Mitochondrial Redox Opto-Lipidomics Reveals Mono-Oxygenated\nCardiolipins as Pro-Apoptotic Death Signals

While opto-genetics has proven to\nhave tremendous value in revealing the functions of the macromolecular\nmachinery in cells, it is not amenable to exploration of small molecules\nsuch as phospholipids (PLs). Here, we describe a redox opto-lipidomics\napproach based on a combination of high affinity light-sensitive ligands\nto specific PLs in mitochondria with LC-MS based redox lipidomics/bioinformatics\nanalysis for the characterization of pro-apoptotic lipid signals.\nWe identified the formation of mono-oxygenated derivatives of C18:2-containing\ncardiolipins (CLs) in mitochondria after the exposure of 10-nonylacridine\norange bromide (NAO)-loaded cells to light. We ascertained that these\nsignals emerge as an immediate opto-lipidomics response, but they\ndecay long before the commencement of apoptotic cell death. We found\nthat a protonophoric uncoupler caused depolarization of mitochondria\nand prevented the mitochondrial accumulation of NAO, inhibited the\nformation of C18:2-CL oxidation product,s and protected cells from\ndeath. Redox opto-lipidomics extends the power of opto-biologic protocols\nto studies of small PL molecules resilient to opto-genetic manipulations.