Prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase) (The
HUGO
Hugo or HUGO may refer to:
Arts and entertainment
* ''Hugo'' (film), a 2011 film directed by Martin Scorsese
* Hugo Award, a science fiction and fantasy award named after Hugo Gernsback
* Hugo (franchise), a children's media franchise based on ...
official symbol is PTGS2; HGNC ID, HGNC:9605), also known as cyclooxygenase-2 or COX-2, is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
that in humans is encoded by the ''PTGS2''
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 b ...
.
In humans it is one of two
cyclooxygenase
Cyclooxygenase (COX), officially known as prostaglandin-endoperoxide synthase (PTGS), is an enzyme (specifically, a family of isozymes, ) that is responsible for formation of prostanoids, including thromboxane and prostaglandins such as pr ...
s. It is involved in the conversion of
arachidonic acid to
prostaglandin H2
Prostaglandin H2 is a type of prostaglandin and a precursor for many other biologically significant molecules. It is synthesized from arachidonic acid in a reaction catalyzed by a cyclooxygenase enzyme. The conversion from Arachidonic acid to Pro ...
, an important precursor of
prostacyclin
Prostacyclin (also called prostaglandin I2 or PGI2) is a prostaglandin member of the eicosanoid family of lipid molecules. It inhibits platelet activation and is also an effective vasodilator.
When used as a drug, it is also known as epoprosten ...
, which is expressed in
inflammation
Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...
.
Function
PTGS2 (COX-2), converts
arachidonic acid (AA) to prostaglandin endoperoxide H2. PTGSs are targets for
NSAID
Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...
s and PTGS2 (COX-2) specific inhibitors called coxibs. PTGS-2 is a sequence homodimer. Each
monomer
In chemistry, a monomer ( ; '' mono-'', "one" + ''-mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
...
of the enzyme has a
peroxidase
Peroxidases or peroxide reductases ( EC numberbr>1.11.1.x are a large group of enzymes which play a role in various biological processes. They are named after the fact that they commonly break up peroxides.
Functionality
Peroxidases typically ca ...
and a PTGS (COX)
active site. The PTGS (COX) enzymes catalyze the conversion of
arachidonic acid to
prostaglandins
The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are deriv ...
in two steps. First, hydrogen is abstracted from carbon 13 of arachidonic acid, and then two molecules of oxygen are added by the PTGS2 (COX-2), giving PGG2. Second,
PGG2
Prostaglandin G2 is an organic peroxide belonging to the family of prostaglandins. The compound has been isolated as a solid, although it is usually used in vivo. It quickly converts into prostaglandin H2, a process catalyzed by the enzyme COX.
...
is reduced to
PGH2
Prostaglandin H2 is a type of prostaglandin and a precursor for many other biologically significant molecules. It is synthesized from arachidonic acid in a reaction catalyzed by a cyclooxygenase enzyme. The conversion from Arachidonic acid to ...
in the peroxidase active site. The synthesized PGH2 is converted to prostaglandins (
PGD2
Prostaglandin D2 (or PGD2) is a prostaglandin that binds to the receptor PTGDR (DP1), as well as CRTH2 (DP2). It is a major prostaglandin produced by mast cells – recruits Th2 cells, eosinophils, and basophils. In mammalian organs, large am ...
,
PGE2
Prostaglandin E2 (PGE2), also known as dinoprostone, is a naturally occurring prostaglandin with oxytocic properties that is used as a medication. Dinoprostone is used in labor induction, bleeding after delivery, termination of pregnancy, and ...
,
PGF2α),
prostacyclin
Prostacyclin (also called prostaglandin I2 or PGI2) is a prostaglandin member of the eicosanoid family of lipid molecules. It inhibits platelet activation and is also an effective vasodilator.
When used as a drug, it is also known as epoprosten ...
(PGI2), or
thromboxane A2
Thromboxane A2 (TXA2) is a type of thromboxane that is produced by activated platelets during hemostasis and has prothrombotic properties: it stimulates activation of new platelets as well as increases platelet aggregation. This is achieved by ac ...
by tissue-specific isomerases.(Figure 2)
While metabolizing arachidonic acid primarily to PGG2, COX-2 also converts this fatty acid to small amounts of a racemic mixture of
15-Hydroxyicosatetraenoic acid
15-Hydroxyeicosatetraenoic acid (also termed 15-HETE, 15(''S'')-HETE, and 15''S''-HETE) is an eicosanoid, i.e. a metabolite of arachidonic acid. Various cell types metabolize arachidonic acid to 15(''S'')-hydroperoxyeicosatetraenoic acid (15(''S'' ...
s (i.e., 15-HETEs) composed of ~22% 15(''R'')-HETE and ~78% 15(''S'')-HETE
stereoisomers
In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms ...
as well as a small amount of 11(''R'')-HETE.
