SOX9 Knockdown-Mediated FOXO3 Downregulation Confers Neuroprotection Against Ischemic Brain Injury

BACKGROUND: Evidence exists uncovering that SRY-box transcription factor 9 (SOX9) plays a role in ischemic brain injury (IBI). Thus, the current study was conducted to elucidate the specific role of SOX9 and the mechanism by which SOX9 influenced IBI. METHODS: The IBI-associated regulatory factors were searched by bioinformatics analysis. The rat model of IBI was generated using middle cerebral artery occlusion (MCAO) treatment. Neuronal cells were exposed to oxygen-glucose deprivation (OGD). The expressions of SOX9, forkhead box O3 (FOXO3), transcription of Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2), and IκB kinase α (IKKα) in OGD-treated neuronal cells were characterized using reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay. The interaction among CITED2, IKKα, and FOXO3 was identified by chromatin immunoprecipitation (ChIP) and dual luciferase reporter gene assays. Gain- and loss-of-function experiments were performed to verify the relationship among SOX9, FOXO3, CITED2, and IKKα and to investigate their functional effects on apoptosis and the inflammatory response of OGD-treated neuronal cells as well as neurological deficit and infarct area of the rat brain. RESULTS: SOX9, FOXO3, CITED2, and IKKα were highly expressed in OGD-treated neuronal cells. Silencing of SOX9 inhibited OGD-induced neuronal apoptosis and inflammatory response and reduced the neurological deficit and infarct area of the brain in the rats, which were caused by MCAO but were reversed by overexpressing FOXO3, CITED2, or IKKα. CONCLUSION: Taken together, our study suggested that upregulation of SOX9 promoted IBI though upregulation of the FOXO3/CITED2/IKKα axis, highlighting a basic therapeutic consideration for IBI treatment.