Oxidation and cytotoxicity of 6-OHDA are mediated by reactive intermediates of COX-2 overexpressed in PC12 cells.
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(2)O(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.
Tyurina
Yulia Y
YY
Center for Free Radical and Antioxidant Health, Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA.
Kapralov
Alexander A
AA
Jiang
Jianfei
J
Borisenko
Grigory G
GG
Potapovich
Alla I
AI
Sorokin
Andrey
A
Kochanek
Patrick M
PM
Graham
Steven H
SH
Schor
Nina F
NF
Kagan
Valerian E
VE
D000818:Animals; D015153:Blotting, Western; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D006801:Humans; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology*; D016627:Oxidopamine / Q000378:metabolism* / Q000633:toxicity*; D016716:PC12 Cells; D051381:Rats
D016627:Oxidopamine; D051546:Cyclooxygenase 2