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.
Arachidonic acid is a polyunsaturated omega−6 fatty acid 20:4(ω−6), or 20:4(5,8,11,14). If its precursors or diet contains linoleic acid it is formed by biosynthesis and can be deposited in animal fats. It is a precursor in the formation of leukotrienes, prostaglandins, and thromboxanes.
Cyclooxygenase (COX), officially known as prostaglandin-endoperoxide synthase (PTGS), is an enzyme that is responsible for biosynthesis of prostanoids, including thromboxane and prostaglandins such as prostacyclin, from arachidonic acid. A member of the animal-type heme peroxidase family, it is also known as prostaglandin G/H synthase. The specific reaction catalyzed is the conversion from arachidonic acid to prostaglandin H2 via a short-living prostaglandin G2 intermediate.
Eicosanoids are signaling molecules made by the enzymatic or non-enzymatic oxidation of arachidonic acid or other polyunsaturated fatty acids (PUFAs) that are, similar to arachidonic acid, around 20 carbon units in length. Eicosanoids are a sub-category of oxylipins, i.e. oxidized fatty acids of diverse carbon units in length, and are distinguished from other oxylipins by their overwhelming importance as cell signaling molecules. Eicosanoids function in diverse physiological systems and pathological processes such as: mounting or inhibiting inflammation, allergy, fever and other immune responses; regulating the abortion of pregnancy and normal childbirth; contributing to the perception of pain; regulating cell growth; controlling blood pressure; and modulating the regional flow of blood to tissues. In performing these roles, eicosanoids most often act as autocrine signaling agents to impact their cells of origin or as paracrine signaling agents to impact cells in the proximity of their cells of origin. Some eicosanoids, such as prostaglandins, may also have endocrine roles as hormones to influence the function of distant cells.
Malondialdehyde belong to the class of β-dicarbonyls. A colorless liquid, malondialdehyde is a highly reactive compound that occurs as the enol. It is a physiological metabolite, and a marker for oxidative stress.
In molecular biology, prostanoids are active lipid mediators that regulate inflammatory response. Prostanoids are a subclass of eicosanoids consisting of the prostaglandins, the thromboxanes, and the prostacyclins. Prostanoids are seen to target NSAIDS which allow for therapeutic potential. Prostanoids are present within areas of the body such as the gastrointestinal tract, urinary tract, respiratory and cardiovascular systems, reproductive tract and vascular system. Prostanoids can even be seen with aid to the water and ion transportation within cells.
The isoprostanes are prostaglandin-like compounds formed in vivo from the free radical-catalyzed peroxidation of essential fatty acids without the direct action of cyclooxygenase (COX) enzymes. The compounds were discovered in 1990 by L. Jackson Roberts and Jason D. Morrow in the Division of Clinical Pharmacology at Vanderbilt University. These nonclassical eicosanoids possess potent biological activity as inflammatory mediators that augment the perception of pain. These compounds are accurate markers of lipid peroxidation in both animal and human models of oxidative stress.
Prostaglandin-I synthase also known as prostaglandin I2 (prostacyclin) synthase (PTGIS) or CYP8A1 is an enzyme involved in prostanoid biosynthesis that in humans is encoded by the PTGIS gene. This enzyme belongs to the family of cytochrome P450 isomerases.
In molecular biology, Beta-ketoacyl-ACP synthase EC 2.3.1.41, is an enzyme involved in fatty acid synthesis. It typically uses malonyl-CoA as a carbon source to elongate ACP-bound acyl species, resulting in the formation of ACP-bound β-ketoacyl species such as acetoacetyl-ACP.
Prostaglandin H2 (PGH2), or prostaglandin H2 (PGH2), 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 prostaglandin H2 is a two-step process. First, COX-1 catalyzes the addition of two free oxygens to form the 1,2-dioxane bridge and a peroxide functional group to form prostaglandin G2 (PGG2). Second, COX-2 reduces the peroxide functional group to a secondary alcohol, forming prostaglandin H2. Other peroxidases like hydroquinone have been observed to reduce PGG2 to PGH2. PGH2 is unstable at room temperature, with a half life of 90–100 seconds, so it is often converted into a different prostaglandin.
Cyclooxygenase-2 (COX-2), also known as prostaglandin-endoperoxide synthase 2 (HUGO PTGS2), is an enzyme that in humans is encoded by the PTGS2 gene. In humans it is one of three cyclooxygenases. It is involved in the conversion of arachidonic acid to prostaglandin H2, an important precursor of prostacyclin, which is expressed in inflammation.
Mead acid is an omega-9 fatty acid, first characterized by James F. Mead. As with some other omega-9 polyunsaturated fatty acids, animals can make Mead acid de novo. Its elevated presence in the blood is an indication of essential fatty acid deficiency. Mead acid is found in large quantities in cartilage.
Nonclassic eicosanoids are biologically active signaling molecules made by oxygenation of twenty-carbon fatty acids other than the classic eicosanoids.
Cyclooxygenase 1 (COX-1), also known as prostaglandin-endoperoxide synthase 1, is an enzyme that in humans is encoded by the PTGS1 gene. In humans it is one of two cyclooxygenases.
Cytochrome P450 4F8 is a protein that in humans is encoded by the CYP4F8 gene.
A depside is a type of polyphenolic compound composed of two or more monocyclic aromatic units linked by an ester group. Depsides are most often found in lichens, but have also been isolated from higher plants, including species of the Ericaceae, Lamiaceae, Papaveraceae and Myrtaceae.
Oxylipins constitute a family of oxygenated natural products which are formed from fatty acids by pathways involving at least one step of dioxygen-dependent oxidation. These small polar lipid compounds are metabolites of polyunsaturated fatty acids (PUFAs) including omega-3 fatty acids and omega-6 fatty acids. Oxylipins are formed by enyzmatic or non-enzymatic oxidation of PUFAs.
15-Hydroxyeicosatetraenoic acid (also termed 15-HETE, 15(S)-HETE, and 15S-HETE) is an eicosanoid, i.e. a metabolite of arachidonic acid. Various cell types metabolize arachidonic acid to 15(S)-hydroperoxyeicosatetraenoic acid (15(S)-HpETE). This initial hydroperoxide product is extremely short-lived in cells: if not otherwise metabolized, it is rapidly reduced to 15(S)-HETE. Both of these metabolites, depending on the cell type which forms them, can be further metabolized to 15-oxo-eicosatetraenoic acid (15-oxo-ETE), 5(S),15(S)-dihydroxy-eicosatetraenoic acid (5(S),15(S)-diHETE), 5-oxo-15(S)-hydroxyeicosatetraenoic acid (5-oxo-15(S)-HETE), a subset of specialized pro-resolving mediators viz., the lipoxins, a class of pro-inflammatory mediators, the eoxins, and other products that have less well-defined activities and functions. Thus, 15(S)-HETE and 15(S)-HpETE, in addition to having intrinsic biological activities, are key precursors to numerous biologically active derivatives.
The prostaglandin E2 (PGE2) receptors are G protein-coupled receptors that bind and are activated by prostaglandin E2. They are members of the prostaglandin receptors class of receptors and include the following Protein isoforms:
The neuroprostanes are prostaglandin-like compounds formed in vivo from the free radical-catalyzed peroxidation of essential fatty acids without the direct action of cyclooxygenase (COX) enzymes. The result is the formation of isoprostane-like compounds F4-, D4-, E4-, A4-, and J4-neuroprostanes which have been shown to be produced in vivo. These oxygenated essential fatty acids possess potent biological activity as anti-inflammatory mediators inhibiting the response of human macrophages that augment the perception of pain.
