N-acetylcysteine amide ameliorates mitochondrial dysfunction and reduces oxidative stress in hiPSC-derived dopaminergic neurons with POLG mutation

Exp Neurol. 2021 Mar;337:113536. doi: 10.1016/j.expneurol.2020.113536. Epub 2020 Nov 29.


The inability to reliably replicate mitochondrial DNA (mtDNA) by mitochondrial DNA polymerase gamma (POLG) leads to a subset of common mitochondrial diseases associated with neuronal death and depletion of neuronal mtDNA. Defining disease mechanisms in neurons remains difficult due to the limited access to human tissue. Using human induced pluripotent stem cells (hiPSCs), we generated functional dopaminergic (DA) neurons showing positive expression of dopaminergic markers TH and DAT, mature neuronal marker MAP2 and functional synaptic markers synaptophysin and PSD-95. These DA neurons were electrophysiologically characterized, and exhibited inward Na + currents, overshooting action potentials and spontaneous postsynaptic currents (sPSCs). POLG patient-specific DA neurons (POLG-DA neurons) manifested a phenotype that replicated the molecular and biochemical changes found in patient post-mortem brain samples namely loss of complex I and depletion of mtDNA. Compared to disease-free hiPSC-derived DA neurons, POLG-DA neurons exhibited loss of mitochondrial membrane potential, loss of complex I and loss of mtDNA and TFAM expression. POLG driven mitochondrial dysfunction also led to neuronal ROS overproduction and increased cellular senescence. This deficit was selectively rescued by treatment with N-acetylcysteine amide (NACA). In conclusion, our study illustrates the promise of hiPSC technology for assessing pathogenetic mechanisms associated with POLG disease, and that NACA can be a promising potential therapy for mitochondrial diseases such as those caused by POLG mutation.

Keywords: DA neurons; Mitochondria; N-acetylcysteine amide; POLG; hiPSCs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcysteine / analogs & derivatives*
  • Acetylcysteine / therapeutic use
  • Action Potentials
  • Antioxidants / therapeutic use*
  • Cellular Senescence / genetics
  • DNA Polymerase gamma / genetics*
  • DNA, Mitochondrial / genetics
  • Dopaminergic Neurons / drug effects*
  • Electron Transport Complex I / metabolism
  • Excitatory Postsynaptic Potentials
  • Humans
  • Induced Pluripotent Stem Cells / drug effects*
  • Membrane Potential, Mitochondrial / drug effects
  • Mitochondrial Diseases / drug therapy*
  • Oxidative Stress / drug effects*
  • Sodium Channels / metabolism


  • Antioxidants
  • DNA, Mitochondrial
  • Sodium Channels
  • N-Acetylcysteinamide
  • DNA Polymerase gamma
  • POLG protein, human
  • Electron Transport Complex I
  • Acetylcysteine