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.

Proinflammatory leukotrienes (LTs) are produced by 5-lipoxygenase (5-LO) aided by 5-LO-activating protein (FLAP). LT biosynthesis inhibitors are currently under clinical investigation as treatments for respiratory and cardiovascular diseases. Here, we have revealed a sex bias in the efficiency of clinically relevant LT biosynthesis inhibitors, showing that their effects are superior in females. We found that androgens cause these sex differences by impeding the LT-biosynthetic 5-LO/FLAP complex assembly. Lower doses of the FLAP inhibitor MK886 were required to reduce LTB4 levels in exudates of female versus male mice and rats. Following platelet-activating factor-induced shock, MK886 increased survival exclusively in female mice, and this effect was abolished by testosterone administration. FLAP inhibitors and the novel-type 5-LO inhibitors licofelone and sulindac sulfide exhibited higher potencies in human blood from females, and bioactive 5-LO/FLAP complexes were formed in female, but not male, human and murine leukocytes. Supplementation of female blood or leukocytes with 5α-dihydrotestosterone abolished the observed sex differences. Our data suggest that females may benefit from anti-LT therapy to a greater extent than males, prompting consideration of sex issues in LT modifier development

5-Lipoxygenase (5-LO) catalyzes the initial steps in the biosynthesis of proinflammatory leukotrienes. Upon cell activation, 5-LO translocates to the nuclear membrane where arachidonic acid is transferred by 5-LOactivating protein (FLAP) to 5-LO for metabolism. Although previous data indicate association of 5-LO with FLAP, the in situ assembly of native 5-LO/FLAP complexes remains elusive. Here, we show time-resolved 5-LO/FLAP colocalization by immunofluorescence microscopy and in situ 5-LO/FLAP interaction by proximity ligation assay at the nuclear membrane of Ca 2+ -ionophore A23187-activated human monocytes and neutrophils in relation to 5-LO activity. Although 5-LO translocation and product formation is completed within 1.5-3 min, 5-LO/FLAP interaction is delayed and proceeds up to 30 min. Though monocytes and neutrophils contain comparable amounts of 5-LO protein, neutrophils produce 3-5 times higher levels of 5-LO products due to prolonged activity, accompanied by delayed 5-LO nuclear membrane translocation. Arachidonic acid seemingly acts as adaptor for 5-LO/FLAP assembly, whereas FLAP inhibitors (MK886, 100 nM; BAY X 1005, 3 mM) disrupt the complex. We conclude that FLAP may regulate 5-LO activity in 2 ways: first by inducing an initial flexible association for efficient 5-LO product synthesis, followed by the formation of a tight 5-LO/FLAP complex that terminates 5-LO activity.-Gerstmeier, J., Weinigel, C., Rummler, S., Rådmark, O., Werz, O., Garscha, U. Time-resolved in situ assembly of the leukotrienesynthetic 5-lipoxygenase/5-lipoxygenase-activating protein complex in blood leukocytes. FASEB J. 30, 276-285 (2016). www.fasebj.org

No abstract

The severity and course of inflammatory processes differ between women and men, but the biochemical mechanisms underlying these sex differences are elusive. Prostaglandins (PG) and leukotrienes (LT) are lipid mediators linked to inflammation. We demonstrated superior LT biosynthesis in human neutrophils and monocytes, and in mouse macrophages from females, and we confirmed these sex differences in vivo where female mice produced more LTs during zymosan-induced peritonitis versus males. Here, we report sex differences in PG production in neutrophils during acute inflammation. In the late phase (4–8 hrs) of mouse zymosan-induced peritonitis and rat carrageenan-induced pleurisy, PG levels in males were higher versus females, seemingly due to higher PG production in infiltrated neutrophils. Accordingly, human neutrophils from males produced more PGE2 than cells from females. Increased PG biosynthesis in males was accompanied by elevated cyclooxygenase (COX)-2 expression connected to increased nuclear factor-kappa B activation, and was abolished when LT synthesis was pharmacologically blocked, suggesting that elevated PG production in males might be caused by increased COX-2 expression and by shunting phenomena due to suppressed LT formation. Conclusively, our data reveal that the biosynthesis of pro-inflammatory PGs and LTs is conversely regulated by sex with consequences for the inflammatory response.