Docosanoid

In biochemistry, docosanoids are signaling molecules made by the metabolism of twenty-two-carbon fatty acids (EFAs), especially the omega-3 fatty acid, docosahexaenoic acid (DHA) (i.e. 4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoic acid) by lipoxygenase, cyclooxygenase, and cytochrome P450 enzymes. Other docosanoids are metabolites of n-3 docosapentaenoic acid (DPA) (i.e. 7Z,10Z,13Z,16Z,19Z-docosapentaenoic acid, or clupanodonic acid), n-6 DPA (i.e. 4Z,7Z,10Z,13Z,16Z-docosapentaenoic acid, or osbond acid), and docosatetraenoic acid (i.e. 7Z,10Z,13Z,16Z-docosatetraenoic acid, DTA, or adrenic acid). Prominent docosanoid metabolites of DPA and n-3 DHA are members of the specialized pro-resolving mediators class of polyunsaturated fatty acid metabolites that possess potent anti-inflammation, tissue healing, and other activities.

Prominent docosanoids

Specialized proresolving mediator docosanoids

Potently bioactive agents of the specialized proresolving mediator class include:

• DHA-derived resolvins (Rvs) of the D series: RvD1, RvD2, RvD3, RvD4, RvD5, RvD6, AT-RvD1, AT-RvD2, AT-RvD3, AT-RvD4, AT-RvD5, and AT-RvD6.
• n-3 DPA-derived resolvins of the D series (RvD1_n-3, RvD2_n-3, and RvD5_n-3) and the T series (RvT1, RvT2, RvT3, and RvT4).
• DHA-derived neuroprotectins, also termed protectins: PD1, PDX, 17-epi-PD1, and 10-epi-PD1.
• n-3 DPA derived protectins: PD1_n-3 and PD2_n-3.
• DHA-derived maresins: MaR1, MaR2, 7-epi-Mar1, Mar-L1, and Mar-L2.
• n-3 DPA-derived maresins: Mar1_n-3, Mar2_n-3, and Mar3_n-3.

These DHA metabolites possess anti-inflammation and tissue-protection activities in animal models of inflammatory diseases; they are proposed to inhibit innate immune responses and thereby to protect from and to resolve a wide range of inflammatory responses in animals and humans. These metabolites are also proposed to contribute to the anti-inflammatory and other beneficial effects of dietary omega-3 fatty acids by being metabolized to them.^[1][2][3][4]

Neurofuran docosanoids

DHA can be converted non-enzymatically by free radical-mediated peroxidation to 8 different neurofuran regioisomers termed neuroprostanes and neurofuranes including 4-, 7-, 10-, 11-, 13-, 14-, 17-, and 20-series neurofurans/neuroporstanes for a total of 128 different racemic compounds. The most studied DHA-derived of these products are members of the 4-series, neurofuran 4-F_αneuroprostane and 4(RS)-ST-Δ6-8-neurofurane. These metabolites have been used mainly as biomarkers of oxidative stress that are formed in nerve tissues of the central nervous system.^[5][6]

Hydroxy-docosanoids

Cells metabolize DHA to 17S-hydroperoxy-4Z,7Z,10Z,13Z,15E,19Z-docosahexaenoic acid (17-HpDHA) and then rapidly reduce this hydroperoxide to 17S-hydroxy-4Z,7Z,10Z,13Z,15E,19Z-docosahexaenoic acid (17-HDHA) and similarly metabolize DHA to 13S-hydroperoxy-4Z,7Z,10Z,14Z,16Z,19Z-docosahexaenoic acid (13-HpDHA) and then to 13S-hydroxy-4Z,7Z,10Z,14Z,16Z,19Z-docosahexaenoic acid (13-HDHA). 17-HDHA exhibits potent in vitro as well as in vivo (animal model) anti-inflammatory activity while 17-HpDHA and to a lesser extent 17-HDHA inhibit the growth of cultured human breast cancer cells.^[7][8] Other SPM docosanoids, e.g. RvD1 and RvD2, have anti-growth effects against cancer cells in animal models.^[9]

Oxo-docosanoids

Cells can metabolize DHA to products that possess an oxo (i.e. ketone) residue. These products include 13-oxo-DHA (termed EFOXD6) and 17-oxo-DHA (termed 18-EFOXD6). Both oxo metabolites possess anti-inflammatory activity as assesses in in vitro systems (see Specialized proresolving mediators § Oxo-DHA and oxo-DPA metabolites).^[10]

DTA-derived docosanoids

Cyclooxygenase and cytochrome P450 oxidase act upon docosatetraenoic acid to produce dihomoprostaglandins,^[11] dihomo-epoxyeicosatrienoic acids,^[12] and dihomo-EETs.^[13]

References

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2. Serhan CN, Chiang N, Dalli J, Levy BD (2015). "Lipid mediators in the resolution of inflammation". Cold Spring Harbor Perspectives in Biology. 7 (2): a016311. doi:10.1101/cshperspect.a016311. PMC 4315926. PMID 25359497.
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7. Chiu CY, Gomolka B, Dierkes C, Huang NR, Schroeder M, Purschke M, Manstein D, Dangi B, Weylandt KH (2012). "Omega-6 docosapentaenoic acid-derived resolvins and 17-hydroxydocosahexaenoic acid modulate macrophage function and alleviate experimental colitis". Inflammation Research. 61 (9): 967–76. doi:10.1007/s00011-012-0489-8. PMID 22618200. S2CID 18265905.
8. O'Flaherty JT, Hu Y, Wooten RE, Horita DA, Samuel MP, Thomas MJ, Sun H, Edwards IJ (2012). "15-lipoxygenase metabolites of docosahexaenoic acid inhibit prostate cancer cell proliferation and survival". PLOS ONE. 7 (9): e45480. Bibcode:2012PLoSO...745480O. doi:10.1371/journal.pone.0045480. PMC 3447860. PMID 23029040.
9. Serhan CN, Chiang N, Dalli J (2015). "The resolution code of acute inflammation: Novel pro-resolving lipid mediators in resolution". Seminars in Immunology. 27 (3): 200–15. doi:10.1016/j.smim.2015.03.004. PMC 4515371. PMID 25857211.
10. Weylandt KH (2015). "Docosapentaenoic acid derived metabolites and mediators - The new world of lipid mediator medicine in a nutshell". European Journal of Pharmacology. 785: 108–115. doi:10.1016/j.ejphar.2015.11.002. PMID 26546723.
11. Campbell WB, Falck JR, Okita JR, Johnson AR, Callahan KS (1985). "Synthesis of dihomoprostaglandins from adrenic acid (7,10,13,16-docosatetraenoic acid) by human endothelial cells". Biochim. Biophys. Acta. 837 (1): 67–76. doi:10.1016/0005-2760(85)90086-4. PMID 3931686.
12. Kopf PG, Zhang DX, Gauthier KM, Nithipatikom K, Yi XY, Falck JR, Campbell WB (2010). "Adrenic acid metabolites as endogenous endothelium-derived and zona glomerulosa-derived hyperpolarizing factors". Hypertension. 55 (2): 547–54. doi:10.1161/HYPERTENSIONAHA.109.144147. PMC 2819927. PMID 20038752.
13. Yi XY, Gauthier KM, Cui L, Nithipatikom K, Falck JR, Campbell WB (May 2007). "Metabolism of adrenic acid to vasodilatory 1α,1β-dihomo-epoxyeicosatrienoic acids by bovine coronary arteries". Am J Physiol Heart Circ Physiol. 292 (5): H2265–74. doi:10.1152/ajpheart.00947.2006. PMID 17209008. S2CID 86090552.