Proteasomal inhibition hypersensitizes differentiated neuroblastoma cells to oxidative damage

Parkinson's disease (PD) is a multifactorial disease caused by both genetic and environmental factors. Alpha-synuclein is of particular interest in PD since it is a major component of Lewy bodies and mutations in the alpha-synuclein gene were identified in familial PD. Oxidative stress and proteasomal dysfunction are implicated in the pathogenesis of PD but their interactions as well as their effect on aggregates formation are not yet clear. We therefore examined the roles of oxidative stress and proteasomal inhibition on protein aggregates induction in naïve and neuronally differentiated neuroblastoma SH-SY5Y cells. Neuroblastoma cells were stably transfected with wild type (WT) and A53T mutant alpha-synuclein. Naïve and transfected cells were exposed to oxidative stress induced by rotenone, SIN-I, FeCl(2,) and to proteasomal inhibition by lactacystin. Proteasomal inhibition caused a dose-dependent decrease in viability and induced protein aggregates formation containing alpha-synuclein and ubiquitin. Proteasomal inhibition induced significantly increased alpha-synuclein aggregation in cells expressing mutant alpha-synuclein. Exposure to reactive oxygen species (ROS) combined with proteasomal inhibition increased aggregates formation. Inclusion body formation and cell death of differentiated neuroblastoma cells overexpressing alpha-synuclein can serve as a valuable model for elucidating the molecular components that cause neurodegeneration in PD as well as evaluating pharmacological interventions.