A Lipidomic Approach to Studying the Downregulation of Free Fatty Acids by Cytosolic Phospholipase A2 Inhibitors

Inhibitors of cytosolic phospholipase A₂ (GIVA cPLA₂) have received great attention, since this enzyme is involved in a number of inflammatory diseases, including cancer and auto-immune and neurodegenerative diseases. Traditionally, the effects of GIVA cPLA₂ inhibitors in cells have been studied by determining the inhibition of arachidonic acid release. However, although to a lesser extent, GIVA cPLA₂ may also hydrolyze glycerophospholipids, releasing other free fatty acids (FFAs), such as linoleic acid or oleic acid. In the present work, we applied a liquid chromatography-high-resolution mass spectrometry method to study the levels of intracellular FFAs, after treating cells with selected GIVA cPLA₂ inhibitors. Six inhibitors belonging to different chemical classes were studied, using SH-SY5Y neuroblastoma cells as a model. This lipidomic approach revealed that treatment with each inhibitor created a distinct intracellular FFA profile, suggesting not only inhibitory potency against GIVA cPLA₂, but also other parameters affecting the outcome. Potent inhibitors were found to reduce not only arachidonic acid, but also other long-chain FAs, such as adrenic or linoleic acid, even medium-chain FAs, such as caproic or caprylic acid, suggesting that GIVA cPLA₂ inhibitors may affect FA metabolic pathways in general. The downregulation of intracellular FFAs may have implications in reprogramming FA metabolism in neurodegenerative diseases and cancer.