Excess lipids effect on mitochondrial function in inflammatory cells

ALVAREZ, MARIA SOLEDAD; POLO, LUIS MARIANO; CASTRO, CLAUDIA

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2022

Mitochondrial–nuclear signalling plays a crucial role in cellular homeostasis, and the disruption of the interplay between mitochondria and nucleus contributes to ageing, age-related disease, and chronic inflammatory diseases. We reported that cholesterol mediates the mitochondria-to-nucleus retrocommunication as ROS and Ca2+ do. Under stress, the enrichment in the number of contact zones between the nucleus and mitochondria results in an increased amount of cholesterol transported by TSPO (the Translocator protein), stabilising NFkB and its pro-survival response and so allowing the evasion of cell death and mitophagy. On the contrary, TSPO deficiency significantly decreased the mitochondrial membrane potential, mitochondrial oxidative phosphorylation (OXPHOS) and ATP production. TSPO is widely used as a biomarker of inflammation in the nervous system based on its marked upregulation in activated microglia. Moreover, TSPO deficient microglia cells are less prone to be stimulated by LPS or IL4.Later, we evaluate how intracellular fatty acid accumulation affects mitochondrial functioning andmitochondria-to-nucleus retro-communication. Fatty acids (FA) are essential regulators ofmitochondrial structure and function because they are structural components in mitochondriamembrane phospholipids, oxidative substrates (beta-oxidation), inhibitors of pyruvate dehydrogenase, and ligands for nuclear receptors that regulate the expression of mitochondrial proteins. They also upregulate the expression of genes involved in mitochondrial fatty acid metabolism. Lipid accumulation results from an increased de novo synthesis, an increased lipid uptake, or lipolysis regulation. We use an in vitro cellular model for RAW 264.7 cells, which emulated foam cells. Since free fatty acids are toxic, their concentration was optimised to reduce their toxicity. We tested oleic acid (w-9 monounsaturated) at different combinations and timing. In addition, we evaluated cellular and ROS biology changes at different fatty acid treatments. Finally, we followed the changes in morphology using flow cytometry on Scatter and Fluorescent signals, oil red absorbance at 492 nm, protein expression by western blot and gene expression for mitophagy precursors.