Endothelium-derived ET-1 and the development of renal injury

Chrono-nutrition for hypertension

Despite the advancement in blood pressure (BP) lowering medications, uncontrolled hypertension persists, underscoring a stagnation of effective clinical strategies. Novel and effective lifestyle therapies are needed to prevent and manage hypertension to mitigate future progression to cardiovascular and chronic kidney diseases. Chrono-nutrition, aligning the timing of eating with environmental cues and internal biological clocks, has emerged as a potential strategy to improve BP in high-risk populations. The aim of this review is to provide an overview of the circadian physiology of BP with an emphasis on renal and vascular circadian biology. The potential of Chrono-nutrition as a lifestyle intervention for hypertension is discussed and current evidence for the efficacy of time-restricted eating is presented.

Research progress on the role of ET-1 in diabetic kidney disease

Diabetic kidney disease (DKD) is one of the common complications of diabetes mellitus, which usually progresses to end-stage renal disease and causes great damage to the health of patients. Endothelin-1 (ET-1), a molecule closely associated with the progression of DKD, has increased expression in response to high glucose stimulation and is involved in hemodynamic changes, inflammation, glomerular and tubular dysfunction in the kidney, causing an increase in proteinuria and a decrease in glomerular filtration function, ultimately leading to glomerulosclerosis and renal failure. This paper aims to review the molecular level changes, regulatory mechanisms, and mechanisms of action of ET-1 under DKD, clinical trials of ET-1 receptor antagonists in recent years and current problems, to provide basic information and new research directions and ideas for the treatment of DKD and ET-1-related research.

TSC1 deletion in fibroblasts alleviates lipopolysaccharide-induced acute kidney injury

Mechanistic target of rapamycin complex 1 (mTORC1) signaling is active in inflammation, but its involvement in septic acute kidney injury (AKI) has not been shown. mTORC1 activation (p-S6) in renal fibroblasts was increased in a mouse AKI model induced by 1.5 mg/kg lipopolysaccharide (LPS). Deletion of tuberous sclerosis complex 1 (TSC1), an mTORC1 negative regulator, in fibroblasts (Fibro-TSC1^-/-) inhibited the elevation of serum creatinine and blood urea nitrogen in AKI compared with that in TSC1^fl/fl control mice. Endothelin-1 (EDN1) and phospho-Jun-amino-terminal kinase (p-JNK) were up-regulated in Fibro-TSC1^-/- renal fibroblasts after LPS challenge. Rapamycin, an mTORC1 inhibitor, and bosentan, an EDN1 antagonist, eliminated the difference in renal function between TSC1^fl/fl and Fibro-TSC1^-/- mice after LPS injection. Rapamycin restored LPS-induced up-regulation of EDN1, endothelin converting enzyme-1 (ECE1), and p-JNK in TSC1-knockdown mouse embryonic fibroblasts (MEFs). SP600125, a Jun-amino-terminal kinase (JNK) inhibitor, attenuated LPS-induced enhancement of EDN1 and ECE1 in TSC1-knockdown MEFs without a change in phospho-S6 ribosomal protein (p-S6) level. The results indicate that mTORC1-JNK-dependent up-regulation of ECE1 elevated EDN1 in TSC1-knockout renal fibroblasts and contributed to improvement of renal function in Fibro-TSC1^-/- mice with LPS-induced AKI. Renal fibroblast mTORC1 plays an important role in septic AKI.

High preoperative plasma endothelin-1 levels are associated with increased acute kidney injury risk after pulmonary endarterectomy

OBJECTIVES

The only curative treatment for chronic thromboembolic pulmonary hypertension (CTEPH) is pulmonary endarterectomy (PEA). PEA requires cardiopulmonary bypass (CPB) which is associated with a high acute kidney injury (AKI) risk. Circulating endothelin-1 (ET-1) levels are elevated in CTEPH, and ET-1 plays a pivotal role in AKI. Because AKI is burdened by high morbidity and mortality, we aimed to evaluate the association between preoperative ET-1 and the risk to develop AKI in CTEPH individuals who undergo PEA. We also evaluated the association of AKI and ET-1 with kidney function and mortality at 1 year after PEA.

METHODS

In 385 consecutive patients diagnosed with CTEPH who underwent PEA at the Foundation IRCC Policlinico San Matteo (Pavia, Italy) from January 2009 to April 2015, we assessed preoperative circulating ET-1 by ELISA and identified presence of AKI based on 2012 KDIGO criteria.

RESULTS

AKI occurred in 26.5% of the 347 patients included in the analysis, and was independently associated with preoperative ET-1 (p = 0.008), body mass index (BMI) (p = 0.022), male gender (p = 0.005) and duration of CPB (p = 0.002). At 1-year post PEA, estimated glomerular filtration rate (eGFR) significantly improved in patients who did not develop AKI [ΔeGFR 5.6 ml/min/1.73 m² (95% CI 3.6-7.6), p < 0.001] but not in those with perioperative AKI. AKI (p < 0.001), age (p < 0.001), preoperative eGFR (p < 0.001) and systemic hypertension diagnosis (p = 0.015) were independently associated with 1-year ΔeGFR. Neither perioperative AKI nor preoperative ET-1 was associated with 1-year survival.

CONCLUSION

Perioperative AKI is associated with higher preoperative circulating ET-1 and it negatively influences long-term kidney function in patients with CTEPH who undergo PEA.

