Neuroprotective Effect of Swertiamain on Cerebral Ischemia/Reperfusion Injury by Inducing the Nrf2 Protective Pathway

Oxidative stress plays a vital role in the development of cerebral ischemic/reperfusion (I/R). Targeting oxidative stress is proposed to be an effective strategy to treat cerebral I/R injury. Gentiana macrophylla Pall is reported to have a potential protective effect against stroke. Swertiamarin (Swe), an active secoiridoid glycoside compound isolated from Gentiana macrophylla Pall, has been reported to possess antioxidative potential. This study is to explore whether Swe could prevent brain from I/R injury, and the related mechanisms of oxidative stress are also elucidated using mice middle cerebral artery occlusion (MCAO) model and primary hippocampal neurons oxygen-glucose deprivation/reperfusion (OGD/R) model. Swe (25, 100, or 400 mg/kg) was pretreated intraperitoneally for 7 days until establishment of the MCAO model, while hippocampal neurons were maintained in Swe (0.1, 1, or 10 mu M) in the entire process of reoxygenation. The results indicated that Swe pretreatment markedly decreased infarct volume, apoptotic neurons, and oxidative damage and promoted neurologic recovery in vivo. It also decreased reactive oxygen species (ROS) and increased cell viability in vitro. Western blot analyses and immunofluorescence staining demonstrated that Swe pretreatment promoted Nrf2 nuclear translocation from Keapl-Nrf2 complex and enhanced the expressions of NAD(P)H: quinone oxidoreductase-1 (NQO1) and heme oxygenase-1 (HO-1) both in vivo and in vitro, while the expressions could be reversed by a Nrf2 inhibitor. The binding mode of Keapl with Swe was also proposed by covalent molecular docking. Collectively, Swe could be considered as a promising protective agent against cerebral I/R injury through suppressing oxidative stress by activation of the Nrf2 protective pathway.