Epi-lipoxins are trihydroxy (i.e. containing 3

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

residues) metabolites of arachidonic acid. They are 15''R''-epimers of their

lipoxin A lipoxin (LX or Lx), an acronym for lipoxygenase interaction product, is a bioactive autacoid metabolite of arachidonic acid made by various cell types. They are categorized as nonclassic eicosanoids and members of the specialized pro-resolvin ...

counterparts; that is, the epi-lipoxins, 15-epi-lipoxin A4 (15-epi-LxA4) and 15-epi-lipoxin B4 (15-epi-LXB4), differ from their respective lipoxin A4 (LxA4) and lipoxin B4 (LxB4) epimers in that their 15-hydroxy residue has ''R'' rather than ''S'' chirality. Formulae for these lipoxins (Lx) are: *LxA4: 5''S'',6''R'',15''S''-trihydroxy-7''E'',9''E'',11''Z'',13''E''-ETE *LxB4: 5''S'',14''R'',15''S''-trihydroxy-6''E'',8''Z'',10''E'',12''E''-ETE *15-epi-LxA4: 5''S'',6''R'',15''R''-trihydroxy-7''E'',9''E'',11''Z'',13''E''-eicosatetraenoic acid *15-epi-LxB4: 5''S'',14''R'',15''R''-trihydroxy-6''E'',8''Z'',10''E'',12''E''-eicosatrienoic acid The two-epi-Lx's as well as the two lx's are

nonclassic eicosanoid Nonclassic eicosanoids are biologically active signaling molecules made by oxygenation of twenty-carbon fatty acids other than the classic eicosanoids. Terminology : "Eicosanoid" is the collective term for oxygenated derivatives of three diffe ...

s that, like other members of the

specialized pro-resolving mediators Specialized pro-resolving mediators (SPM, also termed specialized proresolving mediators) are a large and growing class of cell signaling molecules formed in cells by the metabolism of polyunsaturated fatty acids (PUFA) by one or a combination of ...

class of autocoids, form during and act to resolve inflammatory responses. Synthesis of the lipoxins typically involves a

lipoxygenase Lipoxygenases () are a family of (non-heme) iron-containing enzymes most of which catalyze the dioxygenation of polyunsaturated fatty acids in lipids containing a cis,cis-1,4- pentadiene into cell signaling agents that serve diverse roles as aut ...

enzyme which acts to add a 15''S''-hydroxyl residue to the lipoxin precursor, arachidonic acid, whereas synthesis of the epi-lipoxins involves

aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...

-pretreated

cyclooxygenase 2 Prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase) (The HUGO official symbol is PTGS2; HGNC ID, HGNC:9605), also known as cyclooxygenase-2 or COX-2, is an enzyme that in humans is encoded by the ''PTGS2'' gene ...

or a

cytochrome P450 Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various co ...

enzyme which adds a 15''R''-hydroxyl residue to arachidonic acid. In acknowledgement of the role played by aspirin-treated cyclooxygenase 2 in forming these products, the epi-lipoxins are sometimes termed ATL which stands for Aspirin-Triggered Lipoxins. The counter-regulatory role of the epi-lipoxins in serving as ''stop'' signals for diverse

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

responses is detailed at the

site.

References

Eicosanoids {{biochem-stub

See also

References