Expression and function of resolvin RvD1(n-3 DPA) receptors in oral epithelial cells

Chronic inflammatory responses can inflict permanent damage to host tissues. Specialized pro-resolving mediators downregulate inflammation but also can have other functions. The aim of this study was to examine whether oral epithelial cells express the receptors FPR2/ALX and DRV1/GPR32, which bind RvD1(n-3 DPA) , a recently described pro-resolving mediator derived from omega-3 docosapentaenoic acid (DPA), and whether RvD1(n-3 DPA) exposure induced significant responses in these cells. Gingival biopsies were stained using antibodies to FPR2/ALX and DRV1/GPR32. Expression of FPR2/ALX and DRV1/GPR32 was examined in primary oral epithelial cells by qRT-PCR, flow cytometry, and immunofluorescence. The effect of RvD1(n-3 DPA) on intracellular calcium mobilization and transcription of beta-defensins 1 and 2, and cathelicidin was evaluated by qRT-PCR. FPR2/ALX and DRV1/GPR32 were expressed by gingival keratinocytes in situ. In cultured oral epithelial cells, FPR2/ALX was detected on the cell surface, whereas FPR2/ALX and DRV1/GPR32 were detected intracellularly. Exposure to RvD1(n-3 DPA) induced intracellular calcium mobilization, FPR2/ALX internalization, DRV1/GPR32 translocation to the nucleus, and significantly increased expression of genes coding for beta-defensin 1, beta-defensin 2, and cathelicidin. This shows that the signal constituted by RvD1(n-3 DPA) is recognized by oral keratinocytes and that this can strengthen the antimicrobial and regulatory potential of the oral epithelium

Enantioselective Organocatalyzed Bromolactonizations: Applications in Natural Product Synthesis

Asymmetric bromolactonization reactions of δ-unsaturated carboxylic acids have been investigated in the presence of 10 chiral squaramide hydrogen-bonding organocatalysts. The best catalyst enabled the cyclization of several 5-arylhex-5-enoic acids into the corresponding bromolactones with up to 96% ee and in high to excellent chemical yields. The reported catalysts are prepared in a straightforward manner in two steps from dimethyl squarate. The utility of the developed protocol was demonstrated in highly enantioselective syntheses of the sesquiterpenoids (−)-gossoronol and (−)-boivinianin B. Both natural products were obtained in ≥99% enantiomeric excess

Asymmetric Iodolactonization Utilizing Chiral Squaramides

Asymmetric iodolactonization of γ- and δ-unsaturated carboxylic acids has been explored in the presence of six different chiral organocatalysts <b>5</b>–<b>8</b>. The catalyst <b>6b</b> was found to facilitate the cyclization of 5-arylhex-5-enoic acids <b>1</b> to the corresponding iodolactones <b>2</b> with up to 96% <i>ee</i>. By this protocol, unsaturated carboxylic acids are converted enantioselectively to synthetically useful δ-lactones in high yields using commercially available NIS. Apparently, both hydrogen bonding and aryl/aryl interactions are important for efficient stereodifferentiation

Synthesis, Biological Investigation, and Structural Revision of Sielboldianin A

The two <i>ar</i>-bisabol sesquiterpenoids (+)-sielboldianin A (<b>1</b>) and (+)-sielboldianin B (<b>2</b>) were isolated from the stem bark of the plant <i>Fraxinus sielboldiana</i> and belong to a medicinally interesting class of natural products used in traditional Chinese medicine. Herein the total synthesis of the proposed structure of (+)-sielboldianin A (<b>1</b>) is reported using an organocatalyzed enantioselective bromolactonization protocol. X-ray analysis of a key intermediate together with specific rotation values and NOESY data of the synthesized product enabled the revision of the absolute configuration of the natural product (+)-sielboldianin A to (7<i>R</i>,10<i>R</i>). Studies on the antioxidant effects using two cell-based assays were conducted. These studies revealed that the enantiomer of <b>1</b> exhibited antioxidant effects with IC₅₀ values of 18 ± 3 μM in a cellular lipid peroxidation antioxidant activity assay. Moreover, (−)-<b>1</b> showed strong protective effects against reactive oxygen species in a cell-based antioxidant activity assay (IC₅₀ = 31 ± 5 μM). In addition, the two <i>ar</i>-sesquiterpenoids (−)-boivinianin B and (−)-gossoronol showed no effect in either assay. No cytotoxic activity in the K562 cancer cell line was observed for the three sesquiterpenoids tested (IC₅₀ > 50 μM)

Total Synthesis of the Lipid Mediator PD1n-3 DPA: Configurational Assignments and Anti-inflammatory and Pro-resolving Actions

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

Molecular modelling, synthesis, and biological evaluations of a 3,5-disubstituted isoxazole fatty acid analogue as a PPARα-selective agonist

