CircPRKCI-miR-545/589-E2F7 axis dysregulation mediates hydrogen peroxide-induced neuronal cell injury

Excessive oxidative stress induces significant injury and cytotoxicity to neuronal cells. The current study tested expression and the potential function of the circular RNA PRKCI (circPRKCI) in oxidative stress-injured neuronal cells. In cultured SH-SY5Y neuronal cells, hydrogen peroxide (H₂O₂) downregulated circPRKCI expression, causing accumulation of miR-545 and miR-589, but reduction of their target, the transcription factor E2F7. Importantly, ectopic overexpression of circPRKCI in SH-SY5Y cells significantly attenuated H₂O₂-induced cytotoxicity. Conversely, siRNA-mediated knockdown of circPRKCI induced SH-SY5Y cell death and apoptosis. Further studies demonstrated that H₂O₂-induced cytotoxicity in SH-SY5Y cells was inhibited by miR-545/589 inhibitors, but mimicked by miR-545/589 mimics. Importantly, CRISPR/Cas9-mediated knockout (KO) of E2F7 induced potent SH-SY5Y cell death and apoptosis. Furthermore, transfection of circPRKCI siRNA or miR-545/589 mimics were ineffective in E2F7 KO cells. In the primary human neurons, H₂O₂ stimulation similarly induced circPRKCI downregulation, miR-545/589 accumulation and E2F7 reduction. Moreover, H₂O₂-induced death and apoptosis in the primary neurons were significantly inhibited by circPRKCI overexpression or miR-545/589 inhibitors. Taken together, our results show that dysregulation of circPRKCI-miR-545/589-E2F7 axis mediated H₂O₂-induced neuronal cell injury. Targeting this novel cascade could be a fine strategy to protect neurons from oxidative stress.