Endothelin antagonists

Diabetic nephropathy: Focusing on pathological signals, clinical treatment, and dietary regulation

Diabetic nephropathy (DN) is one of the most severe complications of diabetes. However, due to its complex pathological mechanisms, no effective therapeutic methods (other than ACEIs and ARBs) have been applied, which have been used for many years in clinical practice. Recent studies have shown that emerging therapeutics, including novel target-based pharmacotherapy, cell therapies, and dietary regulation, are leading to new hopes for DN management. This review aims to shed new light on the treatment of DN by describing the important pathological mechanisms of DN and by analysing recent advances in clinical treatment, including drug therapy, cell therapy, and dietary regulation. In pathological mechanisms, RAAS activation, AGE accumulation, and EMT are involved in inflammation, cellular stress, apoptosis, pyroptosis, and autophagy. In pharmacotherapy, several new therapeutics, including SGLT2 inhibitors, GLP-1 agonists, and MRAs, are receiving public attention. In addition, stem cell therapies and dietary regulation are also being emphasized. Herein, we highlight the importance of combining therapy and dietary regulation in the treatment of DN and anticipate more basic research or clinical trials to verify novel strategies.

Application of ultrasound microbubble contrast to evaluate the effect of sitaxentan on renal microvascular perfusion in beagles undergoing cardiopulmonary bypass

BACKGROUND & OBJECTIVE

We aimed to evaluate the effect of sitaxentan on renal microvascular perfusion via application of ultrasound microbubble contrast.

METHODS

Male beagles were randomly divided into: Sham, cardiopulmonary bypass (CPB) and sitaxentan-infused (Sit) groups (n = 6). The ascending slope rate (ASR), area under the curve (AUC), derived peak intensity, and time to peak (TTP) were obtained via ultrasound microbubble contrast before CPB (T1), after 1 h CPB (T2), at end of CPB (T3), and 2 h after CPB (T4).

RESULTS

Compared with the Sham group, the CPB group had lower ASR of the renal cortex and medulla at T2 - 4, higher AUC and TTP at T3 - 4, and lower derived peak intensity at T4. The ASR at T2 - 4 in the Sit group was lower, TTP was higher at T2 - 4, and AUC was higher at T3 - 4 (P < 0.05). Compared with the CPB group, the Sit group had higher ASR of the renal cortex and medulla at T3 - 4 and AUC and TTP at T3 - 4 (P < 0.05). Compared with that at T1, the ASR of the renal cortex and medulla at T2 - 4 in the CPB group was lower, and AUC and TTP were higher at T3 - 4. The ASR of the renal cortex and medulla at T2 - 4 in the Sit group was lower, TTP was higher at T2 - 4, and AUC was higher at T4 (P < 0.05).

CONCLUSIONS

Ultrasound microbubble contrast could be effectively used to evaluate renal microvascular perfusion peri-CPB in beagles, which was prone to decrease and could be improved via pretreatment with sitaxentan.

Recent Advances in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a disease in which stenosis or obstruction of the pulmonary arteries (PAs) causes an increase in PA pressure, leading to right-sided heart failure and death. Basic research has revealed a decrease in the levels of endogenous vasodilators, such as prostacyclin, and an increase in the levels of endogenous vasoconstrictors, such as endothelin, in patients with PAH, leading to the development of therapeutic agents. Currently, therapeutic agents for PAH target three pathways that are selective for PAs: the prostacyclin, endothelin, and nitric oxide pathways. These treatments improve the prognosis of PAH patients. In this review, we introduce new drug therapies and provide an overview of the current therapeutic agents.

Endothelin-1 axes in the framework of predictive, preventive and personalised (3P) medicine

Endothelin-1 (ET-1) is involved in the regulation of a myriad of processes highly relevant for physical and mental well-being; female and male health; in the modulation of senses, pain, stress reactions and drug sensitivity as well as healing processes, amongst others. Shifted ET-1 homeostasis may influence and predict the development and progression of suboptimal health conditions, metabolic impairments with cascading complications, ageing and related pathologies, cardiovascular diseases, neurodegenerative pathologies, aggressive malignancies, modulating, therefore, individual outcomes of both non-communicable and infectious diseases such as COVID-19. This article provides an in-depth analysis of the involvement of ET-1 and related regulatory pathways in physiological and pathophysiological processes and estimates its capacity as a predictor of ageing and related pathologies,a sensor of lifestyle quality and progression of suboptimal health conditions to diseases for their targeted preventionand as a potent target for cost-effective treatments tailored to the person.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

Potassium (K+) channels in the pulmonary vasculature: Implications in pulmonary hypertension Physiological, pathophysiological and pharmacological regulation

The large K⁺ channel functional diversity in the pulmonary vasculature results from the multitude of genes expressed encoding K⁺ channels, alternative RNA splicing, the post-transcriptional modifications, the presence of homomeric or heteromeric assemblies of the pore-forming α-subunits and the existence of accessory β-subunits modulating the functional properties of the channel. K⁺ channels can also be regulated at multiple levels by different factors controlling channel activity, trafficking, recycling and degradation. The activity of these channels is the primary determinant of membrane potential (Em) in pulmonary artery smooth muscle cells (PASMC), providing an essential regulatory mechanism to dilate or contract pulmonary arteries (PA). K⁺ channels are also expressed in pulmonary artery endothelial cells (PAEC) where they control resting Em, Ca²⁺ entry and the production of different vasoactive factors. The activity of K⁺ channels is also important in regulating the population and phenotype of PASMC in the pulmonary vasculature, since they are involved in cell apoptosis, survival and proliferation. Notably, K⁺ channels play a major role in the development of pulmonary hypertension (PH). Impaired K⁺ channel activity in PH results from: 1) loss of function mutations, 2) downregulation of its expression, which involves transcription factors and microRNAs, or 3) decreased channel current as a result of increased vasoactive factors (e.g., hypoxia, 5-HT, endothelin-1 or thromboxane), exposure to drugs with channel-blocking properties, or by a reduction in factors that positively regulate K⁺ channel activity (e.g., NO and prostacyclin). Restoring K⁺ channel expression, its intracellular trafficking and the channel activity is an attractive therapeutic strategy in PH.

