title: Natural forms of vitamin E and 13'-carboxychromanol, a long-chain vitamin E metabolite, inhibit leukotriene generation from stimulated neutrophils by blocking calcium influx and suppressing 5-lipoxygenase activity, respectively.
abstract: Leukotrienes generated by 5-lipoxygenase (5-LOX)-catalyzed reaction are key regulators of inflammation. In ionophore-stimulated (A23187; 1-2.5 μM) human blood neutrophils or differentiated HL-60 cells, vitamin E forms differentially inhibited leukotriene B(4) (LTB(4)) with an IC(50) of 5-20 μM for γ-tocopherol, δ-tocopherol (δT), and γ-tocotrienol, but a much higher IC(50) for α-tocopherol. 13'-Carboxychromanol, a long-chain metabolite of δT, suppressed neutrophil- and HL-60 cell-generated LTB(4) with an IC(50) of 4-7 μM and potently inhibited human recombinant 5-LOX activity with an IC(50) of 0.5-1 μM. In contrast, vitamin E forms had no effect on human 5-LOX activity but impaired ionophore-induced intracellular calcium increase and calcium influx as well as the subsequent signaling including ERK1/2 phosphorylation and 5-LOX translocation from cytosol to the nucleus, a key event for 5-LOX activation. Further investigation showed that δT suppressed cytosolic Ca(2+) increase and/or LTB(4) formation triggered by ionophores, sphingosine 1-phosphate, and lysophosphatidic acid but not by fMLP or thapsigargin, whereas 13'-carboxychromanol decreased cellular production of LTB(4) regardless of different stimuli, consistent with its strong inhibition of the 5-LOX activity. These observations suggest that δT does not likely affect fMLP receptor-mediated signaling or store depletion-induced calcium entry. Instead, we found that δT prevented ionophore-caused cytoplasmic membrane disruption, which may account for its blocking of calcium influx. These activities by vitamin E forms and long-chain carboxychromanol provide potential molecular bases for the differential anti-inflammatory effects of vitamin E forms in vivo.
authors.affiliation: Department of Foods and Nutrition, Interdepartmental Nutrition Program, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Ziying
authors.initials: Z
authors.lastname: Jiang
authors.forename: Xinmin
authors.initials: X
authors.lastname: Yin
authors.forename: Qing
authors.initials: Q
authors.lastname: Jiang
mesh_terms: D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002384:Catalysis / Q000187:drug effects; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002839:Chromans / Q000378:metabolism / Q000494:pharmacology*; D002999:Clone Cells; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology; D018922:HL-60 Cells; D006801:Humans; D020024:Leukotriene Antagonists / Q000378:metabolism / Q000494:pharmacology*; D007975:Leukotriene B4 / Q000037:antagonists & inhibitors / Q000097:blood; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D018375:Neutrophil Activation / Q000187:drug effects* / Q000276:immunology; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D014810:Vitamin E / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D002839:Chromans; D020024:Leukotriene Antagonists; D016859:Lipoxygenase Inhibitors; D014810:Vitamin E; D007975:Leukotriene B4; D000001:Calcimycin; D002118:Calcium