Endothelin System Research Articles

Endothelin Inhibitors in Chronic Kidney Disease: New Treatment Prospects.

The endothelin system is reported to play a significant role in glomerular and tubulointerstitial kidney disease. In the kidney, endothelins are produced in mesangial cells and the glomerular basement membrane by the endothelium and podocytes. The endothelin system regulates glomerular function by inducing proliferation, increasing permeability and in effect proteinuria, and stimulating inflammation, tubular fibrosis, and glomerular scarring. Endothelin A receptor antagonists have been proven to delay the progression of chronic kidney disease and play a protective role in immunoglobulin A nephropathy, focal segmental glomerulosclerosis, and diabetic nephropathy. There are several ongoing research studies with ETAR antagonists in nondiabetic nephropathy, Alport disease, vasculitis and scleroderma nephropathy, which results are promising. Some reports suggest that the endothelin system might contribute to ischemia-reperfusion injury, acute graft rejection and deterioration of graft function. Endothelin inhibition in renal transplantation and its influence on graft survival is the future direction needing further research. The most frequent side effects associated with ETAR antagonists is fluid retention. Additionally, it should be considered if selective ETAR antagonists therapy needs to be co-administered with sodium-glucose co-transporter 2 inhibitors, renin-angiotensin-aldosterone inhibitors or diuretics and which patients should be recruited to such treatment to minimize the risk of adverse outcomes.

Complex regulation of tau phosphorylation by the endothelin system in brain microvascular endothelial cells (BMVECs): link to barrier function.

Endothelin-1 (ET-1), the most potent vasoconstrictor identified to date, contributes to cerebrovascular dysfunction. ET-1 levels in postmortem brain specimens from individuals diagnosed with Alzheimer's disease (AD) and related dementias (ADRD) were shown to be related to cerebral hypoxia and disease severity. ET-1-mediated vascular dysfunction and ensuing cognitive deficits have also been reported in experimental models of AD and ADRD. Moreover, studies also showed that ET-1 secreted from brain microvascular endothelial cells (BMVECs) can affect neurovascular unit integrity in an autocrine and paracrine manner. Vascular contributions to cognitive impairment and dementia (VCID) is a leading ADRD cause known to be free of neuronal tau pathology, a hallmark of AD. However, a recent study reported cytotoxic hyperphosphorylated tau (p-tau) accumulation, which fails to bind or stabilize microtubules in BMVECs in VCID. Thus, the study aimed to determine the impact of ET-1 on tau pathology, microtubule organization, and barrier function in BMVECs. Cells were stimulated with 1 μM ET-1 for 24 h in the presence/absence of ETA (BQ123; 20 μM) or ETB (BQ788; 20 μM) receptor antagonists. Cell lysates were assayed for an array of phosphorylation site-specific antibodies and microtubule organization/stabilization markers. ET-1 stimulation increased p-tau Thr231 but decreased p-tau Ser199, Ser262, Ser396, and Ser214 levels only in the presence of ETA or ETB antagonism. ET-1 also impaired barrier function in the presence of ETA antagonism. These novel findings suggest that (1) dysregulation of endothelial tau phosphorylation may contribute to cerebral microvascular dysfunction and (2) the ET system may be an early intervention target to prevent hyperphosphorylated tau-mediated disruption of BMVEC barrier function.

Right Ventricular Hypertrophy in Spontaneously Hypertensive Rats (SHR/NHsd) Is Associated with Inter-Individual Variations of the Pulmonary Endothelin System.

Spontaneously hypertensive rats (SHRs) develop severe hypertension and subsequently left ventricular hypertrophy. Whether they also develop right ventricular hypertrophy is not clear. We analyzed 76 female SHRs (strain SHR/NHsd) and observed severe right ventricular hypertrophy in 7% of these rats (SHR-RVH). Right ventricular hypertrophy did not correlate with the age of the rats and was already seen in one rat at the pre-hypertensive state. The current study investigated the molecular fingerprint of the lung and right ventricle from SHR-RVH and compared this first to SHRs that did develop left but not right ventricular hypertrophy, and second to normotensive rats without hypertrophy. Rats with right ventricular hypertrophy had a decreased expression of the endothelin-B receptor (EDNRB) in the lung, together with an increased protein content of endothelin-1 and an increased expression of ACTA2A. Furthermore, in the right ventricle, a down-regulation of the endothelin-A receptor (EDNRA) was found, consistent with a mild phenotype. The data suggest that in a sub-group of SHR/NHsd rats, low expression of the endothelin clearance receptor (endothelin-B receptor) in the lung triggers an increase in vascular resistance to the right ventricle that then triggers hypertrophy. Our study is the first description of a genetic variant in a defined SHR strain.