Management of Pulmonary Arterial Hypertension in the Pediatric Patient

PURPOSE OF REVIEW

Pediatric pulmonary arterial hypertension (PAH) is associated with significant morbidity and mortality. Herein we review the diagnosis and classification for pediatric PAH and detail the current therapeutic options available for use in the pediatric PAH population.

RECENT FINDINGS

Classification and treatment of pediatric PAH is guided by adult criteria and treatment algorithms, yet the distribution of factors contributing to PAH in children differs significantly from that seen in adults. It is necessary to understand these differences in order to appropriately tailor therapy to the needs of the child or adolescent. An expanding array of targeted PAH drugs are now approved for use in adults, and many of these drugs are used "off-label" to treat children and adolescents with PAH. Use of these novel therapies has coincided with marked improvement in outcomes, suggesting significant benefit. However, because most of these drugs have not been studied in rigorous randomized, controlled trials in children, it is critical that physicians understand their mechanisms of action, potential benefits, and safety profiles. Pediatric PAH outcomes have improved substantially in the modern era, coinciding with the "off-label" use of targeted PAH drugs in children and adolescents. Ideally, care should be provided at centers with specialized expertise in the diagnosis and treatment of pediatric PAH by providers who understand the appropriate diagnostic algorithms, classification schemes, and treatment approaches.

Potential functional and pathological side effects related to off-target pharmacological activity

Most pharmaceutical companies test their discovery-stage proprietary molecules in a battery of in vitro pharmacology assays to try to determine off-target interactions. During all phases of drug discovery and development, various questions arise regarding potential side effects associated with such off-target pharmacological activity. Here we present a scientific literature curation effort undertaken to determine and summarize the most likely functional and pathological outcomes associated with interactions at 70 receptors, enzymes, ion channels and transporters with established links to adverse effects. To that end, the scientific literature was reviewed using an on-line database, and the most commonly reported effects were summarized in tabular format. The resultant table should serve as a practical guide for research scientists and clinical investigators for the prediction and interpretation of adverse side effects associated with molecules interacting with components of this screening battery.

Comparative efficacy and acceptability of endothelin receptor antagonists for pulmonary arterial hypertension: A network meta-analysis

BACKGROUND

Endothelin receptor antagonists (ERAs) such as ambrisentan, sitaxsentan, bosentan and macitentan are primary drug therapies for pulmonary arterial hypertension (PAH) patients. However, the optimal drugs for PAH remained controversial due to heterogeneous nature of randomized control trials (RCTs).

METHODS

Apart from traditional meta-analysis, network meta-analysis (NMA) was performed in this study for multiple comparisons among PAH therapies. The 6 minute walking distance (6MWD) and clinical worsening were efficacy outcomes whereas serious adverse effects (SAE) and all-cause discontinuation were acceptability outcomes. The weighted mean difference (WMD) and odds ratio (OR) along with their 95% confidence interval (95% CI) or 95% credible interval (95% CrI) were used to evaluate the positive and negative effects of these therapies on PAH patients.

RESULTS

By synthesizing direct evidence from 10 studies with a total number of 2172 patients, we discovered that all of the four PAH therapies significantly increased the average 6MWD in comparison to the placebo (P-value<0.05). Moreover, bosentan and ambrisentan both showed significant association with a decrease in the risk of clinical worsening compared to placebo. Regarding of all-cause discontinuation, ambrisentan is the only therapy which was significantly associated with a risk decrease compared to placebo. However, there was no sufficient evidence suggesting significant difference in any efficacy or acceptability outcomes between any two of the PAH therapies (P-value>0.05).

CONCLUSION

Ambrisentan could be considered as the most appropriate therapy among the four ERAs for PAH patients. Bosentan also behaved well, but it is not as safe as ambrisentan.

A review of therapeutic agents for the management of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an uncommon, progressive and life threatening disease characterized by a proliferative vasculopathy of the small muscular pulmonary arterioles resulting in elevated pulmonary vascular resistance and eventually right ventricular failure. An increasing understanding of the pathobiology of PAH and its natural history has led to the development of numerous targeted therapies. Despite these advances there is significant progression of disease and the survival rate remains low. This article reviews the agents currently available for the medical management of PAH.

