Gram scale synthesis of specialized pro-resolving mediator 17(S)-HDHA using lipoxygenase enhanced by water-soluble reducing agent TCEP

Lipoxygenase catalyzed metabolites derived from docosahexaenoic acid are promising antitumor agents against breast cancer

Docosahexaenoic acid (DHA) is known to inhibit breast cancer in the rat. Here we investigated whether DHA itself or select metabolites can account for its antitumor action. We focused on metabolites derived from the lipoxygenase (LOX) pathway since we previously showed that they were superior anti-proliferating agents compared to DHA; 4-OXO-DHA was the most potent. A lipidomics approach detected several LOX-metabolites in plasma and the mammary gland in rats fed DHA; we also identified for the first time, 4-OXO-DHA in rat plasma. In a reporter assay, 4-OXO-DHA and 4-HDHA were more effective activators of PPARɣ than DHA. In breast cancer cell lines, 4-OXO-DHA induced PPARɣ and 15-hydroxyprostaglandin dehydrogenase (15-PGDH) but inhibited the activity of NF-κB and suppressed PI3K and mTOR signaling. Because of the structural characteristics of 4-OXO-DHA (Michael acceptor), not shared by any of the other hydroxylated-DHA, we used MS and showed that it can covalently modify the cysteine residue of NF-κB. We have also shown that the chemopreventive effect of DHA is associated with significant reduction of PGE₂ levels, in both rat mammary tumors induced by MNU and non-involved mammary tissues. Collectively, our results indicate that 4-OXO-DHA is the metabolite of choice in future chemoprevention studies.

First total syntheses of the pro-resolving lipid mediators 7(S),13(R),20(S)-Resolvin T1 and 7(S),13(R)-Resolvin T4

The first total syntheses of the pro-resolving lipid mediators 7(S),13(R),20(S)-Resolvin T1 [7(S),13(R),20(S)-RvT1] and 7(S),13(R)-Resolvin T4 [7(S),13(R)-RvT4], derived from n-3 docosapentaenoic acid (n-3 DPA), are described. 7(S),13(R),20(S)-RvT1 was prepared from 7(S),13(R)-RvT4 via an enzymatic lipoxidase reaction. 7(S),13(R)-RvT4 was obtained by total synthesis where the chiral centers at C7 and C13 where introduced by a Noyori transfer hydrogenation and a chiral pool strategy respectively. Wittig reactions, Sonogashira coupling and Boland Zn(Cu/Ag) reduction were the key steps in the synthesis.

Lyophilized extracts from vegetable flours as valuable alternatives to purified oxygenases for the synthesis of oxylipins

In this work, the whole aqueous extracts of soybean flour and oat flour have been used as valuable alternatives to purified oxygenase enzymes for the preparation of oxylipins derived from (5Z,8Z,11Z,14Z,17Z)-eicosapentaenoic acid (EPA). The lipoxygenase activity in the aqueous extracts of soybean (Glycine max. L.) flour was monitored with linoleic acid as substrate and compared with the commercially available purified enzyme (LOX-1). Oat flour extracts (Avena sativa L.) were evaluated for their peroxygenase activity by comparing different enzyme preparations in the epoxidation of methyl oleate. It was found that lyophilization of the aqueous extracts from these vegetable flours offers advantages in terms of enzyme stability, reproducibility and applicability to preparative organic synthesis. The lyophilized enzyme preparations were tested for the oxyfunctionalization of EPA and the formed products were isolated in satisfactory yields. In the presence of lyophilized extract from soybean, EPA gave 15S-hydroxy-(5Z,8Z,11Z,13E,17Z)-eicosapentaenoic acid in enantiopure form as exclusive product. Peroxygenase from oat flour was less selective and catalyzed the formation of different epoxides of EPA. However, the biocatalyzed epoxidation of EPA under controlled conditions allowed to obtain optically active (17R,18S)-epoxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic acid (65% ee) as the main monoepoxide, among the five possible ones.

17-OxoDHA Is a PPARα/γ Dual Covalent Modifier and Agonist

17-Hydroxy docosahexaenoic acid (17-HDHA) is an oxidized form of docosahexaenoic acid (DHA) and known as a specialized proresolving mediator. We found that a further oxidized product, 17-oxodocosahexaenoic acid (17-oxoDHA), activates peroxisome proliferator-activated receptors γ (PPARγ) and PPARα in transcriptional assays and thus can be classified as an α/γ dual agonist. ESI mass spectroscopy and X-ray crystallographic analysis showed that 17-oxoDHA binds to PPARγ and PPARα covalently, making 17-oxoDHA the first of a novel class of PPAR agonists, the PPARα/γ dual covalent agonist. Furthermore, the covalent binding sites were identified as Cys285 for PPARγ and Cys275 for PPARα.