1H NMR-visible mobile lipid domains correlate with cytoplasmic lipid bodies in apoptotic T-lymphoblastoid cells |
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Authors: | Massimo Di Vito Luisa Lenti Arno Knijn Egidio Iorio Federica D’Agostino Agnese Molinari Annarica Calcabrini Annarita Stringaro Stefania Meschini Giuseppe Arancia Argante Bozzi Roberto Strom Franca Podo |
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Institution: | 1. Laboratory of Cell Biology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy;2. Department of Experimental Medicine and Pathology, University of Rome ‘La Sapienza’, 00185 Rome, Italy;3. Laboratory of Ultrastructures, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy;4. Department of Biomedical Sciences and Technologies, University of L’Aquila, 67100 L’Aquila, Italy;5. Department of Cellular Biotechnology and Hematology, University of Rome ‘La Sapienza’, 00185 Rome, Italy |
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Abstract: | The presence of nuclear magnetic resonance (NMR)-visible mobile lipid (ML) domains in apoptotic lymphoblasts suggests alterations in neutral lipid metabolism and compartmentation during programmed cell death. The detection of similar ML signals in activated lymphocytes raises questions about common mechanisms of ML formation during apoptosis and upon lymphoblast stimulation. Structure and subcellular localization of ML domains were therefore investigated by NMR, fluorescence and electron microscopy in Jurkat T-lymphoblasts either induced to apoptosis (by anthracyclines or dexamethasone or by serum deprivation) or activated by phorbol myristate acetate (PMA) plus ionomycin. ML contents in drug-treated cells correlated linearly with apoptosis, irrespective of the specific inducer and cell cycle arrest phase (r=0.993, P<0.001). Similar ML levels were measured in drug-induced apoptotic cells (A≈30–40%) and in non-apoptotic PMA/ionomycin-treated lymphoblasts (72 h). Lower ML contents were instead formed in serum-deprived apoptotic cells, with respect to controls. Increases in ML signals were associated, in either apoptotic or activated cells, with the accumulation of cytoplasmic, osmophilic lipid bodies (diameter≤1.0 μm), surrounded by own membrane, possessing intramembrane particles. The results support the hypothesis that ML are formed in the cytoplasm of drug-induced apoptotic cells during an early, ‘biochemically active’ phase of programmed cell death. |
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Keywords: | Apoptosis Lymphoblast activation Mobile lipid Anthracycline Dexamethasone BrdU bromodeoxyuridine FCS fetal calf serum FID free induction decay FFA free fatty acid IMP intramembrane particle ML mobile lipid NMR nuclear magnetic resonance PC phosphatidylcholine PCho phosphocholine plc phospholipase C PI propidium iodide PMA phorbol 12-myristate 13-acetate PUFA polyunsaturated fatty acid TCR T cell receptor TEM transmission electron microscopy TG triacylglycerol TNF tumor necrosis factor |
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