Abstract P437: Correlation between plasma CT-proET-1 and renal dysfunction in patients with resistant hypertension. A biomarker analysis of the PRECISION study.

Hypothesis: Endothelin (ET)-1 is upregulated in hypertension and especially resistant forms of hypertension. As ET-1 is a paracrine hormone involved in renal organ damage, we investigated the correlation between eGFR and activity of the ET system in the resistant hypertensive population of the PRECISION trial (NCT03541174), in which aprocitentan, a dual endothelin ET A /ET B receptor antagonist, significantly reduced blood pressure and UACR. To assess activity of the ET system, ET-1 and CT-proET-1, a stable peptide and biomarker for ET-1 production, were measured in plasma. Methods: From plasma collected at screening from the future randomized patients in PRECISION, ET-1 (n=688) and CT-proET-1 (n=100, randomly selected) were measured by ELISA and LC-MS-based assays respectively. Baseline levels of CT-proET-1 were determined on pooled plasma from healthy adults (n=70). Pearson correlation coefficient was determined between biomarkers of the ET system and eGFR. Results: CT-proET-1 concentrations measured in patients with resistant hypertension were higher than concentrations from healthy subjects (83 vs 55 pM). In patients with an eGFR≥60 mL/min/1.73m 2 , mean CT-proET-1 concentration was 75 pM [95% CI 70-81; n=77] as compared to 116 pM [95% CI 95-140 n=23] in patients with eGFR<60 mL/min/1.73m 2 . In these two subgroups, mean ET-1 concentrations were 1.90 ng/L [95% CI 1.85-1.95; n=531] and 2.10 ng/L [95% CI 1.99-2.22; n=157] for patients with an eGFR≥60 and eGFR<60 mL/min/1.73m 2 respectively. There was an inverse correlation between CT-proET-1 and eGFR (r=-0.61, p<0.0001) and a less pronounced correlation between ET-1 and eGFR (r=-0.11, p=0.0027) (see Figure ). Conclusions: In patients with resistant hypertension, there was a strong inverse correlation between plasma CT-proET-1 and renal function, suggesting the role of the ET system not only in hypertension but also in renal damage. These data demonstrate that CT-proET-1 is a sensitive biomarker of the ET system, reflecting the production of ET-1.

Abstract 34: Elevation of Plasma anti-Endothelin A Receptor Autoantibodies in Lupus Subjects Correlates with Plasma Vascular Adhesion Molecule-1 Independent of Blood Pressure

Systemic Lupus Erythematosus (SLE) is an autoimmune disease that is characterized by deposition of autoantibodies and their immune complexes, resulting in inflammation, and end-organ damage to the kidney and vasculature. SLE disproportionally affects women to men (9:1 ratio), with a high prevalence in African American women and patients often have cardiovascular complications including hypertension (HTN). The activation of the endothelin (ET) system has been implicated in numerous pathological disease states including HTN, SLE, and diabetes. Recently, dual ET receptor antagonism was approved for treatment of patients with uncontrolled hypertension. Studies have demonstrated the presence of biologically active endothelin A receptor autoantibodies (ETAR-AAs) in systemic sclerosis and cystic fibrosis patients. Few studies have investigated the role of the synergistic interplay of SLE and HTN on ETAR-AAs. We hypothesized that women with SLE and HTN would have elevated plasma ETAR-AAs compared to control or SLE only subjects. To investigate this, we recruited non-SLE non-HTN controls (n=10), non-SLE HTN (n=10), SLE non-HTN (n=8), and SLE-HTN (n=10) female human subjects and analyzed clinical characteristics, plasma ETAR-AAs, soluble vascular adhesion molecule-1 (sVCAM-1) and soluble intracellular adhesion molecule-1 (sICAM-1). Plasma ETAR-AAs did not significantly correlate with either age (r=-0.1375; p=0.4453) or body mass index (r=-0.3149; p=0.0743). When subjects were categorized by SLE or HTN diagnosis, we found that subjects with SLE had a profound increase in ETAR-AAs compared to non-SLE controls (p<0.0001) while the levels were similar between HTN and non-HTN controls (p=0.7626). Next, we stratified subjects by blood pressure status and found a significant elevation in plasma ETAR-AAs in SLE non-HTN over non-SLE HTN subjects (p=0.0121), while SLE-HTN subjects had significant elevations in ETAR-AAs compared to both non-SLE non-HTN (p=0.0183) and non-SLE HTN (p=0.0014) subjects. We correlated plasma levels of ETAR-AA with sVCAM-1 and sICAM-1 and found that plasma ETAR-AAs were positively associated with plasma sVCAM-1 (r=0.4288; p=0.0114) and sICAM-1 (r=0.3812; p=0.0286). These data indicate that irrespective of blood pressure status, elevated plasma ETAR-AAs are associated with markers of vascular dysfunction in SLE subjects. Further investigation of cell-specific ETAR-AA and ETAR signaling should be performed in murine models and human subjects with SLE.

