Blockade of endothelin receptors mitigates SARS-CoV-2-induced osteoarthritis.

Joint pain and osteoarthritis can occur as coronavirus disease 2019 (COVID-19) sequelae after infection. However, little is known about the damage to articular cartilage. Here we illustrate knee joint damage after wild-type, Delta and Omicron variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in vivo. Rapid joint injury with cystic lesions at the osteochondral junction was observed in two patients with post-COVID osteoarthritis and recapitulated in a golden Syrian hamster model. SARS-CoV-2-activated endothelin-1 signalling increased vascular permeability and caused viral spike proteins leakage into the subchondral bone. Osteoclast activation, chondrocyte dropout and cyst formation were confirmed histologically. The US Food and Drug Administration-approved endothelin receptor antagonist, macitentan, mitigated cystic lesions and preserved chondrocyte number in the acute phase of viral infection in hamsters. Delayed macitentan treatment at post-acute infection phase alleviated chondrocyte senescence and restored subchondral bone loss. It is worth noting that it could also attenuate viral spike-induced joint pain. Our work suggests endothelin receptor blockade as a novel therapeutic strategy for post-COVID arthritis.

Effects of Bosentan on Hypoxia, Inflammation and Oxidative Stress in Experimental Blunt Thoracic Trauma Model.

Background and Objectives: In this study, we aimed to investigate the effects of bosentan, an endothelin receptor antagonist, on endothelin-1 (ET-1), hypoxia-inducible factor-1 (HIF-1), nuclear factor-kappa B (NF-κB), and tumor necrosis factor (TNF)-α as inflammation markers, pro-oxidant antioxidant balance (PAB), and total antioxidant capacity (TAC) levels as oxidative stress parameters in lung tissues of rats in an experimental model of pulmonary contusion (PC) induced by blunt thoracic trauma. Materials and Methods: Thirty-seven male Sprague-Dawley rats were divided into five groups. C: The control group (n = 6) consisted of unprocessed and untreated rats. PC3 (n = 8) underwent 3 days of PC. PC-B3 (n = 8) received 100 mg/kg bosentan and was given orally once a day for 3 days. The PC7 group (n = 7) underwent 7 days of PC, and PC-B7 (n = 8) received 100 mg/kg bosentan and was given orally once a day for 7 days. Results: ET-1, NF-κB, TNF-α, HIF-1α, and PAB levels were higher, while TAC activity was lower in all groups compared with the control (p < 0.05). There was no significant difference in ET-1 and TNF-α levels between the PC-B3 and PC-B7 groups and the control group (p < 0.05), while NF-κB, HIF-1α, and PAB levels were still higher in both the PC-B3 and PC-B7 groups than in the control group. Bosentan decreased ET-1, NF-κB, TNF-α, HIF-1α, and PAB and increased TAC levels in comparison to the nontreated groups (p < 0.05). Conclusions: Bosentan decreased the severity of oxidative stress in the lungs and reduced the inflammatory reaction in rats with PC induced by blunt thoracic trauma. This suggests that bosentan may have protective effects on lung injury mechanisms by reducing hypoxia, inflammation, and oxidative stress. If supported by similar studies, bosentan can be used in both pulmonary and emergency clinics to reduce ischemic complications, inflammation, and oxidative stress in some diseases that may be accompanied by ischemia.

The Anti-Atherosclerotic Effects of Endothelin Receptor Antagonist, Bosentan, in Combination with Atorvastatin-An Experimental Study.

