Phosphoryl-choline
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Phosphorylcholine (abbreviated ChoP) is the
hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are n ...
polar head group of some
phospholipids Phospholipids are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typi ...
, which is composed of a negatively charged phosphate bonded to a small, positively charged
choline Choline is a cation with the chemical formula . Choline forms various Salt (chemistry), salts, such as choline chloride and choline bitartrate. An essential nutrient for animals, it is a structural component of phospholipids and cell membrane ...
group. Phosphorylcholine is part of the
platelet-activating factor Platelet-activating factor, also known as PAF, PAF-acether or AGEPC (acetyl-glyceryl-ether-phosphorylcholine), is a potent phospholipid activator and mediator of many leukocyte functions, platelet aggregation and degranulation, inflammation, and an ...
; the
phospholipid Phospholipids are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...
phosphatidylcholine Phosphatidylcholines (PC) are a class of phospholipids that incorporate choline as a headgroup. They are a major component of biological membranes and can easily be obtained from a variety of readily available sources, such as egg yolk or soyb ...
and
sphingomyelin Sphingomyelin (SPH, ) is a type of sphingolipid found in animal cell membranes, especially in the membranous myelin sheath that surrounds some nerve cell axons. It usually consists of phosphocholine and ceramide, or a phosphoethanolamine hea ...
, the only phospholipid of the
membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...
that is not built with a glycerol backbone. Treatment of cell membranes, like those of
RBCs Reading Blue Coat School is a co-educational Private schools in the United Kingdom, private day school in Holme Park, Sonning, Berkshire. It is situated beside the River Thames, and was established in 1646 by Richard Aldworth (MP for Reading 1 ...
, by certain enzymes, like some
phospholipase A2 The enzyme phospholipase A2 (EC 3.1.1.4, PLA2, systematic name phosphatidylcholine 2-acylhydrolase) catalyses the cleavage of fatty acids in position 2 of phospholipids, hydrolyzing the bond between the second fatty acid "tail" and the glycero ...
, renders the phosphorylcholine moiety exposed to the external aqueous phase, and thus accessible for recognition by the
immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...
. Antibodies against phosphorylcholine are naturally occurring autoantibodies that are created by CD5+/ B-1 B cells and are referred to as non-pathogenic
autoantibodies An autoantibody is an antibody (a type of protein) produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases (notably lupus erythematosus) are associated with such antibodies. Pr ...
.


Thrombus-resistant stents

In
interventional cardiology Interventional cardiology is a branch of cardiology that deals specifically with the catheter based treatment of structural heart diseases. Andreas Gruentzig is considered the father of interventional cardiology after the development of angioplast ...
, phosphorylcholine is used as a synthetic polymer-based
coating A coating is a covering that is applied to the surface of an object, or substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. powder coatings. Paints ...
, applied to
drug-eluting stents A drug-eluting stent (DES) is a tube made of a mesh-like material used to treat narrowed arteries in medical procedures both mechanically (by providing a supporting scaffold inside the artery) and pharmacologically (by slowly releasing a phar ...
, to prevent the occurrence of
coronary artery The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ of ...
restenosis Restenosis is the recurrence of stenosis, a narrowing of a blood vessel, leading to restricted blood flow. Restenosis usually pertains to an artery or other large blood vessel that has become narrowed, received treatment to clear the blockage, and ...
. The first application of this approach for use of stents evolved from efforts by Hayward, Chapman ''et al.'', who showed that the phosphorylcholine component of the outer surface of the
erythrocyte Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood ce ...
bilayer was non-
thrombogenic Thrombogenicity refers to the tendency of a material in contact with the blood to produce a thrombus, or clot. It not only refers to fixed thrombi but also to emboli, thrombi which have become detached and travel through the bloodstream. Thrombo ...
ity. Until 2002, over 120,000 phosphorylcholine-coated stents have been implanted in patients with no apparent deleterious effect in the long term compared to bare metal stent technologies. ;Phosphorylcholine polymer-based drug-eluting stents Drug-eluting stents (DES) are used by interventional cardiologists, operating on patients with
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), or ischemic heart disease (IHD), is a type of cardiovascular disease, heart disease involving Ischemia, the reduction of blood flow to the cardiac muscle due to a build-up ...
. The stent is inserted into the artery via a
balloon angioplasty Angioplasty, also known as balloon angioplasty and percutaneous transluminal angioplasty, is a minimally invasive endovascular procedure used to widen narrowed or obstructed arteries or veins, typically to treat arterial atherosclerosis. A d ...
. This will dilate the diameter of the coronary artery and keep it fixed in this phase so that more blood flows through the artery without the risk of blood clots (
atherosclerosis Atherosclerosis is a pattern of the disease arteriosclerosis, characterized by development of abnormalities called lesions in walls of arteries. This is a chronic inflammatory disease involving many different cell types and is driven by eleva ...
).A. L. Lewis, P. W. Stratford, A. L. Lewis, R. T. Freeman, L. Hughes, R. P. Redman, L. A. Tolhurst and T. A. Vick, Abstracts of UKSB 1st Annual Conference, July 2000. https://doi.org/10.1023%2FA%3A1012803503667 Retrieved on 2009-02-09 Phosphorylcholine is used as the polymer-based coating of a DES because its molecular design improves surface biocompatibility and lowers the risk of causing inflammation or
thrombosis Thrombosis () is the formation of a Thrombus, blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thrombocytes) and fib ...
. Polymer coatings of stents that deliver the anti-proliferative drug
Zotarolimus Zotarolimus (INN, codenamed ABT-578) is an immunosuppressant. It is a semi-synthetic derivative of sirolimus (rapamycin). It was designed for use in stents with phosphorylcholine as a carrier. Zotarolimus, or ABT-578, was originally used on Abbot ...
to the arterial vessel wall are components of these medical devices. For targeted local delivery of Zotarolimus to the artery, the drug is incorporated into a methacrylate-based copolymer that includes a synthetic form of phosphorylcholine. This use of
biomimicry Biomimetics or biomimicry is the emulation of the models, systems, and elements of nature for the purpose of solving complex human problems. The terms "biomimetics" and "biomimicry" are derived from (''bios''), life, and μίμησις ('' mīm ...
, or the practice of using polymers that occur naturally in biology, provides a coating with minimal thrombus deposition and no adverse clinical effect on late healing of the arterial vessel wall. Not only is the coating non-thrombogenic, but it also exhibits other features that should be present when applying such a material to a medical device for long-term implantation. These include durability, neutrality to the chemistry of the incorporated drug and ability for
sterilization Sterilization may refer to: * Sterilization (microbiology), killing or inactivation of micro-organisms * Soil steam sterilization, a farming technique that sterilizes soil with steam in open fields or greenhouses * Sterilization (medicine) render ...
using standard methods which do not affect drug structure or efficiency


See also

*
Citicoline Citicoline (INN), also known as cytidine diphosphate-choline (CDP-choline) or cytidine 5'-diphosphocholine is an intermediate in the generation of phosphatidylcholine from choline, a common biochemical process in cell membranes. Citicoline is natu ...
*
Acetylcholine Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...


References


External links


Phosphocholine - C5H15NO4P+
at PubChem * {{Acetylcholine receptor modulators Cholinergics Phospholipids