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Selenomethionine Prevents Degeneration Induced by Overexpression of Wild-Type Human -Synuclein during Differentiation of Neuroblastoma Cells

Center for Vitamins and Cancer Research, Department of Radiology, School of Medicine, University of Colorado Health Sciences Center, Denver, CO 80262

Address reprint requests to: Kedar N. Prasad, Ph.D., Premier Micronutrient Corp., Antioxidant Res. Inst., 14 Galli Drive, Suite 200, Novato, CA 94949. E-mail: kprasad{at}premiermicronutrient.com

Objective: High levels of wild-type -synuclein are found in autopsied brain samples of idiopathic Parkinson’s disease (PD), some familial PD, some Alzheimer’s disease (AD) and Down’s syndrome with dementia. Therefore, we have investigated whether overexpression of wild-type -synuclein causes degeneration during adenosine, 3',5'-cyclic monophosphate (cAMP)-induced differentiation of murine neuroblastoma (NB) cells in culture. We have also studied whether selenomethionine can modify the effect of overexpression of -synuclein during differentiation of NB cells.

Methods: To study these issues, we established a murine neuroblastoma (NB) clone (NBP2-PN54-C20) that expressed high levels of wild-type human -synuclein as determined by real time PCR and Western blot. We have utilized RO20-1724, an inhibitor of cyclic nucleotide phosphodiesterase, and prostaglandin A₁ (PGA₁), a stimulator of adenylate cyclase, or RO20-1724 and dibutyryl cAMP to induce terminal differentiation in over 95% of the cell population by elevating the intracellular levels of cAMP in NB cells. The viability of cells was determined by MTT assay and LDH leakage assay, and the degeneration was documented by photomicrographs.

Results: The results showed that overexpression of human wild-type -synuclein decreased viability and increased degenerative changes in comparison to those observed in vector control cells, when differentiation was induced by treatment with RO20-1724 and PGA₁, but not with RO20-1724 and dibutyryl cAMP. When selenomethionine was added to NB cells overexpressing -synuclein immediately after the addition of RO20-1724 and PGA₁, the viability and degenerative changes were markedly reduced, suggesting the involvement of increased oxidative stress in the mechanism of action of -synuclein. This protective effect was not observed after treatment with sodium selenite or methionine.

Conclusions: Data suggested that Overexpression of wild-type human -synuclein-decreased viability and increased the levels of degenerative changes during differentiation of NB cells were reduced by selenomethionine treatment. This suggest that one of mechanisms of action -synuclein may involve increased oxidative stress.

Key words: human wild-type -synuclein, differentiated neuroblastoma cells, prevention, degeneration, selenomethionine

Abbreviations: NB = neuroblastoma cells • cAMP = adenosine 3',5'-cyclic monophosphate • PGA₁ = prostaglandin A₁ • RO20-1724 = 4-3-butoxy-4-methoxybenzyl-2-imidazolidinone • AD = Alzheimer’s disease • PD = Parkinson’s disease