81; 95% confidence interval, 1.11 to 2.96; P_trend=0.04). Endothelin-1 positively associated with all-cause mortality (hazard ratio for fourth versus first quartile, 1.64; 95% confidence interval, 1.24 to 2.16; P_trend<0.001). In conclusion, higher baseline serum endothelin-1 levels associated with incident CKD and all-cause mortality during follow-up in this general population sample of blacks.

Chronic hypoxia alters fetal cerebrovascular responses to endothelin-1

In utero hypoxia influences the structure and function of most fetal arteries, including those of the developing cerebral circulation. Whereas the signals that initiate this hypoxic remodeling remain uncertain, these appear to be distinct from the mechanisms that maintain the remodeled vascular state. The present study explores the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to endothelin-1 (ET-1), a potent vascular contractant and mitogen. In fetal lambs, chronic hypoxia (3,820-m altitude for the last 110 days of gestation) had no significant effect on plasma ET-1 levels or ETA receptor density in cerebral arteries but enhanced contractile responses to ET-1 in an ETA-dependent manner. In organ culture (24 h), 10 nM ET-1 increased medial thicknesses less in hypoxic than in normoxic arteries, and these increases were ablated by inhibition of PKC (chelerythrine) in both normoxic and hypoxic arteries but were attenuated by inhibition of CaMKII (KN93) and p38 (SB203580) in normoxic but not hypoxic arteries. As indicated by Ki-67 immunostaining, ET-1 increased medial thicknesses via hypertrophy. Measurements of colocalization between MLCK and SMαA revealed that organ culture with ET-1 also promoted contractile dedifferentiation in normoxic, but not hypoxic, arteries through mechanisms attenuated by inhibitors of PKC, CaMKII, and p38. These results support the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to ET-1 through pathways dependent upon PKC, CaMKII, and p38 that cause increased ET-1-mediated contractility, decreased ET-1-mediated smooth muscle hypertrophy, and a depressed ability of ET-1 to promote contractile dedifferentiation.

Effects of age and caloric restriction in the vascular response of renal arteries to endothelin-1 in rats

Cardiovascular alterations are the most prevalent cause of impaired physiological function in aged individuals with kidney being one the most affected organs. Aging-induced alterations in renal circulation are associated with a decrease in endothelium-derived relaxing factors such as nitric oxide (NO) and with an increase in contracting factors such as endothelin-1(ET-1). As caloric restriction (CR) exerts beneficial effects preventing some of the aging-induced alterations in cardiovascular system, the aim of this study was to analyze the effects of age and caloric restriction in the vascular response of renal arteries to ET-1 in aged rats. Vascular function was studied in renal arteries from 3-month-old Wistar rats fed ad libitum (3m) and in renal arteries from 8-and 24-month-old Wistar rats fed ad libitum (8m and 24m), or subjected to 20% caloric restriction during their three last months of life (8m-CR and 24m-CR). The contractile response to ET-1 was increased in renal arteries from 8m and 24m compared to 3m rats. ET-1-induced contraction was mediated by ET-A receptors in all experimental groups and also by ET-B receptors in 24m rats. Caloric restriction attenuated the increased contraction to ET-1 in renal arteries from 8m but not from 24m rats possibly through NO release proceeding from ET-B endothelial receptors. In 24m rats, CR did not attenuate the aging-increased response of renal arteries to ET-1, but it prevented the aging-induced increase in iNOS mRNA levels and the aging-induced decrease in eNOS mRNA levels in arterial tissue. In conclusion, aging is associated with an increased response to ET-1 in renal arteries that is prevented by CR in 8m but not in 24m rats.

