Activating Sigma1R by fluoxetine suppresses neuronal ferroptosis in epilepsy by inhibiting MDM2-mediated GPX4 ubiquitination

INTRODUCTION: Epilepsy affects more than 70 million individuals worldwide, contributing to early mortality, disability, and cognitive impairment. Antidepressants have been explored for epilepsy treatment, although their effects and underlying mechanisms remain unclear. Ferroptosis has been implicated in numerous neurological disorders, including epilepsy, but the regulatory mechanisms behind neuronal damage caused by epilepsy remain unclear. OBJECTIVES: This study aimed to investigate the effect of fluoxetine (FLX) on epilepsy and the underlying mechanisms. METHODS: We established a mouse model of epilepsy induced by kainic acid (KA) to evaluate the effects of the antidepressant FLX on seizure activity in mice, as well as its impact on neural damage and cognitive function. We also clarified the effects of FLX on epilepsy-related neuronal ferroptosis in both the epilepsy mouse model and the glutamate-induced cell death model. The key E3 ligases, key signaling pathways and receptors by which FLX regulates the ubiquitination of GPX4, a crucial ferroptosis regulator, were further investigated. Additionally, we characterized the lysine residue sites and polyubiquitination patterns that participate in the ubiquitination of GPX4. RESULTS: This study demonstrates that FLX provides neuroprotective and cognitive benefits in murine epilepsy models by inhibiting neuronal ferroptosis. FLX stabilizes glutathione peroxidase 4 (GPX4), a ferroptosis regulator, by preventing its ubiquitination and proteasomal degradation. The antiferroptotic effect of FLX is mediated by the Sigma-1 receptor (Sigma1R), as its inhibition reverses the protective effects of FLX on epilepsy and GPX4 stability. In neurons, the FLX/Sigma1R axis suppresses the JNK/p38 MAPK-mediated upregulation of MDM2, an E3 ubiquitin ligase, thereby disrupting MDM2-induced K48-linked polyubiquitination of GPX4 at Lys162 and Lys167. This enhances GPX4 stability and increases antioxidant defenses. CONCLUSIONS: These findings reveal a novel molecular pathway (Sigma1R-JNK/p38 MAPK-MDM2-GPX4 axis) through which FLX inhibits ferroptosis, highlighting its therapeutic potential for epilepsy and other ferroptosis-related neurological disorders.