Portopulmonary hypertension

Portopulmonary hypertension (PoPH) refers to the condition that pulmonary arterial hypertension (PAH) occur in the stetting of portal hypertension. The development of PoPH is thought to be independent of the severity of portal hypertension or the etiology or severity of liver disease. PoPH results from excessive vasoconstriction, vascular remodeling, and proliferative and thrombotic events within the pulmonary circulation that lead to progressive right ventricular failure and ultimately to death. Untreated PoPH is associated with a poor prognosis. As PoPH is frequently asymptomatic or symptoms are generally non-specific, patients should be actively screened for the presence of PoPH. Two-dimensional transthoracic echocardiography is a useful non-invasive screening tool, but a definitive diagnosis requires invasive hemodynamic confirmation by right heart catheterization. Despite a dearth of randomized, prospective data, an ever-expanding clinical experience shows that patients with PoPH benefit from therapy with PAH-specific medications including with endothelin receptor antagonists, phosphodiesterase-5 inhibitors, and/or prostanoids. Due to high perioperative mortality, transplantation should be avoided in those patients who have severe PoPH that is refractory to medical therapy.

Emerging drugs for preeclampsia--the endothelium as a target

Preeclampsia, the development of new onset hypertension and proteinuria during pregnancy, affects ∼ 3 - 8% of all pregnancies and is a leading cause of maternal and perinatal morbidity and mortality. Despite the potentially devastating effects of this disease on the mother and the baby and the recent advances in understanding some of the pathological mechanisms responsible for the progression of preeclampsia, there are still few therapies available to manage the disease. The maternal syndrome of preeclampsia is characterized by systemic endothelial dysfunction; therefore, agents that improve endothelial function may hold promise to alleviate the symptoms of preeclampsia, delay the necessity for preterm delivery and improve neonatal outcomes. This brief review will focus on two therapies that are already approved for use in the US for other indications: PDE-5 inhibition to preserve nitric oxide - cGMP signaling to promote vasodilation and inhibition of the endothelin type A receptor to reduce vascular contraction.

Pharmacokinetic-pharmacodynamic relationships of macitentan, a new endothelin receptor antagonist, after multiple dosing in healthy Korean subjects

BACKGROUND AND OBJECTIVES

Macitentan is a novel dual endothelin (ET)-1 receptor antagonist to be used in patients with pulmonary arterial hypertension. This study aimed to assess the pharmacokinetics (PK) and pharmacodynamics (PD) of macitentan after administration of multiple doses to healthy Korean male subjects.

METHODS

A randomized, double-blind, placebo-controlled, multiple-ascending dose study was performed in 30 healthy male subjects receiving oral macitentan (3, 10, or 30 mg) or placebo once daily for 10 days. Plasma concentrations of macitentan, its active metabolite ACT-13277, and ET-1 were evaluated. Safety and tolerability measurements were conducted throughout the study.

RESULTS

The concentration-time profile of macitentan was characterized by slow absorption (median time to maximum plasma concentration [t(max)] 9-10 h) and slow elimination (mean elimination half-life [t ½] 11-15 h). After repeated doses of 3, 10, and 30 mg of macitentan over the course of 10 days, the peak concentration (C(max)) increased as the dose increased and the area under the plasma concentration-time curve during the dosing interval (AUC(τ)) increased in a dose-proportional manner. Plasma concentrations showed approximately 1.5- to 1.9-fold accumulation on day 10 compared with day 1. ACT-132577 showed higher levels of exposure than macitentan, its mean half-life was 46-48 h, and it accumulated 7- to 12-fold. Macitentan increased plasma ET-1 concentrations at all doses tested and was well tolerated and elicited no serious adverse events.

CONCLUSION

Multiple oral doses of 3, 10, and 30 mg of macitentan were well tolerated in healthy Korean subjects, and its pharmacokinetics correlated positively with ET-1 concentrations.

Acute hemodynamic response of infused fasudil in patients with pulmonary arterial hypertension: a randomized, controlled, crossover study

BACKGROUND

The Rho-kinase pathway has been shown to be involved in the pathogenesis of PAH. As yet, however, the acute effects of the Rho-kinase inhibitor fasudil have not been compared with established pulmonary selective vasodilators in patients with PAH. We compared the acute effects of intravenous fasudil with inhaled iloprost in patients with pulmonary arterial hypertension (PAH).

METHODS

Using a crossover design, 50 patients with PAH (idiopathic PAH, PAH associated with repaired left-to-right cardiac shunts, or connective tissue disease) were randomized to iloprost inhalation (5 μg) and intravenous fasudil (30 mg over 30 min). Hemodynamic data were collected at baseline and during acute drug exposure.

RESULTS

Comparable decreases were observed in mean pulmonary artery pressure (-4.6 ± 4.3 mmHg vs. -4.8 ± 4.2 mmHg) and pulmonary vascular resistance (-3.0 ± 3.0 Wood U vs. -2.2 ± 2.7 Wood U) with fasudil infusion and iloprost inhalation, respectively, during acute challenge. However, fasudil infusion resulted in a more pronounced increase in mean cardiac output and mixed venous oxygen saturation compared with iloprost inhalation (13.7 ± 17.1% vs. 6.9 ± 15.0%; p=0.044 and 4.5 ± 5.3% vs. 2.7 ± 8.2%; p=0.044, respectively). Whereas inhaled iloprost resulted in a non-significant increase in mean systemic arterial oxygen saturation (0.8 ± 3.6%), infused fasudil resulted in a non-significant reduction (-0.6 ± 1.1%).

