The endothelins comprise three structurally similar 21-amino acid peptides. Endothelin-1 and -2 activate two G-protein coupled receptors, ETA and ETB, with equal affinity, whereas endothelin-3 has a lower affinity for the ETA subtype. Genes encoding the peptides are present only among vertebrates. The ligand-receptor signaling pathway is a vertebrate innovation and may reflect the evolution of endothelin-1 as the most potent vasoconstrictor in the human cardiovascular system with remarkably long lasting action. Highly selective peptide ETA and ETB antagonists and ETB agonists together with radiolabeled analogs have accurately delineated endothelin pharmacology in humans and animal models, although surprisingly no ETA agonist has been discovered. ET antagonists (bosentan, ambrisentan) have revolutionized the treatment of pulmonary arterial hypertension, with the next generation of antagonists exhibiting improved efficacy (macitentan). Clinical trials continue to explore new applications, particularly in renal failure and for reducing proteinuria in diabetic nephropathy. Translational studies suggest a potential benefit of ETB agonists in chemotherapy and neuroprotection. However, demonstrating clinical efficacy of combined inhibitors of the endothelin converting enzyme and neutral endopeptidase has proved elusive. Over 28 genetic modifications have been made to the ET system in mice through global or cell-specific knockouts, knock ins, or alterations in gene expression of endothelin ligands or their target receptors. These studies have identified key roles for the endothelin isoforms and new therapeutic targets in development, fluid-electrolyte homeostasis, and cardiovascular and neuronal function. For the future, novel pharmacological strategies are emerging via small molecule epigenetic modulators, biologicals such as ETB monoclonal antibodies and the potential of signaling pathway biased agonists and antagonists.

New biomarkers of liver injury are required in the clinic and in preclinical pharmaceutical evaluation. Previous studies demonstrate that two liver-enriched microRNAs (miR-122 and miR-192) are promising biomarkers of acetaminophen-induced acute liver injury (APAP-ALI) in mice. We have examined these molecules, for the first time, in humans with APAP poisoning. Serum miR-122 and miR-192 were substantially higher in APAP-ALI patients, compared to healthy controls (median DDCt [25th, 75th percentile]) (miR-122: 1,265 [491, 4,270] and -192 were substantially higher in APAP-ALI patients than CKD patients (miR-122: P < 0.0001; miR-192: P < 0.0004). miR-122 correlated with peak ALT levels in the APAP-ALI cohort (Pearson R 5 0.46, P 5 0.0005), but not with prothrombin time. miR-122 was also raised alongside peak ALT levels in a group of patients with non-APAP ALI. Day 1 serum miR-122 levels were almost 2-fold higher in APAP-ALI patients who satisfied King's College Criteria (KCC), compared to those who did not satisfy KCC, although this did not reach statistical significance (P 5 0.15). Conclusion: This work provides the first evidence for the potential use of miRNAs as biomarkers of human drug-induced liver injury. (HEPATOLOGY 2011;54:1767-1776 T he development of informative biomarkers of drug-induced liver injury (DILI) remains a primary aim in clinical and preclinical settings. The challenge is to develop biomarkers that are stable, that can be rapidly and accurately quantified in standard hospital laboratories, are minimally invasive, tissue specific, and add true diagnostic/prognostic value to detect and monitor the level of a pathogenic insult to the liver.1 The current battery of available biomarkers to assess liver integrity includes circulating protein markers of hepatocellular injury, such as the aminotransferases, markers of liver functional impairment, such as prothrombin time, markers of blood chemistry, and a number of novel mechanistic biomarkers of tissue injury (e.g., cytokeratin-18 and high-mobility group box-1 protein). 2 Deficiencies discovered with current blood-based biomarkers include the unacceptable frequency of false positives/negatives, poor

The incidence of chronic kidney disease (CKD) is increasing worldwide. Cardiovascular disease (CVD) is strongly associated with CKD and constitutes one of its major causes of morbidity and mortality. Treatments that slow the progression of CKD and improve the cardiovascular risk profile of patients with CKD are needed. The endothelins (ET) are a family of related peptides, of which ET-1 is the most powerful endogenous vasoconstrictor and the predominant isoform in the cardiovascular and renal systems. The ET system has been widely implicated in both CVD and CKD. ET-1 contributes to the pathogenesis and maintenance of hypertension and arterial stiffness and more novel cardiovascular risk factors such as oxidative stress and inflammation. Through these, ET also contributes to endothelial dysfunction and atherosclerosis. By reversal of these effects, ET antagonists may reduce cardiovascular risk. In particular relation to the kidney, antagonism of the ET system may be of benefit in improving renal hemodynamics and reducing proteinuria. ET likely also is involved in progression of renal disease, and data are emerging to suggest a synergistic role for ET receptor antagonists with angiotensin-converting enzyme inhibitors in slowing CKD progression.

