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Eicosanoids are normally known for their roles in inflammation. This is due to the little information available on such molecules because of their state of existence. These molecules contain a lifespan of normally only a few seconds. However, beyond inflammation, further research has shown these molecules to function in cell proliferation, tissue repair, blood clotting, blood vessel permeability, vessel constriction/relaxation, and immune cell behavior.
Eicosanoids and their functions
Eicosanoids are normally associated with the word "inflammation." These molecules are not normally well known for their roles in anything else. Therefore, I hypothesize that 'Eicosanoids mainly function in the inflammation response." In order to understand the roles of eicosanoids, it is necessary to understand what they are exactly.
Eicosanoids are signaling molecules formed by the oxidation of twenty-carbon essential fatty acids (DeCaterina & Basta, 2001). These molecules show a complex control over many bodily systems. Eicosanoidal control exists mainly with the inflammation response and immune response, as well as functioning as messengers of the central nervous system (Funk, 2001). The human body greatly depends on these molecules for normal function.
Eicosanoids originate from omega-3 and omega-6 essential fatty acids (DeCaterina & Basta, 2001). Omega-6 eicosanoids are normally pro-inflammatory; whereas, omega-3's are much less so (DeCaterina & Basta, 2001). The amount and balance of these fats are determined by a person's diet (DeCaterina & Basta, 2001). This directly affects the body's eicosanoid controlled functions (Soberman & Christmas, 2003). These functions have effects on cardiovascular disease, triglycerides, blood pressure, and arthritis (Soberman & Christmas, 2003). Drugs such as aspirin, an anti-inflammatory drug, and other NSAIDs act by downregulating eicosanoid synthesis (Smith, 1989).
There are four types of eicosanoids, each of which has two or three separate series of which is derived from an Omega-3 or Omega-6 essential fatty acid (DeCaterina & Basta, 2001). These four main types are known as the prostaglandins, prostacyclins, the thromboxanes, and the leukotreines (DeCaterina & Basta, 2001). Each series of the main types have different functions in the body, which explains the vast health benefits of the omega-3 and omega-6 fats.
Eicosanoid production occurs from two families of enzymes known as cyclooxygenase and lipoxygease (DeCaterina & Basta, 2001). For example, cyclooxygenase is involved in the creation of prostanoids. Another example is that of an enzyme called 5-lipoxygenase, which creates leukotrienes. The resulting eicosanoid production is not stored in cells,but synthesized as needed (DeCaterina & Basta, 2001).
Ecosanoids are formed primarily by arachidonic acid that has been released from the cell membrane phospholipids. This release occurs from the enzyme phopholipase-A2. This enzyme is normally participates in the maintenance of cellular membranes. However, this enzyme can be found in larger amounts by the triggers involved in initiating or continuing inflammation. The release of arichidonic acid by the enzyme can be halted by the ingestion of corticosteroid drugs (Dharmananda, 2003).
Most drug treatments that focus on painful inflammation block the production of eicosanoids after the arachidonic acid has already formed. The most commonly used drugs are used to inhibit the cyclooxygenase enzymes and recent studies have shown this to be the main role in over the counter anti-inflammatory drugs; i.e., aspirin, acetaminophen, and ibuprofen (Smith, 1989).
All information on eicosanoids and their relationship in inflammation and chronic diseases is extremely complex and constantly evolving. Eicosanoids are very hard to study do to their varying life spans of a split second to a few minutes. They have been referred to in studies as 'local' hormones (Smith, 1989). This concept originated with the studies of Ferreira and Vane (Ferreira & Vane, 1967). These two demonstrated that introduced Prostaglandin-E and Prostaglandin-Fx derivatives were unable to make a single pass through the circulatory system. Their studies supported the theory that eicosanoid synthesis is not restricted to a central endocrine organ, but that synthesis occurs in most organs (Ferreira & Vane, 1967). This supports their wide array of functions.
Research has shown each group of eicosanoids has both good and bad effects. Prostaglandins, for example, mainly effect the influencing of platelet aggregation and the constriction or relaxation of blood vessels. Some prostaglandins show favorable effects, such as insuring the integrity of the gastric lining, regulation of kidney function, and some also play vital roles in stages of childbirth. However, some show negative effects, such as increasing the feeling of pain, causing muscular cramping, and restricting blood flow. These eicosanoids, mainly prostaglandin-E2 , are involved in inflammation (Dharmananda, 2003).
The thromboxanes are created by platelets. These eicosanoids enhance platelet aggregation, as well as causing the constriction of blood vessels and bronchioles. This group is mainly known for their negative impacts on the body; especially cardiovascular health and their contribution to asthma. On the positive side, they start an immediate response to injuries in order to limit blood loss (Dharmananda, 2003).
The leukotreines are created by immune system cells. They stimulate the production of the immune system signaling molecules; i.e., interleukins, interferons, and other substances involved in anaphylactic reactions. These eicosanoids have mostly known for their part in allergies and autoimmune diseases (Dharmananda, 2003).
Eicosanoids are mainly studied for their roles in inflammation. However, their function in the human body goes far beyond that. With these molecules being extremely hard to study, due to their very short lifespan of a split second to a couple minutes, very little is known of these molecules (McMurray, 1982). What research has been done on these molecules has shown them to have a larger number of roles in the human body than normally focuses on. Besides inflammation, eicosanoids function in cell proliferation, tissue repair, blood clotting, blood vessel permeability, vessel constriction/relaxation, and immune cell behavior (Wallace, 2002).