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In the past three decades, endothelin and endothelin receptor antagonists have received great scientific and clinical interest, leading to the publication of more than 27,000 scientific articles since its discovery. The Thirteenth International Conference on Endothelin (ET-13) was held on September 8-11, 2013, at Tokyo Campus of the University of Tsukuba in Japan. Close to 300 scientists from 25 countries from around the world came to Tokyo to celebrate the anniversary of the discovery of the endothelin peptide discovered 25 years ago at the University of Tsukuba. This article summarizes some of the highlights of the conference, the anniversary celebration ceremony, and particularly the participation of next generation of endothelin researchers in endothelin science and the anniversary celebration. As a particular highlight, next generation endothelin researchers wrote a haiku (a traditional form of Japanese poetry originating from consisting of no more than three short verses and 27 on, or Japanese phonetic units) to describe the magic of endothelin science which they presented to the conference audience at the anniversary ceremony. The text of each haiku - both in its original language together with the English translation - is part of this article providing in an exemplary fashion how poetry can be bridged with science. Finally, we give an outlook towards the next 25 years of endothelin research.

Aims Hypertensive patients develop cardiac hypertrophy and fibrosis with increased stiffness, contractile deficit and altered perfusion. Angiotensin II (AngII) is an important factor in the promotion of this pathology. The effects of AngII are partly mediated by endothelin-1 (ET-1) and transforming growth factor-β. The exact feature of these pathways and the intercellular communications involved remain unclear. In this study, we explored the role of endothelial cell-derived ET-1 in the development of AngII-induced cardiac fibrosis and hypertrophy. Main methods We used mice with vascular endothelial cell specific ET-1 deficiency (VEETKO) and their wild type littermates (WT). Mice were infused for one week with AngII (3.2 mg/kg/day, n = 12) or vehicle (0.15 mol/L NaCl and 1 mmol/L acetic acid, n = 5), using subcutaneous mini-pumps. Hearts were stained with hematoxylin–eosin and masson's trichrome for histology. Cardiac gene expression and protein abundance were measured by Northern Blot, real time PCR and Western Blot. Key findings AngII-induced cardiac hypertrophy, interstitial and perivascular fibrosis were less pronounced in VEETKO mice compared to WT. Blood pressure increased similarly in both genotypes. Expression of connective tissue growth factor, tumor growth factor-β, collagen I and III in response to AngII required endothelial ET-1. Endothelial ET-1 was also necessary to the elevation in protein kinase C δ abundance and ERK1/2 activation. AngII-induced elevation in PKCe abundance was however ET-1 independent. Significance This study underscores the significance of ET-1 from the vasculature in the process of AngII-induced cardiac hypertrophy and fibrosis, independently from blood pressure. Endothelial ET-1 represents therefore a possible pharmacological target.

Background The cardiac nitric oxide and endothelin-1 (ET-1) systems are closely linked and play a critical role in cardiac physiology. The balance between both systems is often disturbed in cardiovascular diseases. To define the cardiac effect of excessive ET-1 in a status of nitric oxide deficiency, we compared left ventricular function and morphology in wild-type mice, ET-1 transgenic (ET+/+) mice, endothelial nitric oxide synthase knockout (eNOS(-/-)) mice, and ET(+/+)eNOS(-/-) mice. Methods and results eNOS(-/-) and ET(+/+)eNOS(-/-) mice developed high blood pressure compared with wild-type and ET+/+ mice. Left ventricular catheterization showed that eNOS(-/-) mice, but not ET(+/+)eNOS(-/-), developed diastolic dysfunction characterized by increased end-diastolic pressure and relaxation constant tau. To elucidate the causal molecular mechanisms driving the rescue of diastolic function in ET(+/+)eNOS(-/-) mice, the cardiac proteome was analyzed. Two-dimensional gel electrophoresis coupled to mass spectrometry offers an appropriate hypothesis-free approach. ET-1 overexpression on an eNOS(-/-) background led to an elevated abundance and change in posttranslational state of antioxidant enzymes (e. g., peroxiredoxin-6, glutathione S-transferase mu 2, and heat shock protein beta 7). In contrast to ET(+/+)eNOS(-/-) mice, eNOS(-/-) mice showed an elevated abundance of proteins responsible for sarcomere disassembly (e. g., cofilin-1 and cofilin-2). In ET(+/+)eNOS(-/-) mice, glycolysis was favored at the expense of fatty acid oxidation. Conclusion eNOS(-/-) mice developed diastolic dysfunction; this was rescued by ET-1 transgenic overexpression. This study furthermore suggests that cardiac ET-1 overexpression in case of eNOS deficiency causes specifically the regulation of proteins playing a role in oxidative stress, myocytes contractility, and energy metabolism.

