Nrf2 Activation Rescues Dendritic Pathology in hPSC‐Derived And Primary Neuron Based Models of Parkinson's Disease
Authors: Drolet Jennifer , Czaniecki Christopher , Ryan Tammy , Stykel Morgan , Coackley Carla , Ryan Scott 
Published: June 2021

IntroductionNeuronal loss in Parkinson's disease (PD) is associated with impaired proteostasis and increased oxidative stress in dopaminergic neurons of the substantia nigra pars compacta. In a healthy cell, redox imbalance is controlled by enzymes that detoxify the cell of free radicals. These enzymes are transcriptionally activated as part of the cells antioxidant response. The master regulator of this pathway is a transcription factor called Nrf2 (a.k.a NFE2L2). Aggregated α‐synuclein (α‐syn) is the major constituent of Lewy Bodies (the disease hallmark), however the mechanisms linking α‐syn aggregation with generation of reactive oxygen species (ROS) have been difficult to ascertain. We therefore asked whether a deficit in the antioxidant response might explain the increased susceptibility of PD neurons to ROS generation and dendritic pathology following α‐syn aggregation.MethodsTo study these events, we contrasted human pluripotent stem cells (hPSCs) that harbor the α‐syn‐A53T mutation against isogenic controls. A9‐type dopaminergic neurons (the specific neurons lost in PD) were generated from hPSCs by following a floor plate differentiation paradigm. α‐syn‐A53T neurons show accumulation of insoluble α‐syn consistent with an early disease phenotype. We similarly contrasted rat primary neurons against neurons exposed to α‐syn pre‐formed fibrils (PFF). PFF exposed neurons accumulate large intracellular aggregates of α‐syn consistent with advanced synucleinopathy. We show that aberrant accumulation of α‐syn in both systems promotes increased ROS production coupled to increased dendritic pathology and decreased dendritic length and complexity.ResultsTo evaluate the role of Nrf2 in dendritic pathology we measured Nrf2 protein stability and phospho‐activation in A53T‐mutant and PFF exposed neurons. We found that α‐syn accumulation impaired Nrf2 phospho‐activation leading to the subsequent loss of expression of Nrf2 target genes. To determine whether Nrf2‐mediated activation of Antioxidant Response Elements (AREs) could rescue the observed dendritic pathology, we tested the effects of both Nrf2 overexpression and pharmaceutical modulation of Nrf2 activity on dendritic pathology. We found that Nrf2‐activation increased expression of detoxifying enzymes and reduced ROS levels in both A53T‐mutant and PFF exposed neurons, leading to a significant decrease in dendritic pathology.SignificanceThis investigation established that the Nrf2 transcriptional pathway is impaired by aberrant accumulation of α‐syn in both A53T‐mutant and PFF exposed neurons and determined that restoration of the anti‐oxidant pathway protects PD neurons from dendritic pathology.Support or Funding InformationFunding: This work was supported in part by the Parkinson Society of Canada (2014‐685 to SDR), the Natural Sciences and Engineering Research Council of Canada (RG060805 to SDR)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.