CONCLUSION

Infused fasudil improved pulmonary hemodynamics in patients with PAH without significant toxicity.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Medical and surgical management for pulmonary arterial hypertension

Prior to the availability of the pulmonary arterial hypertension (PAH)-specific therapy, PAH was a dreadful disease with a very poor prognosis. Better understanding of the complex pathobiology of PAH has led to a major therapeutic evolution. International regulatory agencies have approved many specific drugs with different pharmacologic pathways and routes of administration. In the year 2013, two new drugs with great potentials in managing PAH have been added to the treatment options, macitentan and riociguat. Additional drugs are expected to come in the near future.

A substantial body of evidence has confirmed the effectiveness of pulmonary arterial hypertension (PAH)-specific therapies in improving the patients’ symptomatic status and slowing down the rate of clinical deterioration.

Although the newer modern medications have significantly improved the survival of patients with PAH, it remains a non-curable and fatal disease. Lung transplantation (LT) remains the only therapeutic option for selected patients with advanced disease who continue to deteriorate despite optimal therapy.

Interplay between endothelin and erythropoietin in astroglia: the role in protection against hypoxia

We show that, under in vitro conditions, the vulnerability of astroglia to hypoxia is reflected by alterations in endothelin (ET)-1 release and capacity of erythropoietin (EPO) to regulate ET-1 levels. Exposure of cells to 24 h hypoxia did not induce changes in ET-1 release, while 48–72 h hypoxia resulted in increase of ET-1 release from astrocytes that could be abolished by EPO. The endothelin receptor type A (ETA) antagonist BQ123 increased extracellular levels of ET-1 in human fetal astroglial cell line (SV-FHAS). The survival and proliferation of rat primary astrocytes, neural precursors, and neurons upon hypoxic conditions were increased upon administration of BQ123. Hypoxic injury and aging affected the interaction between the EPO and ET systems. Under hypoxia EPO decreased ET-1 release from astrocytes, while ETA receptor blockade enhanced the expression of EPO mRNA and EPO receptor in culture-aged rat astroglia. The blockade of ETA receptor can increase the availability of ET-1 to the ETB receptor and can potentiate the neuroprotective effects of EPO. Thus, the new therapeutic use of combined administration of EPO and ETA receptor antagonists during hypoxia-associated neurodegenerative disorders of the central nervous system (CNS) can be suggested.

The protective effects of endothelin-A receptor antagonist BQ-123 in pentylenetetrazole-induced seizure in rats

Endothelin-1 has been shown to increase neuronal activity and glutaminergic synaptic transmission by endothelin-A receptors (ETAR) in the nucleus tractus solitarius neurons that play an important role in epileptic seizures. Therefore, BQ-123 as an ETAR antagonist might attenuate neuronal excitability and glutaminergic synaptic transmission. The main purpose of the present study is to investigate the protective effect of acute BQ-123 treatment against pentylenetetrazole (PTZ)-induced tonic–clonic seizures. Wistar albino rats were divided into three groups: control, PTZ, and PTZ + BQ-123 groups. BQ-123 (3 mg/kg, intravenously) was administered for 15 min before injecting with PTZ (50 mg/kg, intraperitoneally). We determined a delay resulting from BQ-123 in “duration of the seizure onset.” “Number of rats with major seizure” also decreased according to scoring with video camera in PTZ + BQ-123 group. In BQ-123-treated group, there were eight rats without a major seizure, but only one rat had a delayed major seizure. The brain tissue glutathione peroxidase activity was significantly decreased in the PTZ and PTZ + BQ-123 groups. According to the results of the control group, there was a significant increase in the protein carbonyl levels of the PTZ group and a significant increase in the nitric oxide levels of the PTZ + BQ-123 group. Histological examination showed an increase in the number of neuronal hyperchromatic nucleus especially in hippocampal gyrus dentatus region of BQ-123-treated group. We concluded that BQ-123 impeded the formation and spread of seizure to a great degree. The beneficial effects of BQ-123 were comparatively supported with biochemical parameters and histological examinations.

Endothelin-1 and the kidney--beyond BP

Since its discovery over 20 years ago endothelin-1 (ET-1) has been implicated in a number of physiological and pathophysiological processes. Its role in the development and progression of chronic kidney disease (CKD) is well established and is an area of ongoing intense research. There are now available a number of ET receptor antagonists many of which have been used in trials with CKD patients and shown to reduce BP and proteinuria. However, ET-1 has a number of BP-independent effects. Importantly, and in relation to the kidney, ET-1 has clear roles to play in cell proliferation, podocyte dysfunction, inflammation and fibrosis, and arguably, these actions of ET-1 may be more significant in the progression of CKD than its prohypertensive actions. This review will focus on the potential role of ET-1 in renal disease with an emphasis on its BP-independent actions.

Sex and gender differences in cardiovascular drug therapy

This chapter outlines sex differences in pharmacokinetics and pharmacodynamics of the most frequently used drugs in cardiovascular diseases, e.g., coronary artery disease, hypertension, heart failure. Retrospective analysis of previously published drug trials revealed marked sex differences in efficacy and adverse effects in a number of cardiovascular drugs. This includes a higher mortality among women taking digoxin for heart failure, more torsade de pointes arrhythmia in QT prolonging drugs and more cough with ACE inhibitors. Trends towards a greater benefit for women and/or female animals have been observed in some studies for endothelin receptor antagonists, the calcium channel blocker amlodipine, the ACE-inhibitor ramipril and the aldosterone antagonist eplerenone. However, reproduction of these results in independent studies and solid statistical evidence is still lacking. Some drugs require a particularly careful dose adaptation in women: the beta-blocker metoprolol, the calcium channel blocker verapamil, loop-, and thiazide diuretics. In conclusion, sex differences in pharmacokinetics and pharmacodynamics have to be taken into account for cardiovascular drug therapy in women.