Zibotentan in Microvascular Angina: A Randomized, Placebo-Controlled, Crossover Trial.

Background: Microvascular angina is associated with dysregulation of the endothelin system and impairments in myocardial blood flow, exercise capacity, and health-related quality of life. The G allele of the noncoding single nucleotide polymorphism RS9349379 enhances expression of the endothelin-1 gene (EDN1) in human vascular cells, potentially increasing circulating concentrations of Endothelin-1 (ET-1). Whether zibotentan, an oral ET-A receptor selective antagonist, is efficacious and safe for the treatment of microvascular angina is unknown. Methods: Patients with microvascular angina were enrolled in this double-blind, placebo-controlled, sequential crossover trial of zibotentan (10 mg daily for 12 weeks). The trial population was enriched to ensure a G allele frequency of 50% for the RS9349379 single nucleotide polymorphism. Participants and investigators were blinded to genotype. The primary outcome was treadmill exercise duration (seconds) using the Bruce protocol. The primary analysis estimated the mean within-participant difference in exercise duration after treatment with zibotentan versus placebo. Results: A total of 118 participants (mean ±SD; years of age 63.5 [9.2 ]; 71 [60.2% ] females; 25 [21.2% ] with diabetes) were randomized. Among 103 participants with complete data, the mean exercise duration with zibotentan treatment compared with placebo was not different (between-treatment difference, -4.26 seconds [95 ] CI, -19.60 to 11.06] P=0.5871). Secondary outcomes showed no improvement with zibotentan. Zibotentan reduced blood pressure and increased plasma concentrations of ET-1. Adverse events were more common with zibotentan (60.2%) compared with placebo (14.4%; P<0.001). Conclusions: Among patients with microvascular angina, short-term treatment with a relatively high dose (10 mg daily) of zibotentan was not beneficial. Target-related adverse effects were common.

Abstract P146: Sex-Dependent Regulation of the Endothelin System in Multi-End Organ Inflammation in Lupus-Associated Cardiovascular Disease

Lupus is a chronic autoimmune disease characterized by IgG deposition, Toll-like receptor 7 (TLR7) overactivation, and autoantibody production resulting in end organ inflammation. SLE disproportionally affects women, SLE disproportionally affects women to men (9:1 ratio), with a high prevalence in African American women. Highly vascularized organs are severely impacted by lupus, specifically the kidneys and brain. Recent literature has shown that cardiovascular disease (CVD) has significant detrimental impacts on organ crosstalk. Endothelin-1 (ET-1), a potent vasoconstricting peptide, has been shown elevated in patients with CVD and in patients with lupus independent of disease severity. However, the extent to which ET-1 promotes lupus-associated CVD and end organ cross talk remains to be elucidated. Therefore, we hypothesized that TLR7 overactivation in a murine model of SLE-associated CVD would lead to a sex-dependent regulation of the renal and cerebral ET systems. Female and male lupus-prone B6.Nba2 mice were subjected to bi-weekly treatment with the Resiquimod (R848; TLR7/8 agonist; 100ug/30ul) or vehicle control (Acetone) for one month and subsequently studied for 12 weeks. At 16 weeks, the kidneys and brains were collected for histology and ET system (ET-1, ET A, and ET B ) analysis. Exploration of specific end organ damage demonstrates a profound increase in renal and cerebral IgG complex deposition as well as renal macrophages and T cells in both females and males receiving R848. Renal ET-1 levels displayed no time nor treatment-dependent effects in females, while males exhibited a significant time-dependent increase in expression at the 4 and 16-week timepoints. Interestingly, at the receptor level, neither sex demonstrated differences in ET A nor ET B levels in the kidney. While renal ET-1 level did not change, females demonstrated a significant increase in cerebral ET-1 at the 16-week timepoint, while males trended for increased cerebral ET-1. At the receptor level, females had a trend for increased cerebral ET A expression, while there was no change in males, and neither sex displayed a change in ET B receptor expression. These findings suggest a potential shift towards a pro-inflammatory state via the cerebral ET-1/ET A signaling axis in the R848-treated females. These findings warrant further exploration into the end-organ specific pathophysiological role ET-1/ET A signaling in multiorgan crosstalk in lupus-associated CVD.

