Investigating changes in myelin lipid composition during relapsing-remitting neuroinflammation - The pathological hallmarks of multiple sclerosis (MS) include lesions in the white and gray matter of the central nervous system (CNS) comprised of areas of immune cell infiltration, reactive astrogliosis, axonal transection, and demyelination. Proteins of the myelin sheath, such as myelin basic protein (MBP) and myelin oligodendrocyte protein (MOG) have been extensively studied in MS pathogenesis; surprisingly, very little is known about the changes to lipids components of the myelin sheath during the disease process, in particular as it relates to changes in the composition of key myelin lipids during relapses, remission, and progression of MS. Modifications in myelin lipids composition during disease relapses may critically affect the progression of MS, for example by providing targets for lipid peroxidation. This may provide druggable lipid-based targets, which have previously not been explored. There is an urgent unmet need in this area. Evidence in MS patients supports that increased lipid peroxidation occurs in the CNS. Moreover, it was shown that combined treatment with glatiramer acetate (GA) and the potent antioxidant N-acetylcysteine (NAC) decreased MS relapses as compared with GA treatment alone. Studying myelin lipids in the CNS is technically challenging and therefore, we have developed a novel approach using matrix-assisted laser-desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry imaging (MSI) for analysis of myelin lipids in situ. MALDI-TOF MSI is a label-free, two- dimensional molecular imaging technique with < 20 µm spatial resolution capable of visualizing the molecular spatial distribution, colocalization, and relative abundance of hundreds of targeted and untargeted analytes and providing a molecular biological snapshot of the metabolic state of tissues. In support of the premise of this proposal we have obtained exciting preliminary data revealing changes to myelin lipids in situ in the CNS of mice with experimental autoimmune encephalomyelitis (EAE). Our results provide novel insights into the CNS lipidome during neuroinflammation. We will leverage our preliminary results and the unique combined expertise of our team in neuroinflammation and MSI to test the hypothesis that the composition of myelin lipids does not return to baseline during remission in relapsing-remitting EAE (RR-EAE) models of MS, and that the residual changes in lipid composition play key roles in disease progression, for example via lipid peroxidation. We will test our hypothesis by: (1) determining the effects of neuroinflammation on the composition and spatial distribution of key CNS myelin lipids during relapses, remission, and progression of EAE; (2) determine the key neuroinflammatory mechanisms driving changes in myelin lipid composition. Our proposal will fill a significant gap in knowledge and address critical questions that will help develop better treatments for progressive MS.
