Ferroptosis is an iron-dependent cell death pathway that involves depletion of intracellular glutathione (GSH) levels and iron-mediated lipid peroxidation. Ferroptosis is experimentally caused by inhibition of the cystine/glutamate antiporter xCT, which depletes cells of GSH, or by inhibition of Glutathione peroxidase 4 (GPx4), a key regulator of lipid peroxidation. The events that occur between GPx4 inhibition and the execution of ferroptotic cell death are currently a matter of active research. Previous work has shown that calcium release from the endoplasmic reticulum (ER) mediated by ryanodine receptor (RyR) channels contributes to ferroptosis-induced cell death in primary hippocampal neurons. Here, we used SH-SY5Y neuroblastoma cells, which do not express RyR channels, to test if calcium release mediated by the inositol 1,4,5-trisphosphate receptor (IP3R) channel plays a role in this process. We show that inhibition of GPx4 by RAS Selective Lethal Compound 3 (RSL3) generated an increase in reactive oxygen species (ROS), increased cytoplasmic and mitochondrial calcium levels, increased lipid peroxidation and caused cell death. The RSL3-induced calcium signals were inhibited by Xestospongin B, an inhibitor of the ER-resident IP3R calcium channel, by decreasing IP3R levels with carbachol and by IP3R1 knock-down. The intracellular calcium chelator BAPTA-AM inhibited RSL3-induced calcium signals, which were not affected by extracellular calcium depletion. We propose that GPx4 inhibition activates IP3R-mediated calcium release in SH-SY5Y cells, leading to increased cytoplasmic and mitochondrial calcium levels, which in turn stimulate the production of ROS and induce lipid peroxidation and ferroptotic cell death in a noxious positive feedback cycle.
Biology and Life Sciences, Neuroscience and Neurology
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