Cyanide-induced death of dopaminergic cells is mediated by uncoupling protein-2 up-regulation and reduced Bcl-2 expression

• Published in: Toxicology and applied pharmacology Vol. 238; no. 1; pp. 11 - 19
• Main Authors: Zhang, X., Li, L., Zhang, L., Borowitz, J.L., Isom, G.E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-07-2009; Elsevier
• Subjects: 60 APPLIED LIFE SCIENCES; Animals; APOPTOSIS; Bcl-2; Biological and medical sciences; Cell Death - drug effects; Cell Line, Transformed; Cyanide; CYANIDES; Cyanides - toxicity; DNA, Complementary; Dopamine - metabolism; Down-Regulation - drug effects; GENE REGULATION; GLUTATHIONE; Glutathione - drug effects; Glutathione - metabolism; HYDROGEN PEROXIDE; Hydrogen Peroxide - metabolism; Ion Channels - drug effects; Ion Channels - genetics; Medical sciences; Mesencephalon - cytology; METABOLISM; MITOCHONDRIA; Mitochondria - drug effects; Mitochondria - metabolism; Mitochondrial glutathione; Mitochondrial Proteins - drug effects; Mitochondrial Proteins - genetics; NERVE CELLS; OXIDATION; Oxidative Stress - drug effects; Proto-Oncogene Proteins c-bcl-2 - drug effects; Proto-Oncogene Proteins c-bcl-2 - genetics; Pyrimidines - pharmacology; Rats; RNA Interference; STRESSES; TOXICITY; Toxicology; Transfection; Uncoupling Protein 2; Up-Regulation - drug effects; Bcl-2; Cyanide; Uncoupling protein-2; Mitochondrial glutathione; Rat; Toxicity; Rodentia; Cyanides; Protein; Vertebrata; Mitochondria; Mammalia; Animal; C-Onc gene; Death; Mechanism of action; Protooncogene; Glutathione
• ISSN: 0041-008X; 1096-0333
• DOI: 10.1016/j.taap.2009.03.020

Cyanide is a potent inhibitor of mitochondrial oxidative metabolism and produces mitochondria-mediated death of dopaminergic neurons and sublethal intoxications that are associated with a Parkinson-like syndrome. Cyanide toxicity is enhanced when mitochondrial uncoupling is stimulated following up-regulation of uncoupling protein-2 (UCP-2). In this study, the role of a pro-survival protein, Bcl-2, in cyanide-mediated cell death was determined in a rat dopaminergic immortalized mesencephalic cell line (N27 cells). Following pharmacological up-regulation of UCP-2 by treatment with Wy14,643, cyanide reduced cellular Bcl-2 expression by increasing proteasomal degradation of the protein. The increased turnover of Bcl-2 was mediated by an increase of oxidative stress following UCP-2 up-regulation. The oxidative stress involved depletion of mitochondrial glutathione (mtGSH) and increased H
2O
2 generation. Repletion of mtGSH by loading cells with glutathione ethyl ester reduced H
2O
2 generation and in turn blocked the cyanide-induced decrease of Bcl-2. To determine if UCP-2 mediated the response, RNAi knock down was conducted. The RNAi decreased cyanide-induced depletion of mtGSH, reduced H
2O
2 accumulation, and inhibited down-regulation of Bcl-2, thus blocking cell death. To confirm the role of Bcl-2 down-regulation in the cell death, it was shown that over-expression of Bcl-2 by cDNA transfection attenuated the enhancement of cyanide toxicity after UCP-2 up-regulation. It was concluded that UCP-2 up-regulation sensitizes cells to cyanide by increasing cellular oxidative stress, leading to an increase of Bcl-2 degradation. Then the reduced Bcl-2 levels sensitize the cells to cyanide-mediated cell death.