Sunitinib-induced endocapillary proliferative glomerulonephritis with IgA2 deposit in addition to thrombotic microangiopathy: a case report

BackgroundSunitinib, a multi-targeted tyrosine kinase inhibitor, is used as a second-line therapy for gastrointestinal stromal tumors (GIST) resistant to imatinib. However, its impact on the vascular endothelial growth factor (VEGF) pathway can lead to significant toxicities, including hypertension and thrombotic microangiopathy (TMA).Case presentationThis case report describes a unique instance of a patient with metastatic GIST who developed endocapillary proliferative glomerulonephritis (EPGN) with IgA2 deposits and TMA following sunitinib treatment. The patient presented with severe hypertension, nephrotic syndrome, and acute kidney injury. Renal biopsy confirmed the diagnosis, revealing IgA2 deposits, which are not commonly associated with TMA. Discontinuation of sunitinib led to a rapid improvement in renal function and proteinuria. The potential mechanisms underlying sunitinib-induced glomerular injury may involve the blockade of VEGFR-1, affecting immune cell recruitment and function, and the disruption of the nitric oxide and endothelin systems, leading to endothelial damage and immune dysregulation. Management of these toxicities requires a personalized approach, with options ranging from symptomatic relief to drug discontinuation. The use of endothelin receptor antagonists and other therapeutic alternatives for GIST management is discussed.ConclusionsThis case highlights the complex interplay between the therapeutic effects of sunitinib and its potential renal and cardiovascular toxicities, emphasizing the need for close monitoring and effective management strategies to optimize patient outcomes.

The role of venous capacity in fluid retention with endothelin A antagonism: Mathematical modelling of the RADAR trial.

Endothelin-1 (ET-1) receptor A (ETA) antagonists reduce proteinuria and prevent renal outcomes in chronic kidney disease (CKD) patients, but their utility has been limited because of associated fluid retention, resulting in increased heart failure risk. Understanding the mechanisms responsible for fluid retention could result in solutions that preserve renoprotective effects while mitigating fluid retention, but the complexity of the endothelin system has made identification of the underlying mechanisms challenging. We utilized a previously developed mathematical model of ET-1 kinetics, ETA receptor antagonism, kidney function, haemodynamics, and sodium and water homeostasis to evaluate hypotheses for mechanisms of fluid retention with ETA antagonism. To do this, we simulated the RADAR clinical trial of atrasentan in patients with type 2 diabetes and CKD and evaluated the ability of the model to predict the observed decreases in haematocrit, urine albumin creatinine ratio (UACR), mean arterial pressure (MAP), and estimated glomerular filtration rate (eGFR). An effect of ETA antagonism on venodilation and increased venous capacitance was found to be the critical mechanism necessary to reproduce the simultaneous decrease in both MAP and haematocrit observed in RADAR. These findings indicate that fluid retention with ETA antagonism may not be caused by a direct antidiuretic effect within the kidney but is instead be an adaptive response to venodilation and increased venous capacity, which acutely tends to reduce cardiac filling pressure and cardiac output, and that fluid retention occurs in an attempt to maintain cardiac filling and cardiac output.

Sex-Specific Differences in Kidney Function and Blood Pressure Regulation.

