Endothelins are peptides with

receptor Receptor may refer to: * Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ...

s and effects in many body organs. Endothelin constricts blood vessels and raises blood pressure. The endothelins are normally kept in balance by other mechanisms, but when overexpressed, they contribute to high blood pressure (

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

heart disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...

, and potentially other diseases. Endothelins are 21-

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

vasoconstricting Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A ...

s produced primarily in the

endothelium The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...

having a key role in vascular homeostasis. Endothelins are implicated in vascular diseases of several organ systems, including the heart, lungs, kidneys, and brain. As of 2018, endothelins remain under extensive

basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

and

clinical research Clinical research is a branch of healthcare science that determines the safety and effectiveness ( efficacy) of medications, devices, diagnostic products and treatment regimens intended for human use. These may be used for prevention, treatm ...

to define their roles in several organ systems.

Etymology

Endothelins derived the name from their isolation in cultured

endothelial cell The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...

Isoforms

There are three

isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...

s of the peptide (identified as ET-1, -2, -3), each encoded by a separate gene, with varying regions of expression and binding to at least four known

endothelin receptor There are at least four known endothelin receptors, ETA, ETB1, ETB2 and ETC, all of which are G protein-coupled receptors whose activation result in elevation of intracellular-free calcium, which constricts the smooth muscles of the blood vessels ...

s, ET_A, ET_B1, ET_B2 and ET_C. The human

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

s for endothelin-1 (ET-1), endothelin-2 (ET-2), and endothelin-3 (ET-3) are located on

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

s 6, 1, and 20, respectively.

Mechanism of action and function

Endothelin functions through activation of two

G protein G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their act ...

-coupled receptors, endothelin_A and endothelin_B receptor (ETA and ETB, respectively). These two subtypes of endothelin receptor are distinguished in the laboratory by the order of their affinity for the three endothelin peptides: the ETA receptor is selective for ET-1, whereas the ETB receptor has the same affinity for all three ET peptides. The two types of ET receptor are distributed across diverse cells and

organs In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a f ...

, but with different levels of expression and activity, indicating a multiple-organ ET system.

Endothelin-1 Endothelin 1 (ET-1), also known as preproendothelin-1 (PPET1), is a potent Vasoconstriction, vasoconstrictor peptide produced by vascular endothelium, endothelial cells. The protein encoded by this gene ''EDN1'' is proteolysis, proteolytically pr ...

is the most powerful

endogenous Endogenous substances and processes are those that originate from within a living system such as an organism, tissue, or cell. In contrast, exogenous substances and processes are those that originate from outside of an organism. For example, es ...

chemical affecting vascular tone across organ systems. Secretion of endothelin-1 from the vascular

signals vasoconstriction and influences local cellular growth and survival. ET-1 has been implicated in the development and progression of several

cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...

s, such as

atherosclerosis Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...

and

. Endothelin also has roles in

mitogenesis A mitogen is a small bioactive protein or peptide that induces a cell to begin cell division, or enhances the rate of division (mitosis). Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. The mechanism of action of a ...

, cell survival,

angiogenesis Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splitting ...

, bone growth,

nociceptor A nociceptor ("pain receptor" from Latin ''nocere'' 'to harm or hurt') is a sensory neuron that responds to damaging or potentially damaging stimuli by sending "possible threat" signals to the spinal cord and the brain. The brain creates the sens ...

function, and cancer onset mechanisms. Clinically, anti-ET drugs are used to treat pulmonary arterial hypertension.

Physiological effects

Endothelins are the most potent vasoconstrictors known. Overproduction of endothelin in the lungs may cause pulmonary hypertension, which was treatable in preliminary research by

bosentan Bosentan, sold under the brand name Tracleer and Safebo among others, is a dual endothelin receptor antagonist medication used in the treatment of pulmonary artery hypertension (PAH). Bosentan is available as film-coated tablets (62.5 mg o ...

sitaxentan Sitaxentan sodium (TBC-11251) is a medication for the treatment of pulmonary arterial hypertension (PAH). It was marketed as Thelin by Encysive Pharmaceuticals until Pfizer purchased Encysive in February 2008. In 2010, Pfizer voluntarily remove ...

ambrisentan Ambrisentan (U.S. trade name Letairis; E.U. trade name Volibris; India trade name Pulmonext by MSN labs) is a drug indicated for use in the treatment of pulmonary hypertension. The peptide endothelin constricts muscles in blood vessels, incr ...

. Endothelins have involvement in cardiovascular function, fluid-

electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

homeostasis In biology, homeostasis (British English, British also homoeostasis) Help:IPA/English, (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physics, physical, and chemistry, chemical conditions maintained by organism, living systems. Thi ...