Cyclic guanosine monophosphate signalling pathway in pulmonary arterial hypertension

During the last decade, it emerged that cyclic guanosine monophosphate (cGMP) is a novel drug target for the treatment of pulmonary arterial hypertension (PAH). cGMP regulates many cellular functions, ranging from contractility to growth, of relevance to the disease. Generated from guanylyl cyclases in response to natriuretic peptides or nitric oxide (NO), cGMP transduces its effects through a number of cGMP effectors, including cGMP-regulated phosphodiesterases and protein kinases. Furthermore, the cGMP concentration is modulated by cGMP-degrading phosphodiesterases. Data to date demonstrate that increasing intracellular cGMP through stimulation of GCs, inhibition of PDEs, or both is a valid therapeutic strategy in drug development for PAH. New advances in understanding of cGMP are unravelled, as well as the pathobiology of PAH. cGMP remains an attractive future PAH drug target. This review makes a more detailed examination of cGMP signalling with particular reference to PAH.

Estimation of endothelin-mediated vasoconstriction in acute pulmonary thromboembolism

We aimed to investigate the role of endothelin-mediated vasoconstriction following acute pulmonary thromboembolism (APTE). Thirteen anesthetized piglets (~25 kg) were ventilated with 0 PEEP. Cardiac output (Qt) and wedge pressure (Pw) were measured by a Swan Ganz catheter, along with arterial and venous blood gases. APTE was induced by autologous blood clots (~0.8 g/kg, 12-16 pieces) via a jugular venous catheter at time = 0 minutes until the mean pulmonary arterial pressure (Ppa) was about 2.5 times the baseline at 30 minutes. Eight control animals (Group 1) received only normal saline afterward, while the remaining five (Group 2) received at time = 40-minute saline plus Tezosentan, a nonspecific endothelin antagonist. The drug was initially given as an intravenous bolus (10 mg/kg), followed by an infusion (2 mg/min) until the end of the experiment at 2 hours. Hemodynamic data were measured before APTE and then at 30-minute intervals. Pulmonary vascular resistance index (PVRI) was calculated as (Ppa-Pw)/CI, where CI was cardiac index or Qt/W (body weight). Fluorescent microspheres (FMS) were used to mark regional blood flows and ventilation for cluster analysis. PVRI acutely increased within minutes and remained high despite some recovery over time. With Tezosentan treatment, the results showed that endothelin-mediated vasoconstriction persisted significantly up to 2 hours and accounted for about 25% of the increase in PVRI while clot obstruction accounted for the remaining 75%. CI remained relatively constant throughout. Tezosentan also affected PVRI indirectly by mitigating the shift of regional blood flow back to the embolized areas over time, possibly by attenuating vasoconstriction in the nonembolized areas. We conclude that following APTE, although the increased PVRI is mostly due to mechanical embolic obstruction, secondary factors such as vasoconstriction and pattern of regional blood flow over time also play important roles.

Endothelin receptor antagonists for the treatment of pulmonary artery hypertension

AIMS

The demonstration that endothelin production is upregulated in pulmonary artery hypertension (PAH) served as the rationale for developing endothelin-receptor antagonists (ERAs) as a treatment for PAH. This article reviews the primary studies demonstrating efficacy of ERAs in PAH.

MAIN METHODS

Multicenter, placebo-controlled trials and open-label extension studies.

KEY FINDINGS

Two orally active ERAs are currently approved for the treatment of PAH - the dual receptor antagonist bosentan, and the more selective ET(A) receptor antagonist ambrisentan-based on multicenter randomized clinical trials demonstrating efficacy and safety. Long-term experience with both agents supports maintenance of therapeutic effects in most patients. Adverse effects, including altered liver function and edema may occur and require careful monitoring.

SIGNIFICANCE

Despite failure to demonstrate efficacy of ERAs in other cardiopulmonary conditions, ERAs have a major role in the treatment algorithm for PAH.

New options and perspectives for proteinuria management after kidney transplantation

Proteinuria has been strongly correlated with reduced function and graft survival in kidney-transplanted patients. Data regarding new strategies in proteinuria treatment and subsequent allograft survival are lacking. Similarities between chronic graft injury and chronic kidney disease (CKD) suggest that the same therapeutic antiproteinuric tools should be effective in kidney-transplanted patients. The classic strategies to decrease proteinuria such as blood pressure control, nicotine cessation, low-salt diet, and maintaining an ideal body weight seem to be not enough to achieve proteinuria control. Improvements in our understanding of the pathogenesis of CKD have led to the identification of several novel targets for proteinuria management. In this review, we discuss novel pharmacological approaches that aim to decrease proteinuria in CKD patients, including the use of direct renin inhibitors, vitamin D analogs, pentoxifylline, and endothelin receptor antagonists. We also discuss the promise of using antifibrotic agents to treat proteinuria. The identification of new biomarkers of CKD and its progression can help in the selection of the most effective treatment for decreasing proteinuria and maintaining kidney function.