Premenopausal women generally exhibit lower blood pressure and a lower prevalence of hypertension than men of the same age, but these differences reverse postmenopause due to estrogen withdrawal. Sexual dimorphism has been described in different components of kidney physiology and pathophysiology, including the renin-angiotensin-aldosterone system, endothelin system, and tubular transporters. This review explores the sex-specific differences in kidney function and blood pressure regulation. Understanding these differences provides insights into potential therapeutic targets for managing hypertension and kidney diseases, considering the patient's sex and hormonal status.

Therapeutic approaches and novel antifibrotic agents in renal fibrosis: A comprehensive review.

Renal fibrosis (RF) is one of the underlying pathological conditions leading to progressive loss of renal function and end-stage renal disease (ESRD). Over the years, various therapeutic approaches have been explored to combat RF and prevent ESRD. Despite significant advances in understanding the underlying molecular mechanism(s), effective therapeutic interventions for RF are limited. Current therapeutic strategies primarily target these underlying mechanisms to halt or reverse fibrotic progression. Inhibition of transforming growth factor-β (TGF-β) signaling, a pivotal mediator of RF has emerged as a central strategy to manage RF. Small molecules, peptides, and monoclonal antibodies that target TGF-β receptors or downstream effectors have demonstrated potential in preclinical models. Modulating the renin-angiotensin system and targeting the endothelin system also provide established approaches for controlling fibrosis-related hemodynamic changes. Complementary to pharmacological strategies, lifestyle modifications, and dietary interventions contribute to holistic management. This comprehensive review aims to summarize the underlying mechanisms of RF and provide an overview of the therapeutic strategies and novel antifibrotic agents that hold promise in its treatment.

Comprehensive analysis of the endothelin system in the kidneys of mice, rats, and humans.

The intrarenal endothelin (ET) system is an established moderator of kidney physiology and mechanistic contributor to the pathophysiology and progression of chronic kidney disease in humans and rodents. The aim of the present study was to characterize ET system by combining single cell RNA sequencing (scRNA-seq) data with immunolocalization in human and rodent kidneys of both sexes. Using publicly available scRNA-seq data, we assessed sex and kidney disease status (human), age and sex (rats), and diurnal expression (mice) on the kidney ET system expression. In normal human biopsies of both sexes and in rodent kidney samples, the endothelin-converting enzyme-1 (ECE1) and ET-1 were prominent in the glomeruli and endothelium. These data agreed with the scRNA-seq data from these three species, with ECE1/Ece1 mRNA enriched in the endothelium. However, the EDN1/Edn1 gene (encodes ET-1) was rarely detected, even though it was immunolocalized within the kidneys, and plasma and urinary ET-1 excretion are easily measured. Within each species, there were some sex-specific differences. For example, in kidney biopsies from living donors, men had a greater glomerular endothelial cell endothelin receptor B (Ednrb) compared with women. In mice, females had greater kidney endothelial cell Ednrb than male mice. As commercially available antibodies did not work in all species, and RNA expression did not always correlate with protein levels, multiple approaches should be considered to maintain required rigor and reproducibility of the pre- and clinical studies evaluating the intrarenal ET system.

Endothelin and the tumor microenvironment: a finger in every pie.

The tumor microenvironment (TME) plays a central role in the development of cancer. Within this complex milieu, the endothelin (ET) system plays a key role by triggering epithelial-to-mesenchymal transition, causing degradation of the extracellular matrix and modulating hypoxia response, cell proliferation, composition, and activation. These multiple effects of the ET system on cancer progression have prompted numerous preclinical studies targeting the ET system with promising results, leading to considerable optimism for subsequent clinical trials. However, these clinical trials have not lived up to the high expectations; in fact, the clinical trials have failed to demonstrate any substantiated benefit of targeting the ET system in cancer patients. This review discusses the major and recent advances of the ET system with respect to TME and comments on past and ongoing clinical trials of the ET system.

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.

