Endogenous Derivatives of Linoleic Acid and their Stable Analogs Are Potential Pain Mediators.

Psoriasis is characterized by intense pruritus, with a subset of individuals with psoriasis experiencing thermal hypersensitivity. However, the pathophysiology of thermal hypersensitivity in psoriasis and other skin conditions remains enigmatic. Linoleic acid is an omega-6 fatty acid that is concentrated in the skin, and oxidation of linoleic acid into metabolites with multiple hydroxyl and epoxide functional groups has been shown to play a role in skin barrier function. Previously, we identified several linoleic acid‒derived mediators that were more concentrated in psoriatic lesions, but the role of these lipids in psoriasis remains unknown. In this study, we report that two such compounds-9,10-epoxy-13-hydroxy-octadecenoate and 9,10,13-trihydroxy-octadecenoate-are present as free fatty acids and induce nociceptive behavior in mice but not in rats. By chemically stabilizing 9,10-epoxy-13-hydroxy-octadecenoate and 9,10,13-trihydroxy-octadecenoate through the addition of methyl groups, we observed pain and hypersensitization in mice. The nociceptive responses suggest an involvement of the TRPA1 channel, whereas hypersensitive responses induced by these mediators may require both TRPA1 and TRPV1 channels. Furthermore, we showed that 9,10,13-trihydroxy-octadecenoate‒induced calcium transients in sensory neurons are mediated through the Gßγ subunit of an unidentified G-protein coupled receptor (GPCR). Overall, mechanistic insights from this study will guide the development of potential therapeutic targets for the treatment of pain and hypersensitivity.

Stable analogs of 13­hydroxy-9,10-trans-epoxy-(11E)-octadecenoate (13,9-HEL), an oxidized derivative of linoleic acid implicated in the epidermal skin barrier.

Hydroxy-epoxy- and trihydroxy derivatives of linoleic acid are proposed to play an essential function in formation of the mammalian skin permeability barrier, which could account for the essential nature of its precursor, linoleic acid. Recent literature suggests that a specific oxidized enone derivative of LA esterified in ceramides facilitates binding to proteins, potentially serving a structural role in formation of the epidermal skin barrier. However, it is still to be established if other linoleic acid derivatives are also required for skin barrier formation, and whether the essential role is performed exclusively by an esterified, structural lipid or as an unesterified, labile signaling lipid, or by some combination of these derivatives. Progress in this domain is limited by lack of availability of hydroxy­epoxy-and trihydroxy- and octadecenoate derivatives of linoleic acid and related compounds, and challenges in maintaining them in the unesterified lipid pool. Here we describe methods for the total synthesis of hydroxy­epoxy-octadecenoate derivatives of linoleic acid (HEL1), and stable analogs that are designed to be resistant to inactivation by: (a) acylation/esterification (thus trapping these lipids in the free acid pool), (b) dehydrogenation, and (c) analogs combining both modifications. We further provide a total synthesis of corresponding hydroxy­epoxy- derivatives of sebaleic acid (a regioisomer of linoleic acid present in skin), and of small molecule scaffolds containing the allylic and non-allylic epoxide 7-carbon substructures shared by both families of hydroxy­epoxy-and trihydroxy- octadecenoates. Finally, we demonstrate that 2,2-dimethyl analogs of hydroxy­epoxy-and trihydroxy- octadecenoates are resistant to esterification with an in vitro assay and thus provide a novel template for stabilizing labile, bioactive lipids as free acids by preventing acylation/esterification.

A sixteen-week three-armed, randomized, controlled trial investigating clinical and biochemical effects of targeted alterations in dietary linoleic acid and n-3 EPA+DHA in adults with episodic migraine: Study protocol.

Migraine is a prevalent neurological disorder, affecting over 16% of adult women and 7% of adult men in the U.S., causing significant pain, disability, and medical expense, with incomplete benefits from conventional medical management. Migraine, as a chronic pain syndrome, provides a practical model for investigating the impact of dietary modifications in omega-3 (n-3) and omega-6 (n-6) fatty acids. This paper reports the protocol of a trial to assess whether targeted dietary modifications designed to increase n-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), with or without concurrent reduction in n-6 linoleic acid (LA), will alter nociceptive lipid mediators and mediate decreases in frequency and severity of migraine. This prospective, randomized, controlled trial in 153 male and female adult subjects, ages 18-99, with diagnosed and actively managed episodic migraine tests the efficacy, safety, and biochemical effects of targeted, controlled alterations in dietary omega-3 and omega-6 fatty acids. Participants are masked to diet hypotheses and all assessors are masked to treatment assignment. Following a four-week baseline period, participants with migraine headache frequency of 5-20 per month are randomized to one of three intensive dietary regimens for 16 additional weeks followed by a less intensive observation period. Dietary intervention arms include: 1) increased n-3 EPA+DHA with low n-6 linoleic acid (H3 L6); 2) increased n-3 EPA+DHA with usual US dietary intake of n-6 linoleic acid (H3 H6); and 3) usual US dietary content of n-3 and n-6 fatty acids (L3 H6). During the actual intervention, subjects receive content-specific study oils and foods sufficient for two meals and two snacks per day, as well as dietary counseling. Biochemical and clinical outcome measures are performed at intervals throughout this period. This randomized controlled trial is designed to determine whether targeted alterations in dietary n-3 and n-6 fatty acids can alter nociceptive lipid mediators in a manner that decreases headache pain and enhances quality of life and function in adults with frequent migraines. TRIAL REGISTRATION: NCT02012790.

Synthesis of ß-substituted tryptamines by regioselective ring opening of aziridines.

Functionalized tryptamines are targets of interest for development as small molecule therapeutics. The ring opening of aziridines with indoles is a powerful method for tryptamine synthesis if site selectivity can be controlled. 4-Nitrobenzyl carbamate (PNZ)-protected aziridines undergo regioselective ring opening to produce ß-substituted tryptamines for a series of indoles. The PNZ-protected tryptamines can be further manipulated by PNZ removal under mild conditions.