title: Vitamin E γ-Tocotrienol Inhibits Cytokine-Stimulated NF-κB Activation by Induction of Anti-Inflammatory A20 via Stress Adaptive Response Due to Modulation of Sphingolipids.
abstract: NF-κB plays a central role in pathogenesis of inflammation and cancer. Many phytochemicals, including γ-tocotrienol (γTE), a natural form of vitamin E, have been shown to inhibit NF-κB activation, but the underlying mechanism has not been identified. In this study, we show that γTE inhibited cytokine-triggered activation of NF-κB and its upstream regulator TGF-β-activated kinase-1 in murine RAW 264.7 macrophages and primary bone marrow-derived macrophages. In these cells, γTE induced upregulation of A20, an inhibitor of NF-κB. Knockout of A20 partially diminished γTE's anti-NF-κB effect, but γTE increased another NF-κB inhibitor, Cezanne, in A20(-/-) cells. In search of the reason for A20 upregulation, we found that γTE treatment increased phosphorylation of translation initiation factor 2, IκBα, and JNK, indicating induction of endoplasmic reticulum stress. Liquid chromatography-tandem mass spectrometry analyses revealed that γTE modulated sphingolipids, including enhancement of intracellular dihydroceramides, sphingoid bases in de novo synthesis of the sphingolipid pathway. Chemical inhibition of de novo sphingolipid synthesis partially reversed γTE's induction of A20 and the anti-NF-κB effect. The importance of dihydroceramide increase is further supported by the observation that C8-dihydroceramide mimicked γTE in upregulating A20, enhancing endoplasmic reticulum stress, and attenuating TNF-triggered NF-κB activation. Our study identifies a novel anti-NF-κB mechanism where A20 is induced by stress-induced adaptive response as a result of modulation of sphingolipids, and it demonstrates an immunomodulatory role of dihydrocermides.
authors.affiliation: Department of Nutrition Science, Purdue University, West Lafayette, IN 47907; and.
authors.forename: Yun
authors.identifier: http://orcid.org/0000-0002-4346-0096
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Nutrition Science, Purdue University, West Lafayette, IN 47907; and.
authors.forename: Na-Young
authors.initials: NY
authors.lastname: Park
authors.affiliation: Department of Nutrition Science, Purdue University, West Lafayette, IN 47907; and.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Jang
authors.affiliation: Department of Medicine, University of California at San Francisco, San Francisco, CA 94143.
authors.forename: Averil
authors.initials: A
authors.lastname: Ma
authors.affiliation: Department of Nutrition Science, Purdue University, West Lafayette, IN 47907; and qjiang@purdue.edu.
authors.forename: Qing
authors.initials: Q
authors.lastname: Jiang
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000276:immunology; D010450:Endopeptidases / Q000235:genetics / Q000276:immunology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D005786:Gene Expression Regulation; D020672:I-kappa B Proteins / Q000235:genetics / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins / Q000819:agonists* / Q000235:genetics / Q000276:immunology; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000276:immunology; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000276:immunology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology; D061251:Primary Cell Culture; D015398:Signal Transduction; D013107:Sphingolipids / Q000276:immunology* / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects / Q000276:immunology; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D024504:gamma-Tocopherol / Q000494:pharmacology*; D000099151:MAP Kinase Kinase Kinase 7; D000072017:Deubiquitinating Enzymes
chemical_list: D003546:Cysteine Endopeptidases; D010450:Endopeptidases; D020672:I-kappa B Proteins; D047908:Intracellular Signaling Peptides and Proteins; D048670:MAP Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D013107:Sphingolipids; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D024504:gamma-Tocopherol; D000099151:MAP Kinase Kinase Kinase 7; C000606205:Nfkbia protein, mouse; C578787:Otud7b protein, mouse; D000072017:Deubiquitinating Enzymes; C513261:Tnfaip3 protein, mouse