Inhibition of autophagy rescues HT22 hippocampal neurons from erastin-induced ferroptosis.

Abstract

Ferroptosis is a regulated form of cell death which is considered an oxidative iron-dependent process. The lipid hydroperoxidase glutathione peroxidase 4 prevents the iron (Fe2+)-dependent formation of toxic lipid reactive oxygen species. While emerging evidence indicates that inhibition of glutathione peroxidase 4 as a hallmark of ferroptosis in many cancer cell lines, the involvement of this biochemical pathway in neuronal death remains largely unclear. Here, we investigate, first whether the ferroptosis key players are involved in the neuronal cell death induced by erastin. The second objective was to examine whether there is a cross talk between ferroptosis and autophagy. The third main was to address neuron response to erastin, with a special focus on ferritin and nuclear receptor coactivator 4-mediated ferritinophagy. To test this in neurons, erastin (0.5-8 µM) was applied to hippocampal HT22 neurons for 16 hours. In addition, cells were cultured with the autophagy inhibitor, 3-methyladenin (10 mM) and/or ferroptosis inhibitors, ferrostatin 1 (10-20 µM) or deferoxamine (10-200 µM) before exposure to erastin. In this study, we demonstrated by immunofluorescence and western blot analysis, that erastin downregulates dramatically the expression of glutathione peroxidase 4, the sodium-independent cystine-glutamate antiporter and nuclear receptor coactivator 4. The protein levels of ferritin and mitochondrial ferritin in HT22 hippocampal neurons did not remarkably change following erastin treatment. In addition, we demonstrated that not only the ferroptosis inhibitor, ferrostatin1/deferoxamine abrogated the ferroptotic cell death induced by erastin in hippocampal HT22 neurons, but also the potent autophagy inhibitor, 3-methyladenin. We conclude that (1) erastin-induced ferroptosis in hippocampal HT22 neurons, despite reduced nuclear receptor coactivator 4 levels, (2) that either nuclear receptor coactivator 4-mediated ferritinophagy does not occur or is of secondary importance in this model, (3) that ferroptosis seems to share some features of the autophagic cell death process.