Abstract Background and Purpose: Activation of Nrf2 holds great promise for treating major depressive disorder (MDD). Trilobatin (TLB) is a naturally occurring food additive conferring robust neuroprotection with Nrf2 activation potency. This study was designed to explore whether TLB is able to overcome MDD, and the role of Nrf2 in the antidepressant effect of TLB. Experimental Approach: Mice and primary hippocampal astrocytes challenged with lipopolysaccharide (LPS) were used to decipher the effects of TLB on MDD. Nrf2-deficient mice were treated with TLB and fecal microbiota transplantation (FMT) to validate the potential targets of ICS Ⅱ on ALI. Key results: TLB ameliorated depressive-like behavior in LPS-induced MDD mouse model. Single-cell RNA sequencing analysis of the hippocampus revealed that astrocytes exhibited distinct MDD-related clustering with increased Nrf2 in the antidepressant effect of TLB. TLB directly bound to Nrf2 and increased Nrf2-antioxidant response element (ARE) binding activity, which ultimately restored mitochondrial function, reduced oxidative stress and neuroinflammation. TLB improved intestinal microbiota dysbiosis and attenuated intestinal barrier through increasing expressions of the tight junction proteins. Fecal microbiota transplantation from TLB-treated mice also ameliorated depression-like behavior after LPS insult. Furthermore, by using genetically modified Nrf2-knockout mice, we validated that the antidepressant effect of TLB were Nrf2/ARE signaling dependent, suppressing astrocytes activation and gut microbiota dysbiosis. These favorable effects of TLB were abrogated in Nrf2 deficiency mice. Conclusions and implications: Our results reveal a new-found pharmacological property of TLB: serves as a novel and naturally-occurring Nrf2 activator to conquer MDD through modulating microbiota-gut-brain axis.

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.