Keap1-nuclear factor rythroid 2-related factor 2 inhibitor NXPZ ameliorates Aβ1-42-induced cognitive dysfunction in mice

摘要

OBJECTIVE Nuclear factor erythroid 2-related factor 2(Nrf2) 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 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 in AD mice models.METHODS Amyloid β^(1-42)(Aβ^(1-42))was injected into the bilateral hippocampus to induce the cognitive dysfunction in eight-week old male mice.The mice were treated with Keap1-Nrf2 inhibitor NXPZ of three doses as well as donepezil as a positive control by intragastric administration one time a day for one week.Several behavior tests were used to analyze the mice learning and memory ability.Additionally,we detected Nrf2 and Aβ in 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 blotting.SH-SY5 Y 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.The plasma Nrf2 level was increased in a dose-dependent manner in the treatment groups;however,the plasma Aβ was decreased.What′ s more,superoxide dismutase(SOD) and glutathione reductase(GSSH) in the hippocampus and cortex were 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 blotting 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-SY5 Y 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 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 Keap1-Nrf2 inhibitor may be a novel medication for protecting the loss of learning and memory ability.