The peroxisome proliferator activated receptors (PPARs) are important drug targets in treatment of metabolic and inflammatory disorders. Fibrates, acting as PPARα agonists, have been widely used lipid-lowering agents for decades. However, the currently available PPARα targeting agents show low subtype-specificity and consequently a search for more potent agonists have emerged. In this study, previously isolated oxohexadecenoic acids from the marine algae Chaetoceros karianus were used to design a PPARα-specific analogue. Herein we report the design, synthesis, molecular modelling studies and biological evaluations of the novel 3,5-disubstituted isoxazole analogue 6-(5-heptyl-1,2-oxazol-3-yl)hexanoic acid (1), named ADAM. ADAM shows a clear receptor preference and significant dose-dependent activation of PPARα (EC50 = 47 µM) through its ligand-binding domain (LBD). Moreover, ADAM induces expression of important PPARα target genes, such as CPT1A, in the Huh7 cell line and primary mouse hepatocytes. In addition, ADAM exhibits a moderate ability to regulate PPARγ target genes and drive adipogenesis. Molecular modelling studies indicated that ADAM docks its carboxyl group into opposite ends of the PPARα and -γ LBD. ADAM interacts with the receptor-activating polar network of amino acids (Tyr501, His447 and Ser317) in PPARα, but not in PPARγ LBD. This may explain the lack of PPARγ agonism, and argues for a PPARα-dependent adipogenic function. Such compounds are of interest towards developing new lipid-lowering remedies

Synthesis of the 16<i>S</i>,17<i>S</i>‑Epoxyprotectin Intermediate in the Biosynthesis of Protectins by Human Macrophages

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 (<b>1</b>). 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 <b>1</b> in human macrophages occurring via the intermediate 16<i>S</i>,17<i>S</i>-epoxyprotectin (<b>5</b>). Stereochemically pure <b>5</b> was obtained using the Katsuki–Sharpless epoxidation protocol, establishing the chirality at the C16 and C17 atoms, one <i>Z</i>-selective reduction, and <i>E</i>- and <i>Z</i>-stereoselective Wittig reactions. In addition, information on the nonenzymatic aqueous hydrolysis products and the half-life of 16<i>S</i>,17<i>S</i>-epoxyprotectin (<b>5</b>) is presented

Synthesis and Anti-inflammatory and Pro-resolving Activities of 22-OH-PD1, a Monohydroxylated Metabolite of Protectin D1

Protectin D1 (PD1 (<b>3</b>)), a C22-dihydroxylated polyunsaturated fatty acid biosynthesized from all-<i>Z</i>-docosahexaenoic acid, belongs to the new family of endogenous mediators referred to as specialized pro-resolving lipid mediators. PD1 (<b>3</b>) is a natural product that displays potent anti-inflammatory properties together with pro-resolving actions including inhibition of polymorphonuclear leukocyte (PMN) infiltration and promotion of macrophage phagocytosis and efferocytosis. Given its potent endogenous actions, this compound has entered several clinical development programs. Little has been reported on the metabolism of PD1 (<b>3</b>). The synthesis and biological evaluations of the ω-22 monohydroxylated metabolite of PD1 (<b>3</b>), named herein 22-OH-PD1 (<b>6</b>), are presented. LC-MS/MS data of the free acid <b>6</b>, obtained from hydrolysis of the synthetic methyl ester <b>7</b>, matched data for the endogenously produced 22-OH-PD1 (<b>6</b>). Compound <b>6</b> exhibited potent pro-resolving actions by inhibiting PMN chemotaxis in vivo and in vitro comparable to its precursor PD1 (<b>3</b>) and decreased pro-inflammatory mediator levels in inflammatory exudates. The results reported herein provide new knowledge of the metabolism of the protectin class of specialized pro-resolving mediators

Total Synthesis of the Lipid Mediator PD1_{n‑3 DPA}: Configurational Assignments and Anti-inflammatory and Pro-resolving Actions

The polyunsaturated lipid mediator PD1_n‑3 DPA (<b>5</b>) was recently isolated from self-resolving inflammatory exudates of <b>5</b> and human macrophages. Herein, the first total synthesis of PD1_n‑3 DPA (<b>5</b>) is reported in 10 steps and 9% overall yield. These efforts, together with NMR data of its methyl ester <b>6</b>, confirmed the structure of <b>5</b> to be (7<i>Z</i>,10<i>R</i>,11<i>E</i>,13<i>E</i>,15<i>Z</i>,17<i>S</i>,19<i>Z</i>)-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 <b>5</b>, obtained from hydrolysis of the synthetic methyl ester <b>6</b>, matched data for the endogenously produced biological material. The natural product PD1_n‑3 DPA (<b>5</b>) 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