The two 15-HETE stereoisomers have intrinsic biological activities but, perhaps more importantly, can be further metabolized to a major class of agents, the
lipoxins
A lipoxin (LX or Lx), an acronym for lipoxygenase interaction product, is a bioactive autacoid metabolite of arachidonic acid made by various cell types. They are categorized as nonclassic eicosanoids and members of the specialized pro-resolv ...
. Furthermore,
aspirin
Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...
-treated COX-2 metabolizes arachidonic acid almost exclusively to 15(''R'')-HETE which product can be further metabolized to epi-
lipoxins
A lipoxin (LX or Lx), an acronym for lipoxygenase interaction product, is a bioactive autacoid metabolite of arachidonic acid made by various cell types. They are categorized as nonclassic eicosanoids and members of the specialized pro-resolv ...
.
The lipoxins and epi-lipoxins are potent anti-inflammatory agents and may contribute to the overall activities of the two COX's as well as to aspirin.
COX-2 is naturally inhibited by
calcitriol
Calcitriol is the active form of vitamin D, normally made in the kidney. It is also known as 1,25-dihydroxycholecalciferol. It is a hormone which binds to and activates the vitamin D receptor in the nucleus of the cell, which then increases the ...
(the active form of Vitamin D).
Mechanism
![AACOX](https://upload.wikimedia.org/wikipedia/commons/8/88/AACOX.png)
Both the peroxidase and PTGS activities are inactivated during catalysis by mechanism-based, first-order processes, which means that PGHS-2 peroxidase or PTGS activities fall to zero within 1–2 minutes, even in the presence of sufficient substrates.
The conversion of arachidonic acid to PGG2 can be shown as a series of
radical reaction
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron.
With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spon ...
s analogous to polyunsaturated
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...
autoxidation
Autoxidation (sometimes auto-oxidation) refers to oxidations brought about by reactions with oxygen at normal temperatures, without the intervention of flame or electric spark. The term is usually used to describe the gradual degradation of organi ...
.
The 13-pro(S) -hydrogen is abstracted and dioxygen traps the
pentadienyl
In organic chemistry, pentadienyl refers to the organic radical, anion, or cation with the formula , where ''z'' = 0, −1, +1, respectively.
Organometallic chemistry
In organometallic chemistry, the pentadienyl anion is a ligand, the acyclic ana ...
radical at carbon 11. The 11-peroxyl radical cyclizes at carbon 9 and the carbon-centered radical generated at C-8 cyclizes at carbon 12, generating the
endoperoxide
In organic chemistry, organic peroxides are organic compounds containing the peroxide functional group (). If the R′ is hydrogen, the compounds are called hydroperoxides, which are discussed in that article. The O−O bond of peroxides easily b ...
. The
allylic radical generated is trapped by dioxygen at carbon 15 to form the 15-(S) -peroxyl radical; this radical is then reduced to
PGG2
Prostaglandin G2 is an organic peroxide belonging to the family of prostaglandins. The compound has been isolated as a solid, although it is usually used in vivo. It quickly converts into prostaglandin H2, a process catalyzed by the enzyme COX.
...
. This is supported by the following evidence: 1) a significant
kinetic isotope effect
In physical organic chemistry, a kinetic isotope effect (KIE) is the change in the reaction rate of a chemical reaction when one of the atoms in the reactants is replaced by one of its isotopes. Formally, it is the ratio of rate constants for th ...
is observed for the abstraction of the 13-pro (S )-hydrogen; 2) carbon-centered radicals are trapped during
catalysis
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
;
3) small amounts of
oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
products are formed due to the oxygen trapping of an allylic radical intermediate at positions 13 and 15.
Another mechanism in which the 13-pro (S )-hydrogen is
deprotonated
Deprotonation (or dehydronation) is the removal (transfer) of a proton (or hydron, or hydrogen cation), (H+) from a Brønsted–Lowry acid in an acid–base reaction.Henry Jakubowski, Biochemistry Online Chapter 2A3, https://employees.csbsju.ed ...
and the
carbanion is
oxidized
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
to a
radical is theoretically possible. However, oxygenation of 10,10-difluoroarachidonic acid to 11-(S )-hydroxyeicosa-5,8,12,14-tetraenoic acid is not consistent with the generation of a carbanion intermediate because it would eliminate fluoride to form a conjugated diene.
