Neuroprotective Effects of Trilobatin, a Novel Naturally Occurring Sirt3 Agonist from <i>Lithocarpus polystachyus</i> Rehd., Mitigate Cerebral Ischemia/Reperfusion Injury: Involvement of TLR4/NF-κB and Nrf2/Keap-1 Signaling

Abstract

<b><i>Aims:</i></b> Neuroinflammation and oxidative stress are deemed the prime causes of brain injury after cerebral ischemia/reperfusion (I/R). Since the silent mating-type information regulation 2 homologue 3 (Sirt3) pathway plays an imperative role in protecting against neuroinflammation and oxidative stress, it has been verified as a target to treat ischemia stroke. Therefore, we attempted to seek novel Sirt3 agonist and explore its underlying mechanism for stroke treatment both <i>in vivo</i> and <i>in vitro</i>. <b><i>Results:</i></b> Trilobatin (TLB) not only dramatically suppressed neuroinflammation and oxidative stress injury after middle cerebral artery occlusion in rats, but also effectively mitigated oxygen and glucose deprivation/reoxygenation injury in primary cultured astrocytes. These beneficial effects, along with the reduced proinflammatory cytokines <i>via</i> suppressing Toll-like receptor 4 (TLR4) signaling pathway, lessened oxidative injury <i>via</i> activating nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways, in keeping with the findings <i>in vivo</i>. Intriguingly, the TLB-mediated neuroprotection on cerebral I/R injury was modulated by reciprocity between TLR4-mediated neuroinflammatory responses and Nrf2 antioxidant responses as evidenced by molecular docking and silencing TLR4 and Nrf2, respectively. Most importantly, TLB not only directly bonded to Sirt3 but also increased Sirt3 expression and activity, indicating that Sirt3 might be a promising therapeutic target of TLB. <b><i>Innovation:</i></b> TLB is a naturally occurring Sirt3 agonist with potent neuroprotective effects <i>via</i> regulation of TLR4/nuclear factor-kappa B and Nrf2/Kelch-like ECH-associated protein 1 (Keap-1) signaling pathways both <i>in vivo</i> and <i>in vitro</i>. <b><i>Conclusion:</i></b> Our findings indicate that TLB protects against cerebral I/R-induced neuroinflammation and oxidative injury through the regulation of neuroinflammatory and oxidative responses <i>via</i> TLR4, Nrf2, and Sirt3, suggesting that TLB might be a promising Sirt3 agonist against ischemic stroke.