Pulmonary hypertension-"state of the art" management in 2012

Pulmonary artery hypertension (PAH) is a pathological condition of small pulmonary arteries, characterised by vascular proliferation and remodelling. The pulmonary artery pressure and pulmonary vascular resistance progressively rise, leading to right heart failure and death. Pulmonary artery hypertension may be secondary to various conditions, or it may be idiopathic where no underlying cause is identifiable. Earlier, only symptomatic treatment was available for such patients which did not change the natural history of the disease. However, over the years, improvement in understanding the pathogenesis has resulted in the development of targeted approaches to the treatment of PAH. Survival advantage has also been shown with some of the pharmacologic agents. This review article discusses the current management strategy for PAH with special emphasis on an idiopathic variety, in an Indian context.

Lactoferrin-endothelin-1 axis contributes to the development and invasiveness of triple-negative breast cancer phenotypes

Triple-negative breast cancer (TNBC) is characterized by the lack of expression of estrogen receptor-α (ER-α), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2). However, pathways responsible for downregulation of therapeutic receptors, as well as subsequent aggressiveness, remain unknown. In this study, we discovered that lactoferrin (Lf) efficiently downregulates levels of ER-α, PR, and HER-2 in a proteasome-dependent manner in breast cancer cells, and it accounts for the loss of responsiveness to ER- or HER-2-targeted therapies. Furthermore, we found that lactoferrin increases migration and invasiveness of both non-TNBC and TNBC cell lines. We discovered that lactoferrin directly stimulates the transcription of endothelin-1 (ET-1), a secreted proinvasive polypeptide that acts through a specific receptor, ET(A)R, leading to secretion of the bioactive ET-1 peptide. Interestingly, a therapeutic ET-1 receptor-antagonist blocked lactoferrin-dependent motility and invasiveness of breast cancer cells. The physiologic significance of this newly discovered Lf-ET-1 axis in the manifestation of TNBC phenotypes is revealed by elevated plasma and tissue lactoferrin and ET-1 levels in patients with TNBC compared with those in ER(+) cases. These findings describe the first physiologically relevant polypeptide as a functional determinant in downregulating all three therapeutic receptors in breast cancer, which uses another secreted ET-1 system to confer invasiveness. Results presented in this article provide proof-of-principle evidence in support of the therapeutic effectiveness of ET-1 receptor antagonist to completely block the lactoferrin-induced motility and invasiveness of the TNBC as well as non-TNBC cells, and thus, open a remarkable opportunity to treat TNBC by targeting the Lf-ET-1 axis using an approved developmental drug.

Endothelium-derived NO, but not cyclic GMP, is required for hypoxic augmentation in isolated porcine coronary arteries

The present study investigated the mechanism underlying the transient potentiation of vasoconstriction by hypoxia in isolated porcine coronary arteries. Isometric tension was measured in rings with or without endothelium. Hypoxia (Po(2) <30 mmHg) caused a transient further increase in tension (hypoxic augmentation) in contracted (with U46619) preparations. The hypoxic response was endothelium dependent and abolished by inhibitors of nitric oxide synthase [N(ω)-nitro-L-arginine methyl ester (L-NAME)] or soluble guanylyl cyclase (ODQ and NS2028). The addition of DETA NONOate (nitric oxide donor) in the presence of L-NAME restored the hypoxic augmentation, suggesting the involvement of the nitric oxide pathway. However, the same was not observed after incubation with 8-bromo-cyclic GMP, atrial natriuretic peptide, or isoproterenol. Assay of the cyclic GMP content showed no change upon exposure to hypoxia in preparations with and without endothelium. Incubation with protein kinase G and protein kinase A inhibitors did not inhibit the hypoxic augmentation. Thus the hypoxic augmentation is dependent on nitric oxide and soluble guanylyl cyclase but independent of cyclic GMP. The hypoxic augmentation persisted in calcium-free buffer and in the presence of nifedipine, ruling out a role for extracellular calcium influx. Hypoxia did not alter the intracellular calcium concentration, as measured by confocal fluorescence microscopy. This observation and the findings that hypoxic augmentation is enhanced by thapsigargin (sarco/endoplasmic reticulum calcium ATPase inhibitor) and inhibited by HA1077 or Y27632 (Rho kinase inhibitors) demonstrate the involvement of calcium sensitization in the phenomenon.

Race and sex differences in response to endothelin receptor antagonists for pulmonary arterial hypertension

BACKGROUND

Recently studied therapies for pulmonary arterial hypertension (PAH) have improved outcomes among populations of patients, but little is known about which patients are most likely to respond to specific treatments. Differences in endothelin-1 biology between sexes and between whites and blacks may lead to differences in patients' responses to treatment with endothelin receptor antagonists (ERAs).

METHODS

We conducted pooled analyses of deidentified, patient-level data from six randomized placebo-controlled trials of ERAs submitted to the US Food and Drug Administration to elucidate heterogeneity in treatment response. We estimated the interaction between treatment assignment (ERA vs placebo) and sex and between treatment and white or black race in terms of the change in 6-min walk distance from baseline to 12 weeks.

RESULTS

Trials included 1,130 participants with a mean age of 49 years; 21% were men, 74% were white, and 6% were black. The placebo-adjusted response to ERAs was 29.7 m (95% CI, 3.7-55.7 m) greater in women than in men (P = .03). The placebo-adjusted response was 42.2 m for whites and -1.4 m for blacks, a difference of 43.6 m (95% CI, -3.5-90.7 m) (P = .07). Similar results were found in sensitivity analyses and in secondary analyses using the outcome of absolute distance walked.