Roles of miR-31 and endothelin-1 in psoriasis vulgaris: pathophysiological functions and potential biomarkers

Psoriatic lesions are characterized by hyperproliferation, aberrant differentiation of keratinocytes resistant to apoptosis and inflammation. miR-31 plays pro-proliferative, pro-differentiative and pro-inflammatory roles and modulates apoptosis in psoriatic keratinocytes. Endothelin-1 (ET-1) is produced by psoriatic keratinocytes and suppresses apoptosis. Inflammation increases the production of ET-1, which in turn leads to the chronic stimulation of keratinocyte proliferation. The aim of this study was to identify the putative link between two potential biomarkers (miR-31 and ET-1) in patients with psoriasis. The study design included experimental group (29 patients with psoriasis), and the control group (22 blood donors). The PASI score evaluated the state of the disease (median: 18.6; interquartile range 14.5-20.9). Both, the serum level of ET-1 and the whole blood level of miR-31 were significantly increased (p<0.001 and p<0.05, respectively) in patients compared to the controls. However, a significant negative relationship between ET-1 and miR-31 was observed (Spearman's rho=-037, p=0.05). It is possible that a negative feedback loop will be present between miR-31 and ET-1. Our results indicate that miR-31 and ET-1, potential biomarkers of the disease, play significant roles in the pathophysiology of psoriasis.

Association between Endothelin-1 Levels and Kidney Disease among Blacks

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

Atrasentan for the treatment of diabetic nephropathy

INTRODUCTION

Endothelin-1 (ET-1) is the most potent vasoconstrictor, and is involved in the renal regulation of salt and water homeostasis. When produced in excess in the kidney, ET-1 promotes proteinuria and tubulointerstitial injury. There is great interest in the clinical use of endothelin receptor antagonists (ERAs) in chronic kidney disease (CKD), mainly in diabetic nephropathy (DN). Areas covered: Physiopathological actions of ET-1 on the kidney. Both dual ETAR/ET_BR (bosentan) or ET_AR specific endothelin antagonists (avosentan and atrasentan, among others), which have progressed to early clinical development, with particular emphasis on atrasentan. Expert opinion: Different phase I and II clinical trials with ERAs in DN, mostly with atrasentan, have shown that these drugs have a marked anti-proteinuric effect on residual proteinuria when administered as add-on therapy in addition to ACEi or ARAII treatment. In the past few years, a series of randomized controlled trials investigating new approaches to DN have provided negative or inconclusive data, or even were terminated due to safety concerns or lack of efficacy. Therefore, we eagerly but cautiously await the results of the ongoing SONAR trial with atrasentan in more than 4,000 patients including assessment of renal and cardiovascular hard-end points (estimated primary completion date, July 2018).

Long-Term Endothelin-A Receptor Antagonism Provides Robust Renal Protection in Humanized Sickle Cell Disease Mice

Sickle cell disease (SCD)-associated nephropathy is a major source of morbidity and mortality in patients because of the lack of efficacious treatments targeting renal manifestations of the disease. Here, we describe a long-term treatment strategy with the selective endothelin-A receptor (ET_A) antagonist, ambrisentan, designed to interfere with the development of nephropathy in a humanized mouse model of SCD. Ambrisentan preserved GFR at the level of nondisease controls and prevented the development of proteinuria, albuminuria, and nephrinuria. Microscopy studies demonstrated prevention of podocyte loss and structural alterations, the absence of vascular congestion, and attenuation of glomerulosclerosis in treated mice. Studies in isolated glomeruli showed that treatment reduced inflammation and oxidative stress. At the level of renal tubules, ambrisentan treatment prevented the increased excretion of urinary tubular injury biomarkers. Additionally, the treatment strategy prevented tubular brush border loss, diminished tubular iron deposition, blocked the development of interstitial fibrosis, and prevented immune cell infiltration. Furthermore, the prevention of albuminuria in treated mice was associated with preservation of cortical megalin expression. In a separate series of identical experiments, combined ET_A and ET_B receptor antagonism provided only some of the protection observed with ambrisentan, highlighting the importance of exclusively targeting the ET_A receptor in SCD. Our results demonstrate that ambrisentan treatment provides robust protection from diverse renal pathologies in SCD mice, and suggest that long-term ET_A receptor antagonism may provide a strategy for the prevention of renal complications of SCD.

Endothelin-1 and the kidney: new perspectives and recent findings

PURPOSE OF REVIEW

The role of endothelin-1 (ET-1) in the kidney has been under study for many years; however, the complex mechanisms by which endothelin controls the physiology/pathophysiology of this organ are not fully resolved. This review aims to summarize recent findings in the field, especially regarding glomerular and tubular damage, Na/water homeostasis and sex differences in ET-1 function.

RECENT FINDINGS

Podocytes have been recently identified as a target of ET-1 in the glomerular filtration barrier via ETA receptor activation. Activation of the ETA receptor by ET-1 leads to renal tubular damage by promoting endoplasmic reticulum stress and apoptosis in these cells. In addition, high flow rates in the nephron in response to high salt intake induce ET-1 production by the collecting ducts and promote nitric oxide-dependent natriuresis through epithelial sodium channel inhibition. Recent evidence also indicates that sex hormones regulate the renal ET-1 system differently in men and women, with estrogen suppressing renal ET-1 production and testosterone upregulating that production.

SUMMARY

Based on the reports reviewed in here, targeting of the renal endothelin system is a possible therapeutic approach against the development of glomerular injury. More animal and clinical studies are needed to better understand the dimorphic control of this system by sex hormones.