The absence of endoperoxide-containing products derived from 10,10-difluoroarachidonic acid has been thought to indicate the importance of a C-10 carbocation in
PGG2
Prostaglandin G2 is an organic peroxide belonging to the family of prostaglandins. The compound has been isolated as a solid, although it is usually used in vivo. It quickly converts into prostaglandin H2, a process catalyzed by the enzyme COX.
...
synthesis.
However, the cationic mechanism requires that endoperoxide formation comes before the removal of the 13-pro (S )-hydrogen. This is not consistent with the results of the isotope experiments of
arachidonic acid oxygenation.
Structure
PTGS2 (COX-2) exists as a homodimer, each monomer with a molecular mass of about 70 kDa. The tertiary and quaternary structures of PTGS1 (COX-1) and PTGS2 (COX-2) enzymes are almost identical. Each subunit has three different structural domains: a short
N-terminal epidermal growth factor (
EGF) domain; an
α-helical membrane-binding moiety; and a
C-terminal
The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...
catalytic domain. PTGS (COX, which can be confused with "
cytochrome oxidase
The enzyme cytochrome c oxidase or Complex IV, (was , now reclassified as a translocasEC 7.1.1.9 is a large transmembrane protein complex found in bacteria, archaea, and mitochondria of eukaryotes.
It is the last enzyme in the respiratory elect ...
") enzymes are
monotopic membrane proteins; the membrane-binding domain consists of a series of
amphipathic
An amphiphile (from the Greek αμφις amphis, both, and φιλíα philia, love, friendship), or amphipath, is a chemical compound possessing both hydrophilic (''water-loving'', polar) and lipophilic (''fat-loving'') properties. Such a compoun ...
α helices with several
hydrophobic
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water.
Hydrophobic molecules tend to be nonpolar and, t ...
amino acids exposed to a membrane monolayer. PTGS1 (COX-1) and PTGS2 (COX-2) are bifunctional enzymes that carry out two consecutive chemical reactions in spatially distinct but mechanistically
coupled
''Coupled'' is an American dating game show that aired on Fox from May 17 to August 2, 2016. It was hosted by television personality, Terrence J and created by Mark Burnett, of '' Survivor'', ''The Apprentice'', '' Are You Smarter Than a 5th G ...
active sites. Both the
cyclooxygenase
Cyclooxygenase (COX), officially known as prostaglandin-endoperoxide synthase (PTGS), is an enzyme (specifically, a family of isozymes, ) that is responsible for formation of prostanoids, including thromboxane and prostaglandins such as pr ...
and the
peroxidase
Peroxidases or peroxide reductases ( EC numberbr>1.11.1.x are a large group of enzymes which play a role in various biological processes. They are named after the fact that they commonly break up peroxides.
Functionality
Peroxidases typically ca ...
active sites are located in the catalytic domain, which accounts for approximately 80% of the protein. The catalytic domain is
homologous to mammalian peroxidases such as
myeloperoxidase
Myeloperoxidase (MPO) is a peroxidase enzyme that in humans is encoded by the ''MPO'' gene on chromosome 17. MPO is most abundantly expressed in neutrophil granulocytes (a subtype of white blood cells), and produces hypohalous acids to carry ...
.
It has been found that human PTGS2 (COX-2) functions as a conformational heterodimer having a catalytic monomer (E-cat) and an allosteric monomer (E-allo).
Heme
Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver.
In biochemical terms, heme is a coordination complex "consis ...
binds only to the
peroxidase
Peroxidases or peroxide reductases ( EC numberbr>1.11.1.x are a large group of enzymes which play a role in various biological processes. They are named after the fact that they commonly break up peroxides.
Functionality
Peroxidases typically ca ...
site of E-cat while substrates, as well as certain
inhibitors (e.g.
celecoxib
Celecoxib, sold under the brand name Celebrex among others, is a COX-2 inhibitor and nonsteroidal anti-inflammatory drug (NSAID). It is used to treat the pain and inflammation in osteoarthritis, acute pain in adults, rheumatoid arthritis, ankyl ...
), bind the COX site of E-cat. E-cat is regulated by E-allo in a way dependent on what ligand is bound to E-allo.
Substrate and non-substrate
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...
(FAs) and some PTGS (COX) inhibitors (e.g.
naproxen
Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain, menstrual cramps, inflammatory diseases such as rheumatoid arthritis, gout and fever. It is taken orally. It is available in immediate and delayed release formulat ...
) preferentially bind to the PTGS (COX) site of E-allo.
Arachidonic acid can bind to E-cat and E-allo, but the affinity of AA for E-allo is 25 times that for Ecat. Palmitic acid, an efficacious stimulator of
huPGHS-2, binds only E-allo in palmitic acid/murine PGHS-2 co-crystals. Non-substrate FAs can potentiate or
attenuate
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at vari ...