Bosentan, an endothelin receptor antagonist (ERA), has potential anti-atherosclerotic properties. We investigated the complementary effects of bosentan and atorvastatin on the progression and composition of the atherosclerotic lesions in diabetic mice. Forty-eight male ApoE-/- mice were fed high-fat diet (HFD) for 14 weeks. At week 8, diabetes was induced with streptozotocin, and mice were randomized into four groups: (1) control/COG: no intervention; (2) ΒOG: bosentan 100 mg/kg/day per os; (3) ATG: atorvastatin 20 mg/kg/day per os; and (4) BO + ATG: combined administration of bosentan and atorvastatin. The intra-plaque contents of collagen, elastin, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-a (TNF-a), matrix metalloproteinases (MMP-2, -3, -9), and TIMP-1 were determined. The percentage of lumen stenosis was significantly lower across all treated groups: BOG: 19.5 ± 2.2%, ATG: 12.8 ± 4.8%, and BO + ATG: 9.1 ± 2.7% compared to controls (24.6 ± 4.8%, p < 0.001). The administration of both atorvastatin and bosentan resulted in significantly higher collagen content and thicker fibrous cap versus COG (p < 0.01). All intervention groups showed lower relative intra-plaque concentrations of MCP-1, MMP-3, and MMP-9 and a higher TIMP-1concentration compared to COG (p < 0.001). Importantly, latter parameters presented lower levels when bosentan was combined with atorvastatin compared to COG (p < 0.05). Bosentan treatment in diabetic, atherosclerotic ApoE-/- mice delayed the atherosclerosis progression and enhanced plaques' stability, showing modest but additive effects with atorvastatin, which are promising in atherosclerotic cardiovascular diseases.

Is endothelin targeting finally ready for prime time?

The endothelin family of peptides has long been recognized as a physiological regulator of diverse biological functions and mechanistically involved in various disease states, encompassing, among others, the cardiovascular system, the kidney, and the nervous system. Pharmacological blockade of the endothelin system, however, has encountered strong obstacles in its entry into the clinical mainstream, having obtained only a few proven indications until recently. This translational gap has been attributable predominantly to the relevant side effects associated with endothelin receptor antagonism (ERA), particularly fluid retention. Of recent, however, an expanding understanding of the pathophysiological processes involving endothelin, in conjunction with the development of new antagonists of endothelin receptors or adjustment of their doses, has driven a flourish of new clinical trials. The favorable results of some of them have extended the proven indications for ET targeting to a variety of clinical conditions, including resistant arterial hypertension and glomerulopathies. In addition, on the ground of strong preclinical evidence, other studies are ongoing to test the potential benefits of ERA in combination with other treatments, such as sodium-glucose co-transporter 2 inhibition in fluid retentive states or anti-cancer therapies in solid tumors. Furthermore, antibodies providing long-term blockade of endothelin receptors are under testing to overcome the short half-life of most small molecule endothelin antagonists. These efforts may yet bring new life to the translation of endothelin targeting strategies in clinical practice.

Fixed-dose combination therapy in pulmonary arterial hypertension: Pros & cons.

Quality of life of patients suffering from chronic diseases is inevitably conditioned by the number of pills taken during the day. To improve patients' tolerability, compliance and quality of life and reduce healthcare costs, pharmaceutical companies are focusing on the commercialization of fixed-dose combination (FDC) therapies. The last ESC/ERS guidelines for the treatment of pulmonary arterial hypertension (PAH) recommend initial dual combination therapy for newly diagnosed patients at low or intermediate mortality risk. In this regard, polypills including an endothelin receptor antagonist (ERA) and a phosphodiesterase 5 inhibitor (PDE5-i) could represent an useful therapeutic strategy, although with some limitations. To date, evidence about the use of FDCs in PAH is limited but future studies evaluating their safety and efficacy are welcome.

Bosentan in the treatment of persistent pulmonary hypertension in newborns: a systematic review and meta-analysis.

BACKGROUND: Persistent pulmonary hypertension of the newborn is a life-threatening condition that affects about 1-2 per 1,000 live births worldwide. Bosentan is an oral dual endothelin receptor antagonist that may have a beneficial effect on persistent pulmonary hypertension of the newborn by reducing pulmonary vascular resistance and improving oxygenation. However, its role in persistent pulmonary hypertension of the newborn remains unclear. OBJECTIVES: To systematically evaluate the efficacy and safety of bosentan as an adjuvant therapy for persistent pulmonary hypertension of the newborn in newborns. METHODS: We searched six English and two Chinese databases from their inception to 1 January 2023 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We included randomised controlled trials and retrospective studies that compared bosentan with placebo or other drugs for persistent pulmonary hypertension of the newborn in newborns. We performed a meta-analysis using random-effects models and assessed the risk of bias and heterogeneity in the included studies. RESULTS: We included 10 studies with a total of 550 participants. Bosentan significantly reduced the treatment failure rate (relative risk = 0.25, P < 0.001), pulmonary artery pressure (mean difference = -11.79, P < 0.001), and length of hospital stay (mean difference = -1.04, P = 0.003), and increased the partial pressure of oxygen (mean difference = 10.02, P < 0.001) and blood oxygen saturation (SpO2) (mean difference = 8.24, P < 0.001) compared with a placebo or other drugs. The occurrence of adverse reactions was not significantly different between bosentan and a placebo or other drugs. CONCLUSIONS: Bosentan is effective in the treatment of persistent pulmonary hypertension of the newborn but adverse reactions such as abnormal liver function should be observed when using it.

