Flow cytometric determination of ferroptosis using a rat monoclonal antibody raised against ferroptotic cells

Ferroptosis, a type of iron-dependent necrotic cell death, is specifically associated with increased lipid peroxidation. The dysfunction of the glutathione (GSH) production via the starvation of cysteine or the inhibition of phospholipid hydroperoxide glutathione peroxidase (GPX4) typically results in the accumulation of lipid peroxidation products and, consequently, the development of ferroptosis. We recently reported on the production of a rat monoclonal antibody, referred to as FerAb, against mouse-derived Hepa 1-6 cells that had been cultivated in cystine-deprived medium. Immunocytological analyses by means of fluorescence microscopy revealed that FerAb binds to fixed ferroptotic cells regardless of the species from which they were obtained, but not to apoptotic cells. We report herein on an in-depth characterization of the reactivity of FerAb with respect to unfixed cells by means of flow cytometry. The binding of FerAb to the cells was stimulated by incubating the cells in cystine deprived culture medium or treatment with RSL3, a GPX4 inhibitor, while treatment with staurosporine, an apoptosis inducer, had no effect on its binding to the cells. Supplementation with ferrostatin-1, a ferroptosis inhibitor, effectively suppressed the binding of FerAb to cells that had been cultivated in cystine-deprived medium or treated with RSL3, further confirming the specific binding of FerAb to ferroptotic cells. Thus, FerAb combined with a flow cytometry can be used to distinguish ferroptotic cells from living cells or apoptotic cells without the need for fixation. Applications of this combined technique will enable the quantitative evaluation of ferroptotic cells under a variety of patho-physiological conditions and will contribute to our understanding of the roles of ferroptosis in the body as well as cultured cells.