Oxidation and cytotoxicity of 6-OHDA are mediated by reactive intermediates of COX-2 overexpressed in PC12 cells

• Published in: Brain research 2006-06, Vol.1093 (1), p.71-82
• Main Authors: Tyurina, Yulia Y., Kapralov, Alexander A., Jiang, Jianfei, Borisenko, Grigory G., Potapovich, Alla I., Sorokin, Andrey, Kochanek, Patrick M., Graham, Steven H., Schor, Nina F., Kagan, Valerian E.
• Format: Article
• Language: English
• Subjects: 6-OHDA oxidation; Animals; Biological and medical sciences; Blotting, Western; Cyclooxygenase 2 - metabolism; Cyclooxygenase-2; Cytotoxicity; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Humans; Medical sciences; Neurology; Oxidation-Reduction; Oxidative Stress - physiology; Oxidopamine - metabolism; Oxidopamine - toxicity; PC12 Cells; Peroxidase activity; Rats; Superoxide
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2005.10.105

Parkinson's disease is characterized by a progressive loss of dopaminergic neurons, likely associated with dysregulation of oxidation of catechols, such as dopamine (DA) and 6-hydroxydopamine (6-OHDA), and resulting in oxidative stress. The involvement of cyclooxygenase-2 (COX-2) in pathogenesis of Parkinson's disease has been suggested. However, specific COX-2 triggered mechanisms participating in catalysis of DA oxidation and enhanced catechol-induced cytotoxicity remain poorly characterized. Here, we demonstrate that in a model biochemical system, recombinant heme-reconstituted COX-2 induced oxidation of 6-OHDA in the course of its peroxidase (H 2O 2-dependent) and cyclooxygenase (arachidonic acid (AA)-dependent) catalytic half-cycles. Similarly, COX-2 was able to stimulate 6-OHDA oxidation during its peroxidase- and cyclooxygenase half-cycles and caused oxidative stress in homogenates of PC12 cells stably overexpressing the enzyme (but not in mock-transfected cells). In addition, the increased levels of COX-2 were associated with enhanced cytotoxicity of 6-OHDA in stably transfected PC12 cells. Finally, co-oxidation of 6-OHDA by COX-2 triggered production of superoxide radicals critical for both propagation of 6-OHDA oxidation and induction of oxidative stress in COX-2 overexpressing cells. Thus, we conclude that both peroxidase and cyclooxygenase half-cycles of COX-2-catalyzed reactions are essential for COX-2-dependent activation of 6-OHDA oxidation, oxygen radical production, oxidative stress, and cytotoxicity.