An endothelium-derived 21-residue vasoconstrictor peptide, endothelin, has been isolated, and shown to be one of the most potent vasoconstrictors known. Cloning and sequencing of preproendothelin complementary DNA shows that mature endothelin is generated through an unusual proteolytic processing, and regional homologies to a group of neurotoxins suggest that endothelin is an endogenous modulator of voltage-dependent ion channels. Expression of the endothelin gene is regulated by several vasoactive agents, indicating the existence of a novel cardiovascular control system.

Three distinct human endothelin-related genes were cloned by screening a genomic DNA library under a low hybridization stringency with a synthetic oligonucleotide probe encoding a portion of the endothelin sequence. Genomic Southern blot analysis with the same oligonucleotide probe showed three corresponding chromosomal loci not only in the human genome but also in porcine and rat genomes. The nucleotide sequences of the three human genes were highly conserved within the regions encoding the 21-residue (mature) endothelins, in spite of the fact that the immediately upstream exon sequences, which encode a part of the propeptides, retained little similarity. Moreover, each of the human genes predicted a putative 21-residue peptide, similar to but distinct from each other: (i) the "classical" endothelin (ET-1), (ii) [Trp6,Leu7]endothelin (ET-2), and (iii) [Thr2,Phe4,Thr5,Tyr6, Lys7,Tyr'4]endothelin . Synthetic ET-1, ET-2, and ET-3 were prepared according to the deduced amino acid sequences, and the biological activities were assayed by contraction of isolated porcine coronary artery strips and by intravenous injection to anesthetized rats. All these synthetic peptides produced strong vasoconstrictor and pressor responses. However, the quantitative profiles of the pharmacological activities were considerably different among the three isopeptides, suggesting the possible existence of endothelin receptor subbpes.Endothelin is a potent vasoconstrictor/pressor peptide originally characterized from the culture supernatant of porcine aortic endothelial cells and consists of 21 amino acid residues with two sets of intrachain disulfide linkages (1). Sequence analysis of cloned cDNAs for porcine (1) and human (2) endothelin precursors showed that endothelin is produced in endothelial cells from an "200-residue prepropeptide much like many peptide hormones and neuropeptides. A presumptive 39-residue (porcine) or 38-residue (human) "big endothelin" is thought to be generated from the preproendothelin; the 21-residue (mature) endothelin is produced through an unusual proteolytic processing of big endothelin between Trp21 and Val22 residues. The amino acid sequences of mature porcine and human endothelin are identical. Preproendothelin mRNA has been detected not only in the cultured endothelial cells but also in porcine aortic endothelium in vivo, and the mRNA expression is markedly influenced by various chemical and mechanical stimuli to the endothelial cells (1, 10). These observations suggest an important role of endothelin in regulation of the mammalian cardiovascular system. In addition to the potent vasoconstrictor and pressor actions, endothelin has been reported to produce a wide spectrum ofbiological effects: regional vasodilatory effects in vivo (3); stimulation of proliferation of vascular smooth muscle cells and fibroblasts (4, 9); contraction of airway and intestinal smooth muscles (5, 6); positive inotropic and chronotropic effects on the myocardium (7, 8); release of icosanoids and/or endothelium-deri...

Endothelin-1 was initially identified as a 21-residue potent vasoconstrictor peptide produced by vascular endothelial cells, but was subsequently found to have many effects on both vascular and non-vascular tissues. The discovery of three isopeptides of the endothelin family, ET-1, ET-2 and ET-3, each possessing a diverse set of pharmacological activities of different potency, suggested the existence of several different endothelin receptor subtypes. Endothelins may elicit biological responses by various signal-transduction mechanisms, including the G protein-coupled activation of phospholipase C and the activation of voltage-dependent Ca2+ channels. Thus, different subtypes of the endothelin receptor may use different signal-transduction mechanisms. Here we report the cloning of a complementary DNA encoding one subtype belonging to the superfamily of G protein-coupled receptors. COS-7 cells transfected with the cDNA express specific and high-affinity binding sites for endothelins, responding to binding by the production of inositol phosphates and a transient increase in the concentration of intracellular free Ca2+. The three endothelin isopeptides are roughly equipotent in displacing 125I-labelled ET-1 binding and causing Ca2+ mobilization. A messenger RNA corresponding to the cDNA is detected in many rat tissues including the brain, kidney and lung but not in vascular smooth muscle cells. These results indicate that this cDNA encodes a 'nonselective' subtype of the receptor which is different from the vascular smooth muscle receptor.

