Person:

Dalli, Jesmond P

Mechanisms underlying delays in resolution programs of inflammation are of interest for many diseases. Here, we addressed delayed resolution of inflammation and identified specific microRNA (miR)-metabolipidomic signatures. Delayed resolution initiated by high-dose challenges decreased miR-219-5p expression along with increased leukotriene B4 (5-fold) and decreased (~3-fold) specialized pro-resolving mediators, e.g. protectin D1. Resolvin (Rv)E1 and RvD1 (1 nM) reduced miR-219-5p in human macrophages, not shared by RvD2 or PD1. Since mature miR-219-5p is produced from pre-miRs miR-219-1 and miR-219-2, we co-expressed in human macrophages a 5-lipoxygenase (LOX) 3′UTR-luciferase reporter vector together with either miR-219-1 or miR-219-2. Only miR-219-2 reduced luciferase activity. Apoptotic neutrophils administered into inflamed exudates in vivo increased miR-219-2-3p expression and PD1/NPD1 levels as well as decreased leukotriene B4. These results demonstrate that delayed resolution undermines endogenous resolution programs, altering miR-219-2 expression, increasing pro-inflammatory mediators and compromising SPM production that contribute to failed catabasis and homeostasis.

Maresins are a new family of anti-inflammatory and pro-resolving lipid mediators biosynthesized from docosahexaenoic acid (DHA) by macrophages. Here we identified a novel pro-resolving product, 13R,14S-dihydroxy-docosahexaenoic acid (13R,14S-diHDHA), produced by human macrophages. PCR mapping of 12-lipoxygenase (12-LOX) mRNA sequence in human macrophages and platelet showed that they are identical. This human 12-LOX mRNA and enzyme are expressed in monocyte-derived cell lineage, and enzyme expression levels increase with maturation to macrophages or dendritic cells. Recombinant human 12-LOX gave essentially equivalent catalytic efficiency (kcat/KM) with arachidonic acid (AA) and DHA as substrates. Lipid mediator metabololipidomics demonstrated that human macrophages produce a novel bioactive product 13,14-dihydroxy-docosahexaenoic acid in addition to maresin-1, 7R,14S-dihydroxy-4Z,8E,10E,12Z,16Z,19Z-docosahexaenoic acid (MaR1). Co-incubations with human recombinant 12-LOX and soluble epoxide hydrolase (sEH) demonstrated that biosynthesis of 13,14-dihydroxy-docosahexaenoic acid (13,14-diHDHA) involves the 13S,14S-epoxy-maresin intermediate produced from DHA by 12-LOX, followed by conversion via soluble epoxide hydrolase (sEH). This new 13,14-diHDHA displayed potent anti-inflammatory and pro-resolving actions, and at 1 ng reduced neutrophil infiltration in mouse peritonitis by ∼40% and at 10 pM enhanced human macrophage phagocytosis of zymosan by ∼90%. However, MaR1 proved more potent than the 13R,14S-diHDHA at enhancing efferocytosis with human macrophages. Taken together, the present findings demonstrate that macrophages produced a novel bioactive product identified in the maresin metabolome as 13R,14S-dihydroxy-docosahexaenoic acid, from DHA via conversion by human 12-LOX followed by sEH. Given its potent bioactions, we coined 13R,14S-diHDHA maresin 2 (MaR2).