Impact of rapid sequential combination therapy on distinct haemodynamic measures in newly diagnosed pulmonary arterial hypertension.

AIMS: In pulmonary arterial hypertension (PAH), upfront combination therapy with ERA and PDE5i is associated with a reduction in morbidity and mortality events and improves standard haemodynamics, but data remain limited. Aims of this study were (i) to capture detailed haemodynamic effects of rapid sequential dual combination therapy in patients with newly diagnosed PAH; (ii) to monitor the impact of treatment initiation on clinical variables and patients' risk status, and (iii) to compare the treatment effect in patients with 'classical PAH' and 'PAH with co-morbidities'. METHODS: Fifty patients (median age 57 [42-71] years, 66% female) with newly diagnosed PAH (76% idiopathic) were treated with a PD5i/sGC-S or ERA, followed by addition of the respective other drug class within 4 weeks. All patients underwent repeat right heart catheterization (RHC) during early follow-up. RESULTS: At early repeat RHC (7 ± 2 months), there were substantial reductions in mean pulmonary artery pressure (mPAP: 52.2 ± 13.5 to 39.0 ± 10.6 mmHg; -25.3%), and pulmonary vascular resistance (PVR: 12.1 ± 5.7 to 5.8 ± 3.1 WU; -52.1%), and an increase in cardiac index (2.1 ± 0.4 to 2.7 ± 0.7 mL/min/m2; +32.2%) (all P < 0.05). Haemodynamic improvements correlated with improved clinical parameters including 6-min walking distance (336 ± 315 to 389 ± 120 m), NTproBNP levels (1.712 ± 2.024 to 506 ± 550 ng/L, both P < 0.05) and WHO-FC at 12 months, resulting in improved risk status, and were found in patients with few (n = 37) or multiple cardiovascular co-morbidities (BMI > 30 kg/m2, hypertension, diabetes, coronary artery disease [≥3]; n = 13), albeit baseline PVR in PAH patients with multiple co-morbidities was lower (9.3 ± 4.4 vs. 13.1 ± 5.9 WU) and PVR reduction less pronounced compared with those with few co-morbidities (-42.7% vs. -54.7%). However, comprehensive haemodynamic assessment considering further variables of prognostic relevance such as stroke volume index and pulmonary artery compliance showed similar improvements among the two groups (SVI: +50.0% vs. +49.2%; PAC: 91.7% vs. 100.0%). Finally, the 4-strata risk assessment approach was better able to capture treatment response as compared with other approaches, particularly in patients with co-morbidities. CONCLUSIONS: Rapid sequential combination therapy with PDE5i/sGC-S and ERA substantially ameliorates cardiopulmonary haemodynamics at early follow-up in patients without, and to a lesser extent, with cardiovascular co-morbidities. This occurs in line with improvements of clinical parameters and risk status.

Endothelin System in Hypertension and Chronic Kidney Disease.

ET (endothelin) is a powerful vasoconstrictor 21-amino acid peptide present in many tissues, which exerts many physiological functions across the body and participates as a mediator in many pathological conditions. ETs exert their effects through ETA and ETB receptors, which can be blocked by selective receptor antagonists. ETs were shown to play important roles among others, in systemic hypertension, particularly when resistant or difficult to control, and in pulmonary hypertension, atherosclerosis, cardiac hypertrophy, subarachnoid hemorrhage, chronic kidney disease, diabetic cardiovascular disease, scleroderma, some cancers, etc. To date, ET antagonists are only approved for the treatment of primary pulmonary hypertension and recently for IgA nephropathy and used in the treatment of digital ulcers in scleroderma. However, they may soon be approved for the treatment of patients with resistant hypertension and different types of nephropathy. Here, the role of ETs is reviewed with a special emphasis on participation in and treatment of hypertension and chronic kidney disease.