CONCLUSIONS

Women with PAH obtain greater responses to ERAs than do men, and whites may experience a greater treatment benefit than do blacks. This heterogeneity in treatment-response may reflect pathophysiologic differences between sexes and races or distinct disease phenotypes.

Endothelin antagonism as an active principle for glaucoma therapy

Endothelin, the most potent vasoactive peptide known to date, has been suggested to play a potential role in the pathogenesis of open-angle glaucoma. Open-angle glaucoma is the most common optic nerve head neuropathy and is associated with a loss of retinal ganglion cells and visual field damage. Although an increased intraocular pressure is a major risk factor for glaucomatous optic neuropathy, other factors such as a reduced ocular blood flow play an important role for appearance of the disease. Thus, treatment of glaucoma is focused on lowering of intraocular pressure and preventing the occurrence or progression of glaucomatous optic neuropathy. Endothelin participates in the regulation of intraocular pressure by an effect on trabecular outflow, the main route for aqueous humour outflow from the eye. Trabecular outflow is modulated by trabecular meshwork contractility which is affected by endothelin. In addition to the effects of endothelin in the anterior part of the eye, the vasoconstrictor causes a decrease in ocular blood flow followed by pathological changes in the retina and the optic nerve head which is assumed to contribute to the degeneration of retinal ganglion cells. In sum, inhibition of endothelin signalling leads to lowering of intraocular pressure and exerts neuroprotective effects. Thus, endothelin antagonism in the eye represents a promising approach for pharmacological treatment of glaucoma.

Pulmonary arterial hypertension: pathobiology, diagnosis, treatment, and emerging therapies

Pulmonary hypertension is a rare disorder caused by vasoconstriction of the pulmonary arteries that leads to elevation of pulmonary vascular resistance, right ventricular failure, and ultimately death. Hypertrophy and proliferation of the pulmonary vascular endothelium leads to remodeling of this vascular system, resulting in a progressive disorder. In the past decade the molecular mechanisms and pathobiology of this disorder has become clearer. In addition, a host of new medical treatments and therapies are now available for what has been previously known to be a devastating disorder. Although much needs to be learned, this review will discuss our current knowledge, results of clinical trials, along with treatment options and emerging therapies available for the treatment of this disorder.

Cardiorenal Syndrome: The Clinical Cardiologists' Perspective

The term cardiorenal syndrome has evolved over the years. The understanding of the interactions between these two organ systems has led to better recognition and treatment strategies. As cardiovascular mortality is high in individuals with renal dysfunction, it is imperative to understand the pathophysiology behind the disease process. This knowledge may better serve these patients with this syndrome and improve their outcomes. In this review, we examine the key issues of the cardiorenal syndrome from a cardiologist's perspective.

Sitaxsentan for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening, progressive condition that eventually leads to right heart failure. Endothelin receptor antagonists (ETRAs) have been shown to be a safe and efficacious treatment for PAH. Sitaxsentan is a highly selective oral ETRA that, in clinical trials, has demonstrated significant improvements in exercise capacity, functional class and pulmonary hemodynamics in PAH. Sitaxsentan has been shown to be a well tolerated and effective agent with a durable response for the treatment of PAH, and is associated with a low incidence of liver toxicity.

Endothelin--biology and disease

Endothelins are important mediators of physiological and pathophysiologic processes including cardiovascular disorders, pulmonary disease, renal diseases and many others. Additionally, endothelins are involved in many other important processes such as development, cancer biology, wound healing, and even neurotransmission. Here, we review the cell and molecular biology as well as the prominent pathophysiological aspects of the endothelin system.

Working under pressure: coronary arteries and the endothelin system

Endogenous endothelin-1-dependent (ET-1) tone in coronary arteries depends on the balance between ET(A) and ET(B) receptor-mediated effects and on parameters such as receptor distribution and endothelial integrity. Numerous studies highlight the striking functional interactions that exist between nitric oxide (NO) and ET-1 in the regulation of vascular tone. Many of the cardiovascular complications associated with cardiovascular risk factors and aging are initially attributable, at least in part, to endothelial dysfunction characterized by a dysregulation between NO and ET-1. The contribution of the imbalance between smooth muscle ET(A/B) and endothelial ET(B) receptors to this process is poorly understood. An increased contribution of ET-1 that is associated with a proportional decrease in that of NO accompanies the development of coronary endothelial dysfunction, coronary vasospasm, and atherosclerosis. These data form the basis for the rationale of testing therapeutic approaches counteracting ET-1-induced cardiovascular dysfunction. It remains to be determined whether the beneficial role of endothelial ET(B) receptors declines with age and risk factors for cardiovascular diseases, revealing smooth muscle ET(B) receptors with proconstricting and proinflammatory activities.

Increased tissue endothelin-1 and endothelin-B receptor expression in temporal arteries from patients with giant cell arteritis

PURPOSE

Endothelin (ET)-1 has been implicated in the atherosclerotic process and during inflammation. Similarity in the development process of giant cell arteritis (GCA) and atherosclerosis exists. Several ET receptor antagonists have been developed, principally to target cardiovascular disease states. High doses of corticosteroids currently are used in the treatment of GCA, whereas other treatments are not as reliably effective. The present study was performed to elucidate the role for ET-1, ET(A), and ET(B) receptors in GCA.

DESIGN

Experimental, retrospective immunohistochemical study of temporal arteries using archival formalin-fixed, paraffin-embedded tissue.

PARTICIPANTS

The study included 10 patients with GCA and 10 control patients with clinically suspected GCA but diagnosed not to have GCA.

