alpha-Synuclein Protects Against Manganese Neurotoxic Insult During the Early Stages of Exposure in a Dopaminergic Cell Model of Parkinson's Disease

作者：Harischandra Dilshan S; Jin Huajun; Anantharam Vellareddy; Kanthasamy Arthi; Kanthasamy Anumantha G

来源：Toxicological Sciences, 2015, 143(2): 454-468.

DOI：10.1093/toxsci/kfu247

• alpha-synuclein
• protein aggregation
• Parkinson's disease
• metals
• neuroprotection
• neurotoxicity

The pathological role of alpha-synuclein (alpha-Syn) aggregation in neurodegeneration is well recognized, but the physiological function of normal alpha-Syn remains unknown. As alpha-Syn protein contains multiple divalent metal binding sites, herein we conducted a comprehensive characterization of the role of alpha-Syn in manganese-induced dopaminergic neurotoxicity. We established transgenic N27 dopaminergic neuronal cells by stably expressing human wild-type alpha-Syn at normal physiological levels. alpha-Syn-expressing dopaminergic cells significantly attenuated Mn-induced neurotoxicity for 24-h exposures relative to vector control cells. To further explore cellular mechanisms, we studied the mitochondria-dependent apoptotic pathway. Analysis of a key mitochondrial apoptotic initiator, cytochrome c, revealed that alpha-Syn significantly reduces the Mn-induced cytochrome c release into cytosol. The downstream caspase cascade, involving caspase-9 and caspase-3 activation, during Mn exposure was also largely attenuated in Mn-treated alpha-Syn cells in a time-dependent manner. alpha-Syn cells also showed a dramatic reduction in the Mn-induced proteolytic activation of the pro-apoptotic kinase PKC delta. The generation of Mn-induced reactive oxygen species (ROS) did not differ between alpha-Syn and vector control cells, indicating that alpha-Syn exerts its protective effect independent of altering ROS generation. Inductively coupled plasma-mass spectrometry (ICP-MS) revealed no significant differences in intracellular Mn levels between treated vector and alpha-Syn cells. Notably, the expression of wild-type alpha-Syn in primary mesencephalic cells also rescued cells from Mn-induced neurotoxicity. However, prolonged exposure to Mn promoted protein aggregation in alpha-Syn-expressing cells. Collectively, these results demonstrate that wild-type alpha-Syn exhibits neuroprotective effects against Mn-induced neurotoxicity during the early stages of exposure in a dopaminergic neuronal model of PD.

• 出版日期2015-2