Advances in the discovery of drugs that treat pulmonary arterial hypertension.

INTRODUCTION: Distal pulmonary arterial remodeling and elevated pulmonary vascular resistance are characteristic of pulmonary arterial hypertension (PAH). Current approved vasodilator-specific PAH therapy that includes phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators, endothelin receptor antagonists, and prostanoids has demonstrated dramatic enhancement in functional capacity, quality of life, and invasive hemodynamics. However, none of these treatments are curative, underscoring the need to identify new pathophysiologic signaling pathways. AREAS COVERED: The author provides a comprehensive review on current knowledge and recent development in the understanding of PAH. Furthermore, the author discusses PAH potential genetic causes as well as novel molecular signaling pathways. This article also reviews the currently approved PAH specific therapy based on pivotal clinical trials and ongoing clinical trials using novel compounds that specifically target PAH pathogenesis. EXPERT OPINION: The discovery of novel signaling pathways - growth factors, tyrosine kinases, BMPs, estrogen, and serotonin - involved in the PAH pathobiology will lead within the next 5 years to the approval of new therapeutic agents targeting these different pathways. If proven beneficial, these new agents may reverse or at least prevent the progression of this devastating and lethal disease.

The potential benefit of endothelin receptor antagonists' therapy in idiopathic pulmonary fibrosis: A meta-analysis of results from randomized controlled trials.

BACKGROUND: Fibrotic diseases take a very heavy toll in terms of morbidity and mortality equal to or even greater than that caused by metastatic cancer. This meta-analysis aimed to evaluate the effect of endothelin receptor antagonists on idiopathic pulmonary fibrosis. METHOD: A systematic search of the clinical trials from the Medline, Google Scholar, Cochrane Library, and PubMed electronic databases was performed. Stata version 12.0 statistical software (Stata Crop LP, College Station, TX) was adopted as statistical software. RESULT: A total of 5 studies, which included 1500 participants. Our analysis found there is no significant difference between using the endothelin receptor antagonists' group and placebo groups regarding the lung function via estimating both the change of forced vital capacity from baseline and DLco index. Exercise capacity and serious adverse effects are taken into consideration as well; however, there is still no significant change between the 2 groups. CONCLUSION: This meta-analysis provides insufficient evidence to support that endothelin receptor antagonists' administration provides a benefit among included participants who encounter idiopathic pulmonary fibrosis.

Oral administration of a dual ETA/ETB receptor antagonist promotes neuroprotection in a rodent model of glaucoma.

Purpose: Glaucoma is a neurodegenerative disease associated with elevated intraocular pressure and characterized by optic nerve axonal degeneration, cupping of the optic disc, and loss of retinal ganglion cells (RGCs). The endothelin (ET) system of vasoactive peptides (ET-1, ET-2, ET-3) and their G-protein coupled receptors (ETA and ETB receptors) have been shown to contribute to the pathophysiology of glaucoma. The purpose of this study was to determine whether administration of the endothelin receptor antagonist macitentan was neuroprotective to RGCs and optic nerve axons when administered after the onset of intraocular pressure (IOP) elevation in ocular hypertensive rats. Methods: Male and female Brown Norway rats were subjected to the Morrison model of ocular hypertension by injection of hypertonic saline through the episcleral veins. Following IOP elevation, macitentan (5 mg/kg body wt) was administered orally 3 days per week, and rats with IOP elevation were maintained for 4 weeks. RGC function was determined by pattern electroretinography (PERG) at 2 and 4 weeks post-IOP elevation. Rats were euthanized by approved humane methods, and retinal flat mounts were generated and immunostained for the RGC-selective marker Brn3a. PPD-stained optic nerve sections were imaged by confocal microscopy. RGC and axon counts were conducted in a masked manner and compared between the treatment groups. Results: Significant protection against loss of RGCs and optic nerve axons was found following oral administration of macitentan in rats with elevated IOP. In addition, a protective trend for RGC function, as measured by pattern ERG analysis, was evident following macitentan treatment. Conclusions: Macitentan treatment had a neuroprotective effect on RGCs and their axons, independent of its IOP-lowering effect, suggesting that macitentan may complement existing treatments to prevent neurodegeneration during ocular hypertension. The findings presented have implications for the use of macitentan as an oral formulation to promote neuroprotection in glaucoma patients.