Activation of the endothelin (ET) system promotes vasoconstriction, inflammation, and fibrosis in various tissues, including the lung. Therefore, ET-1 transgenic mice overexpressing ET-1 develop pulmonary fibrosis in a slow, age-dependent manner. In vivo, NO is the most important counterregulatory mediator of the ET system and decreases ET-1 promoter activity. The aim of our study was to elucidate the impact on pulmonary inflammation and fibrosis of the interaction between NO and the ET system in young ET-1 transgenic mice before the onset of pulmonary fibrosis. Male ET-1 transgenic mice and wild-type littermates at the age of 8 weeks were randomly allocated to the following 6 groups: WT (n = 11), wild-type animals without treatment; WT + l-NAME (n = 14), wild-type animals receiving l-NAME, an inhibitor of NO synthase; WT + l-NAME + LU (n = 13), wild-type animals receiving l-NAME and LU 302872, a dual ETA/ETB-receptor antagonist; ET1tg (n = 10), ET-1 transgenic mice; ET1tg + l-NAME (n = 13); and ET1tg + l-NAME + LU (n = 13). After 6 weeks, animals were euthanized, and hearts and lungs were harvested for histology and immunohistochemistry. No differences in pulmonary inflammation, as indicated by macrophage infiltration, or in interstitial fibrosis were observed between WT and ET1tg mice at baseline; however, inflammation and interstitial fibrosis were significantly enhanced in ET1tg mice, but not in WT groups, after l-NAME treatment. The combined ETA/ETB-receptor antagonist LU 302872 abolished inflammation and interstitial fibrosis in l-NAME-treated ET1tg mice. Perivascular fibrosis and media/lumen ratio of pulmonary bronchi and arteries did not differ between all study groups. In our study l-NAME induced pulmonary fibrosis and inflammation only in young ET1tg mice. Additional treatment with LU 302872 abolished these effects. We thus conclude that an imbalance between an activated ET system and a suppressed NO system contributes to pulmonary inflammation and fibrosis.

Background and purpose: Myocardial fibrosis is an unwanted effect associated with chronic renal failure. The adenosine system is involved in cardiac and renal function. Therefore, we investigated the novel selective adenosine A1 receptor antagonist SLV320 focusing on its potential in preventing cardiomyopathy in rats with 5/6 nephrectomy.

It has recently been established that a high salt diet leads to sodium storage within the skin of rats and mice. This increase in sodium in the highly vascularized skin results in macrophage infiltration and lymphangiogenesis. While dysfunction in this process has been implicated in salt sensitive hypertension, the mechanisms are poorly understood. Because vascular endothelin-1 (ET-1) is upregulated in response to a high salt diet or hypertonicity, and is a potent chemoattractant, we hypothesized that endothelial derived ET-1 mediates infiltration of immune cells into the skin during chronic high salt intake, thereby allowing sodium clearance from the skin and preventing accumulation. Our data indicate that increasing extracellular concentration of human endothelial cells by 40 mOsm with NaCl, similar to what is seen in the interstitial space of rats placed on a high salt diet, leads to a 50% increase in ET-1 production, a mechanism likely mediated by TonEBP. Furthermore, in response to one week of high salt diet, skin Na/water ratio was elevated in vascular endothelial cell ET-1 knockout mice compared to wild type mice (0.112 ± 0.007 vs. 0.096 ± 0.004 mmol/ml). These data suggest a critical role for ET-1 in preventing the accumulation of sodium in the skin during a high salt intake, an emerging mechanism of the body's ability to buffer blood pressure changes in response to increases in sodium intake.

Background Endothelin-1 participates in the pathophysiology of heart failure. The reasons for the lack of beneficial effect of endothelin antagonists in heart failure patients remain however speculative. The anti-apoptotic properties of ET-1 on cardiomyocytes could be a reasonable explanation. We therefore hypothesized that blocking the pro-apoptotic TNF-α pathway using pentoxifylline could prevent the deleterious effect of the lack of ET-1 in a model for heart failure. Methods We performed transaortic constriction (TAC) in vascular endothelial cells specific ET-1 deficient (VEETKO) and wild type (WT) mice (n = 5–9) and treated them with pentoxifylline for twelve weeks. Results TAC induced a cardiac hypertrophy in VEETKO and WT mice but a reduction of fractional shortening could be detected by echocardiography in VEETKO mice only. Cardiomyocyte diameter was significantly increased by TAC in VEETKO mice only. Pentoxifylline treatment prevented cardiac hypertrophy and reduction of fractional shortening in VEETKO mice but decreased fractional shortening in WT mice. Collagen deposition and number of apoptotic cells remained stable between the groups as did TNF-α, caspase-3 and caspase-8 messenger RNA expression levels. TAC surgery enhanced ANP, BNP and bcl2 expression. Pentoxifylline treatment reduced expression levels of BNP, bcl2 and bax. Conclusions Lack of endothelial ET-1 worsened the impact of TAC-induced pressure overload on cardiac function, indicating the crucial role of ET-1 for normal cardiac function under stress. Moreover, we put in light a TNF-α-independent beneficial effect of pentoxifylline in the VEETKO mice suggesting a therapeutic potential for pentoxifylline in a subpopulation of heart failure patients at higher risk.