Orexins (hypocretins) are a pair of neuropeptides implicated in energy homeostasis and arousal. Recent reports suggest that loss of orexin-containing neurons occurs in human patients with narcolepsy. We generated transgenic mice in which orexin-containing neurons are ablated by orexinergic-specific expression of a truncated Machado-Joseph disease gene product (ataxin-3) with an expanded polyglutamine stretch. These mice showed a phenotype strikingly similar to human narcolepsy, including behavioral arrests, premature entry into rapid eye movement (REM) sleep, poorly consolidated sleep patterns, and a late-onset obesity, despite eating less than nontransgenic littermates. These results provide evidence that orexin-containing neurons play important roles in regulating vigilance states and energy homeostasis. Orexin/ataxin-3 mice provide a valuable model for studying the pathophysiology and treatment of narcolepsy.

Mammals respond to reduced food availability by becoming more wakeful and active, yet the central pathways regulating arousal and instinctual motor programs (such as food seeking) according to homeostatic need are not well understood. We demonstrate that hypothalamic orexin neurons monitor indicators of energy balance and mediate adaptive augmentation of arousal in response to fasting. Activity of isolated orexin neurons is inhibited by glucose and leptin and stimulated by ghrelin. Orexin expression of normal and ob/ob mice correlates negatively with changes in blood glucose, leptin, and food intake. Transgenic mice, in which orexin neurons are ablated, fail to respond to fasting with increased wakefulness and activity. These findings indicate that orexin neurons provide a crucial link between energy balance and arousal.

Systemic blood pressure is controlled by changes in the resistance of the peripheral vascular bed for example in the mesenteric blood vessels. The tone of peripheral blood vessels is primarily maintained by sympathetic vasoconstrictor nerves. Although vasodilator innervation has been identified in certain isolated elastic arteries, it is not known whether vasodilator nerves contribute to the regulation of the peripheral resistance vessels. We present pharmacological evidence for the existence of nonadrenergic, noncholinergic (NANC) vasodilator nerves in the mesenteric resistance vessel of the rat and that the resistance is controlled by not only sympathetic vasoconstrictor nerves but also NANC vasodilator nerves. We also show that the neurogenic vasodilation was selectively abolished by depleting endogenous calcitonin gene-related peptide (CGRP), a potent vasodilator neuropeptide, from perivascular nerves. This indicates that CGRP is a novel vasodilator neurotransmitter and may play a role in control of the total peripheral resistance of systemic circulation through a local reflex mechanism.

Occlusion of the diseased coronary artery in humans causes acute myocardial infarction, survivors of which have a high risk for the development of chronic heart failure. Cardiac myocytes and vascular endothelial cells produce endothelin-1 (refs 2-4), which increases the contractility of cardiac muscle and of vascular smooth muscle cells. Endothelin-1 also exerts long-term effects such as myocardial hypertrophy, and causes cellular injury in cardiac myocytes. Production of endothelin-1 is markedly increased in the myocardium of rats with heart failure, and acute application of an endothelin-receptor antagonist decreases myocardial contractility in such rats, indicating that myocardial endothelin-1 may help to support contractility of the failing heart. But we report here that the upregulated myocardial endothelin system may contribute to the progression of chronic heart failure, because long-term treatment with an endothelin-receptor antagonist greatly improved the survival of rats with chronic heart failure. This beneficial effect was accompanied by significant amelioration of left ventricular dysfunction and prevention of ventricular remodelling, in which there is usually an increase in the ventricular mass and cavity enlargement of the ventricle.

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