Mechanism of toxicity in rotenone models of Parkinson's disease.
Exposure of rats to the pesticide and complex I inhibitor rotenone reproduces features of Parkinson's disease, including selective nigrostriatal dopaminergic degeneration and alpha-synuclein-positive cytoplasmic inclusions (Betarbet et al., 2000; Sherer et al., 2003). Here, we examined mechanisms of rotenone toxicity using three model systems. In SK-N-MC human neuroblastoma cells, rotenone (10 nm to 1 microm) caused dose-dependent ATP depletion, oxidative damage, and death. To determine the molecular site of action of rotenone, cells were transfected with the rotenone-insensitive single-subunit NADH dehydrogenase of Saccharomyces cerevisiae (NDI1), which incorporates into the mammalian ETC and acts as a "replacement" for endogenous complex I. In response to rotenone, NDI1-transfected cells did not show mitochondrial impairment, oxidative damage, or death, demonstrating that these effects of rotenone were caused by specific interactions at complex I. Although rotenone caused modest ATP depletion, equivalent ATP loss induced by 2-deoxyglucose was without toxicity, arguing that bioenergetic defects were not responsible for cell death. In contrast, reducing oxidative damage with antioxidants, or by NDI1 transfection, blocked cell death. To determine the relevance of rotenone-induced oxidative damage to dopaminergic neuronal death, we used a chronic midbrain slice culture model. In this system, rotenone caused oxidative damage and dopaminergic neuronal loss, effects blocked by alpha-tocopherol. Finally, brains from rotenone-treated animals demonstrated oxidative damage, most notably in midbrain and olfactory bulb, dopaminergic regions affected by Parkinson's disease. These results, using three models of increasing complexity, demonstrate the involvement of oxidative damage in rotenone toxicity and support the evaluation of antioxidant therapies for Parkinson's disease.
Sherer
Todd B
TB
Center for Neurodegenerative Disease, Emory University, Atlanta, Georgia 30322, USA. tsherer@emory.edu
Betarbet
Ranjita
R
Testa
Claudia M
CM
Seo
Byoung Boo
BB
Richardson
Jason R
JR
Kim
Jin Ho
JH
Miller
Gary W
GW
Yagi
Takao
T
Matsuno-Yagi
Akemi
A
Greenamyre
J Timothy
JT
D000255:Adenosine Triphosphate / Q000172:deficiency / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004195:Disease Models, Animal; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000633:toxicity; D006801:Humans; D066298:In Vitro Techniques; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology; D009830:Olfactory Bulb / Q000187:drug effects / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects; D020734:Parkinsonian Disorders / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D011917:Rats, Inbred Lew; D012402:Rotenone / Q000633:toxicity*; D013995:Time
D000975:Antioxidants; D004791:Enzyme Inhibitors; D018696:Neuroprotective Agents; D012402:Rotenone; D000255:Adenosine Triphosphate; D042967:Electron Transport Complex I; D004298:Dopamine