Pharmacological counseling in hepatotoxicity induced by macitentan and selexipag: a case report.

BACKGROUND: Pulmonary arterial hypertension is a progressive, debilitating condition characterized by increased resistance in the pulmonary arterial circulation. Current treatments for pulmonary arterial hypertension include endothelin receptor antagonists such as bosentan, sitaxentan, ambrisentan, macitentan, and oral prostacyclin receptor agonists such as selexipag. Endothelin receptor antagonists have been associated with liver injury, while hepatotoxicity was not reported for selexipag. Although genetic variability has been indisputably associated with variability in drug response, no study has been designed until now to assess its effects on the pharmacokinetics of endothelin receptor antagonists or selexipag. CASE PRESENTATION: We report the case of a 58-year-old female Caucasian patient with a dramatic increase in plasma levels of transaminases after treatment with macitentan and selexipag, drugs whose risk of causing liver injury has so far been considered limited. After therapy discontinuation, plasma levels of transaminases returned to baseline, thus suggesting a role of these drugs in the observed hepatotoxicity. After pharmacological counseling, we decided to introduce ambrisentan for the patient's treatment. After 7 months of treatment, no liver injury has been reported. To evaluate the role of genetic factors in the observed hepatotoxicity, we genotyped the patient for single-nucleotide polymorphisms previously associated with macitentan, ambrisentan, or selexipag metabolism. We found a genetic profile associated with a poor metabolizer (PM) phenotype for CYP2C8 and CYP2C9, key enzymes for elimination of both macitentan and selexipag. The reported results suggest that an allelic profile associated with low activity for CYP2C8 and CYP2C9 enzyme could be a potential risk factor for macitentan and selexipag-induced liver injury and could provide a possible marker for early identification of subjects at higher risk of developing hepatotoxicity. CONCLUSIONS: A multidisciplinary approach based on clinical evaluation, as well as pharmacological counseling and evaluation of the patient's genetic profile, might be useful for identification of patients with a high chance of drug-induced liver injury, avoiding unnecessary risks in therapy selection and prescription.

Determination and pharmacokinetic study of riociguat by UPLC-MS/MS in human plasma.

Pulmonary hypertension (PH) is frequent in the general population and is linked to an increased risk of death. Riociguat is a kind of endothelin receptor antagonist that is often used to treat PH. For pharmacokinetic studies and the determination of riociguat in PH patients, a new, quick, easy, and sensitive UPLC-MS/MS approach was designed and validated. Riociguat and irbesartan (IS) were detected using ESI in positive ion and multiple reaction monitoring mode, respectively, by monitoring the mass transitions m/z 423.0 â†’ 391.0 and 429.1 â†’ 206.9. A reverse-phase C18 column (5 µm, 4.6 × 150 mm) was used with an isocratic mobile phase of water containing 0.1 % formic acid-acetonitrile (25:75, v/v) at a flow rate of 1 ml/min for chromatographic separation. In the range of 5-400 ng/ml, the calibration curve was linear and had a good correlation coefficient (0.9972). This is the first UPLC-MS/MS technique that has been developed and validated for determining riociguat from human plasma. The developed analytical method was extensively validated for linearity, selectivity, specificity, accuracy, precision, sensitivity, stability, matrix effect and recovery, according to FDA criteria. The devised approach was successfully used for a pharmacokinetic research and riociguat determination in PH patients.

Endothelial and vascular smooth muscle dysfunction in hypertension.