Background Vascular calcification accompanying chronic kidney disease increases the mortality and morbidity associated with cardiovascular disorders, but no effective therapy is available. We hypothesized that glycosaminoglycans may contribute to osteoblastic differentiation of vascular smooth muscle cells during vascular calcification. Methods and Results We used exostosin‐like glycosyltranferase 2–deficient ( EXTL 2 knockout) mice expressing high levels of glycosaminoglycans in several organs including the aorta. We performed 5/6 subtotal nephrectomy and fed the mice a high‐phosphate diet to induce chronic kidney disease. Overexpression of glycosaminoglycans in the aorta enhanced aortic calcification in chronic kidney disease in EXTL 2 knockout mice. Ex vivo and in vitro, matrix mineralization in aortic rings and vascular smooth muscle cells of EXTL 2 knockout mice was augmented. Furthermore, removal of glycosaminoglycans in EXTL 2 knockout and wild‐type mice‐derived vascular smooth muscle cells effectively suppressed calcium deposition in a high‐phosphate environment. Conclusions These results illustrate an important role for glycosaminoglycans in the development of vascular calcification. Manipulation of glycosaminoglycan expression may have beneficial effects on the progression of vascular calcification in chronic kidney disease patients.

The therapeutic implications of the actions of endothelin (ET)-1 upon renal and cardiovascular function are evident. Among other diseases, ET-1 is recognized to be involved in hypertension and renal failure and, in a rush to develop novel treatments, has been extensively studied. However, given the broad localization of the two receptors (ET(A) and ET(B)) and the diverse effects resulting from their activation, analysis of the role of ET-1 in kidney-regulated blood pressure remains complicated. Moreover, the actions of ET-1 depend upon the cell type and physiological situation. To add to the complexity, both receptors often activate opposing signaling pathways within a single cell. Thus, until recently, reliable insights into the respective involvement of both receptors in the physiology and pathology of the kidney were eagerly awaited. These have been obtained using mice that are genetically modified for different members of the ET system. In this article, the molecular biology of ET-1 and its receptors in the control of renal vasculature tonicity, glomerular function, and management of water and salt reabsorption is discussed. The role of renal ET-1 in the context of blood pressure regulation will be discussed, and the potential of utilizing ET receptor antagonism in the treatment and prevention of glomerular and proteinuric diseases is also outlined.

The therapeutic implications of the actions of endothelin (ET)-1 upon renal and cardiovascular function are evident. Among other diseases, ET-1 is recognized to be involved in hypertension and renal f

Liver cirrhosis is often complicated by an impaired renal excretion of water and sodium. Diuretics tend to further deteriorate renal function. It is unknown whether chronic selective adenosine A(1) receptor blockade, via inhibition of the hepatorenal reflex and the tubuloglomerular feedback, might exert diuretic and natriuretic effects without a reduction of the glomerular filtration rate. In healthy animals intravenous treatment with the novel A(1) receptor antagonist SLV329 resulted in a strong dose-dependent diuretic (up to 3.4-fold) and natriuretic (up to 13.5-fold) effect without affecting creatinine clearance. Male Wistar rats with thioacetamide-induced liver cirrhosis received SLV329, vehicle or furosemide for 12 weeks. The creatinine clearance of cirrhotic animals decreased significantly (-36.5%, p < 0.05), especially in those receiving furosemide (-41.9%, p < 0.01). SLV329 was able to prevent this decline of creatinine clearance. Mortality was significantly lower in cirrhotic animals treated with SLV329 in comparison to animals treated with furosemide (17% vs. 54%, p < 0.05). SLV329 did not relevantly influence the degree of liver fibrosis, kidney histology or expression of hepatic or renal adenosine receptors. In conclusion, chronic treatment with SLV329 prevented the decrease of creatinine clearance in a rat model of liver cirrhosis. Further studies will have to establish whether adenosine A(1) receptor antagonists are clinically beneficial at different stages of liver cirrhosis.

Genetically modified animal models are an important part of medical research. By inducing conditions similar to human diseases in animals, pathophysiologic hypotheses and therapeutic strategies can be tested and evaluated.

