Prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids that have diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derived enzymatically from the fatty acid arachidonic acid. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring. They are a subclass of eicosanoids and of the prostanoid class of fatty acid derivatives.
Pulmonary hypertension is a condition of increased blood pressure in the arteries of the lungs. Symptoms include shortness of breath, fainting, tiredness, chest pain, swelling of the legs, and a fast heartbeat. The condition may make it difficult to exercise. Onset is typically gradual. According to the definition at the 6th World Symposium of Pulmonary Hypertension in 2018, a patient is deemed to have pulmonary hypertension if the pulmonary mean arterial pressure is greater than 20mmHg at rest, revised down from a purely arbitrary 25mmHg, and pulmonary vascular resistance (PVR) greater than 3 Wood units.
The ductus arteriosus, also called the ductus Botalli, named after the Italian physiologist Leonardo Botallo, is a blood vessel in the developing fetus connecting the trunk of the pulmonary artery to the proximal descending aorta. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled non-functioning lungs. Upon closure at birth, it becomes the ligamentum arteriosum.
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.
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 in newborn babies to keep the ductus arteriosus open. In babies it is used in those with congenital heart defects until surgery can be carried out. It is also used to manage gestational trophoblastic disease. It may be used within the vagina or by injection into a vein.
Portopulmonary hypertension (PPH) is defined by the coexistence of portal and pulmonary hypertension. PPH is a serious complication of liver disease, present in 0.25 to 4% of all patients with cirrhosis. Once an absolute contraindication to liver transplantation, it is no longer, thanks to rapid advances in the treatment of this condition. Today, PPH is comorbid in 4-6% of those referred for a liver transplant.
Enprostil is a synthetic prostaglandin designed to resemble dinoprostone. Enprostil was found to be a highly potent inhibitor of gastric HCl secretion. It is an analog of prostaglandin E2 but unlike this prostaglandin, which binds to and activates all four cellular receptors viz., EP1, EP2, EP3, and EP4 receptors, enprostil is a more selective receptor agonist in that it binds to and activates primarily the EP3 receptor. Consequently, enprostil is expected to have a narrower range of actions that may avoid some of the unwanted side-effects and toxicities of prostaglandin E2. A prospective multicenter randomized controlled trial conducted in Japan found combining enprostil with cimetidine was more effective than cimetidine alone in treating gastric ulcer.
Treprostinil, sold under the brand names Remodulin for infusion, Orenitram for oral, and Tyvaso for inhalation, is a vasodilator that is used for the treatment of pulmonary arterial hypertension. Treprostinil is a synthetic analog of prostacyclin (PGI2).
Beraprost is a pharmaceutical drug used in several Asian countries, including Japan and South Korea, as a vasodilator and antiplatelet agent. It is classified as a prostacyclin analog.
A prostaglandin antagonist is a hormone antagonist acting upon one or more prostaglandins, a subclass of eicosanoid compounds which function as signaling molecules in numerous types of animal tissues.
Most of the eicosanoid receptors are integral membrane protein G protein-coupled receptors (GPCRs) that bind and respond to eicosanoid signaling molecules. Eicosanoids are rapidly metabolized to inactive products and therefore are short-lived. Accordingly, the eicosanoid-receptor interaction is typically limited to a local interaction: cells, upon stimulation, metabolize arachidonic acid to an eicosanoid which then binds cognate receptors on either its parent cell or on nearby cells to trigger functional responses within a restricted tissue area, e.g. an inflammatory response to an invading pathogen. In some cases, however, the synthesized eicosanoid travels through the blood to trigger systemic or coordinated tissue responses, e.g. prostaglandin (PG) E2 released locally travels to the hypothalamus to trigger a febrile reaction. An example of a non-GPCR receptor that binds many eicosanoids is the PPAR-γ nuclear receptor.
