Jianmei Gao

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Background and Purpose: Astrocytic nuclear factor erythroid-derived 2-related factor 2 (Nrf2) is a potential therapeutic target of ischemic preconditioning (IPC). Icariside Ⅱ (ICS Ⅱ) is a naturally occurring flavonoid derived from Herba Epimedii with Nrf2 induction potency. This study was designed to clarify whether ICS Ⅱ simulates IPC neuroprotection and to decipher if the astrocytic-Nrf2 is contributed to ICS Ⅱ preconditioning against ischemic stroke. Experimental Approach: Mice with transient middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia and oxygen-glucose deprivation (OGD)-injured primary astrocytes were used to explore the neuroprotective of ICS Ⅱ preconditioning. Additionally, Nrf2-deficient mice were pretreated with ICS Ⅱ to determine whether ICS Ⅱ exerts its neuroprotection by activating Nrf2. Key results: ICS Ⅱ pre-treatment dramatically mitigated the cerebral injury in ischemic stroke mice along with restoring long-term recovery. Furthermore, proteomics screening identified Nrf2 is a crucial gene evoked by ICS Ⅱ stimulation and is required for the anti-oxidative effect and anti-inflammatory effect of ICS Ⅱ. Most interestingly, ICS Ⅱ directly bound with Nrf2 and reinforced the transcriptional activity of Nrf2 after MCAO. Moreover, ICS Ⅱ pre-treatment exerted cytoprotective effect on astrocytes after lethal oxygen-glucose deprivation insult via promoting Nrf2 nuclear translocation and mediating OXPHOS/NF-κB/ferroptosis axis. While, abrogated neuroprotection in Nrf2-deficient mice and astrocyte potently supports Nrf2-dependent neuroprotection of ICS Ⅱ. Conclusions and implications: ICS Ⅱ preconditioning confers robust neuroprotection against ischemic stroke via astrocytic Nrf2-mediated OXPHOS/NF-κB/ferroptosis axis, it is concluded that ICS Ⅱ will be serve as a promising Nrf2 activator to rescue ischemic stroke.