The development of essential hypertension involves several factors. Vascular dysfunction, characterized by endothelial dysfunction, low-grade inflammation and structural remodeling, plays an important role in the initiation and maintenance of essential hypertension. Although the mechanistic pathways by which essential hypertension develops are poorly understood, several pharmacological classes available on the clinical settings improve blood pressure by interfering in the cardiac output and/or vascular function. This review is divided in two major sections. The first section depicts the major molecular pathways as renin angiotensin aldosterone system (RAAS), endothelin, nitric oxide signalling pathway and oxidative stress in the development of vascular dysfunction. The second section describes the role of some pharmacological classes such as i) RAAS inhibitors, ii) dual angiotensin receptor-neprilysin inhibitors, iii) endothelin-1 receptor antagonists, iv) soluble guanylate cyclase modulators, v) phosphodiesterase type 5 inhibitors and vi) sodium-glucose cotransporter 2 inhibitors in the context of hypertension. Some classes are already approved in the treatment of hypertension, but others are not yet approved. However, due to their potential benefits these classes were included.

Organic Anion Transporter Gene Variants Associated With Plasma Exposure and Long-Term Response to Atrasentan in Patients With Diabetic Kidney Disease.

Plasma exposure of the endothelin receptor antagonist atrasentan varies between individuals and is associated with nephroprotective effects and the risk of heart failure. We examined the influence of genetic polymorphisms on atrasentan plasma exposure and pharmacodynamic effects. We performed a substudy of the Study of Diabetic Nephropathy With Atrasentan (SONAR) trial which enrolled adults with type 2 diabetes and chronic kidney disease (estimated glomerular filtration rate: 25-75 mL/min/1.73 m2 , and a urine albumin-to-creatinine ratio of 300-5,000 mg/g). Single nucleotide polymorphisms (SNPs) were determined for prespecified membrane transporters, metabolizing enzymes, and the endothelin-1 peptide. The associations among genotype, atrasentan plasma exposure, and the effect of atrasentan on the prespecified kidney and heart failure hospitalization (HHF) outcomes was assessed with Cox proportional hazards regression models. Of 3,668 patients randomized, 2,329 (63.5%) consented to genotype analysis. Two SNPs in the SLCO1B1 gene (rs4149056 and rs2306283), encoding the hepatic organic anion transporter 1B1 (OATP1B1), showed the strongest association with atrasentan plasma exposure. Based on their SLCO1B1 genotype, patients were classified into normal (atrasentan area under the plasma-concentration time curve from zero to infinity (AUC0-inf ) 41.3 ng·h/mL) or slow (atrasentan AUC0-inf 49.7 ng·h/mL, P < 0.001) OATP1B1 transporter phenotypes. Among patients with a normal OATP1B1 phenotype, the hazard ratio (HR) with atrasentan for the primary kidney and HHF outcomes were 0.61 (95% confidence interval (CI): 0.45-0.81) and 1.35 (95% CI: 0.84-2.13), respectively. In the slow transporter phenotype, HRs for kidney and HHF outcomes were 1.95 (95% CI: 0.95-4.03, P-interaction normal phenotype = 0.004), and 4.18 (95% CI: 1.37-12.7, P-interaction normal phenotype = 0.060), respectively. OATP1B1 gene polymorphisms are associated with significant between-patient variability in atrasentan plasma exposure and long-term efficacy and safety.

Endothelin-axis antagonism enhances tumor perfusion in pancreatic cancer.

Delivery of therapeutic agents in pancreatic cancer (PC) is impaired due to its hypovascular and desmoplastic tumor microenvironment. The Endothelin (ET)-axis is the major regulator of vasomotor tone under physiological conditions and is highly upregulated in multiple cancers. We investigated the effect of dual endothelin receptor antagonist bosentan on perfusion and macromolecular transport in a PC cell-fibroblast co-implantation tumor model using Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI). Following bosentan treatment, the contrast enhancement ratio and wash-in rates in tumors were two- and nine times higher, respectively, compared to the controls, whereas the time to peak was significantly shorter (7.29 ± 1.29 min v/s 22.08 ± 5.88 min; p = 0.04). Importantly, these effects were tumor selective as the magnitudes of change for these parameters were much lower in muscles. Bosentan treatment also reduced desmoplasia and improved intratumoral distribution of high molecular weight FITC-dextran. Overall, these findings support that targeting the ET-axis can serve as a potential strategy to selectively enhance tumor perfusion and improve the delivery of therapeutic agents in pancreatic tumors.

Endothelin A receptor antagonist attenuated renal iron accumulation in iron overload heme oxygenase-1 knockout mice.

