Investigation of oxidized lipids with (patho)physiological relevance using mass spectrometric methods and their improved detection using MS imaging

• Applicant: Dr. Kathrin Engel
• Subject Area: Analytical Chemistry
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 511424302

Lipids are essential components of cellular membranes, which are present in comparatively high concentrations in all tissues. The excessive generation of radicals, i.e. reactive oxygen or nitrogen species (ROS or RNS) during inflammatory processes, can oxidatively alter particularly unsaturated phospholipids (PL). Oxidized lipids and products derived thereof play an important role during the development of cardiovascular diseases, diabetes, atherosclerosis and tumors. The detection of oxidized PL, particularly spatially resolved in tissues, is a big challenge due to the lack of suitable detection methods. Analytics of these oxidation products is difficult because of two reasons: first, some oxidation products, such as hydroperoxides are hardly detectable under conditions of the here applied MALDI-MS (matrix-assisted laser desorption and ionization mass spectrometry), because they are depleted under (UV) laser irradiation. Furthermore, some oxidation products, such as chain-shortened aldehydes react with biogenic compounds, like proteins or phosphatidylethanolamines and are not detected with their original molecular weight. Another problem is that only a few oxidized lipids are commercially available and these (transient) products need to be generated in-house. Thus, the detectability of lipid oxidation products by mass spectrometry – particularly MALDI MS – is to be investigated and improved during this project. Initially, oxidized PL are being generated from commercially available PL by different methods. By using new matrix substances and chemically modifying established ones, MALDI conditions shall be adjusted to enable the detection of all kinds of labile PL oxidation products. Next, these conditions are being transferred to biological samples (seminal plasma, blood plasma) from which it is already known that these are prone to lipid oxidation. Finally, oxidized PL are being detected on selected tissue slices (healthy and inflamed liver tissue) using imaging MS (MSI). This work will be performed in cooperation with groups from Mannheim (MSI) and Aachen (mouse liver tissue). Beside the evaluation of the native tissues, these tissues will also be spiked with defined amounts of oxidized PL in order to determine the achievable detection limits of the method. This should answer the question, which parameters need to be "fine tuned" to monitor inflammation processes by MALDI MSI and to avoid artifacts. The expected results are of high scientific and socio-economic value from the methodological as well as from the medical point of view. MSI gives specific chemical information, that allows conclusions about the progression and the prognosis of (inflammatory) diseases. Reliable information on the tissue composition (in almost real time) would help to advance tumor surgery.

• DFG Programme: Research Grants