Treatment with efavirenz (EFV), an antiretroviral drug widely used to treat HIV, leads to region-specific alterations in various lipids in the mouse brain, according to a recent study. The findings shed light on the neurotoxic effects associated with the drug.
To understand the molecular basis of these effects, researchers employed matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) to visualize lipid distribution in brain tissue. They coupled this approach with tandem mass spectrometry (MS/MS) and bottom-up proteomics to explore changes in lipid metabolism and protein expression in specific brain regions.
The study found that certain phosphatidylcholine species (PCs) increased in the hippocampus while being depleted in the thalamus, highlighting region-specific dysregulation. Additionally, proteomic analysis showed a downregulation of enzymes in the sphingomyelin-ceramide pathway, a potential link to neurotoxicity.
“Lipids are important biomolecules that play crucial roles in brain function, and their metabolism involves several proteins. However, our understanding of the role of lipid metabolism in drug responses are incomplete,” explain co-authors Herana Kamal Seneviratne and Nav Raj Phulara from the University of Maryland, Baltimore County (UMBC). "The brain contains lipid-rich regions which prompted us to investigate the impact of efavirenz on brain lipids."
Though previous studies have reported changes in lipid localizations during disease conditions, such as neurodegeneration, the changes of lipid metabolic proteins have not been integrated, according to the authors. To address this gap, the team aimed to investigate not only lipid localization but also the broader impact of efavirenz on brain lipid metabolism. "That’s where untargeted proteomics becomes invaluable," Seneviratne and Phulara explain.
They also highlight the novelty of their approach: "To our knowledge, this is a novel approach to study drug disposition and response. A few months ago, we published our perspectives in the Journal of Mass Spectrometry, which underscores the value of combining multiple omics approaches, such as mass spectrometry imaging and proteomics, to investigate complex biological processes, including drug disposition and response.”
One of the key challenges the team faced was the complexity of the MSI and proteomics processes, compounded by the brain’s highly heterogeneous nature. And that’s why, they say, “Sample preparation and method optimizations are crucial in mass spectrometry experiments.” He added that integrating the massive amounts of data was also challenging – in a good way: “Integration of tissue imaging data and proteomics data was an exciting task for us.”
Looking ahead, the research points to new approaches to drug development. “This kind of research definitely has significant implications, particularly in improving drug efficacy and safety profiles. Alterations in lipid homeostasis are associated with various neurological disorders. Understanding these lipid alterations provides mechanistic insights into how drugs affect the brain at a molecular level,” conclude Seneviratne and Phulara.
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