Gamma-tocotrienol attenuates the aberrant lipid mediator production in NLRP3 inflammasome-stimulated macrophages

The activation of NLRP3 inflammasome in innate immune cells is associated with enhanced production of pro-inflammatory lipid mediator eicosanoids that play a crucial role in propagating inflammation. Gamma-tocotrienol (gamma T3) is an unsaturated vitamin E that has been demonstrated to attenuate NLRP3-inflammasome. However, the role of gamma T3 in regulating eicosanoid formation is unknown. We hypothesized that gamma T3 abolishes the eicosanoid production by modulating the macrophage lipidome. LPS-primed bone marrow-derived macrophages (BMDM) were stimulated with saturated fatty acids (SFA) along with gamma T3, and the effects of gamma T3 in modulating macrophage lipidome were quantified by using mass spectrometry based-shotgun lipidomic approaches. The SFA-mediated inflammasome activation induced robust changes in lipid species of glycerolipids (GL), glycerophospholipids (GPL), and sphingolipids in BMDM, which were distinctly different in the gamma T3-treated BMDM. The gamma T3 treatment caused substantial decreases of lysophospholipids (LysoPL), diacylglycerol (DAG), and free arachidonic acid (AA, C20:4), indicating that gamma T3 limits the availability of AA, the precursor for eicosanoids. This was confirmed by the pulse-chase experiment using [H-3]-AA, and by diminished prostaglandin E-2 (PGE(2)) secretion by ELISA. Concurrently, gamma T3 inhibited LPS-induced cyclooxygenases 2 (COX2) induction, further suppressing prostaglandin synthesis. In addition, gamma T3 attenuated ceramide synthesis by transcriptional downregulation of key enzymes for de novo synthesis. The altered lipid metabolism during inflammation is linked to reduced ATP production, which was partly rescued by gamma T3. Taken together, our work revealed that gamma T3 induces distinct modification of the macrophage lipidome to reduce AA release and corresponding lipid mediator synthesis, leading to attenuated cellular lipotoxicity. (C) 2018 Elsevier Inc. All rights reserved.