Abstract
Uncoupling protein 2 (UCP-2) regulates mitochondrial function by increasing proton leak across the inner membrane to dissociate respiration from ATP synthesis and reduce reactive oxygen species generation. A number of studies have shown that UCP-2 expression protects cells from oxidative stress mediated injuries. In the current study, we show UCP-2-mediated reduction in mitochondrial function contributes to the mitochondrial dysfunction and the necrotic death of primary cultured mesencephalic cells (MCs) after exposure to cyanide, a complex IV inhibitor. The necrotic cell death was directly related to the level of mitochondrial dysfunction, as shown by reduction in ATP levels and decreased mitochondrial membrane potential. Treatment with cyanide for 6 h or longer upregulated UCP-2 expression. Blockade of up-regulation with a transcription or a translational inhibitor reduced the response to cyanide. Knockdown with RNAi or transfection with a UCP-2 dominant-negative interfering mutant reduced the cyanide-induced mitochondrial dysfunction and cell death, showing that constitutive expression of UCP-2 plays a role in the response to cyanide. Overexpression of UCP-2 by transfection with human full-length cDNA potentiated the cyanide toxicity. These findings indicate that UCP-2 can serve as a regulator of mitochondria-mediated necrotic cell death, in which enhanced expression can increase the vulnerability of primary MCs to injury due to complex IV-mediated inhibition by cyanide.
Footnotes
-
This work was supported by National Institutes of Health Grant ES04140.
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
-
doi:10.1124/jpet.105.088625.
-
ABBREVIATIONS: PD, Parkinson's disease; UCP, uncoupling protein; ROS, reactive oxygen species; ΔΨm, mitochondrial membrane potential; MC, mesencephalic cell; MPT, mitochondrial permeability transition; DMEM, Dulbecco's modified Eagle's medium; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; PBS, phosphate-buffered saline; PI, propidium iodide; PCR, polymerase chain reaction; R123, rhodamine 123; CsA, cyclosporin A; PAGE, polyacrylamide gel electrophoresis.
- Received April 26, 2005.
- Accepted June 2, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|