Docosanoids (FA04)

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Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are precursors of novel oxygenated bioactive products that were identified in resolving inflammatory exudates (Serhan et al. 2000). They were named resolvins, docosatrienes and neuroprotectins and, unlike other omega-3 fatty acids products, are present in anti-inflammatory and immunoregulatory processes.

The classification of resolvins, the products of interaction between aspirin acetylated COX-2 and omega-3 polyunsaturated fatty acids, is based on their origin:

Resolvins originated from EPA constitute resolvins of E series (Resolvin E1 or RvE1) and those from DHA constitute resolvins of D series (Resolvin D1 or RvD1). The anti-inflammatory and neuroprotective products, which carry conjugated triene structures, are denoted as docosatrienes (DT) and docosatrienes that contain dihydroxy acid are termed neuroprotectins (NPD1) (Sehran et al. 2004). Both resolvins of D and E series are potent regulators of PMN infiltration in brain and their strong anti-inflammatory properties are mediated partially by modulation of cytokines expression (Serhan et al. 2002, Serhan et al. 2003). Additionally, RvE1 reduces dermal inflammation, peritonitis, dendritic cell migration and IL-12 production (Arita et al. 2005).

Figure 24. Essential polyunsaturated fatty acids as precursors for bioactive lipid mediators (Serhan, 2005)
Figure 24. Essential polyunsaturated fatty acids as precursors for bioactive lipid mediators (Serhan, 2005)

The anti-inflammatory action of RvE1 is mediated via G-protein-coupled receptor, ChemR23 (Arita et al. 2005), which is upregulated by cytokines during resolution; a process that counter regulates proinflammatory gene expression and cell trafficking and stimulates inflammatory cell clearance (Nathan, 2002). ChemR23 is structurally similar to LXA4 receptor and similarly can interact with other lipid ligands. RvE1 may serve as a paracrine or autocrine signal during resolution to repress NF-kB activation and further cytokine synthesis.

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