Visualization of Region-Specific Lipid Alterations in the Mouse Brain in Response to Efavirenz Treatment Using MALDI Mass Spectrometry Imaging

Abstract ID 129701 Poster Board 042 Efavirenz (EFV) is a non-nucleoside reverse transcriptase inhibitor used for human immunodeficiency virus (HIV) treatment in combination with other antiretrovirals such as tenofovir and emtricitabine. Notably, EFV has been listed in the World Health Organization's list of essential medicines. However, previous clinical studies have revealed that EFV has been associated with adverse effects on the brain. Since lipids play diverse physiological roles in the brain, their alterations can result in the onset of brain disorders. Of note, it has been reported that EFV-based antiretroviral regimens impact lipid profiles in plasma. To elucidate the association between EFV-based therapy and brain disorders, it is essential to understand the impact of EFV on brain lipid profiles. Moreover, changes in the brain lipid metabolism in response to EFV treatment are currently unknown. In this study, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging was employed to generate region-specific spatial localization profiles of lipids in the mouse brain following EFV treatment. The area under the receiver operating characteristic curve was used to discriminate between the spatial localization profiles of lipids of interest in control and EFV-treated mouse brains. Additionally, mass spectrometry-based proteomics was performed to investigate changes in proteins in the mouse brain in response to the EFV treatment. Using MALDI mass spectrometry imaging we discovered distinct region-specific localizations of phosphatidylcholine (PC), sphingomyelin (SM), ceramide phosphoinositol (PI-Cer), and hexosylceramide (HexCer) in mouse brain. Specifically, PC(32:0), PC(38:5), and SM(d18:1/18:0) exhibited their accumulation in the hippocampus region while PI-Cer(38:8) showed its depletion in the same brain region in response to EFV treatment. In addition, we observed the depletion of PC(38:6), PC(40:6), and PI-Cer(40:3) in the thalamus region of the EFV-treated mice. Moreover, SM(d18:1/22:0), SM(d18:1/24:1), SM(d18:1/24:0), SM(d18:2/25:0), and SM(d18:1/25:0) exhibited high abundance, in the corpus callosum region in response to EFV treatment. In contrast, PI-Cer(38:1), PI-Cer(38:0), HexCer(t42:1), and HexCer(t42:2) exhibited their low abundance in the corpus callosum region of the EFV-treated mice as compared to control mice. From mass spectrometry-based proteomics analysis, we found the expression of lipid metabolizing enzymes, including ceramide synthase 2, acid sphingomyelinase, acid ceramidase, and calcium-independent phospholipase A2-gamma in the brain tissues. Further, the expression levels of twelve proteins were significantly decreased following EFV treatment. The above proteins include Na⁺/K⁺ transporting ATPase subunit alpha 1, tubulin beta-3 chain, neurofilament medium chain, and homer protein homolog 1. Taken together, these results provide insight into the EFV-induced alterations of lipid metabolism in the brain. This research was funded by a startup grant from the University of Maryland, Baltimore County (to H.K.S.), START (to H.K.S.), and SURFF (to H.K.S.)