Labelfree mapping and profiling of altered lipid homeostasis in the rat hippocampus after traumatic stress: Role of oxidative homeostasis

Oxidative and lipid homeostasis are altered by stress and trauma and post-traumatic stress disorder (PTSD) is associated with alterations to lipid species in plasma. Stress-induced alterations to lipid and oxidative homeostasis may exacerbate PTSD pathology, but few preclinical investigations of stress-induced lipidomic changes in the brain exist. Currently available techniques for the quantification of lipid species in biological samples require tissue extraction and are limited in their ability to retrieve spatial information. Raman imaging can overcome this limitation through the quantification of lipid species in situ in minimally processed tissue slices. Here, we utilized a predator exposure and psychosocial stress (PE/PSS) model of traumatic stress to standardize Raman imaging of lipid species in the hippocampus using LC-MS based lipidomics and these data were confirmed with qRT-PCR measures of mRNA expression of relevant enzymes and transporters. Electron Paramagnetic Resonance Spectroscopy (EPR) was used to measure free radical production and an MDA assay to measure oxidized polyunsaturated fatty acids. We observed that PE/PSS is associated with increased cholesterol, altered lipid concentrations, increased free radical production and reduced oxidized polyunsaturated fats (PUFAs) in the hippocampus (HPC), indicating shifts in lipid and oxidative homeostasis in the HPC after traumatic stress.