Activation of the endothelin (ET) system promotes vasoconstriction, inflammation, and fibrosis in various tissues, including the lung. Therefore, ET-1 transgenic mice overexpressing ET-1 develop pulmonary fibrosis in a slow, age-dependent manner. In vivo, NO is the most important counterregulatory mediator of the ET system and decreases ET-1 promoter activity. The aim of our study was to elucidate the impact on pulmonary inflammation and fibrosis of the interaction between NO and the ET system in young ET-1 transgenic mice before the onset of pulmonary fibrosis. Male ET-1 transgenic mice and wild-type littermates at the age of 8 weeks were randomly allocated to the following 6 groups: WT (n = 11), wild-type animals without treatment; WT + L-NAME (n = 14), wild-type animals receiving L-NAME, an inhibitor of NO synthase; WT + L-NAME + LU (n = 13), wild-type animals receiving L-NAME and LU 302872, a dual ETA/ETB-receptor antagonist; ET1tg (n = 10), ET-1 transgenic mice; ET1tg + L-NAME (n = 13); and ET1tg + L-NAME + LU (n = 13). After 6 weeks, animals were euthanized, and hearts and lungs were harvested for histology and immunohistochemistry. No differences in pulmonary inflammation, as indicated by macrophage infiltration, or in interstitial fibrosis were observed between WT and ET1tg mice at baseline; however, inflammation and interstitial fibrosis were significantly enhanced in ET1tg mice, but not in WT groups, after L-NAME treatment. The combined ETA/ETB-receptor antagonist LU 302872 abolished inflammation and interstitial fibrosis in L-NAME-treated ET1tg mice. Perivascular fibrosis and media/lumen ratio of pulmonary bronchi and arteries did not differ between all study groups. In our study L-NAME induced pulmonary fibrosis and inflammation only in young ET1tg mice. Additional treatment with LU 302872 abolished these effects. We thus conclude that an imbalance between an activated ET system and a suppressed NO system contributes to pulmonary inflammation and fibrosis.

Background: Uremic cardiomyopathy contributes substantially to mortality in chronic kidney disease (CKD) patients. Glucagon-like peptide-1 (GLP-1) may improve cardiac function, but is mainly degraded by dipeptidyl peptidase-4 (DPP-4). Methodology/Principal Findings: In a rat model of chronic renal failure, 5/6-nephrectomized [5/6N] rats were treated orally with DPP-4 inhibitors (linagliptin, sitagliptin, alogliptin) or placebo once daily for 4 days from 8 weeks after surgery, to identify the most appropriate treatment for cardiac dysfunction associated with CKD. Linagliptin showed no significant change in blood level AUC(0-infinity) in 5/6N rats, but sitagliptin and alogliptin had significantly higher AUC(0-infinity) values; 41% and 28% (p=0.0001 and p=0.0324), respectively. No correlation of markers of renal tubular and glomerular function with AUC was observed for linagliptin, which required no dose adjustment in uremic rats. Linagliptin 7 mu mol/kg caused a 2-fold increase in GLP-1 (AUC 201.0 ng/l*h) in 5/6N rats compared with sham-treated rats (AUC 108.6 ng/l*h) (p=0.01). The mRNA levels of heart tissue fibrosis markers were all significantly increased in 5/6N vs control rats and reduced/normalized by linagliptin. Conclusions/Significance: DPP-4 inhibition increases plasma GLP-1 levels, particularly in uremia, and reduces expression of cardiac mRNA levels of matrix proteins and B-type natriuretic peptides (BNP). Linagliptin may offer a unique approach for treating uremic cardiomyopathy in CKD patients, with no need for dose-adjustment.

Endothelin-1 (ET-1) is a multifunctional hormone which regulates the physiology of the cardiovascular and renal systems. ET-1 modulates cardiac contractility, systemic and renal vascular resistance, salt and water renal reabsorption, and glomerular function. ET-1 is responsible for a variety of cellular events: contraction, proliferation, apoptosis, etc. These effects take place after the activation of the two endothelin receptors ETA and ETB, which are present – among others – on cardiomyocytes, fibroblasts, smooth muscle and endothelial cells, glomerular and tubular cells of the kidney. The complex and numerous intracellular pathways, which can be contradictory in term of functional response depending on the receptor type, cell type and physiological situation, are described in this review. Many diseases share an enhanced ET-1 expression as part of the pathophysiology. However, the use of endothelin blockers is currently restricted to pulmonary arterial hypertension, and more recently to digital ulcer. The complexity of the endothelin system does not facilitate the translation of the molecular knowledge to clinical applications. Endothelin antagonists can prevent disease development but secondary undesirable effects limit their usage. Nevertheless, the increasing understanding of the effects of ET-1 on the cardiac and renal physiology maintains the endothelin system as a promising therapeutic target.