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Eicosanoid
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[[File:480px-EFA_to_Eicosanoids.svg.png|right|insert caption]] '''Eicosanoids''' are [[Signaling molecule|signaling molecules]] made from the long chain [[polyunsaturated fatty acid]]s (PUFAs) [[eicosapentaenoic acid]] (EPA), [[dihomo-gamma-linolenic acid]] (DGLA) and especially [[arachidonic acid]] (AA). Like [[cytokine]]s and [[inflammasome]]s, they play an important role in the initiation and resolution of immune responses to [[infection]] and [[injury]]. Their complex role in [[inflammation]] and [[homeostasis]] is not well understood. ==Types of eicosanoids== Eicosanoids include [[leukotriene]]s, [[eoxin]]s and three types of [[prostanoid]]s βΒ [[prostaglandins]], [[prostacyclin]]s and [[thromboxanes]]. Eicosanoids derived from [[omega 6 fatty acid]]s tend to be pro-inflammatory while those derived from [[omega 3 fatty acid]]s tend to be [[anti-inflammatory]] or perhaps more accurately, less active.{{citation needed}} Eicosanoids are also related to [[docosanoid]]s, signaling molecules derived primarily from [[docosahexaenoic acid]] (DHA) and [[resolvin]]s and [[lipoxin]]s, signaling molecules that induce the resolution of inflammation following acute [[infection]] or injury that are made from EPA and EHA. ==Biosynthesis== Eicosanoids are made from the oxidation of arachidonic acid and other PUFAs by [[cyclooxygenase]] (COX), [[lipoxygenase]] (LOX) and [[cytochrome P450]] (CYP) [[Enzyme|enzymes]] from [[Cell membrane|cell membranes]] or via free radicals. <ref>http://www.ncbi.nlm.nih.gov/pubmed/26139350</ref> The majority of eicosanoids require [[arachidonic acid]], which is cleaved from cell membranes by [[phospholipase A2]] (PLA2) enzymes. Most cells produce insignificant amount of eicosanoids under normal conditions and produce a small number of specific eicosanoids when exposed to stimuli that activate [[PLA2]]. ==Function== Eicosanoids are involved in vasodilation and vasoconstriction, promotion of sleep, pain and fever. They pay a role in up- or down-regulating inflammatory [[Cytokine|cytokines]]. What eicosanoids cells produce and their effects depend on the type of cell, the tissue in which that cell is found, and the cell's activation state. For example, those produced via the [[COX]] enzyme pathway generate the symptoms commonly associated with inflammation: heat, swelling, redness, and pain. Those produced via the [[LOX]] pathway tend to be associated with the leukotrienes involved in [[allergy]] and asthma. The same prostaglandin that causes pain signaling in the brain can lead to a decrease in inflammation in other parts of the body.<ref>http://www.ncbi.nlm.nih.gov/pubmed/26139350</ref> ==Medical applications== ===NSAIDs=== [[NSAIDs|Non-steroidal anti-inflammatory drugs]] like [[aspirin]] relieve pain, swelling and fever by inhibiting the receptors for leukotrienes, for example, or by inhibiting COX enzymes.<ref>http://www.ncbi.nlm.nih.gov/pubmed/26139350</ref> ===Inhibition of Omega 6 products by Omega 3 supplementation=== Omega 3 and Omega 6 derived eicosanoids compete with each other in three ways: displacement (dietary Omega 3 decreases tissue concentrations of AA), competitive inhibition ([[Dihomo-gamma-linolenic acid|DGLA]] and [[Eicosapentaenoic acid|EPA]] compete with [[Arachidonic acid|AA]] for enzymes), and counteraction (some DGLA and EPA-derived eicosanoids counteract their AA derived counterparts). Omega 3 supplementation is commonly prescribed for the treatment of inflammatory and cardiovascular disease because of the capacity of EPA and [[Docosahexaenoic acid|DHA]] to inhibit arachidonic acid [[metabolism]] by the [[COX1]] pathway (but less so by [[COX2]]).<ref>http://www.ncbi.nlm.nih.gov/pubmed/26139350</ref> ==See also== *[[Fatty acid hypothesis]] == References == {{Reflist}} [[Category:Immunology]] [[Category:Eicosanoids]] [[Category:Fatty acids]]
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