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Photodynamic oxidation of Escherichia coli membrane phospholipids: new insights based on lipidomics
Author(s) -
Alves Eliana,
Santos Nuno,
Melo Tânia,
Maciel Elisabete,
Dória M. Luísa,
Faustino Maria A. F.,
Tomé João P. C.,
Neves Maria G. P. M. S.,
Cavaleiro José A. S.,
Cunha Ângela,
Helguero Luisa A.,
Domingues Pedro,
Almeida Adelaide,
Domingues M. Rosário M.
Publication year - 2013
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6739
Subject(s) - chemistry , lipidomics , phospholipid , escherichia coli , liposome , lipid oxidation , chromatography , porphyrin , biochemistry , electrospray ionization , lipid peroxidation , membrane , mass spectrometry , antioxidant , gene
RATIONALE The irreversible oxidation of biological molecules, such as lipids, can be achieved with a photosensitizing agent and subsequent exposure to light, in the presence of molecular oxygen. Although lipid peroxidation is an important toxicity mechanism in bacteria, the alterations caused by the photodynamic therapy on bacterial phospholipids are still unknown. In this work, we studied the photodynamic oxidation of Escherichia coli membrane phospholipids using a lipidomic approach. METHODS E. coli ATCC 25922 were irradiated for 90 min with white light (4 mW cm –2 , 21.6 J cm –2 ) in the presence of a tricationic porphyrin [(5,10,15‐tris(1‐methylpyridinium‐4‐yl)‐20‐(pentafluorophenyl)porphyrin triiodide, Tri‐Py + ‐Me‐PF]. Lipids were extracted and separated by thin‐layer chromatography. Phospholipid classes were quantified by phosphorus assay and analyzed by electrospray ionization tandem mass spectrometry. Fatty acids were analyzed by gas chromatography. Quantification of lipid hydroperoxides was performed by FOX2 assay. Analysis of the photodynamic oxidation of a phospholipid standard was also performed. RESULTS Our approach allowed us to see that the photodynamic treatment induced the formation of a high amount of lipid hydroperoxides in the E. coli lipid extract. Quantification of fatty acids revealed a decrease in the unsaturated C16:1 and C18:1 species suggesting that oxidative modifications were responsible for their variation. It was also observed that photosensitization induced the oxidation of phosphatidylethanolamines with C16:1, C18:1 and C18:2 fatty acyl chains, with formation of hydroxy and hydroperoxy derivatives. CONCLUSIONS Membrane phospholipids of E. coli are molecular targets of the photodynamic effect induced by Tri‐Py + ‐Me‐PF. The overall change in the relative amount of unsaturated fatty acids and the formation of PE hydroxides and hydroperoxides evidence the damages in bacterial phospholipids caused by this lethal treatment. Copyright © 2013 John Wiley & Sons, Ltd.