PTGS (COX) inhibitors depending on the
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...
and whether the inhibitor binds E-cat or E-allo. Studies suggest that the concentration and composition of the free fatty acid pool in the environment in which PGHS-2 functions in cells, also referred to as the FA tone, is a key factor regulating the activity of PGHS-2 and its response to PTGS (COX) inhibitors.
Clinical significance
![Flurbiprofen in COX-2](https://upload.wikimedia.org/wikipedia/commons/5/5f/Flurbiprofen_in_COX-2.png)
PTGS2 (COX-2) is unexpressed under normal conditions in most cells, but elevated levels are found during
inflammation
Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...
. PTGS1 (COX-1) is constitutively expressed in many tissues and is the predominant form in gastric mucosa and in the kidneys. Inhibition of PTGS1 (COX-1) reduces the
basal production of cytoprotective
PGE2
Prostaglandin E2 (PGE2), also known as dinoprostone, is a naturally occurring prostaglandin with oxytocic properties that is used as a medication. Dinoprostone is used in labor induction, bleeding after delivery, termination of pregnancy, and ...
and
PGI2
Prostacyclin (also called prostaglandin I2 or PGI2) is a prostaglandin member of the eicosanoid family of lipid molecules. It inhibits platelet activation and is also an effective vasodilator.
When used as a drug, it is also known as epoprosten ...
in the
stomach
The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...
, which may contribute to
gastric ulceration. Since PTGS2 (COX-2) is generally expressed only in cells where
prostaglandins are upregulated (e.g., during inflammation), drug-candidates that selectively inhibit PTGS2 (COX-2) were suspected to show fewer
side-effects
In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
but proved to substantially increase risk for cardiovascular events such as heart attack and stroke. Two different mechanisms may explain contradictory effects. Low-dose aspirin protects against heart attacks and strokes by blocking PTGS1 (COX-1) from forming a prostaglandin called thromboxane A2. It sticks platelets together and promotes clotting; inhibiting this helps prevent heart disease. On the other hand, PTGS2 (COX-2) is a more important source of prostaglandins, particularly prostacyclin which is found in blood vessel lining. Prostacyclin relaxes or unsticks platelets, so
selective COX-2 inhibitors (coxibs) increase risk of cardiovascular events due to clotting.
Non-steroidal anti-inflammatory drug
Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...
s (NSAIDs) inhibit
prostaglandin production by PTGS1 (COX-1) and PTGS2 (COX-2).
NSAIDs selective for inhibition of PTGS2 (COX-2) are less likely than traditional drugs to cause
gastrointestinal
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
adverse effects, but could cause
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 ...
events, such as
heart failure,
myocardial infarction
A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may ...
, and
stroke. Studies with human
pharmacology and
genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
, genetically manipulated
rodents, and other animal models and randomized trials indicate that this is due to suppression of PTGS2 (COX-2)-dependent cardioprotective
prostaglandins
The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are deriv ...
,
prostacyclin
Prostacyclin (also called prostaglandin I2 or PGI2) is a prostaglandin member of the eicosanoid family of lipid molecules. It inhibits platelet activation and is also an effective vasodilator.
When used as a drug, it is also known as epoprosten ...
in particular.
The expression of PTGS2 (COX-2) is upregulated in many cancers. The overexpression of PTGS2 (COX-2) along with increased angiogenesis and SLC2A1 (GLUT-1) expression is significantly associated with gallbladder carcinomas.
Furthermore, the product of PTGS2 (COX-2),
PGH2 is converted by
prostaglandin E2 synthase
Prostaglandin E synthase (, or PGE synthase) is an enzyme involved in eicosanoid and glutathione metabolism, a member of MAPEG family. It generates prostaglandin E (PGE) from prostaglandin H2.
The synthase generating PGE2 is a membrane-associated ...
into
PGE2, which in turn can stimulate cancer progression. Consequently, inhibiting PTGS2 (COX-2) may have benefit in the prevention and treatment of these types of cancer.
COX-2 expression was found in human idiopathic epiretinal membranes. Cyclooxygenases blocking by
lornoxicam
Lornoxicam, also known as chlortenoxicam, is a nonsteroidal anti-inflammatory drug (NSAID) of the oxicam class with analgesic (pain relieving), anti-inflammatory and antipyretic (fever reducing) properties. It is available in oral administration, ...
in acute stage of inflammation reduced the frequency of membrane formation by 43% in the
dispase model of
PVR and by 31% in the
concanavalin one.
