Activation of SSAT1/ALOX15 Axis Aggravates Cerebral Ischemia/Reperfusion Injury via Triggering Neuronal Ferroptosis

Ferroptosis, an iron-dependent form of non-apoptotic cell death, is reportedly responsible for cerebral ischemia/reperfusion (I/R) injury. Evidence has shown that spermidine/spermine N1-acetyltransferase 1 (SSAT1) activation-induced ferroptosis is associated with upregulation of arachidonate 15-Lipoxygenase (ALOX15). Our previous study has revealed that upregulation of ALOX15 contributes to cerebral I/R injury via inducing microglial activation. The current study aimed to investigate the role of SSAT1/ALOX15 axis in neuronal ferroptosis after I/R. We found that the expression of SSAT1 was upregulated in the cortical penumbra of mice subjected to transient middle cerebral artery occlusion and reperfusion (tMCAO/R). Knockdown of SSAT1 mitigated I/R-induced cerebral infarction and neurological impairments, as well as decreased cortical iron contents, reactive oxygen species (ROS) generation and 4-Hydroxynonenal (4-HNE) level. Further in vitro evidence revealed that knockdown of SSAT1 downregulated the expression of ALOX15 in the primary cortical neurons exposed to tertbutyl-hydroksyperoxide (TBH). In addition, loss of neuronal viability and production of lipid hydroperoxides were inhibited in TBH-treated neurons when SSAT1 was knocked down. Mechanistically, SSAT1 overexpression decreased the expression levels of two key ferroptotic repressors, glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11) in TBH-stimulated neurons. Treatment with the ALOX15 inhibitor PD146176 or ferroptosis inhibitor ferrostatin-1 partially reversed SSAT1 upregulation-induced ferroptosis and viability loss in TBH-treated neurons. These results together indicate that the activation of SSAT1/ALOX15 axis may aggravate cerebral I/R injury via triggering neuronal ferroptosis, providing novel insights into cerebral injury associated with lipid peroxidation.