title: Uncoupling protein-2 up-regulation and enhanced cyanide toxicity are mediated by PPARalpha activation and oxidative stress.
abstract: Uncoupling protein 2 (UCP-2) is an inner mitochondrial membrane proton carrier that modulates mitochondrial membrane potential (DeltaPsi(m)) and uncouples oxidative phosphorylation. We have shown that up-regulation of UCP-2 by Wy14,643, a selective peroxisome proliferator-activated receptor-alpha (PPARalpha) agonist, enhances cyanide cytotoxicity. The pathway by which Wy14,643 up-regulates UCP-2 was determined in a dopaminergic cell line (N27 cells). Since dopaminergic mesencephalic cells are a primary brain target of cyanide, the N27 immortalized mesencephalic cell was used in this study. Wy14,643 produced a concentration- and time-dependent up-regulation of UCP-2 that was linked to enhanced cyanide-induced cell death. MK886 (PPARalpha antagonist) or PPARalpha knock-down by RNA interference (RNAi) inhibited PPARalpha activity as shown by the peroxisome proliferator response element-luciferase reporter assay, but only partially decreased up-regulation of UCP-2. The role of oxidative stress as an alternative pathway to UCP-2 up-regulation was determined. Wy14,643 induced a rapid surge of ROS generation and loading cells with glutathione ethyl ester (GSH-EE) or pre-treatment with vitamin E attenuated up-regulation of UCP-2. On the other hand, RNAi knockdown of PPARalpha did not alter ROS generation, suggesting a PPARalpha-independent component to the response. Co-treatment with PPARalpha-RNAi and GSH-EE blocked both the up-regulation of UCP-2 by Wy14,643 and the cyanide-induced cell death. It was concluded that a PPARalpha-mediated pathway and an oxidative stress pathway independent of PPARalpha mediate the up-regulation of UCP-2 and subsequent increased vulnerability to cyanide-induced cytotoxicity.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907-1333, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: L
authors.initials: L
authors.lastname: Li
authors.forename: K
authors.initials: K
authors.lastname: Prabhakaran
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: H B
authors.initials: HB
authors.lastname: Leavesley
authors.forename: J L
authors.initials: JL
authors.lastname: Borowitz
authors.forename: G E
authors.initials: GE
authors.lastname: Isom
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000633:toxicity*; D020868:Gene Silencing; D005978:Glutathione / Q000031:analogs & derivatives / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress; D047493:PPAR alpha / Q000819:agonists / Q000378:metabolism*; D011190:Potassium Cyanide / Q000633:toxicity*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D000071246:Uncoupling Protein 2; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D014810:Vitamin E / Q000494:pharmacology; D002722:Chlorobenzenes
chemical_list: D004338:Drug Combinations; D004791:Enzyme Inhibitors; D005978:Glutathione; D007211:Indoles; D007473:Ion Channels; D024101:Mitochondrial Proteins; D047493:PPAR alpha; D011190:Potassium Cyanide; D011743:Pyrimidines; D017382:Reactive Oxygen Species; D000071246:Uncoupling Protein 2; D014810:Vitamin E; C000604391:Ucp2 protein, rat; C060893:MK-886; D002722:Chlorobenzenes; C042431:S-ethyl glutathione; C006253:pirinixic acid