Maresin 1 ( MaR1 or 7 R,14 S-dihydroxy-4 Z,8 E,10 E,12 Z,16 Z,19 Z-docosahexaenoic acid) is a macrophage-derived mediator of inflammation resolution coined from macrophage mediator in resolving inflammation. Maresin 1, and more recently defined maresins, are 12-lipoxygenase-derived metabolites of the omega-3 fatty acid, docosahexaenoic acid (DHA), that possess potent anti-inflammatory, pro-resolving, protective, and pro-healing properties similar to a variety of other members of the specialized proresolving mediators (SPM) class of polyunsaturated fatty acid (PUFA) metabolites. SPM are dihydroxy, trihydroxy, and epoxy-hydroxy metabolites of long chain PUFA made by certain dioxygenase enzymes viz., and . In addition to the maresins, this class of mediators includes: the 15-lipoxygenase (i.e. ALOX15 and/or possibly ALOX15B)-derived lipoxin A4 and B4 metabolites of the omega 6 fatty acid, arachidonic acid; the cyclooxygenase 2-derived resolvin E series metabolites of the omega 3 fatty acid, eicosapentaenoic acid; certain 15-lipoxygenase-derived resolvin D series metabolites of DHA; certain other 15-lipoxygenase-derived protectin D1 and related metabolites of DHA; and the more recently defined and therefore less fully studied 15-lipoxygenase-derived resolvin Dn-3DPA metabolites of the omega-3 fatty acid n-3 docosapentaenoic acid (n-3 DPA or clupanodonic acid), the cyclooxygenase 2-derived resolvin T metabolites of this clupanodonic acid, and the 15-lipoxygenase-derived products of the N-acetylated fatty acid amide of the DHA metabolite, docosahexaenoyl ethanolamide.
MaR1 enhances the uptake (i.e. stimulates the efferocytosis) of apoptotic human neutrophils by human macrophages, stimulates macrophage phagocytosis, and limits the infiltration of neutrophils into the inflamed peritoneum of mice. In a murine model of acute respiratory distress syndrome, MaR1 generation was detected in a temporally regulated manner with early MaR1 production was dependent on platelet-neutrophil interactions; intravascular MaR1 was organ-protective, leading to decreased lung neutrophils, edema, tissue hypoxia, and prophlogistic mediators.
In a murine model of a self-limiting pulmonary allergic reaction, MaR1 reduced lung inflammation. It appeared to act at least in part by augmenting the generation of regulatory T cells which interacted with Group 2 innate lymphoid cells (i.e. helper T cell lymphocytes) to markedly suppress the production of two , interleukin-5 and interleukin-13, implicated in mediating allergic reactions. MaR1 accelerated tissue regeneration in experimentally injured planaria worms. In particular, it increasing the rate of head reappearance in beheaded worms. And, MaR1 reduced neuropathic pain in a mouse model by inhibiting a neuron ion channel, TRPV1, and thereby blocking capsaicin-induced inward currents and neuron excitation.
MaR2 possesses at least some of the activities ascribed to MaR1. It enhances human macrophage phagocytosis of particles and efferocytosis of apoptotic human neutrophils and reduces neutrophil infiltration into the inflamed peritoneum of mice. Its potencies in producing these responses are similar to those of MaR1.
13( S),14( S)-epoxy-maresin inhibits the production of the arachidonic acid metabolite, leukotriene B4 (LTB4), by directly inactivating the enzyme, leukotriene-A4 hydrolase, which converts the LTB4 precursor, leukotriene A4, to LTB4; this effect may contribute to the resolution of inflammatory responses by reducing the production of the proinflammatory mediator, LTB4.
Further studies are needed to determine if maresins play a functional role in resolving inflammation, promoting wound healing, or limiting neuropathic pain and/or if maresins or their metabolism-resistant analogs are clinically useful in treating the latter conditions.
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