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.

Abstract Background and Purpose: G-protein-coupled receptor (GPR158), an orphan receptor, is highly expressed in the medial prefrontal cortex in (mPFC) and identified as a novel therapeutic target for treating depression. Trilobatin (TLB) is a naturally-occurring food additive with potent neuroprotective properties. However, its pharmacological effects and molecular mechanisms against depression remains unknown. We explored whether TLB alleviates depression by targeting GPR158. Experimental Approach: Chronic unpredictable mild stress (CUMS)-induced depression mice model was used to explore antidepressant-like effect of TLB. GPR158-deficent mice were treated with TLB to determine whether TLB exerts its antidepressant-like effect by targeting GPR158. Key Results: TLB effectively alleviated CUMS-induced depressive-like behavior in mice. Mitophagy was contributed to the antidepressant-like effect of TLB, as evidenced by qRT-PCR array. As anticipated, TLB up-regulated autophagy associated protein expression of PFC in mice and restored mitochondrial dynamic balance, further inhibiting oxidative stress, as reflected by reducing ROS generation and increasing antioxidant enzymes. Mechanistically, GPR158 deficiency also up-regulated autophagy associated proteins expression and rejuvenated mitochondrial dynamic, further attenuating depressive-like behavior in response to CUMS insult. Most importantly, TLB directly bound to GPR158 and decreased its protein expression. Encouragingly, the promotive effect of TLB on mitophagy and its antidepressant-like effect were enhanced in GPR158-deficent mice. Conclusions and Implications: Our findings not only highlight GPR158-mediated mitophagy as a crucial pharmacological target for managing depression, but also reveal a new-found pharmacological property of TLB: serving as a novel naturally-occurring ligand of GPR158 to safeguard depression from oxidative stress by promoting mitophagy.

Background and Purpose:: Peroxisome proliferator-activated receptor α and-γ (PPARα/γ) are known to play crucial roles in acute liver injury (ALI). Icariside Ⅱ (ICS Ⅱ), a natural flavonoid compound derived from Herba Epimedii, confers neuroprotection with PPARα/γ induction potency. This study was aimed to explore whether ICS Ⅱ has the capacity to protect against ALI, and if so what are the role of PPARα/γ in the beneficial effect of ICS Ⅱ on ALI. Experimental Approach: Mice challenged by D-galactosamine (GalN)/lipopolysaccharide (LPS) and Kupffer cells (KCs) upon LPS insult were used as ALI models in vivo and in vitro. PPARα/γ-deficient mice and Sirt6-deficient mice were treated with ICS Ⅱ to validate the potential targets of ICS Ⅱ on ALI. Key results: ICS Ⅱ dose-dependently improved the survival rate and liver histology, decreased ALT and AST in D-galactosamine (GalN)/lipopolysaccharide (LPS)-treated mice. Furthermore, ICS Ⅱ directly bound to PPARα/γ and increased their activities. The protective properties of ICS Ⅱ were counteracted when PPARα/γ were knocked out in GalN/LPS-induced mice and LPS-induced KCs, respectively. Mechanistically, ICS Ⅱ restored mitochondrial function, reduced oxidative stress and inflammation through activating PPARα/γ, which interacted with Sirt6 and inhibited NF-κB nuclear translocation. Intriguingly, ICS Ⅱ-evoked hepatoprotective effect and activation of PPARα/γ were largely blunted in Sirt6-deficient mice. Conclusions and implications: Our findings not only highlight PPARα/γ-SIRT6 signaling as a vital therapeutic target to combat ALI, but also reveal ICS Ⅱ may serve as a novel dual PPARα/γ agonist to safeguard ALI from the oxidation-inflammation vicious circle by coactivating SIRT6.

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.