Dopamine Cytotoxicity Involves Both Oxidative and Nonoxidative Pathways in SH-SY5Y Cells: Potential Role of Alpha-Synuclein Overexpression and Proteasomal Inhibition in the Etiopathogenesis of Parkinson's Disease.

Kalpita Banerjee,Vishmadeb Pramanik,Soumyabrata Munshi,Tapasi Roy Mukherjee,Oishimaya Sen,Sasanka Chakrabarti

doi:10.1155/2014/878935

Abstract

Background. The cytotoxic effects of dopamine (DA) on several catecholaminergic cell lines involve DA oxidation products like reactive oxygen species (ROS) and toxic quinones and have implications in the pathogenesis of sporadic Parkinson's disease (PD). However, many molecular details are yet to be elucidated, and the possible nonoxidative mechanism of dopamine cytotoxicity has not been studied in great detail. Results. Cultured SH-SY5Y cells treated with DA (up to 400 μM) or lactacystin (5 μM) or DA (400 μM) plus N-acetylcysteine (NAC, 2.5 mM) for 24 h are processed accordingly to observe the cell viability, mitochondrial dysfunctions, oxidative stress parameters, proteasomal activity, expression of alpha-synuclein gene, and intracellular accumulation of the protein. DA causes mitochondrial dysfunction and extensive loss of cell viability partially inhibited by NAC, potent inhibition of proteasomal activity marginally prevented by NAC, and overexpression with accumulation of intracellular alpha-synuclein partially preventable by NAC. Under similar conditions of incubation, NAC completely prevents enhanced production of ROS and increased formation of quinoprotein adducts in DA-treated SH-SY5Y cells. Separately, proteasomal inhibitor lactacystin causes accumulation of alpha-synuclein as well as mitochondrial dysfunction and cell death. Conclusions. DA cytotoxicity includes both oxidative and nonoxidative modes and may involve overexpression and accumulation of alpha-synuclein as well as proteasomal inhibition.

Highlights

Parkinson’s disease (PD), which is a progressive neurodegenerative disorder affecting mainly the elderly people, appears in two major forms, familial and sporadic, and the latter variety accounts for nearly 90–95% of PD subjects
In some models various toxins like 6-hydroxydopamine (6-OHDA), rotenone, and 1-methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP) have been used to induce cell death, the cytotoxic action of dopamine (DA) on catecholaminergic cell lines is of special relevance in the context of PD pathogenesis because DA is endogenously available in the body [5, 6, 9, 10]
When SHSY5Y cells were exposed to DA, a dose-dependent loss of cell viability was noted as measured by trypan blue exclusion assay (Figure 1(a))

Summary

Introduction

Parkinson’s disease (PD), which is a progressive neurodegenerative disorder affecting mainly the elderly people, appears in two major forms, familial and sporadic, and the latter variety accounts for nearly 90–95% of PD subjects. A large body of evidence has already implicated that DA oxidation products like reactive oxygen species (ROS) and toxic quinones can trigger apoptotic death in cultured PC12 and SH-SY5Y cells in which mitochondrial dysfunction plays a critical role [11,12,13,14,15,16]. Most of these studies on DA cytotoxicity have suggested the oxidative mode of cellular damage, a few have indicated the existence of a nonoxidative pathway in this process [17, 18]. DA cytotoxicity includes both oxidative and nonoxidative modes and may involve overexpression and accumulation of alpha-synuclein as well as proteasomal inhibition

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Discussion

Conclusion