Glutathione depletion resulting in selective mitochondrial complex I inhibition in dopaminergic cells is via an NO-mediated pathway not involving peroxynitrite: implications for Parkinson's disease.
An early biochemical change in the Parkinsonian substantia nigra (SN) is reduction in total glutathione (GSH + GSSG) levels in affected dopaminergic neurons prior to depletion in mitochondrial complex I activity, dopamine loss, and cell death. We have demonstrated using dopaminergic PC12 cell lines genetically engineered to inducibly down-regulate glutathione synthesis that total glutathione depletion in these cells results in selective complex I inhibition via a reversible thiol oxidation event. Here, we demonstrate that inhibition of complex I may occur either by direct nitric oxide (NO) but not peroxinitrite-mediated inhibition of complex I or through H2O2-mediated inhibition of the tricarboxylic acid (TCA) cycle enzyme alpha-ketoglutarate dehydrogenase (KGDH) which supplies NADH as substrate to the complex; activity of both enzymes are reduced in PD. While glutathione depletion causes a reduction in spare KGDH enzymatic capacity, it produces a complete collapse of complex I reserves and significant effects on mitochondrial function. Our data suggest that NO is likely the primary agent involved in preferential complex I inhibition following acute glutathione depletion in dopaminergic cells. This may have major implications in terms of understanding mechanisms of dopamine cell death associated with PD especially as they relate to complex I inhibition.
Hsu
Michael
M
Department of Molecular Biology, University of Southern California, Los Angeles, California, USA.
Srinivas
Bharath
B
Kumar
Jyothi
J
Subramanian
Rajagopalan
R
Andersen
Julie
J
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D002454:Cell Differentiation / Q000187:drug effects; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000494:pharmacology; D042967:Electron Transport Complex I / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D016716:PC12 Cells / Q000187:drug effects; D010300:Parkinson Disease / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology
D000447:Aldehydes; D000900:Anti-Bacterial Agents; D009097:Multienzyme Complexes; D009569:Nitric Oxide; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D007655:Ketoglutarate Dehydrogenase Complex; D002950:Citrate (si)-Synthase; D042967:Electron Transport Complex I; D005978:Glutathione; C027576:4-hydroxy-2-nonenal; D004318:Doxycycline; D010100:Oxygen; D004298:Dopamine