Eicosanoids are signaling molecules produced by the enzymatic or non-enzymatic oxidation of arachidonic acid or other polyunsaturated fatty acids (PUFAs) with 20 carbon units in length, identical to arachidonic acid.
Eicosanoids are a subcategory of oxylipins, which are oxidized fatty acids with varying carbon unit lengths. They differ from other oxylipins in their relevance as cell signaling molecules. Eicosanoids play a role in a variety of physiological and pathological processes, including mounting or inhibiting inflammation, allergy, fever, and other immune responses; regulating pregnancy and childbirth; contributing to pain perception; regulating cell growth; controlling blood pressure; and modulating regional blood flow to tissues.
Eicosanoids most commonly serve as autocrine signalling agents to affect their cells of origin or as paracrine signalling agents to impact cells in close proximity to their cells of origin when executing their functions. Eicosanoids may also act as endocrine agents, influencing the function of cells in other parts of the body.
Eicosanoids are divided into several subfamilies, the most well-known of which are prostaglandins, thromboxanes, leukotrienes, lipoxins, resolvins, and eoxins. There are at least four different series of metabolites for each subfamily, two series generated from ω-6 PUFAs (arachidonic and dihomo-gamma-linolenic acids), one series derived from ω-3 PUFA (eicosapentaenoic acid), and one series produced from ω-9 PUFA (mead acid). This distinction between subfamilies is crucial. ω-6 PUFA cannot be converted into ω-3 PUFA by mammals, including humans. As a result, tissue levels of ω-6 and ω-3 PUFAs, as well as their eicosanoid metabolites, are linked to dietary ω-6 vs ω-3 PUFA consumption.
Because certain metabolites from the ω-6 and ω-3 PUFA series have almost diametrically opposing physiological and pathological activities, it’s been suggested that the negative consequences of a ω-6 PUFA-rich diet reflect excessive production and activities of ω-6 PUFA-derived eicosanoids, whereas the beneficial effects of a ω-3 PUFA-rich diet reflect excessive production and activities of ω-3 PUF-derived eicosanoids.