Polyoxygenated Cholesterol Ester Hydroperoxide Activates TLR4 and SYK Dependent Signaling in Macrophages

• Published in: PloS one Vol. 8; no. 12; p. e83145
• Main Authors: Choi, Soo-Ho, Yin, Huiyong, Ravandi, Amir, Armando, Aaron, Dumlao, Darren, Kim, Jungsu, Almazan, Felicidad, Taylor, Angela M., McNamara, Coleen A., Tsimikas, Sotirios, Dennis, Edward A., Witztum, Joseph L., Miller, Yury I.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 23.12.2013; Public Library of Science (PLoS)
• Subjects: Accumulation; Animals; Apolipoproteins; Arteriosclerosis; Atherosclerosis; Biochemistry; Biological activity; Biological Transport; Blood lipids; Blood plasma; Bone growth; Bone marrow; c-Jun protein; Cell Line; Cell spreading; Cholesterol; Cholesterol - analogs & derivatives; Cholesterol - chemistry; Cholesterol - isolation & purification; Cholesterol - pharmacology; Cholesterol, LDL - metabolism; Chromatography; Development and progression; Dextran; Dextrans; Dimerization; Esters; Foams; Food safety; Gene Expression Regulation; Health sciences; Human subjects; Humans; Inflammation; Inflammation - genetics; Inflammation - metabolism; Inflammation - pathology; Intracellular; Intracellular Signaling Peptides and Proteins - deficiency; Intracellular Signaling Peptides and Proteins - genetics; JNK Mitogen-Activated Protein Kinases - genetics; JNK Mitogen-Activated Protein Kinases - metabolism; Laboratories; Lesions; Lipoproteins, LDL - chemistry; Liquid chromatography; Low density lipoprotein; Low density lipoprotein receptors; Low density lipoproteins; Lymphocyte Antigen 96 - genetics; Lymphocyte Antigen 96 - metabolism; Macrophages; Macrophages - drug effects; Macrophages - metabolism; Macrophages - pathology; MAP Kinase Kinase 4 - genetics; MAP Kinase Kinase 4 - metabolism; Mass spectrometry; Mass spectroscopy; Medicine; Mice; Mice, Knockout; Mitogen-Activated Protein Kinase 1 - genetics; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - genetics; Mitogen-Activated Protein Kinase 3 - metabolism; Oxidation; Oxidation-Reduction; Pharmacology; Phosphorylation; Plaque, Atherosclerotic - genetics; Plaque, Atherosclerotic - metabolism; Plaque, Atherosclerotic - pathology; Primary Cell Culture; Protein Multimerization; Protein-Tyrosine Kinases - deficiency; Protein-Tyrosine Kinases - genetics; Review boards; Rodents; Signal Transduction; Signaling; Studies; Syk Kinase; Syk protein; TLR4 protein; Toll-Like Receptor 4 - deficiency; Toll-Like Receptor 4 - genetics; Toll-like receptors; Transcription factors; Veins & arteries; La Jolla California; California; United States > US; Virginia; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0083145

Oxidation of low-density lipoprotein (LDL) is one of the major causative mechanisms in the development of atherosclerosis. In previous studies, we showed that minimally oxidized LDL (mmLDL) induced inflammatory responses in macrophages, macropinocytosis and intracellular lipid accumulation and that oxidized cholesterol esters (OxCEs) were biologically active components of mmLDL. Here we identified a specific OxCE molecule responsible for the biological activity of mmLDL and characterized signaling pathways in macrophages in response to this OxCE. Using liquid chromatography - tandem mass spectrometry and biological assays, we identified an oxidized cholesteryl arachidonate with bicyclic endoperoxide and hydroperoxide groups (BEP-CE) as a specific OxCE that activates macrophages in a TLR4/MD-2-dependent manner. BEP-CE induced TLR4/MD-2 binding and TLR4 dimerization, phosphorylation of SYK, ERK1/2, JNK and c-Jun, cell spreading and uptake of dextran and native LDL by macrophages. The enhanced macropinocytosis resulted in intracellular lipid accumulation and macrophage foam cell formation. Bone marrow-derived macrophages isolated from TLR4 and SYK knockout mice did not respond to BEP-CE. The presence of BEP-CE was demonstrated in human plasma and in the human plaque material captured in distal protection devices during percutaneous intervention. Our results suggest that BEP-CE is an endogenous ligand that activates the TLR4/SYK signaling pathway. Because BEP-CE is present in human plasma and human atherosclerotic lesions, BEP-CE-induced and TLR4/SYK-mediated macrophage responses may contribute to chronic inflammation in human atherosclerosis.