Progressive iron accumulation and renal impairment are prominent in both patients and mouse models of sickle cell disease (SCD). Endothelin A receptor (ETA) antagonism prevents this iron accumulation phenotype and reduces renal iron deposition in the proximal tubules of SCD mice. To better understand the mechanisms of iron metabolism in the kidney and the role of the ETA receptor in iron chelation and transport, we studied renal iron handling in a nonsickle cell iron overload model, heme oxygenase-1 (Hmox-1-/-) knockout mice. We found that Hmox-1-/- mice had elevated plasma endothelin-1 (ET-1), cortical ET-1 mRNA expression, and renal iron content compared with Hmox-1+/+ controls. The ETA receptor antagonist, ambrisentan, attenuated renal iron deposition, without any changes to anemia status in Hmox-1-/- mice. This was accompanied by reduced urinary iron excretion. Finally, ambrisentan had an important iron recycling effect by increasing the expression of the cellular iron exporter, ferroportin-1 (FPN-1), and circulating total iron levels in Hmox-1-/- mice. These findings suggest that the ET-1/ETA signaling pathway contributes to renal iron trafficking in a murine model of iron overload.

Adolescents and adults with Fontan circulation: insights from the PREpArE-Fontan registry.

The Patient Registry for Adolescents and Adults with Stable Fontan Circulation aims to describe a contemporary cohort of Fontan patients who could be eligible for a clinical trial investigating macitentan, an endothelin receptor antagonist. This international, non-interventional, multicentre, cross-sectional, observational registry enrolled patients with "stable" Fontan circulation ≥10 years following extra-cardiac conduit or lateral tunnel procedure. Main exclusion criteria were NYHA functional class IV, reoperation of Fontan circulation, or signs of disease worsening. Patient characteristics at enrolment are described; available data were collected during a single registration visit. Of the 266 screened patients, 254 were included in this analysis. At enrolment, median (interquartile range) age was 24 (20;30) years, 37%/63% of patients were from the USA/Europe, 54% were male, 54%/47% had undergone extra-cardiac conduit/lateral tunnel procedures, and 95% were in NYHA functional class I or II. History of arrhythmia was more common in older patients and patients with lateral tunnel; overall prevalence was 19%. Most laboratory values were within the normal range but mean creatinine clearance was abnormally low (87.7 ml/min). Angiotensin-converting enzyme inhibitors were used by 48% of patients and their use was associated with creatinine clearance <90 ml/min (p = 0.007), as was Fontan completion at an older age (p = 0.007). 53.4% of patients had clinical characteristics that could potentially meet an endothelin receptor antagonist trial's eligibility criteria. The PREpArE-Fontan registry describes a cohort of patients who could potentially participate in an endothelin receptor antagonist trial and identified early subtle signs of Fontan failure, even in "stable" patients.

Cardioprotective effects of bosentan in 5-fluorouracil-induced cardiotoxicity.

5-fluorouracil (5-FU) is a widely used chemotherapeutic agent but cardiotoxicity challenges its clinical usefulness. Thus, searching for more cardioprotective drugs is highly required to prevent the accompanied cardiac hazards. Up to date, the different mechanisms involved in 5-FU cardiotoxicity are still unclear and there is no evaluation of bosentan's role in controlling these cardiac complications. This forced us to deeply study and evaluate the possible cardiopreserving properties of bosentan and different mechanisms involved in mediating it. 32 Wistar albino rats were included in our experiment and induction of cardiotoxicity was performed via administration of 5-FU (150 mg/kg) on 5th day of the experiment by intraperitoneal (i.p.) injection with or without co-administration of bosentan (50 mg/kg/day) orally for 7days. Our data revealed that 5-FU could induce cardiotoxicity which was detected as significant increases of troponin I, lactate dehydrogenase (LDH), creatine kinase- MB (CK-MB), endothelin receptors, malondialdehyde (MDA), toll like receptor4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor kappa B (NFκB), and caspase 3 levels. However, there is marked decrease in endothelial nitric oxide synthase (eNOS), reduced glutathione (GSH) and total antioxidant capacity (TAC). In addition, the histopathological examination showed severe toxic features of cardiac injury. Interestingly, co-administration of bosentan could ameliorate 5-FU-induced cardiotoxicity via improving the detected biochemical and histopathological changes besides modulation of TLR4/MyD88/NFκB signaling pathway, eNOS, and endothelin receptors. Bosentan had a significant cardioprotective effect against 5-FU induced cardiac damage. This effect may be attributed to its ability to inhibit endothelin receptors, stimulates eNOS, anti-oxidant, anti-inflammatory, anti-apoptotic properties with modulation of TLR4/MyD88/NFκB signaling pathway.