Chronic kidney disease (CKD) is an increasingly prevalent condition globally and is strongly associated with incident cardiovascular disease (CVD). Hypertension is both a cause and effect of CKD and affects the vast majority of CKD patients. Control of hypertension is important in those with CKD as it leads to slowing of disease progression as well as reduced CVD risk. Existing guidelines do not offer a consensus on optimal blood pressure (BP) targets. Therefore, an understanding of the evidence used to create these guidelines is vital when considering how best to manage individual patients. Non-pharmacological interventions are useful in reducing BP in CKD but are rarely sufficient to control BP adequately. Patients with CKD and hypertension will often require a combination of antihypertensive medications to achieve target BP. Certain pharmacological therapies provide additional BP-independent renoprotective and/or cardioprotective action and this must be considered when instituting therapy. Managing hypertension in the context of haemodialysis and following kidney transplantation presents further challenges. Novel therapies may enhance treatment in the near future. Importantly, a personalised and evidence-based management plan remains key to achieving BP targets, reducing CVD risk and slowing progression of CKD.

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Abstract-Proteinuria is associated with adverse cardiovascular and renal outcomes that are not prevented by current treatments.Endothelin 1 promotes the development and progression of chronic kidney disease and associated cardiovascular disease. We, therefore, studied the effects of selective endothelin-A receptor antagonism in proteinuric chronic kidney disease patients, assessing proteinuria, blood pressure (BP), and arterial stiffness, key independent, surrogate markers of chronic kidney disease progression and cardiovascular disease risk. In a randomized, double-blind, 3-way crossover study, 27 subjects on recommended renoprotective treatment received 6 weeks of placebo, 100 mg once daily of sitaxsentan, and 30 mg once daily of nifedipine long acting. Twenty-four-hour proteinuria, protein:creatinine ratio, 24-hour ambulatory BP, and pulse wave velocity (as a measure of arterial stiffness) were measured at baseline and week 6 of each treatment. In 13 subjects, renal blood flow and glomerular filtration rate were assessed at baseline and week 6 of each period.

H ypertension is the most common risk factor worldwide for cardiovascular morbidity and mortality. 1,2 Currently it is estimated that a quarter of the world's adult population is hypertensive, and this number is projected to increase to Ϸ30% by 2025. 1 Although, there exist a number of drug therapies for hypertension, blood pressure (BP) control to target is still only achieved in Ϸ30% of patients. 3 Over the last 20 years, novel licensed therapies have primarily focused on the renin-angiotensin-aldosterone system. Endothelin (ET) receptor antagonism represents an innovative, but as yet only partially explored, alternative approach in the management of hypertension.A review in Hypertension 10 years ago outlined the potential role that ET-1 may play in the development of hypertension, 4 as proposed by Yanagisawa et al in their original Nature article in 1988. 5 This largely focused on preclinical data because, at that time, there was only 1 published study of ET receptor antagonism in patients with essential hypertension. 6 There were also few data that focused on the relative benefits of selective or mixed ET blockade. Finally, the lack of longer-term data on safety and tolerability for these drugs made their place in the antihypertensive armamentarium unclear. In this review we aim to answer many of these questions and outline some of the key findings in this field from the last decade. Biology of the ET SystemThe ET family consists of three 21-amino acid peptides (ET-1, ET-2, and ET-3) with powerful vasoconstrictor and pressor properties. 7 Of the 3 peptides, ET-1 is the major vascular isoform and of most importance in the cardiovascular system. 8 The gene product is the 212-amino acid prepro-ET-1. This is cleaved to big ET-1, after which an ETconverting enzyme (ECE) catalyzes the generation of the biologically active ET-1 and a C-terminal fragment.ET-1 acts by binding to 2 distinct receptors, the ET A and the ET B receptors (ET A R and ET B R). 9,10 ET receptors are expressed by a wide variety of cells and tissues. Within the vasculature, ET A R and ET B R, located on vascular smooth muscle cells, mediate the vasoconstrictor effects of ET B Rs are also found on vascular endothelial cells, where their activation results in vasodilation mediated mainly by NO. 12,13 In addition, ET B Rs have a major role in the clearance of circulating ET-1. The plasma half-life of ET-1 in health is Ϸ1 minute, 14 with removal through receptor-and nonreceptormediated mechanisms. ET-1 binds to ET B R, with subsequent ligand-receptor complex internalization and intracellular degradation accounting for the majority of clearance, particularly in the pulmonary circulation, 15 although the splanchnic and renal circulations also contribute. 16 Therefore, a reduction in ET B R number, or ET B R blockade, may reduce ET-1 clearance, increasing plasma concentrations without altering production. For this reason and, importantly, because most ET-1 is released albuminally, plasma concentrations of ET-1 do not accurately reflect ET-1 productio...

There have been several global epidemics of chronic kidney disease of unknown etiology (CKDu). Some, such as Itai-Itai disease in Japan and Balkan endemic nephropathy, have been explained, whereas the etiology of others remains unclear. In countries such as Sri Lanka, El Salvador, Nicaragua, and India, CKDu is a major public health problem and causes significant morbidity and mortality. Despite their geographical separation, however, there are striking similarities between these endemic nephropathies. Young male agricultural workers who perform strenuous labor in extreme conditions are the worst affected. Patients remain asymptomatic until end-stage renal failure. Biomarkers of tubular injury are raised, and kidney biopsy shows chronic interstitial nephritis with associated tubular atrophy. In many of these places access to dialysis and transplantation is limited, leaving few treatment options. In this review we briefly describe the major historic endemic nephropathies. We then summarize the epidemiology, clinical features, histology and clinical course of CKDu in Mesoamerica, Sri Lanka, India, Egypt, and Tunisia. We draw comparisons between the proposed etiologies and supporting research. Recognition of the similarities may reinforce the international drive to establish causality and to effect prevention.