Inflammation and its natural resolution are host-protective responses triggered by infection or injury. The resolution phase of inflammation is regulated by enzymatically produced specialized pro-resolving mediators. We recently identified a new class of peptide-conjugated specialized pro-resolving mediators that carry potent tissue regenerative actions that belong to the protectin family and are coined protectin conjugates in tissue regeneration (PCTR). Herein, with the use of microbial-induced peritonitis in mice and liquid chromatography-tandem mass spectrometryebased lipid mediator metabololipidomics, we found that PCTR1 is temporally regulated during self-resolving infection. When administered at peak of inflammation, PCTR1 enhanced macrophage recruitment and phagocytosis of Escherichia coli, decreased polymorphonuclear leukocyte infiltration, and counter-regulated inflammation-initiating lipid mediators, including prostaglandins. In addition, biologically produced PCTR1 promoted human monocyte and macrophage migration in a dose-dependent manner (0.001 to 10.0 nmol/L). We prepared PCTR1 via organic synthesis and confirmed that synthetic PCTR1 increased macrophage and monocyte migration, enhanced macrophage efferocytosis, and accelerated tissue regeneration in planaria. With human macrophage subsets, PCTR1 levels were significantly higher in M2 macrophages than in M1 phenotype, along with members of the resolvin conjugates in tissue regeneration and maresin conjugate families. In contrast, M1 macrophages gave higher levels of cysteinyl leukotrienes. Together, these results demonstrate that PCTR1 is a potent monocyte/macrophage agonist, regulating key anti-inflammatory and pro-resolving processes during bacterial infection. (Am J Pathol 2016, 186: 962e973; http://dx

The polyunsaturated lipid mediator PD1n-3 DPA (5) was recently isolated from self-resolving inflammatory exudates of 5 and human macrophages. Herein, the first total synthesis of PD1n-3 DPA (5) is reported in 10 steps and 9% overall yield. These efforts, together with NMR data of its methyl ester 6, confirmed the structure of 5 to be (7Z,10R,11E,13E,15Z,17S,19Z)-10,17-dihydroxydocosa-7,11,13,15,19-pentaenoic acid. The proposed biosynthetic pathway, with the involvement of an epoxide intermediate, was supported by results from trapping experiments. In addition, LC-MS/MS data of the free acid 5, obtained from hydrolysis of the synthetic methyl ester 6, matched data for the endogenously produced biological material. The natural product PD1n-3 DPA (5) demonstrated potent anti-inflammatory properties together with pro-resolving actions stimulating human macrophage phagocytosis and efferocytosis. These results contribute new knowledge on the n-3 DPA structure-function of the growing numbers of specialized pro-resolving lipid mediators and pathways.

The n-3 polyunsaturated fatty acids act as substrates during the resolution phase of acute inflammation for the biosynthesis of specialized pro-resolving lipid mediators. One premier example is the C22-dihydroxy-polyunsaturated fatty acid protectin D1 (1). The human 15-lipoxygenase type I, via stereoselective processes and with docosahexaenoic acid as the substrate, enables the formation of this specialized pro-resolving lipid mediator. Herein, based on results from LC/MS-MS metabololipidomics, support is presented for the apprehended biosynthesis of 1 in human macrophages occurs via the intermediate 16S,17S-epoxy-protectin (5). Stereochemical pure 5 was obtained using the Katsuki-Sharpless epoxidation protocol, establishing the chirality at the C16 and C17 atoms, one Z-selective reduction as well as E- and Z-stereoselective Wittig reactions. In addition, information on the non-enzymatic aqueous hydrolysis products and the half-life of 16S,17S-epoxy-protectin (5) is presented.

Docosahexaenoic acid (DHA), a polyunsaturated ω-3 fatty acid enriched in oily fish, contributes to better health by affecting multiple targets. Large-conductance Ca 2+ -and voltage-gated Slo1 BK channels are directly activated by nanomolar levels of DHA. We investigated DHA-channel interaction by manipulating both the fatty acid structure and the channel composition through the site-directed incorporation of unnatural amino acids. Electrophysiological measurements show that the para-group of a Tyr residue near the ion conduction pathway has a critical role. To robustly activate the channel, ionization must occur readily by a fatty acid for a good efficacy, and a long nonpolar acyl tail with a Z double bond present at the halfway position for a high affinity. The results suggest that DHA and the channel form an ion-dipole bond to promote opening and demonstrate the channel druggability. DHA, a marine-derived nutraceutical, represents a promising lead compound for rational drug design and discovery. -4,7,10,13,16,19-hexaenoic acid], found abundantly in oily fish, are believed to have many health-promoting effects (1). For example, select ω-3 PUFAs may decrease cardiovascular disease risk (2). Furthermore, human studies suggest that ω-3 PUFAs may lower blood pressure in some individuals (3). Thus, PUFAs such as DHA are natural nutraceuticals with great potential as lead compounds for rational drug design and discovery. To be successful, such an effort requires clear mechanistic understanding of the interactions between PUFAs and their effectors (4); however, the molecular targets of PUFAs and the mechanisms of action are only beginning to be revealed.One of the high-affinity targets of PUFAs is the large-conductance Ca 2+ -and voltage-gated K + (Slo1 BK) channel (5), whose activation in vascular smooth muscle cells facilitates vessel relaxation (6). Vascular Slo1 BK channels made of four pore-forming Slo1 and auxiliary β1 subunits (Slo1 + β1) are potently and reversibly activated by DHA with a nanomolar level of EC 50 , and this effect contributes to the hypotensive action of DHA in wild-type mice but not in mice with the gene encoding the channel (KCNMA1) disrupted (5).The function of the Slo1 BK channel can be electrophysiologically monitored with high precision to produce quantitative results amenable to mechanistic interpretations (7,8). Such in vitro studies show that DHA biases the ion conduction gate of the channel toward the open conformation without any need for activation of the channel's Ca 2+ sensors in the intracellular domain or transmembrane voltage sensor domains (VSDs) (5). Structurally, the action of DHA depends on a Tyr residue [Y318 in human Slo1 (hSlo1)] near the intracellular end of the ion conduction pathway; the mutation Y318S abolishes the activating effect of DHA (9).The exact role of Y318 in mediating the effect of DHA, however, is not clear. Some clues may be gained from interactions of other proteins with PUFAs. Extracellular DHA regulates voltagegated K + channels by interacting with ...

A convergent stereoselective synthesis of the potent anti-inflammatory, proresolving and neuroprotective lipid mediator protectin D1 (2) has been achieved in 15% yield over eight steps. The key features were a stereocontrolled Evans-aldol reaction with Nagao’s chiral auxiliary and a highly selective Lindlar reduction of internal alkyne 23, allowing the sensitive conjugated E,E,Z-triene to be introduced late in the preparation of 2. The UV and LC/MS-MS data of synthetic protectin D1 (2) matched those obtained from endogenously produced material