Notoginsenoside R1 alleviates cerebral ischemia/reperfusion injury by inhibiting the TLR4/MyD88/NF-κB signaling pathway through microbiota-gut-brain axis

Ischemic stroke (IS) ranks as the second common cause of death worldwide. However, a narrow thrombolysis timeframe and ischemia-reperfusion (I/R) injury limits patient recovery. Moreover, anticoagulation and antithrombotic drugs do not meet the clinical requirements. Studies have demonstrated close communication between the brain and gut microbiota in IS. Notoginsenoside R1 (NG-R1), a significant component of the total saponins from Panax notoginseng, has been demonstrated to be effective against cerebral I/R injury. Total saponins have been used to treat IS in Chinese pharmacopoeia. Furthermore, previous research has indicated that the absorption of NG-R1 was controlled by gut microbiota. This study aimed to access the impact of NG-R1 treatment on neuroinflammation and investigate the microbiota-related mechanisms. NG-R1 significantly reduced neuronal death and neuroinflammation in middle cerebral artery occlusion/reperfusion (MCAO/R) models. 16S rRNA sequencing revealed that NG-R1 treatment displayed the reversal of microbiota related with MCAO/R models. Additionally, NG-R1 administration attenuates intestinal inflammation, gut barrier destruction, and systemic inflammation. Furthermore, microbiota transplantation from NG-R1 exhibited a similar effect in the MCAO/R models. In summary, NG-R1 treatment resulted in the restoration of the structure of the blood-brain barrier (BBB) and reduction in neuroinflammation via suppressing the stimulation of astrocytes and microglia in the cerebral ischemic area. Mechanistic research demonstrated that NG-R1 treatment suppressed the toll-like receptor 4/myeloid differentiation primary response 88/nuclear factor kappa B (TLR4/MyD88/NF-κB) signaling pathway in both the ischemic brain and colon. NG-R1 treatment enhanced microbiota dysbiosis by inhibiting the TLR4 signaling pathway to protect MCAO/R models. These findings elucidate the mechanisms by which NG-R1 improve stroke outcomes and provide some basis for Panax notoginseng saponins in clinical treatment.