Assessment of mitochondrial lipid peroxidation in cells and zebrafish using a targeted mass spectrometry probe

Mitochondrial lipid peroxidation is a major component of oxidative damage and is also thought to contribute to ferroptosis. Lipid peroxidation is generally assessed from the accumulation of oxidized end products, such as 4-hydroxynonenal (HNE). However, these report on damage throughout the cell and are affected by changes in how oxidized phospholipids are turned over. To overcome these constraints, we developed MitoLiPOX, a mitochondria-targeted mass spectrometry probe. Mitochondria targeting and detection sensitivity were achieved by incorporating a lipophilic triphenylphosphonium cation. Responsiveness to lipid peroxidation was brought about by building in a bis-allylic carbon-hydrogen bond mimic that, upon oxidation and processing, generated a single product, MitoLiPOX-OH. LC-MS/MS quantification of MitoLiPOX-OH followed by normalization to the amount of MitoLiPOX present enabled ratiometric quantification of mitochondrial lipid peroxidation. We then used MitoLiPOX to assess mitochondrial lipid peroxidation during ferroptosis in vitro and in zebrafish in vivo.