Prostaglandin receptors or prostanoid receptors represent a sub-class of cell surface membrane receptors that are regarded as the primary receptors for one or more of the classical, naturally occurring prostanoids viz., prostaglandin D2,, PGE2, PGF2alpha, prostacyclin (PGI2), thromboxane A2 (TXA2), and PGH2. They are named based on the prostanoid to which they preferentially bind and respond, e.g. the receptor responsive to PGI2 at lower concentrations than any other prostanoid is named the Prostacyclin receptor (IP). One exception to this rule is the receptor for thromboxane A2 (TP) which binds and responds to PGH2 and TXA2 equally well.
The prostaglandin D2 receptor 1 (DP1), a G protein-coupled receptor encoded by the PTGDR1 gene (also termed PTGDR), is primarily a receptor for prostaglandin D2 (PGD2). The receptor is a member of the prostaglandin receptors belonging to the subfamily A14 of rhodopsin-like receptors. Activation of DP1 by PGD2 or other cognate receptor ligands is associated with a variety of physiological and pathological responses in animal models.
Prostaglandin E2 receptor 4 (EP4) is a prostaglandin receptor for prostaglandin E2 (PGE2) encoded by the PTGER4 gene in humans; it is one of four identified EP receptors, the others being EP1, EP2, and EP3, all of which bind with and mediate cellular responses to PGE2 and also, but generally with lesser affinity and responsiveness, certain other prostanoids (see Prostaglandin receptors). EP4 has been implicated in various physiological and pathological responses in animal models and humans.
Prostaglandin E2 receptor 2, also known as EP2, is a prostaglandin receptor for prostaglandin E2 (PGE2) encoded by the human gene PTGER2: it is one of four identified EP receptors, the others being EP1, EP3, and EP4, which bind with and mediate cellular responses to PGE2 and also, but with lesser affinity and responsiveness, certain other prostanoids (see Prostaglandin receptors). EP has been implicated in various physiological and pathological responses.
Prostaglandin EP3 receptor (53kDa), also known as EP3, is a prostaglandin receptor for prostaglandin E2 (PGE2) encoded by the human gene PTGER3; it is one of four identified EP receptors, the others being EP1, EP2, and EP4, all of which bind with and mediate cellular responses to PGE2 and also, but generally with lesser affinity and responsiveness, certain other prostanoids (see Prostaglandin receptors). EP has been implicated in various physiological and pathological responses.
The Prostacyclin receptor, also termed the prostaglandin I2 receptor or just IP, is a receptor belonging to the prostaglandin (PG) group of receptors. IP binds to and mediates the biological actions of prostacyclin (also termed Prostaglandin I2, PGI2, or when used as a drug, epoprostenol). IP is encoded in humans by the PTGIR gene. While possessing many functions as defined in animal model studies, the major clinical relevancy of IP is as a powerful vasodilator: stimulators of IP are used to treat severe and even life-threatening diseases involving pathological vasoconstriction.
Sulprostone is an analogue of prostaglandin E2 (PGE2) that has oxytocic activity in assays of rat kidney cells and tissues. There are four known receptors which mediate various but often different cellular and tissue responses to PGE2: prostaglandin EP1 receptor, prostaglandin EP2 receptor, prostaglandin EP3 receptor, and prostaglandin EP4 receptor. Sulprosotone binds to and activates the prostaglandin EP3 receptor with far greater efficacy than the other PGE2 receptors and also has the advantage of being relatively resistant, compared with PGE2, to becoming metabolically degraded. It is listed as a comparatively weak receptor agonist of the prostaglandin EP1 receptor. In all events, this as well as other potent synthetic EP3 receptor antagonists have the realized or potential ability to promote the beneficial effects of prostaglandin EP3 receptor activation.
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 ambrisentan. Macitentan is a dual ERA, meaning that it acts as an antagonist of two endothelin (ET) receptor subtypes, ETA and ETB. However, macitentan has a 50-fold increased selectivity for the ETA subtype compared to the ETB subtype. The drug received approval from the U.S. Food and Drug Administration (FDA) on October 13, 2013.
Selexipag, sold under the brand name Uptravi, is a medication developed by Actelion for the treatment of pulmonary arterial hypertension (PAH). Selexipag and its active metabolite, ACT-333679, are agonists of the prostacyclin receptor, which leads to vasodilation in the pulmonary circulation. It is taken by mouth or administered intravenously.
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