Systemic vitamin E metabolites have been proposed as signaling molecules, but their physiological role is unknown. Here we show, by library screening of potential human vitamin E metabolites, that long-chain ω-carboxylates are potent allosteric inhibitors of 5-lipoxygenase, a key enzyme in the biosynthesis of chemoattractant and vasoactive leukotrienes. 13-((2R)-6-hydroxy-2,5,7,8-tetramethylchroman-2-yl)-2,6,10-trimethyltridecanoic acid (α-T-13′-COOH) can be synthesized from α-tocopherol in a human liver-on-chip, and is detected in human and mouse plasma at concentrations (8–49 nM) that inhibit 5-lipoxygenase in human leukocytes. α-T-13′-COOH accumulates in immune cells and inflamed murine exudates, selectively inhibits the biosynthesis of 5-lipoxygenase-derived lipid mediators in vitro and in vivo, and efficiently suppresses inflammation and bronchial hyper-reactivity in mouse models of peritonitis and asthma. Together, our data suggest that the immune regulatory and anti-inflammatory functions of α-tocopherol depend on its endogenous metabolite α-T-13′-COOH, potentially through inhibiting 5-lipoxygenase in immune cells.

Whether chemists or biologists, researchers dealing with metabolomics require tools to decipher complex mixtures. As a part of metabolomics and initially dedicated to identifying bioactive natural products, dereplication aims at reducing the usual timeconsuming process of known compounds isolation. Mass spectrometry and nuclear magnetic resonance are the most commonly reported analytical tools during dereplication analysis. Though it has low sensitivity, 13 C NMR has many advantages for such a study. Notably, it is nonspecific allowing simultaneous high-resolution analysis of any organic compounds including stereoisomers. Since NMR spectrometers nowadays provide useful data sets in a reasonable time frame, we have embarked upon writing software dedicated to 13 C NMR dereplication. The present study describes the development of a freely distributed algorithm, namely MixONat and its ability to help researchers decipher complex mixtures. Based on Python 3.5, MixONat analyses a { 1 H}-13 C NMR spectrum optionally combined with DEPT-135 and 90 datato distinguish carbon types (i.e., CH 3 , CH 2 , CH, and C)as well as a MW filtering. The software requires predicted or experimental carbon chemical shifts (δc) databases and displays results that can be refined based on user interactions. As a proof of concept, this 13

The paradigm that GPCRs are able to prolong or initiate cellular signalling through intracellular receptors recently emerged. Melatonin binds to G protein-coupled MT 1 and MT 2 receptors. In contrast to most other hormones targeting GPCRs, melatonin and its synthetic analogues are amphiphilic molecules easily penetrating into cells, but the existence of intracellular receptors is still unclear mainly due to a lack of appropriate tools. EXPERIMENTAL APPROACHWe therefore designed and synthesized a series of hydrophilic melatonin receptor ligands coupled to the Cy3 cyanin fluorophore to reliably monitor its inability to penetrate cells. Two compounds, one lipophilic and one hydrophilic, were then functionally characterized in terms of their affinity for human and murine melatonin receptors expressed in HEK293 cells and their signalling efficacy. KEY RESULTSAmong the different ligands, ICOA-13 showed the desired properties as it was cell-impermeant and bound to human and mouse MT 1 and MT 2 receptors. ICOA-13 showed differential activities on melatonin receptors ranging from partial to full agonistic properties for the G i /cAMP and ERK pathway and β-arrestin 2 recruitment. Notably, ICOA-13 enabled us to discriminate between G i /cAMP signalling of the MT 1 receptor initiated at the cell surface and neuronal mitochondria. CONCLUSIONS AND IMPLICATIONSWe report here the first cell-impermeant melatonin receptor agonist, ICOA-13, which allows us to discriminate between signalling events initiated at the cell surface and intracellular compartments. Detection of mitochondrial MT 1 receptors may have an important impact on the development of novel melatonin receptor ligands relevant for neurodegenerative diseases, such as Huntington disease.