Dopamine as a Potent Inducer of Cellular Glutathione and NAD(P)H:Quinone Oxidoreductase 1 in PC12 Neuronal Cells: A Potential Adaptive Mechanism for Dopaminergic Neuroprotection

Abstract

Dopamine auto-oxidation and the consequent formation of reactive oxygen species and electrophilic quinone molecules have been implicated in dopaminergic neuronal cell death in Parkinson's disease. We reported here that in PC12 dopaminergic neuronal cells dopamine at noncytotoxic concentrations (50-150 muM) potently induced cellular glutathione (GSH) and the phase 2 enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1), two critical cellular defenses in detoxification of ROS and electrophilic quinone molecules. Incubation of PC12 cells with dopamine also led to a marked increase in the mRNA levels for gamma-glutamylcysteine ligase catalytic subunit (GCLC) and NQO1. In addition, treatment of PC12 cells with dopamine resulted in a significant elevation of GSH content in the mitochondrial compartment. To determine whether treatment with dopamine at noncytotoxic concentrations, which upregulated the cellular defenses could protect the neuronal cells against subsequent lethal oxidative and electrophilic injury, PC12 cells were pretreated with dopamine (150 muM) for 24 h and then exposed to various cytotoxic concentrations of dopamine or 6-hydroxydopamine (6-OHDA). We found that pretreatment of PC12 cells with dopamine at a noncytotoxic concentration led to a remarkable protection against cytotoxicity caused by dopamine or 6-OHDA at lethal concentrations, as detected by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium reduction assay. In view of the critical roles of GSH and NQO1 in protecting against dopaminergic neuron degeneration, the above findings implicate that upregulation of both GSH and NQO1 by dopamine at noncytotoxic concentrations may serve as an important adaptive mechanism for dopaminergic neuroprotection.

Genistein inhibits TNF-α-induced endothelial inflammation through the protein kinase pathway A and improves vascular inflammation in C57BL/6 mice

“…The protein concentrations were measured using a Bio-Rad protein assay kit with bovine serum albumin (BSA) as the standard. The measurements of the cellular superoxide dismutase (SOD), glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione transferase (GST), NAD(P)H:quinone oxidoreductase 1 (NQO-1) and catalase (CAT) were performed according to previously described methods [29, 30]. …”

NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1), a multifunctional antioxidant enzyme and exceptionally versatile cytoprotector

“…In addition, overexpression of NQO1 protected SK-N-MC human neuroblastoma cells against the cytotoxicity of dopamine, whereas superoxide dismutase and catalase were ineffective [74]. Prior treatment of PC12 neuronal cells with dopamine increased NQO1 and glutathione levels and protected against cell death caused by toxic concentrations of dopamine or 6-hydroxydopamine [75]. Similarly, induction of NQO1 and GSH by dimethyl fumarate, 3 H -1,2-dithiole-3-thione or tert -butylhydroquinone (tBHQ) protected against neurocytotoxicity caused by dopamine, 6-hydroxydopamine, 4-hydroxy-2-nonenal, or H 2 O 2 [76–80].…”

Mitochondrial Thiols in the Regulation of Cell Death Pathways

“…The chemoprotectant 3H-1,2-dithiole-3-thione protected against oxidative and electrophilic neurotoxicity in neuroblastoma cells and primary neurons due to its ability to increase mitochondrial GSH (76). Interestingly, dopamine at nontoxic concentrations strongly increased mitochondrial GSH and afforded a greater protection against cytotoxicity (75). GSH was substantially decreased in cerebral cortex and striatum mitochondria in a model of brain focal ischemia, in which the loss in mitochondrial GSH did not correlate with minimal total GSH losses in the tissue (4).…”