High‐resolution lipidomics coupled with rapid fixation reveals novel ischemia‐induced signaling in the rat neurolipidome

• Published in: Journal of neurochemistry 2017-03, Vol.140 (5), p.766-775
• Main Authors: Trépanier, Marc‐Olivier, Eiden, Michael, Morin‐Rivron, Delphine, Bazinet, Richard P., Masoodi, Mojgan
• Format: Article
• Language: English
• Subjects: Animals; bioactive lipids; Brain; Brain Ischemia - metabolism; Brain Ischemia - physiopathology; Ceramides - metabolism; Diglycerides; Diglycerides - metabolism; Energy measurement; Fatty acids; Fatty Acids - metabolism; Fixation; Head; Inflammation - chemically induced; Inflammation - physiopathology; Ischemia; Lipid Metabolism; lipidomics; Lipids; Lipopolysaccharides - pharmacology; Liquid chromatography; Male; Mass spectrometry; Mass spectroscopy; Mathematical models; microwave fixation; Microwaves; Neurochemistry; Neurons - metabolism; Phospholipids; Phospholipids - metabolism; Rats; Rats, Long-Evans; Rodents; Scientific imaging; Signal Transduction; Signaling; Spectroscopy; Statistical models
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/jnc.13934

The field of lipidomics has evolved vastly since its creation 15 years ago. Advancements in mass spectrometry have allowed for the identification of hundreds of intact lipids and lipid mediators. However, because of the release of fatty acids from the phospholipid membrane in the brain caused by ischemia, identifying the neurolipidome has been challenging. Microwave fixation has been shown to reduce the ischemia‐induced release of several lipid mediators. Therefore, this study aimed to develop a method combining high‐resolution tandem mass spectrometry (MS/MS), high‐energy head‐focused microwave fixation and statistical modeling, allowing for the measurement of intact lipids and lipid mediators in order to eliminate the ischemia‐induced release of fatty acids and identify the rat neurolipidome. In this study, we demonstrated the ischemia‐induced production of bioactive lipid mediators, and the reduction in variability using microwave fixation in combination with liquid chromatography (LC)–MS/MS. We have also illustrated for the first time that microwave fixation eliminates the alterations in intact lipid species following ischemia. While many phospholipid species were unchanged by ischemia, other intact lipid classes, such as diacylglycerol, were lower in concentration following microwave fixation compared to ischemia. The field of lipidomics has evolved vastly since its creation 15 years ago, identifying many new lipid mediators. However, in the brain, ischemia releases fatty acids from the phospholipid membrane through the activation of phospholipase A2 (PLA2). Microwave fixation has been shown to reduce the ischemia‐induced release of several lipid mediators. In this study, we highlight the usefulness of using microwave fixation, which reduced the CO2 asphyxiation‐induced production of DHA mediators such as PD1 and HDoHE and ARA mediators such as HETE, PG, and TXB.