A novel dual inhibitor of the angiotensin and endothelin systems for the treatment of hypertension

Hypertension, affecting nearly half of the US adult population, is a primary cause of morbidity and mortality worldwide. Despite the availability of several classes of antihypertensive medications, only 25% of patients have their blood pressure under control, highlighting the need for novel antihypertensive therapeutics with better effcacy. Among hypertensive cases, salt-sensitive and drug-resistant hypertension are particularly concerning, as they are unresponsive to a combined regimen of three or more classes of medications, including angiotensin II (Ang II) receptor blockers (ARBs), angiotensin-converting enzyme inhibitors (ACEis), and diuretics. Salt-sensitive, observed in 50% of the general and 73% of black hypertensive patients, disproportionately affects the latter, leading to significantly higher mortality. Salt-sensitive hypertension in humans, as well as in various experimental models of hypertension (e.g., Ang II-induced, Dahl-salt sensitive [DSS] rats, deoxycorticosterone acetate [DOCA]-salt hypertensive rats), is characterized by significantly elevated levels of plasma endothelin-1 (ET-1), oxidative stress, and kidney dysfunction. ET-1 is often considered a final common pathway in orchestrating cardiovascular dysfunction through a range of proinflammatory mediators such as Ang II, cytokines, hypoxia, thrombin, reactive oxygen species (ROS), oxidized LDL, and vasopressin, all of which stimulate ET-1 production. In this capacity, we report the discovery of a gut microbiota-derived metabolite, indole-3-acetic acid (IAA), that simultaneously blocks ET-1 receptors (ETAR and ETBR) and the ET-biosynthetic enzyme ECE-1. Our data demonstrate that IAA inhibits ET-1-induced constriction of resistance mesenteric arteries, ROS production in human aortic smooth muscle cells, activation of cultured endothelial cells, adhesion molecule expression, and leukocyte adhesion. IAA inhibited purified human ECE-1 and suppressed Ang-II-induced and hypoxia-elicited ET-1 production from endothelial cells in vitro. Administration of a once-daily, extended-release formulation of IAA inhibits blood pressure elevation and kidney dysfunction in both DSS and Ang II-induced hypertension. IAA treatment preserved endothelial nitric oxide (NO) production and maintained smooth muscle sensitivity to a NO donor, sodium nitroprusside. Furthermore, IAA inhibited the expression of ROS-associated proteins such as Nox2 and Nox4, reduced oxidative damages, and decreased the production of ET-1 in vivo. Overall, IAA is the first compound that, through novel dual targeting of both the angiotensin and endothelin systems, demonstrates profound antihypertensive action in both salt-sensitive and angiotensin II-induced hypertension. Thus, IAA has the potential to effectively treat hypertension that does not respond to conventional therapies. American Heart Association. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Sex Differences of the Endothelin System in the Cardio-Renal Axis of a Lupus Prone Mouse Model

Systemic Lupus Erythematosus (SLE) is the most common form of lupus autoimmunity. It is characterized by overactivation of toll-like receptor 7 (TLR7) and immune complex deposition in target organs including the kidney and vasculature. A lupus diagnosis disproportionately affects women at a rate of 9:1 compared to men. Clinically, patients present with heterogenous symptoms including chronic hypertension, heart failure, renal failure, vascular disease, and neuropathies. Despite a variety of clinical presentations of lupus, elevated endothelin-1 (ET-1) has been detected in both male and female lupus patients' plasma compared to healthy controls. However, the exact sex differences in ET-1 in the development of lupus and its associated cardiovascular complications remain unknown. Therefore, we hypothesized that acceleration of SLE through TLR7 activation promotes sex-dependent regulation of the ET system within the cardiorenal axis. To investigate this, female and male lupus-prone B6.Nba2 mice were treated with a TLR7/8 agonist (R848; 100ug/30ul) or acetone as a control topically twice a week for 4 weeks. After the R848 treatment, mice were followed for 12 more weeks until the 16-week terminal timepoint where the kidney and heart tissues were collected and tissue ET-1, endothelin receptor A (ETA) and endothelin receptor B (ETB) were analyzed by ELISA, RTqPCR, and immunoblotting. At the RNA level, cardiac Ednra expression trended towards upregulation in females, whereas males remained unchanged compared to their respective controls. At the protein level, both sexes tended to decrease ETA receptor levels. Renal Ednra expression trended towards downregulation in females but was unchanged in treated males, which was opposite of renal protein ETA where females were unchanged, and males trended towards reduction. Interestingly, Ednrb and Edn1 trended towards an increase in both the cardiac and renal system in both sexes. However, at the protein level only female cardiac ET-1 was significantly elevated (p&lt;0.0001) while renal ET-1 levels were unchanged. Males demonstrated a significant increase in both cardiac (p=0.0004) and renal ET-1 (p=0.0127). Analysis of female cardiac ETB receptor levels yielded a significant reduction (p=0.0025) and an increasing trend in renal levels. Both cardiac and renal ETB was unchanged in males. The sex differences in the cardiorenal ET system regulation warrants further exploration and possible therapeutic treatments into cardiorenal lupus associated pathologies. Veterans Affairs Biomedical Laboratory Research &amp; Development Career Development Award (CDA-2) 1IK2BX005605-01 to J.P.V.B, Medical University of South Carolina College of Medicine Program Project Grant to and J.P.V.B., and Medical University of South Carolina Core Centers for Clinical Research Project Award P30AR072582 to M.A.C and J.P.V.B. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endothelin-1 Receptor Antagonism Attenuates Increased Uncoupling Protein-1 in Brown Adipose Tissue of Obese Mice

