The Neuroprotective Mechanism Of REST In Prion Diseases Models

Transmissible spongiform encephalopathies(TSEs),also known as prion diseases,are a group of infectious neurodegenerative diseases characterized by multiple neuropathological hallmarks including synaptic damage,neurofibrillary degeneration and neuronal death.The factors and mechanisms that maintain cellular morphological integrity and protect against neurodegeneration in prion diseases are still unclear.The RE 1-silencing transcription factor(REST)/neuron-restrictive silencer factor(NRSF)acts as a transcriptional regulator.REST functions as a hub and with other factors,coordinately regulates multiple aspects of neurogenesis,orchestrates neural differentiation,and preserves the unique neural phenotype.During normal ageing,REST is induced in the nucleus.The activation state of REST may distinguish neuroprotection from neurodegeneration in the ageing brain.The role and the associated molecular regulatory mechanisms of REST in prion diseases is poorly understood.Here we use PrP106-126-treated primary cortical neurons and 263K-infected hamsters as in vitro and in vivo prion diseases model,respectively.After the overexpression/knockdown of REST,examining the express and location of REST,the potential regulatory mechanism that function upstream and downstream of REST in prion diseases.(1)Here we report that after stimulation with the neurotoxic PrP106-126 fragment in primary cortical neurons,the levels of total and nucleus REST become decreased in vivo in the brain of 263K-infected hamsters and in vitro in PrP 106-126-treated primary neurons by immunofluorescence(IF)and immunoblotting(IB).(2)By IF,IB,transmission electron microscope(TME),flow cytometry(FCM),we demonstrate that REST alleviates neurotoxic prion peptide(PrP106-126)-induced synaptic damage and neurofibrillary degeneration,morphological changes of organelles,increased intracellular ROS level,decreased cell viability and neuronal cell death in primary neurons.Knockdown of REST exacerbates above neuropathological damages.(3)Overexpression of REST reduces pathological damage and abnormal biochemical alterations of neurons induced by PrP 106-126 and maintains neuronal viability by stabilizing the level of pro-survival protein FOXO1,CREB,Bcl-2 and inhibiting the permeability of the mitochondrial outer membrane,release of cytochrome c from mitochondria to cytoplasm and the activation of Capase3.Conversely,knockdown of REST exacerbates morphological damage and inhibits the expression of FOXO1.Overexpression of REST in primary cortical neurons alleviated PrP 106-126 peptide-induced neuronal oxidative stress,mitochondrial damage and partly inhibition of the LRP6-Wnt-(3-catenin and Akt-mTOR signaling.(4)Additionally,by overexpression or knockdown of LRP6,we further show that LRP6-mediated Wnt-β-catenin signaling partly regulates the expression of REST.Collectively,we demonstrate for the first time novel neuroprotective function of REST in prion diseases and hypothesize that the LRP6-Wnt-β-catenin/REST signaling plays critical and collaborative roles in neuroprotection.(5)Lithium restores nuclear expression of REST,which is essential for regulating survival proteins.lithium directly alleviates PrP106-126-induced synaptic damage and neuronal cell death by preventing changes in presynaptic and postsynaptic marker proteins and promoting survival pathways also partially via the expression of REST.Moreover,REST plays a critical role in the neuroprotective mechanisms of lithium treatment.Lithium also mics neuroprotective functions when REST is blocked,and these beneficial effects are additive with REST overexpression under physiological conditions.Knockdown of REST significantly suppresses the neuroprotective function of lithium.Conversely,overexpression of REST partially recovers its actions.Summary:REST is an essential neuroprotective regulator in prion diseases.However,the levels of total and nucleus REST become decreased in vivo and in vitro prion diseases models.LRP6-Wnt-β-catenin signaling specially regulates the expression of REST.Overexpression of LRP6 or lithium could induce the expression and nuclear translocation of REST.This signaling of neuronal survival regulation could be explored as a novel therapeutic target for prion diseases.