HOCl-induced lysophospholipid generation from diacyl- and alkenyl-acyl-phospholipids

• Applicant: Dr. Beate Fuchs
• Subject Area: Analytical Chemistry
• Term: from 2009 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 112537167

Inflammatory processes play extraordinarily important roles in many diseases. On the molecular level inflammatory processes are characterized by the invasion of typical inflammatory cells (such as neutrophilic granulocytes) from the blood stream into the inflamed tissue. These cells generate (beside other compounds) reactive oxygen species (ROS), for instance, HOCl. As biological samples contain always major amounts of phospholipids (PLs), their ROS-induced oxidation products possess unequivocally physiological relevance. The addition of HOCl to the unsaturated fatty acyl residues of phosphatidylcholine (PC) leads in several steps to the generation of lysophosphatidylcholine (LPC). Lysophospholipids (LPLs), particularly LPCs, are increasingly discussed as potential disease biomarkers. As PLs of different species are widely identical, LPLs would represent (in contrast to proteins) a universal biomarker. In the last funding period the influence of the positions of the double bonds with either cis or trans configuration on the reaction of PLs with HOCl were investigated and particularly the yield of LPC determined. One major aspect was also the oxidation behavior of alkenyl-PLs (plasmalogens), as these compounds are very sensitive to oxidation. A significant influence of the position of the double bond is evident. Remarkably, the trans isomers are less sensitive to oxidation than the cis-isomers. Another important result was that hydroxyl radicals (generated by the Fenton reaction) do also result in chlorohydrin generation if the reaction is performed in the presence of physiological salt concentration. The reasons for these effects are to be further investigated in more detail by modern MS and NMR methods, whereby the in vivo relevance of the identified products will be another important aspect. Beside the products of free fatty acid oxidation, the so far unavailable phospholipids are to be synthesized (by a chemoenzymatic approach) and their oxidation products have to be identified. In addition to these simplified model experiments chemical reactions of PLs will also be studied at a higher complexity level. On the one hand, the reactions between lipid oxidation products (e.g. aldehydes generated by the cleavage of the double bond) and other abundant molecules (e.g. proteins) must be studied. On the other hand, LPLs are generated in the organism not only by oxidation but as well under the influence of the enzyme phospholipase A2 (PLA2). Therefore, it must be investigated if oxidized PLs are cleaved to the same extent by PLA2 (as the non-oxidized PLs) or if the enzyme is (partially) inhibited by the presence of oxidized functional groups. Finally, it will be proven whether the in vitro detected oxidation products are also detectable in tissue slices, i.e. within a highly complex biological matrix. These investigations will be carried out by MALDI-MS-Imaging in cooperation with the University of Münster.

• DFG Programme: Research Grants
• Cooperation Partners: Professor Dr. Klaus Dreisewerd; Professor Dr. Thomas Weiß