, and neuronal mechanisms across diverse cell types. Endothelin receptors are present in the three pituitary lobes which display increased metabolic activity when exposed to ET-1 in the blood or ventricular system. ET-1 contributes to the vascular dysfunction associated with cardiovascular disease, particularly

and

. The ET_A receptor for ET-1 is primarily located on vascular smooth muscle cells, mediating vasoconstriction, whereas the ET_B receptor for ET-1 is primarily located on endothelial cells, causing vasodilation due to

nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its che ...

release. The binding of

platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ini ...

s to the

receptor

LOX-1 Oxidized low-density lipoprotein receptor 1 (Ox-LDL receptor 1) also known as lectin-type oxidized LDL receptor 1 (LOX-1) is a protein that in humans is encoded by the ''OLR1'' gene. LOX-1 is the main receptor for oxidized LDL on endothelium, endo ...

causes a release of endothelin, which induces

endothelial dysfunction In vascular diseases, endothelial dysfunction is a systemic pathological state of the endothelium. Along with acting as a semi-permeable membrane, the endothelium is responsible for maintaining vascular tone and regulating oxidative stress by rel ...

Clinical significance

The ubiquitous distribution of endothelin peptides and receptors implicates involvement in a wide variety of physiological and pathological processes among different

organ systems An organ system is a biological system consisting of a group of organs that work together to perform one or more functions. Each organ has a specialized role in a plant or animal body, and is made up of distinct tissues. Plants Plants have ...

. Among numerous diseases potentially occurring from endothelin dysregulation are: * several types of

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

* cerebral

vasospasm Vasospasm refers to a condition in which an arterial spasm leads to vasoconstriction. This can lead to tissue ischemia and tissue death (necrosis). Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or de ...

following

subarachnoid hemorrhage Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain. Symptoms may include a severe headache of rapid onset, vomiting, decreased level of consci ...

arterial hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

, pulmonary hypertension, and other

cardiovascular The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

disorders *

pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...

mediation *

cardiac hypertrophy Ventricular hypertrophy (VH) is thickening of the walls of a ventricle (lower chamber) of the heart. Although left ventricular hypertrophy (LVH) is more common, right ventricular hypertrophy (RVH), as well as concurrent hypertrophy of both ventri ...

and

heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...

Dengue haemorrhagic fever Dengue fever is a mosquito-borne disease, mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, myalgia, muscle and art ...

Type II diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...

*some cases of

Hirschsprung disease Hirschsprung's disease (HD or HSCR) is a birth defect in which nerves are missing from parts of the intestine. The most prominent symptom is constipation. Other symptoms may include vomiting, abdominal pain, diarrhea and slow growth. Symptoms usu ...

insulin resistance Insulin resistance (IR) is a pathological condition in which cell (biology), cells fail to respond normally to the hormone insulin. Insulin is a hormone that facilitates the transport of glucose from blood into cells, thereby reducing blood gluco ...

the high levels of blood insulin results in increased production and activity of ET-1, which promotes vasoconstriction and elevates

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...

. ET-1 impairs glucose uptake in the skeletal muscles of insulin resistant subjects, thereby worsening

. In preliminary research, injection of endothelin-1 into a lateral cerebral ventricle was shown to potently stimulate

glucose metabolism Carbohydrate metabolism is the whole of the biochemical processes responsible for the metabolic formation, breakdown, and interconversion of carbohydrates in living organisms. Carbohydrates are central to many essential metabolic pathways. Plants ...

in specified interconnected circuits of the brain, and to induce

convulsion A convulsion is a medical condition where the body muscles contract and relax rapidly and repeatedly, resulting in uncontrolled shaking. Because epileptic seizures typically include convulsions, the term ''convulsion'' is sometimes used as a s ...

s, indicating its potential for diverse neural effects in conditions such as

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical ...

. Receptors for endothelin-1 exist in brain

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...

s, indicating a potential role in neural functions.

Antagonists

Earliest antagonists discovered for ET_A were BQ123, and for ET_B, BQ788. An ET_A-selective antagonist,

was approved for treatment of pulmonary arterial hypertension in 2007, followed by a more selective ET_A antagonist,

, which was later withdrawn due to potentially lethal effects in the liver.

Bosentan Bosentan, sold under the brand name Tracleer and Safebo among others, is a dual endothelin receptor antagonist medication used in the treatment of pulmonary artery hypertension (PAH). Bosentan is available as film-coated tablets (62.5 mg o ...

was a precursor to

macitentan Macitentan, sold under the brand name Opsumit, is an endothelin receptor antagonist (ERA) developed by Actelion and approved for the treatment of pulmonary arterial hypertension (PAH). The other two ERAs marketed as of 2014 are bosentan and am ...

, which was approved in 2013.

References

External links

* {{Authority control Peptide hormones Hormones of the blood vessels