Collaborative registry of pulmonary hypertension in Argentina (RECOPILAR). Final analysis / Registro colaborativo de hipertensión pulmonar en Argentina (RECOPILAR): análisis final

Abstract The epidemiology of pulmonary hypertension (PH), especially pulmonary arterial hypertension (PAH), has not been evaluated in our country, therefore there is no reference parameter to establishing the representativeness of this information in the national order. This registry represents the first collaborative effort to provide a knowledge base of this disease, including 5 scientific societies that represent different specialties (pediatrics, rheumatology, pulmonology and cardiology) with data from 23 Argentine provinces. These efforts involved five societies of various adult (cardiology, rheumatology, and pulmonology) and pediatric (cardiology) specialties. Subjects were grouped (1-5) in accord with the 2013 Nice classification. A total of 627 patients (mean age, 50.8±18 years; women, 69.2%) were recruited. Incident cases accounted for 53%. Functional class III-IV accounted for 69% at time of diagnosis and 33.4% at time of inclusion. Distributions in groups 1-5 were 63.6%, 15.9%, 8.3%, 9.7%, and 2.4%, respectively. Treatment consisted of diuretics (51.2%), mineralocorticoid receptor antagonists (44.7%), digoxin (16.6%), anticoagulants (39.2%), renin-angiotensin antagonists (15.5%), beta blockers (15.6%), and calcium channel blockers (8%). Rates of specific therapies usage in PAH vs. non-PAH group were 80.5% vs. 40.8% (phosphodiesterase-5 inhibitors: 71% vs. 38.6%; endothelin receptor antagonists: 54.4% vs. 14.5%; prostanoids: 14.3 vs. 3.1%; all p < 0.001). Three-year survival in PAH and non-PAH differed significantly (82.8% vs. 73.3%; p = 0.001). In the Argentine RECOPILAR registry, the clinic-epidemiologic profile was that of advanced-stage disease. Diagnostic workups and therapeutics interventions, including use of specific therapy for PAH, were consistent with current recommendations. Despite delays in diagnosis, survival was aligned with other contemporary registries.

Resumen La epidemiología de la hipertensión pulmonar (HP), especialmente la arterial (HAP), no ha sido evaluada en nuestro país, por lo cual no existe un parámetro de referencia para establecer la representatividad de esta información en el orden nacional. El presente registro representa el primer esfuerzo colaborativo para una base de conocimiento de esta enfermedad, incluyendo 5 sociedades científicas que representan a distintas especiali dades médicas (pediatría, reumatología, neumonología y cardiología) con datos de 23 provincias argentinas. Los sujetos se agruparon (1-5) de acuerdo con la clasificación de Niza de 2013. El seguimiento se completó en 583 pacientes (93%) un año después del final de la inscripción. Se incluyeron 627 pacientes (edad media, 50.8 ± 18 años; mujeres, 69.2%). Los casos incidentes representaron el 53%. La clase funcional III-IV representaba 69% en el momento del diagnóstico y 33.4% en el momento de la inclusión. Las manifestaciones clínicas fueron disnea (81.8%), fatiga (54.1%), síncope (10.8%), dolor torácico (14.7%), palpitaciones (20.9%) e insuficiencia cardíaca (20.4%). Las tasas de uso de terapias específicas en la hipertensión arterial pulmonar (HAP) frente al grupo sin HAP fueron del 80.5% frente al 40.8%. La supervivencia a tres años en los subconjuntos de HAP y no HAP difirió significativamente (82.8% vs. 73.3%; p = 0.001). En el registro RECOPILAR argentino, que aborda principalmente la HAP, el perfil clínico-epidemiológico fue el d e una enfermedad en estadios avanzados. El diag nóstico y las intervenciones terapéuticas, incluido el uso de terapia específica para la HAP, fueron consistentes con las recomendaciones actuales.