Exp Neurobiol 2010; 19(3): 155-164
Published online December 1, 2010
© The Korean Society for Brain and Neural Sciences
Sung-Man Jeon1, Sang-Myung Cheon2*, Hye-Rahn Bae3, Jae Woo Kim2 and Seung U Kim4
1Department of Neurology, Bongseng Memorial Hospital, Busan 601-723, 2Department of Neurology, Dong-A University School of Medicine, Busan 602-715, 3Department of Physiology, Dong-A University School of Medicine, Busan 602-714, 4Institute for Regenerative Medicine, Gachon University Gil Hospital, Inchon 450-460, Korea
Correspondence to: *To whom correspondence should be addressed.
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Dysfunctions of ubiquitin-proteasome system and toxicity of dopamine have been known as the key mechanisms in the pathogenesis of Parkinson's disease (PD) and proteasome inhibitors are widely used in experimental models of PD to reproduce cell death of dopaminergic neurons. In the present study, immortalized human neural stem cells (HB1.F3, F3) and those transfected with human aromatic acid decarboxylase gene (F3.AADC), were used to investigate the mechanism of selective dopaminergic neuronal cell death mediated by dopamine or proteasome inhibitors. Flow cytometric analysis revealed that F3.AADC was more susceptible to dopamine than parental F3 cell which does not carry dopaminergic phenotype. The dopamine-induced apoptosis was mediated by activation of caspases 3 and 9 and cleavage of PARP. Proteasome inhibitors also induced apoptosis in dose-dependent manner but there was no difference between cell types. Prolonged exposure to subtoxic dose of proteasome inhibitors further enhanced dopamine-induced apoptosis in the F3.AADC, and increased presence of alpha-synuclein and ubiquitin-positive inclusions was noted in the cytoplasm of apoptotic cells by immunocytochemistry. These findings indicate that dopaminergic cells are selectively susceptible to dopamine toxicity and prolonged suppression of proteasome system further enhances selective sensitivity to dopamine toxicity. Chronic subtoxic proteasomal dysfunction of dopaminergic cells might contribute to selective cell death of dopaminergic neurons during the pathogenesis of Parkinson's disease.
Keywords: Parkinson's disease, proteasome, dopamine, apoptosis, human neural stem cells