Endothelin-1 Treatment Induces an Experimental Cerebral Malaria-Like Syndrome in C57BL/6 Mice Infected with Plasmodium berghei NK65

Plasmodium berghei ANKA infection of C57BL/6 mice is a widely used model of experimental cerebral malaria (ECM). By contrast, the nonneurotropic P. berghei NK65 (PbN) causes severe malarial disease in C57BL/6 mice but does not cause ECM. Previous studies suggest that endothelin-1 (ET-1) contributes to the pathogenesis of ECM. In this study, we characterize the role of ET-1 on ECM vascular dysfunction. Mice infected with 10⁶ PbN-parasitized red blood cells were treated with either ET-1 or saline from 2 to 8 days postinfection (dpi). Plasmodium berghei ANKA-infected mice served as the positive control. ET-1-treated PbN-infected mice exhibited neurological signs, hypothermia, and behavioral alterations characteristic of ECM, dying 4 to 8 dpi. Parasitemia was not affected by ET-1 treatment. Saline-treated PbN-infected mice did not display ECM, surviving until 12 dpi. ET-1-treated PbN-infected mice displayed leukocyte adhesion to the vascular endothelia and petechial hemorrhages throughout the brain at 6 dpi. Intravital microscopic images demonstrated significant brain arteriolar vessel constriction, decreased functional capillary density, and increased blood-brain barrier permeability. These alterations were not present in either ET-1-treated uninfected or saline-treated PbN-infected mice. In summary, ET-1 treatment of PbN-infected mice induced an ECM-like syndrome, causing brain vasoconstriction, adherence of activated leukocytes in the cerebral microvasculature, and blood-brain barrier leakage, indicating that ET-1 is involved in the genesis of brain microvascular alterations that are the hallmark of ECM.

Hyperinsulinemia augments endothelin-1 protein expression and impairs vasodilation of human skeletal muscle arterioles

Hyperinsulinemia is a hallmark of insulin resistance-associated metabolic disorders. Under physiological conditions, insulin maintains a balance between nitric oxide (NO) and, the potent vasoconstrictor, endothelin-1 (ET-1). We tested the hypothesis that acute hyperinsulinemia will preferentially augment ET-1 protein expression, disrupt the equilibrium between ET-1 expression and endothelial NO synthase (eNOS) activation, and subsequently impair flow-induced dilation (FID) in human skeletal muscle arterioles. Skeletal muscle biopsies were performed on 18 lean, healthy controls (LHCs) and 9 older, obese, type 2 diabetics (T2DM) before and during (120 min) a 40 mU/m2/min hyperinsulinemic-euglycemic (5 mmol/L) clamp. Skeletal muscle protein was analyzed for ET-1, eNOS, phosphorylated eNOS (p-eNOS), and ET-1 receptor type A (ETAR) and B (ETBR) expression. In a subset of T2DM (n = 6) and LHCs (n = 5), FID of isolated skeletal muscle arterioles was measured. Experimental hyperinsulinemia impaired FID (% of dilation at ∆60 pressure gradient) in LHCs (basal: 74.2 ± 2.0; insulin: 57.2 ± 3.3, P = 0.003) and T2DM (basal: 62.1 ± 3.6; insulin: 48.9 ± 3.6, P = 0.01). Hyperinsulinemia increased ET-1 protein expression in LHCs (0.63 ± 0.04) and T2DM (0.86 ± 0.06) compared to basal conditions (LHCs: 0.44 ± 0.05, P = 0.007; T2DM: 0.69 ± 0.06, P = 0.02). Insulin decreased p-eNOS (serine 1177) only in T2DM (basal: 0.28 ± 0.07; insulin: 0.17 ± 0.04, P = 0.03). In LHCs, hyperinsulinemia disturbed the balance between ETAR and ETBR receptors known to mediate vasoconstrictor and vasodilator actions of ET-1, respectively. Moreover, hyperinsulinemia markedly impaired plasma NO concentration in both LHCs and T2DM These data suggest that hyperinsulinemia disturbs the vasomotor balance in human skeletal muscle favoring vasoconstrictive pathways, eventually impairing arteriolar vasodilation.