Lornoxicam
Lornoxicam, also known as chlortenoxicam, is a nonsteroidal anti-inflammatory drug (NSAID) of the oxicam class with analgesic (pain relieving), anti-inflammatory and antipyretic (fever reducing) properties. It is available in oral administration, ...
not only normalized the expression of cyclooxygenases in both models of PVR, but also neutralized the changes of the
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
and the
choroid thickness caused by the injection of pro-inflammatory agents. These facts underline the importance of cyclooxygenases and prostaglandins in the development of PVR.
PTGS2 gene upregulation has also been linked with multiple stages of human reproduction. Presence of gene is found in the
chorionic plate, in the
amnion epithelium,
syncytiotrophoblasts
Syncytiotrophoblast (from the Greek 'syn'- "together"; 'cytio'- "of cells"; 'tropho'- "nutrition"; 'blast'- "bud") is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nut ...
, villous fibroblasts, chorionic
trophoblast
The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the p ...
s,
amniotic trophoblasts, as well as the
basal plate of the placenta, in the
decidual cells
Before the fertilized ovum reaches the uterus, the mucous membrane of the body of the uterus undergoes important changes and is then known as the decidua. The thickness and vascularity of the mucous membrane are greatly increased; its glands are el ...
and
extravillous cytotrophoblasts. During the process of
chorioamnionitis
Chorioamnionitis, also known as intra-amniotic infection (IAI), is inflammation of the fetal membranes ( amnion and chorion), usually due to bacterial infection. In 2015, a National Institute of Child Health and Human Development Workshop expert ...
/deciduitis, the upregulation of PTGS2 in the
amnion and choriodecidua is one of three limited effects of inflammation in the
uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
. Increased expression of the PTGS2 gene in the
fetal membranes
The fetal membranes are the four extraembryonic membranes, associated with the developing embryo, and fetus in humans and other mammals.. They are the amnion, chorion, allantois, and yolk sac. The amnion and the chorion are the chorioamniotic me ...
is connected to the presence of inflammation, causing uterine prostaglandin gene expression and immunolocalization of
prostaglandin pathway proteins in chorionic trophoblast cells and adjacent decidua, or choriodecidua. PTGS2 is linked with the inflammatory system and has been observed in inflammatory
leukocytes
White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...
. It has been noted that there is a positive correlation with PTGS2 expression in the amnion during spontaneous labour and was discovered to have increased expression with gestational age following the presence of labour with no change observed in amnion and choriodecidua during either preterm or term labour. Additionally,
oxytocin stimulates the expression of PTGS2 in
myometrial cells.
[Phillips, Robert J et al. “Prostaglandin pathway gene expression in human placenta, amnion and choriodecidua is differentially affected by preterm and term labour and by uterine inflammation.” BMC pregnancy and childbirth vol. 14 241. 22 Jul. 2014, doi:10.1186/1471-2393-14-241]
The mutant allele PTGS2 5939C carriers among the Han Chinese population have been shown to have a higher risk of
gastric cancer
Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Lymph ...
. In addition, a connection was found between ''
Helicobacter pylori
''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is thoug ...
'' infection and the presence of the 5939C allele.
Interactions
PTGS2 has been shown to
interact
Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...
with
caveolin 1
Caveolin-1 is a protein that in humans is encoded by the ''CAV1'' gene.
Function
The scaffolding protein encoded by this gene is the main component of the caveolae plasma membranes found in most cell types. The protein links integrin subunits ...
.
History
PTGS2 (COX-2) was discovered in 1991 by the
Daniel Simmons laboratory
at Brigham Young University.
See also
*
Arachidonic acid
*
Cyclooxygenase
Cyclooxygenase (COX), officially known as prostaglandin-endoperoxide synthase (PTGS), is an enzyme (specifically, a family of isozymes, ) that is responsible for formation of prostanoids, including thromboxane and prostaglandins such as pr ...
*
Cyclooxygenase 1
Cyclooxygenase (COX), officially known as prostaglandin-endoperoxide synthase (PTGS), is an enzyme (specifically, a family of isozymes, ) that is responsible for formation of prostanoids, including thromboxane and prostaglandins such as prosta ...
*
NSAID
Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...
*
Discovery and development of COX-2 selective inhibitors
*
COX-2 selective inhibitor
COX-2 inhibitors are a type of nonsteroidal anti-inflammatory drug (NSAID) that directly targets cyclooxygenase-2, COX-2, an enzyme responsible for inflammation and pain. Targeting selectivity for COX-2 reduces the risk of peptic ulceration and ...
References
Further reading
*
*
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*
External links
NextbioNSAIDs and Cardiovascular Risk Explained, According to Studies from the Perelman School of Medicine*
{{Prostanoidergics
Prostaglandins