Endothelin-1 (ET-1) is increased in patients and rodent models with obesity and promotes metabolic syndrome by causing inflammation and adipocyte dysfunction. Recently, our laboratory demonstrated that treatment of obese mice with Atrasentan (Atr) and Bosentan (Bos) significantly improved fasting blood glucose, insulin, and glucose and insulin tolerance; however, the mechanisms are not completely understood. Brown adipocytes express all components of the ET-1 system and are important in limiting adiposity though an increase in uncoupling protein-1 (UCP-1) leading to increased metabolism via thermogenesis. We hypothesized that ET-1 antagonism may improve metabolism in obese mice by regulating UCP-1 in brown adipose. Mice were fed either normal (NMD) or high fat diet (HFD) for 10 week and treated with either vehicle, Atr, or Bos for the final two weeks. HFD significantly increased ET-1 and tumor necrosis factor alpha expression in brown adipose tissue compared to NMD controls with no significant effect of either ET-1 receptor antagonists. Interestingly, brown adipose expression of UCP-1 was significantly increased in HFD fed mice compared to NMD, an effect that was significantly attenuated in mice treated with atrasentan and bosentan. These data suggest that ET-1 modulates brown adipose tissue function in obesity, a potential contributor to obesity induced cardio metabolic risk. This work was supported by National Institutes of Health grant 5T32HL105324-14. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endothelin receptor antagonists in diabetic and non-diabetic chronic kidney disease.

Chronic kidney disease (CKD) is one of the major causes of morbidity and mortality, affecting >800 million persons globally. While we still lack efficient, targeted therapies addressing the major underlying pathophysiologic processes in CKD, findings of several recent trials have brought about a shifting landscape of promising therapies. The endothelin system has been implicated in the pathophysiology of CKD and endothelin receptor antagonists are one class of drugs for which we have increasing evidence of efficacy in these patients. In this review we summarize the most recent findings on the safety and efficacy of endothelin receptor antagonists in diabetic and non-diabetic CKD, future directions of research and upcoming treatments.

Unaltered Long-Term Maternal Endothelin System in a Gestational Hypertensive Rat Model

INTRODUCTION: Cardiovascular diseases (CVDs) are two to four times more likely to affect women with a history of hypertensive disorders of pregnancy (HDPs). One of the etiologies of CVDs is endothelial dysfunction, which results from an imbalance in the production of endothelin-1 (ET-1) and nitric oxide (NO). Although blood pressure (BP) is normalized postpartum, we hypothesize that a transient increase in BP during HDPs may cause ongoing endothelial dysfunction. We aimed to discover the impact of HDPs in the development of cardiovascular diseases after long-term postpartum changes in endothelin-A receptor (ETAR) and endothelin-B receptor (ETBR) expression and the concentration of ET-1 and NO. MATERIALS AND METHOD: Twenty-four female Sprague-Dawley (SD) rats were assigned into four groups (n = 6), including two treatment and two control groups. All rats were sacrificed on Day 30 postpartum. The NO and ET-1 concentrations were determined by ELISA and the ETAR and ETBR expression of the mesenteric arteries were measured by immunohistochemistry studies. RESULTS: The mean concentrations of ET-1 and NO were not significantly different in all groups. There was no significant difference in the mean immunoreactivity of ETAR and ETBR percentages area in the tunica intima and media in all groups. CONCLUSION: No evidence demonstrates significant changes in the endothelin system of the resistance arteries at the proteomic level in the long-term duration following HDP. Further investigation of its potential chronic effect warrants a deeper analysis at the molecular and ultrastructural levels.

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.