Ginsenoside Rg1 protects against ischemia reperfusion-induced neurotoxicity through miR-144/Nrf2/ARE pathway

OBJECTIVE Ginsenoside Rg1(Rg1),a purified compound from Panax ginseng,has been well documented to be effective against ischemia/reperfusion(I/R) neurotoxicity.However,the underlying mechanism is stil obscure.METHODS The anti-I/R effect of Rg1 were investigated in vitro and in vivo,and the dynamics of nuclear accumulation and the transcriptional activity of NF-E2-related factor 2(Nrf2) determined by Western blotting and Dual Luciferase Reporter Assay,respectively.Nrf2 siRNA was employed to investigate Nrf2′s role in the protective effect of Rg1 against I/R.Furthermore,the role of miR-144,which could regulate post-translational Nrf2 levels,was investigated in the anti-I/R effect of Rg1 by injection of AAV-hypoxia-inducible factor miR-144-shRNA in the predicted ischemic penumbra.RESULTS It was found that the anti-I/R effect of Rg1 was related to its anti-oxidative capacity,which is mainly regulated by the Nrf2/antioxidant response element(ARE) pathway.Further study suggested that Rg1 contributes to the enhancement of the Nrf2/ARE pathway,as manifested by increasing the dynamic peak content of Nrf2,which prolonged the maintenance stage,and promoting the expression of ARE-target genes after oxygen glucose deprivation/reperfusion(OGD/R) in PC12 cells.Nrf2-siRNA application significantly reduced these changes.Furthermore,the enhancement of the Nrf2/ARE pathway by Rg1 was independent of disassociation from Keap1;rather it was a result of posttranslational regulations.It was found that Rg1 significantly reduced the expression of miR-144,which down-regulates Nrf2 production by targeting its 3′-untranslated region,after OGD/R.Knockdown of Nrf2 showed no effect on the expression of miR-144,indicating that miR-144 is an upstream regulator of Nrf2.Moreover,direct binding between Nrf2 and miR-144 in the PC12 cells was identified.Application of anti-miR-144 significantly reduced Rg1′s anti-OGD/R capacity.Final y,the role of miR-144 in Rg1′ s anti-I/R effect was tested by inhibiting miR-144 in the predicted ischemic penumbra when hypoxia-inducible-factor was activated.The results showed that loss of miR-144 abolished the anti-I/R effect of Rg1,which included reduced infarct volume,improved neurological scores,attenuated oxidative impairment,as well as activation of the Nrf2/ARE pathway.CONCLUSION Oxidative stress after I/R is alleviated by Rg1 through inhibition of miR-144 activity and subsequent promotion of the Nrf2/ARE pathway at the post-translational level.