NP-11 Keap1-Nrf2 Inhibitor NXPZ Ameliorated Aβ1-42-Induced Cognitive Dysfunction in Mice

Objective:Nuclear factor erythroid 2-related factor 2(Nrf2)is a member of the cap‘n’collar(CNC)subfamily of transcription factors and contains a basic leucine zipper domain.It is found to be ubiquitiously expressed in many tissues,and works as the key regulator against oxidative stress damage in cells and organs,which makes Nrf2 a widely concerned drug target.Recent research has identified that Nrf2 is involved in the pathology of Alzheimer’s disease(AD),whereas the mechanism is unknown.The purpose of this study is to figure out the role of Nrf2 in the pathologic process of AD through Nrf2-Keap1-ARE pathway and the effects of Keap1-Nrf2 inhibitor on cognitive dysfunction in mice models.Methods:Amyloidβ1-42(Aβ1-42)was injected into the bilateral hippocampus to induce the cognitive dysfunction in eightweek old male mice.Then mice were treated with Keap1-Nrf2 inhibitor NXPZ of three doses and donepezil as a positive control by intragastric administration one time a day.After one week of treatment,several behavior tests were run to identify the learning and memory ability of the AD mice.We used histopathological examination to show the cell and tissue structure changes in the hippocampus.Additionally,we detected Nrf2 and Aβin the plasma in mice with ELISA kits,as well as some factors related to oxidative stress in the hippocampus and cortex.The expression levels of Nrf2,Keap1,Tau and p-Tau were measured in the murine brain tissue with Western blot.SH-SY5Y cells were studied as an in vitro model to further clarify the mechanism.Results:The treatment of NXPZ ameliorated learning and memory dysfunction in AD mice in a dose-dependent manner,and the high dose group recovered better than the positive drug group.Hematoxylineosin staining showed that the cell number and morphology of the hippocampus were all restored in different degrees and the number of pyramidal cells increased with no obvious swelling and complete structure and the cells arranged neatly,indicating that compound NXPZ could improve the damaged hippocampal structure.The plasma Nrf2 level was increased in a dosedependent manner in the treatment groups;however,the plasma Aβwas decrease after NXPZ treatment.What’s more,superoxide dismutase(SOD)and glutathione reductase(GSSH)in the hippocampus and cortex was increased in the treatment group,while the malondialdehyde(MDA)was decreased,meaning that NXPZ treatment promoted expression of the anti-oxidative factors and inhibited the expression of the oxidative factors in the down-stream.Western blot analysis of hippocampus and cortex showed up-regulated Nrf2,decreased Keap1 and decreased p-Tau in NXPZ treatment mice.In ex vivo experiments,when SH-SY5Y cells were treated with Aβ,Nrf2 in the cytoplasm was increased,as well as the expression Nrf2 in the nuclear was decreased.The treatment of NXPZ increased nuclear Nrf2,decreased cytoplasm Nrf2,and decreased the expression of p-Tau.Conclusion:The present study demonstrates that Nrf2 has an important role in neuron function.Nrf2 activation by selective Keap1-Nrf2 inhibitor NXPZ may contribute to improve cognitive function in AD mice.The mechanism may be related to increased generation and release of Nrf2 induced by more disaggregation with Keap1,leading to more expression of anti-oxidative molecules to protect the damage caused by Aβ.These results indicates that Nrf2 may be a novel therapeutic target of AD and Nrf2 agonist may be a novel medication for protecting the loss of learning and memory ability.