title: Thioredoxin reductase deficiency potentiates oxidative stress, mitochondrial dysfunction and cell death in dopaminergic cells.
abstract: Mitochondria are considered major generators of cellular reactive oxygen species (ROS) which are implicated in the pathogenesis of neurodegenerative diseases such as Parkinson's disease (PD). We have recently shown that isolated mitochondria consume hydrogen peroxide (H₂O₂) in a substrate- and respiration-dependent manner predominantly via the thioredoxin/peroxiredoxin (Trx/Prx) system. The goal of this study was to determine the role of Trx/Prx system in dopaminergic cell death. We asked if pharmacological and lentiviral inhibition of the Trx/Prx system sensitized dopaminergic cells to mitochondrial dysfunction, increased steady-state H₂O₂ levels and death in response to toxicants implicated in PD. Incubation of N27 dopaminergic cells or primary rat mesencephalic cultures with the Trx reductase (TrxR) inhibitor auranofin in the presence of sub-toxic concentrations of parkinsonian toxicants paraquat; PQ or 6-hydroxydopamine; 6OHDA (for N27 cells) resulted in a synergistic increase in H₂O₂ levels and subsequent cell death. shRNA targeting the mitochondrial thioredoxin reductase (TrxR2) in N27 cells confirmed the effects of pharmacological inhibition. A synergistic decrease in maximal and reserve respiratory capacity was observed in auranofin treated cells and TrxR2 deficient cells following incubation with PQ or 6OHDA. Additionally, TrxR2 deficient cells showed decreased basal mitochondrial oxygen consumption rates. These data demonstrate that inhibition of the mitochondrial Trx/Prx system sensitizes dopaminergic cells to mitochondrial dysfunction, increased steady-state H₂O₂, and cell death. Therefore, in addition to their role in the production of cellular H₂O₂ the mitochondrial Trx/Prx system serve as a major sink for cellular H₂O₂ and its disruption may contribute to dopaminergic pathology associated with PD.
authors.affiliation: Neuroscience Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.
authors.forename: Pamela
authors.initials: P
authors.lastname: Lopert
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Day
authors.forename: Manisha
authors.initials: M
authors.lastname: Patel
mesh_terms: D000818:Animals; D001310:Auranofin / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D019069:Cell Respiration / Q000187:drug effects / Q000235:genetics; D059290:Dopaminergic Neurons / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D004357:Drug Synergism; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D006861:Hydrogen Peroxide / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics; D008636:Mesencephalon / Q000166:cytology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology*; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D016627:Oxidopamine / Q000494:pharmacology; D010269:Paraquat / Q000494:pharmacology; D054464:Peroxiredoxins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D054482:Thioredoxin Reductase 2 / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D001310:Auranofin; D016627:Oxidopamine; D006861:Hydrogen Peroxide; D054464:Peroxiredoxins; D054482:Thioredoxin Reductase 2; D010269:Paraquat