METHODS

Immunohistochemistry, with anti ET-1, anti-ET(A), and anti-ET(B) antibodies, was performed on formalin-fixed and paraffin-embedded temporal arteries.

MAIN OUTCOME MEASURES

Endothelin-1, ET(A), and ET(B) receptor immunostaining intensities were quantified.

RESULTS

Temporal arteries from the patients with GCA showed the typical histologic features, including intimal thickening, disruption or loss of the elastic lamina, and inflammatory infiltrates of lymphocytes, macrophages, and multinucleated giant cells. These features were associated with increased ET-1 and ET(B) receptor immunoreactivity in the medial layer of the temporal arteries and endothelial cells in patients with GCA compared with the controls. The increased ET-1 and ET(B) receptor immunoreactivity occurred in vascular smooth muscle cells (SMCs) and multinucleated giant cells. The ET-1 and ET(B) receptor immunoreactivity correlated with the degree of systemic inflammation. No changes were observed in ET(A) receptor expression in SMCs or endothelial cells compared with controls.

CONCLUSIONS

The results suggest a role for ET-1 and ET(B) receptors in GCA. Inhibiting the ET system may provide a corticosteroid-sparing alternative in the treatment of GCA.

Acute renal failure and hepatitis following ingestion of carp gallbladder

INTRODUCTION

Fish gallbladder has long been used as folk remedy in China. Poisoning due to carp gallbladder ingestion has been reported in many countries but the majority of cases are in Chinese journals. We report a case of grass carp gallbladder poisoning and review the literature, including the Chinese reports.

CASE REPORT

A 67 year old woman ingested a grass carp gallbladder and complained of nausea and epigastric pain in two hours, and had elevated alanine aminotransferase by 8 hours. She developed oliguria on day three and hemodialysis was performed on day five, following which she gradually recovered and was discharged on day 26.

DISCUSSION

Carp gallbladder contains 5 alpha-cyprinol sulphate, which is hepatotoxic and nephrotoxic. The exact mechanism of toxicity is unknown. Mild poisoning causes only gastroenteritis, liver and kidneys are affected in moderate poisoning, and multi-organ failure occurs in severe poisoning. The initial symptoms are nausea, vomiting, diarrhea and abdominal pain, which usually occur 5 to 12 hours after ingestion. Raised liver enzymes or jaundice occurs in 75% to 87% of patients. Acute renal impairment occurs in 72% to 87% of patients, usually on day 3 to 6. Treatment is supportive and often included hemodialysis.

CONCLUSION

The ingestion of grass carp gallbladder may result in transient hepatitis with subsequent acute renal failure. This case also illustrated the importance of understanding the use and potential serious complications of alternative medicines. Fish gallbladder poisoning should be considered in unexplained acute renal failure in Chinese and Asian patients.

Improved myocardial protection in the failing heart by selective endothelin-A receptor blockade

OBJECTIVE

Ischemia/reperfusion injury caused by cardioplegic arrest is still a major challenge in patients with reduced left ventricular function. We investigated the effect of chronic versus acute administration of the selective endothelin-A receptor antagonist (ERA) TBC-3214Na during ischemia/reperfusion in failing hearts.

METHODS

Male Sprague-Dawley rats underwent coronary ligation. Three days after myocardial infarction (MI), 19 randomly assigned animals (ERA chronic) were administered TBC-3214Na continuously with their drinking water, 29 MI rats received placebo, and 3 rats died during the observation period. Six weeks after infarction, hearts were evaluated in a blood-perfused working heart model during 60 minutes of ischemia and 30 minutes of reperfusion. In 14 MI rats, TBC-3214Na (ERA acute) was added to the cardioplegic solution during ischemia. Thirteen MI rats served as control.

RESULTS

At a similar infarct size, postischemic recovery of cardiac output (ERA chronic: 91% +/- 10%, ERA acute: 86% +/- 11% vs control: 52% +/- 15%; P < .05) and external heart work (ERA chronic: 90% +/- 10%, ERA acute: 85% +/- 13% vs control: 51% +/- 17%; P < .05) was significantly enhanced in both TBC-3214Na-treated groups whereas recovery of coronary flow was only improved in ERA acute rats (ERA acute: 121% +/- 23% vs ERA chronic: 75% +/- 13%; control: 64% +/- 15%; P < .05). Blood gas measurements showed enhanced myocardial oxygen delivery and consumption with acute TBC-3214Na therapy. Additionally, high-energy phosphates (phosphocreatine) were significantly higher and transmission electron microscopy revealed less ultrastructural damage under acute TBC-3214Na administration.

CONCLUSION

Acute endothelin-A receptor blockade is superior to chronic blockade in attenuating ischemia/reperfusion injury in failing hearts. Therefore, acute endothelin-A receptor blockade might be an interesting option for patients with heart failure undergoing cardiac surgery.

Calponin control of cerebrovascular reactivity: therapeutic implications in brain trauma

Calponin (Cp) is an actin-binding protein first characterized in chicken gizzard smooth muscle (SM). This review discusses the role of Cp in mediating SM contraction, the biochemical process by which Cp facilitates SM contraction and the function of Cp in the brain. Recent work on the role of Cp in pathological states with emphasis on traumatic brain injury is also discussed. Based on past and present data, the case is presented for targeting Cp for novel genetic and pharmacological therapies aimed at improving outcome following traumatic brain injury (TBI).